1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718 2719 2720 2721 2722 2723 2724 2725 2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769 2770 2771 2772 2773 2774 2775 2776 2777 2778 2779 2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906 2907 2908 2909 2910 2911 2912 2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969 2970 2971 2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011 3012 3013 3014 3015 3016 3017 3018 3019 3020 3021 3022 3023 3024 3025 3026 3027 3028 3029 3030 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050 3051 3052 3053 3054 3055 3056 3057 3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082 3083 3084 3085 3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096 3097 3098 3099 3100 3101 3102 3103 3104 3105 3106 3107 3108 3109 3110 3111 3112 3113 3114 3115 3116 3117 3118 3119 3120 3121 3122 3123 3124 3125 3126 3127 3128 3129 3130 3131 3132 3133 3134 3135 3136 3137 3138 3139 3140 3141 3142 3143 3144 3145 3146 3147 3148 3149 3150 3151 3152 3153 3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253 3254 3255 3256 3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282 3283 3284 3285 3286 3287 3288 3289 3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302 3303 3304 3305 3306 3307 3308 3309 3310 3311 3312 3313 3314 3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326 3327 3328 3329 3330 3331 3332 3333 3334 3335 3336 3337 3338 3339 3340 3341 3342 3343 3344 3345 3346 3347 3348 3349 3350 3351 3352 3353 3354 3355 3356 3357 3358 3359 3360 3361 3362 3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375 3376 3377 3378 3379 3380 3381 3382 3383 3384 3385 3386 3387 3388 3389 3390 3391 3392 3393 3394 3395 3396 3397 3398 3399 3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411 3412 3413 3414 3415 3416 3417 3418 3419 3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430 3431 3432 3433 3434 3435 3436 3437 3438 3439 3440 3441 3442 3443 3444 3445 3446 3447 3448 3449 3450 3451 3452 3453 3454 3455 3456 3457 3458 3459 3460 3461 3462 3463 3464 3465 3466 3467 3468 3469 3470 3471 3472 3473 3474 3475 3476 3477 3478 3479 3480 3481 3482 3483 3484 3485 3486 3487 3488 3489 3490 3491 3492 3493 3494 3495 3496 3497 3498 3499 3500 3501 3502 3503 3504 3505 3506 3507 3508 3509 3510 3511 3512 3513 3514 3515 3516 3517 3518 3519 3520 3521 3522 3523 3524 3525 3526 3527 3528 3529 3530 3531 3532 3533 3534 3535 3536 3537 3538 3539 3540 3541 3542 3543 3544 3545 3546 3547 3548 3549 3550 3551 3552 3553 3554 3555 3556 3557 3558 3559 3560 3561 3562 3563 3564 3565 3566 3567 3568 3569 3570 3571 3572 3573 3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 3590 3591 3592 3593 3594 3595 3596 3597 3598 3599 3600 3601 3602 3603 3604 3605 3606 3607 3608 3609 3610 3611 3612 3613 3614 3615 3616 3617 3618 3619 3620 3621 3622 3623 3624 3625 3626 3627 3628 3629 3630 3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647 3648 3649 3650 3651 3652 3653 3654 3655 3656 3657 3658 3659 3660 3661 3662 3663 3664 3665 3666 3667 3668 3669 3670 3671 3672 3673 3674 3675 3676 3677 3678 3679 3680 3681 3682 3683 3684 3685 3686 3687 3688 3689 3690 3691 3692 3693 3694 3695 3696 3697 3698 3699 3700 3701 3702 3703 3704 3705 3706 3707 3708 3709 3710 3711 3712 3713 3714 3715 3716 3717 3718 3719 3720 3721 3722 3723 3724 3725 3726 3727 3728 3729 3730 3731 3732 3733 3734 3735 3736 3737 3738 3739 3740 3741 3742 3743 3744 3745 3746 3747 3748 3749 3750 3751 3752 3753 3754 3755 3756 3757 3758 3759 3760 3761 3762 3763 3764 3765 3766 3767 3768 3769 3770 3771 3772 3773 3774 3775 3776 3777 3778 3779 3780 3781 3782 3783 3784 3785 3786 3787 3788 3789 3790 3791 3792 3793 3794 3795 3796 3797 3798 3799 3800 3801 3802 3803 3804 3805 3806 3807 3808 3809 3810 3811 3812 3813 3814 3815 3816 3817 3818 3819 3820 3821 3822 3823 3824 3825 3826 3827 3828 3829 3830 3831 3832 3833 3834 3835 3836 3837 3838 3839 3840 3841 3842 3843 3844 3845 3846 3847 3848 3849 3850 3851 3852 3853 3854 3855 3856 3857 3858 3859 3860 3861 3862 3863 3864 3865 3866 3867 3868 3869 3870 3871 3872 3873 3874 3875 3876 3877 3878 3879 3880 3881 3882 3883 3884 3885 3886 3887 3888 3889 3890 3891 3892 3893 3894 3895 3896 3897 3898 3899 3900 3901 3902 3903 3904 3905 3906 3907 3908 3909 3910 3911 3912 3913 3914 3915 3916 3917 3918 3919 3920 3921 3922 3923 3924 3925 3926 3927 3928 3929 3930 3931 3932 3933 3934 3935 3936 3937 3938 3939 3940 3941 3942 3943 3944 3945 3946 3947 3948 3949 3950 3951 3952 3953 3954 3955 3956 3957 3958 3959 3960 3961 3962 3963 3964 3965 3966 3967 3968 3969 3970 3971 3972 3973 3974 3975 3976 3977 3978 3979 3980 3981 3982 3983 3984 3985 3986 3987 3988 3989 3990 3991 3992 3993 3994 3995 3996 3997 3998 3999 4000 4001 4002 4003 4004 4005 4006 4007 4008 4009 4010 4011 4012 4013 4014 4015 4016 4017 4018 4019 4020 4021 4022 4023 4024 4025 4026 4027 4028 4029 4030 4031 4032 4033 4034 4035 4036 4037 4038 4039 4040 4041 4042 4043 4044 4045 4046 4047 4048 4049 4050 4051 4052 4053 4054 4055 4056 4057 4058 4059 4060 4061 4062 4063 4064 4065 4066 4067 4068 4069 4070 4071 4072 4073 4074 4075 4076 4077 4078 4079 4080 4081 4082 4083 4084 4085 4086 4087 4088 4089 4090 4091 4092 4093 4094 4095 4096 4097 4098 4099 4100 4101 4102 4103 4104 4105 4106 4107 4108 4109 4110 4111 4112 4113 4114 4115 4116 4117 4118 4119 4120 4121 4122 4123 4124 4125 4126 4127 4128 4129 4130 4131 4132 4133 4134 4135 4136 4137 4138 4139 4140 4141 4142 4143 4144 4145 4146 4147 4148 4149 4150 4151 4152 4153 4154 4155 4156 4157 4158 4159 4160 4161 4162 4163 4164 4165 4166 4167 4168 4169 4170 4171 4172 4173 4174 4175 4176 4177 4178 4179 4180 4181 4182 4183 4184 4185 4186 4187 4188 4189 4190 4191 4192 4193 4194 4195 4196 4197 4198 4199 4200 4201 4202 4203 4204 4205 4206 4207 4208 4209 4210 4211 4212 4213 4214 4215 4216 4217 4218 4219 4220 4221 4222 4223 4224 4225 4226 4227 4228 4229 4230 4231 4232 4233 4234 4235 4236 4237 4238 4239 4240 4241 4242 4243 4244 4245 4246 4247 4248 4249 4250 4251 4252 4253 4254 4255 4256 4257 4258 4259 4260 4261 4262 4263 4264 4265 4266 4267 4268 4269 4270 4271 4272 4273 4274 4275 4276 4277 4278 4279 4280 4281 4282 4283 4284 4285 4286 4287 4288 4289 4290 4291 4292 4293 4294 4295 4296 4297 4298 4299 4300 4301 4302 4303 4304 4305 4306 4307 4308 4309 4310 4311 4312 4313 4314 4315 4316 4317 4318 4319 4320 4321 4322 4323 4324 4325 4326 4327 4328 4329 4330 4331 4332 4333 4334 4335 4336 4337 4338 4339 4340 4341 4342 4343 4344 4345 4346 4347 4348 4349 4350 4351 4352 4353 4354 4355 4356 4357 4358 4359 4360 4361 4362 4363 4364 4365 4366 4367 4368 4369 4370 4371 4372 4373 4374 4375 4376 4377 4378 4379 4380 4381 4382 4383 4384 4385 4386 4387 4388 4389 4390 4391 4392 4393 4394 4395 4396 4397 4398 4399 4400 4401 4402 4403 4404 4405 4406 4407 4408 4409 4410 4411 4412 4413 4414 4415 4416 4417 4418 4419 4420 4421 4422 4423 4424 4425 4426 4427 4428 4429 4430 4431 4432 4433 4434 4435 4436 4437 4438 4439 4440 4441 4442 4443 4444 4445 4446 4447 4448 4449 4450 4451 4452 4453 4454 4455 4456 4457 4458 4459 4460 4461 4462 4463 4464 4465 4466 4467 4468 4469 4470 4471 4472 4473 4474 4475 4476 4477 4478 4479 4480 4481 4482 4483 4484 4485 4486 4487 4488 4489 4490 4491 4492 4493 4494 4495 4496 4497 4498 4499 4500 4501 4502 4503 4504 4505 4506 4507 4508 4509 4510 4511 4512 4513 4514 4515 4516 4517 4518 4519 4520 4521 4522 4523 4524 4525 4526 4527 4528 4529 4530 4531 4532 4533 4534 4535 4536 4537 4538 4539 4540 4541 4542 4543 4544 4545 4546 4547 4548 4549 4550 4551 4552 4553 4554 4555 4556 4557 4558 4559 4560 4561 4562 4563 4564 4565 4566 4567 4568 4569 4570 4571 4572 4573 4574 4575 4576 4577 4578 4579 4580 4581 4582 4583 4584 4585 4586 4587 4588 4589 4590 4591 4592 4593 4594 4595 4596 4597 4598 4599 4600 4601 4602 4603 4604 4605 4606 4607 4608 4609 4610 4611 4612 4613 4614 4615 4616 4617 4618 4619 4620 4621 4622 4623 4624 4625 4626 4627 4628 4629 4630 4631 4632 4633 4634 4635 4636 4637 4638 4639 4640 4641 4642 4643 4644 4645 4646 4647 4648 4649 4650 4651 4652 4653 4654 4655 4656 4657 4658 4659 4660 4661 4662 4663 4664 4665 4666 4667 4668 4669 4670 4671 4672 4673 4674 4675 4676 4677 4678 4679 4680 4681 4682 4683 4684 4685 4686 4687 4688 4689 4690 4691 4692 4693 4694 4695 4696 4697 4698 4699 4700 4701 4702 4703 4704 4705 4706 4707 4708 4709 4710 4711 4712 4713 4714 4715 4716 4717 4718 4719 4720 4721 4722 4723 4724 4725 4726 4727 4728 4729 4730 4731 4732 4733 4734 4735 4736 4737 4738 4739 4740 4741 4742 4743 4744 4745 4746 4747 4748 4749 4750 4751 4752 4753 4754 4755 4756 4757 4758 4759 4760 4761 4762 4763 4764 4765 4766 4767 4768 4769 4770 4771 4772 4773 4774 4775 4776 4777 4778 4779 4780 4781 4782 4783 4784 4785 4786 4787 4788 4789 4790 4791 4792 4793 4794 4795 4796 4797 4798 4799 4800 4801 4802 4803 4804 4805 4806 4807 4808 4809 4810 4811 4812 4813 4814 4815 4816 4817 4818 4819 4820 4821 4822 4823 4824 4825 4826 4827 4828 4829 4830 4831 4832 4833 4834 4835 4836 4837 4838 4839 4840 4841 4842 4843 4844 4845 4846 4847 4848 4849 4850 4851 4852 4853 4854 4855 4856 4857 4858 4859 4860 4861 4862 4863 4864 4865 4866 4867 4868 4869 4870 4871 4872 4873 4874 4875 4876 4877 4878 4879 4880 4881 4882 4883 4884 4885 4886 4887 4888 4889 4890 4891 4892 4893 4894 4895 4896 4897 4898 4899 4900 4901 4902 4903 4904 4905 4906 4907 4908 4909 4910 4911 4912 4913 4914 4915 4916 4917 4918 4919 4920 4921 4922 4923 4924 4925 4926 4927 4928 4929 4930 4931 4932 4933 4934 4935 4936 4937 4938 4939 4940 4941 4942 4943 4944 4945 4946 4947 4948 4949 4950 4951 4952 4953 4954 4955 4956 4957 4958 4959 4960 4961 4962 4963 4964 4965 4966 4967 4968 4969 4970 4971 4972 4973 4974 4975 4976 4977 4978 4979 4980 4981 4982 4983 4984 4985 4986 4987 4988 4989 4990 4991 4992 4993 4994 4995 4996 4997 4998 4999 5000 5001 5002 5003 5004 5005 5006 5007 5008 5009 5010 5011 5012 5013 5014 5015 5016 5017 5018 5019 5020 5021 5022 5023 5024 5025 5026 5027 5028 5029 5030 5031 5032 5033 5034 5035 5036 5037 5038 5039 5040 5041 5042 5043 5044 5045 5046 5047 5048 5049 5050 5051 5052 5053 5054 5055 5056 5057 5058 5059 5060 5061 5062 5063 5064 5065 5066 5067 5068 5069 5070 5071 5072 5073 5074 5075 5076 5077 5078 5079 5080 5081 5082 5083 5084 5085 5086 5087 5088 5089 5090 5091 5092 5093 5094 5095 5096 5097 5098 5099 5100 5101 5102 5103 5104 5105 5106 5107 5108 5109 5110 5111 5112 5113 5114 5115 5116 5117 5118 5119 5120 5121 5122 5123 5124 5125 5126 5127 5128 5129 5130 5131 5132 5133 5134 5135 5136 5137 5138 5139 5140 5141 5142 5143 5144 5145 5146 5147 5148 5149 5150 5151 5152 5153 5154 5155 5156 5157 5158 5159 5160 5161 5162 5163 5164 5165 5166 5167 5168 5169 5170 5171 5172 5173 5174 5175 5176 5177 5178 5179 5180 5181 5182 5183 5184 5185 5186 5187 5188 5189 5190 5191 5192 5193 5194 5195 5196 5197 5198 5199 5200 5201 5202 5203 5204 5205 5206 5207 5208 5209 5210 5211 5212 5213 5214 5215 5216 5217 5218 5219 5220 5221 5222 5223 5224 5225 5226 5227 5228 5229 5230 5231 5232 5233 5234 5235 5236 5237 5238 5239 5240 5241 5242 5243 5244 5245 5246 5247 5248 5249 5250 5251 5252 5253 5254 5255 5256 5257 5258 5259 5260 5261 5262 5263 5264 5265 5266 5267 5268 5269 5270 5271 5272 5273 5274 5275 5276 5277 5278 5279 5280 5281 5282 5283 5284 5285 5286 5287 5288 5289 5290 5291 5292 5293 5294 5295 5296 5297 5298 5299 5300 5301 5302 5303 5304 5305 5306 5307 5308 5309 5310 5311 5312 5313 5314 5315 5316 5317 5318 5319 5320 5321 5322 5323 5324 5325 5326 5327 5328 5329 5330 5331 5332 5333 5334 5335 5336 5337 5338 5339 5340 5341 5342 5343 5344 5345 5346 5347 5348 5349 5350 5351 5352 5353 5354 5355 5356 5357 5358 5359 5360 5361 5362 5363 5364 5365 5366 5367 5368 5369 5370 5371 5372 5373 5374 5375 5376 5377 5378 5379 5380 5381 5382 5383 5384 5385 5386 5387 5388 5389 5390 5391 5392 5393 5394 5395 5396 5397 5398 5399 5400 5401 5402 5403 5404 5405 5406 5407 5408 5409 5410 5411 5412 5413 5414 5415 5416 5417 5418 5419 5420 5421 5422 5423 5424 5425 5426 5427 5428 5429 5430 5431 5432 5433 5434 5435 5436 5437 5438 5439 5440 5441 5442 5443 5444 5445 5446 5447 5448 5449 5450 5451 5452 5453 5454 5455 5456 5457 5458 5459 5460 5461 5462 5463 5464 5465 5466 5467 5468 5469 5470 5471 5472 5473 5474 5475 5476 5477 5478 5479 5480 5481 5482 5483 5484 5485 5486 5487 5488 5489 5490 5491 5492 5493 5494 5495 5496 5497 5498 5499 5500 5501 5502 5503 5504 5505 5506 5507 5508 5509 5510 5511 5512 5513 5514 5515 5516 5517 5518 5519 5520 5521 5522 5523 5524 5525 5526 5527 5528 5529 5530 5531 5532 5533 5534 5535 5536 5537 5538 5539 5540 5541 5542 5543 5544 5545 5546 5547 5548 5549 5550 5551 5552 5553 5554 5555 5556 5557 5558 5559 5560 5561 5562 5563 5564 5565 5566 5567 5568 5569 5570 5571 5572 5573 5574 5575 5576 5577 5578 5579 5580 5581 5582 5583 5584 5585 5586 5587 5588 5589 5590 5591 5592 5593 5594 5595 5596 5597 5598 5599 5600 5601 5602 5603 5604 5605 5606 5607 5608 5609 5610 5611 5612 5613 5614 5615 5616 5617 5618 5619 5620 5621 5622 5623 5624 5625 5626 5627 5628 5629 5630 5631 5632 5633 5634 5635 5636 5637 5638 5639 5640 5641 5642 5643 5644 5645 5646 5647 5648 5649 5650 5651 5652 5653 5654 5655 5656 5657 5658 5659 5660 5661 5662 5663 5664 5665 5666 5667 5668 5669 5670 5671 5672 5673 5674 5675 5676 5677 5678 5679 5680 5681 5682 5683 5684 5685 5686 5687 5688 5689 5690 5691 5692 5693 5694 5695 5696 5697 5698 5699 5700 5701 5702 5703 5704 5705 5706 5707 5708 5709 5710 5711 5712 5713 5714 5715 5716 5717 5718 5719 5720 5721 5722 5723 5724 5725 5726 5727 5728 5729 5730 5731 5732 5733 5734 5735 5736 5737 5738 5739 5740 5741 5742 5743 5744 5745 5746 5747 5748 5749 5750 5751 5752 5753 5754 5755 5756 5757 5758 5759 5760 5761 5762 5763 5764 5765 5766 5767 5768 5769 5770 5771 5772 5773 5774 5775 5776 5777 5778 5779 5780 5781 5782 5783 5784 5785 5786 5787 5788 5789 5790 5791 5792 5793 5794 5795 5796 5797 5798 5799 5800 5801 5802 5803 5804 5805 5806 5807 5808 5809 5810 5811 5812 5813 5814 5815 5816 5817 5818 5819 5820 5821 5822 5823 5824 5825 5826 5827 5828 5829 5830 5831 5832 5833 5834 5835 5836 5837 5838 5839 5840 5841 5842 5843 5844 5845 5846 5847 5848 5849 5850 5851 5852 5853 5854 5855 5856 5857 5858 5859 5860 5861 5862 5863 5864 5865 5866 5867 5868 5869 5870 5871 5872 5873 5874 5875 5876 5877 5878 5879 5880 5881 5882 5883 5884 5885 5886 5887 5888 5889 5890 5891 5892 5893 5894 5895 5896 5897 5898 5899 5900 5901 5902 5903 5904 5905 5906 5907 5908 5909 5910 5911 5912 5913 5914 5915 5916 5917 5918 5919 5920 5921 5922 5923 5924 5925 5926 5927 5928 5929 5930 5931 5932 5933 5934 5935 5936 5937 5938 5939 5940 5941 5942 5943 5944 5945 5946 5947 5948 5949 5950 5951 5952 5953 5954 5955 5956 5957 5958 5959 5960 5961 5962 5963 5964 5965 5966 5967 5968 5969 5970 5971 5972 5973 5974 5975 5976 5977 5978 5979 5980 5981 5982 5983 5984 5985 5986 5987 5988 5989 5990 5991 5992 5993 5994 5995 5996 5997 5998 5999 6000 6001 6002 6003 6004 6005 6006 6007 6008 6009 6010 6011 6012 6013 6014 6015 6016 6017 6018 6019 6020 6021 6022 6023 6024 6025 6026 6027 6028 6029 6030 6031 6032 6033 6034 6035 6036 6037 6038 6039 6040 6041 6042 6043 6044 6045 6046 6047 6048 6049 6050 6051 6052 6053 6054 6055 6056 6057 6058 6059 6060 6061 6062 6063 6064 6065 6066 6067 6068 6069 6070 6071 6072 6073 6074 6075 6076 6077 6078 6079 6080 6081 6082 6083 6084 6085 6086 6087 6088 6089 6090 6091 6092 6093 6094 6095 6096 6097 6098 6099 6100 6101 6102 6103 6104 6105 6106 6107 6108 6109 6110 6111 6112 6113 6114 6115 6116 6117 6118 6119 6120 6121 6122 6123 6124 6125 6126 6127 6128 6129 6130 6131 6132 6133 6134 6135 6136 6137 6138 6139 6140 6141 6142 6143 6144 6145 6146 6147 6148 6149 6150 6151 6152 6153 6154 6155 6156 6157 6158 6159 6160 6161 6162 6163 6164 6165 6166 6167 6168 6169 6170 6171 6172 6173 6174 6175 6176 6177 6178 6179 6180 6181 6182 6183 6184 6185 6186 6187 6188 6189 6190 6191 6192 6193 6194 6195 6196 6197 6198 6199 6200 6201 6202 6203 6204 6205 6206 6207 6208 6209 6210 6211 6212 6213 6214 6215 6216 6217 6218 6219 6220 6221 6222 6223 6224 6225 6226 6227 6228 6229 6230 6231 6232 6233 6234 6235 6236 6237 6238 6239 6240 6241 6242 6243 6244 6245 6246 6247 6248 6249 6250 6251 6252 6253 6254 6255 6256 6257 6258 6259 6260 6261 6262 6263 6264 6265 6266 6267 6268 6269 6270 6271 6272 6273 6274 6275 6276 6277 6278 6279 6280 6281 6282 6283 6284 6285 6286 6287 6288 6289 6290 6291 6292 6293 6294 6295 6296 6297 6298 6299 6300 6301 6302 6303 6304 6305 6306 6307 6308 6309 6310 6311 6312 6313 6314 6315 6316 6317 6318 6319 6320 6321 6322 6323 6324 6325 6326 6327 6328 6329 6330 6331 6332 6333 6334 6335 6336 6337 6338 6339 6340 6341 6342 6343 6344 6345 6346 6347 6348 6349 6350 6351 6352 6353 6354 6355 6356 6357 6358 6359 6360 6361 6362 6363 6364 6365 6366 6367 6368 6369 6370 6371 6372 6373 6374 6375 6376 6377 6378 6379 6380 6381 6382 6383 6384 6385 6386 6387 6388 6389 6390 6391 6392 6393 6394 6395 6396 6397 6398 6399 6400 6401 6402 6403 6404 6405 6406 6407 6408 6409 6410 6411 6412 6413 6414 6415 6416 6417 6418 6419 6420 6421 6422 6423 6424 6425 6426 6427 6428 6429 6430 6431 6432 6433 6434 6435 6436 6437 6438 6439 6440 6441 6442 6443 6444 6445 6446 6447 6448 6449 6450 6451 6452 6453 6454 6455 6456 6457 6458 6459 6460 6461 6462 6463 6464 6465 6466 6467 6468 6469 6470 6471 6472 6473 6474 6475 6476 6477 6478 6479 6480 6481 6482 6483 6484 6485 6486 6487 6488 6489 6490 6491 6492 6493 6494 6495 6496 6497 6498 6499 6500 6501 6502 6503 6504 6505 6506 6507 6508 6509 6510 6511 6512 6513 6514 6515 6516 6517 6518 6519 6520 6521 6522 6523 6524 6525 6526 6527 6528 6529 6530 6531 6532 6533 6534 6535 6536 6537 6538 6539 6540 6541 6542 6543 6544 6545 6546 6547 6548 6549 6550 6551 6552 6553 6554 6555 6556 6557 6558 6559 6560 6561 6562 6563 6564 6565 6566 6567 6568 6569 6570 6571 6572 6573 6574 6575 6576 6577 6578 6579 6580 6581 6582 6583 6584 6585 6586 6587 6588 6589 6590 6591 6592 6593 6594 6595 6596 6597 6598 6599 6600 6601 6602 6603 6604 6605 6606 6607 6608 6609 6610 6611 6612 6613 6614 6615 6616 6617 6618 6619 6620 6621 6622 6623 6624 6625 6626 6627 6628 6629 6630 6631 6632 6633 6634 6635 6636 6637 6638 6639 6640 6641 6642 6643 6644 6645 6646 6647 6648 6649 6650 6651 6652 6653 6654 6655 6656 6657 6658 6659 6660 6661 6662 6663 6664 6665 6666 6667 6668 6669 6670 6671 6672 6673 6674 6675 6676 6677 6678 6679 6680 6681 6682 6683 6684 6685 6686 6687 6688 6689 6690 6691 6692 6693 6694 6695 6696 6697 6698 6699 6700 6701 6702 6703 6704 6705 6706 6707 6708 6709 6710 6711 6712 6713 6714 6715 6716 6717 6718 6719 6720 6721 6722 6723 6724 6725 6726 6727 6728 6729 6730 6731 6732 6733 6734 6735 6736 6737 6738 6739 6740 6741 6742 6743 6744 6745 6746 6747 6748 6749 6750 6751 6752 6753 6754 6755 6756 6757 6758 6759 6760 6761 6762 6763 6764 6765 6766 6767 6768 6769 6770 6771 6772 6773 6774 6775 6776 6777 6778 6779 6780 6781 6782 6783 6784 6785 6786 6787 6788 6789 6790 6791 6792 6793 6794 6795 6796 6797 6798 6799 6800 6801 6802 6803 6804 6805 6806 6807 6808 6809 6810 6811 6812 6813 6814 6815 6816 6817 6818 6819 6820 6821 6822 6823 6824 6825 6826 6827 6828 6829 6830 6831 6832 6833 6834 6835 6836 6837 6838 6839 6840 6841 6842 6843 6844 6845 6846 6847 6848 6849 6850 6851 6852 6853 6854 6855 6856 6857 6858 6859 6860 6861 6862 6863 6864 6865 6866 6867 6868 6869 6870 6871 6872 6873 6874 6875 6876 6877 6878 6879 6880 6881 6882 6883 6884 6885 6886 6887 6888 6889 6890 6891 6892 6893 6894 6895 6896 6897 6898 6899 6900 6901 6902 6903 6904 6905 6906 6907 6908 6909 6910 6911 6912 6913 6914 6915 6916 6917 6918 6919 6920 6921 6922 6923 6924 6925 6926 6927 6928 6929 6930 6931 6932 6933 6934 6935 6936 6937 6938 6939 6940 6941 6942 6943 6944 6945 6946 6947 6948 6949 6950 6951 6952 6953 6954 6955 6956 6957 6958 6959 6960 6961 6962 6963 6964 6965 6966 6967 6968 6969 6970 6971 6972 6973 6974 6975 6976 6977 6978 6979 6980 6981 6982 6983 6984 6985 6986 6987 6988 6989 6990 6991 6992 6993 6994 6995 6996 6997 6998 6999 7000 7001 7002 7003 7004 7005 7006 7007 7008 7009 7010 7011 7012 7013 7014 7015 7016 7017 7018 7019 7020 7021 7022 7023 7024 7025 7026 7027 7028 7029 7030 7031 7032 7033 7034 7035 7036 7037 7038 7039 7040 7041 7042 7043 7044 7045 7046 7047 7048 7049 7050 7051 7052 7053 7054 7055 7056 7057 7058 7059 7060 7061 7062 7063 7064 7065 7066 7067 7068 7069 7070 7071 7072 7073 7074 7075 7076 7077 7078 7079 7080 7081 7082 7083 7084 7085 7086 7087 7088 7089 7090 7091 7092 7093 7094 7095 7096 7097 7098 7099 7100 7101 7102 7103 7104 7105 7106 7107 7108 7109 7110 7111 7112 7113 7114 7115 7116 7117 7118 7119 7120 7121 7122 7123 7124 7125 7126 7127 7128 7129 7130 7131 7132 7133 7134 7135 7136 7137 7138 7139 7140 7141 7142 7143 7144 7145 7146 7147 7148 7149 7150 7151 7152 7153 7154 7155 7156 7157 7158 7159 7160 7161 7162 7163 7164 7165 7166 7167 7168 7169 7170 7171 7172 7173 7174 7175 7176 7177 7178 7179 7180 7181 7182 7183 7184 7185 7186 7187 7188 7189 7190 7191 7192 7193 7194 7195 7196 7197 7198 7199 7200 7201 7202 7203 7204 7205 7206 7207 7208 7209 7210 7211 7212 7213 7214 7215 7216 7217 7218 7219 7220 7221 7222 7223 7224 7225 7226 7227 7228 7229 7230 7231 7232 7233 7234 7235 7236 7237 7238 7239 7240 7241 7242 7243 7244 7245 7246 7247 7248 7249 7250 7251 7252 7253 7254 7255 7256 7257 7258 7259 7260 7261 7262 7263 7264 7265 7266 7267 7268 7269 7270 7271 7272 7273 7274 7275 7276 7277 7278 7279 7280 7281 7282 7283 7284 7285 7286 7287 7288 7289 7290 7291 7292 7293 7294 7295 7296 7297 7298 7299 7300 7301 7302 7303 7304 7305 7306 7307 7308 7309 7310 7311 7312 7313 7314 7315 7316 7317 7318 7319 7320 7321 7322 7323 7324 7325 7326 7327 7328 7329 7330 7331 7332 7333 7334 7335 7336 7337 7338 7339 7340 7341 7342 7343 7344 7345 7346 7347 7348 7349 7350 7351 7352 7353 7354 7355 7356 7357 7358 7359 7360 7361 7362 7363 7364 7365 7366 7367 7368 7369 7370 7371 7372 7373 7374 7375 7376 7377 7378 7379 7380 7381 7382 7383 7384 7385 7386 7387 7388 7389 7390 7391 7392 7393 7394 7395 7396 7397 7398 7399 7400 7401 7402 7403 7404 7405 7406 7407 7408 7409 7410 7411 7412 7413 7414 7415 7416 7417 7418 7419 7420 7421 7422 7423 7424 7425 7426 7427 7428 7429 7430 7431 7432 7433 7434 7435 7436 7437 7438 7439 7440 7441 7442 7443 7444 7445 7446 7447 7448 7449 7450 7451 7452 7453 7454 7455 7456 7457 7458 7459 7460 7461 7462 7463 7464 7465 7466 7467 7468 7469 7470 7471 7472 7473 7474 7475 7476 7477 7478 7479 7480 7481 7482 7483 7484 7485 7486 7487 7488 7489 7490 7491 7492 7493 7494 7495 7496 7497 7498 7499 7500 7501 7502 7503 7504 7505 7506 7507 7508 7509 7510 7511 7512 7513 7514 7515 7516 7517 7518 7519 7520 7521 7522 7523 7524 7525 7526 7527 7528 7529 7530 7531 7532 7533 7534 7535 7536 7537 7538 7539 7540 7541 7542 7543 7544 7545 7546 7547 7548 7549 7550 7551 7552 7553 7554 7555 7556 7557 7558 7559 7560 7561 7562 7563 7564 7565 7566 7567 7568 7569 7570 7571 7572 7573 7574 7575 7576 7577 7578 7579 7580 7581 7582 7583 7584 7585 7586 7587 7588 7589 7590 7591 7592 7593 7594 7595 7596 7597 7598 7599 7600 7601 7602 7603 7604 7605 7606 7607 7608 7609 7610 7611 7612 7613 7614 7615 7616 7617 7618 7619 7620 7621 7622 7623 7624 7625 7626 7627 7628 7629 7630 7631 7632 7633 7634 7635 7636 7637 7638 7639 7640 7641 7642 7643 7644 7645 7646 7647 7648 7649 7650 7651 7652 7653 7654 7655 7656 7657 7658 7659 7660 7661 7662 7663 7664 7665 7666 7667 7668 7669 7670 7671 7672 7673 7674 7675 7676 7677 7678 7679 7680 7681 7682 7683 7684 7685 7686 7687 7688 7689 7690 7691 7692 7693 7694 7695 7696 7697 7698 7699 7700 7701 7702 7703 7704 7705 7706 7707 7708 7709 7710 7711 7712 7713 7714 7715 7716 7717 7718 7719 7720 7721 7722 7723 7724 7725 7726 7727 7728 7729 7730 7731 7732 7733 7734 7735 7736 7737 7738 7739 7740 7741 7742 7743 7744 7745 7746 7747 7748 7749 7750 7751 7752 7753 7754 7755 7756 7757 7758 7759 7760 7761 7762 7763 7764 7765 7766 7767 7768 7769 7770 7771 7772 7773 7774 7775 7776 7777 7778 7779 7780 7781 7782 7783 7784 7785 7786 7787 7788 7789 7790 7791 7792 7793 7794 7795 7796 7797 7798 7799 7800 7801 7802 7803 7804 7805 7806 7807 7808 7809 7810 7811 7812 7813 7814 7815 7816 7817 7818 7819 7820 7821 7822 7823 7824 7825 7826 7827 7828 7829 7830 7831 7832 7833 7834 7835 7836 7837 7838 7839 7840 7841 7842 7843 7844 7845 7846 7847 7848 7849 7850 7851 7852 7853 7854 7855 7856 7857 7858 7859 7860 7861 7862 7863 7864 7865 7866 7867 7868 7869 7870 7871 7872 7873 7874 7875 7876 7877 7878 7879 7880 7881 7882 7883 7884 7885 7886 7887 7888 7889 7890 7891 7892 7893 7894 7895 7896 7897 7898 7899 7900 7901 7902 7903 7904 7905 7906 7907 7908 7909 7910 7911 7912 7913 7914 7915 7916 7917 7918 7919 7920 7921 7922 7923 7924 7925 7926 7927 7928 7929 7930 7931 7932 7933 7934 7935 7936 7937 7938 7939 7940 7941 7942 7943 7944 7945 7946 7947 7948 7949 7950 7951 7952 7953 7954 7955 7956 7957 7958 7959 7960 7961 7962 7963 7964 7965 7966 7967 7968 7969 7970 7971 7972 7973 7974 7975 7976 7977 7978 7979 7980 7981 7982 7983 7984 7985 7986 7987 7988 7989 7990 7991 7992 7993 7994 7995 7996 7997 7998 7999 8000 8001 8002 8003 8004 8005 8006 8007 8008 8009 8010 8011 8012 8013 8014 8015 8016 8017 8018 8019 8020 8021 8022 8023 8024 8025 8026 8027 8028 8029 8030 8031 8032 8033 8034 8035 8036 8037 8038 8039 8040 8041 8042 8043 8044 8045 8046 8047 8048 8049 8050 8051 8052 8053 8054 8055 8056 8057 8058 8059 8060 8061 8062 8063 8064 8065 8066 8067 8068 8069 8070 8071 8072 8073 8074 8075 8076 8077 8078 8079 8080 8081 8082 8083 8084 8085 8086 8087 8088 8089 8090 8091 8092 8093 8094 8095 8096 8097 8098 8099 8100 8101 8102 8103 8104 8105 8106 8107 8108 8109 8110 8111 8112 8113 8114 8115 8116 8117 8118 8119 8120 8121 8122 8123 8124 8125 8126 8127 8128 8129 8130 8131 8132 8133 8134 8135 8136 8137 8138 8139 8140 8141 8142 8143 8144 8145 8146 8147 8148 8149 8150 8151 8152 8153 8154 8155 8156 8157 8158 8159 8160 8161 8162 8163 8164 8165 8166 8167 8168 8169 8170 8171 8172 8173 8174 8175 8176 8177 8178 8179 8180 8181 8182 8183 8184 8185 8186 8187 8188 8189 8190 8191 8192 8193 8194 8195 8196 8197 8198 8199 8200 8201 8202 8203 8204 8205 8206 8207 8208 8209 8210 8211 8212 8213 8214 8215 8216 8217 8218 8219 8220 8221 8222 8223 8224 8225 8226 8227 8228 8229 8230 8231 8232 8233 8234 8235 8236 8237 8238 8239 8240 8241 8242 8243 8244 8245 8246 8247 8248 8249 8250 8251 8252 8253 8254 8255 8256 8257 8258 8259 8260 8261 8262 8263 8264 8265 8266 8267 8268 8269 8270 8271 8272 8273 8274 8275 8276 8277 8278 8279 8280 8281 8282 8283 8284 8285 8286 8287 8288 8289 8290 8291 8292 8293 8294 8295 8296 8297 8298 8299 8300 8301 8302 8303 8304 8305 8306 8307 8308 8309 8310 8311 8312 8313 8314 8315 8316 8317 8318 8319 8320 8321 8322 8323 8324 8325 8326 8327 8328 8329 8330 8331 8332 8333 8334 8335 8336 8337 8338 8339 8340 8341 8342 8343 8344 8345 8346 8347 8348 8349 8350 8351 8352 8353 8354 8355 8356 8357 8358 8359 8360 8361 8362 8363 8364 8365 8366 8367 8368 8369 8370 8371 8372 8373 8374 8375 8376 8377 8378 8379 8380 8381 8382 8383 8384 8385 8386 8387 8388 8389 8390 8391 8392 8393 8394 8395 8396 8397 8398 8399 8400 8401 8402 8403 8404 8405 8406 8407 8408 8409 8410 8411 8412 8413 8414 8415 8416 8417 8418 8419 8420 8421 8422 8423 8424 8425 8426 8427 8428 8429 8430 8431 8432 8433 8434 8435 8436 8437 8438 8439 8440 8441 8442 8443 8444 8445 8446 8447 8448 8449 8450 8451 8452 8453 8454 8455 8456 8457 8458 8459 8460 8461 8462 8463 8464 8465 8466 8467 8468 8469 8470 8471 8472 8473 8474 8475 8476 8477 8478 8479 8480 8481 8482 8483 8484 8485 8486 8487 8488 8489 8490 8491 8492 8493 8494 8495 8496 8497 8498 8499 8500 8501 8502 8503 8504 8505 8506 8507 8508 8509 8510 8511 8512 8513 8514 8515 8516 8517 8518 8519 8520 8521 8522 8523 8524 8525 8526 8527 8528 8529 8530 8531 8532 8533 8534 8535 8536 8537 8538 8539 8540 8541 8542 8543 8544 8545 8546 8547 8548 8549 8550 8551 8552 8553 8554 8555 8556 8557 8558 8559 8560 8561 8562 8563 8564 8565 8566 8567 8568 8569 8570 8571 8572 8573 8574 8575 8576 8577 8578 8579 8580 8581 8582 8583 8584 8585 8586 8587 8588 8589 8590 8591 8592 8593 8594 8595 8596 8597 8598 8599 8600 8601 8602 8603 8604 8605 8606 8607 8608 8609 8610 8611 8612 8613 8614 8615 8616 8617 8618 8619 8620 8621 8622 8623 8624 8625 8626 8627 8628 8629 8630 8631 8632 8633 8634 8635 8636 8637 8638 8639 8640 8641 8642 8643 8644 8645 8646 8647 8648 8649 8650 8651 8652 8653 8654 8655 8656 8657 8658 8659 8660 8661 8662 8663 8664 8665 8666 8667 8668 8669 8670 8671 8672 8673 8674 8675 8676 8677 8678 8679 8680 8681 8682 8683 8684 8685 8686 8687 8688 8689 8690 8691 8692 8693 8694 8695 8696 8697 8698 8699 8700 8701 8702 8703 8704 8705 8706 8707 8708 8709 8710 8711 8712 8713 8714 8715 8716 8717 8718 8719 8720 8721 8722 8723 8724 8725 8726 8727 8728 8729 8730 8731 8732 8733 8734 8735 8736 8737 8738 8739 8740 8741 8742 8743 8744 8745 8746 8747 8748 8749 8750 8751 8752 8753 8754 8755 8756 8757 8758 8759 8760 8761 8762 8763 8764 8765 8766 8767 8768 8769 8770 8771 8772 8773 8774 8775 8776 8777 8778 8779 8780 8781 8782 8783 8784 8785 8786 8787 8788 8789 8790 8791 8792 8793 8794 8795 8796 8797 8798 8799 8800 8801 8802 8803 8804 8805 8806 8807 8808 8809 8810 8811 8812 8813 8814 8815 8816 8817 8818 8819 8820 8821 8822 8823 8824 8825 8826 8827 8828 8829 8830 8831 8832 8833 8834 8835 8836 8837 8838 8839 8840 8841 8842 8843 8844 8845 8846 8847 8848 8849 8850 8851 8852 8853 8854 8855 8856 8857 8858 8859 8860 8861 8862 8863 8864 8865 8866 8867 8868 8869 8870 8871 8872 8873 8874 8875 8876 8877 8878 8879 8880 8881 8882 8883 8884 8885 8886 8887 8888 8889 8890 8891 8892 8893 8894 8895 8896 8897 8898 8899 8900 8901 8902 8903 8904 8905 8906 8907 8908 8909 8910 8911 8912 8913 8914 8915 8916 8917 8918 8919 8920 8921 8922 8923 8924 8925 8926 8927 8928 8929 8930 8931 8932 8933 8934 8935 8936 8937 8938 8939 8940 8941 8942 8943 8944 8945 8946 8947 8948 8949 8950 8951 8952 8953 8954 8955 8956 8957 8958 8959 8960 8961 8962 8963 8964 8965 8966 8967 8968 8969 8970 8971 8972 8973 8974 8975 8976 8977 8978 8979 8980 8981 8982 8983 8984 8985 8986 8987 8988 8989 8990 8991 8992 8993 8994 8995 8996 8997 8998 8999 9000 9001 9002 9003 9004 9005 9006 9007 9008 9009 9010 9011 9012 9013 9014 9015 9016 9017 9018 9019 9020 9021 9022 9023 9024 9025 9026 9027 9028 9029 9030 9031 9032 9033 9034 9035 9036 9037 9038 9039 9040 9041 9042 9043 9044 9045 9046 9047 9048 9049 9050 9051 9052 9053 9054 9055 9056 9057 9058 9059 9060 9061 9062 9063 9064 9065 9066 9067 9068 9069 9070 9071 9072 9073 9074 9075 9076 9077 9078 9079 9080 9081 9082 9083 9084 9085 9086 9087 9088 9089 9090 9091 9092 9093 9094 9095 9096 9097 9098 9099 9100 9101 9102 9103 9104 9105 9106 9107 9108 9109 9110 9111 9112 9113 9114 9115 9116 9117 9118 9119 9120 9121 9122 9123 9124 9125 9126 9127 9128 9129 9130 9131 9132 9133 9134 9135 9136 9137 9138 9139 9140 9141 9142 9143 9144 9145 9146 9147 9148 9149 9150 9151 9152 9153 9154 9155 9156 9157 9158 9159 9160 9161 9162 9163 9164 9165 9166 9167 9168 9169 9170 9171 9172 9173 9174 9175 9176 9177 9178 9179 9180 9181 9182 9183 9184 9185 9186 9187 9188 9189 9190 9191 9192 9193 9194 9195 9196 9197 9198 9199 9200 9201 9202 9203 9204 9205 9206 9207 9208 9209 9210 9211 9212 9213 9214 9215 9216 9217 9218 9219 9220 9221 9222 9223 9224 9225 9226 9227 9228 9229 9230 9231 9232 9233 9234 9235 9236 9237 9238 9239 9240 9241 9242 9243 9244 9245 9246 9247 9248 9249 9250 9251 9252 9253 9254 9255 9256 9257 9258 9259 9260 9261 9262 9263 9264 9265 9266 9267 9268 9269 9270 9271 9272 9273 9274 9275 9276 9277 9278 9279 9280 9281 9282 9283 9284 9285 9286 9287 9288 9289 9290 9291 9292 9293 9294 9295 9296 9297 9298 9299 9300 9301 9302 9303 9304 9305 9306 9307 9308 9309 9310 9311 9312 9313 9314 9315 9316 9317 9318 9319 9320 9321 9322 9323 9324 9325 9326 9327 9328 9329 9330 9331 9332 9333 9334 9335 9336 9337 9338 9339 9340 9341 9342 9343 9344 9345 9346 9347 9348 9349 9350 9351 9352 9353 9354 9355 9356 9357 9358 9359 9360 9361 9362 9363 9364 9365 9366 9367 9368 9369 9370 9371 9372 9373 9374 9375 9376 9377 9378 9379 9380 9381 9382 9383 9384 9385 9386 9387 9388 9389 9390 9391 9392 9393 9394 9395 9396 9397 9398 9399 9400 9401 9402 9403 9404 9405 9406 9407 9408 9409 9410 9411 9412 9413 9414 9415 9416 9417 9418 9419 9420 9421 9422 9423 9424 9425 9426 9427 9428 9429 9430 9431 9432 9433 9434 9435 9436 9437 9438 9439 9440 9441 9442 9443 9444 9445 9446 9447 9448 9449 9450 9451 9452 9453 9454 9455 9456 9457 9458 9459 9460 9461 9462 9463 9464 9465 9466 9467 9468 9469 9470 9471 9472 9473 9474 9475 9476 9477 9478 9479 9480 9481 9482 9483 9484 9485 9486 9487 9488 9489 9490 9491 9492 9493 9494 9495 9496 9497 9498 9499 9500 9501 9502 9503 9504 9505 9506 9507 9508 9509 9510 9511 9512 9513 9514 9515 9516 9517 9518 9519 9520 9521 9522 9523 9524 9525 9526 9527 9528 9529 9530 9531 9532 9533 9534 9535 9536 9537 9538 9539 9540 9541 9542 9543 9544 9545 9546 9547 9548 9549 9550 9551 9552 9553 9554 9555 9556 9557 9558 9559 9560 9561 9562 9563 9564 9565 9566 9567 9568 9569 9570 9571 9572 9573 9574 9575 9576 9577 9578 9579 9580 9581 9582 9583 9584 9585 9586 9587 9588 9589 9590 9591 9592 9593 9594 9595 9596 9597 9598 9599 9600 9601 9602 9603 9604 9605 9606 9607 9608 9609 9610 9611 9612 9613 9614 9615 9616 9617 9618 9619 9620 9621 9622 9623 9624 9625 9626 9627 9628 9629 9630 9631 9632 9633 9634 9635 9636 9637 9638 9639 9640 9641 9642 9643 9644 9645 9646 9647 9648 9649 9650 9651 9652 9653 9654 9655 9656 9657 9658 9659 9660 9661 9662 9663 9664 9665 9666 9667 9668 9669 9670 9671 9672 9673 9674 9675 9676 9677 9678 9679 9680 9681 9682 9683 9684 9685 9686 9687 9688 9689 9690 9691 9692 9693 9694 9695 9696 9697 9698 9699 9700 9701 9702 9703 9704 9705 9706 9707 9708 9709 9710 9711 9712 9713 9714 9715 9716 9717 9718 9719 9720 9721 9722 9723 9724 9725 9726 9727 9728 9729 9730 9731 9732 9733 9734 9735 9736 9737 9738 9739 9740 9741 9742 9743 9744 9745 9746 9747 9748 9749 9750 9751 9752 9753 9754 9755 9756 9757 9758 9759 9760 9761 9762 9763 9764 9765 9766 9767 9768 9769 9770 9771 9772 9773 9774 9775 9776 9777 9778 9779 9780 9781 9782 9783 9784 9785 9786 9787 9788 9789 9790 9791 9792 9793 9794 9795 9796 9797 9798 9799 9800 9801 9802 9803 9804 9805 9806 9807 9808 9809 9810 9811 9812 9813 9814 9815 9816 9817 9818 9819 9820 9821 9822 9823 9824 9825 9826 9827 9828 9829 9830 9831 9832 9833 9834 9835 9836 9837 9838 9839 9840 9841 9842 9843 9844 9845 9846 9847 9848 9849 9850 9851 9852 9853 9854 9855 9856 9857 9858 9859 9860 9861 9862 9863 9864 9865 9866 9867 9868 9869 9870 9871 9872 9873 9874 9875 9876 9877 9878 9879 9880 9881 9882 9883 9884 9885 9886 9887 9888 9889 9890 9891 9892 9893 9894 9895 9896 9897 9898 9899 9900 9901 9902 9903 9904 9905 9906 9907 9908 9909 9910 9911 9912 9913 9914 9915 9916 9917 9918 9919 9920 9921 9922 9923 9924 9925 9926 9927 9928 9929 9930 9931 9932 9933 9934 9935 9936 9937 9938 9939 9940 9941 9942 9943 9944 9945 9946 9947 9948 9949 9950 9951 9952 9953 9954 9955 9956 9957 9958 9959 9960 9961 9962 9963 9964 9965 9966 9967 9968 9969 9970 9971 9972 9973 9974 9975 9976 9977 9978 9979 9980 9981 9982 9983 9984 9985 9986 9987 9988 9989 9990 9991 9992 9993 9994 9995 9996 9997 9998 9999 10000 10001 10002 10003 10004 10005 10006 10007 10008 10009 10010 10011 10012 10013 10014 10015 10016 10017 10018 10019 10020 10021 10022 10023 10024 10025 10026 10027 10028 10029 10030 10031 10032 10033 10034 10035 10036 10037 10038 10039 10040 10041 10042 10043 10044 10045 10046 10047 10048 10049 10050 10051 10052 10053 10054 10055 10056 10057 10058 10059 10060 10061 10062 10063 10064 10065 10066 10067 10068 10069 10070 10071 10072 10073 10074 10075 10076 10077 10078 10079 10080 10081 10082 10083 10084 10085 10086 10087 10088 10089 10090 10091 10092 10093 10094 10095 10096 10097 10098 10099 10100 10101 10102 10103 10104 10105 10106 10107 10108 10109 10110 10111 10112 10113 10114 10115 10116 10117 10118 10119 10120 10121 10122 10123 10124 10125 10126 10127 10128 10129 10130 10131 10132 10133 10134 10135 10136 10137 10138 10139 10140 10141 10142 10143 10144 10145 10146 10147 10148 10149 10150 10151 10152 10153 10154 10155 10156 10157 10158 10159 10160 10161 10162 10163 10164 10165 10166 10167 10168 10169 10170 10171 10172 10173 10174 10175 10176 10177 10178 10179 10180 10181 10182 10183 10184 10185 10186 10187 10188 10189 10190 10191 10192 10193 10194 10195 10196 10197 10198 10199 10200 10201 10202 10203 10204 10205 10206 10207 10208 10209 10210 10211 10212 10213 10214 10215 10216 10217 10218 10219 10220 10221 10222 10223 10224 10225 10226 10227 10228 10229 10230 10231 10232 10233 10234 10235 10236 10237 10238 10239 10240 10241 10242 10243 10244 10245 10246 10247 10248 10249 10250 10251 10252 10253 10254 10255 10256 10257 10258 10259 10260 10261 10262 10263 10264 10265 10266 10267 10268 10269 10270 10271 10272 10273 10274 10275 10276 10277 10278 10279 10280 10281 10282 10283 10284 10285 10286 10287 10288 10289 10290 10291 10292 10293 10294 10295 10296 10297 10298 10299 10300 10301 10302 10303 10304 10305 10306 10307 10308 10309 10310 10311 10312 10313 10314 10315 10316 10317 10318 10319 10320 10321 10322 10323 10324 10325 10326 10327 10328 10329 10330 10331 10332 10333 10334 10335 10336 10337 10338 10339 10340 10341 10342 10343 10344 10345 10346 10347 10348 10349 10350 10351 10352 10353 10354 10355 10356 10357 10358 10359 10360 10361 10362 10363 10364 10365 10366 10367 10368 10369 10370 10371 10372 10373 10374 10375 10376 10377 10378 10379 10380 10381 10382 10383 10384 10385 10386 10387 10388 10389 10390 10391 10392 10393 10394 10395 10396 10397 10398 10399 10400 10401 10402 10403 10404 10405 10406 10407 10408 10409 10410 10411 10412 10413 10414 10415 10416 10417 10418 10419 10420 10421 10422 10423 10424 10425 10426 10427 10428 10429 10430 10431 10432 10433 10434 10435 10436 10437 10438 10439 10440 10441 10442 10443 10444 10445 10446 10447 10448 10449 10450 10451 10452 10453 10454 10455 10456 10457 10458 10459 10460 10461 10462 10463 10464 10465 10466 10467 10468 10469 10470 10471 10472 10473 10474 10475 10476 10477 10478 10479 10480 10481 10482 10483 10484 10485 10486 10487 10488 10489 10490 10491 10492 10493 10494 10495 10496 10497 10498 10499 10500 10501 10502 10503 10504 10505 10506 10507 10508 10509 10510 10511 10512 10513 10514 10515 10516 10517 10518 10519 10520 10521 10522 10523 10524 10525 10526 10527 10528 10529 10530 10531 10532 10533 10534 10535 10536 10537 10538 10539 10540 10541 10542 10543 10544 10545 10546 10547 10548 10549 10550 10551 10552 10553 10554 10555 10556 10557 10558 10559 10560 10561 10562 10563 10564 10565 10566 10567 10568 10569 10570 10571 10572 10573 10574 10575 10576 10577 10578 10579 10580 10581 10582 10583 10584 10585 10586 10587 10588 10589 10590 10591 10592 10593 10594 10595 10596 10597 10598 10599 10600 10601 10602 10603 10604 10605 10606 10607 10608 10609 10610 10611 10612 10613 10614 10615 10616 10617 10618 10619 10620 10621 10622 10623 10624 10625 10626 10627 10628 10629 10630 10631 10632 10633 10634 10635 10636 10637 10638 10639 10640 10641 10642 10643 10644 10645 10646 10647 10648 10649 10650 10651 10652 10653 10654 10655 10656 10657 10658 10659 10660 10661 10662 10663 10664 10665 10666 10667 10668 10669 10670 10671 10672 10673 10674 10675 10676 10677 10678 10679 10680 10681 10682 10683 10684 10685 10686 10687 10688 10689 10690 10691 10692 10693 10694 10695 10696 10697 10698 10699 10700 10701 10702 10703 10704 10705 10706 10707 10708 10709 10710 10711 10712 10713 10714 10715 10716 10717 10718 10719 10720 10721 10722 10723 10724 10725 10726 10727 10728 10729 10730 10731 10732 10733 10734 10735 10736 10737 10738 10739 10740 10741 10742 10743 10744 10745 10746 10747 10748 10749 10750 10751 10752 10753 10754 10755 10756 10757 10758 10759 10760 10761 10762 10763 10764 10765 10766 10767 10768 10769 10770 10771 10772 10773 10774 10775 10776 10777 10778 10779 10780 10781 10782 10783 10784 10785 10786 10787 10788 10789 10790 10791 10792 10793 10794 10795 10796 10797 10798 10799 10800 10801 10802 10803 10804 10805 10806 10807 10808 10809 10810 10811 10812 10813 10814 10815 10816 10817 10818 10819 10820 10821 10822 10823 10824 10825 10826 10827 10828 10829 10830 10831 10832 10833 10834 10835 10836 10837 10838 10839 10840 10841 10842 10843 10844 10845 10846 10847 10848 10849 10850 10851 10852 10853 10854 10855 10856 10857 10858 10859 10860 10861 10862 10863 10864 10865 10866 10867 10868 10869 10870 10871 10872 10873 10874 10875 10876 10877 10878 10879 10880 10881 10882 10883 10884 10885 10886 10887 10888 10889 10890 10891 10892 10893 10894 10895 10896 10897 10898 10899 10900 10901 10902 10903 10904 10905 10906 10907 10908 10909 10910 10911 10912 10913 10914 10915 10916 10917 10918 10919 10920 10921 10922 10923 10924 10925 10926 10927 10928 10929 10930 10931 10932 10933 10934 10935 10936 10937 10938 10939 10940 10941 10942 10943 10944 10945 10946 10947 10948 10949 10950 10951 10952 10953 10954 10955 10956 10957 10958 10959 10960 10961 10962 10963 10964 10965 10966 10967 10968 10969 10970 10971 10972 10973 10974 10975 10976 10977 10978 10979 10980 10981 10982 10983 10984 10985 10986 10987 10988 10989 10990 10991 10992 10993 10994 10995 10996 10997 10998 10999 11000 11001 11002 11003 11004 11005 11006 11007 11008 11009 11010 11011 11012 11013 11014 11015 11016 11017 11018 11019 11020 11021 11022 11023 11024 11025 11026 11027 11028 11029 11030 11031 11032 11033 11034 11035 11036 11037 11038 11039 11040 11041 11042 11043 11044 11045 11046 11047 11048 11049 11050 11051 11052 11053 11054 11055 11056 11057 11058 11059 11060 11061 11062 11063 11064 11065 11066 11067 11068 11069 11070 11071 11072 11073 11074 11075 11076 11077 11078 11079 11080 11081 11082 11083 11084 11085 11086 11087 11088 11089 11090 11091 11092 11093 11094 11095 11096 11097 11098 11099 11100 11101 11102 11103 11104 11105 11106 11107 11108 11109 11110 11111 11112 11113 11114 11115 11116 11117 11118 11119 11120 11121 11122 11123 11124 11125 11126 11127 11128 11129 11130 11131 11132 11133 11134 11135 11136 11137 11138 11139 11140 11141 11142 11143 11144 11145 11146 11147 11148 11149 11150 11151 11152 11153 11154 11155 11156 11157 11158 11159 11160 11161 11162 11163 11164 11165 11166 11167 11168 11169 11170 11171 11172 11173 11174 11175 11176 11177 11178 11179 11180 11181 11182 11183 11184 11185 11186 11187 11188 11189 11190 11191 11192 11193 11194 11195 11196 11197 11198 11199 11200 11201 11202 11203 11204 11205 11206 11207 11208 11209 11210 11211 11212 11213 11214 11215 11216 11217 11218 11219 11220 11221 11222 11223 11224 11225 11226 11227 11228 11229 11230 11231 11232 11233 11234 11235 11236 11237 11238 11239 11240 11241 11242 11243 11244 11245 11246 11247 11248 11249 11250 11251 11252 11253 11254 11255 11256 11257 11258 11259 11260 11261 11262 11263 11264 11265 11266 11267 11268 11269 11270 11271 11272 11273 11274 11275 11276 11277 11278 11279 11280 11281 11282 11283 11284 11285 11286 11287 11288 11289 11290 11291 11292 11293 11294 11295 11296 11297 11298 11299 11300 11301 11302 11303 11304 11305 11306 11307 11308 11309 11310 11311 11312 11313 11314 11315 11316 11317 11318 11319 11320 11321 11322 11323 11324 11325 11326 11327 11328 11329 11330 11331 11332 11333 11334 11335 11336 11337 11338 11339 11340 11341 11342 11343 11344 11345 11346 11347 11348 11349 11350 11351 11352 11353 11354 11355 11356 11357 11358 11359 11360 11361 11362 11363 11364 11365 11366 11367 11368 11369 11370 11371 11372 11373 11374 11375 11376 11377 11378 11379 11380 11381 11382 11383 11384 11385 11386 11387 11388 11389 11390 11391 11392 11393 11394 11395 11396 11397 11398 11399 11400 11401 11402 11403 11404 11405 11406 11407 11408 11409 11410 11411 11412 11413 11414 11415 11416 11417 11418 11419 11420 11421 11422 11423 11424 11425 11426 11427 11428 11429 11430 11431 11432 11433 11434 11435 11436 11437 11438 11439 11440 11441 11442 11443 11444 11445 11446 11447 11448 11449 11450 11451 11452 11453 11454 11455 11456 11457 11458 11459 11460 11461 11462 11463 11464 11465 11466 11467 11468 11469 11470 11471 11472 11473 11474 11475 11476 11477 11478 11479 11480 11481 11482 11483 11484 11485 11486 11487 11488 11489 11490 11491 11492 11493 11494 11495 11496 11497 11498 11499 11500 11501 11502 11503 11504 11505 11506 11507 11508 11509 11510 11511 11512 11513 11514 11515 11516 11517 11518 11519 11520 11521 11522 11523 11524 11525 11526 11527 11528 11529 11530 11531 11532 11533 11534 11535 11536 11537 11538 11539 11540 11541 11542 11543 11544 11545 11546 11547 11548 11549 11550 11551 11552 11553 11554 11555 11556 11557 11558 11559 11560 11561 11562 11563 11564 11565 11566 11567 11568 11569 11570 11571 11572 11573 11574 11575 11576 11577 11578 11579 11580 11581 11582 11583 11584 11585 11586 11587 11588 11589 11590 11591 11592 11593 11594 11595 11596 11597 11598 11599 11600 11601 11602 11603 11604 11605 11606 11607 11608 11609 11610 11611 11612 11613 11614 11615 11616 11617 11618 11619 11620 11621 11622 11623 11624 11625 11626 11627 11628 11629 11630 11631 11632 11633 11634 11635 11636 11637 11638 11639 11640 11641 11642 11643 11644 11645 11646 11647 11648 11649 11650 11651 11652 11653 11654 11655 11656 11657 11658 11659 11660 11661 11662 11663 11664 11665 11666 11667 11668 11669 11670 11671 11672 11673 11674 11675 11676 11677 11678 11679 11680 11681 11682 11683 11684 11685 11686 11687 11688 11689 11690 11691 11692 11693 11694 11695 11696 11697 11698 11699 11700 11701 11702 11703 11704 11705 11706 11707 11708 11709 11710 11711 11712 11713 11714 11715 11716 11717 11718 11719 11720 11721 11722 11723 11724 11725 11726 11727 11728 11729 11730 11731 11732 11733 11734 11735 11736 11737 11738 11739 11740 11741 11742 11743 11744 11745 11746 11747 11748 11749 11750 11751 11752 11753 11754 11755 11756 11757 11758 11759 11760 11761 11762 11763 11764 11765 11766 11767 11768 11769 11770 11771 11772 11773 11774 11775 11776 11777 11778 11779 11780 11781 11782 11783 11784 11785 11786 11787 11788 11789 11790 11791 11792 11793 11794 11795 11796 11797 11798 11799 11800 11801 11802 11803 11804 11805 11806 11807 11808 11809 11810 11811 11812 11813 11814 11815 11816 11817 11818 11819 11820 11821 11822 11823 11824 11825 11826 11827 11828 11829 11830 11831 11832 11833 11834 11835 11836 11837 11838 11839 11840 11841 11842 11843 11844 11845 11846 11847 11848 11849 11850 11851 11852 11853 11854 11855 11856 11857 11858 11859 11860 11861 11862 11863 11864 11865 11866 11867 11868 11869 11870 11871 11872 11873 11874 11875 11876 11877 11878 11879 11880 11881 11882 11883 11884 11885 11886 11887 11888 11889 11890 11891 11892 11893 11894 11895 11896 11897 11898 11899 11900 11901 11902 11903 11904 11905 11906 11907 11908 11909 11910 11911 11912 11913 11914 11915 11916 11917 11918 11919 11920 11921 11922 11923 11924 11925 11926 11927 11928 11929 11930 11931 11932 11933 11934 11935 11936 11937 11938 11939 11940 11941 11942 11943 11944 11945 11946 11947 11948 11949 11950 11951 11952 11953 11954 11955 11956 11957 11958 11959 11960 11961 11962 11963 11964 11965 11966 11967 11968 11969 11970 11971 11972 11973 11974 11975 11976 11977 11978 11979 11980 11981 11982 11983 11984 11985 11986 11987 11988 11989 11990 11991 11992 11993 11994 11995 11996 11997 11998 11999 12000 12001 12002 12003 12004 12005 12006 12007 12008 12009 12010 12011 12012 12013 12014 12015 12016 12017 12018 12019 12020 12021 12022 12023 12024 12025 12026 12027 12028 12029 12030 12031 12032 12033 12034 12035 12036 12037 12038 12039 12040 12041 12042 12043 12044 12045 12046 12047 12048 12049 12050 12051 12052 12053 12054 12055 12056 12057 12058 12059 12060 12061 12062 12063 12064 12065 12066 12067 12068 12069 12070 12071 12072 12073 12074 12075 12076 12077 12078 12079 12080 12081 12082 12083 12084 12085 12086 12087 12088 12089 12090 12091 12092 12093 12094 12095 12096 12097 12098 12099 12100 12101 12102 12103 12104 12105 12106 12107 12108 12109 12110 12111 12112 12113 12114 12115 12116 12117 12118 12119 12120 12121 12122 12123 12124 12125 12126 12127 12128 12129 12130 12131 12132 12133 12134 12135 12136 12137 12138 12139 12140 12141 12142 12143 12144 12145 12146 12147 12148 12149 12150 12151 12152 12153 12154 12155 12156 12157 12158 12159 12160 12161 12162 12163 12164 12165 12166 12167 12168 12169 12170 12171 12172 12173 12174 12175 12176 12177 12178 12179 12180 12181 12182 12183 12184 12185 12186 12187 12188 12189 12190 12191 12192 12193 12194 12195 12196 12197 12198 12199 12200 12201 12202 12203 12204 12205 12206 12207 12208 12209 12210 12211 12212 12213 12214 12215 12216 12217 12218 12219 12220 12221 12222 12223 12224 12225 12226 12227 12228 12229 12230 12231 12232 12233 12234 12235 12236 12237 12238 12239 12240 12241 12242 12243 12244 12245 12246 12247 12248 12249 12250 12251 12252 12253 12254 12255 12256 12257 12258 12259 12260 12261 12262 12263 12264 12265 12266 12267 12268 12269 12270 12271 12272 12273 12274 12275 12276 12277 12278 12279 12280 12281 12282 12283 12284 12285 12286 12287 12288 12289 12290 12291 12292 12293 12294 12295 12296 12297 12298 12299 12300 12301 12302 12303 12304 12305 12306 12307 12308 12309 12310 12311 12312 12313 12314 12315 12316 12317 12318 12319 12320 12321 12322 12323 12324 12325 12326 12327 12328 12329 12330 12331 12332 12333 12334 12335 12336 12337 12338 12339 12340 12341 12342 12343 12344 12345 12346 12347 12348 12349 12350 12351 12352 12353 12354 12355 12356 12357 12358 12359 12360 12361 12362 12363 12364 12365 12366 12367 12368 12369 12370 12371 12372 12373 12374 12375 12376 12377 12378 12379 12380 12381 12382 12383 12384 12385 12386 12387 12388 12389 12390 12391 12392 12393 12394 12395 12396 12397 12398 12399 12400 12401 12402 12403 12404 12405 12406 12407 12408 12409 12410 12411 12412 12413 12414 12415 12416 12417 12418 12419 12420 12421 12422 12423 12424 12425 12426 12427 12428 12429 12430 12431 12432 12433 12434 12435 12436 12437 12438 12439 12440 12441 12442 12443 12444 12445 12446 12447 12448 12449 12450 12451 12452 12453 12454 12455 12456 12457 12458 12459 12460 12461 12462 12463 12464 12465 12466 12467 12468 12469 12470 12471 12472 12473 12474 12475 12476 12477 12478 12479 12480 12481 12482 12483 12484 12485 12486 12487 12488 12489 12490 12491 12492 12493 12494 12495 12496 12497 12498 12499 12500 12501 12502 12503 12504 12505 12506 12507 12508 12509 12510 12511 12512 12513 12514 12515 12516 12517 12518 12519 12520 12521 12522 12523 12524 12525 12526 12527 12528 12529 12530 12531 12532 12533 12534 12535 12536 12537 12538 12539 12540 12541 12542 12543 12544 12545 12546 12547 12548 12549 12550 12551 12552 12553 12554 12555 12556 12557 12558 12559 12560 12561 12562 12563 12564 12565 12566 12567 12568 12569 12570 12571 12572 12573 12574 12575 12576 12577 12578 12579 12580 12581 12582 12583 12584 12585 12586 12587 12588 12589 12590 12591 12592 12593 12594 12595 12596 12597 12598 12599 12600 12601 12602 12603 12604 12605 12606 12607 12608 12609 12610 12611 12612 12613 12614 12615 12616 12617 12618 12619 12620 12621 12622 12623 12624 12625 12626 12627 12628 12629 12630 12631 12632 12633 12634 12635 12636 12637 12638 12639 12640 12641 12642 12643 12644 12645 12646 12647 12648 12649 12650 12651 12652 12653 12654 12655 12656 12657 12658 12659 12660 12661 12662 12663 12664 12665 12666 12667 12668 12669 12670 12671 12672 12673 12674 12675 12676 12677 12678 12679 12680 12681 12682 12683 12684 12685 12686 12687 12688 12689 12690 12691 12692 12693 12694 12695 12696 12697 12698 12699 12700 12701 12702 12703 12704 12705 12706 12707 12708 12709 12710 12711 12712 12713 12714 12715 12716 12717 12718 12719 12720 12721 12722 12723 12724 12725 12726 12727 12728 12729 12730 12731 12732 12733 12734 12735 12736 12737 12738 12739 12740 12741 12742 12743 12744 12745 12746 12747 12748 12749 12750 12751 12752 12753 12754 12755 12756 12757 12758 12759 12760 12761 12762 12763 12764 12765 12766 12767 12768 12769 12770 12771 12772 12773 12774 12775 12776 12777 12778 12779 12780 12781 12782 12783 12784 12785 12786 12787 12788 12789 12790 12791 12792 12793 12794 12795 12796 12797 12798 12799 12800 12801 12802 12803 12804 12805 12806 12807 12808 12809 12810 12811 12812 12813 12814 12815 12816 12817 12818 12819 12820 12821 12822 12823 12824 12825 12826 12827 12828 12829 12830 12831 12832 12833 12834 12835 12836 12837 12838 12839 12840 12841 12842 12843 12844 12845 12846 12847 12848 12849 12850 12851 12852 12853 12854 12855 12856 12857 12858 12859 12860 12861 12862 12863 12864 12865 12866 12867 12868 12869 12870 12871 12872 12873 12874 12875 12876 12877 12878 12879 12880 12881 12882 12883 12884 12885 12886 12887 12888 12889 12890 12891 12892 12893 12894 12895 12896 12897 12898 12899 12900 12901 12902 12903 12904 12905 12906 12907 12908 12909 12910 12911 12912 12913 12914 12915 12916 12917 12918 12919 12920 12921 12922 12923 12924 12925 12926 12927 12928 12929 12930 12931 12932 12933 12934 12935 12936 12937 12938 12939 12940 12941 12942 12943 12944 12945 12946 12947 12948 12949 12950 12951 12952 12953 12954 12955 12956 12957 12958 12959 12960 12961 12962 12963 12964 12965 12966 12967 12968 12969 12970 12971 12972 12973 12974 12975 12976 12977 12978 12979 12980 12981 12982 12983 12984 12985 12986 12987 12988 12989 12990 12991 12992 12993 12994 12995 12996 12997 12998 12999 13000 13001 13002 13003 13004 13005 13006 13007 13008 13009 13010 13011 13012 13013 13014 13015 13016 13017 13018 13019 13020 13021 13022 13023 13024 13025 13026 13027 13028 13029 13030 13031 13032 13033 13034 13035 13036 13037 13038 13039 13040 13041 13042 13043 13044 13045 13046 13047 13048 13049 13050 13051 13052 13053 13054 13055 13056 13057 13058 13059 13060 13061 13062 13063 13064 13065 13066 13067 13068 13069 13070 13071 13072 13073 13074 13075 13076 13077 13078 13079 13080 13081 13082 13083 13084 13085 13086 13087 13088 13089 13090 13091 13092 13093 13094 13095 13096 13097 13098 13099 13100 13101 13102 13103 13104 13105 13106 13107 13108 13109 13110 13111 13112 13113 13114 13115 13116 13117 13118 13119 13120 13121 13122 13123 13124 13125 13126 13127 13128 13129 13130 13131 13132 13133 13134 13135 13136 13137 13138 13139 13140 13141 13142 13143 13144 13145 13146 13147 13148 13149 13150 13151 13152 13153 13154 13155 13156 13157 13158 13159 13160 13161 13162 13163 13164 13165 13166 13167 13168 13169 13170 13171 13172 13173 13174 13175 13176 13177 13178 13179 13180 13181 13182 13183 13184 13185 13186 13187 13188 13189 13190 13191 13192 13193 13194 13195 13196 13197 13198 13199 13200 13201 13202 13203 13204 13205 13206 13207 13208 13209 13210 13211 13212 13213 13214 13215 13216 13217 13218 13219 13220 13221 13222 13223 13224 13225 13226 13227 13228 13229 13230 13231 13232 13233 13234 13235 13236 13237 13238 13239 13240 13241 13242 13243 13244 13245 13246 13247 13248 13249 13250 13251 13252 13253 13254 13255 13256 13257 13258 13259 13260 13261 13262 13263 13264 13265 13266 13267 13268 13269 13270 13271 13272 13273 13274 13275 13276 13277 13278 13279 13280 13281 13282 13283 13284 13285 13286 13287 13288 13289 13290 13291 13292 13293 13294 13295 13296 13297 13298 13299 13300 13301 13302 13303 13304 13305 13306 13307 13308 13309 13310 13311 13312 13313 13314 13315 13316 13317 13318 13319 13320 13321 13322 13323 13324 13325 13326 13327 13328 13329 13330 13331 13332 13333 13334 13335 13336 13337 13338 13339 13340 13341 13342 13343 13344 13345 13346 13347 13348 13349 13350 13351 13352 13353 13354 13355 13356 13357 13358 13359 13360 13361 13362 13363 13364 13365 13366 13367 13368 13369 13370 13371 13372 13373 13374 13375 13376 13377 13378 13379 13380 13381 13382 13383 13384 13385 13386 13387 13388 13389 13390 13391 13392 13393 13394 13395 13396 13397 13398 13399 13400 13401 13402 13403 13404 13405 13406 13407 13408 13409 13410 13411 13412 13413 13414 13415 13416 13417 13418 13419 13420 13421 13422 13423 13424 13425 13426 13427 13428 13429 13430 13431 13432 13433 13434 13435 13436 13437 13438 13439 13440 13441 13442 13443 13444 13445 13446 13447 13448 13449 13450 13451 13452 13453 13454 13455 13456 13457 13458 13459 13460 13461 13462 13463 13464 13465 13466 13467 13468 13469 13470 13471 13472 13473 13474 13475 13476 13477 13478 13479 13480 13481 13482 13483 13484 13485 13486 13487 13488 13489 13490 13491 13492 13493 13494 13495 13496 13497 13498 13499 13500 13501 13502 13503 13504 13505 13506 13507 13508 13509 13510 13511 13512 13513 13514 13515 13516 13517 13518 13519 13520 13521 13522 13523 13524 13525 13526 13527 13528 13529 13530 13531 13532 13533 13534 13535 13536 13537 13538 13539 13540 13541 13542 13543 13544 13545 13546 13547 13548 13549 13550 13551 13552 13553 13554 13555 13556 13557 13558 13559 13560 13561 13562 13563 13564 13565 13566 13567 13568 13569 13570 13571 13572 13573 13574 13575 13576 13577 13578 13579 13580 13581 13582 13583 13584 13585 13586 13587 13588 13589 13590 13591 13592 13593 13594 13595 13596 13597 13598 13599 13600 13601 13602 13603 13604 13605 13606 13607 13608 13609 13610 13611 13612 13613 13614 13615 13616 13617 13618 13619 13620 13621 13622 13623 13624 13625 13626 13627 13628 13629 13630 13631 13632 13633 13634 13635 13636 13637 13638 13639 13640 13641 13642 13643 13644 13645 13646 13647 13648 13649 13650 13651 13652 13653 13654 13655 13656 13657 13658 13659 13660 13661 13662 13663 13664 13665 13666 13667 13668 13669 13670 13671 13672 13673 13674 13675 13676 13677 13678 13679 13680 13681 13682 13683 13684 13685 13686 13687 13688 13689 13690 13691 13692 13693 13694 13695 13696 13697 13698 13699 13700 13701 13702 13703 13704 13705 13706 13707 13708 13709 13710 13711 13712 13713 13714 13715 13716 13717 13718 13719 13720 13721 13722 13723 13724 13725 13726 13727 13728 13729 13730 13731 13732 13733 13734 13735 13736 13737 13738 13739 13740 13741 13742 13743 13744 13745 13746 13747 13748 13749 13750 13751 13752 13753 13754 13755 13756 13757 13758 13759 13760 13761 13762 13763 13764 13765 13766 13767 13768 13769 13770 13771 13772 13773 13774 13775 13776 13777 13778 13779 13780 13781 13782 13783 13784 13785 13786 13787 13788 13789 13790 13791 13792 13793 13794 13795 13796 13797 13798 13799 13800 13801 13802 13803 13804 13805 13806 13807 13808 13809 13810 13811 13812 13813 13814 13815 13816 13817 13818 13819 13820 13821 13822 13823 13824 13825 13826 13827 13828 13829 13830 13831 13832 13833 13834 13835 13836 13837 13838 13839 13840 13841 13842 13843 13844 13845 13846 13847 13848 13849 13850 13851 13852 13853 13854 13855 13856 13857 13858 13859 13860 13861 13862 13863 13864 13865 13866 13867 13868 13869 13870 13871 13872 13873 13874 13875 13876 13877 13878 13879 13880 13881 13882 13883 13884 13885 13886 13887 13888 13889 13890 13891 13892 13893 13894 13895 13896 13897 13898 13899 13900 13901 13902 13903 13904 13905 13906 13907 13908 13909 13910 13911 13912 13913 13914 13915 13916 13917 13918 13919 13920 13921 13922 13923 13924 13925 13926 13927 13928 13929 13930 13931 13932 13933 13934 13935 13936 13937 13938 13939 13940 13941 13942 13943 13944 13945 13946 13947 13948 13949 13950 13951 13952 13953 13954 13955 13956 13957 13958 13959 13960 13961 13962 13963 13964 13965 13966 13967 13968 13969 13970 13971 13972 13973 13974 13975 13976 13977 13978 13979 13980 13981 13982 13983 13984 13985 13986 13987 13988 13989 13990 13991 13992 13993 13994 13995 13996 13997 13998 13999 14000 14001 14002 14003 14004 14005 14006 14007 14008 14009 14010 14011 14012 14013 14014 14015 14016 14017 14018 14019 14020 14021 14022 14023 14024 14025 14026 14027 14028 14029 14030 14031 14032 14033 14034 14035 14036 14037 14038 14039 14040 14041 14042 14043 14044 14045 14046 14047 14048 14049 14050 14051 14052 14053 14054 14055 14056 14057 14058 14059 14060 14061 14062 14063 14064 14065 14066 14067 14068 14069 14070 14071 14072 14073 14074 14075 14076 14077 14078 14079 14080 14081 14082 14083 14084 14085 14086 14087 14088 14089 14090 14091 14092 14093 14094 14095 14096 14097 14098 14099 14100 14101 14102 14103 14104 14105 14106 14107 14108 14109 14110 14111 14112 14113 14114 14115 14116 14117 14118 14119 14120 14121 14122 14123 14124 14125 14126 14127 14128 14129 14130 14131 14132 14133 14134 14135 14136 14137 14138 14139 14140 14141 14142 14143 14144 14145 14146 14147 14148 14149 14150 14151 14152 14153 14154 14155 14156 14157 14158 14159 14160 14161 14162 14163 14164 14165 14166 14167 14168 14169 14170 14171 14172 14173 14174 14175 14176 14177 14178 14179 14180 14181 14182 14183 14184 14185 14186 14187 14188 14189 14190 14191 14192 14193 14194 14195 14196 14197 14198 14199 14200 14201 14202 14203 14204 14205 14206 14207 14208 14209 14210 14211 14212 14213 14214 14215 14216 14217 14218 14219 14220 14221 14222 14223 14224 14225 14226 14227 14228 14229 14230 14231 14232 14233 14234 14235 14236 14237 14238 14239 14240 14241 14242 14243 14244 14245 14246 14247 14248 14249 14250 14251 14252 14253 14254 14255 14256 14257 14258 14259 14260 14261 14262 14263 14264 14265 14266 14267 14268 14269 14270 14271 14272 14273 14274 14275 14276 14277 14278 14279 14280 14281 14282 14283 14284 14285 14286 14287 14288 14289 14290 14291 14292 14293 14294 14295 14296 14297 14298 14299 14300 14301 14302 14303 14304 14305 14306 14307 14308 14309 14310 14311 14312 14313 14314 14315 14316 14317 14318 14319 14320 14321 14322 14323 14324 14325 14326 14327 14328 14329 14330 14331 14332 14333 14334 14335 14336 14337 14338 14339 14340 14341 14342 14343 14344 14345 14346 14347 14348 14349 14350 14351 14352 14353 14354 14355 14356 14357 14358 14359 14360 14361 14362 14363 14364 14365 14366 14367 14368 14369 14370 14371 14372 14373 14374 14375 14376 14377 14378 14379 14380 14381 14382 14383 14384 14385 14386 14387 14388 14389 14390 14391 14392 14393 14394 14395 14396 14397 14398 14399 14400 14401 14402 14403 14404 14405 14406 14407 14408 14409 14410 14411 14412 14413 14414 14415 14416 14417 14418 14419 14420 14421 14422 14423 14424 14425 14426 14427 14428 14429 14430 14431 14432 14433 14434 14435 14436 14437 14438 14439 14440 14441 14442 14443 14444 14445 14446 14447 14448 14449 14450 14451 14452 14453 14454 14455 14456 14457 14458 14459 14460 14461 14462 14463 14464 14465 14466 14467 14468 14469 14470 14471 14472 14473 14474 14475 14476 14477 14478 14479 14480 14481 14482 14483 14484 14485 14486 14487 14488 14489 14490 14491 14492 14493 14494 14495 14496 14497 14498 14499 14500 14501 14502 14503 14504 14505 14506 14507 14508 14509 14510 14511 14512 14513 14514 14515 14516 14517 14518 14519 14520 14521 14522 14523 14524 14525 14526 14527 14528 14529 14530 14531 14532 14533 14534 14535 14536 14537 14538 14539 14540 14541 14542 14543 14544 14545 14546 14547 14548 14549 14550 14551 14552 14553 14554 14555 14556 14557 14558 14559 14560 14561 14562 14563 14564 14565 14566 14567 14568 14569 14570 14571 14572 14573 14574 14575 14576 14577 14578 14579 14580 14581 14582 14583 14584 14585 14586 14587 14588 14589 14590 14591 14592 14593 14594 14595 14596 14597 14598 14599 14600 14601 14602 14603 14604 14605 14606 14607 14608 14609 14610 14611 14612 14613 14614 14615 14616 14617 14618 14619 14620 14621 14622 14623 14624 14625 14626 14627 14628 14629 14630 14631 14632 14633 14634 14635 14636 14637 14638 14639 14640 14641 14642 14643 14644 14645 14646 14647 14648 14649 14650 14651 14652 14653 14654 14655 14656 14657 14658 14659 14660 14661 14662 14663 14664 14665 14666 14667 14668 14669 14670 14671 14672 14673 14674 14675 14676 14677 14678 14679 14680 14681 14682 14683 14684 14685 14686 14687 14688 14689 14690 14691 14692 14693 14694 14695 14696 14697 14698 14699 14700 14701 14702 14703 14704 14705 14706 14707 14708 14709 14710 14711 14712 14713 14714 14715 14716 14717 14718 14719 14720 14721 14722 14723 14724 14725 14726 14727 14728 14729 14730 14731 14732 14733 14734 14735 14736 14737 14738 14739 14740 14741 14742 14743 14744 14745 14746 14747 14748 14749 14750 14751 14752 14753 14754 14755 14756 14757 14758 14759 14760 14761 14762 14763 14764 14765 14766 14767 14768 14769 14770 14771 14772 14773 14774 14775 14776 14777 14778 14779 14780 14781 14782 14783 14784 14785 14786 14787 14788 14789 14790 14791 14792 14793 14794 14795 14796 14797 14798 14799 14800 14801 14802 14803 14804 14805 14806 14807 14808 14809 14810 14811 14812 14813 14814 14815 14816 14817 14818 14819 14820 14821 14822 14823 14824 14825 14826 14827 14828 14829 14830 14831 14832 14833 14834 14835 14836 14837 14838 14839 14840 14841 14842 14843 14844 14845 14846 14847 14848 14849 14850 14851 14852 14853 14854 14855 14856 14857 14858 14859 14860 14861 14862 14863 14864 14865 14866 14867 14868 14869 14870 14871 14872 14873 14874 14875 14876 14877 14878 14879 14880 14881 14882 14883 14884 14885 14886 14887 14888 14889 14890 14891 14892 14893 14894 14895 14896 14897 14898 14899 14900 14901 14902 14903 14904 14905 14906 14907 14908 14909 14910 14911 14912 14913 14914 14915 14916 14917 14918 14919 14920 14921 14922 14923 14924 14925 14926 14927 14928 14929 14930 14931 14932 14933 14934 14935 14936 14937 14938 14939 14940 14941 14942 14943 14944 14945 14946 14947 14948 14949 14950 14951 14952 14953 14954 14955 14956 14957 14958 14959 14960 14961 14962 14963 14964 14965 14966 14967 14968 14969 14970 14971 14972 14973 14974 14975 14976 14977 14978 14979 14980 14981 14982 14983 14984 14985 14986 14987 14988 14989 14990 14991 14992 14993 14994 14995 14996 14997 14998 14999 15000 15001 15002 15003 15004 15005 15006 15007 15008 15009 15010 15011 15012 15013 15014 15015 15016 15017 15018 15019 15020 15021 15022 15023 15024 15025 15026 15027 15028 15029 15030 15031 15032 15033 15034 15035 15036 15037 15038 15039 15040 15041 15042 15043 15044 15045 15046 15047 15048 15049 15050 15051 15052 15053 15054 15055 15056 15057 15058 15059 15060 15061 15062 15063 15064 15065 15066 15067 15068 15069 15070 15071 15072 15073 15074 15075 15076 15077 15078 15079 15080 15081 15082 15083 15084 15085 15086 15087 15088 15089 15090 15091 15092 15093 15094 15095 15096 15097 15098 15099 15100 15101 15102 15103 15104 15105 15106 15107 15108 15109 15110 15111 15112 15113 15114 15115 15116 15117 15118 15119 15120 15121 15122 15123 15124 15125 15126 15127 15128 15129 15130 15131 15132 15133 15134 15135 15136 15137 15138 15139 15140 15141 15142 15143 15144 15145 15146 15147 15148 15149 15150 15151 15152 15153 15154 15155 15156 15157 15158 15159 15160 15161 15162 15163 15164 15165 15166 15167 15168 15169 15170 15171 15172 15173 15174 15175 15176 15177 15178 15179 15180 15181 15182 15183 15184 15185 15186 15187 15188 15189 15190 15191 15192 15193 15194 15195 15196 15197 15198 15199 15200 15201 15202 15203 15204 15205 15206 15207 15208 15209 15210 15211 15212 15213 15214 15215 15216 15217 15218 15219 15220 15221 15222 15223 15224 15225 15226 15227 15228 15229 15230 15231 15232 15233 15234 15235 15236 15237 15238 15239 15240 15241 15242 15243 15244 15245 15246 15247 15248 15249 15250 15251 15252 15253 15254 15255 15256 15257 15258 15259 15260 15261 15262 15263 15264 15265 15266 15267 15268 15269 15270 15271 15272 15273 15274 15275 15276 15277 15278 15279 15280 15281 15282 15283 15284 15285 15286 15287 15288 15289 15290 15291 15292 15293 15294 15295 15296 15297 15298 15299 15300 15301 15302 15303 15304 15305 15306 15307 15308 15309 15310 15311 15312 15313 15314 15315 15316 15317 15318 15319 15320 15321 15322 15323 15324 15325 15326 15327 15328 15329 15330 15331 15332 15333 15334 15335 15336 15337 15338 15339 15340 15341 15342 15343 15344 15345 15346 15347 15348 15349 15350 15351 15352 15353 15354 15355 15356 15357 15358 15359 15360 15361 15362 15363 15364 15365 15366 15367 15368 15369 15370 15371 15372 15373 15374 15375 15376 15377 15378 15379 15380 15381 15382 15383 15384 15385 15386 15387 15388 15389 15390 15391 15392 15393 15394 15395 15396 15397 15398 15399 15400 15401 15402 15403 15404 15405 15406 15407 15408 15409 15410 15411 15412 15413 15414 15415 15416 15417 15418 15419 15420 15421 15422 15423 15424 15425 15426 15427 15428 15429 15430 15431 15432 15433 15434 15435 15436 15437 15438 15439 15440 15441 15442 15443 15444 15445 15446 15447 15448 15449 15450 15451 15452 15453 15454 15455 15456 15457 15458 15459 15460 15461 15462 15463 15464 15465 15466 15467 15468 15469 15470 15471 15472 15473 15474 15475 15476 15477 15478 15479 15480 15481 15482 15483 15484 15485 15486 15487 15488 15489 15490 15491 15492 15493 15494 15495 15496 15497 15498 15499 15500 15501 15502 15503 15504 15505 15506 15507 15508 15509 15510 15511 15512 15513 15514 15515 15516 15517 15518 15519 15520 15521 15522 15523 15524 15525 15526 15527 15528 15529 15530 15531 15532 15533 15534 15535 15536 15537 15538 15539 15540 15541 15542 15543 15544 15545 15546 15547 15548 15549 15550 15551 15552 15553 15554 15555 15556 15557 15558 15559 15560 15561 15562 15563 15564 15565 15566 15567 15568 15569 15570 15571 15572 15573 15574 15575 15576 15577 15578 15579 15580 15581 15582 15583 15584 15585 15586 15587 15588 15589 15590 15591 15592 15593 15594 15595 15596 15597 15598 15599 15600 15601 15602 15603 15604 15605 15606 15607 15608 15609 15610 15611 15612 15613 15614 15615 15616 15617 15618 15619 15620 15621 15622 15623 15624 15625 15626 15627 15628 15629 15630 15631 15632 15633 15634 15635 15636 15637 15638 15639 15640 15641 15642 15643 15644 15645 15646 15647 15648 15649 15650 15651 15652 15653 15654 15655 15656 15657 15658 15659 15660 15661 15662 15663 15664 15665 15666 15667 15668 15669 15670 15671 15672 15673 15674 15675 15676 15677 15678 15679 15680 15681 15682 15683 15684 15685 15686 15687 15688 15689 15690 15691 15692 15693 15694 15695 15696 15697 15698 15699 15700 15701 15702 15703 15704 15705 15706 15707 15708 15709 15710 15711 15712 15713 15714 15715 15716 15717 15718 15719 15720 15721 15722 15723 15724 15725 15726 15727 15728 15729 15730 15731 15732 15733 15734 15735 15736 15737 15738 15739 15740 15741 15742 15743 15744 15745 15746 15747 15748 15749 15750 15751 15752 15753 15754 15755 15756 15757 15758 15759 15760 15761 15762 15763 15764 15765 15766 15767 15768 15769 15770 15771 15772 15773 15774 15775 15776 15777 15778 15779 15780 15781 15782 15783 15784 15785 15786 15787 15788 15789 15790 15791 15792 15793 15794 15795 15796 15797 15798 15799 15800 15801 15802 15803 15804 15805 15806 15807 15808 15809 15810 15811 15812 15813 15814 15815 15816 15817 15818 15819 15820 15821 15822 15823 15824 15825 15826 15827 15828 15829 15830 15831 15832 15833 15834 15835 15836 15837 15838 15839 15840 15841 15842 15843 15844 15845 15846 15847 15848 15849 15850 15851 15852 15853 15854 15855 15856 15857 15858 15859 15860 15861 15862 15863 15864 15865 15866 15867 15868 15869 15870 15871 15872 15873 15874 15875 15876 15877 15878 15879 15880 15881 15882 15883 15884 15885 15886 15887 15888 15889 15890 15891 15892 15893 15894 15895 15896 15897 15898 15899 15900 15901 15902 15903 15904 15905 15906 15907 15908 15909 15910 15911 15912 15913 15914 15915 15916 15917 15918 15919 15920 15921 15922 15923 15924 15925 15926 15927 15928 15929 15930 15931 15932 15933 15934 15935 15936 15937 15938 15939 15940 15941 15942 15943 15944 15945 15946 15947 15948 15949 15950 15951 15952 15953 15954 15955 15956 15957 15958 15959 15960 15961 15962 15963 15964 15965 15966 15967 15968 15969 15970 15971 15972 15973 15974 15975 15976 15977 15978 15979 15980 15981 15982 15983 15984 15985 15986 15987 15988 15989 15990 15991 15992 15993 15994 15995 15996 15997 15998 15999 16000 16001 16002 16003 16004 16005 16006 16007 16008 16009 16010 16011 16012 16013 16014 16015 16016 16017 16018 16019 16020 16021 16022 16023 16024 16025 16026 16027 16028 16029 16030 16031 16032 16033 16034 16035 16036 16037 16038 16039 16040 16041 16042 16043 16044 16045 16046 16047 16048 16049 16050 16051 16052 16053 16054 16055 16056 16057 16058 16059 16060 16061 16062 16063 16064 16065 16066 16067 16068 16069 16070 16071 16072 16073 16074 16075 16076 16077 16078 16079 16080 16081 16082 16083 16084 16085 16086 16087 16088 16089 16090 16091 16092 16093 16094 16095 16096 16097 16098 16099 16100 16101 16102 16103 16104 16105 16106 16107 16108 16109 16110 16111 16112 16113 16114 16115 16116 16117 16118 16119 16120 16121 16122 16123 16124 16125 16126 16127 16128 16129 16130 16131 16132 16133 16134 16135 16136 16137 16138 16139 16140 16141 16142 16143 16144 16145 16146 16147 16148 16149 16150 16151 16152 16153 16154 16155 16156 16157 16158 16159 16160 16161 16162 16163 16164 16165 16166 16167 16168 16169 16170 16171 16172 16173 16174 16175 16176 16177 16178 16179 16180 16181 16182 16183 16184 16185 16186 16187 16188 16189 16190 16191 16192 16193 16194 16195 16196 16197 16198 16199 16200 16201 16202 16203 16204 16205 16206 16207 16208 16209 16210 16211 16212 16213 16214 16215 16216 16217 16218 16219 16220 16221 16222 16223 16224 16225 16226 16227 16228 16229 16230 16231 16232 16233 16234 16235 16236 16237 16238 16239 16240 16241 16242 16243 16244 16245 16246 16247 16248 16249 16250 16251 16252 16253 16254 16255 16256 16257 16258 16259 16260 16261 16262 16263 16264 16265 16266 16267 16268 16269 16270 16271 16272 16273 16274 16275 16276 16277 16278 16279 16280 16281 16282 16283 16284 16285 16286 16287 16288 16289 16290 16291 16292 16293 16294 16295 16296 16297 16298 16299 16300 16301 16302 16303 16304 16305 16306 16307 16308 16309 16310 16311 16312 16313 16314 16315 16316 16317 16318 16319 16320 16321 16322 16323 16324 16325 16326 16327 16328 16329 16330 16331 16332 16333 16334 16335 16336 16337 16338 16339 16340 16341 16342 16343 16344 16345 16346 16347 16348 16349 16350 16351 16352 16353 16354 16355 16356 16357 16358 16359 16360 16361 16362 16363 16364 16365 16366 16367 16368 16369 16370 16371 16372 16373 16374 16375 16376 16377 16378 16379 16380 16381 16382 16383 16384 16385 16386 16387 16388 16389 16390 16391 16392 16393 16394 16395 16396 16397 16398 16399 16400 16401 16402 16403 16404 16405 16406 16407 16408 16409 16410 16411 16412 16413 16414 16415 16416 16417 16418 16419 16420 16421 16422 16423 16424 16425 16426 16427 16428 16429 16430 16431 16432 16433 16434 16435 16436 16437 16438 16439 16440 16441 16442 16443 16444 16445 16446 16447 16448 16449 16450 16451 16452 16453 16454 16455 16456 16457 16458 16459 16460 16461 16462 16463 16464 16465 16466 16467 16468 16469 16470 16471 16472 16473 16474 16475 16476 16477 16478 16479 16480 16481 16482 16483 16484 16485 16486 16487 16488 16489 16490 16491 16492 16493 16494 16495 16496 16497 16498 16499 16500 16501 16502 16503 16504 16505 16506 16507 16508 16509 16510 16511 16512 16513 16514 16515 16516 16517 16518 16519 16520 16521 16522 16523 16524 16525 16526 16527 16528 16529 16530 16531 16532 16533 16534 16535 16536 16537 16538 16539 16540 16541 16542 16543 16544 16545 16546 16547 16548 16549 16550 16551 16552 16553 16554 16555 16556 16557 16558 16559 16560 16561 16562 16563 16564 16565 16566 16567 16568 16569 16570 16571 16572 16573 16574 16575 16576 16577 16578 16579 16580 16581 16582 16583 16584 16585 16586 16587 16588 16589 16590 16591 16592 16593 16594 16595 16596 16597 16598 16599 16600 16601 16602 16603 16604 16605 16606 16607 16608 16609 16610 16611 16612 16613 16614 16615 16616 16617 16618 16619 16620 16621 16622 16623 16624 16625 16626 16627 16628 16629 16630 16631 16632 16633 16634 16635 16636 16637 16638 16639 16640 16641 16642 16643 16644 16645 16646 16647 16648 16649 16650 16651 16652 16653 16654 16655 16656 16657 16658 16659 16660 16661 16662 16663 16664 16665 16666 16667 16668 16669 16670 16671 16672 16673 16674 16675 16676 16677 16678 16679 16680 16681 16682 16683 16684 16685 16686 16687 16688 16689 16690 16691 16692 16693 16694 16695 16696 16697 16698 16699 16700 16701 16702 16703 16704 16705 16706 16707 16708 16709 16710 16711 16712 16713 16714 16715 16716 16717 16718 16719 16720 16721 16722 16723 16724 16725 16726 16727 16728 16729 16730 16731 16732 16733 16734 16735 16736 16737 16738 16739 16740 16741 16742 16743 16744 16745 16746 16747 16748 16749 16750 16751 16752 16753 16754 16755 16756 16757 16758 16759 16760 16761 16762 16763 16764 16765 16766 16767 16768 16769 16770 16771 16772 16773 16774 16775 16776 16777 16778 16779 16780 16781 16782 16783 16784 16785 16786 16787 16788 16789 16790 16791 16792 16793 16794 16795 16796 16797 16798 16799 16800 16801 16802 16803 16804 16805 16806 16807 16808 16809 16810 16811 16812 16813 16814 16815 16816 16817 16818 16819 16820 16821 16822 16823 16824 16825 16826 16827 16828 16829 16830 16831 16832 16833 16834 16835 16836 16837 16838 16839 16840 16841 16842 16843 16844 16845 16846 16847 16848 16849 16850 16851 16852 16853 16854 16855 16856 16857 16858 16859 16860 16861 16862 16863 16864 16865 16866 16867 16868 16869 16870 16871 16872 16873 16874 16875 16876 16877 16878 16879 16880 16881 16882 16883 16884 16885 16886 16887 16888 16889 16890 16891 16892 16893 16894 16895 16896 16897 16898 16899 16900 16901 16902 16903 16904 16905 16906 16907 16908 16909 16910 16911 16912 16913 16914 16915 16916 16917 16918 16919 16920 16921 16922 16923 16924 16925 16926 16927 16928 16929 16930 16931 16932 16933 16934 16935 16936 16937 16938 16939 16940 16941 16942 16943 16944 16945 16946 16947 16948 16949 16950 16951 16952 16953 16954 16955 16956 16957 16958 16959 16960 16961 16962 16963 16964 16965 16966 16967 16968 16969 16970 16971 16972 16973 16974 16975 16976 16977 16978 16979 16980 16981 16982 16983 16984 16985 16986 16987 16988 16989 16990 16991 16992 16993 16994 16995 16996 16997 16998 16999 17000 17001 17002 17003 17004 17005 17006 17007 17008 17009 17010 17011 17012 17013 17014 17015 17016 17017 17018 17019 17020 17021 17022 17023 17024 17025 17026 17027 17028 17029 17030 17031 17032 17033 17034 17035 17036 17037 17038 17039 17040 17041 17042 17043 17044 17045 17046 17047 17048 17049 17050 17051 17052 17053 17054 17055 17056 17057 17058 17059 17060 17061 17062 17063 17064 17065 17066 17067 17068 17069 17070 17071 17072 17073 17074 17075 17076 17077 17078 17079 17080 17081 17082 17083 17084 17085 17086 17087 17088 17089 17090 17091 17092 17093 17094 17095 17096 17097 17098 17099 17100 17101 17102 17103 17104 17105 17106 17107 17108 17109 17110 17111 17112 17113 17114 17115 17116 17117 17118 17119 17120 17121 17122 17123 17124 17125 17126 17127 17128 17129 17130 17131 17132 17133 17134 17135 17136 17137 17138 17139 17140 17141 17142 17143 17144 17145 17146 17147 17148 17149 17150 17151 17152 17153 17154 17155 17156 17157 17158 17159 17160 17161 17162 17163 17164 17165 17166 17167 17168 17169 17170 17171 17172 17173 17174 17175 17176 17177 17178 17179 17180 17181 17182 17183 17184 17185 17186 17187 17188 17189 17190 17191 17192 17193 17194 17195 17196 17197 17198 17199 17200 17201 17202 17203 17204 17205 17206 17207 17208 17209 17210 17211 17212 17213 17214 17215 17216 17217 17218 17219 17220 17221 17222 17223 17224 17225 17226 17227 17228 17229 17230 17231 17232 17233 17234 17235 17236 17237 17238 17239 17240 17241 17242 17243 17244 17245 17246 17247 17248 17249 17250 17251 17252 17253 17254 17255 17256 17257 17258 17259 17260 17261 17262 17263 17264 17265 17266 17267 17268 17269 17270 17271 17272 17273 17274 17275 17276 17277 17278 17279 17280 17281 17282 17283 17284 17285 17286 17287 17288 17289 17290 17291 17292 17293 17294 17295 17296 17297 17298 17299 17300 17301 17302 17303 17304 17305 17306 17307 17308 17309 17310 17311 17312 17313 17314 17315 17316 17317 17318 17319 17320 17321 17322 17323 17324 17325 17326 17327 17328 17329 17330 17331 17332 17333 17334 17335 17336 17337 17338 17339 17340 17341 17342 17343 17344 17345 17346 17347 17348 17349 17350 17351 17352 17353 17354 17355 17356 17357 17358 17359 17360 17361 17362 17363 17364 17365 17366 17367 17368 17369 17370 17371 17372 17373 17374 17375 17376 17377 17378 17379 17380 17381 17382 17383 17384 17385 17386 17387 17388 17389 17390 17391 17392 17393 17394 17395 17396 17397 17398 17399 17400 17401 17402 17403 17404 17405 17406 17407 17408 17409 17410 17411 17412 17413 17414 17415 17416 17417 17418 17419 17420 17421 17422 17423 17424 17425 17426 17427 17428 17429 17430 17431 17432 17433 17434 17435 17436 17437 17438 17439 17440 17441 17442 17443 17444 17445 17446 17447 17448 17449 17450 17451 17452 17453 17454 17455 17456 17457 17458 17459 17460 17461 17462 17463 17464 17465 17466 17467 17468 17469 17470 17471 17472 17473 17474 17475 17476 17477 17478 17479 17480 17481 17482 17483 17484 17485 17486 17487 17488 17489 17490 17491 17492 17493 17494 17495 17496 17497 17498 17499 17500 17501 17502 17503 17504 17505 17506 17507 17508 17509 17510 17511 17512 17513 17514 17515 17516 17517 17518 17519 17520 17521 17522 17523 17524 17525 17526 17527 17528 17529 17530 17531 17532 17533 17534 17535 17536 17537 17538 17539 17540 17541 17542 17543 17544 17545 17546 17547 17548 17549 17550 17551 17552 17553 17554 17555 17556 17557 17558 17559 17560 17561 17562 17563 17564 17565 17566 17567 17568 17569 17570 17571 17572 17573 17574 17575 17576 17577 17578 17579 17580 17581 17582 17583 17584 17585 17586 17587 17588 17589 17590 17591 17592 17593 17594 17595 17596 17597 17598 17599 17600 17601 17602 17603 17604 17605 17606 17607 17608 17609 17610 17611 17612 17613 17614 17615 17616 17617 17618 17619 17620 17621 17622 17623 17624 17625 17626 17627 17628 17629 17630 17631 17632 17633 17634 17635 17636 17637 17638 17639 17640 17641 17642 17643 17644 17645 17646 17647 17648 17649 17650 17651 17652 17653 17654 17655 17656 17657 17658 17659 17660 17661 17662 17663 17664 17665 17666 17667 17668 17669 17670 17671 17672 17673 17674 17675 17676 17677 17678 17679 17680 17681 17682 17683 17684 17685 17686 17687 17688 17689 17690 17691 17692 17693 17694 17695 17696 17697 17698 17699 17700 17701 17702 17703 17704 17705 17706 17707 17708 17709 17710 17711 17712 17713 17714 17715 17716 17717 17718 17719 17720 17721 17722 17723 17724 17725 17726 17727 17728 17729 17730 17731 17732 17733 17734 17735 17736 17737 17738 17739 17740 17741 17742 17743 17744 17745 17746 17747 17748 17749 17750 17751 17752 17753 17754 17755 17756 17757 17758 17759 17760 17761 17762 17763 17764 17765 17766 17767 17768 17769 17770 17771 17772 17773 17774 17775 17776 17777 17778 17779 17780 17781 17782 17783 17784 17785 17786 17787 17788 17789 17790 17791 17792 17793 17794 17795 17796 17797 17798 17799 17800 17801 17802 17803 17804 17805 17806 17807 17808 17809 17810 17811 17812 17813 17814 17815 17816 17817 17818 17819 17820 17821 17822 17823 17824 17825 17826 17827 17828 17829 17830 17831 17832 17833 17834 17835 17836 17837 17838 17839 17840 17841 17842 17843 17844 17845 17846 17847 17848 17849 17850 17851 17852 17853 17854 17855 17856 17857 17858 17859 17860 17861 17862 17863 17864 17865 17866 17867 17868 17869 17870 17871 17872 17873 17874 17875 17876 17877 17878 17879 17880 17881 17882 17883 17884 17885 17886 17887 17888 17889 17890 17891 17892 17893 17894 17895 17896 17897 17898 17899 17900 17901 17902 17903 17904 17905 17906 17907 17908 17909 17910 17911 17912 17913 17914 17915 17916 17917 17918 17919 17920 17921 17922 17923 17924 17925 17926 17927 17928 17929 17930 17931 17932 17933 17934 17935 17936 17937 17938 17939 17940 17941 17942 17943 17944 17945 17946 17947 17948 17949 17950 17951 17952 17953 17954 17955 17956 17957 17958 17959 17960 17961 17962 17963 17964 17965 17966 17967 17968 17969 17970 17971 17972 17973 17974 17975 17976 17977 17978 17979 17980 17981 17982 17983 17984 17985 17986 17987 17988 17989 17990 17991 17992 17993 17994 17995 17996 17997 17998 17999 18000 18001 18002 18003 18004 18005 18006 18007 18008 18009 18010 18011 18012 18013 18014 18015 18016 18017 18018 18019 18020 18021 18022 18023 18024 18025 18026 18027 18028 18029 18030 18031 18032 18033 18034 18035 18036 18037 18038 18039 18040 18041 18042 18043 18044 18045 18046 18047 18048 18049 18050 18051 18052 18053 18054 18055 18056 18057 18058 18059 18060 18061 18062 18063 18064 18065 18066 18067 18068 18069 18070 18071 18072 18073 18074 18075 18076 18077 18078 18079 18080 18081 18082 18083 18084 18085 18086 18087 18088 18089 18090 18091 18092 18093 18094 18095 18096 18097 18098 18099 18100 18101 18102 18103 18104 18105 18106 18107 18108 18109 18110 18111 18112 18113 18114 18115 18116 18117 18118 18119 18120 18121 18122 18123 18124 18125 18126 18127 18128 18129 18130 18131 18132 18133 18134 18135 18136 18137 18138 18139 18140 18141 18142 18143 18144 18145 18146 18147 18148 18149 18150 18151 18152 18153 18154 18155 18156 18157 18158 18159 18160 18161 18162 18163 18164 18165 18166 18167 18168 18169 18170 18171 18172 18173 18174 18175 18176 18177 18178 18179 18180 18181 18182 18183 18184 18185 18186 18187 18188 18189 18190 18191 18192 18193 18194 18195 18196 18197 18198 18199 18200 18201 18202 18203 18204 18205 18206 18207 18208 18209 18210 18211 18212 18213 18214 18215 18216 18217 18218 18219 18220 18221 18222 18223 18224 18225 18226 18227 18228 18229 18230 18231 18232 18233 18234 18235 18236 18237 18238 18239 18240 18241 18242 18243 18244 18245 18246 18247 18248 18249 18250 18251 18252 18253 18254 18255 18256 18257 18258 18259 18260 18261 18262 18263 18264 18265 18266 18267 18268 18269 18270 18271 18272 18273 18274 18275 18276 18277 18278 18279 18280 18281 18282 18283 18284 18285 18286 18287 18288 18289 18290 18291 18292 18293 18294 18295 18296 18297 18298 18299 18300 18301 18302 18303 18304 18305 18306 18307 18308 18309 18310 18311 18312 18313 18314 18315 18316 18317 18318 18319 18320 18321 18322 18323 18324 18325 18326 18327 18328 18329 18330 18331 18332 18333 18334 18335 18336 18337 18338 18339 18340 18341 18342 18343 18344 18345 18346 18347 18348 18349 18350 18351 18352 18353 18354 18355 18356 18357 18358 18359 18360 18361 18362 18363 18364 18365 18366 18367 18368 18369 18370 18371 18372 18373 18374 18375 18376 18377 18378 18379 18380 18381 18382 18383 18384 18385 18386 18387 18388 18389 18390 18391 18392 18393 18394 18395 18396 18397 18398 18399 18400 18401 18402 18403 18404 18405 18406 18407 18408 18409 18410 18411 18412 18413 18414 18415 18416 18417 18418 18419 18420 18421 18422 18423 18424 18425 18426 18427 18428 18429 18430 18431 18432 18433 18434 18435 18436 18437 18438 18439 18440 18441 18442 18443 18444 18445 18446 18447 18448 18449 18450 18451 18452 18453 18454 18455 18456 18457 18458 18459 18460 18461 18462 18463 18464 18465 18466 18467 18468 18469 18470 18471 18472 18473 18474 18475 18476 18477 18478 18479 18480 18481 18482 18483 18484 18485 18486 18487 18488 18489 18490 18491 18492 18493 18494 18495 18496 18497 18498 18499 18500 18501 18502 18503 18504 18505 18506 18507 18508 18509 18510 18511 18512 18513 18514 18515 18516 18517 18518 18519 18520 18521 18522 18523 18524 18525 18526 18527 18528 18529 18530 18531 18532 18533 18534 18535 18536 18537 18538 18539 18540 18541 18542 18543 18544 18545 18546 18547 18548 18549 18550 18551 18552 18553 18554 18555 18556 18557 18558 18559 18560 18561 18562 18563 18564 18565 18566 18567 18568 18569 18570 18571 18572 18573 18574 18575 18576 18577 18578 18579 18580 18581 18582 18583 18584 18585 18586 18587 18588 18589 18590 18591 18592 18593 18594 18595 18596 18597 18598 18599 18600 18601 18602 18603 18604 18605 18606 18607 18608 18609 18610 18611 18612 18613 18614 18615 18616 18617 18618 18619 18620 18621 18622 18623 18624 18625 18626 18627 18628 18629 18630 18631 18632 18633 18634 18635 18636 18637 18638 18639 18640 18641 18642 18643 18644 18645 18646 18647 18648 18649 18650 18651 18652 18653 18654 18655 18656 18657 18658 18659 18660 18661 18662 18663 18664 18665 18666 18667 18668 18669 18670 18671 18672 18673 18674 18675 18676 18677 18678 18679 18680 18681 18682 18683 18684 18685 18686 18687 18688 18689 18690 18691 18692 18693 18694 18695 18696 18697 18698 18699 18700 18701 18702 18703 18704 18705 18706 18707 18708 18709 18710 18711 18712 18713 18714 18715 18716 18717 18718 18719 18720 18721 18722 18723 18724 18725 18726 18727 18728 18729 18730 18731 18732 18733 18734 18735 18736 18737 18738 18739 18740 18741 18742 18743 18744 18745 18746 18747 18748 18749 18750 18751 18752 18753 18754 18755 18756 18757 18758 18759 18760 18761 18762 18763 18764 18765 18766 18767 18768 18769 18770 18771 18772 18773 18774 18775 18776 18777 18778 18779 18780 18781 18782 18783 18784 18785 18786 18787 18788 18789 18790 18791 18792 18793 18794 18795 18796 18797 18798 18799 18800 18801 18802 18803 18804 18805 18806 18807 18808 18809 18810 18811 18812 18813 18814 18815 18816 18817 18818 18819 18820 18821 18822 18823 18824 18825 18826 18827 18828 18829 18830 18831 18832 18833 18834 18835 18836 18837 18838 18839 18840 18841 18842 18843 18844 18845 18846 18847 18848 18849 18850 18851 18852 18853 18854 18855 18856 18857 18858 18859 18860 18861 18862 18863 18864 18865 18866 18867 18868 18869 18870 18871 18872 18873 18874 18875 18876 18877 18878 18879 18880 18881 18882 18883 18884 18885 18886 18887 18888 18889 18890 18891 18892 18893 18894 18895 18896 18897 18898 18899 18900 18901 18902 18903 18904 18905 18906 18907 18908 18909 18910 18911 18912 18913 18914 18915 18916 18917 18918 18919 18920 18921 18922 18923 18924 18925 18926 18927 18928 18929 18930 18931 18932 18933 18934 18935 18936 18937 18938 18939 18940 18941 18942 18943 18944 18945 18946 18947 18948 18949 18950 18951 18952 18953 18954 18955 18956 18957 18958 18959 18960 18961 18962 18963 18964 18965 18966 18967 18968 18969 18970 18971 18972 18973 18974 18975 18976 18977 18978 18979 18980 18981 18982 18983 18984 18985 18986 18987 18988 18989 18990 18991 18992 18993 18994 18995 18996 18997 18998 18999 19000 19001 19002 19003 19004 19005 19006 19007 19008 19009 19010 19011 19012 19013 19014 19015 19016 19017 19018 19019 19020 19021 19022 19023 19024 19025 19026 19027 19028 19029 19030 19031 19032 19033 19034 19035 19036 19037 19038 19039 19040 19041 19042 19043 19044 19045 19046 19047 19048 19049 19050 19051 19052 19053 19054 19055 19056 19057 19058 19059 19060 19061 19062 19063 19064 19065 19066 19067 19068 19069 19070 19071 19072 19073 19074 19075 19076 19077 19078 19079 19080 19081 19082 19083 19084 19085 19086 19087 19088 19089 19090 19091 19092 19093 19094 19095 19096 19097 19098 19099 19100 19101 19102 19103 19104 19105 19106 19107 19108 19109 19110 19111 19112 19113 19114 19115 19116 19117 19118 19119 19120 19121 19122 19123 19124 19125 19126 19127 19128 19129 19130 19131 19132 19133 19134 19135 19136 19137 19138 19139 19140 19141 19142 19143 19144 19145 19146 19147 19148 19149 19150 19151 19152 19153 19154 19155 19156 19157 19158 19159 19160 19161 19162 19163 19164 19165 19166 19167 19168 19169 19170 19171 19172 19173 19174 19175 19176 19177 19178 19179 19180 19181 19182 19183 19184 19185 19186 19187 19188 19189 19190 19191 19192 19193 19194 19195 19196 19197 19198 19199 19200 19201 19202 19203 19204 19205 19206 19207 19208 19209 19210 19211 19212 19213 19214 19215 19216 19217 19218 19219 19220 19221 19222 19223 19224 19225 19226 19227 19228 19229 19230 19231 19232 19233 19234 19235 19236 19237 19238 19239 19240 19241 19242 19243 19244 19245 19246 19247 19248 19249 19250 19251 19252 19253 19254 19255 19256 19257 19258 19259 19260 19261 19262 19263 19264 19265 19266 19267 19268 19269 19270 19271 19272 19273 19274 19275 19276 19277 19278 19279 19280 19281 19282 19283 19284 19285 19286 19287 19288 19289 19290 19291 19292 19293 19294 19295 19296 19297 19298 19299 19300 19301 19302 19303 19304 19305 19306 19307 19308 19309 19310 19311 19312 19313 19314 19315 19316 19317 19318 19319 19320 19321 19322 19323 19324 19325 19326 19327 19328 19329 19330 19331 19332 19333 19334 19335 19336 19337 19338 19339 19340 19341 19342 19343 19344 19345 19346 19347 19348 19349 19350 19351 19352 19353 19354 19355 19356 19357 19358 19359 19360 19361 19362 19363 19364 19365 19366 19367 19368 19369 19370 19371 19372 19373 19374 19375 19376 19377 19378 19379 19380 19381 19382 19383 19384 19385 19386 19387 19388 19389 19390 19391 19392 19393 19394 19395 19396 19397 19398 19399 19400 19401 19402 19403 19404 19405 19406 19407 19408 19409 19410 19411 19412 19413 19414 19415 19416 19417 19418 19419 19420 19421 19422 19423 19424 19425 19426 19427 19428 19429 19430 19431 19432 19433 19434 19435 19436 19437 19438 19439 19440 19441 19442 19443 19444 19445 19446 19447 19448 19449 19450 19451 19452 19453 19454 19455 19456 19457 19458 19459 19460 19461 19462 19463 19464 19465 19466 19467 19468 19469 19470 19471 19472 19473 19474 19475 19476 19477 19478 19479 19480 19481 19482 19483 19484 19485 19486 19487 19488 19489 19490 19491 19492 19493 19494 19495 19496 19497 19498 19499 19500 19501 19502 19503 19504 19505 19506 19507 19508 19509 19510 19511 19512 19513 19514 19515 19516 19517 19518 19519 19520 19521 19522 19523 19524 19525 19526 19527 19528 19529 19530 19531 19532 19533 19534 19535 19536 19537 19538 19539 19540 19541 19542 19543 19544 19545 19546 19547 19548 19549 19550 19551 19552 19553 19554 19555 19556 19557 19558 19559 19560 19561 19562 19563 19564 19565 19566 19567 19568 19569 19570 19571 19572 19573 19574 19575 19576 19577 19578 19579 19580 19581 19582 19583 19584 19585 19586 19587 19588 19589 19590 19591 19592 19593 19594 19595 19596 19597 19598 19599 19600 19601 19602 19603 19604 19605 19606 19607 19608 19609 19610 19611 19612 19613 19614 19615 19616 19617 19618 19619 19620 19621 19622 19623 19624 19625 19626 19627 19628 19629 19630 19631 19632 19633 19634 19635 19636 19637 19638 19639 19640 19641 19642 19643 19644 19645 19646 19647 19648 19649 19650 19651 19652 19653 19654 19655 19656 19657 19658 19659 19660 19661 19662 19663 19664 19665 19666 19667 19668 19669 19670 19671 19672 19673 19674 19675 19676 19677 19678 19679 19680 19681 19682 19683 19684 19685 19686 19687 19688 19689 19690 19691 19692 19693 19694 19695 19696 19697 19698 19699 19700 19701 19702 19703 19704 19705 19706 19707 19708 19709 19710 19711 19712 19713 19714 19715 19716 19717 19718 19719 19720 19721 19722 19723 19724 19725 19726 19727 19728 19729 19730 19731 19732 19733 19734 19735 19736 19737 19738 19739 19740 19741 19742 19743 19744 19745 19746 19747 19748 19749 19750 19751 19752 19753 19754 19755 19756 19757 19758 19759 19760 19761 19762 19763 19764 19765 19766 19767 19768 19769 19770 19771 19772 19773 19774 19775 19776 19777 19778 19779 19780 19781 19782 19783 19784 19785 19786 19787 19788 19789 19790 19791 19792 19793 19794 19795 19796 19797 19798 19799 19800 19801 19802 19803 19804 19805 19806 19807 19808 19809 19810 19811 19812 19813 19814 19815 19816 19817 19818 19819 19820 19821 19822 19823 19824 19825 19826 19827 19828 19829 19830 19831 19832 19833 19834 19835 19836 19837 19838 19839 19840 19841 19842 19843 19844 19845 19846 19847 19848 19849 19850 19851 19852 19853 19854 19855 19856 19857 19858 19859 19860 19861 19862 19863 19864 19865 19866 19867 19868 19869 19870 19871 19872 19873 19874 19875 19876 19877 19878 19879 19880 19881 19882 19883 19884 19885 19886 19887 19888 19889 19890 19891 19892 19893 19894 19895 19896 19897 19898 19899 19900 19901 19902 19903 19904 19905 19906 19907 19908 19909 19910 19911 19912 19913 19914 19915 19916 19917 19918 19919 19920 19921 19922 19923 19924 19925 19926 19927 19928 19929 19930 19931 19932 19933 19934 19935 19936 19937 19938 19939 19940 19941 19942 19943 19944 19945 19946 19947 19948 19949 19950 19951 19952 19953 19954 19955 19956 19957 19958 19959 19960 19961 19962 19963 19964 19965 19966 19967 19968 19969 19970 19971 19972 19973 19974 19975 19976 19977 19978 19979 19980 19981 19982 19983 19984 19985 19986 19987 19988 19989 19990 19991 19992 19993 19994 19995 19996 19997 19998 19999 20000 20001 20002 20003 20004 20005 20006 20007 20008 20009 20010 20011 20012 20013 20014 20015 20016 20017 20018 20019 20020 20021 20022 20023 20024 20025 20026 20027 20028 20029 20030 20031 20032 20033 20034 20035 20036 20037 20038 20039 20040 20041 20042 20043 20044 20045 20046 20047 20048 20049 20050 20051 20052 20053 20054 20055 20056 20057 20058 20059 20060 20061 20062 20063 20064 20065 20066 20067 20068 20069 20070 20071 20072 20073 20074 20075 20076 20077 20078 20079 20080 20081 20082 20083 20084 20085 20086 20087 20088 20089 20090 20091 20092 20093 20094 20095 20096 20097 20098 20099 20100 20101 20102 20103 20104 20105 20106 20107 20108 20109 20110 20111 20112 20113 20114 20115 20116 20117 20118 20119 20120 20121 20122 20123 20124 20125 20126 20127 20128 20129 20130 20131 20132 20133 20134 20135 20136 20137 20138 20139 20140 20141 20142 20143 20144 20145 20146 20147 20148 20149 20150 20151 20152 20153 20154 20155 20156 20157 20158 20159 20160 20161 20162 20163 20164 20165 20166 20167 20168 20169 20170 20171 20172 20173 20174 20175 20176 20177 20178 20179 20180 20181 20182 20183 20184 20185 20186 20187 20188 20189 20190 20191 20192 20193 20194 20195 20196 20197 20198 20199 20200 20201 20202 20203 20204 20205 20206 20207 20208 20209 20210 20211 20212 20213 20214 20215 20216 20217 20218 20219 20220 20221 20222 20223 20224 20225 20226 20227 20228 20229 20230 20231 20232 20233 20234 20235 20236 20237 20238 20239 20240 20241 20242 20243 20244 20245 20246 20247 20248 20249 20250 20251 20252 20253 20254 20255 20256 20257 20258 20259 20260 20261 20262 20263 20264 20265 20266 20267 20268 20269 20270 20271 20272 20273 20274 20275 20276 20277 20278 20279 20280 20281 20282 20283 20284 20285 20286 20287 20288 20289 20290 20291 20292 20293 20294 20295 20296 20297 20298 20299 20300 20301 20302 20303 20304 20305 20306 20307 20308 20309 20310 20311 20312 20313 20314 20315 20316 20317 20318 20319 20320 20321 20322 20323 20324 20325 20326 20327 20328 20329 20330 20331 20332 20333 20334 20335 20336 20337 20338 20339 20340 20341 20342 20343 20344 20345 20346 20347 20348 20349 20350 20351 20352 20353 20354 20355 20356 20357 20358 20359 20360 20361 20362 20363 20364 20365 20366 20367 20368 20369 20370 20371 20372 20373 20374 20375 20376 20377 20378 20379 20380 20381 20382 20383 20384 20385 20386 20387 20388 20389 20390 20391 20392 20393 20394 20395 20396 20397 20398 20399 20400 20401 20402 20403 20404 20405 20406 20407 20408 20409 20410 20411 20412 20413 20414 20415 20416 20417 20418 20419 20420 20421 20422 20423 20424 20425 20426 20427 20428 20429 20430 20431 20432 20433 20434 20435 20436 20437 20438 20439 20440 20441 20442 20443 20444 20445 20446 20447 20448 20449 20450 20451 20452 20453 20454 20455 20456 20457 20458 20459 20460 20461 20462 20463 20464 20465 20466 20467 20468 20469 20470 20471 20472 20473 20474 20475 20476 20477 20478 20479 20480 20481 20482 20483 20484 20485 20486 20487 20488 20489 20490 20491 20492 20493 20494 20495 20496 20497 20498 20499 20500 20501 20502 20503 20504 20505 20506 20507 20508 20509 20510 20511 20512 20513 20514 20515 20516 20517 20518 20519 20520 20521 20522 20523 20524 20525 20526 20527 20528 20529 20530 20531 20532 20533 20534 20535 20536 20537 20538 20539 20540 20541 20542 20543 20544 20545 20546 20547 20548 20549 20550 20551 20552 20553 20554 20555 20556 20557 20558 20559 20560 20561 20562 20563 20564 20565 20566 20567 20568 20569 20570 20571 20572 20573 20574 20575 20576 20577 20578 20579 20580 20581 20582 20583 20584 20585 20586 20587 20588 20589 20590 20591 20592 20593 20594 20595 20596 20597 20598 20599 20600 20601 20602 20603 20604 20605 20606 20607 20608 20609 20610 20611 20612 20613 20614 20615 20616 20617 20618 20619 20620 20621 20622 20623 20624 20625 20626 20627 20628 20629 20630 20631 20632 20633 20634 20635 20636 20637 20638 20639 20640 20641 20642 20643 20644 20645 20646 20647 20648 20649 20650 20651 20652 20653 20654 20655 20656 20657 20658 20659 20660 20661 20662 20663 20664 20665 20666 20667 20668 20669 20670 20671 20672 20673 20674 20675 20676 20677 20678 20679 20680 20681 20682 20683 20684 20685 20686 20687 20688 20689 20690 20691 20692 20693 20694 20695 20696 20697 20698 20699 20700 20701 20702 20703 20704 20705 20706 20707 20708 20709 20710 20711 20712 20713 20714 20715 20716 20717 20718 20719 20720 20721 20722 20723 20724 20725 20726 20727 20728 20729 20730 20731 20732 20733 20734 20735 20736 20737 20738 20739 20740 20741 20742 20743 20744 20745 20746 20747 20748 20749 20750 20751 20752 20753 20754 20755 20756 20757 20758 20759 20760 20761 20762 20763 20764 20765 20766 20767 20768 20769 20770 20771 20772 20773 20774 20775 20776 20777 20778 20779 20780 20781 20782 20783 20784 20785 20786 20787 20788 20789 20790 20791 20792 20793 20794 20795 20796 20797 20798 20799 20800 20801 20802 20803 20804 20805 20806 20807 20808 20809 20810 20811 20812 20813 20814 20815 20816 20817 20818 20819 20820 20821 20822 20823 20824 20825 20826 20827 20828 20829 20830 20831 20832 20833 20834 20835 20836 20837 20838 20839 20840 20841 20842 20843 20844 20845 20846 20847 20848 20849 20850 20851 20852 20853 20854 20855 20856 20857 20858 20859 20860 20861 20862 20863 20864 20865 20866 20867 20868 20869 20870 20871 20872 20873 20874 20875 20876 20877 20878 20879 20880 20881 20882 20883 20884 20885 20886 20887 20888 20889 20890 20891 20892 20893 20894 20895 20896 20897 20898 20899 20900 20901 20902 20903 20904 20905 20906 20907 20908 20909 20910 20911 20912 20913 20914 20915 20916 20917 20918 20919 20920 20921 20922 20923 20924 20925 20926 20927 20928 20929 20930 20931 20932 20933 20934 20935 20936 20937 20938 20939 20940 20941 20942 20943 20944 20945 20946 20947 20948 20949 20950 20951 20952 20953 20954 20955 20956 20957 20958 20959 20960 20961 20962 20963 20964 20965 20966 20967 20968 20969 20970 20971 20972 20973 20974 20975 20976 20977 20978 20979 20980 20981 20982 20983 20984 20985 20986 20987 20988 20989 20990 20991 20992 20993 20994 20995 20996 20997 20998 20999 21000 21001 21002 21003 21004 21005 21006 21007 21008 21009 21010 21011 21012 21013 21014 21015 21016 21017 21018 21019 21020 21021 21022 21023 21024 21025 21026 21027 21028 21029 21030 21031 21032 21033 21034 21035 21036 21037 21038 21039 21040 21041 21042 21043 21044 21045 21046 21047 21048 21049 21050 21051 21052 21053 21054 21055 21056 21057 21058 21059 21060 21061 21062 21063 21064 21065 21066 21067 21068 21069 21070 21071 21072 21073 21074 21075 21076 21077 21078 21079 21080 21081 21082 21083 21084 21085 21086 21087 21088 21089 21090 21091 21092 21093 21094 21095 21096 21097 21098 21099 21100 21101 21102 21103 21104 21105 21106 21107 21108 21109 21110 21111 21112 21113 21114 21115 21116 21117 21118 21119 21120 21121 21122 21123 21124 21125 21126 21127 21128 21129 21130 21131 21132 21133 21134 21135 21136 21137 21138 21139 21140 21141 21142 21143 21144 21145 21146 21147 21148 21149 21150 21151 21152 21153 21154 21155 21156 21157 21158 21159 21160 21161 21162 21163 21164 21165 21166 21167 21168 21169 21170 21171 21172 21173 21174 21175 21176 21177 21178 21179 21180 21181 21182 21183 21184 21185 21186 21187 21188 21189 21190 21191 21192 21193 21194 21195 21196 21197 21198 21199 21200 21201 21202 21203 21204 21205 21206 21207 21208 21209 21210 21211 21212 21213 21214 21215 21216 21217 21218 21219 21220 21221 21222 21223 21224 21225 21226 21227 21228 21229 21230 21231 21232 21233 21234 21235 21236 21237 21238 21239 21240 21241 21242 21243 21244 21245 21246 21247 21248 21249 21250 21251 21252 21253 21254 21255 21256 21257 21258 21259 21260 21261 21262 21263 21264 21265 21266 21267 21268 21269 21270 21271 21272 21273 21274 21275 21276 21277 21278 21279 21280 21281 21282 21283 21284 21285 21286 21287 21288 21289 21290 21291 21292 21293 21294 21295 21296 21297 21298 21299 21300 21301 21302 21303 21304 21305 21306 21307 21308 21309 21310 21311 21312 21313 21314 21315 21316 21317 21318 21319 21320 21321 21322 21323 21324 21325 21326 21327 21328 21329 21330 21331 21332 21333 21334 21335 21336 21337 21338 21339 21340 21341 21342 21343 21344 21345 21346 21347 21348 21349 21350 21351 21352 21353 21354 21355 21356 21357 21358 21359 21360 21361 21362 21363 21364 21365 21366 21367 21368 21369 21370 21371 21372 21373 21374 21375 21376 21377 21378 21379 21380 21381 21382 21383 21384 21385 21386 21387 21388 21389 21390 21391 21392 21393 21394 21395 21396 21397 21398 21399 21400 21401 21402 21403 21404 21405 21406 21407 21408 21409 21410 21411 21412 21413 21414 21415 21416 21417 21418 21419 21420 21421 21422 21423 21424 21425 21426 21427 21428 21429 21430 21431 21432 21433 21434 21435 21436 21437 21438 21439 21440 21441 21442 21443 21444 21445 21446 21447 21448 21449 21450 21451 21452 21453 21454 21455 21456 21457 21458 21459 21460 21461 21462 21463 21464 21465 21466 21467 21468 21469 21470 21471 21472 21473 21474 21475 21476 21477 21478 21479 21480 21481 21482 21483 21484 21485 21486 21487 21488 21489 21490 21491 21492 21493 21494 21495 21496 21497 21498 21499 21500 21501 21502 21503 21504 21505 21506 21507 21508 21509 21510 21511 21512 21513 21514 21515 21516 21517 21518 21519 21520 21521 21522 21523 21524 21525 21526 21527 21528 21529 21530 21531 21532 21533 21534 21535 21536 21537 21538 21539 21540 21541 21542 21543 21544 21545 21546 21547 21548 21549 21550 21551 21552 21553 21554 21555 21556 21557 21558 21559 21560 21561 21562 21563 21564 21565 21566 21567 21568 21569 21570 21571 21572 21573 21574 21575 21576 21577 21578 21579 21580 21581 21582 21583 21584 21585 21586 21587 21588 21589 21590 21591 21592 21593 21594 21595 21596 21597 21598 21599 21600 21601 21602 21603 21604 21605 21606 21607 21608 21609 21610 21611 21612 21613 21614 21615 21616 21617 21618 21619 21620 21621 21622 21623 21624 21625 21626 21627 21628 21629 21630 21631 21632 21633 21634 21635 21636 21637 21638 21639 21640 21641 21642 21643 21644 21645 21646 21647 21648 21649 21650 21651 21652 21653 21654 21655 21656 21657 21658 21659 21660 21661 21662 21663 21664 21665 21666 21667 21668 21669 21670 21671 21672 21673 21674 21675 21676 21677 21678 21679 21680 21681 21682 21683 21684 21685 21686 21687 21688 21689 21690 21691 21692 21693 21694 21695 21696 21697 21698 21699 21700 21701 21702 21703 21704 21705 21706 21707 21708 21709 21710 21711 21712 21713 21714 21715 21716 21717 21718 21719 21720 21721 21722 21723 21724 21725 21726 21727 21728 21729 21730 21731 21732 21733 21734 21735 21736 21737 21738 21739 21740 21741 21742 21743 21744 21745 21746 21747 21748 21749 21750 21751 21752 21753 21754 21755 21756 21757 21758 21759 21760 21761 21762 21763 21764 21765 21766 21767 21768 21769 21770 21771 21772 21773 21774 21775 21776 21777 21778 21779 21780 21781 21782 21783 21784 21785 21786 21787 21788 21789 21790 21791 21792 21793 21794 21795 21796 21797 21798 21799 21800 21801 21802 21803 21804 21805 21806 21807 21808 21809 21810 21811 21812 21813 21814 21815 21816 21817 21818 21819 21820 21821 21822 21823 21824 21825 21826 21827 21828 21829 21830 21831 21832 21833 21834 21835 21836 21837 21838 21839 21840 21841 21842 21843 21844 21845 21846 21847 21848 21849 21850 21851 21852 21853 21854 21855 21856 21857 21858 21859 21860 21861 21862 21863 21864 21865 21866 21867 21868 21869 21870 21871 21872 21873 21874 21875 21876 21877 21878 21879 21880 21881 21882 21883 21884 21885 21886 21887 21888 21889 21890 21891 21892 21893 21894 21895 21896 21897 21898 21899 21900 21901 21902 21903 21904 21905 21906 21907 21908 21909 21910 21911 21912 21913 21914 21915 21916 21917 21918 21919 21920 21921 21922 21923 21924 21925 21926 21927 21928 21929 21930 21931 21932 21933 21934 21935 21936 21937 21938 21939 21940 21941 21942 21943 21944 21945 21946 21947 21948 21949 21950 21951 21952 21953 21954 21955 21956 21957 21958 21959 21960 21961 21962 21963 21964 21965 21966 21967 21968 21969 21970 21971 21972 21973 21974 21975 21976 21977 21978 21979 21980 21981 21982 21983 21984 21985 21986 21987 21988 21989 21990 21991 21992 21993 21994 21995 21996 21997 21998 21999 22000 22001 22002 22003 22004 22005 22006 22007 22008 22009 22010 22011 22012 22013 22014 22015 22016 22017 22018 22019 22020 22021 22022 22023 22024 22025 22026 22027 22028 22029 22030 22031 22032 22033 22034 22035 22036 22037 22038 22039 22040 22041 22042 22043 22044 22045 22046 22047 22048 22049 22050 22051 22052 22053 22054 22055 22056 22057 22058 22059 22060 22061 22062 22063 22064 22065 22066 22067 22068 22069 22070 22071 22072 22073 22074 22075 22076 22077 22078 22079 22080 22081 22082 22083 22084 22085 22086 22087 22088 22089 22090 22091 22092 22093 22094 22095 22096 22097 22098 22099 22100 22101 22102 22103 22104 22105 22106 22107 22108 22109 22110 22111 22112 22113 22114 22115 22116 22117 22118 22119 22120 22121 22122 22123 22124 22125 22126 22127 22128 22129 22130 22131 22132 22133 22134 22135 22136 22137 22138 22139 22140 22141 22142 22143 22144 22145 22146 22147 22148 22149 22150 22151 22152 22153 22154 22155 22156 22157 22158 22159 22160 22161 22162 22163 22164 22165 22166 22167 22168 22169 22170 22171 22172 22173 22174 22175 22176 22177 22178 22179 22180 22181 22182 22183 22184 22185 22186 22187 22188 22189 22190 22191 22192 22193 22194 22195 22196 22197 22198 22199 22200 22201 22202 22203 22204 22205 22206 22207 22208 22209 22210 22211 22212 22213 22214 22215 22216 22217 22218 22219 22220 22221 22222 22223 22224 22225 22226 22227 22228 22229 22230 22231 22232 22233 22234 22235 22236 22237 22238 22239 22240 22241 22242 22243 22244 22245 22246 22247 22248 22249 22250 22251 22252 22253 22254 22255 22256 22257 22258 22259 22260 22261 22262 22263 22264 22265 22266 22267 22268 22269 22270 22271 22272 22273 22274 22275 22276 22277 22278 22279 22280 22281 22282 22283 22284 22285 22286 22287 22288 22289 22290 22291 22292 22293 22294 22295 22296 22297 22298 22299 22300 22301 22302 22303 22304 22305 22306 22307 22308 22309 22310 22311 22312 22313 22314 22315 22316 22317 22318 22319 22320 22321 22322 22323 22324 22325 22326 22327 22328 22329 22330 22331 22332 22333 22334 22335 22336 22337 22338 22339 22340 22341 22342 22343 22344 22345 22346 22347 22348 22349 22350 22351 22352 22353 22354 22355 22356 22357 22358 22359 22360 22361 22362 22363 22364 22365 22366 22367 22368 22369 22370 22371 22372 22373 22374 22375 22376 22377 22378 22379 22380 22381 22382 22383 22384 22385 22386 22387 22388 22389 22390 22391 22392 22393 22394 22395 22396 22397 22398 22399 22400 22401 22402 22403 22404 22405 22406 22407 22408 22409 22410 22411 22412 22413 22414 22415 22416 22417 22418 22419 22420 22421 22422 22423 22424 22425 22426 22427 22428 22429 22430 22431 22432 22433 22434 22435 22436 22437 22438 22439 22440 22441 22442 22443 22444 22445 22446 22447 22448 22449 22450 22451 22452 22453 22454 22455 22456 22457 22458 22459 22460 22461 22462 22463 22464 22465 22466 22467 22468 22469 22470 22471 22472 22473 22474 22475 22476 22477 22478 22479 22480 22481 22482 22483 22484 22485 22486 22487 22488 22489 22490 22491 22492 22493 22494 22495 22496 22497 22498 22499 22500 22501 22502 22503 22504 22505 22506 22507 22508 22509 22510 22511 22512 22513 22514 22515 22516 22517 22518 22519 22520 22521 22522 22523 22524 22525 22526 22527 22528 22529 22530 22531 22532 22533 22534 22535 22536 22537 22538 22539 22540 22541 22542 22543 22544 22545 22546 22547 22548 22549 22550 22551 22552 22553 22554 22555 22556 22557 22558 22559 22560 22561 22562 22563 22564 22565 22566 22567 22568 22569 22570 22571 22572 22573 22574 22575 22576 22577 22578 22579 22580 22581 22582 22583 22584 22585 22586 22587 22588 22589 22590 22591 22592 22593 22594 22595 22596 22597 22598 22599 22600 22601 22602 22603 22604 22605 22606 22607 22608 22609 22610 22611 22612 22613 22614 22615 22616 22617 22618 22619 22620 22621 22622 22623 22624 22625 22626 22627 22628 22629 22630 22631 22632 22633 22634 22635 22636 22637 22638 22639 22640 22641 22642 22643 22644 22645 22646 22647 22648 22649 22650 22651 22652 22653 22654 22655 22656 22657 22658 22659 22660 22661 22662 22663 22664 22665 22666 22667 22668 22669 22670 22671 22672 22673 22674 22675 22676 22677 22678 22679 22680 22681 22682 22683 22684 22685 22686 22687 22688 22689 22690 22691 22692 22693 22694 22695 22696 22697 22698 22699 22700 22701 22702 22703 22704 22705 22706 22707 22708 22709 22710 22711 22712 22713 22714 22715 22716 22717 22718 22719 22720 22721 22722 22723 22724 22725 22726 22727 22728 22729 22730 22731 22732 22733 22734 22735 22736 22737 22738 22739 22740 22741 22742 22743 22744 22745 22746 22747 22748 22749 22750 22751 22752 22753 22754 22755 22756 22757 22758 22759 22760 22761 22762 22763 22764 22765 22766 22767 22768 22769 22770 22771 22772 22773 22774 22775 22776 22777 22778 22779 22780 22781 22782 22783 22784 22785 22786 22787 22788 22789 22790 22791 22792 22793 22794 22795 22796 22797 22798 22799 22800 22801 22802 22803 22804 22805 22806 22807 22808 22809 22810 22811 22812 22813 22814 22815 22816 22817 22818 22819 22820 22821 22822 22823 22824 22825 22826 22827 22828 22829 22830 22831 22832 22833 22834 22835 22836 22837 22838 22839 22840 22841 22842 22843 22844 22845 22846 22847 22848 22849 22850 22851 22852 22853 22854 22855 22856 22857 22858 22859 22860 22861 22862 22863 22864 22865 22866 22867 22868 22869 22870 22871 22872 22873 22874 22875 22876 22877 22878 22879 22880 22881 22882 22883 22884 22885 22886 22887 22888 22889 22890 22891 22892 22893 22894 22895 22896 22897 22898 22899 22900 22901 22902 22903 22904 22905 22906 22907 22908 22909 22910 22911 22912 22913 22914 22915 22916 22917 22918 22919 22920 22921 22922 22923 22924 22925 22926 22927 22928 22929 22930 22931 22932 22933 22934 22935 22936 22937 22938 22939 22940 22941 22942 22943 22944 22945 22946 22947 22948 22949 22950 22951 22952 22953 22954 22955 22956 22957 22958 22959 22960 22961 22962 22963 22964 22965 22966 22967 22968 22969 22970 22971 22972 22973 22974 22975 22976 22977 22978 22979 22980 22981 22982 22983 22984 22985 22986 22987 22988 22989 22990 22991 22992 22993 22994 22995 22996 22997 22998 22999 23000 23001 23002 23003 23004 23005 23006 23007 23008 23009 23010 23011 23012 23013 23014 23015 23016 23017 23018 23019 23020 23021 23022 23023 23024 23025 23026 23027 23028 23029 23030 23031 23032 23033 23034 23035 23036 23037 23038 23039 23040 23041 23042 23043 23044 23045 23046 23047 23048 23049 23050 23051 23052 23053 23054 23055 23056 23057 23058 23059 23060 23061 23062 23063 23064 23065 23066 23067 23068 23069 23070 23071 23072 23073 23074 23075 23076 23077 23078 23079 23080 23081 23082 23083 23084 23085 23086 23087 23088 23089 23090 23091 23092 23093 23094 23095 23096 23097 23098 23099 23100 23101 23102 23103 23104 23105 23106 23107 23108 23109 23110 23111 23112 23113 23114 23115 23116 23117 23118 23119 23120 23121 23122 23123 23124 23125 23126 23127 23128 23129 23130 23131 23132 23133 23134 23135 23136 23137 23138 23139 23140 23141 23142 23143 23144 23145 23146 23147 23148 23149 23150 23151 23152 23153 23154 23155 23156 23157 23158 23159 23160 23161 23162 23163 23164 23165 23166 23167 23168 23169 23170 23171 23172 23173 23174 23175 23176 23177 23178 23179 23180 23181 23182 23183 23184 23185 23186 23187 23188 23189 23190 23191 23192 23193 23194 23195 23196 23197 23198 23199 23200 23201 23202 23203 23204 23205 23206 23207 23208 23209 23210 23211 23212 23213 23214 23215 23216 23217 23218 23219 23220 23221 23222 23223 23224 23225 23226 23227 23228 23229 23230 23231 23232 23233 23234 23235 23236 23237 23238 23239 23240 23241 23242 23243 23244 23245 23246 23247 23248 23249 23250 23251 23252 23253 23254 23255 23256 23257 23258 23259 23260 23261 23262 23263 23264 23265 23266 23267 23268 23269 23270 23271 23272 23273 23274 23275 23276 23277 23278 23279 23280 23281 23282 23283 23284 23285 23286 23287 23288 23289 23290 23291 23292 23293 23294 23295 23296 23297 23298 23299 23300 23301 23302 23303 23304 23305 23306 23307 23308 23309 23310 23311 23312 23313 23314 23315 23316 23317 23318 23319 23320 23321 23322 23323 23324 23325 23326 23327 23328 23329 23330 23331 23332 23333 23334 23335 23336 23337 23338 23339 23340 23341 23342 23343 23344 23345 23346 23347 23348 23349 23350 23351 23352 23353 23354 23355 23356 23357 23358 23359 23360 23361 23362 23363 23364 23365 23366 23367 23368 23369 23370 23371 23372 23373 23374 23375 23376 23377 23378 23379 23380 23381 23382 23383 23384 23385 23386 23387 23388 23389 23390 23391 23392 23393 23394 23395 23396 23397 23398 23399 23400 23401 23402 23403 23404 23405 23406 23407 23408 23409 23410 23411 23412 23413 23414 23415 23416 23417 23418 23419 23420 23421 23422 23423 23424 23425 23426 23427 23428 23429 23430 23431 23432 23433 23434 23435 23436 23437 23438 23439 23440 23441 23442 23443 23444 23445 23446 23447 23448 23449 23450 23451 23452 23453 23454 23455 23456 23457 23458 23459 23460 23461 23462 23463 23464 23465 23466 23467 23468 23469 23470 23471 23472 23473 23474 23475 23476 23477 23478 23479 23480 23481 23482 23483 23484 23485 23486 23487 23488 23489 23490 23491 23492 23493 23494 23495 23496 23497 23498 23499 23500 23501 23502 23503 23504 23505 23506 23507 23508 23509 23510 23511 23512 23513 23514 23515 23516 23517 23518 23519 23520 23521 23522 23523 23524 23525 23526 23527 23528 23529 23530 23531 23532 23533 23534 23535 23536 23537 23538 23539 23540 23541 23542 23543 23544 23545 23546 23547 23548 23549 23550 23551 23552 23553 23554 23555 23556 23557 23558 23559 23560 23561 23562 23563 23564 23565 23566 23567 23568 23569 23570 23571 23572 23573 23574 23575 23576 23577 23578 23579 23580 23581 23582 23583 23584 23585 23586 23587 23588 23589 23590 23591 23592 23593 23594 23595 23596 23597 23598 23599 23600 23601 23602 23603 23604 23605 23606 23607 23608 23609 23610 23611 23612 23613 23614 23615 23616 23617 23618 23619 23620 23621 23622 23623 23624 23625 23626 23627 23628 23629 23630 23631 23632 23633 23634 23635 23636 23637 23638 23639 23640 23641 23642 23643 23644 23645 23646 23647 23648 23649 23650 23651 23652 23653 23654 23655 23656 23657 23658 23659 23660 23661 23662 23663 23664 23665 23666 23667 23668 23669 23670 23671 23672 23673 23674 23675 23676 23677 23678 23679 23680 23681 23682 23683 23684 23685 23686 23687 23688 23689 23690 23691 23692 23693 23694 23695 23696 23697 23698 23699 23700 23701 23702 23703 23704 23705 23706 23707 23708 23709 23710 23711 23712 23713 23714 23715 23716 23717 23718 23719 23720 23721 23722 23723 23724 23725 23726 23727 23728 23729 23730 23731 23732 23733 23734 23735 23736 23737 23738 23739 23740 23741 23742 23743 23744 23745 23746 23747 23748 23749 23750 23751 23752 23753 23754 23755 23756 23757 23758 23759 23760 23761 23762 23763 23764 23765 23766 23767 23768 23769 23770 23771 23772 23773 23774 23775 23776 23777 23778 23779 23780 23781 23782 23783 23784 23785 23786 23787 23788 23789 23790 23791 23792 23793 23794 23795 23796 23797 23798 23799 23800 23801 23802 23803 23804 23805 23806 23807 23808 23809 23810 23811 23812 23813 23814 23815 23816 23817 23818 23819 23820 23821 23822 23823 23824 23825 23826 23827 23828 23829 23830 23831 23832 23833 23834 23835 23836 23837 23838 23839 23840 23841 23842 23843 23844 23845 23846 23847 23848 23849 23850 23851 23852 23853 23854 23855 23856 23857 23858 23859 23860 23861 23862 23863 23864 23865 23866 23867 23868 23869 23870 23871 23872 23873 23874 23875 23876 23877 23878 23879 23880 23881 23882 23883 23884 23885 23886 23887 23888 23889 23890 23891 23892 23893 23894 23895 23896 23897 23898 23899 23900 23901 23902 23903 23904 23905 23906 23907 23908 23909 23910 23911 23912 23913 23914 23915 23916 23917 23918 23919 23920 23921 23922 23923 23924 23925 23926 23927 23928 23929 23930 23931 23932 23933 23934 23935 23936 23937 23938 23939 23940 23941 23942 23943 23944 23945 23946 23947 23948 23949 23950 23951 23952 23953 23954 23955 23956 23957 23958 23959 23960 23961 23962 23963 23964 23965 23966 23967 23968 23969 23970 23971 23972 23973 23974 23975 23976 23977 23978 23979 23980 23981 23982 23983 23984 23985 23986 23987 23988 23989 23990 23991 23992 23993 23994 23995 23996 23997 23998 23999 24000 24001 24002 24003 24004 24005 24006 24007 24008 24009 24010 24011 24012 24013 24014 24015 24016 24017 24018 24019 24020 24021 24022 24023 24024 24025 24026 24027 24028 24029 24030 24031 24032 24033 24034 24035 24036 24037 24038 24039 24040 24041 24042 24043 24044 24045 24046 24047 24048 24049 24050 24051 24052 24053 24054 24055 24056 24057 24058 24059 24060 24061 24062 24063 24064 24065 24066 24067 24068 24069 24070 24071 24072 24073 24074 24075 24076 24077 24078 24079 24080 24081 24082 24083 24084 24085 24086 24087 24088 24089 24090 24091 24092 24093 24094 24095 24096 24097 24098 24099 24100 24101 24102 24103 24104 24105 24106 24107 24108 24109 24110 24111 24112 24113 24114 24115 24116 24117 24118 24119 24120 24121 24122 24123 24124 24125 24126 24127 24128 24129 24130 24131 24132 24133 24134 24135 24136 24137 24138 24139 24140 24141 24142 24143 24144 24145 24146 24147 24148 24149 24150 24151 24152 24153 24154 24155 24156 24157 24158 24159 24160 24161 24162 24163 24164 24165 24166 24167 24168 24169 24170 24171 24172 24173 24174 24175 24176 24177 24178 24179 24180 24181 24182 24183 24184 24185 24186 24187 24188 24189 24190 24191 24192 24193 24194 24195 24196 24197 24198 24199 24200 24201 24202 24203 24204 24205 24206 24207 24208 24209 24210 24211 24212 24213 24214 24215 24216 24217 24218 24219 24220 24221 24222 24223 24224 24225 24226 24227 24228 24229 24230 24231 24232 24233 24234 24235 24236 24237 24238 24239 24240 24241 24242 24243 24244 24245 24246 24247 24248 24249 24250 24251 24252 24253 24254 24255 24256 24257 24258 24259 24260 24261 24262 24263 24264 24265 24266 24267 24268 24269 24270 24271 24272 24273 24274 24275 24276 24277 24278 24279 24280 24281 24282 24283 24284 24285 24286 24287 24288 24289 24290 24291 24292 24293 24294 24295 24296 24297 24298 24299 24300 24301 24302 24303 24304 24305 24306 24307 24308 24309 24310 24311 24312 24313 24314 24315 24316 24317 24318 24319 24320 24321 24322 24323 24324 24325 24326 24327 24328 24329 24330 24331 24332 24333 24334 24335 24336 24337 24338 24339 24340 24341 24342 24343 24344 24345 24346 24347 24348 24349 24350 24351 24352 24353 24354 24355 24356 24357 24358 24359 24360 24361 24362 24363 24364 24365 24366 24367 24368 24369 24370 24371 24372 24373 24374 24375 24376 24377 24378 24379 24380 24381 24382 24383 24384 24385 24386 24387 24388 24389 24390 24391 24392 24393 24394 24395 24396 24397 24398 24399 24400 24401 24402 24403 24404 24405 24406 24407 24408 24409 24410 24411 24412 24413 24414 24415 24416 24417 24418 24419 24420 24421 24422 24423 24424 24425 24426 24427 24428 24429 24430 24431 24432 24433 24434 24435 24436 24437 24438 24439 24440 24441 24442 24443 24444 24445 24446 24447 24448 24449 24450 24451 24452 24453 24454 24455 24456 24457 24458 24459 24460 24461 24462 24463 24464 24465 24466 24467 24468 24469 24470 24471 24472 24473 24474 24475 24476 24477 24478 24479 24480 24481 24482 24483 24484 24485 24486 24487 24488 24489 24490 24491 24492 24493 24494 24495 24496 24497 24498 24499 24500 24501 24502 24503 24504 24505 24506 24507 24508 24509 24510 24511 24512 24513 24514 24515 24516 24517 24518 24519 24520 24521 24522 24523 24524 24525 24526 24527 24528 24529 24530 24531 24532 24533 24534 24535 24536 24537 24538 24539 24540 24541 24542 24543 24544 24545 24546 24547 24548 24549 24550 24551 24552 24553 24554 24555 24556 24557 24558 24559 24560 24561 24562 24563 24564 24565 24566 24567 24568 24569 24570 24571 24572 24573 24574 24575 24576 24577 24578 24579 24580 24581 24582 24583 24584 24585 24586 24587 24588 24589 24590 24591 24592 24593 24594 24595 24596 24597 24598 24599 24600 24601 24602 24603 24604 24605 24606 24607 24608 24609 24610 24611 24612 24613 24614 24615 24616 24617 24618 24619 24620 24621 24622 24623 24624 24625 24626 24627 24628 24629 24630 24631 24632 24633 24634 24635 24636 24637 24638 24639 24640 24641 24642 24643 24644 24645 24646 24647 24648 24649 24650 24651 24652 24653 24654 24655 24656 24657 24658 24659 24660 24661 24662 24663 24664 24665 24666 24667 24668 24669 24670 24671 24672 24673 24674 24675 24676 24677 24678 24679 24680 24681 24682 24683 24684 24685 24686 24687 24688 24689 24690 24691 24692 24693 24694 24695 24696 24697 24698 24699 24700 24701 24702 24703 24704 24705 24706 24707 24708 24709 24710 24711 24712 24713 24714 24715 24716 24717 24718 24719 24720 24721 24722 24723 24724 24725 24726 24727 24728 24729 24730 24731 24732 24733 24734 24735 24736 24737 24738 24739 24740 24741 24742 24743 24744 24745 24746 24747 24748 24749 24750 24751 24752 24753 24754 24755 24756 24757 24758 24759 24760 24761 24762 24763 24764 24765 24766 24767 24768 24769 24770 24771 24772 24773 24774 24775 24776 24777 24778 24779 24780 24781 24782 24783 24784 24785 24786 24787 24788 24789 24790 24791 24792 24793 24794 24795 24796 24797 24798 24799 24800 24801 24802 24803 24804 24805 24806 24807 24808 24809 24810 24811 24812 24813 24814 24815 24816 24817 24818 24819 24820 24821 24822 24823 24824 24825 24826 24827 24828 24829 24830 24831 24832 24833 24834 24835 24836 24837 24838 24839 24840 24841 24842 24843 24844 24845 24846 24847 24848 24849 24850 24851 24852 24853 24854 24855 24856 24857 24858 24859 24860 24861 24862 24863 24864 24865 24866 24867 24868 24869 24870 24871 24872 24873 24874 24875 24876 24877 24878 24879 24880 24881 24882 24883 24884 24885 24886 24887 24888 24889 24890 24891 24892 24893 24894 24895 24896 24897 24898 24899 24900 24901 24902 24903 24904 24905 24906 24907 24908 24909 24910 24911 24912 24913 24914 24915 24916 24917 24918 24919 24920 24921 24922 24923 24924 24925 24926 24927 24928 24929 24930 24931 24932 24933 24934 24935 24936 24937 24938 24939 24940 24941 24942 24943 24944 24945 24946 24947 24948 24949 24950 24951 24952 24953 24954 24955 24956 24957 24958 24959 24960 24961 24962 24963 24964 24965 24966 24967 24968 24969 24970 24971 24972 24973 24974 24975 24976 24977 24978 24979 24980 24981 24982 24983 24984 24985 24986 24987 24988 24989 24990 24991 24992 24993 24994 24995 24996 24997 24998 24999 25000 25001 25002 25003 25004 25005 25006 25007 25008 25009 25010 25011 25012 25013 25014 25015 25016 25017 25018 25019 25020 25021 25022 25023 25024 25025 25026 25027 25028 25029 25030 25031 25032 25033 25034 25035 25036 25037 25038 25039 25040 25041 25042 25043 25044 25045 25046 25047 25048 25049 25050 25051 25052 25053 25054 25055 25056 25057 25058 25059 25060 25061 25062 25063 25064 25065 25066 25067 25068 25069 25070 25071 25072 25073 25074 25075 25076 25077 25078 25079 25080 25081 25082 25083 25084 25085 25086 25087 25088 25089 25090 25091 25092 25093 25094 25095 25096 25097 25098 25099 25100 25101 25102 25103 25104 25105 25106 25107 25108 25109 25110 25111 25112 25113 25114 25115 25116 25117 25118 25119 25120 25121 25122 25123 25124 25125 25126 25127 25128 25129 25130 25131 25132 25133 25134 25135 25136 25137 25138 25139 25140 25141 25142 25143 25144 25145 25146 25147 25148 25149 25150 25151 25152 25153 25154 25155 25156 25157 25158 25159 25160 25161 25162 25163 25164 25165 25166 25167 25168 25169 25170 25171 25172 25173 25174 25175 25176 25177 25178 25179 25180 25181 25182 25183 25184 25185 25186 25187 25188 25189 25190 25191 25192 25193 25194 25195 25196 25197 25198 25199 25200 25201 25202 25203 25204 25205 25206 25207 25208 25209 25210 25211 25212 25213 25214 25215 25216 25217 25218 25219 25220 25221 25222 25223 25224 25225 25226 25227 25228 25229 25230 25231 25232 25233 25234 25235 25236 25237 25238 25239 25240 25241 25242 25243 25244 25245 25246 25247 25248 25249 25250 25251 25252 25253 25254 25255 25256 25257 25258 25259 25260 25261 25262 25263 25264 25265 25266 25267 25268 25269 25270 25271 25272 25273 25274 25275 25276 25277 25278 25279 25280 25281 25282 25283 25284 25285 25286 25287 25288 25289 25290 25291 25292 25293 25294 25295 25296 25297 25298 25299 25300 25301 25302 25303 25304 25305 25306 25307 25308 25309 25310 25311 25312 25313 25314 25315 25316 25317 25318 25319 25320 25321 25322 25323 25324 25325 25326 25327 25328 25329 25330 25331 25332 25333 25334 25335 25336 25337 25338 25339 25340 25341 25342 25343 25344 25345 25346 25347 25348 25349 25350 25351 25352 25353 25354 25355 25356 25357 25358 25359 25360 25361 25362 25363 25364 25365 25366 25367 25368 25369 25370 25371 25372 25373 25374 25375 25376 25377 25378 25379 25380 25381 25382 25383 25384 25385 25386 25387 25388 25389 25390 25391 25392 25393 25394 25395 25396 25397 25398 25399 25400 25401 25402 25403 25404 25405 25406 25407 25408 25409 25410 25411 25412 25413 25414 25415 25416 25417 25418 25419 25420 25421 25422 25423 25424 25425 25426 25427 25428 25429 25430 25431 25432 25433 25434 25435 25436 25437 25438 25439 25440 25441 25442 25443 25444 25445 25446 25447 25448 25449 25450 25451 25452 25453 25454 25455 25456 25457 25458 25459 25460 25461 25462 25463 25464 25465 25466 25467 25468 25469 25470 25471 25472 25473 25474 25475 25476 25477 25478 25479 25480 25481 25482 25483 25484 25485 25486 25487 25488 25489 25490 25491 25492 25493 25494 25495 25496 25497 25498 25499 25500 25501 25502 25503 25504 25505 25506 25507 25508 25509 25510 25511 25512 25513 25514 25515 25516 25517 25518 25519 25520 25521 25522 25523 25524 25525 25526 25527 25528 25529 25530 25531 25532 25533 25534 25535 25536 25537 25538 25539 25540 25541 25542 25543 25544 25545 25546 25547 25548 25549 25550 25551 25552 25553 25554 25555 25556 25557 25558 25559 25560 25561 25562 25563 25564 25565 25566 25567 25568 25569 25570 25571 25572 25573 25574 25575 25576 25577 25578 25579 25580 25581 25582 25583 25584 25585 25586 25587 25588 25589 25590 25591 25592 25593 25594 25595 25596 25597 25598 25599 25600 25601 25602 25603 25604 25605 25606 25607 25608 25609 25610 25611 25612 25613 25614 25615 25616 25617 25618 25619 25620 25621 25622 25623 25624 25625 25626 25627 25628 25629 25630 25631 25632 25633 25634 25635 25636 25637 25638 25639 25640 25641 25642 25643 25644 25645 25646 25647 25648 25649 25650 25651 25652 25653 25654 25655 25656 25657 25658 25659 25660 25661 25662 25663 25664 25665 25666 25667 25668 25669 25670 25671 25672 25673 25674 25675 25676 25677 25678 25679 25680 25681 25682 25683 25684 25685 25686 25687 25688 25689 25690 25691 25692 25693 25694 25695 25696 25697 25698 25699 25700 25701 25702 25703 25704 25705 25706 25707 25708 25709 25710 25711 25712 25713 25714 25715 25716 25717 25718 25719 25720 25721 25722 25723 25724 25725 25726 25727 25728 25729 25730 25731 25732 25733 25734 25735 25736 25737 25738 25739 25740 25741 25742 25743 25744 25745 25746 25747 25748 25749 25750 25751 25752 25753 25754 25755 25756 25757 25758 25759 25760 25761 25762 25763 25764 25765 25766 25767 25768 25769 25770 25771 25772 25773 25774 25775 25776 25777 25778 25779 25780 25781 25782 25783 25784 25785 25786 25787 25788 25789 25790 25791 25792 25793 25794 25795 25796 25797 25798 25799 25800 25801 25802 25803 25804 25805 25806 25807 25808 25809 25810 25811 25812 25813 25814 25815 25816 25817 25818 25819 25820 25821 25822 25823 25824 25825 25826 25827 25828 25829 25830 25831 25832 25833 25834 25835 25836 25837 25838 25839 25840 25841 25842 25843 25844 25845 25846 25847 25848 25849 25850 25851 25852 25853 25854 25855 25856 25857 25858 25859 25860 25861 25862 25863 25864 25865 25866 25867 25868 25869 25870 25871 25872 25873 25874 25875 25876 25877 25878 25879 25880 25881 25882 25883 25884 25885 25886 25887 25888 25889 25890 25891 25892 25893 25894 25895 25896 25897 25898 25899 25900 25901 25902 25903 25904 25905 25906 25907 25908 25909 25910 25911 25912 25913 25914 25915 25916 25917 25918 25919 25920 25921 25922 25923 25924 25925 25926 25927 25928 25929 25930 25931 25932 25933 25934 25935 25936 25937 25938 25939 25940 25941 25942 25943 25944 25945 25946 25947 25948 25949 25950 25951 25952 25953 25954 25955 25956 25957 25958 25959 25960 25961 25962 25963 25964 25965 25966 25967 25968 25969 25970 25971 25972 25973 25974 25975 25976 25977 25978 25979 25980 25981 25982 25983 25984 25985 25986 25987 25988 25989 25990 25991 25992 25993 25994 25995 25996 25997 25998 25999 26000 26001 26002 26003 26004 26005 26006 26007 26008 26009 26010 26011 26012 26013 26014 26015 26016 26017 26018 26019 26020 26021 26022 26023 26024 26025 26026 26027 26028 26029 26030 26031 26032 26033 26034 26035 26036 26037 26038 26039 26040 26041 26042 26043 26044 26045 26046 26047 26048 26049 26050 26051 26052 26053 26054 26055 26056 26057 26058 26059 26060 26061 26062 26063 26064 26065 26066 26067 26068 26069 26070 26071 26072 26073 26074 26075 26076 26077 26078 26079 26080 26081 26082 26083 26084 26085 26086 26087 26088 26089 26090 26091 26092 26093 26094 26095 26096 26097 26098 26099 26100 26101 26102 26103 26104 26105 26106 26107 26108 26109 26110 26111 26112 26113 26114 26115 26116 26117 26118 26119 26120 26121 26122 26123 26124 26125 26126 26127 26128 26129 26130 26131 26132 26133 26134 26135 26136 26137 26138 26139 26140 26141 26142 26143 26144 26145 26146 26147 26148 26149 26150 26151 26152 26153 26154 26155 26156 26157 26158 26159 26160 26161 26162 26163 26164 26165 26166 26167 26168 26169 26170 26171 26172 26173 26174 26175 26176 26177 26178 26179 26180 26181 26182 26183 26184 26185 26186 26187 26188 26189 26190 26191 26192 26193 26194 26195 26196 26197 26198 26199 26200 26201 26202 26203 26204 26205 26206 26207 26208 26209 26210 26211 26212 26213 26214 26215 26216 26217 26218 26219 26220 26221 26222 26223 26224 26225 26226 26227 26228 26229 26230 26231 26232 26233 26234 26235 26236 26237 26238 26239 26240 26241 26242 26243 26244 26245 26246 26247 26248 26249 26250 26251 26252 26253 26254 26255 26256 26257 26258 26259 26260 26261 26262 26263 26264 26265 26266 26267 26268 26269 26270 26271 26272 26273 26274 26275 26276 26277 26278 26279 26280 26281 26282 26283 26284 26285 26286 26287 26288 26289 26290 26291 26292 26293 26294 26295 26296 26297 26298 26299 26300 26301 26302 26303 26304 26305 26306 26307 26308 26309 26310 26311 26312 26313 26314 26315 26316 26317 26318 26319 26320 26321 26322 26323 26324 26325 26326 26327 26328 26329 26330 26331 26332 26333 26334 26335 26336 26337 26338 26339 26340 26341 26342 26343 26344 26345 26346 26347 26348 26349 26350 26351 26352 26353 26354 26355 26356 26357 26358 26359 26360 26361 26362 26363 26364 26365 26366 26367 26368 26369 26370 26371 26372 26373 26374 26375 26376 26377 26378 26379 26380 26381 26382 26383 26384 26385 26386 26387 26388 26389 26390 26391 26392 26393 26394 26395 26396 26397 26398 26399 26400 26401 26402 26403 26404 26405 26406 26407 26408 26409 26410 26411 26412 26413 26414 26415 26416 26417 26418 26419 26420 26421 26422 26423 26424 26425 26426 26427 26428 26429 26430 26431 26432 26433 26434 26435 26436 26437 26438 26439 26440 26441 26442 26443 26444 26445 26446 26447 26448 26449 26450 26451 26452 26453 26454 26455 26456 26457 26458 26459 26460 26461 26462 26463 26464 26465 26466 26467 26468 26469 26470 26471 26472 26473 26474 26475 26476 26477 26478 26479 26480 26481 26482 26483 26484 26485 26486 26487 26488 26489 26490 26491 26492 26493 26494 26495 26496 26497 26498 26499 26500 26501 26502 26503 26504 26505 26506 26507 26508 26509 26510 26511 26512 26513 26514 26515 26516 26517 26518 26519 26520 26521 26522 26523 26524 26525 26526 26527 26528 26529 26530 26531 26532 26533 26534 26535 26536 26537 26538 26539 26540 26541 26542 26543 26544 26545 26546 26547 26548 26549 26550 26551 26552 26553 26554 26555 26556 26557 26558 26559 26560 26561 26562 26563 26564 26565 26566 26567 26568 26569 26570 26571 26572 26573 26574 26575 26576 26577 26578 26579 26580 26581 26582 26583 26584 26585 26586 26587 26588 26589 26590 26591 26592 26593 26594 26595 26596 26597 26598 26599 26600 26601 26602 26603 26604 26605 26606 26607 26608 26609 26610 26611 26612 26613 26614 26615 26616 26617 26618 26619 26620 26621 26622 26623 26624 26625 26626 26627 26628 26629 26630 26631 26632 26633 26634 26635 26636 26637 26638 26639 26640 26641 26642 26643 26644 26645 26646 26647 26648 26649 26650 26651 26652 26653 26654 26655 26656 26657 26658 26659 26660 26661 26662 26663 26664 26665 26666 26667 26668 26669 26670 26671 26672 26673 26674 26675 26676 26677 26678 26679 26680 26681 26682 26683 26684 26685 26686 26687 26688 26689 26690 26691 26692 26693 26694 26695 26696 26697 26698 26699 26700 26701 26702 26703 26704 26705 26706 26707 26708 26709 26710 26711 26712 26713 26714 26715 26716 26717 26718 26719 26720 26721 26722 26723 26724 26725 26726 26727 26728 26729 26730 26731 26732 26733 26734 26735 26736 26737 26738 26739 26740 26741 26742 26743 26744 26745 26746 26747 26748 26749 26750 26751 26752 26753 26754 26755 26756 26757 26758 26759 26760 26761 26762 26763 26764 26765 26766 26767 26768 26769 26770 26771 26772 26773 26774 26775 26776 26777 26778 26779 26780 26781 26782 26783 26784 26785 26786 26787 26788 26789 26790 26791 26792 26793 26794 26795 26796 26797 26798 26799 26800 26801 26802 26803 26804 26805 26806 26807 26808 26809 26810 26811 26812 26813 26814 26815 26816 26817 26818 26819 26820 26821 26822 26823 26824 26825 26826 26827 26828 26829 26830 26831 26832 26833 26834 26835 26836 26837 26838 26839 26840 26841 26842 26843 26844 26845 26846 26847 26848 26849 26850 26851 26852 26853 26854 26855 26856 26857 26858 26859 26860 26861 26862 26863 26864 26865 26866 26867 26868 26869 26870 26871 26872 26873 26874 26875 26876 26877 26878 26879 26880 26881 26882 26883 26884 26885 26886 26887 26888 26889 26890 26891 26892 26893 26894 26895 26896 26897 26898 26899 26900 26901 26902 26903 26904 26905 26906 26907 26908 26909 26910 26911 26912 26913 26914 26915 26916 26917 26918 26919 26920 26921 26922 26923 26924 26925 26926 26927 26928 26929 26930 26931 26932 26933 26934 26935 26936 26937 26938 26939 26940 26941 26942 26943 26944 26945 26946 26947 26948 26949 26950 26951 26952 26953 26954 26955 26956 26957 26958 26959 26960 26961 26962 26963 26964 26965 26966 26967 26968 26969 26970 26971 26972 26973 26974 26975 26976 26977 26978 26979 26980 26981 26982 26983 26984 26985 26986 26987 26988 26989 26990 26991 26992 26993 26994 26995 26996 26997 26998 26999 27000 27001 27002 27003 27004 27005 27006 27007 27008 27009 27010 27011 27012 27013 27014 27015 27016 27017 27018 27019 27020 27021 27022 27023 27024 27025 27026 27027 27028 27029 27030 27031 27032 27033 27034 27035 27036 27037 27038 27039 27040 27041 27042 27043 27044 27045 27046 27047 27048 27049 27050 27051 27052 27053 27054 27055 27056 27057 27058 27059 27060 27061 27062 27063 27064 27065 27066 27067 27068 27069 27070 27071 27072 27073 27074 27075 27076 27077 27078 27079 27080 27081 27082 27083 27084 27085 27086 27087 27088 27089 27090 27091 27092 27093 27094 27095 27096 27097 27098 27099 27100 27101 27102 27103 27104 27105 27106 27107 27108 27109 27110 27111 27112 27113 27114 27115 27116 27117 27118 27119 27120 27121 27122 27123 27124 27125 27126 27127 27128 27129 27130 27131 27132 27133 27134 27135 27136 27137 27138 27139 27140 27141 27142 27143 27144 27145 27146 27147 27148 27149 27150 27151 27152 27153 27154 27155 27156 27157 27158 27159 27160 27161 27162 27163 27164 27165 27166 27167 27168 27169 27170 27171 27172 27173 27174 27175 27176 27177 27178 27179 27180 27181 27182 27183 27184 27185 27186 27187 27188 27189 27190 27191 27192 27193 27194 27195 27196 27197 27198 27199 27200 27201 27202 27203 27204 27205 27206 27207 27208 27209 27210 27211 27212 27213 27214 27215 27216 27217 27218 27219 27220 27221 27222 27223 27224 27225 27226 27227 27228 27229 27230 27231 27232 27233 27234 27235 27236 27237 27238 27239 27240 27241 27242 27243 27244 27245 27246 27247 27248 27249 27250 27251 27252 27253 27254 27255 27256 27257 27258 27259 27260 27261 27262 27263 27264 27265 27266 27267 27268 27269 27270 27271 27272 27273 27274 27275 27276 27277 27278 27279 27280 27281 27282 27283 27284 27285 27286 27287 27288 27289 27290 27291 27292 27293 27294 27295 27296 27297 27298 27299 27300 27301 27302 27303 27304 27305 27306 27307 27308 27309 27310 27311 27312 27313 27314 27315 27316 27317 27318 27319 27320 27321 27322 27323 27324 27325 27326 27327 27328 27329 27330 27331 27332 27333 27334 27335 27336 27337 27338 27339 27340 27341 27342 27343 27344 27345 27346 27347 27348 27349 27350 27351 27352 27353 27354 27355 27356 27357 27358 27359 27360 27361 27362 27363 27364 27365 27366 27367 27368 27369 27370 27371 27372 27373 27374 27375 27376 27377 27378 27379 27380 27381 27382 27383 27384 27385 27386 27387 27388 27389 27390 27391 27392 27393 27394 27395 27396 27397 27398 27399 27400 27401 27402 27403 27404 27405 27406 27407 27408 27409 27410 27411 27412 27413 27414 27415 27416 27417 27418 27419 27420 27421 27422 27423 27424 27425 27426 27427 27428 27429 27430 27431 27432 27433 27434 27435 27436 27437 27438 27439 27440 27441 27442 27443 27444 27445 27446 27447 27448 27449 27450 27451 27452 27453 27454 27455 27456 27457 27458 27459 27460 27461 27462 27463 27464 27465 27466 27467 27468 27469 27470 27471 27472 27473 27474 27475 27476 27477 27478 27479 27480 27481 27482 27483 27484 27485 27486 27487 27488 27489 27490 27491 27492 27493 27494 27495 27496 27497 27498 27499 27500 27501 27502 27503 27504 27505 27506 27507 27508 27509 27510 27511 27512 27513 27514 27515 27516 27517 27518 27519 27520 27521 27522 27523 27524 27525 27526 27527 27528 27529 27530 27531 27532 27533 27534 27535 27536 27537 27538 27539 27540 27541 27542 27543 27544 27545 27546 27547 27548 27549 27550 27551 27552 27553 27554 27555 27556 27557 27558 27559 27560 27561 27562 27563 27564 27565 27566 27567 27568 27569 27570 27571 27572 27573 27574 27575 27576 27577 27578 27579 27580 27581 27582 27583 27584 27585 27586 27587 27588 27589 27590 27591 27592 27593 27594 27595 27596 27597 27598 27599 27600 27601 27602 27603 27604 27605 27606 27607 27608 27609 27610 27611 27612 27613 27614 27615 27616 27617 27618 27619 27620 27621 27622 27623 27624 27625 27626 27627 27628 27629 27630 27631 27632 27633 27634 27635 27636 27637 27638 27639 27640 27641 27642 27643 27644 27645 27646 27647 27648 27649 27650 27651 27652 27653 27654 27655 27656 27657 27658 27659 27660 27661 27662 27663 27664 27665 27666 27667 27668 27669 27670 27671 27672 27673 27674 27675 27676 27677 27678 27679 27680 27681 27682 27683 27684 27685 27686 27687 27688 27689 27690 27691 27692 27693 27694 27695 27696 27697 27698 27699 27700 27701 27702 27703 27704 27705 27706 27707 27708 27709 27710 27711 27712 27713 27714 27715 27716 27717 27718 27719 27720 27721 27722 27723 27724 27725 27726 27727 27728 27729 27730 27731 27732 27733 27734 27735 27736 27737 27738 27739 27740 27741 27742 27743 27744 27745 27746 27747 27748 27749 27750 27751 27752 27753 27754 27755 27756 27757 27758 27759 27760 27761 27762 27763 27764 27765 27766 27767 27768 27769 27770 27771 27772 27773 27774 27775 27776 27777 27778 27779 27780 27781 27782 27783 27784 27785 27786 27787 27788 27789 27790 27791 27792 27793 27794 27795 27796 27797 27798 27799 27800 27801 27802 27803 27804 27805 27806 27807 27808 27809 27810 27811 27812 27813 27814 27815 27816 27817 27818 27819 27820 27821 27822 27823 27824 27825 27826 27827 27828 27829 27830 27831 27832 27833 27834 27835 27836 27837 27838 27839 27840 27841 27842 27843 27844 27845 27846 27847 27848 27849 27850 27851 27852 27853 27854 27855 27856 27857 27858 27859 27860 27861 27862 27863 27864 27865 27866 27867 27868 27869 27870 27871 27872 27873 27874 27875 27876 27877 27878 27879 27880 27881 27882 27883 27884 27885 27886 27887 27888 27889 27890 27891 27892 27893 27894 27895 27896 27897 27898 27899 27900 27901 27902 27903 27904 27905 27906 27907 27908 27909 27910 27911 27912 27913 27914 27915 27916 27917 27918 27919 27920 27921 27922 27923 27924 27925 27926 27927 27928 27929 27930 27931 27932 27933 27934 27935 27936 27937 27938 27939 27940 27941 27942 27943 27944 27945 27946 27947 27948 27949 27950 27951 27952 27953 27954 27955 27956 27957 27958 27959 27960 27961 27962 27963 27964 27965 27966 27967 27968 27969 27970 27971 27972 27973 27974 27975 27976 27977 27978 27979 27980 27981 27982 27983 27984 27985 27986 27987 27988 27989 27990 27991 27992 27993 27994 27995 27996 27997 27998 27999 28000 28001 28002 28003 28004 28005 28006 28007 28008 28009 28010 28011 28012 28013 28014 28015 28016 28017 28018 28019 28020 28021 28022 28023 28024 28025 28026 28027 28028 28029 28030 28031 28032 28033 28034 28035 28036 28037 28038 28039 28040 28041 28042 28043 28044 28045 28046 28047 28048 28049 28050 28051 28052 28053 28054 28055 28056 28057 28058 28059 28060 28061 28062 28063 28064 28065 28066 28067 28068 28069 28070 28071 28072 28073 28074 28075 28076 28077 28078 28079 28080 28081 28082 28083 28084 28085 28086 28087 28088 28089 28090 28091 28092 28093 28094 28095 28096 28097 28098 28099 28100 28101 28102 28103 28104 28105 28106 28107 28108 28109 28110 28111 28112 28113 28114 28115 28116 28117 28118 28119 28120 28121 28122 28123 28124 28125 28126 28127 28128 28129 28130 28131 28132 28133 28134 28135 28136 28137 28138 28139 28140 28141 28142 28143 28144 28145 28146 28147 28148 28149 28150 28151 28152 28153 28154 28155 28156 28157 28158 28159 28160 28161 28162 28163 28164 28165 28166 28167 28168 28169 28170 28171 28172 28173 28174 28175 28176 28177 28178 28179 28180 28181 28182 28183 28184 28185 28186 28187 28188 28189 28190 28191 28192 28193 28194 28195 28196 28197 28198 28199 28200 28201 28202 28203 28204 28205 28206 28207 28208 28209 28210 28211 28212 28213 28214 28215 28216 28217 28218 28219 28220 28221 28222 28223 28224 28225 28226 28227 28228 28229 28230 28231 28232 28233 28234 28235 28236 28237 28238 28239 28240 28241 28242 28243 28244 28245 28246 28247 28248 28249 28250 28251 28252 28253 28254 28255 28256 28257 28258 28259 28260 28261 28262 28263 28264 28265 28266 28267 28268 28269 28270 28271 28272 28273 28274 28275 28276 28277 28278 28279 28280 28281 28282 28283 28284 28285 28286 28287 28288 28289 28290 28291 28292 28293 28294 28295 28296 28297 28298 28299 28300 28301 28302 28303 28304 28305 28306 28307 28308 28309 28310 28311 28312 28313 28314 28315 28316 28317 28318 28319 28320 28321 28322 28323 28324 28325 28326 28327 28328 28329 28330 28331 28332 28333 28334 28335 28336 28337 28338 28339 28340 28341 28342 28343 28344 28345 28346 28347 28348 28349 28350 28351 28352 28353 28354 28355 28356 28357 28358 28359 28360 28361 28362 28363 28364 28365 28366 28367 28368 28369 28370 28371 28372 28373 28374 28375 28376 28377 28378 28379 28380 28381 28382 28383 28384 28385 28386 28387 28388 28389 28390 28391 28392 28393 28394 28395 28396 28397 28398 28399 28400 28401 28402 28403 28404 28405 28406 28407 28408 28409 28410 28411 28412 28413 28414 28415 28416 28417 28418 28419 28420 28421 28422 28423 28424 28425 28426 28427 28428 28429 28430 28431 28432 28433 28434 28435 28436 28437 28438 28439 28440 28441 28442 28443 28444 28445 28446 28447 28448 28449 28450 28451 28452 28453 28454 28455 28456 28457 28458 28459 28460 28461 28462 28463 28464 28465 28466 28467 28468 28469 28470 28471 28472 28473 28474 28475 28476 28477 28478 28479 28480 28481 28482 28483 28484 28485 28486 28487 28488 28489 28490 28491 28492 28493 28494 28495 28496 28497 28498 28499 28500 28501 28502 28503 28504 28505 28506 28507 28508 28509 28510 28511 28512 28513 28514 28515 28516 28517 28518 28519 28520 28521 28522 28523 28524 28525 28526 28527 28528 28529 28530 28531 28532 28533 28534 28535 28536 28537 28538 28539 28540 28541 28542 28543 28544 28545 28546 28547 28548 28549 28550 28551 28552 28553 28554 28555 28556 28557 28558 28559 28560 28561 28562 28563 28564 28565 28566 28567 28568 28569 28570 28571 28572 28573 28574 28575 28576 28577 28578 28579 28580 28581 28582 28583 28584 28585 28586 28587 28588 28589 28590 28591 28592 28593 28594 28595 28596 28597 28598 28599 28600 28601 28602 28603 28604 28605 28606 28607 28608 28609 28610 28611 28612 28613 28614 28615 28616 28617 28618 28619 28620 28621 28622 28623 28624 28625 28626 28627 28628 28629 28630 28631 28632 28633 28634 28635 28636 28637 28638 28639 28640 28641 28642 28643 28644 28645 28646 28647 28648 28649 28650 28651 28652 28653 28654 28655 28656 28657 28658 28659 28660 28661 28662 28663 28664 28665 28666 28667 28668 28669 28670 28671 28672 28673 28674 28675 28676 28677 28678 28679 28680 28681 28682 28683 28684 28685 28686 28687 28688 28689 28690 28691 28692 28693 28694 28695 28696 28697 28698 28699 28700 28701 28702 28703 28704 28705 28706 28707 28708 28709 28710 28711 28712 28713 28714 28715 28716 28717 28718 28719 28720 28721 28722 28723 28724 28725 28726 28727 28728 28729 28730 28731 28732 28733 28734 28735 28736 28737 28738 28739 28740 28741 28742 28743 28744 28745 28746 28747 28748 28749 28750 28751 28752 28753 28754 28755 28756 28757 28758 28759 28760 28761 28762 28763 28764 28765 28766 28767 28768 28769 28770 28771 28772 28773 28774 28775 28776 28777 28778 28779 28780 28781 28782 28783 28784 28785 28786 28787 28788 28789 28790 28791 28792 28793 28794 28795 28796 28797 28798 28799 28800 28801 28802 28803 28804 28805 28806 28807 28808 28809 28810 28811 28812 28813 28814 28815 28816 28817 28818 28819 28820 28821 28822 28823 28824 28825 28826 28827 28828 28829 28830 28831 28832 28833 28834 28835 28836 28837 28838 28839 28840 28841 28842 28843 28844 28845 28846 28847 28848 28849 28850 28851 28852 28853 28854 28855 28856 28857 28858 28859 28860 28861 28862 28863 28864 28865 28866 28867 28868 28869 28870 28871 28872 28873 28874 28875 28876 28877 28878 28879 28880 28881 28882 28883 28884 28885 28886 28887 28888 28889 28890 28891 28892 28893 28894 28895 28896 28897 28898 28899 28900 28901 28902 28903 28904 28905 28906 28907 28908 28909 28910 28911 28912 28913 28914 28915 28916 28917 28918 28919 28920 28921 28922 28923 28924 28925 28926 28927 28928 28929 28930 28931 28932 28933 28934 28935 28936 28937 28938 28939 28940 28941 28942 28943 28944 28945 28946 28947 28948 28949 28950 28951 28952 28953 28954 28955 28956 28957 28958 28959 28960 28961 28962 28963 28964 28965 28966 28967 28968 28969 28970 28971 28972 28973 28974 28975 28976 28977 28978 28979 28980 28981 28982 28983 28984 28985 28986 28987 28988 28989 28990 28991 28992 28993 28994 28995 28996 28997 28998 28999 29000 29001 29002 29003 29004 29005 29006 29007 29008 29009 29010 29011 29012 29013 29014 29015 29016 29017 29018 29019 29020 29021 29022 29023 29024 29025 29026 29027 29028 29029 29030 29031 29032 29033 29034 29035 29036 29037 29038 29039 29040 29041 29042 29043 29044 29045 29046 29047 29048 29049 29050 29051 29052 29053 29054 29055 29056 29057 29058 29059 29060 29061 29062 29063 29064 29065 29066 29067 29068 29069 29070 29071 29072 29073 29074 29075 29076 29077 29078 29079 29080 29081 29082 29083 29084 29085 29086 29087 29088 29089 29090 29091 29092 29093 29094 29095 29096 29097 29098 29099 29100 29101 29102 29103 29104 29105 29106 29107 29108 29109 29110 29111 29112 29113 29114 29115 29116 29117 29118 29119 29120 29121 29122 29123 29124 29125 29126 29127 29128 29129 29130 29131 29132 29133 29134 29135 29136 29137 29138 29139 29140 29141 29142 29143 29144 29145 29146 29147 29148 29149 29150 29151 29152 29153 29154 29155 29156 29157 29158 29159 29160 29161 29162 29163 29164 29165 29166 29167 29168 29169 29170 29171 29172 29173 29174 29175 29176 29177 29178 29179 29180 29181 29182 29183 29184 29185 29186 29187 29188 29189 29190 29191 29192 29193 29194 29195 29196 29197 29198 29199 29200 29201 29202 29203 29204 29205 29206 29207 29208 29209 29210 29211 29212 29213 29214 29215 29216 29217 29218 29219 29220 29221 29222 29223 29224 29225 29226 29227 29228 29229 29230 29231 29232 29233 29234 29235 29236 29237 29238 29239 29240 29241 29242 29243 29244 29245 29246 29247 29248 29249 29250 29251 29252 29253 29254 29255 29256 29257 29258 29259 29260 29261 29262 29263 29264 29265 29266 29267 29268 29269 29270 29271 29272 29273 29274 29275 29276 29277 29278 29279 29280 29281 29282 29283 29284 29285 29286 29287 29288 29289 29290 29291 29292 29293 29294 29295 29296 29297 29298 29299 29300 29301 29302 29303 29304 29305 29306 29307 29308 29309 29310 29311 29312 29313 29314 29315 29316 29317 29318 29319 29320 29321 29322 29323 29324 29325 29326 29327 29328 29329 29330 29331 29332 29333 29334 29335 29336 29337 29338 29339 29340 29341 29342 29343 29344 29345 29346 29347 29348 29349 29350 29351 29352 29353 29354 29355 29356 29357 29358 29359 29360 29361 29362 29363 29364 29365 29366 29367 29368 29369 29370 29371 29372 29373 29374 29375 29376 29377 29378 29379 29380 29381 29382 29383 29384 29385 29386 29387 29388 29389 29390 29391 29392 29393 29394 29395 29396 29397 29398 29399 29400 29401 29402 29403 29404 29405 29406 29407 29408 29409 29410 29411 29412 29413 29414 29415 29416 29417 29418 29419 29420 29421 29422 29423 29424 29425 29426 29427 29428 29429 29430 29431 29432 29433 29434 29435 29436 29437 29438 29439 29440 29441 29442 29443 29444 29445 29446 29447 29448 29449 29450 29451 29452 29453 29454 29455 29456 29457 29458 29459 29460 29461 29462 29463 29464 29465 29466 29467 29468 29469 29470 29471 29472 29473 29474 29475 29476 29477 29478 29479 29480 29481 29482 29483 29484 29485 29486 29487 29488 29489 29490 29491 29492 29493 29494 29495 29496 29497 29498 29499 29500 29501 29502 29503 29504 29505 29506 29507 29508 29509 29510 29511 29512 29513 29514 29515 29516 29517 29518 29519 29520 29521 29522 29523 29524 29525 29526 29527 29528 29529 29530 29531 29532 29533 29534 29535 29536 29537 29538 29539 29540 29541 29542 29543 29544 29545 29546 29547 29548 29549 29550 29551 29552 29553 29554 29555 29556 29557 29558 29559 29560 29561 29562 29563 29564 29565 29566 29567 29568 29569 29570 29571 29572 29573 29574 29575 29576 29577 29578 29579 29580 29581 29582 29583 29584 29585 29586 29587 29588 29589 29590 29591 29592 29593 29594 29595 29596 29597 29598 29599 29600 29601 29602 29603 29604 29605 29606 29607 29608 29609 29610 29611 29612 29613 29614 29615 29616 29617 29618 29619 29620 29621 29622 29623 29624 29625 29626 29627 29628 29629 29630 29631 29632 29633 29634 29635 29636 29637 29638 29639 29640 29641 29642 29643 29644 29645 29646 29647 29648 29649 29650 29651 29652 29653 29654 29655 29656 29657 29658 29659 29660 29661 29662 29663 29664 29665 29666 29667 29668 29669 29670 29671 29672 29673 29674 29675 29676 29677 29678 29679 29680 29681 29682 29683 29684 29685 29686 29687 29688 29689 29690 29691 29692 29693 29694 29695 29696 29697 29698 29699 29700 29701 29702 29703 29704 29705 29706 29707 29708 29709 29710 29711 29712 29713 29714 29715 29716 29717 29718 29719 29720 29721 29722 29723 29724 29725 29726 29727 29728 29729 29730 29731 29732 29733 29734 29735 29736 29737 29738 29739 29740 29741 29742 29743 29744 29745 29746 29747 29748 29749 29750 29751 29752 29753 29754 29755 29756 29757 29758 29759 29760 29761 29762 29763 29764 29765 29766 29767 29768 29769 29770 29771 29772 29773 29774 29775 29776 29777 29778 29779 29780 29781 29782 29783 29784 29785 29786 29787 29788 29789 29790 29791 29792 29793 29794 29795 29796 29797 29798 29799 29800 29801 29802 29803 29804 29805 29806 29807 29808 29809 29810 29811 29812 29813 29814 29815 29816 29817 29818 29819 29820 29821 29822 29823 29824 29825 29826 29827 29828 29829 29830 29831 29832 29833 29834 29835 29836 29837 29838 29839 29840 29841 29842 29843 29844 29845 29846 29847 29848 29849 29850 29851 29852 29853 29854 29855 29856 29857 29858 29859 29860 29861 29862 29863 29864 29865 29866 29867 29868 29869 29870 29871 29872 29873 29874 29875 29876 29877 29878 29879 29880 29881 29882 29883 29884 29885 29886 29887 29888 29889 29890 29891 29892 29893 29894 29895 29896 29897 29898 29899 29900 29901 29902 29903 29904 29905 29906 29907 29908 29909 29910 29911 29912 29913 29914 29915 29916 29917 29918 29919 29920 29921 29922 29923 29924 29925 29926 29927 29928 29929 29930 29931 29932 29933 29934 29935 29936 29937 29938 29939 29940 29941 29942 29943 29944 29945 29946 29947 29948 29949 29950 29951 29952 29953 29954 29955 29956 29957 29958 29959 29960 29961 29962 29963 29964 29965 29966 29967 29968 29969 29970 29971 29972 29973 29974 29975 29976 29977 29978 29979 29980 29981 29982 29983 29984 29985 29986 29987 29988 29989 29990 29991 29992 29993 29994 29995 29996 29997 29998 29999 30000 30001 30002 30003 30004 30005 30006 30007 30008 30009 30010 30011 30012 30013 30014 30015 30016 30017 30018 30019 30020 30021 30022 30023 30024 30025 30026 30027 30028 30029 30030 30031 30032 30033 30034 30035 30036 30037 30038 30039 30040 30041 30042 30043 30044 30045 30046 30047 30048 30049 30050 30051 30052 30053 30054 30055 30056 30057 30058 30059 30060 30061 30062 30063 30064 30065 30066 30067 30068 30069 30070 30071 30072 30073 30074 30075 30076 30077 30078 30079 30080 30081 30082 30083 30084 30085 30086 30087 30088 30089 30090 30091 30092 30093 30094 30095 30096 30097 30098 30099 30100 30101 30102 30103 30104 30105 30106 30107 30108 30109 30110 30111 30112 30113 30114 30115 30116 30117 30118 30119 30120 30121 30122 30123 30124 30125 30126 30127 30128 30129 30130 30131 30132 30133 30134 30135 30136 30137 30138 30139 30140 30141 30142 30143 30144 30145 30146 30147 30148 30149 30150 30151 30152 30153 30154 30155 30156 30157 30158 30159 30160 30161 30162 30163 30164 30165 30166 30167 30168 30169 30170 30171 30172 30173 30174 30175 30176 30177 30178 30179 30180 30181 30182 30183 30184 30185 30186 30187 30188 30189 30190 30191 30192 30193 30194 30195 30196 30197 30198 30199 30200 30201 30202 30203 30204 30205 30206 30207 30208 30209 30210 30211 30212 30213 30214 30215 30216 30217 30218 30219 30220 30221 30222 30223 30224 30225 30226 30227 30228 30229 30230 30231 30232 30233 30234 30235 30236 30237 30238 30239 30240 30241 30242 30243 30244 30245 30246 30247 30248 30249 30250 30251 30252 30253 30254 30255 30256 30257 30258 30259 30260 30261 30262 30263 30264 30265 30266 30267 30268 30269 30270 30271 30272 30273 30274 30275 30276 30277 30278 30279 30280 30281 30282 30283 30284 30285 30286 30287 30288 30289 30290 30291 30292 30293 30294 30295 30296 30297 30298 30299 30300 30301 30302 30303 30304 30305 30306 30307 30308 30309 30310 30311 30312 30313 30314 30315 30316 30317 30318 30319 30320 30321 30322 30323 30324 30325 30326 30327 30328 30329 30330 30331 30332 30333 30334 30335 30336 30337 30338 30339 30340 30341 30342 30343 30344 30345 30346 30347 30348 30349 30350 30351 30352 30353 30354 30355 30356 30357 30358 30359 30360 30361 30362 30363 30364 30365 30366 30367 30368 30369 30370 30371 30372 30373 30374 30375 30376 30377 30378 30379 30380 30381 30382 30383 30384 30385 30386 30387 30388 30389 30390 30391 30392 30393 30394 30395 30396 30397 30398 30399 30400 30401 30402 30403 30404 30405 30406 30407 30408 30409 30410 30411 30412 30413 30414 30415 30416 30417 30418 30419 30420 30421 30422 30423 30424 30425 30426 30427 30428 30429 30430 30431 30432 30433 30434 30435 30436 30437 30438 30439 30440 30441 30442 30443 30444 30445 30446 30447 30448 30449 30450 30451 30452 30453 30454 30455 30456 30457 30458 30459 30460 30461 30462 30463 30464 30465 30466 30467 30468 30469 30470 30471 30472 30473 30474 30475 30476 30477 30478 30479 30480 30481 30482 30483 30484 30485 30486 30487 30488 30489 30490 30491 30492 30493 30494 30495 30496 30497 30498 30499 30500 30501 30502 30503 30504 30505 30506 30507 30508 30509 30510 30511 30512 30513 30514 30515 30516 30517 30518 30519 30520 30521 30522 30523 30524 30525 30526 30527 30528 30529 30530 30531 30532 30533 30534 30535 30536 30537 30538 30539 30540 30541 30542 30543 30544 30545 30546 30547 30548 30549 30550 30551 30552 30553 30554 30555 30556 30557 30558 30559 30560 30561 30562 30563 30564 30565 30566 30567 30568 30569 30570 30571 30572 30573 30574 30575 30576 30577 30578 30579 30580 30581 30582 30583 30584 30585 30586 30587 30588 30589 30590 30591 30592 30593 30594 30595 30596 30597 30598 30599 30600 30601 30602 30603 30604 30605 30606 30607 30608 30609 30610 30611 30612 30613 30614 30615 30616 30617 30618 30619 30620 30621 30622 30623 30624 30625 30626 30627 30628 30629 30630 30631 30632 30633 30634 30635 30636 30637 30638 30639 30640 30641 30642 30643 30644 30645 30646 30647 30648 30649 30650 30651 30652 30653 30654 30655 30656 30657 30658 30659 30660 30661 30662 30663 30664 30665 30666 30667 30668 30669 30670 30671 30672 30673 30674 30675 30676 30677 30678 30679 30680 30681 30682 30683 30684 30685 30686 30687 30688 30689 30690 30691 30692 30693 30694 30695 30696 30697 30698 30699 30700 30701 30702 30703 30704 30705 30706 30707 30708 30709 30710 30711 30712 30713 30714 30715 30716 30717 30718 30719 30720 30721 30722 30723 30724 30725 30726 30727 30728 30729 30730 30731 30732 30733 30734 30735 30736 30737 30738 30739 30740 30741 30742 30743 30744 30745 30746 30747 30748 30749 30750 30751 30752 30753 30754 30755 30756 30757 30758 30759 30760 30761 30762 30763 30764 30765 30766 30767 30768 30769 30770 30771 30772 30773 30774 30775 30776 30777 30778 30779 30780 30781 30782 30783 30784 30785 30786 30787 30788 30789 30790 30791 30792 30793 30794 30795 30796 30797 30798 30799 30800 30801 30802 30803 30804 30805 30806 30807 30808 30809 30810 30811 30812 30813 30814 30815 30816 30817 30818 30819 30820 30821 30822 30823 30824 30825 30826 30827 30828 30829 30830 30831 30832 30833 30834 30835 30836 30837 30838 30839 30840 30841 30842 30843 30844 30845 30846 30847 30848 30849 30850 30851 30852 30853 30854 30855 30856 30857 30858 30859 30860 30861 30862 30863 30864 30865 30866 30867 30868 30869 30870 30871 30872 30873 30874 30875 30876 30877 30878 30879 30880 30881 30882 30883 30884 30885 30886 30887 30888 30889 30890 30891 30892 30893 30894 30895 30896 30897 30898 30899 30900 30901 30902 30903 30904 30905 30906 30907 30908 30909 30910 30911 30912 30913 30914 30915 30916 30917 30918 30919 30920 30921 30922 30923 30924 30925 30926 30927 30928 30929 30930 30931 30932 30933 30934 30935 30936 30937 30938 30939 30940 30941 30942 30943 30944 30945 30946 30947 30948 30949 30950 30951 30952 30953 30954 30955 30956 30957 30958 30959 30960 30961 30962 30963 30964 30965 30966 30967 30968 30969 30970 30971 30972 30973 30974 30975 30976 30977 30978 30979 30980 30981 30982 30983 30984 30985 30986 30987 30988 30989 30990 30991 30992 30993 30994 30995 30996 30997 30998 30999 31000 31001 31002 31003 31004 31005 31006 31007 31008 31009 31010 31011 31012 31013 31014 31015 31016 31017 31018 31019 31020 31021 31022 31023 31024 31025 31026 31027 31028 31029 31030 31031 31032 31033 31034 31035 31036 31037 31038 31039 31040 31041 31042 31043 31044 31045 31046 31047 31048 31049 31050 31051 31052 31053 31054 31055 31056 31057 31058 31059 31060 31061 31062 31063 31064 31065 31066 31067 31068 31069 31070 31071 31072 31073 31074 31075 31076 31077 31078 31079 31080 31081 31082 31083 31084 31085 31086 31087 31088 31089 31090 31091 31092 31093 31094 31095 31096 31097 31098 31099 31100 31101 31102 31103 31104 31105 31106 31107 31108 31109 31110 31111 31112 31113 31114 31115 31116 31117 31118 31119 31120 31121 31122 31123 31124 31125 31126 31127 31128 31129 31130 31131 31132 31133 31134 31135 31136 31137 31138 31139 31140 31141 31142 31143 31144 31145 31146 31147 31148 31149 31150 31151 31152 31153 31154 31155 31156 31157 31158 31159 31160 31161 31162 31163 31164 31165 31166 31167 31168 31169 31170 31171 31172 31173 31174 31175 31176 31177 31178 31179 31180 31181 31182 31183 31184 31185 31186 31187 31188 31189 31190 31191 31192 31193 31194 31195 31196 31197 31198 31199 31200 31201 31202 31203 31204 31205 31206 31207 31208 31209 31210 31211 31212 31213 31214 31215 31216 31217 31218 31219 31220 31221 31222 31223 31224 31225 31226 31227 31228 31229 31230 31231 31232 31233 31234 31235 31236 31237 31238 31239 31240 31241 31242 31243 31244 31245 31246 31247 31248 31249 31250 31251 31252 31253 31254 31255 31256 31257 31258 31259 31260 31261 31262 31263 31264 31265 31266 31267 31268 31269 31270 31271 31272 31273 31274 31275 31276 31277 31278 31279 31280 31281 31282 31283 31284 31285 31286 31287 31288 31289 31290 31291 31292 31293 31294 31295 31296 31297 31298 31299 31300 31301 31302 31303 31304 31305 31306 31307 31308 31309 31310 31311 31312 31313 31314 31315 31316 31317 31318 31319 31320 31321 31322 31323 31324 31325 31326 31327 31328 31329 31330 31331 31332 31333 31334 31335 31336 31337 31338 31339 31340 31341 31342 31343 31344 31345 31346 31347 31348 31349 31350 31351 31352 31353 31354 31355 31356 31357 31358 31359 31360 31361 31362 31363 31364 31365 31366 31367 31368 31369 31370 31371 31372 31373 31374 31375 31376 31377 31378 31379 31380 31381 31382 31383 31384 31385 31386 31387 31388 31389 31390 31391 31392 31393 31394 31395 31396 31397 31398 31399 31400 31401 31402 31403 31404 31405 31406 31407 31408 31409 31410 31411 31412 31413 31414 31415 31416 31417 31418 31419 31420 31421 31422 31423 31424 31425 31426 31427 31428 31429 31430 31431 31432 31433 31434 31435 31436 31437 31438 31439 31440 31441 31442 31443 31444 31445 31446 31447 31448 31449 31450 31451 31452 31453 31454 31455 31456 31457 31458 31459 31460 31461 31462 31463 31464 31465 31466 31467 31468 31469 31470 31471 31472 31473 31474 31475 31476 31477 31478 31479 31480 31481 31482 31483 31484 31485 31486 31487 31488 31489 31490 31491 31492 31493 31494 31495 31496 31497 31498 31499 31500 31501 31502 31503 31504 31505 31506 31507 31508 31509 31510 31511 31512 31513 31514 31515 31516 31517 31518 31519 31520 31521 31522 31523 31524 31525 31526 31527 31528 31529 31530 31531 31532 31533 31534 31535 31536 31537 31538 31539 31540 31541 31542 31543 31544 31545 31546 31547 31548 31549 31550 31551 31552 31553 31554 31555 31556 31557 31558 31559 31560 31561 31562 31563 31564 31565 31566 31567 31568 31569 31570 31571 31572 31573 31574 31575 31576 31577 31578 31579 31580 31581 31582 31583 31584 31585 31586 31587 31588 31589 31590 31591 31592 31593 31594 31595 31596 31597 31598 31599 31600 31601 31602 31603 31604 31605 31606 31607 31608 31609 31610 31611 31612 31613 31614 31615 31616 31617 31618 31619 31620 31621 31622 31623 31624 31625 31626 31627 31628 31629 31630 31631 31632 31633 31634 31635 31636 31637 31638 31639 31640 31641 31642 31643 31644 31645 31646 31647 31648 31649 31650 31651 31652 31653 31654 31655 31656 31657 31658 31659 31660 31661 31662 31663 31664 31665 31666 31667 31668 31669 31670 31671 31672 31673 31674 31675 31676 31677 31678 31679 31680 31681 31682 31683 31684 31685 31686 31687 31688 31689 31690 31691 31692 31693 31694 31695 31696 31697 31698 31699 31700 31701 31702 31703 31704 31705 31706 31707 31708 31709 31710 31711 31712 31713 31714 31715 31716 31717 31718 31719 31720 31721 31722 31723 31724 31725 31726 31727 31728 31729 31730 31731 31732 31733 31734 31735 31736 31737 31738 31739 31740 31741 31742 31743 31744 31745 31746 31747 31748 31749 31750 31751 31752 31753 31754 31755 31756 31757 31758 31759 31760 31761 31762 31763 31764 31765 31766 31767 31768 31769 31770 31771 31772 31773 31774 31775 31776 31777 31778 31779 31780 31781 31782 31783 31784 31785 31786 31787 31788 31789 31790 31791 31792 31793 31794 31795 31796 31797 31798 31799 31800 31801 31802 31803 31804 31805 31806 31807 31808 31809 31810 31811 31812 31813 31814 31815 31816 31817 31818 31819 31820 31821 31822 31823 31824 31825 31826 31827 31828 31829 31830 31831 31832 31833 31834 31835 31836 31837 31838 31839 31840 31841 31842 31843 31844 31845 31846 31847 31848 31849 31850 31851 31852 31853 31854 31855 31856 31857 31858 31859 31860 31861 31862 31863 31864 31865 31866 31867 31868 31869 31870 31871 31872 31873 31874 31875 31876 31877 31878 31879 31880 31881 31882 31883 31884 31885 31886 31887 31888 31889 31890 31891 31892 31893 31894 31895 31896 31897 31898 31899 31900 31901 31902 31903 31904 31905 31906 31907 31908 31909 31910 31911 31912 31913 31914 31915 31916 31917 31918 31919 31920 31921 31922 31923 31924 31925 31926 31927 31928 31929 31930 31931 31932 31933 31934 31935 31936 31937 31938 31939 31940 31941 31942 31943 31944 31945 31946 31947 31948 31949 31950 31951 31952 31953 31954 31955 31956 31957 31958 31959 31960 31961 31962 31963 31964 31965 31966 31967 31968 31969 31970 31971 31972 31973 31974 31975 31976 31977 31978 31979 31980 31981 31982 31983 31984 31985 31986 31987 31988 31989 31990 31991 31992 31993 31994 31995 31996 31997 31998 31999 32000 32001 32002 32003 32004 32005 32006 32007 32008 32009 32010 32011 32012 32013 32014 32015 32016 32017 32018 32019 32020 32021 32022 32023 32024 32025 32026 32027 32028 32029 32030 32031 32032 32033 32034 32035 32036 32037 32038 32039 32040 32041 32042 32043 32044 32045 32046 32047 32048 32049 32050 32051 32052 32053 32054 32055 32056 32057 32058 32059 32060 32061 32062 32063 32064 32065 32066 32067 32068 32069 32070 32071 32072 32073 32074 32075 32076 32077 32078 32079 32080 32081 32082 32083 32084 32085 32086 32087 32088 32089 32090 32091 32092 32093 32094 32095 32096 32097 32098 32099 32100 32101 32102 32103 32104 32105 32106 32107 32108 32109 32110 32111 32112 32113 32114 32115 32116 32117 32118 32119 32120 32121 32122 32123 32124 32125 32126 32127 32128 32129 32130 32131 32132 32133 32134 32135 32136 32137 32138 32139 32140 32141 32142 32143 32144 32145 32146 32147 32148 32149 32150 32151 32152 32153 32154 32155 32156 32157 32158 32159 32160 32161 32162 32163 32164 32165 32166 32167 32168 32169 32170 32171 32172 32173 32174 32175 32176 32177 32178 32179 32180 32181 32182 32183 32184 32185 32186 32187 32188 32189 32190 32191 32192 32193 32194 32195 32196 32197 32198 32199 32200 32201 32202 32203 32204 32205 32206 32207 32208 32209 32210 32211 32212 32213 32214 32215 32216 32217 32218 32219 32220 32221 32222 32223 32224 32225 32226 32227 32228 32229 32230 32231 32232 32233 32234 32235 32236 32237 32238 32239 32240 32241 32242 32243 32244 32245 32246 32247 32248 32249 32250 32251 32252 32253 32254 32255 32256 32257 32258 32259 32260 32261 32262 32263 32264 32265 32266 32267 32268 32269 32270 32271 32272 32273 32274 32275 32276 32277 32278 32279 32280 32281 32282 32283 32284 32285 32286 32287 32288 32289 32290 32291 32292 32293 32294 32295 32296 32297 32298 32299 32300 32301 32302 32303 32304 32305 32306 32307 32308 32309 32310 32311 32312 32313 32314 32315 32316 32317 32318 32319 32320 32321 32322 32323 32324 32325 32326 32327 32328 32329 32330 32331 32332 32333 32334 32335 32336 32337 32338 32339 32340 32341 32342 32343 32344 32345 32346 32347 32348 32349 32350 32351 32352 32353 32354 32355 32356 32357 32358 32359 32360 32361 32362 32363 32364 32365 32366 32367 32368 32369 32370 32371 32372 32373 32374 32375 32376 32377 32378 32379 32380 32381 32382 32383 32384 32385 32386 32387 32388 32389 32390 32391 32392 32393 32394 32395 32396 32397 32398 32399 32400 32401 32402 32403 32404 32405 32406 32407 32408 32409 32410 32411 32412 32413 32414 32415 32416 32417 32418 32419 32420 32421 32422 32423 32424 32425 32426 32427 32428 32429 32430 32431 32432 32433 32434 32435 32436 32437 32438 32439 32440 32441 32442 32443 32444 32445 32446 32447 32448 32449 32450 32451 32452 32453 32454 32455 32456 32457 32458 32459 32460 32461 32462 32463 32464 32465 32466 32467 32468 32469 32470 32471 32472 32473 32474 32475 32476 32477 32478 32479 32480 32481 32482 32483 32484 32485 32486 32487 32488 32489 32490 32491 32492 32493 32494 32495 32496 32497 32498 32499 32500 32501 32502 32503 32504 32505 32506 32507 32508 32509 32510 32511 32512 32513 32514 32515 32516 32517 32518 32519 32520 32521 32522 32523 32524 32525 32526 32527 32528 32529 32530 32531 32532 32533 32534 32535 32536 32537 32538 32539 32540 32541 32542 32543 32544 32545 32546 32547 32548 32549 32550 32551 32552 32553 32554 32555 32556 32557 32558 32559 32560 32561 32562 32563 32564 32565 32566 32567 32568 32569 32570 32571 32572 32573 32574 32575 32576 32577 32578 32579 32580 32581 32582 32583 32584 32585 32586 32587 32588 32589 32590 32591 32592 32593 32594 32595 32596 32597 32598 32599 32600 32601 32602 32603 32604 32605 32606 32607 32608 32609 32610 32611 32612 32613 32614 32615 32616 32617 32618 32619 32620 32621 32622 32623 32624 32625 32626 32627 32628 32629 32630 32631 32632 32633 32634 32635 32636 32637 32638 32639 32640 32641 32642 32643 32644 32645 32646 32647 32648 32649 32650 32651 32652 32653 32654 32655 32656 32657 32658 32659 32660 32661 32662 32663 32664 32665 32666 32667 32668 32669 32670 32671 32672 32673 32674 32675 32676 32677 32678 32679 32680 32681 32682 32683 32684 32685 32686 32687 32688 32689 32690 32691 32692 32693 32694 32695 32696 32697 32698 32699 32700 32701 32702 32703 32704 32705 32706 32707 32708 32709 32710 32711 32712 32713 32714 32715 32716 32717 32718 32719 32720 32721 32722 32723 32724 32725 32726 32727 32728 32729 32730 32731 32732 32733 32734 32735 32736 32737 32738 32739 32740 32741 32742 32743 32744 32745 32746 32747 32748 32749 32750 32751 32752 32753 32754 32755 32756 32757 32758 32759 32760 32761 32762 32763 32764 32765 32766 32767 32768 32769 32770 32771 32772 32773 32774 32775 32776 32777 32778 32779 32780 32781 32782 32783 32784 32785 32786 32787 32788 32789 32790 32791 32792 32793 32794 32795 32796 32797 32798 32799 32800 32801 32802 32803 32804 32805 32806 32807 32808 32809 32810 32811 32812 32813 32814 32815 32816 32817 32818 32819 32820 32821 32822 32823 32824 32825 32826 32827 32828 32829 32830 32831 32832 32833 32834 32835 32836 32837 32838 32839 32840 32841 32842 32843 32844 32845 32846 32847 32848 32849 32850 32851 32852 32853 32854 32855 32856 32857 32858 32859 32860 32861 32862 32863 32864 32865 32866 32867 32868 32869 32870 32871 32872 32873 32874 32875 32876 32877 32878 32879 32880 32881 32882 32883 32884 32885 32886 32887 32888 32889 32890 32891 32892 32893 32894 32895 32896 32897 32898 32899 32900 32901 32902 32903 32904 32905 32906 32907 32908 32909 32910 32911 32912 32913 32914 32915 32916 32917 32918 32919 32920 32921 32922 32923 32924 32925 32926 32927 32928 32929 32930 32931 32932 32933 32934 32935 32936 32937 32938 32939 32940 32941 32942 32943 32944 32945 32946 32947 32948 32949 32950 32951 32952 32953 32954 32955 32956 32957 32958 32959 32960 32961 32962 32963 32964 32965 32966 32967 32968 32969 32970 32971 32972 32973 32974 32975 32976 32977 32978 32979 32980 32981 32982 32983 32984 32985 32986 32987 32988 32989 32990 32991 32992 32993 32994 32995 32996 32997 32998 32999 33000 33001 33002 33003 33004 33005 33006 33007 33008 33009 33010 33011 33012 33013 33014 33015 33016 33017 33018 33019 33020 33021 33022 33023 33024 33025 33026 33027 33028 33029 33030 33031 33032 33033 33034 33035 33036 33037 33038 33039 33040 33041 33042 33043 33044 33045 33046 33047 33048 33049 33050 33051 33052 33053 33054 33055 33056 33057 33058 33059 33060 33061 33062 33063 33064 33065 33066 33067 33068 33069 33070 33071 33072 33073 33074 33075 33076 33077 33078 33079 33080 33081 33082 33083 33084 33085 33086 33087 33088 33089 33090 33091 33092 33093 33094 33095 33096 33097 33098 33099 33100 33101 33102 33103 33104 33105 33106 33107 33108 33109 33110 33111 33112 33113 33114 33115 33116 33117 33118 33119 33120 33121 33122 33123 33124 33125 33126 33127 33128 33129 33130 33131 33132 33133 33134 33135 33136 33137 33138 33139 33140 33141 33142 33143 33144 33145 33146 33147 33148 33149 33150 33151 33152 33153 33154 33155 33156 33157 33158 33159 33160 33161 33162 33163 33164 33165 33166 33167 33168 33169 33170 33171 33172 33173 33174 33175 33176 33177 33178 33179 33180 33181 33182 33183 33184 33185 33186 33187 33188 33189 33190 33191 33192 33193 33194 33195 33196 33197 33198 33199 33200 33201 33202 33203 33204 33205 33206 33207 33208 33209 33210 33211 33212 33213 33214 33215 33216 33217 33218 33219 33220 33221 33222 33223 33224 33225 33226 33227 33228 33229 33230 33231 33232 33233 33234 33235 33236 33237 33238 33239 33240 33241 33242 33243 33244 33245 33246 33247 33248 33249 33250 33251 33252 33253 33254 33255 33256 33257 33258 33259 33260 33261 33262 33263 33264 33265 33266 33267 33268 33269 33270 33271 33272 33273 33274 33275 33276 33277 33278 33279 33280 33281 33282 33283 33284 33285 33286 33287 33288 33289 33290 33291 33292 33293 33294 33295 33296 33297 33298 33299 33300 33301 33302 33303 33304 33305 33306 33307 33308 33309 33310 33311 33312 33313 33314 33315 33316 33317 33318 33319 33320 33321 33322 33323 33324 33325 33326 33327 33328 33329 33330 33331 33332 33333 33334 33335 33336 33337 33338 33339 33340 33341 33342 33343 33344 33345 33346 33347 33348 33349 33350 33351 33352 33353 33354 33355 33356 33357 33358 33359 33360 33361 33362 33363 33364 33365 33366 33367 33368 33369 33370 33371 33372 33373 33374 33375 33376 33377 33378 33379 33380 33381 33382 33383 33384 33385 33386 33387 33388 33389 33390 33391 33392 33393 33394 33395 33396 33397 33398 33399 33400 33401 33402 33403 33404 33405 33406 33407 33408 33409 33410 33411 33412 33413 33414 33415 33416 33417 33418 33419 33420 33421 33422 33423 33424 33425 33426 33427 33428 33429 33430 33431 33432 33433 33434 33435 33436 33437 33438 33439 33440 33441 33442 33443 33444 33445 33446 33447 33448 33449 33450 33451 33452 33453 33454 33455 33456 33457 33458 33459 33460 33461 33462 33463 33464 33465 33466 33467 33468 33469 33470 33471 33472 33473 33474 33475 33476 33477 33478 33479 33480 33481 33482 33483 33484 33485 33486 33487 33488 33489 33490 33491 33492 33493 33494 33495 33496 33497 33498 33499 33500 33501 33502 33503 33504 33505 33506 33507 33508 33509 33510 33511 33512 33513 33514 33515 33516 33517 33518 33519 33520 33521 33522 33523 33524 33525 33526 33527 33528 33529 33530 33531 33532 33533 33534 33535 33536 33537 33538 33539 33540 33541 33542 33543 33544 33545 33546 33547 33548 33549 33550 33551 33552 33553 33554 33555 33556 33557 33558 33559 33560 33561 33562 33563 33564 33565 33566 33567 33568 33569 33570 33571 33572 33573 33574 33575 33576 33577 33578 33579 33580 33581 33582 33583 33584 33585 33586 33587 33588 33589 33590 33591 33592 33593 33594 33595 33596 33597 33598 33599 33600 33601 33602 33603 33604 33605 33606 33607 33608 33609 33610 33611 33612 33613 33614 33615 33616 33617 33618 33619 33620 33621 33622 33623 33624 33625 33626 33627 33628 33629 33630 33631 33632 33633 33634 33635 33636 33637 33638 33639 33640 33641 33642 33643 33644 33645 33646 33647 33648 33649 33650 33651 33652 33653 33654 33655 33656 33657 33658 33659 33660 33661 33662 33663 33664 33665 33666 33667 33668 33669 33670 33671 33672 33673 33674 33675 33676 33677 33678 33679 33680 33681 33682 33683 33684 33685 33686 33687 33688 33689 33690 33691 33692 33693 33694 33695 33696 33697 33698 33699 33700 33701 33702 33703 33704 33705 33706 33707 33708 33709 33710 33711 33712 33713 33714 33715 33716 33717 33718 33719 33720 33721 33722 33723 33724 33725 33726 33727 33728 33729 33730 33731 33732 33733 33734 33735 33736 33737 33738 33739 33740 33741 33742 33743 33744 33745 33746 33747 33748 33749 33750 33751 33752 33753 33754 33755 33756 33757 33758 33759 33760 33761 33762 33763 33764 33765 33766 33767 33768 33769 33770 33771 33772 33773 33774 33775 33776 33777 33778 33779 33780 33781 33782 33783 33784 33785 33786 33787 33788 33789 33790 33791 33792 33793 33794 33795 33796 33797 33798 33799 33800 33801 33802 33803 33804 33805 33806 33807 33808 33809 33810 33811 33812 33813 33814 33815 33816 33817 33818 33819 33820 33821 33822 33823 33824 33825 33826 33827 33828 33829 33830 33831 33832 33833 33834 33835 33836 33837 33838 33839 33840 33841 33842 33843 33844 33845 33846 33847 33848 33849 33850 33851 33852 33853 33854 33855 33856 33857 33858 33859 33860 33861 33862 33863 33864 33865 33866 33867 33868 33869 33870 33871 33872 33873 33874 33875 33876 33877 33878 33879 33880 33881 33882 33883 33884 33885 33886 33887 33888 33889 33890 33891 33892 33893 33894 33895 33896 33897 33898 33899 33900 33901 33902 33903 33904 33905 33906 33907 33908 33909 33910 33911 33912 33913 33914 33915 33916 33917 33918 33919 33920 33921 33922 33923 33924 33925 33926 33927 33928 33929 33930 33931 33932 33933 33934 33935 33936 33937 33938 33939 33940 33941 33942 33943 33944 33945 33946 33947 33948 33949 33950 33951 33952 33953 33954 33955 33956 33957 33958 33959 33960 33961 33962 33963 33964 33965 33966 33967 33968 33969 33970 33971 33972 33973 33974 33975 33976 33977 33978 33979 33980 33981 33982 33983 33984 33985 33986 33987 33988 33989 33990 33991 33992 33993 33994 33995 33996 33997 33998 33999 34000 34001 34002 34003 34004 34005 34006 34007 34008 34009 34010 34011 34012 34013 34014 34015 34016 34017 34018 34019 34020 34021 34022 34023 34024 34025 34026 34027 34028 34029 34030 34031 34032 34033 34034 34035 34036 34037 34038 34039 34040 34041 34042 34043 34044 34045 34046 34047 34048 34049 34050 34051 34052 34053 34054 34055 34056 34057 34058 34059 34060 34061 34062 34063 34064 34065 34066 34067 34068 34069 34070 34071 34072 34073 34074 34075 34076 34077 34078 34079 34080 34081 34082 34083 34084 34085 34086 34087 34088 34089 34090 34091 34092 34093 34094 34095 34096 34097 34098 34099 34100 34101 34102 34103 34104 34105 34106 34107 34108 34109 34110 34111 34112 34113 34114 34115 34116 34117 34118 34119 34120 34121 34122 34123 34124 34125 34126 34127 34128 34129 34130 34131 34132 34133 34134 34135 34136 34137 34138 34139 34140 34141 34142 34143 34144 34145 34146 34147 34148 34149 34150 34151 34152 34153 34154 34155 34156 34157 34158 34159 34160 34161 34162 34163 34164 34165 34166 34167 34168 34169 34170 34171 34172 34173 34174 34175 34176 34177 34178 34179 34180 34181 34182 34183 34184 34185 34186 34187 34188 34189 34190 34191 34192 34193 34194 34195 34196 34197 34198 34199 34200 34201 34202 34203 34204 34205 34206 34207 34208 34209 34210 34211 34212 34213 34214 34215 34216 34217 34218 34219 34220 34221 34222 34223 34224 34225 34226 34227 34228 34229 34230 34231 34232 34233 34234 34235 34236 34237 34238 34239 34240 34241 34242 34243 34244 34245 34246 34247 34248 34249 34250 34251 34252 34253 34254 34255 34256 34257 34258 34259 34260 34261 34262 34263 34264 34265 34266 34267 34268 34269 34270 34271 34272 34273 34274 34275 34276 34277 34278 34279 34280 34281 34282 34283 34284 34285 34286 34287 34288 34289 34290 34291 34292 34293 34294 34295 34296 34297 34298 34299 34300 34301 34302 34303 34304 34305 34306 34307 34308 34309 34310 34311 34312 34313 34314 34315 34316 34317 34318 34319 34320 34321 34322 34323 34324 34325 34326 34327 34328 34329 34330 34331 34332 34333 34334 34335 34336 34337 34338 34339 34340 34341 34342 34343 34344 34345 34346 34347 34348 34349 34350 34351 34352 34353 34354 34355 34356 34357 34358 34359 34360 34361 34362 34363 34364 34365 34366 34367 34368 34369 34370 34371 34372 34373 34374 34375 34376 34377 34378 34379 34380 34381 34382 34383 34384 34385 34386 34387 34388 34389 34390 34391 34392 34393 34394 34395 34396 34397 34398 34399 34400 34401 34402 34403 34404 34405 34406 34407 34408 34409 34410 34411 34412 34413 34414 34415 34416 34417 34418 34419 34420 34421 34422 34423 34424 34425 34426 34427 34428 34429 34430 34431 34432 34433 34434 34435 34436 34437 34438 34439 34440 34441 34442 34443 34444 34445 34446 34447 34448 34449 34450 34451 34452 34453 34454 34455 34456 34457 34458 34459 34460 34461 34462 34463 34464 34465 34466 34467 34468 34469 34470 34471 34472 34473 34474 34475 34476 34477 34478 34479 34480 34481 34482 34483 34484 34485 34486 34487 34488 34489 34490 34491 34492 34493 34494 34495 34496 34497 34498 34499 34500 34501 34502 34503 34504 34505 34506 34507 34508 34509 34510 34511 34512 34513 34514 34515 34516 34517 34518 34519 34520 34521 34522 34523 34524 34525 34526 34527 34528 34529 34530 34531 34532 34533 34534 34535 34536 34537 34538 34539 34540 34541 34542 34543 34544 34545 34546 34547 34548 34549 34550 34551 34552 34553 34554 34555 34556 34557 34558 34559 34560 34561 34562 34563 34564 34565 34566 34567 34568 34569 34570 34571 34572 34573 34574 34575 34576 34577 34578 34579 34580 34581 34582 34583 34584 34585 34586 34587 34588 34589 34590 34591 34592 34593 34594 34595 34596 34597 34598 34599 34600 34601 34602 34603 34604 34605 34606 34607 34608 34609 34610 34611 34612 34613 34614 34615 34616 34617 34618 34619 34620 34621 34622 34623 34624 34625 34626 34627 34628 34629 34630 34631 34632 34633 34634 34635 34636 34637 34638 34639 34640 34641 34642 34643 34644 34645 34646 34647 34648 34649 34650 34651 34652 34653 34654 34655 34656 34657 34658 34659 34660 34661 34662 34663 34664 34665 34666 34667 34668 34669 34670 34671 34672 34673 34674 34675 34676 34677 34678 34679 34680 34681 34682 34683 34684 34685 34686 34687 34688 34689 34690 34691 34692 34693 34694 34695 34696 34697 34698 34699 34700 34701 34702 34703 34704 34705 34706 34707 34708 34709 34710 34711 34712 34713 34714 34715 34716 34717 34718 34719 34720 34721 34722 34723 34724 34725 34726 34727 34728 34729 34730 34731 34732 34733 34734 34735 34736 34737 34738 34739 34740 34741 34742 34743 34744 34745 34746 34747 34748 34749 34750 34751 34752 34753 34754 34755 34756 34757 34758 34759 34760 34761 34762 34763 34764 34765 34766 34767 34768 34769 34770 34771 34772 34773 34774 34775 34776 34777 34778 34779 34780 34781 34782 34783 34784 34785 34786 34787 34788 34789 34790 34791 34792 34793 34794 34795 34796 34797 34798 34799 34800 34801 34802 34803 34804 34805 34806 34807 34808 34809 34810 34811 34812 34813 34814 34815 34816 34817 34818 34819 34820 34821 34822 34823 34824 34825 34826 34827 34828 34829 34830 34831 34832 34833 34834 34835 34836 34837 34838 34839 34840 34841 34842 34843 34844 34845 34846 34847 34848 34849 34850 34851 34852 34853 34854 34855 34856 34857 34858 34859 34860 34861 34862 34863 34864 34865 34866 34867 34868 34869 34870 34871 34872 34873 34874 34875 34876 34877 34878 34879 34880 34881 34882 34883 34884 34885 34886 34887 34888 34889 34890 34891 34892 34893 34894 34895 34896 34897 34898 34899 34900 34901 34902 34903 34904 34905 34906 34907 34908 34909 34910 34911 34912 34913 34914 34915 34916 34917 34918 34919 34920 34921 34922 34923 34924 34925 34926 34927 34928 34929 34930 34931 34932 34933 34934 34935 34936 34937 34938 34939 34940 34941 34942 34943 34944 34945 34946 34947 34948 34949 34950 34951 34952 34953 34954 34955 34956 34957 34958 34959 34960 34961 34962 34963 34964 34965 34966 34967 34968 34969 34970 34971 34972 34973 34974 34975 34976 34977 34978 34979 34980 34981 34982 34983 34984 34985 34986 34987 34988 34989 34990 34991 34992 34993 34994 34995 34996 34997 34998 34999 35000 35001 35002 35003 35004 35005 35006 35007 35008 35009 35010 35011 35012 35013 35014 35015 35016 35017 35018 35019 35020 35021 35022 35023 35024 35025 35026 35027 35028 35029 35030 35031 35032 35033 35034 35035 35036 35037 35038 35039 35040 35041 35042 35043 35044 35045 35046 35047 35048 35049 35050 35051 35052 35053 35054 35055 35056 35057 35058 35059 35060 35061 35062 35063 35064 35065 35066 35067 35068 35069 35070 35071 35072 35073 35074 35075 35076 35077 35078 35079 35080 35081 35082 35083 35084 35085 35086 35087 35088 35089 35090 35091 35092 35093 35094 35095 35096 35097 35098 35099 35100 35101 35102 35103 35104 35105 35106 35107 35108 35109 35110 35111 35112 35113 35114 35115 35116 35117 35118 35119 35120 35121 35122 35123 35124 35125 35126 35127 35128 35129 35130 35131 35132 35133 35134 35135 35136 35137 35138 35139 35140 35141 35142 35143 35144 35145 35146 35147 35148 35149 35150 35151 35152 35153 35154 35155 35156 35157 35158 35159 35160 35161 35162 35163 35164 35165 35166 35167 35168 35169 35170 35171 35172 35173 35174 35175 35176 35177 35178 35179 35180 35181 35182 35183 35184 35185 35186 35187 35188 35189 35190 35191 35192 35193 35194 35195 35196 35197 35198 35199 35200 35201 35202 35203 35204 35205 35206 35207 35208 35209 35210 35211 35212 35213 35214 35215 35216 35217 35218 35219 35220 35221 35222 35223 35224 35225 35226 35227 35228 35229 35230 35231 35232 35233 35234 35235 35236 35237 35238 35239 35240 35241 35242 35243 35244 35245 35246 35247 35248 35249 35250 35251 35252 35253 35254 35255 35256 35257 35258 35259 35260 35261 35262 35263 35264 35265 35266 35267 35268 35269 35270 35271 35272 35273 35274 35275 35276 35277 35278 35279 35280 35281 35282 35283 35284 35285 35286 35287 35288 35289 35290 35291 35292 35293 35294 35295 35296 35297 35298 35299 35300 35301 35302 35303 35304 35305 35306 35307 35308 35309 35310 35311 35312 35313 35314 35315 35316 35317 35318 35319 35320 35321 35322 35323 35324 35325 35326 35327 35328 35329 35330 35331 35332 35333 35334 35335 35336 35337 35338 35339 35340 35341 35342 35343 35344 35345 35346 35347 35348 35349 35350 35351 35352 35353 35354 35355 35356 35357 35358 35359 35360 35361 35362 35363 35364 35365 35366 35367 35368 35369 35370 35371 35372 35373 35374 35375 35376 35377 35378 35379 35380 35381 35382 35383 35384 35385 35386 35387 35388 35389 35390 35391 35392 35393 35394 35395 35396 35397 35398 35399 35400 35401 35402 35403 35404 35405 35406 35407 35408 35409 35410 35411 35412 35413 35414 35415 35416 35417 35418 35419 35420 35421 35422 35423 35424 35425 35426 35427 35428 35429 35430 35431 35432 35433 35434 35435 35436 35437 35438 35439 35440 35441 35442 35443 35444 35445 35446 35447 35448 35449 35450 35451 35452 35453 35454 35455 35456 35457 35458 35459 35460 35461 35462 35463 35464 35465 35466 35467 35468 35469 35470 35471 35472 35473 35474 35475 35476 35477 35478 35479 35480 35481 35482 35483 35484 35485 35486 35487 35488 35489 35490 35491 35492 35493 35494 35495 35496 35497 35498 35499 35500 35501 35502 35503 35504 35505 35506 35507 35508 35509 35510 35511 35512 35513 35514 35515 35516 35517 35518 35519 35520 35521 35522 35523 35524 35525 35526 35527 35528 35529 35530 35531 35532 35533 35534 35535 35536 35537 35538 35539 35540 35541 35542 35543 35544 35545 35546 35547 35548 35549 35550 35551 35552 35553 35554 35555 35556 35557 35558 35559 35560 35561 35562 35563 35564 35565 35566 35567 35568 35569 35570 35571 35572 35573 35574 35575 35576 35577 35578 35579 35580 35581 35582 35583 35584 35585 35586 35587 35588 35589 35590 35591 35592 35593 35594 35595 35596 35597 35598 35599 35600 35601 35602 35603 35604 35605 35606 35607 35608 35609 35610 35611 35612 35613 35614 35615 35616 35617 35618 35619 35620 35621 35622 35623 35624 35625 35626 35627 35628 35629 35630 35631 35632 35633 35634 35635 35636 35637 35638 35639 35640 35641 35642 35643 35644 35645 35646 35647 35648 35649 35650 35651 35652 35653 35654 35655 35656 35657 35658 35659 35660 35661 35662 35663 35664 35665 35666 35667 35668 35669 35670 35671 35672 35673 35674 35675 35676 35677 35678 35679 35680 35681 35682 35683 35684 35685 35686 35687 35688 35689 35690 35691 35692 35693 35694 35695 35696 35697 35698 35699 35700 35701 35702 35703 35704 35705 35706 35707 35708 35709 35710 35711 35712 35713 35714 35715 35716 35717 35718 35719 35720 35721 35722 35723 35724 35725 35726 35727 35728 35729 35730 35731 35732 35733 35734 35735 35736 35737 35738 35739 35740 35741 35742 35743 35744 35745 35746 35747 35748 35749 35750 35751 35752 35753 35754 35755 35756 35757 35758 35759 35760 35761 35762 35763 35764 35765 35766 35767 35768 35769 35770 35771 35772 35773 35774 35775 35776 35777 35778 35779 35780 35781 35782 35783 35784 35785 35786 35787 35788 35789 35790 35791 35792 35793 35794 35795 35796 35797 35798 35799 35800 35801 35802 35803 35804 35805 35806 35807 35808 35809 35810 35811 35812 35813 35814 35815 35816 35817 35818 35819 35820 35821 35822 35823 35824 35825 35826 35827 35828 35829 35830 35831 35832 35833 35834 35835 35836 35837 35838 35839 35840 35841 35842 35843 35844 35845 35846 35847 35848 35849 35850 35851 35852 35853 35854 35855 35856 35857 35858 35859 35860 35861 35862 35863 35864 35865 35866 35867 35868 35869 35870 35871 35872 35873 35874 35875 35876 35877 35878 35879 35880 35881 35882 35883 35884 35885 35886 35887 35888 35889 35890 35891 35892 35893 35894 35895 35896 35897 35898 35899 35900 35901 35902 35903 35904 35905 35906 35907 35908 35909 35910 35911 35912 35913 35914 35915 35916 35917 35918 35919 35920 35921 35922 35923 35924 35925 35926 35927 35928 35929 35930 35931 35932 35933 35934 35935 35936 35937 35938 35939 35940 35941 35942 35943 35944 35945 35946 35947 35948 35949 35950 35951 35952 35953 35954 35955 35956 35957 35958 35959 35960 35961 35962 35963 35964 35965 35966 35967 35968 35969 35970 35971 35972 35973 35974 35975 35976 35977 35978 35979 35980 35981 35982 35983 35984 35985 35986 35987 35988 35989 35990 35991 35992 35993 35994 35995 35996 35997 35998 35999 36000 36001 36002 36003 36004 36005 36006 36007 36008 36009 36010 36011 36012 36013 36014 36015 36016 36017 36018 36019 36020 36021 36022 36023 36024 36025 36026 36027 36028 36029 36030 36031 36032 36033 36034 36035 36036 36037 36038 36039 36040 36041 36042 36043 36044 36045 36046 36047 36048 36049 36050 36051 36052 36053 36054 36055 36056 36057 36058 36059 36060 36061 36062 36063 36064 36065 36066 36067 36068 36069 36070 36071 36072 36073 36074 36075 36076 36077 36078 36079 36080 36081 36082 36083 36084 36085 36086 36087 36088 36089 36090 36091 36092 36093 36094 36095 36096 36097 36098 36099 36100 36101 36102 36103 36104 36105 36106 36107 36108 36109 36110 36111 36112 36113 36114 36115 36116 36117 36118 36119 36120 36121 36122 36123 36124 36125 36126 36127 36128 36129 36130 36131 36132 36133 36134 36135 36136 36137 36138 36139 36140 36141 36142 36143 36144 36145 36146 36147 36148 36149 36150 36151 36152 36153 36154 36155 36156 36157 36158 36159 36160 36161 36162 36163 36164 36165 36166 36167 36168 36169 36170 36171 36172 36173 36174 36175 36176 36177 36178 36179 36180 36181 36182 36183 36184 36185 36186 36187 36188 36189 36190 36191 36192 36193 36194 36195 36196 36197 36198 36199 36200 36201 36202 36203 36204 36205 36206 36207 36208 36209 36210 36211 36212 36213 36214 36215 36216 36217 36218 36219 36220 36221 36222 36223 36224 36225 36226 36227 36228 36229 36230 36231 36232 36233 36234 36235 36236 36237 36238 36239 36240 36241 36242 36243 36244 36245 36246 36247 36248 36249 36250 36251 36252 36253 36254 36255 36256 36257 36258 36259 36260 36261 36262 36263 36264 36265 36266 36267 36268 36269 36270 36271 36272 36273 36274 36275 36276 36277 36278 36279 36280 36281 36282 36283 36284 36285 36286 36287 36288 36289 36290 36291 36292 36293 36294 36295 36296 36297 36298 36299 36300 36301 36302 36303 36304 36305 36306 36307 36308 36309 36310 36311 36312 36313 36314 36315 36316 36317 36318 36319 36320 36321 36322 36323 36324 36325 36326 36327 36328 36329 36330 36331 36332 36333 36334 36335 36336 36337 36338 36339 36340 36341 36342 36343 36344 36345 36346 36347 36348 36349 36350 36351 36352 36353 36354 36355 36356 36357 36358 36359 36360 36361 36362 36363 36364 36365 36366 36367 36368 36369 36370 36371 36372 36373 36374 36375 36376 36377 36378 36379 36380 36381 36382 36383 36384 36385 36386 36387 36388 36389 36390 36391 36392 36393 36394 36395 36396 36397 36398 36399 36400 36401 36402 36403 36404 36405 36406 36407 36408 36409 36410 36411 36412 36413 36414 36415 36416 36417 36418 36419 36420 36421 36422 36423 36424 36425 36426 36427 36428 36429 36430 36431 36432 36433 36434 36435 36436 36437 36438 36439 36440 36441 36442 36443 36444 36445 36446 36447 36448 36449 36450 36451 36452 36453 36454 36455 36456 36457 36458 36459 36460 36461 36462 36463 36464 36465 36466 36467 36468 36469 36470 36471 36472 36473 36474 36475 36476 36477 36478 36479 36480 36481 36482 36483 36484 36485 36486 36487 36488 36489 36490 36491 36492 36493 36494 36495 36496 36497 36498 36499 36500 36501 36502 36503 36504 36505 36506 36507 36508 36509 36510 36511 36512 36513 36514 36515 36516 36517 36518 36519 36520 36521 36522 36523 36524 36525 36526 36527 36528 36529 36530 36531 36532 36533 36534 36535 36536 36537 36538 36539 36540 36541 36542 36543 36544 36545 36546 36547 36548 36549 36550 36551 36552 36553 36554 36555 36556 36557 36558 36559 36560 36561 36562 36563 36564 36565 36566 36567 36568 36569 36570 36571 36572 36573 36574 36575 36576 36577 36578 36579 36580 36581 36582 36583 36584 36585 36586 36587 36588 36589 36590 36591 36592 36593 36594 36595 36596 36597 36598 36599 36600 36601 36602 36603 36604 36605 36606 36607 36608 36609 36610 36611 36612 36613 36614 36615 36616 36617 36618 36619 36620 36621 36622 36623 36624 36625 36626 36627 36628 36629 36630 36631 36632 36633 36634 36635 36636 36637 36638 36639 36640 36641 36642 36643 36644 36645 36646 36647 36648 36649 36650 36651 36652 36653 36654 36655 36656 36657 36658 36659 36660 36661 36662 36663 36664 36665 36666 36667 36668 36669 36670 36671 36672 36673 36674 36675 36676 36677 36678 36679 36680 36681 36682 36683 36684 36685 36686 36687 36688 36689 36690 36691 36692 36693 36694 36695 36696 36697 36698 36699 36700 36701 36702 36703 36704 36705 36706 36707 36708 36709 36710 36711 36712 36713 36714 36715 36716 36717 36718 36719 36720 36721 36722 36723 36724 36725 36726 36727 36728 36729 36730 36731 36732 36733 36734 36735 36736 36737 36738 36739 36740 36741 36742 36743 36744 36745 36746 36747 36748 36749 36750 36751 36752 36753 36754 36755 36756 36757 36758 36759 36760 36761 36762 36763 36764 36765 36766 36767 36768 36769 36770 36771 36772 36773 36774 36775 36776 36777 36778 36779 36780 36781 36782 36783 36784 36785 36786 36787 36788 36789 36790 36791 36792 36793 36794 36795 36796 36797 36798 36799 36800 36801 36802 36803 36804 36805 36806 36807 36808 36809 36810 36811 36812 36813 36814 36815 36816 36817 36818 36819 36820 36821 36822 36823 36824 36825 36826 36827 36828 36829 36830 36831 36832 36833 36834 36835 36836 36837 36838 36839 36840 36841 36842 36843 36844 36845 36846 36847 36848 36849 36850 36851 36852 36853 36854 36855 36856 36857 36858 36859 36860 36861 36862 36863 36864 36865 36866 36867 36868 36869 36870 36871 36872 36873 36874 36875 36876 36877 36878 36879 36880 36881 36882 36883 36884 36885 36886 36887 36888 36889 36890 36891 36892 36893 36894 36895 36896 36897 36898 36899 36900 36901 36902 36903 36904 36905 36906 36907 36908 36909 36910 36911 36912 36913 36914 36915 36916 36917 36918 36919 36920 36921 36922 36923 36924 36925 36926 36927 36928 36929 36930 36931 36932 36933 36934 36935 36936 36937 36938 36939 36940 36941 36942 36943 36944 36945 36946 36947 36948 36949 36950 36951 36952 36953 36954 36955 36956 36957 36958 36959 36960 36961 36962 36963 36964 36965 36966 36967 36968 36969 36970 36971 36972 36973 36974 36975 36976 36977 36978 36979 36980 36981 36982 36983 36984 36985 36986 36987 36988 36989 36990 36991 36992 36993 36994 36995 36996 36997 36998 36999 37000 37001 37002 37003 37004 37005 37006 37007 37008 37009 37010 37011 37012 37013 37014 37015 37016 37017 37018 37019 37020 37021 37022 37023 37024 37025 37026 37027 37028 37029 37030 37031 37032 37033 37034 37035 37036 37037 37038 37039 37040 37041 37042 37043 37044 37045 37046 37047 37048 37049 37050 37051 37052 37053 37054 37055 37056 37057 37058 37059 37060 37061 37062 37063 37064 37065 37066 37067 37068 37069 37070 37071 37072 37073 37074 37075 37076 37077 37078 37079 37080 37081 37082 37083 37084 37085 37086 37087 37088 37089 37090 37091 37092 37093 37094 37095 37096 37097 37098 37099 37100 37101 37102 37103 37104 37105 37106 37107 37108 37109 37110 37111 37112 37113 37114 37115 37116 37117 37118 37119 37120 37121 37122 37123 37124 37125 37126 37127 37128 37129 37130 37131 37132 37133 37134 37135 37136 37137 37138 37139 37140 37141 37142 37143 37144 37145 37146 37147 37148 37149 37150 37151 37152 37153 37154 37155 37156 37157 37158 37159 37160 37161 37162 37163 37164 37165 37166 37167 37168 37169 37170 37171 37172 37173 37174 37175 37176 37177 37178 37179 37180 37181 37182 37183 37184 37185 37186 37187 37188 37189 37190 37191 37192 37193 37194 37195 37196 37197 37198 37199 37200 37201 37202 37203 37204 37205 37206 37207 37208 37209 37210 37211 37212 37213 37214 37215 37216 37217 37218 37219 37220 37221 37222 37223 37224 37225 37226 37227 37228 37229 37230 37231 37232 37233 37234 37235 37236 37237 37238 37239 37240 37241 37242 37243 37244 37245 37246 37247 37248 37249 37250 37251 37252 37253 37254 37255 37256 37257 37258 37259 37260 37261 37262 37263 37264 37265 37266 37267 37268 37269 37270 37271 37272 37273 37274 37275 37276 37277 37278 37279 37280 37281 37282 37283 37284 37285 37286 37287 37288 37289 37290 37291 37292 37293 37294 37295 37296 37297 37298 37299 37300 37301 37302 37303 37304 37305 37306 37307 37308 37309 37310 37311 37312 37313 37314 37315 37316 37317 37318 37319 37320 37321 37322 37323 37324 37325 37326 37327 37328 37329 37330 37331 37332 37333 37334 37335 37336 37337 37338 37339 37340 37341 37342 37343 37344 37345 37346 37347 37348 37349 37350 37351 37352 37353 37354 37355 37356 37357 37358 37359 37360 37361 37362 37363 37364 37365 37366 37367 37368 37369 37370 37371 37372 37373 37374 37375 37376 37377 37378 37379 37380 37381 37382 37383 37384 37385 37386 37387 37388 37389 37390 37391 37392 37393 37394 37395 37396 37397 37398 37399 37400 37401 37402 37403 37404 37405 37406 37407 37408 37409 37410 37411 37412 37413 37414 37415 37416 37417 37418 37419 37420 37421 37422 37423 37424 37425 37426 37427 37428 37429 37430 37431 37432 37433 37434 37435 37436 37437 37438 37439 37440 37441 37442 37443 37444 37445 37446 37447 37448 37449 37450 37451 37452 37453 37454 37455 37456 37457 37458 37459 37460 37461 37462 37463 37464 37465 37466 37467 37468 37469 37470 37471 37472 37473 37474 37475 37476 37477 37478 37479 37480 37481 37482 37483 37484 37485 37486 37487 37488 37489 37490 37491 37492 37493 37494 37495 37496 37497 37498 37499 37500 37501 37502 37503 37504 37505 37506 37507 37508 37509 37510 37511 37512 37513 37514 37515 37516 37517 37518 37519 37520 37521 37522 37523 37524 37525 37526 37527 37528 37529 37530 37531 37532 37533 37534 37535 37536 37537 37538 37539 37540 37541 37542 37543 37544 37545 37546 37547 37548 37549 37550 37551 37552 37553 37554 37555 37556 37557 37558 37559 37560 37561 37562 37563 37564 37565 37566 37567 37568 37569 37570 37571 37572 37573 37574 37575 37576 37577 37578 37579 37580 37581 37582 37583 37584 37585 37586 37587 37588 37589 37590 37591 37592 37593 37594 37595 37596 37597 37598 37599 37600 37601 37602 37603 37604 37605 37606 37607 37608 37609 37610 37611 37612 37613 37614 37615 37616 37617 37618 37619 37620 37621 37622 37623 37624 37625 37626 37627 37628 37629 37630 37631 37632 37633 37634 37635 37636 37637 37638 37639 37640 37641 37642 37643 37644 37645 37646 37647 37648 37649 37650 37651 37652 37653 37654 37655 37656 37657 37658 37659 37660 37661 37662 37663 37664 37665 37666 37667 37668 37669 37670 37671 37672 37673 37674 37675 37676 37677 37678 37679 37680 37681 37682 37683 37684 37685 37686 37687 37688 37689 37690 37691 37692 37693 37694 37695 37696 37697 37698 37699 37700 37701 37702 37703 37704 37705 37706 37707 37708 37709 37710 37711 37712 37713 37714 37715 37716 37717 37718 37719 37720 37721 37722 37723 37724 37725 37726 37727 37728 37729 37730 37731 37732 37733 37734 37735 37736 37737 37738 37739 37740 37741 37742 37743 37744 37745 37746 37747 37748 37749 37750 37751 37752 37753 37754 37755 37756 37757 37758 37759 37760 37761 37762 37763 37764 37765 37766 37767 37768 37769 37770 37771 37772 37773 37774 37775 37776 37777 37778 37779 37780 37781 37782 37783 37784 37785 37786 37787 37788 37789 37790 37791 37792 37793 37794 37795 37796 37797 37798 37799 37800 37801 37802 37803 37804 37805 37806 37807 37808 37809 37810 37811 37812 37813 37814 37815 37816 37817 37818 37819 37820 37821 37822 37823 37824 37825 37826 37827 37828 37829 37830 37831 37832 37833 37834 37835 37836 37837 37838 37839 37840 37841 37842 37843 37844 37845 37846 37847 37848 37849 37850 37851 37852 37853 37854 37855 37856 37857 37858 37859 37860 37861 37862 37863 37864 37865 37866 37867 37868 37869 37870 37871 37872 37873 37874 37875 37876 37877 37878 37879 37880 37881 37882 37883 37884 37885 37886 37887 37888 37889 37890 37891 37892 37893 37894 37895 37896 37897 37898 37899 37900 37901 37902 37903 37904 37905 37906 37907 37908 37909 37910 37911 37912 37913 37914 37915 37916 37917 37918 37919 37920 37921 37922 37923 37924 37925 37926 37927 37928 37929 37930 37931 37932 37933 37934 37935 37936 37937 37938 37939 37940 37941 37942 37943 37944 37945 37946 37947 37948 37949 37950 37951 37952 37953 37954 37955 37956 37957 37958 37959 37960 37961 37962 37963 37964 37965 37966 37967 37968 37969 37970 37971 37972 37973 37974 37975 37976 37977 37978 37979 37980 37981 37982 37983 37984 37985 37986 37987 37988 37989 37990 37991 37992 37993 37994 37995 37996 37997 37998 37999 38000 38001 38002 38003 38004 38005 38006 38007 38008 38009 38010 38011 38012 38013 38014 38015 38016 38017 38018 38019 38020 38021 38022 38023 38024 38025 38026 38027 38028 38029 38030 38031 38032 38033 38034 38035 38036 38037 38038 38039 38040 38041 38042 38043 38044 38045 38046 38047 38048 38049 38050 38051 38052 38053 38054 38055 38056 38057 38058 38059 38060 38061 38062 38063 38064 38065 38066 38067 38068 38069 38070 38071 38072 38073 38074 38075 38076 38077 38078 38079 38080 38081 38082 38083 38084 38085 38086 38087 38088 38089 38090 38091 38092 38093 38094 38095 38096 38097 38098 38099 38100 38101 38102 38103 38104 38105 38106 38107 38108 38109 38110 38111 38112 38113 38114 38115 38116 38117 38118 38119 38120 38121 38122 38123 38124 38125 38126 38127 38128 38129 38130 38131 38132 38133 38134 38135 38136 38137 38138 38139 38140 38141 38142 38143 38144 38145 38146 38147 38148 38149 38150 38151 38152 38153 38154 38155 38156 38157 38158 38159 38160 38161 38162 38163 38164 38165 38166 38167 38168 38169 38170 38171 38172 38173 38174 38175 38176 38177 38178 38179 38180 38181 38182 38183 38184 38185 38186 38187 38188 38189 38190 38191 38192 38193 38194 38195 38196 38197 38198 38199 38200 38201 38202 38203 38204 38205 38206 38207 38208 38209 38210 38211 38212 38213 38214 38215 38216 38217 38218 38219 38220 38221 38222 38223 38224 38225 38226 38227 38228 38229 38230 38231 38232 38233 38234 38235 38236 38237 38238 38239 38240 38241 38242 38243 38244 38245 38246 38247 38248 38249 38250 38251 38252 38253 38254 38255 38256 38257 38258 38259 38260 38261 38262 38263 38264 38265 38266 38267 38268 38269 38270 38271 38272 38273 38274 38275 38276 38277 38278 38279 38280 38281 38282 38283 38284 38285 38286 38287 38288 38289 38290 38291 38292 38293 38294 38295 38296 38297 38298 38299 38300 38301 38302 38303 38304 38305 38306 38307 38308 38309 38310 38311 38312 38313 38314 38315 38316 38317 38318 38319 38320 38321 38322 38323 38324 38325 38326 38327 38328 38329 38330 38331 38332 38333 38334 38335 38336 38337 38338 38339 38340 38341 38342 38343 38344 38345 38346 38347 38348 38349 38350 38351 38352 38353 38354 38355 38356 38357 38358 38359 38360 38361 38362 38363 38364 38365 38366 38367 38368 38369 38370 38371 38372 38373 38374 38375 38376 38377 38378 38379 38380 38381 38382 38383 38384 38385 38386 38387 38388 38389 38390 38391 38392 38393 38394 38395 38396 38397 38398 38399 38400 38401 38402 38403 38404 38405 38406 38407 38408 38409 38410 38411 38412 38413 38414 38415 38416 38417 38418 38419 38420 38421 38422 38423 38424 38425 38426 38427 38428 38429 38430 38431 38432 38433 38434 38435 38436 38437 38438 38439 38440 38441 38442 38443 38444 38445 38446 38447 38448 38449 38450 38451 38452 38453 38454 38455 38456 38457 38458 38459 38460 38461 38462 38463 38464 38465 38466 38467 38468 38469 38470 38471 38472 38473 38474 38475 38476 38477 38478 38479 38480 38481 38482 38483 38484 38485 38486 38487 38488 38489 38490 38491 38492 38493 38494 38495 38496 38497 38498 38499 38500 38501 38502 38503 38504 38505 38506 38507 38508 38509 38510 38511 38512 38513 38514 38515 38516 38517 38518 38519 38520 38521 38522 38523 38524 38525 38526 38527 38528 38529 38530 38531 38532 38533 38534 38535 38536 38537 38538 38539 38540 38541 38542 38543 38544 38545 38546 38547 38548 38549 38550 38551 38552 38553 38554 38555 38556 38557 38558 38559 38560 38561 38562 38563 38564 38565 38566 38567 38568 38569 38570 38571 38572 38573 38574 38575 38576 38577 38578 38579 38580 38581 38582 38583 38584 38585 38586 38587 38588 38589 38590 38591 38592 38593 38594 38595 38596 38597 38598 38599 38600 38601 38602 38603 38604 38605 38606 38607 38608 38609 38610 38611 38612 38613 38614 38615 38616 38617 38618 38619 38620 38621 38622 38623 38624 38625 38626 38627 38628 38629 38630 38631 38632 38633 38634 38635 38636 38637 38638 38639 38640 38641 38642 38643 38644 38645 38646 38647 38648 38649 38650 38651 38652 38653 38654 38655 38656 38657 38658 38659 38660 38661 38662 38663 38664 38665 38666 38667 38668 38669 38670 38671 38672 38673 38674 38675 38676 38677 38678 38679 38680 38681 38682 38683 38684 38685 38686 38687 38688 38689 38690 38691 38692 38693 38694 38695 38696 38697 38698 38699 38700 38701 38702 38703 38704 38705 38706 38707 38708 38709 38710 38711 38712 38713 38714 38715 38716 38717 38718 38719 38720 38721 38722 38723 38724 38725 38726 38727 38728 38729 38730 38731 38732 38733 38734 38735 38736 38737 38738 38739 38740 38741 38742 38743 38744 38745 38746 38747 38748 38749 38750 38751 38752 38753 38754 38755 38756 38757 38758 38759 38760 38761 38762 38763 38764 38765 38766 38767 38768 38769 38770 38771 38772 38773 38774 38775 38776 38777 38778 38779 38780 38781 38782 38783 38784 38785 38786 38787 38788 38789 38790 38791 38792 38793 38794 38795 38796 38797 38798 38799 38800 38801 38802 38803 38804 38805 38806 38807 38808 38809 38810 38811 38812 38813 38814 38815 38816 38817 38818 38819 38820 38821 38822 38823 38824 38825 38826 38827 38828 38829 38830 38831 38832 38833 38834 38835 38836 38837 38838 38839 38840 38841 38842 38843 38844 38845 38846 38847 38848 38849 38850 38851 38852 38853 38854 38855 38856 38857 38858 38859 38860 38861 38862 38863 38864 38865 38866 38867 38868 38869 38870 38871 38872 38873 38874 38875 38876 38877 38878 38879 38880 38881 38882 38883 38884 38885 38886 38887 38888 38889 38890 38891 38892 38893 38894 38895 38896 38897 38898 38899 38900 38901 38902 38903 38904 38905 38906 38907 38908 38909 38910 38911 38912 38913 38914 38915 38916 38917 38918 38919 38920 38921 38922 38923 38924 38925 38926 38927 38928 38929 38930 38931 38932 38933 38934 38935 38936 38937 38938 38939 38940 38941 38942 38943 38944 38945 38946 38947 38948 38949 38950 38951 38952 38953 38954 38955 38956 38957 38958 38959 38960 38961 38962 38963 38964 38965 38966 38967 38968 38969 38970 38971 38972 38973 38974 38975 38976 38977 38978 38979 38980 38981 38982 38983 38984 38985 38986 38987 38988 38989 38990 38991 38992 38993 38994 38995 38996 38997 38998 38999 39000 39001 39002 39003 39004 39005 39006 39007 39008 39009 39010 39011 39012 39013 39014 39015 39016 39017 39018 39019 39020 39021 39022 39023 39024 39025 39026 39027 39028 39029 39030 39031 39032 39033 39034 39035 39036 39037 39038 39039 39040 39041 39042 39043 39044 39045 39046 39047 39048 39049 39050 39051 39052 39053 39054 39055 39056 39057 39058 39059 39060 39061 39062 39063 39064 39065 39066 39067 39068 39069 39070 39071 39072 39073 39074 39075 39076 39077 39078 39079 39080 39081 39082 39083 39084 39085 39086 39087 39088 39089 39090 39091 39092 39093 39094 39095 39096 39097 39098 39099 39100 39101 39102 39103 39104 39105 39106 39107 39108 39109 39110 39111 39112 39113 39114 39115 39116 39117 39118 39119 39120 39121 39122 39123 39124 39125 39126 39127 39128 39129 39130 39131 39132 39133 39134 39135 39136 39137 39138 39139 39140 39141 39142 39143 39144 39145 39146 39147 39148 39149 39150 39151 39152 39153 39154 39155 39156 39157 39158 39159 39160 39161 39162 39163 39164 39165 39166 39167 39168 39169 39170 39171 39172 39173 39174 39175 39176 39177 39178 39179 39180 39181 39182 39183 39184 39185 39186 39187 39188 39189 39190 39191 39192 39193 39194 39195 39196 39197 39198 39199 39200 39201 39202 39203 39204 39205 39206 39207 39208 39209 39210 39211 39212 39213 39214 39215 39216 39217 39218 39219 39220 39221 39222 39223 39224 39225 39226 39227 39228 39229 39230 39231 39232 39233 39234 39235 39236 39237 39238 39239 39240 39241 39242 39243 39244 39245 39246 39247 39248 39249 39250 39251 39252 39253 39254 39255 39256 39257 39258 39259 39260 39261 39262 39263 39264 39265 39266 39267 39268 39269 39270 39271 39272 39273 39274 39275 39276 39277 39278 39279 39280 39281 39282 39283 39284 39285 39286 39287 39288 39289 39290 39291 39292 39293 39294 39295 39296 39297 39298 39299 39300 39301 39302 39303 39304 39305 39306 39307 39308 39309 39310 39311 39312 39313 39314 39315 39316 39317 39318 39319 39320 39321 39322 39323 39324 39325 39326 39327 39328 39329 39330 39331 39332 39333 39334 39335 39336 39337 39338 39339 39340 39341 39342 39343 39344 39345 39346 39347 39348 39349 39350 39351 39352 39353 39354 39355 39356 39357 39358 39359 39360 39361 39362 39363 39364 39365 39366 39367 39368 39369 39370 39371 39372 39373 39374 39375 39376 39377 39378 39379 39380 39381 39382 39383 39384 39385 39386 39387 39388 39389 39390 39391 39392 39393 39394 39395 39396 39397 39398 39399 39400 39401 39402 39403 39404 39405 39406 39407 39408 39409 39410 39411 39412 39413 39414 39415 39416 39417 39418 39419 39420 39421 39422 39423 39424 39425 39426 39427 39428 39429 39430 39431 39432 39433 39434 39435 39436 39437 39438 39439 39440 39441 39442 39443 39444 39445 39446 39447 39448 39449 39450 39451 39452 39453 39454 39455 39456 39457 39458 39459 39460 39461 39462 39463 39464 39465 39466 39467 39468 39469 39470 39471 39472 39473 39474 39475 39476 39477 39478 39479 39480 39481 39482 39483 39484 39485 39486 39487 39488 39489 39490 39491 39492 39493 39494 39495 39496 39497 39498 39499 39500 39501 39502 39503 39504 39505 39506 39507 39508 39509 39510 39511 39512 39513 39514 39515 39516 39517 39518 39519 39520 39521 39522 39523 39524 39525 39526 39527 39528 39529 39530 39531 39532 39533 39534 39535 39536 39537 39538 39539 39540 39541 39542 39543 39544 39545 39546 39547 39548 39549 39550 39551 39552 39553 39554 39555 39556 39557 39558 39559 39560 39561 39562 39563 39564 39565 39566 39567 39568 39569 39570 39571 39572 39573 39574 39575 39576 39577 39578 39579 39580 39581 39582 39583 39584 39585 39586 39587 39588 39589 39590 39591 39592 39593 39594 39595 39596 39597 39598 39599 39600 39601 39602 39603 39604 39605 39606 39607 39608 39609 39610 39611 39612 39613 39614 39615 39616 39617 39618 39619 39620 39621 39622 39623 39624 39625 39626 39627 39628 39629 39630 39631 39632 39633 39634 39635 39636 39637 39638 39639 39640 39641 39642 39643 39644 39645 39646 39647 39648 39649 39650 39651 39652 39653 39654 39655 39656 39657 39658 39659 39660 39661 39662 39663 39664 39665 39666 39667 39668 39669 39670 39671 39672 39673 39674 39675 39676 39677 39678 39679 39680 39681 39682 39683 39684 39685 39686 39687 39688 39689 39690 39691 39692 39693 39694 39695 39696 39697 39698 39699 39700 39701 39702 39703 39704 39705 39706 39707 39708 39709 39710 39711 39712 39713 39714 39715 39716 39717 39718 39719 39720 39721 39722 39723 39724 39725 39726 39727 39728 39729 39730 39731 39732 39733 39734 39735 39736 39737 39738 39739 39740 39741 39742 39743 39744 39745 39746 39747 39748 39749 39750 39751 39752 39753 39754 39755 39756 39757 39758 39759 39760 39761 39762 39763 39764 39765 39766 39767 39768 39769 39770 39771 39772 39773 39774 39775 39776 39777 39778 39779 39780 39781 39782 39783 39784 39785 39786 39787 39788 39789 39790 39791 39792 39793 39794 39795 39796 39797 39798 39799 39800 39801 39802 39803 39804 39805 39806 39807 39808 39809 39810 39811 39812 39813 39814 39815 39816 39817 39818 39819 39820 39821 39822 39823 39824 39825 39826 39827 39828 39829 39830 39831 39832 39833 39834 39835 39836 39837 39838 39839 39840 39841 39842 39843 39844 39845 39846 39847 39848 39849 39850 39851 39852 39853 39854 39855 39856 39857 39858 39859 39860 39861 39862 39863 39864 39865 39866 39867 39868 39869 39870 39871 39872 39873 39874 39875 39876 39877 39878 39879 39880 39881 39882 39883 39884 39885 39886 39887 39888 39889 39890 39891 39892 39893 39894 39895 39896 39897 39898 39899 39900 39901 39902 39903 39904 39905 39906 39907 39908 39909 39910 39911 39912 39913 39914 39915 39916 39917 39918 39919 39920 39921 39922 39923 39924 39925 39926 39927 39928 39929 39930 39931 39932 39933 39934 39935 39936 39937 39938 39939 39940 39941 39942 39943 39944 39945 39946 39947 39948 39949 39950 39951 39952 39953 39954 39955 39956 39957 39958 39959 39960 39961 39962 39963 39964 39965 39966 39967 39968 39969 39970 39971 39972 39973 39974 39975 39976 39977 39978 39979 39980 39981 39982 39983 39984 39985 39986 39987 39988 39989 39990 39991 39992 39993 39994 39995 39996 39997 39998 39999 40000 40001 40002 40003 40004 40005 40006 40007 40008 40009 40010 40011 40012 40013 40014 40015 40016 40017 40018 40019 40020 40021 40022 40023 40024 40025 40026 40027 40028 40029 40030 40031 40032 40033 40034 40035 40036 40037 40038 40039 40040 40041 40042 40043 40044 40045 40046 40047 40048 40049 40050 40051 40052 40053 40054 40055 40056 40057 40058 40059 40060 40061 40062 40063 40064 40065 40066 40067 40068 40069 40070 40071 40072 40073 40074 40075 40076 40077 40078 40079 40080 40081 40082 40083 40084 40085 40086 40087 40088 40089 40090 40091 40092 40093 40094 40095 40096 40097 40098 40099 40100 40101 40102 40103 40104 40105 40106 40107 40108 40109 40110 40111 40112 40113 40114 40115 40116 40117 40118 40119 40120 40121 40122 40123 40124 40125 40126 40127 40128 40129 40130 40131 40132 40133 40134 40135 40136 40137 40138 40139 40140 40141 40142 40143 40144 40145 40146 40147 40148 40149 40150 40151 40152 40153 40154 40155 40156 40157 40158 40159 40160 40161 40162 40163 40164 40165 40166 40167 40168 40169 40170 40171 40172 40173 40174 40175 40176 40177 40178 40179 40180 40181 40182 40183 40184 40185 40186 40187 40188 40189 40190 40191 40192 40193 40194 40195 40196 40197 40198 40199 40200 40201 40202 40203 40204 40205 40206 40207 40208 40209 40210 40211 40212 40213 40214 40215 40216 40217 40218 40219 40220 40221 40222 40223 40224 40225 40226 40227 40228 40229 40230 40231 40232 40233 40234 40235 40236 40237 40238 40239 40240 40241 40242 40243 40244 40245 40246 40247 40248 40249 40250 40251 40252 40253 40254 40255 40256 40257 40258 40259 40260 40261 40262 40263 40264 40265 40266 40267 40268 40269 40270 40271 40272 40273 40274 40275 40276 40277 40278 40279 40280 40281 40282 40283 40284 40285 40286 40287 40288 40289 40290 40291 40292 40293 40294 40295 40296 40297 40298 40299 40300 40301 40302 40303 40304 40305 40306 40307 40308 40309 40310 40311 40312 40313 40314 40315 40316 40317 40318 40319 40320 40321 40322 40323 40324 40325 40326 40327 40328 40329 40330 40331 40332 40333 40334 40335 40336 40337 40338 40339 40340 40341 40342 40343 40344 40345 40346 40347 40348 40349 40350 40351 40352 40353 40354 40355 40356 40357 40358 40359 40360 40361 40362 40363 40364 40365 40366 40367 40368 40369 40370 40371 40372 40373 40374 40375 40376 40377 40378 40379 40380 40381 40382 40383 40384 40385 40386 40387 40388 40389 40390 40391 40392 40393 40394 40395 40396 40397 40398 40399 40400 40401 40402 40403 40404 40405 40406 40407 40408 40409 40410 40411 40412 40413 40414 40415 40416 40417 40418 40419 40420 40421 40422 40423 40424 40425 40426 40427 40428 40429 40430 40431 40432 40433 40434 40435 40436 40437 40438 40439 40440 40441 40442 40443 40444 40445 40446 40447 40448 40449 40450 40451 40452 40453 40454 40455 40456 40457 40458 40459 40460 40461 40462 40463 40464 40465 40466 40467 40468 40469 40470 40471 40472 40473 40474 40475 40476 40477 40478 40479 40480 40481 40482 40483 40484 40485 40486 40487 40488 40489 40490 40491 40492 40493 40494 40495 40496 40497 40498 40499 40500 40501 40502 40503 40504 40505 40506 40507 40508 40509 40510 40511 40512 40513 40514 40515 40516 40517 40518 40519 40520 40521 40522 40523 40524 40525 40526 40527 40528 40529 40530 40531 40532 40533 40534 40535 40536 40537 40538 40539 40540 40541 40542 40543 40544 40545 40546 40547 40548 40549 40550 40551 40552 40553 40554 40555 40556 40557 40558 40559 40560 40561 40562 40563 40564 40565 40566 40567 40568 40569 40570 40571 40572 40573 40574 40575 40576 40577 40578 40579 40580 40581 40582 40583 40584 40585 40586 40587 40588 40589 40590 40591 40592 40593 40594 40595 40596 40597 40598 40599 40600 40601 40602 40603 40604 40605 40606 40607 40608 40609 40610 40611 40612 40613 40614 40615 40616 40617 40618 40619 40620 40621 40622 40623 40624 40625 40626 40627 40628 40629 40630 40631 40632 40633 40634 40635 40636 40637 40638 40639 40640 40641 40642 40643 40644 40645 40646 40647 40648 40649 40650 40651 40652 40653 40654 40655 40656 40657 40658 40659 40660 40661 40662 40663 40664 40665 40666 40667 40668 40669 40670 40671 40672 40673 40674 40675 40676 40677 40678 40679 40680 40681 40682 40683 40684 40685 40686 40687 40688 40689 40690 40691 40692 40693 40694 40695 40696 40697 40698 40699 40700 40701 40702 40703 40704 40705 40706 40707 40708 40709 40710 40711 40712 40713 40714 40715 40716 40717 40718 40719 40720 40721 40722 40723 40724 40725 40726 40727 40728 40729 40730 40731 40732 40733 40734 40735 40736 40737 40738 40739 40740 40741 40742 40743 40744 40745 40746 40747 40748 40749 40750 40751 40752 40753 40754 40755 40756 40757 40758 40759 40760 40761 40762 40763 40764 40765 40766 40767 40768 40769 40770 40771 40772 40773 40774 40775 40776 40777 40778 40779 40780 40781 40782 40783 40784 40785 40786 40787 40788 40789 40790 40791 40792 40793 40794 40795 40796 40797 40798 40799 40800 40801 40802 40803 40804 40805 40806 40807 40808 40809 40810 40811 40812 40813 40814 40815 40816 40817 40818 40819 40820 40821 40822 40823 40824 40825 40826 40827 40828 40829 40830 40831 40832 40833 40834 40835 40836 40837 40838 40839 40840 40841 40842 40843 40844 40845 40846 40847 40848 40849 40850 40851 40852 40853 40854 40855 40856 40857 40858 40859 40860 40861 40862 40863 40864 40865 40866 40867 40868 40869 40870 40871 40872 40873 40874 40875 40876 40877 40878 40879 40880 40881 40882 40883 40884 40885 40886 40887 40888 40889 40890 40891 40892 40893 40894 40895 40896 40897 40898 40899 40900 40901 40902 40903 40904 40905 40906 40907 40908 40909 40910 40911 40912 40913 40914 40915 40916 40917 40918 40919 40920 40921 40922 40923 40924 40925 40926 40927 40928 40929 40930 40931 40932 40933 40934 40935 40936 40937 40938 40939 40940 40941 40942 40943 40944 40945 40946 40947 40948 40949 40950 40951 40952 40953 40954 40955 40956 40957 40958 40959 40960 40961 40962 40963 40964 40965 40966 40967 40968 40969 40970 40971 40972 40973 40974 40975 40976 40977 40978 40979 40980 40981 40982 40983 40984 40985 40986 40987 40988 40989 40990 40991 40992 40993 40994 40995 40996 40997 40998 40999 41000 41001 41002 41003 41004 41005 41006 41007 41008 41009 41010 41011 41012 41013 41014 41015 41016 41017 41018 41019 41020 41021 41022 41023 41024 41025 41026 41027 41028 41029 41030 41031 41032 41033 41034 41035 41036 41037 41038 41039 41040 41041 41042 41043 41044 41045 41046 41047 41048 41049 41050 41051 41052 41053 41054 41055 41056 41057 41058 41059 41060 41061 41062 41063 41064 41065 41066 41067 41068 41069 41070 41071 41072 41073 41074 41075 41076 41077 41078 41079 41080 41081 41082 41083 41084 41085 41086 41087 41088 41089 41090 41091 41092 41093 41094 41095 41096 41097 41098 41099 41100 41101 41102 41103 41104 41105 41106 41107 41108 41109 41110 41111 41112 41113 41114 41115 41116 41117 41118 41119 41120 41121 41122 41123 41124 41125 41126 41127 41128 41129 41130 41131 41132 41133 41134 41135 41136 41137 41138 41139 41140 41141 41142 41143 41144 41145 41146 41147 41148 41149 41150 41151 41152 41153 41154 41155 41156 41157 41158 41159 41160 41161 41162 41163 41164 41165 41166 41167 41168 41169 41170 41171 41172 41173 41174 41175 41176 41177 41178 41179 41180 41181 41182 41183 41184 41185 41186 41187 41188 41189 41190 41191 41192 41193 41194 41195 41196 41197 41198 41199 41200 41201 41202 41203 41204 41205 41206 41207 41208 41209 41210 41211 41212 41213 41214 41215 41216 41217 41218 41219 41220 41221 41222 41223 41224 41225 41226 41227 41228 41229 41230 41231 41232 41233 41234 41235 41236 41237 41238 41239 41240 41241 41242 41243 41244 41245 41246 41247 41248 41249 41250 41251 41252 41253 41254 41255 41256 41257 41258 41259 41260 41261 41262 41263 41264 41265 41266 41267 41268 41269 41270 41271 41272 41273 41274 41275 41276 41277 41278 41279 41280 41281 41282 41283 41284 41285 41286 41287 41288 41289 41290 41291 41292 41293 41294 41295 41296 41297 41298 41299 41300 41301 41302 41303 41304 41305 41306 41307 41308 41309 41310 41311 41312 41313 41314 41315 41316 41317 41318 41319 41320 41321 41322 41323 41324 41325 41326 41327 41328 41329 41330 41331 41332 41333 41334 41335 41336 41337 41338 41339 41340 41341 41342 41343 41344 41345 41346 41347 41348 41349 41350 41351 41352 41353 41354 41355 41356 41357 41358 41359 41360 41361 41362 41363 41364 41365 41366 41367 41368 41369 41370 41371 41372 41373 41374 41375 41376 41377 41378 41379 41380 41381 41382 41383 41384 41385 41386 41387 41388 41389 41390 41391 41392 41393 41394 41395 41396 41397 41398 41399 41400 41401 41402 41403 41404 41405 41406 41407 41408 41409 41410 41411 41412 41413 41414 41415 41416 41417 41418 41419 41420 41421 41422 41423 41424 41425 41426 41427 41428 41429 41430 41431 41432 41433 41434 41435 41436 41437 41438 41439 41440 41441 41442 41443 41444 41445 41446 41447 41448 41449 41450 41451 41452 41453 41454 41455 41456 41457 41458 41459 41460 41461 41462 41463 41464 41465 41466 41467 41468 41469 41470 41471 41472 41473 41474 41475 41476 41477 41478 41479 41480 41481 41482 41483 41484 41485 41486 41487 41488 41489 41490 41491 41492 41493 41494 41495 41496 41497 41498 41499 41500 41501 41502 41503 41504 41505 41506 41507 41508 41509 41510 41511 41512 41513 41514 41515 41516 41517 41518 41519 41520 41521 41522 41523 41524 41525 41526 41527 41528 41529 41530 41531 41532 41533 41534 41535 41536 41537 41538 41539 41540 41541 41542 41543 41544 41545 41546 41547 41548 41549 41550 41551 41552 41553 41554 41555 41556 41557 41558 41559 41560 41561 41562 41563 41564 41565 41566 41567 41568 41569 41570 41571 41572 41573 41574 41575 41576 41577 41578 41579 41580 41581 41582 41583 41584 41585 41586 41587 41588 41589 41590 41591 41592 41593 41594 41595 41596 41597 41598 41599 41600 41601 41602 41603 41604 41605 41606 41607 41608 41609 41610 41611 41612 41613 41614 41615 41616 41617 41618 41619 41620 41621 41622 41623 41624 41625 41626 41627 41628 41629 41630 41631 41632 41633 41634 41635 41636 41637 41638 41639 41640 41641 41642 41643 41644 41645 41646 41647 41648 41649 41650 41651 41652 41653 41654 41655 41656 41657 41658 41659 41660 41661 41662 41663 41664 41665 41666 41667 41668 41669 41670 41671 41672 41673 41674 41675 41676 41677 41678 41679 41680 41681 41682 41683 41684 41685 41686 41687 41688 41689 41690 41691 41692 41693 41694 41695 41696 41697 41698 41699 41700 41701 41702 41703 41704 41705 41706 41707 41708 41709 41710 41711 41712 41713 41714 41715 41716 41717 41718 41719 41720 41721 41722 41723 41724 41725 41726 41727 41728 41729 41730 41731 41732 41733 41734 41735 41736 41737 41738 41739 41740 41741 41742 41743 41744 41745 41746 41747 41748 41749 41750 41751 41752 41753 41754 41755 41756 41757 41758 41759 41760 41761 41762 41763 41764 41765 41766 41767 41768 41769 41770 41771 41772 41773 41774 41775 41776 41777 41778 41779 41780 41781 41782 41783 41784 41785 41786 41787 41788 41789 41790 41791 41792 41793 41794 41795 41796 41797 41798 41799 41800 41801 41802 41803 41804 41805 41806 41807 41808 41809 41810 41811 41812 41813 41814 41815 41816 41817 41818 41819 41820 41821 41822 41823 41824 41825 41826 41827 41828 41829 41830 41831 41832 41833 41834 41835 41836 41837 41838 41839 41840 41841 41842 41843 41844 41845 41846 41847 41848 41849 41850 41851 41852 41853 41854 41855 41856 41857 41858 41859 41860 41861 41862 41863 41864 41865 41866 41867 41868 41869 41870 41871 41872 41873 41874 41875 41876 41877 41878 41879 41880 41881 41882 41883 41884 41885 41886 41887 41888 41889 41890 41891 41892 41893 41894 41895 41896 41897 41898 41899 41900 41901 41902 41903 41904 41905 41906 41907 41908 41909 41910 41911 41912 41913 41914 41915 41916 41917 41918 41919 41920 41921 41922 41923 41924 41925 41926 41927 41928 41929 41930 41931 41932 41933 41934 41935 41936 41937 41938 41939 41940 41941 41942 41943 41944 41945 41946 41947 41948 41949 41950 41951 41952 41953 41954 41955 41956 41957 41958 41959 41960 41961 41962 41963 41964 41965 41966 41967 41968 41969 41970 41971 41972 41973 41974 41975 41976 41977 41978 41979 41980 41981 41982 41983 41984 41985 41986 41987 41988 41989 41990 41991 41992 41993 41994 41995 41996 41997 41998 41999 42000 42001 42002 42003 42004 42005 42006 42007 42008 42009 42010 42011 42012 42013 42014 42015 42016 42017 42018 42019 42020 42021 42022 42023 42024 42025 42026 42027 42028 42029 42030 42031 42032 42033 42034 42035 42036 42037 42038 42039 42040 42041 42042 42043 42044 42045 42046 42047 42048 42049 42050 42051 42052 42053 42054 42055 42056 42057 42058 42059 42060 42061 42062 42063 42064 42065 42066 42067 42068 42069 42070 42071 42072 42073 42074 42075 42076 42077 42078 42079 42080 42081 42082 42083 42084 42085 42086 42087 42088 42089 42090 42091 42092 42093 42094 42095 42096 42097 42098 42099 42100 42101 42102 42103 42104 42105 42106 42107 42108 42109 42110 42111 42112 42113 42114 42115 42116 42117 42118 42119 42120 42121 42122 42123 42124 42125 42126 42127 42128 42129 42130 42131 42132 42133 42134 42135 42136 42137 42138 42139 42140 42141 42142 42143 42144 42145 42146 42147 42148 42149 42150 42151 42152 42153 42154 42155 42156 42157 42158 42159 42160 42161 42162 42163 42164 42165 42166 42167 42168 42169 42170 42171 42172 42173 42174 42175 42176 42177 42178 42179 42180 42181 42182 42183 42184 42185 42186 42187 42188 42189 42190 42191 42192 42193 42194 42195 42196 42197 42198 42199 42200 42201 42202 42203 42204 42205 42206 42207 42208 42209 42210 42211 42212 42213 42214 42215 42216 42217 42218 42219 42220 42221 42222 42223 42224 42225 42226 42227 42228 42229 42230 42231 42232 42233 42234 42235 42236 42237 42238 42239 42240 42241 42242 42243 42244 42245 42246 42247 42248 42249 42250 42251 42252 42253 42254 42255 42256 42257 42258 42259 42260 42261 42262 42263 42264 42265 42266 42267 42268 42269 42270 42271 42272 42273 42274 42275 42276 42277 42278 42279 42280 42281 42282 42283 42284 42285 42286 42287 42288 42289 42290 42291 42292 42293 42294 42295 42296 42297 42298 42299 42300 42301 42302 42303 42304 42305 42306 42307 42308 42309 42310 42311 42312 42313 42314 42315 42316 42317 42318 42319 42320 42321 42322 42323 42324 42325 42326 42327 42328 42329 42330 42331 42332 42333 42334 42335 42336 42337 42338 42339 42340 42341 42342 42343 42344 42345 42346 42347 42348 42349 42350 42351 42352 42353 42354 42355 42356 42357 42358 42359 42360 42361 42362 42363 42364 42365 42366 42367 42368 42369 42370 42371 42372 42373 42374 42375 42376 42377 42378 42379 42380 42381 42382 42383 42384 42385 42386 42387 42388 42389 42390 42391 42392 42393 42394 42395 42396 42397 42398 42399 42400 42401 42402 42403 42404 42405 42406 42407 42408 42409 42410 42411 42412 42413 42414 42415 42416 42417 42418 42419 42420 42421 42422 42423 42424 42425 42426 42427 42428 42429 42430 42431 42432 42433 42434 42435 42436 42437 42438 42439 42440 42441 42442 42443 42444 42445 42446 42447 42448 42449 42450 42451 42452 42453 42454 42455 42456 42457 42458 42459 42460 42461 42462 42463 42464 42465 42466 42467 42468 42469 42470 42471 42472 42473 42474 42475 42476 42477 42478 42479 42480 42481 42482 42483 42484 42485 42486 42487 42488 42489 42490 42491 42492 42493 42494 42495 42496 42497 42498 42499 42500 42501 42502 42503 42504 42505 42506 42507 42508 42509 42510 42511 42512 42513 42514 42515 42516 42517 42518 42519 42520 42521 42522 42523 42524 42525 42526 42527 42528 42529 42530 42531 42532 42533 42534 42535 42536 42537 42538 42539 42540 42541 42542 42543 42544 42545 42546 42547 42548 42549 42550 42551 42552 42553 42554 42555 42556 42557 42558 42559 42560 42561 42562 42563 42564 42565 42566 42567 42568 42569 42570 42571 42572 42573 42574 42575 42576 42577 42578 42579 42580 42581 42582 42583 42584 42585 42586 42587 42588 42589 42590 42591 42592 42593 42594 42595 42596 42597 42598 42599 42600 42601 42602 42603 42604 42605 42606 42607 42608 42609 42610 42611 42612 42613 42614 42615 42616 42617 42618 42619 42620 42621 42622 42623 42624 42625 42626 42627 42628 42629 42630 42631 42632 42633 42634 42635 42636 42637 42638 42639 42640 42641 42642 42643 42644 42645 42646 42647 42648 42649 42650 42651 42652 42653 42654 42655 42656 42657 42658 42659 42660 42661 42662 42663 42664 42665 42666 42667 42668 42669 42670 42671 42672 42673 42674 42675 42676 42677 42678 42679 42680 42681 42682 42683 42684 42685 42686 42687 42688 42689 42690 42691 42692 42693 42694 42695 42696 42697 42698 42699 42700 42701 42702 42703 42704 42705 42706 42707 42708 42709 42710 42711 42712 42713 42714 42715 42716 42717 42718 42719 42720 42721 42722 42723 42724 42725 42726 42727 42728 42729 42730 42731 42732 42733 42734 42735 42736 42737 42738 42739 42740 42741 42742 42743 42744 42745 42746 42747 42748 42749 42750 42751 42752 42753 42754 42755 42756 42757 42758 42759 42760 42761 42762 42763 42764 42765 42766 42767 42768 42769 42770 42771 42772 42773 42774 42775 42776 42777 42778 42779 42780 42781 42782 42783 42784 42785 42786 42787 42788 42789 42790 42791 42792 42793 42794 42795 42796 42797 42798 42799 42800 42801 42802 42803 42804 42805 42806 42807 42808 42809 42810 42811 42812 42813 42814 42815 42816 42817 42818 42819 42820 42821 42822 42823 42824 42825 42826 42827 42828 42829 42830 42831 42832 42833 42834 42835 42836 42837 42838 42839 42840 42841 42842 42843 42844 42845 42846 42847 42848 42849 42850 42851 42852 42853 42854 42855 42856 42857 42858 42859 42860 42861 42862 42863 42864 42865 42866 42867 42868 42869 42870 42871 42872 42873 42874 42875 42876 42877 42878 42879 42880 42881 42882 42883 42884 42885 42886 42887 42888 42889 42890 42891 42892 42893 42894 42895 42896 42897 42898 42899 42900 42901 42902 42903 42904 42905 42906 42907 42908 42909 42910 42911 42912 42913 42914 42915 42916 42917 42918 42919 42920 42921 42922 42923 42924 42925 42926 42927 42928 42929 42930 42931 42932 42933 42934 42935 42936 42937 42938 42939 42940 42941 42942 42943 42944 42945 42946 42947 42948 42949 42950 42951 42952 42953 42954 42955 42956 42957 42958 42959 42960 42961 42962 42963 42964 42965 42966 42967 42968 42969 42970 42971 42972 42973 42974 42975 42976 42977 42978 42979 42980 42981 42982 42983 42984 42985 42986 42987 42988 42989 42990 42991 42992 42993 42994 42995 42996 42997 42998 42999 43000 43001 43002 43003 43004 43005 43006 43007 43008 43009 43010 43011 43012 43013 43014 43015 43016 43017 43018 43019 43020 43021 43022 43023 43024 43025 43026 43027 43028 43029 43030 43031 43032 43033 43034 43035 43036 43037 43038 43039 43040 43041 43042 43043 43044 43045 43046 43047 43048 43049 43050 43051 43052 43053 43054 43055 43056 43057 43058 43059 43060 43061 43062 43063 43064 43065 43066 43067 43068 43069 43070 43071 43072 43073 43074 43075 43076 43077 43078 43079 43080 43081 43082 43083 43084 43085 43086 43087 43088 43089 43090 43091 43092 43093 43094 43095 43096 43097 43098 43099 43100 43101 43102 43103 43104 43105 43106 43107 43108 43109 43110 43111 43112 43113 43114 43115 43116 43117 43118 43119 43120 43121 43122 43123 43124 43125 43126 43127 43128 43129 43130 43131 43132 43133 43134 43135 43136 43137 43138 43139 43140 43141 43142 43143 43144 43145 43146 43147 43148 43149 43150 43151 43152 43153 43154 43155 43156 43157 43158 43159 43160 43161 43162 43163 43164 43165 43166 43167 43168 43169 43170 43171 43172 43173 43174 43175 43176 43177 43178 43179 43180 43181 43182 43183 43184 43185 43186 43187 43188 43189 43190 43191 43192 43193 43194 43195 43196 43197 43198 43199 43200 43201 43202 43203 43204 43205 43206 43207 43208 43209 43210 43211 43212 43213 43214 43215 43216 43217 43218 43219 43220 43221 43222 43223 43224 43225 43226 43227 43228 43229 43230 43231 43232 43233 43234 43235 43236 43237 43238 43239 43240 43241 43242 43243 43244 43245 43246 43247 43248 43249 43250 43251 43252 43253 43254 43255 43256 43257 43258 43259 43260 43261 43262 43263 43264 43265 43266 43267 43268 43269 43270 43271 43272 43273 43274 43275 43276 43277 43278 43279 43280 43281 43282 43283 43284 43285 43286 43287 43288 43289 43290 43291 43292 43293 43294 43295 43296 43297 43298 43299 43300 43301 43302 43303 43304 43305 43306 43307 43308 43309 43310 43311 43312 43313 43314 43315 43316 43317 43318 43319 43320 43321 43322 43323 43324 43325 43326 43327 43328 43329 43330 43331 43332 43333 43334 43335 43336 43337 43338 43339 43340 43341 43342 43343 43344 43345 43346 43347 43348 43349 43350 43351 43352 43353 43354 43355 43356 43357 43358 43359 43360 43361 43362 43363 43364 43365 43366 43367 43368 43369 43370 43371 43372 43373 43374 43375 43376 43377 43378 43379 43380 43381 43382 43383 43384 43385 43386 43387 43388 43389 43390 43391 43392 43393 43394 43395 43396 43397 43398 43399 43400 43401 43402 43403 43404 43405 43406 43407 43408 43409 43410 43411 43412 43413 43414 43415 43416 43417 43418 43419 43420 43421 43422 43423 43424 43425 43426 43427 43428 43429 43430 43431 43432 43433 43434 43435 43436 43437 43438 43439 43440 43441 43442 43443 43444 43445 43446 43447 43448 43449 43450 43451 43452 43453 43454 43455 43456 43457 43458 43459 43460 43461 43462 43463 43464 43465 43466 43467 43468 43469 43470 43471 43472 43473 43474 43475 43476 43477 43478 43479 43480 43481 43482 43483 43484 43485 43486 43487 43488 43489 43490 43491 43492 43493 43494 43495 43496 43497 43498 43499 43500 43501 43502 43503 43504 43505 43506 43507 43508 43509 43510 43511 43512 43513 43514 43515 43516 43517 43518 43519 43520 43521 43522 43523 43524 43525 43526 43527 43528 43529 43530 43531 43532 43533 43534 43535 43536 43537 43538 43539 43540 43541 43542 43543 43544 43545 43546 43547 43548 43549 43550 43551 43552 43553 43554 43555 43556 43557 43558 43559 43560 43561 43562 43563 43564 43565 43566 43567 43568 43569 43570 43571 43572 43573 43574 43575 43576 43577 43578 43579 43580 43581 43582 43583 43584 43585 43586 43587 43588 43589 43590 43591 43592 43593 43594 43595 43596 43597 43598 43599 43600 43601 43602 43603 43604 43605 43606 43607 43608 43609 43610 43611 43612 43613 43614 43615 43616 43617 43618 43619 43620 43621 43622 43623 43624 43625 43626 43627 43628 43629 43630 43631 43632 43633 43634 43635 43636 43637 43638 43639 43640 43641 43642 43643 43644 43645 43646 43647 43648 43649 43650 43651 43652 43653 43654 43655 43656 43657 43658 43659 43660 43661 43662 43663 43664 43665 43666 43667 43668 43669 43670 43671 43672 43673 43674 43675 43676 43677 43678 43679 43680 43681 43682 43683 43684 43685 43686 43687 43688 43689 43690 43691 43692 43693 43694 43695 43696 43697 43698 43699 43700 43701 43702 43703 43704 43705 43706 43707 43708 43709 43710 43711 43712 43713 43714 43715 43716 43717 43718 43719 43720 43721 43722 43723 43724 43725 43726 43727 43728 43729 43730 43731 43732 43733 43734 43735 43736 43737 43738 43739 43740 43741 43742 43743 43744 43745 43746 43747 43748 43749 43750 43751 43752 43753 43754 43755 43756 43757 43758 43759 43760 43761 43762 43763 43764 43765 43766 43767 43768 43769 43770 43771 43772 43773 43774 43775 43776 43777 43778 43779 43780 43781 43782 43783 43784 43785 43786 43787 43788 43789 43790 43791 43792 43793 43794 43795 43796 43797 43798 43799 43800 43801 43802 43803 43804 43805 43806 43807 43808 43809 43810 43811 43812 43813 43814 43815 43816 43817 43818 43819 43820 43821 43822 43823 43824 43825 43826 43827 43828 43829 43830 43831 43832 43833 43834 43835 43836 43837 43838 43839 43840 43841 43842 43843 43844 43845 43846 43847 43848 43849 43850 43851 43852 43853 43854 43855 43856 43857 43858 43859 43860 43861 43862 43863 43864 43865 43866 43867 43868 43869 43870 43871 43872 43873 43874 43875 43876 43877 43878 43879 43880 43881 43882 43883 43884 43885 43886 43887 43888 43889 43890 43891 43892 43893 43894 43895 43896 43897 43898 43899 43900 43901 43902 43903 43904 43905 43906 43907 43908 43909 43910 43911 43912 43913 43914 43915 43916 43917 43918 43919 43920 43921 43922 43923 43924 43925 43926 43927 43928 43929 43930 43931 43932 43933 43934 43935 43936 43937 43938 43939 43940 43941 43942 43943 43944 43945 43946 43947 43948 43949 43950 43951 43952 43953 43954 43955 43956 43957 43958 43959 43960 43961 43962 43963 43964 43965 43966 43967 43968 43969 43970 43971 43972 43973 43974 43975 43976 43977 43978 43979 43980 43981 43982 43983 43984 43985 43986 43987 43988 43989 43990 43991 43992 43993 43994 43995 43996 43997 43998 43999 44000 44001 44002 44003 44004 44005 44006 44007 44008 44009 44010 44011 44012 44013 44014 44015 44016 44017 44018 44019 44020 44021 44022 44023 44024 44025 44026 44027 44028 44029 44030 44031 44032 44033 44034 44035 44036 44037 44038 44039 44040 44041 44042 44043 44044 44045 44046 44047 44048 44049 44050 44051 44052 44053 44054 44055 44056 44057 44058 44059 44060 44061 44062 44063 44064 44065 44066 44067 44068 44069 44070 44071 44072 44073 44074 44075 44076 44077 44078 44079 44080 44081 44082 44083 44084 44085 44086 44087 44088 44089 44090 44091 44092 44093 44094 44095 44096 44097 44098 44099 44100 44101 44102 44103 44104 44105 44106 44107 44108 44109 44110 44111 44112 44113 44114 44115 44116 44117 44118 44119 44120 44121 44122 44123 44124 44125 44126 44127 44128 44129 44130 44131 44132 44133 44134 44135 44136 44137 44138 44139 44140 44141 44142 44143 44144 44145 44146 44147 44148 44149 44150 44151 44152 44153 44154 44155 44156 44157 44158 44159 44160 44161 44162 44163 44164 44165 44166 44167 44168 44169 44170 44171 44172 44173 44174 44175 44176 44177 44178 44179 44180 44181 44182 44183 44184 44185 44186 44187 44188 44189 44190 44191 44192 44193 44194 44195 44196 44197 44198 44199 44200 44201 44202 44203 44204 44205 44206 44207 44208 44209 44210 44211 44212 44213 44214 44215 44216 44217 44218 44219 44220 44221 44222 44223 44224 44225 44226 44227 44228 44229 44230 44231 44232 44233 44234 44235 44236 44237 44238 44239 44240 44241 44242 44243 44244 44245 44246 44247 44248 44249 44250 44251 44252 44253 44254 44255 44256 44257 44258 44259 44260 44261 44262 44263 44264 44265 44266 44267 44268 44269 44270 44271 44272 44273 44274 44275 44276 44277 44278 44279 44280 44281 44282 44283 44284 44285 44286 44287 44288 44289 44290 44291 44292 44293 44294 44295 44296 44297 44298 44299 44300 44301 44302 44303 44304 44305 44306 44307 44308 44309 44310 44311 44312 44313 44314 44315 44316 44317 44318 44319 44320 44321 44322 44323 44324 44325 44326 44327 44328 44329 44330 44331 44332 44333 44334 44335 44336 44337 44338 44339 44340 44341 44342 44343 44344 44345 44346 44347 44348 44349 44350 44351 44352 44353 44354 44355 44356 44357 44358 44359 44360 44361 44362 44363 44364 44365 44366 44367 44368 44369 44370 44371 44372 44373 44374 44375 44376 44377 44378 44379 44380 44381 44382 44383 44384 44385 44386 44387 44388 44389 44390 44391 44392 44393 44394 44395 44396 44397 44398 44399 44400 44401 44402 44403 44404 44405 44406 44407 44408 44409 44410 44411 44412 44413 44414 44415 44416 44417 44418 44419 44420 44421 44422 44423 44424 44425 44426 44427 44428 44429 44430 44431 44432 44433 44434 44435 44436 44437 44438 44439 44440 44441 44442 44443 44444 44445 44446 44447 44448 44449 44450 44451 44452 44453 44454 44455 44456 44457 44458 44459 44460 44461 44462 44463 44464 44465 44466 44467 44468 44469 44470 44471 44472 44473 44474 44475 44476 44477 44478 44479 44480 44481 44482 44483 44484 44485 44486 44487 44488 44489 44490 44491 44492 44493 44494 44495 44496 44497 44498 44499 44500 44501 44502 44503 44504 44505 44506 44507 44508 44509 44510 44511 44512 44513 44514 44515 44516 44517 44518 44519 44520 44521 44522 44523 44524 44525 44526 44527 44528 44529 44530 44531 44532 44533 44534 44535 44536 44537 44538 44539 44540 44541 44542 44543 44544 44545 44546 44547 44548 44549 44550 44551 44552 44553 44554 44555 44556 44557 44558 44559 44560 44561 44562 44563 44564 44565 44566 44567 44568 44569 44570 44571 44572 44573 44574 44575 44576 44577 44578 44579 44580 44581 44582 44583 44584 44585 44586 44587 44588 44589 44590 44591 44592 44593 44594 44595 44596 44597 44598 44599 44600 44601 44602 44603 44604 44605 44606 44607 44608 44609 44610 44611 44612 44613 44614 44615 44616 44617 44618 44619 44620 44621 44622 44623 44624 44625 44626 44627 44628 44629 44630 44631 44632 44633 44634 44635 44636 44637 44638 44639 44640 44641 44642 44643 44644 44645 44646 44647 44648 44649 44650 44651 44652 44653 44654 44655 44656 44657 44658 44659 44660 44661 44662 44663 44664 44665 44666 44667 44668 44669 44670 44671 44672 44673 44674 44675 44676 44677 44678 44679 44680 44681 44682 44683 44684 44685 44686 44687 44688 44689 44690 44691 44692 44693 44694 44695 44696 44697 44698 44699 44700 44701 44702 44703 44704 44705 44706 44707 44708 44709 44710 44711 44712 44713 44714 44715 44716 44717 44718 44719 44720 44721 44722 44723 44724 44725 44726 44727 44728 44729 44730 44731 44732 44733 44734 44735 44736 44737 44738 44739 44740 44741 44742 44743 44744 44745 44746 44747 44748 44749 44750 44751 44752 44753 44754 44755 44756 44757 44758 44759 44760 44761 44762 44763 44764 44765 44766 44767 44768 44769 44770 44771 44772 44773 44774 44775 44776 44777 44778 44779 44780 44781 44782 44783 44784 44785 44786 44787 44788 44789 44790 44791 44792 44793 44794 44795 44796 44797 44798 44799 44800 44801 44802 44803 44804 44805 44806 44807 44808 44809 44810 44811 44812 44813 44814 44815 44816 44817 44818 44819 44820 44821 44822 44823 44824 44825 44826 44827 44828 44829 44830 44831 44832 44833 44834 44835 44836 44837 44838 44839 44840 44841 44842 44843 44844 44845 44846 44847 44848 44849 44850 44851 44852 44853 44854 44855 44856 44857 44858 44859 44860 44861 44862 44863 44864 44865 44866 44867 44868 44869 44870 44871 44872 44873 44874 44875 44876 44877 44878 44879 44880 44881 44882 44883 44884 44885 44886 44887 44888 44889 44890 44891 44892 44893 44894 44895 44896 44897 44898 44899 44900 44901 44902 44903 44904 44905 44906 44907 44908 44909 44910 44911 44912 44913 44914 44915 44916 44917 44918 44919 44920 44921 44922 44923 44924 44925 44926 44927 44928 44929 44930 44931 44932 44933 44934 44935 44936 44937 44938 44939 44940 44941 44942 44943 44944 44945 44946 44947 44948 44949 44950 44951 44952 44953 44954 44955 44956 44957 44958 44959 44960 44961 44962 44963 44964 44965 44966 44967 44968 44969 44970 44971 44972 44973 44974 44975 44976 44977 44978 44979 44980 44981 44982 44983 44984 44985 44986 44987 44988 44989 44990 44991 44992 44993 44994 44995 44996 44997 44998 44999 45000 45001 45002 45003 45004 45005 45006 45007 45008 45009 45010 45011 45012 45013 45014 45015 45016 45017 45018 45019 45020 45021 45022 45023 45024 45025 45026 45027 45028 45029 45030 45031 45032 45033 45034 45035 45036 45037 45038 45039 45040 45041 45042 45043 45044 45045 45046 45047 45048 45049 45050 45051 45052 45053 45054 45055 45056 45057 45058 45059 45060 45061 45062 45063 45064 45065 45066 45067 45068 45069 45070 45071 45072 45073 45074 45075 45076 45077 45078 45079 45080 45081 45082 45083 45084 45085 45086 45087 45088 45089 45090 45091 45092 45093 45094 45095 45096 45097 45098 45099 45100 45101 45102 45103 45104 45105 45106 45107 45108 45109 45110 45111 45112 45113 45114 45115 45116 45117 45118 45119 45120 45121 45122 45123 45124 45125 45126 45127 45128 45129 45130 45131 45132 45133 45134 45135 45136 45137 45138 45139 45140 45141 45142 45143 45144 45145 45146 45147 45148 45149 45150 45151 45152 45153 45154 45155 45156 45157 45158 45159 45160 45161 45162 45163 45164 45165 45166 45167 45168 45169 45170 45171 45172 45173 45174 45175 45176 45177 45178 45179 45180 45181 45182 45183 45184 45185 45186 45187 45188 45189 45190 45191 45192 45193 45194 45195 45196 45197 45198 45199 45200 45201 45202 45203 45204 45205 45206 45207 45208 45209 45210 45211 45212 45213 45214 45215 45216 45217 45218 45219 45220 45221 45222 45223 45224 45225 45226 45227 45228 45229 45230 45231 45232 45233 45234 45235 45236 45237 45238 45239 45240 45241 45242 45243 45244 45245 45246 45247 45248 45249 45250 45251 45252 45253 45254 45255 45256 45257 45258 45259 45260 45261 45262 45263 45264 45265 45266 45267 45268 45269 45270 45271 45272 45273 45274 45275 45276 45277 45278 45279 45280 45281 45282 45283 45284 45285 45286 45287 45288 45289 45290 45291 45292 45293 45294 45295 45296 45297 45298 45299 45300 45301 45302 45303 45304 45305 45306 45307 45308 45309 45310 45311 45312 45313 45314 45315 45316 45317 45318 45319 45320 45321 45322 45323 45324 45325 45326 45327 45328 45329 45330 45331 45332 45333 45334 45335 45336 45337 45338 45339 45340 45341 45342 45343 45344 45345 45346 45347 45348 45349 45350 45351 45352 45353 45354 45355 45356 45357 45358 45359 45360 45361 45362 45363 45364 45365 45366 45367 45368 45369 45370 45371 45372 45373 45374 45375 45376 45377 45378 45379 45380 45381 45382 45383 45384 45385 45386 45387 45388 45389 45390 45391 45392 45393 45394 45395 45396 45397 45398 45399 45400 45401 45402 45403 45404 45405 45406 45407 45408 45409 45410 45411 45412 45413 45414 45415 45416 45417 45418 45419 45420 45421 45422 45423 45424 45425 45426 45427 45428 45429 45430 45431 45432 45433 45434 45435 45436 45437 45438 45439 45440 45441 45442 45443 45444 45445 45446 45447 45448 45449 45450 45451 45452 45453 45454 45455 45456 45457 45458 45459 45460 45461 45462 45463 45464 45465 45466 45467 45468 45469 45470 45471 45472 45473 45474 45475 45476 45477 45478 45479 45480 45481 45482 45483 45484 45485 45486 45487 45488 45489 45490 45491 45492 45493 45494 45495 45496 45497 45498 45499 45500 45501 45502 45503 45504 45505 45506 45507 45508 45509 45510 45511 45512 45513 45514 45515 45516 45517 45518 45519 45520 45521 45522 45523 45524 45525 45526 45527 45528 45529 45530 45531 45532 45533 45534 45535 45536 45537 45538 45539 45540 45541 45542 45543 45544 45545 45546 45547 45548 45549 45550 45551 45552 45553 45554 45555 45556 45557 45558 45559 45560 45561 45562 45563 45564 45565 45566 45567 45568 45569 45570 45571 45572 45573 45574 45575 45576 45577 45578 45579 45580 45581 45582 45583 45584 45585 45586 45587 45588 45589 45590 45591 45592 45593 45594 45595 45596 45597 45598 45599 45600 45601 45602 45603 45604 45605 45606 45607 45608 45609 45610 45611 45612 45613 45614 45615 45616 45617 45618 45619 45620 45621 45622 45623 45624 45625 45626 45627 45628 45629 45630 45631 45632 45633 45634 45635 45636 45637 45638 45639 45640 45641 45642 45643 45644 45645 45646 45647 45648 45649 45650 45651 45652 45653 45654 45655 45656 45657 45658 45659 45660 45661 45662 45663 45664 45665 45666 45667 45668 45669 45670 45671 45672 45673 45674 45675 45676 45677 45678 45679 45680 45681 45682 45683 45684 45685 45686 45687 45688 45689 45690 45691 45692 45693 45694 45695 45696 45697 45698 45699 45700 45701 45702 45703 45704 45705 45706
|
% ****************************************************
% * DO NOT MODIFY THIS FILE!!!! *
% * It was generated from gawktexi.in by sidebar.awk *
% * Edit gawktexi.in instead. *
% ****************************************************
\input texinfo @c -*-texinfo-*-
@c vim: filetype=texinfo
@c %**start of header (This is for running Texinfo on a region.)
@setfilename gawk.info
@settitle The GNU Awk User's Guide
@c %**end of header (This is for running Texinfo on a region.)
@dircategory Text creation and manipulation
@direntry
* Gawk: (gawk). A text scanning and processing language.
@end direntry
@dircategory Individual utilities
@direntry
* awk: (gawk)Invoking Gawk. Text scanning and processing.
@end direntry
@ifset FOR_PRINT
@tex
\gdef\xrefprintnodename#1{``#1''}
@end tex
@end ifset
@ifclear FOR_PRINT
@c With early 2014 texinfo.tex, restore PDF links and colors
@tex
\gdef\linkcolor{0.5 0.09 0.12} % Dark Red
\gdef\urlcolor{0.5 0.09 0.12} % Also
\global\urefurlonlylinktrue
@end tex
@end ifclear
@ifnotdocbook
@set BULLET @bullet{}
@set MINUS @minus{}
@end ifnotdocbook
@ifdocbook
@set BULLET
@set MINUS
@end ifdocbook
@iftex
@set TIMES @times
@end iftex
@ifnottex
@set TIMES *
@end ifnottex
@c Let texinfo.tex give us full section titles
@xrefautomaticsectiontitle on
@c The following information should be updated here only!
@c This sets the edition of the document, the version of gawk it
@c applies to and all the info about who's publishing this edition
@c These apply across the board.
@set UPDATE-MONTH March, 2020
@set VERSION 5.1
@set PATCHLEVEL 0
@set GAWKINETTITLE TCP/IP Internetworking with @command{gawk}
@ifset FOR_PRINT
@set TITLE Effective awk Programming
@end ifset
@ifclear FOR_PRINT
@set TITLE GAWK: Effective AWK Programming
@end ifclear
@set SUBTITLE A User's Guide for GNU Awk
@set EDITION 5.1
@iftex
@set DOCUMENT book
@set CHAPTER chapter
@set APPENDIX appendix
@set SECTION section
@set SUBSECTION subsection
@set DARKCORNER @inmargin{@image{lflashlight,1cm}, @image{rflashlight,1cm}}
@set COMMONEXT (c.e.)
@set PAGE page
@end iftex
@ifinfo
@set DOCUMENT Info file
@set CHAPTER major node
@set APPENDIX major node
@set SECTION minor node
@set SUBSECTION node
@set DARKCORNER (d.c.)
@set COMMONEXT (c.e.)
@set PAGE screen
@end ifinfo
@ifhtml
@set DOCUMENT Web page
@set CHAPTER chapter
@set APPENDIX appendix
@set SECTION section
@set SUBSECTION subsection
@set DARKCORNER (d.c.)
@set COMMONEXT (c.e.)
@set PAGE screen
@end ifhtml
@ifdocbook
@set DOCUMENT book
@set CHAPTER chapter
@set APPENDIX appendix
@set SECTION section
@set SUBSECTION subsection
@set DARKCORNER (d.c.)
@set COMMONEXT (c.e.)
@set PAGE page
@end ifdocbook
@ifxml
@set DOCUMENT book
@set CHAPTER chapter
@set APPENDIX appendix
@set SECTION section
@set SUBSECTION subsection
@set DARKCORNER (d.c.)
@set COMMONEXT (c.e.)
@set PAGE page
@end ifxml
@ifplaintext
@set DOCUMENT book
@set CHAPTER chapter
@set APPENDIX appendix
@set SECTION section
@set SUBSECTION subsection
@set DARKCORNER (d.c.)
@set COMMONEXT (c.e.)
@set PAGE page
@end ifplaintext
@ifdocbook
@c empty on purpose
@set PART1
@set PART2
@set PART3
@set PART4
@end ifdocbook
@ifnotdocbook
@set PART1 Part I:@*
@set PART2 Part II:@*
@set PART3 Part III:@*
@set PART4 Part IV:@*
@end ifnotdocbook
@c some special symbols
@iftex
@set LEQ @math{@leq}
@set PI @math{@pi}
@end iftex
@ifdocbook
@set LEQ @inlineraw{docbook, ≤}
@set PI @inlineraw{docbook, &pgr;}
@end ifdocbook
@ifnottex
@ifnotdocbook
@set LEQ <=
@set PI @i{pi}
@end ifnotdocbook
@end ifnottex
@ifnottex
@ifnotdocbook
@macro ii{text}
@i{\text\}
@end macro
@end ifnotdocbook
@end ifnottex
@ifdocbook
@macro ii{text}
@inlineraw{docbook,<lineannotation>\text\</lineannotation>}
@end macro
@end ifdocbook
@ifclear FOR_PRINT
@set FN file name
@set FFN File name
@set DF data file
@set DDF Data file
@set PVERSION version
@end ifclear
@ifset FOR_PRINT
@set FN filename
@set FFN Filename
@set DF datafile
@set DDF Datafile
@set PVERSION version
@end ifset
@c For HTML, spell out email addresses, to avoid problems with
@c address harvesters for spammers.
@ifhtml
@macro EMAIL{real,spelled}
``\spelled\''
@end macro
@end ifhtml
@ifnothtml
@macro EMAIL{real,spelled}
@email{\real\}
@end macro
@end ifnothtml
@c Indexing macros
@ifinfo
@macro cindexawkfunc{name}
@cindex @code{\name\}
@end macro
@macro cindexgawkfunc{name}
@cindex @code{\name\}
@end macro
@end ifinfo
@ifnotinfo
@macro cindexawkfunc{name}
@cindex @code{\name\()} function
@end macro
@macro cindexgawkfunc{name}
@cindex @code{\name\()} function (@command{gawk})
@end macro
@end ifnotinfo
@ignore
Some comments on the layout for TeX.
1. Use at least texinfo.tex 2016-02-05.07.
@end ignore
@c merge the function and variable indexes into the concept index
@ifinfo
@synindex fn cp
@synindex vr cp
@end ifinfo
@iftex
@syncodeindex fn cp
@syncodeindex vr cp
@end iftex
@ifxml
@syncodeindex fn cp
@syncodeindex vr cp
@end ifxml
@ifdocbook
@synindex fn cp
@synindex vr cp
@end ifdocbook
@c If "finalout" is commented out, the printed output will show
@c black boxes that mark lines that are too long. Thus, it is
@c unwise to comment it out when running a master in case there are
@c overfulls which are deemed okay.
@iftex
@finalout
@end iftex
@c Enabled '-quotes in PDF files so that cut/paste works in
@c more places.
@codequoteundirected on
@codequotebacktick on
@copying
@docbook
<para>
“To boldly go where no man has gone before” is a
Registered Trademark of Paramount Pictures Corporation.</para>
<para>Published by:</para>
<literallayout class="normal">Free Software Foundation
51 Franklin Street, Fifth Floor
Boston, MA 02110-1301 USA
Phone: +1-617-542-5942
Fax: +1-617-542-2652
Email: <email>gnu@@gnu.org</email>
URL: <ulink url="https://www.gnu.org">https://www.gnu.org/</ulink></literallayout>
<literallayout class="normal">Copyright © 1989, 1991, 1992, 1993, 1996–2005, 2007, 2009–2020
Free Software Foundation, Inc.
All Rights Reserved.</literallayout>
@end docbook
@ifnotdocbook
Copyright @copyright{} 1989, 1991, 1992, 1993, 1996--2005, 2007, 2009--2020 @*
Free Software Foundation, Inc.
@end ifnotdocbook
@sp 2
This is Edition @value{EDITION} of @cite{@value{TITLE}: @value{SUBTITLE}},
for the @value{VERSION}.@value{PATCHLEVEL} (or later) version of the GNU
implementation of AWK.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with the
Invariant Sections being ``GNU General Public License'', with the
Front-Cover Texts being ``A GNU Manual'', and with the Back-Cover Texts
as in (a) below.
@ifclear FOR_PRINT
A copy of the license is included in the section entitled
``GNU Free Documentation License''.
@end ifclear
@ifset FOR_PRINT
A copy of the license
may be found on the Internet at
@uref{https://www.gnu.org/software/gawk/manual/html_node/GNU-Free-Documentation-License.html,
the GNU Project's website}.
@end ifset
@enumerate a
@item
The FSF's Back-Cover Text is: ``You have the freedom to
copy and modify this GNU manual.''
@end enumerate
@end copying
@c Comment out the "smallbook" for technical review. Saves
@c considerable paper. Remember to turn it back on *before*
@c starting the page-breaking work.
@c 4/2002: Karl Berry recommends commenting out this and the
@c `@setchapternewpage odd', and letting users use `texi2dvi -t'
@c if they want to waste paper.
@c @smallbook
@c Uncomment this for the release. Leaving it off saves paper
@c during editing and review.
@setchapternewpage odd
@shorttitlepage GNU Awk
@titlepage
@title @value{TITLE}
@subtitle @value{SUBTITLE}
@subtitle Edition @value{EDITION}
@subtitle @value{UPDATE-MONTH}
@author Arnold D. Robbins
@ifnotdocbook
@c Include the Distribution inside the titlepage environment so
@c that headings are turned off. Headings on and off do not work.
@page
@vskip 0pt plus 1filll
``To boldly go where no man has gone before'' is a
Registered Trademark of Paramount Pictures Corporation. @*
@c sorry, i couldn't resist
@sp 3
Published by:
@sp 1
Free Software Foundation @*
51 Franklin Street, Fifth Floor @*
Boston, MA 02110-1301 USA @*
Phone: +1-617-542-5942 @*
Fax: +1-617-542-2652 @*
Email: @email{gnu@@gnu.org} @*
URL: @uref{https://www.gnu.org/} @*
@c This one is correct for gawk 3.1.0 from the FSF
ISBN 1-882114-28-0 @*
@sp 2
@insertcopying
@end ifnotdocbook
@end titlepage
@c Thanks to Bob Chassell for directions on doing dedications.
@iftex
@headings off
@page
@w{ }
@sp 9
@center @i{To my parents, for their love, and for the wonderful example they set for me.}
@sp 1
@center @i{To my wife, Miriam, for making me complete.
Thank you for building your life together with me.}
@sp 1
@center @i{To our children, Chana, Rivka, Nachum, and Malka, for enrichening our lives in innumerable ways.}
@sp 1
@w{ }
@page
@w{ }
@page
@headings on
@end iftex
@docbook
<dedication>
<para>To my parents, for their love, and for the wonderful
example they set for me.</para>
<para>To my wife Miriam, for making me complete.
Thank you for building your life together with me.</para>
<para>To our children Chana, Rivka, Nachum and Malka,
for enrichening our lives in innumerable ways.</para>
</dedication>
@end docbook
@iftex
@headings off
@evenheading @thispage@ @ @ @strong{@value{TITLE}} @| @|
@oddheading @| @| @strong{@thischapter}@ @ @ @thispage
@end iftex
@ifnottex
@ifnotxml
@ifnotdocbook
@node Top
@top General Introduction
@c Preface node should come right after the Top
@c node, in `unnumbered' sections, then the chapter, `What is gawk'.
@c Licensing nodes are appendices, they're not central to AWK.
This file documents @command{awk}, a program that you can use to select
particular records in a file and perform operations upon them.
@insertcopying
@end ifnotdocbook
@end ifnotxml
@end ifnottex
@menu
* Foreword3:: Some nice words about this
@value{DOCUMENT}.
* Foreword4:: More nice words.
* Preface:: What this @value{DOCUMENT} is about; brief
history and acknowledgments.
* Getting Started:: A basic introduction to using
@command{awk}. How to run an @command{awk}
program. Command-line syntax.
* Invoking Gawk:: How to run @command{gawk}.
* Regexp:: All about matching things using regular
expressions.
* Reading Files:: How to read files and manipulate fields.
* Printing:: How to print using @command{awk}. Describes
the @code{print} and @code{printf}
statements. Also describes redirection of
output.
* Expressions:: Expressions are the basic building blocks
of statements.
* Patterns and Actions:: Overviews of patterns and actions.
* Arrays:: The description and use of arrays. Also
includes array-oriented control statements.
* Functions:: Built-in and user-defined functions.
* Library Functions:: A Library of @command{awk} Functions.
* Sample Programs:: Many @command{awk} programs with complete
explanations.
* Advanced Features:: Stuff for advanced users, specific to
@command{gawk}.
* Internationalization:: Getting @command{gawk} to speak your
language.
* Debugger:: The @command{gawk} debugger.
* Namespaces:: How namespaces work in @command{gawk}.
* Arbitrary Precision Arithmetic:: Arbitrary precision arithmetic with
@command{gawk}.
* Dynamic Extensions:: Adding new built-in functions to
@command{gawk}.
* Language History:: The evolution of the @command{awk}
language.
* Installation:: Installing @command{gawk} under various
operating systems.
* Notes:: Notes about adding things to @command{gawk}
and possible future work.
* Basic Concepts:: A very quick introduction to programming
concepts.
* Glossary:: An explanation of some unfamiliar terms.
* Copying:: Your right to copy and distribute
@command{gawk}.
* GNU Free Documentation License:: The license for this @value{DOCUMENT}.
* Index:: Concept and Variable Index.
@detailmenu
* History:: The history of @command{gawk} and
@command{awk}.
* Names:: What name to use to find
@command{awk}.
* This Manual:: Using this @value{DOCUMENT}. Includes
sample input files that you can use.
* Conventions:: Typographical Conventions.
* Manual History:: Brief history of the GNU project and
this @value{DOCUMENT}.
* How To Contribute:: Helping to save the world.
* Acknowledgments:: Acknowledgments.
* Running gawk:: How to run @command{gawk} programs;
includes command-line syntax.
* One-shot:: Running a short throwaway
@command{awk} program.
* Read Terminal:: Using no input files (input from the
keyboard instead).
* Long:: Putting permanent @command{awk}
programs in files.
* Executable Scripts:: Making self-contained @command{awk}
programs.
* Comments:: Adding documentation to @command{gawk}
programs.
* Quoting:: More discussion of shell quoting
issues.
* DOS Quoting:: Quoting in Windows Batch Files.
* Sample Data Files:: Sample data files for use in the
@command{awk} programs illustrated in
this @value{DOCUMENT}.
* Very Simple:: A very simple example.
* Two Rules:: A less simple one-line example using
two rules.
* More Complex:: A more complex example.
* Statements/Lines:: Subdividing or combining statements
into lines.
* Other Features:: Other Features of @command{awk}.
* When:: When to use @command{gawk} and when to
use other things.
* Intro Summary:: Summary of the introduction.
* Command Line:: How to run @command{awk}.
* Options:: Command-line options and their
meanings.
* Other Arguments:: Input file names and variable
assignments.
* Naming Standard Input:: How to specify standard input with
other files.
* Environment Variables:: The environment variables
@command{gawk} uses.
* AWKPATH Variable:: Searching directories for
@command{awk} programs.
* AWKLIBPATH Variable:: Searching directories for
@command{awk} shared libraries.
* Other Environment Variables:: The environment variables.
* Exit Status:: @command{gawk}'s exit status.
* Include Files:: Including other files into your
program.
* Loading Shared Libraries:: Loading shared libraries into your
program.
* Obsolete:: Obsolete Options and/or features.
* Undocumented:: Undocumented Options and Features.
* Invoking Summary:: Invocation summary.
* Regexp Usage:: How to Use Regular Expressions.
* Escape Sequences:: How to write nonprinting characters.
* Regexp Operators:: Regular Expression Operators.
* Regexp Operator Details:: The actual details.
* Interval Expressions:: Notes on interval expressions.
* Bracket Expressions:: What can go between @samp{[...]}.
* Leftmost Longest:: How much text matches.
* Computed Regexps:: Using Dynamic Regexps.
* GNU Regexp Operators:: Operators specific to GNU software.
* Case-sensitivity:: How to do case-insensitive matching.
* Regexp Summary:: Regular expressions summary.
* Records:: Controlling how data is split into
records.
* awk split records:: How standard @command{awk} splits
records.
* gawk split records:: How @command{gawk} splits records.
* Fields:: An introduction to fields.
* Nonconstant Fields:: Nonconstant Field Numbers.
* Changing Fields:: Changing the Contents of a Field.
* Field Separators:: The field separator and how to change
it.
* Default Field Splitting:: How fields are normally separated.
* Regexp Field Splitting:: Using regexps as the field separator.
* Single Character Fields:: Making each character a separate
field.
* Command Line Field Separator:: Setting @code{FS} from the command
line.
* Full Line Fields:: Making the full line be a single
field.
* Field Splitting Summary:: Some final points and a summary table.
* Constant Size:: Reading constant width data.
* Fixed width data:: Processing fixed-width data.
* Skipping intervening:: Skipping intervening fields.
* Allowing trailing data:: Capturing optional trailing data.
* Fields with fixed data:: Field values with fixed-width data.
* Splitting By Content:: Defining Fields By Content
* More CSV:: More on CSV files.
* Testing field creation:: Checking how @command{gawk} is
splitting records.
* Multiple Line:: Reading multiline records.
* Getline:: Reading files under explicit program
control using the @code{getline}
function.
* Plain Getline:: Using @code{getline} with no
arguments.
* Getline/Variable:: Using @code{getline} into a variable.
* Getline/File:: Using @code{getline} from a file.
* Getline/Variable/File:: Using @code{getline} into a variable
from a file.
* Getline/Pipe:: Using @code{getline} from a pipe.
* Getline/Variable/Pipe:: Using @code{getline} into a variable
from a pipe.
* Getline/Coprocess:: Using @code{getline} from a coprocess.
* Getline/Variable/Coprocess:: Using @code{getline} into a variable
from a coprocess.
* Getline Notes:: Important things to know about
@code{getline}.
* Getline Summary:: Summary of @code{getline} Variants.
* Read Timeout:: Reading input with a timeout.
* Retrying Input:: Retrying input after certain errors.
* Command-line directories:: What happens if you put a directory on
the command line.
* Input Summary:: Input summary.
* Input Exercises:: Exercises.
* Print:: The @code{print} statement.
* Print Examples:: Simple examples of @code{print}
statements.
* Output Separators:: The output separators and how to
change them.
* OFMT:: Controlling Numeric Output With
@code{print}.
* Printf:: The @code{printf} statement.
* Basic Printf:: Syntax of the @code{printf} statement.
* Control Letters:: Format-control letters.
* Format Modifiers:: Format-specification modifiers.
* Printf Examples:: Several examples.
* Redirection:: How to redirect output to multiple
files and pipes.
* Special FD:: Special files for I/O.
* Special Files:: File name interpretation in
@command{gawk}. @command{gawk} allows
access to inherited file descriptors.
* Other Inherited Files:: Accessing other open files with
@command{gawk}.
* Special Network:: Special files for network
communications.
* Special Caveats:: Things to watch out for.
* Close Files And Pipes:: Closing Input and Output Files and
Pipes.
* Nonfatal:: Enabling Nonfatal Output.
* Output Summary:: Output summary.
* Output Exercises:: Exercises.
* Values:: Constants, Variables, and Regular
Expressions.
* Constants:: String, numeric and regexp constants.
* Scalar Constants:: Numeric and string constants.
* Nondecimal-numbers:: What are octal and hex numbers.
* Regexp Constants:: Regular Expression constants.
* Using Constant Regexps:: When and how to use a regexp constant.
* Standard Regexp Constants:: Regexp constants in standard
@command{awk}.
* Strong Regexp Constants:: Strongly typed regexp constants.
* Variables:: Variables give names to values for
later use.
* Using Variables:: Using variables in your programs.
* Assignment Options:: Setting variables on the command line
and a summary of command-line syntax.
This is an advanced method of input.
* Conversion:: The conversion of strings to numbers
and vice versa.
* Strings And Numbers:: How @command{awk} Converts Between
Strings And Numbers.
* Locale influences conversions:: How the locale may affect conversions.
* All Operators:: @command{gawk}'s operators.
* Arithmetic Ops:: Arithmetic operations (@samp{+},
@samp{-}, etc.)
* Concatenation:: Concatenating strings.
* Assignment Ops:: Changing the value of a variable or a
field.
* Increment Ops:: Incrementing the numeric value of a
variable.
* Truth Values and Conditions:: Testing for true and false.
* Truth Values:: What is ``true'' and what is
``false''.
* Typing and Comparison:: How variables acquire types and how
this affects comparison of numbers and
strings with @samp{<}, etc.
* Variable Typing:: String type versus numeric type.
* Comparison Operators:: The comparison operators.
* POSIX String Comparison:: String comparison with POSIX rules.
* Boolean Ops:: Combining comparison expressions using
boolean operators @samp{||} (``or''),
@samp{&&} (``and'') and @samp{!}
(``not'').
* Conditional Exp:: Conditional expressions select between
two subexpressions under control of a
third subexpression.
* Function Calls:: A function call is an expression.
* Precedence:: How various operators nest.
* Locales:: How the locale affects things.
* Expressions Summary:: Expressions summary.
* Pattern Overview:: What goes into a pattern.
* Regexp Patterns:: Using regexps as patterns.
* Expression Patterns:: Any expression can be used as a
pattern.
* Ranges:: Pairs of patterns specify record
ranges.
* BEGIN/END:: Specifying initialization and cleanup
rules.
* Using BEGIN/END:: How and why to use BEGIN/END rules.
* I/O And BEGIN/END:: I/O issues in BEGIN/END rules.
* BEGINFILE/ENDFILE:: Two special patterns for advanced
control.
* Empty:: The empty pattern, which matches every
record.
* Using Shell Variables:: How to use shell variables with
@command{awk}.
* Action Overview:: What goes into an action.
* Statements:: Describes the various control
statements in detail.
* If Statement:: Conditionally execute some
@command{awk} statements.
* While Statement:: Loop until some condition is
satisfied.
* Do Statement:: Do specified action while looping
until some condition is satisfied.
* For Statement:: Another looping statement, that
provides initialization and increment
clauses.
* Switch Statement:: Switch/case evaluation for conditional
execution of statements based on a
value.
* Break Statement:: Immediately exit the innermost
enclosing loop.
* Continue Statement:: Skip to the end of the innermost
enclosing loop.
* Next Statement:: Stop processing the current input
record.
* Nextfile Statement:: Stop processing the current file.
* Exit Statement:: Stop execution of @command{awk}.
* Built-in Variables:: Summarizes the predefined variables.
* User-modified:: Built-in variables that you change to
control @command{awk}.
* Auto-set:: Built-in variables where @command{awk}
gives you information.
* ARGC and ARGV:: Ways to use @code{ARGC} and
@code{ARGV}.
* Pattern Action Summary:: Patterns and Actions summary.
* Array Basics:: The basics of arrays.
* Array Intro:: Introduction to Arrays
* Reference to Elements:: How to examine one element of an
array.
* Assigning Elements:: How to change an element of an array.
* Array Example:: Basic Example of an Array
* Scanning an Array:: A variation of the @code{for}
statement. It loops through the
indices of an array's existing
elements.
* Controlling Scanning:: Controlling the order in which arrays
are scanned.
* Numeric Array Subscripts:: How to use numbers as subscripts in
@command{awk}.
* Uninitialized Subscripts:: Using Uninitialized variables as
subscripts.
* Delete:: The @code{delete} statement removes an
element from an array.
* Multidimensional:: Emulating multidimensional arrays in
@command{awk}.
* Multiscanning:: Scanning multidimensional arrays.
* Arrays of Arrays:: True multidimensional arrays.
* Arrays Summary:: Summary of arrays.
* Built-in:: Summarizes the built-in functions.
* Calling Built-in:: How to call built-in functions.
* Numeric Functions:: Functions that work with numbers,
including @code{int()}, @code{sin()}
and @code{rand()}.
* String Functions:: Functions for string manipulation,
such as @code{split()}, @code{match()}
and @code{sprintf()}.
* Gory Details:: More than you want to know about
@samp{\} and @samp{&} with
@code{sub()}, @code{gsub()}, and
@code{gensub()}.
* I/O Functions:: Functions for files and shell
commands.
* Time Functions:: Functions for dealing with timestamps.
* Bitwise Functions:: Functions for bitwise operations.
* Type Functions:: Functions for type information.
* I18N Functions:: Functions for string translation.
* User-defined:: Describes User-defined functions in
detail.
* Definition Syntax:: How to write definitions and what they
mean.
* Function Example:: An example function definition and
what it does.
* Function Calling:: Calling user-defined functions.
* Calling A Function:: Don't use spaces.
* Variable Scope:: Controlling variable scope.
* Pass By Value/Reference:: Passing parameters.
* Function Caveats:: Other points to know about functions.
* Return Statement:: Specifying the value a function
returns.
* Dynamic Typing:: How variable types can change at
runtime.
* Indirect Calls:: Choosing the function to call at
runtime.
* Functions Summary:: Summary of functions.
* Library Names:: How to best name private global
variables in library functions.
* General Functions:: Functions that are of general use.
* Strtonum Function:: A replacement for the built-in
@code{strtonum()} function.
* Assert Function:: A function for assertions in
@command{awk} programs.
* Round Function:: A function for rounding if
@code{sprintf()} does not do it
correctly.
* Cliff Random Function:: The Cliff Random Number Generator.
* Ordinal Functions:: Functions for using characters as
numbers and vice versa.
* Join Function:: A function to join an array into a
string.
* Getlocaltime Function:: A function to get formatted times.
* Readfile Function:: A function to read an entire file at
once.
* Shell Quoting:: A function to quote strings for the
shell.
* Data File Management:: Functions for managing command-line
data files.
* Filetrans Function:: A function for handling data file
transitions.
* Rewind Function:: A function for rereading the current
file.
* File Checking:: Checking that data files are readable.
* Empty Files:: Checking for zero-length files.
* Ignoring Assigns:: Treating assignments as file names.
* Getopt Function:: A function for processing command-line
arguments.
* Passwd Functions:: Functions for getting user
information.
* Group Functions:: Functions for getting group
information.
* Walking Arrays:: A function to walk arrays of arrays.
* Library Functions Summary:: Summary of library functions.
* Library Exercises:: Exercises.
* Running Examples:: How to run these examples.
* Clones:: Clones of common utilities.
* Cut Program:: The @command{cut} utility.
* Egrep Program:: The @command{egrep} utility.
* Id Program:: The @command{id} utility.
* Split Program:: The @command{split} utility.
* Tee Program:: The @command{tee} utility.
* Uniq Program:: The @command{uniq} utility.
* Wc Program:: The @command{wc} utility.
* Miscellaneous Programs:: Some interesting @command{awk}
programs.
* Dupword Program:: Finding duplicated words in a
document.
* Alarm Program:: An alarm clock.
* Translate Program:: A program similar to the @command{tr}
utility.
* Labels Program:: Printing mailing labels.
* Word Sorting:: A program to produce a word usage
count.
* History Sorting:: Eliminating duplicate entries from a
history file.
* Extract Program:: Pulling out programs from Texinfo
source files.
* Simple Sed:: A Simple Stream Editor.
* Igawk Program:: A wrapper for @command{awk} that
includes files.
* Anagram Program:: Finding anagrams from a dictionary.
* Signature Program:: People do amazing things with too much
time on their hands.
* Programs Summary:: Summary of programs.
* Programs Exercises:: Exercises.
* Nondecimal Data:: Allowing nondecimal input data.
* Array Sorting:: Facilities for controlling array
traversal and sorting arrays.
* Controlling Array Traversal:: How to use PROCINFO["sorted_in"].
* Array Sorting Functions:: How to use @code{asort()} and
@code{asorti()}.
* Two-way I/O:: Two-way communications with another
process.
* TCP/IP Networking:: Using @command{gawk} for network
programming.
* Profiling:: Profiling your @command{awk} programs.
* Advanced Features Summary:: Summary of advanced features.
* I18N and L10N:: Internationalization and Localization.
* Explaining gettext:: How GNU @command{gettext} works.
* Programmer i18n:: Features for the programmer.
* Translator i18n:: Features for the translator.
* String Extraction:: Extracting marked strings.
* Printf Ordering:: Rearranging @code{printf} arguments.
* I18N Portability:: @command{awk}-level portability
issues.
* I18N Example:: A simple i18n example.
* Gawk I18N:: @command{gawk} is also
internationalized.
* I18N Summary:: Summary of I18N stuff.
* Debugging:: Introduction to @command{gawk}
debugger.
* Debugging Concepts:: Debugging in General.
* Debugging Terms:: Additional Debugging Concepts.
* Awk Debugging:: Awk Debugging.
* Sample Debugging Session:: Sample debugging session.
* Debugger Invocation:: How to Start the Debugger.
* Finding The Bug:: Finding the Bug.
* List of Debugger Commands:: Main debugger commands.
* Breakpoint Control:: Control of Breakpoints.
* Debugger Execution Control:: Control of Execution.
* Viewing And Changing Data:: Viewing and Changing Data.
* Execution Stack:: Dealing with the Stack.
* Debugger Info:: Obtaining Information about the
Program and the Debugger State.
* Miscellaneous Debugger Commands:: Miscellaneous Commands.
* Readline Support:: Readline support.
* Limitations:: Limitations and future plans.
* Debugging Summary:: Debugging summary.
* Global Namespace:: The global namespace in standard
@command{awk}.
* Qualified Names:: How to qualify names with a namespace.
* Default Namespace:: The default namespace.
* Changing The Namespace:: How to change the namespace.
* Naming Rules:: Namespace and Component Naming Rules.
* Internal Name Management:: How names are stored internally.
* Namespace Example:: An example of code using a namespace.
* Namespace And Features:: Namespaces and other @command{gawk}
features.
* Namespace Summary:: Summarizing namespaces.
* Computer Arithmetic:: A quick intro to computer math.
* Math Definitions:: Defining terms used.
* MPFR features:: The MPFR features in @command{gawk}.
* FP Math Caution:: Things to know.
* Inexactness of computations:: Floating point math is not exact.
* Inexact representation:: Numbers are not exactly represented.
* Comparing FP Values:: How to compare floating point values.
* Errors accumulate:: Errors get bigger as they go.
* Getting Accuracy:: Getting more accuracy takes some work.
* Try To Round:: Add digits and round.
* Setting precision:: How to set the precision.
* Setting the rounding mode:: How to set the rounding mode.
* Arbitrary Precision Integers:: Arbitrary Precision Integer Arithmetic
with @command{gawk}.
* Checking for MPFR:: How to check if MPFR is available.
* POSIX Floating Point Problems:: Standards Versus Existing Practice.
* Floating point summary:: Summary of floating point discussion.
* Extension Intro:: What is an extension.
* Plugin License:: A note about licensing.
* Extension Mechanism Outline:: An outline of how it works.
* Extension API Description:: A full description of the API.
* Extension API Functions Introduction:: Introduction to the API functions.
* General Data Types:: The data types.
* Memory Allocation Functions:: Functions for allocating memory.
* Constructor Functions:: Functions for creating values.
* Registration Functions:: Functions to register things with
@command{gawk}.
* Extension Functions:: Registering extension functions.
* Exit Callback Functions:: Registering an exit callback.
* Extension Version String:: Registering a version string.
* Input Parsers:: Registering an input parser.
* Output Wrappers:: Registering an output wrapper.
* Two-way processors:: Registering a two-way processor.
* Printing Messages:: Functions for printing messages.
* Updating @code{ERRNO}:: Functions for updating @code{ERRNO}.
* Requesting Values:: How to get a value.
* Accessing Parameters:: Functions for accessing parameters.
* Symbol Table Access:: Functions for accessing global
variables.
* Symbol table by name:: Accessing variables by name.
* Symbol table by cookie:: Accessing variables by ``cookie''.
* Cached values:: Creating and using cached values.
* Array Manipulation:: Functions for working with arrays.
* Array Data Types:: Data types for working with arrays.
* Array Functions:: Functions for working with arrays.
* Flattening Arrays:: How to flatten arrays.
* Creating Arrays:: How to create and populate arrays.
* Redirection API:: How to access and manipulate
redirections.
* Extension API Variables:: Variables provided by the API.
* Extension Versioning:: API Version information.
* Extension GMP/MPFR Versioning:: Version information about GMP and
MPFR.
* Extension API Informational Variables:: Variables providing information about
@command{gawk}'s invocation.
* Extension API Boilerplate:: Boilerplate code for using the API.
* Changes from API V1:: Changes from V1 of the API.
* Finding Extensions:: How @command{gawk} finds compiled
extensions.
* Extension Example:: Example C code for an extension.
* Internal File Description:: What the new functions will do.
* Internal File Ops:: The code for internal file operations.
* Using Internal File Ops:: How to use an external extension.
* Extension Samples:: The sample extensions that ship with
@command{gawk}.
* Extension Sample File Functions:: The file functions sample.
* Extension Sample Fnmatch:: An interface to @code{fnmatch()}.
* Extension Sample Fork:: An interface to @code{fork()} and
other process functions.
* Extension Sample Inplace:: Enabling in-place file editing.
* Extension Sample Ord:: Character to value to character
conversions.
* Extension Sample Readdir:: An interface to @code{readdir()}.
* Extension Sample Revout:: Reversing output sample output
wrapper.
* Extension Sample Rev2way:: Reversing data sample two-way
processor.
* Extension Sample Read write array:: Serializing an array to a file.
* Extension Sample Readfile:: Reading an entire file into a string.
* Extension Sample Time:: An interface to @code{gettimeofday()}
and @code{sleep()}.
* Extension Sample API Tests:: Tests for the API.
* gawkextlib:: The @code{gawkextlib} project.
* Extension summary:: Extension summary.
* Extension Exercises:: Exercises.
* V7/SVR3.1:: The major changes between V7 and
System V Release 3.1.
* SVR4:: Minor changes between System V
Releases 3.1 and 4.
* POSIX:: New features from the POSIX standard.
* BTL:: New features from Brian Kernighan's
version of @command{awk}.
* POSIX/GNU:: The extensions in @command{gawk} not
in POSIX @command{awk}.
* Feature History:: The history of the features in
@command{gawk}.
* Common Extensions:: Common Extensions Summary.
* Ranges and Locales:: How locales used to affect regexp
ranges.
* Contributors:: The major contributors to
@command{gawk}.
* History summary:: History summary.
* Gawk Distribution:: What is in the @command{gawk}
distribution.
* Getting:: How to get the distribution.
* Extracting:: How to extract the distribution.
* Distribution contents:: What is in the distribution.
* Unix Installation:: Installing @command{gawk} under
various versions of Unix.
* Quick Installation:: Compiling @command{gawk} under Unix.
* Shell Startup Files:: Shell convenience functions.
* Additional Configuration Options:: Other compile-time options.
* Configuration Philosophy:: How it's all supposed to work.
* Non-Unix Installation:: Installation on Other Operating
Systems.
* PC Installation:: Installing and Compiling
@command{gawk} on Microsoft Windows.
* PC Binary Installation:: Installing a prepared distribution.
* PC Compiling:: Compiling @command{gawk} for
Windows32.
* PC Using:: Running @command{gawk} on Windows32.
* Cygwin:: Building and running @command{gawk}
for Cygwin.
* MSYS:: Using @command{gawk} In The MSYS
Environment.
* VMS Installation:: Installing @command{gawk} on VMS.
* VMS Compilation:: How to compile @command{gawk} under
VMS.
* VMS Dynamic Extensions:: Compiling @command{gawk} dynamic
extensions on VMS.
* VMS Installation Details:: How to install @command{gawk} under
VMS.
* VMS Running:: How to run @command{gawk} under VMS.
* VMS GNV:: The VMS GNV Project.
* VMS Old Gawk:: An old version comes with some VMS
systems.
* Bugs:: Reporting Problems and Bugs.
* Bug address:: Where to send reports to.
* Usenet:: Where not to send reports to.
* Maintainers:: Maintainers of non-*nix ports.
* Other Versions:: Other freely available @command{awk}
implementations.
* Installation summary:: Summary of installation.
* Compatibility Mode:: How to disable certain @command{gawk}
extensions.
* Additions:: Making Additions To @command{gawk}.
* Accessing The Source:: Accessing the Git repository.
* Adding Code:: Adding code to the main body of
@command{gawk}.
* New Ports:: Porting @command{gawk} to a new
operating system.
* Derived Files:: Why derived files are kept in the Git
repository.
* Future Extensions:: New features that may be implemented
one day.
* Implementation Limitations:: Some limitations of the
implementation.
* Extension Design:: Design notes about the extension API.
* Old Extension Problems:: Problems with the old mechanism.
* Extension New Mechanism Goals:: Goals for the new mechanism.
* Extension Other Design Decisions:: Some other design decisions.
* Extension Future Growth:: Some room for future growth.
* Notes summary:: Summary of implementation notes.
* Basic High Level:: The high level view.
* Basic Data Typing:: A very quick intro to data types.
@end detailmenu
@end menu
@c dedication for Info file
@ifinfo
To my parents, for their love, and for the wonderful
example they set for me.
@sp 1
To my wife Miriam, for making me complete.
Thank you for building your life together with me.
@sp 1
To our children Chana, Rivka, Nachum and Malka,
for enrichening our lives in innumerable ways.
@end ifinfo
@summarycontents
@contents
@node Foreword3
@unnumbered Foreword to the Third Edition
@c This bit is post-processed by a script which turns the chapter
@c tag into a preface tag, and moves this stuff to before the title.
@c Bleah.
@docbook
<prefaceinfo>
<author>
<firstname>Michael</firstname>
<surname>Brennan</surname>
<!-- can't put mawk into command tags. sigh. -->
<affiliation><jobtitle>Author of mawk</jobtitle></affiliation>
</author>
<date>March 2001</date>
</prefaceinfo>
@end docbook
Arnold Robbins and I are good friends. We were introduced
@c 11 years ago
in 1990
by circumstances---and our favorite programming language, AWK.
The circumstances started a couple of years
earlier. I was working at a new job and noticed an unplugged
Unix computer sitting in the corner. No one knew how to use it,
and neither did I. However,
a couple of days later, it was running, and
I was @code{root} and the one-and-only user.
That day, I began the transition from statistician to Unix programmer.
On one of many trips to the library or bookstore in search of
books on Unix, I found the gray AWK book, a.k.a.@:
Alfred V.@: Aho, Brian W.@: Kernighan, and
Peter J.@: Weinberger's @cite{The AWK Programming Language} (Addison-Wesley,
1988). @command{awk}'s simple programming paradigm---find a pattern in the
input and then perform an action---often reduced complex or tedious
data manipulations to a few lines of code. I was excited to try my
hand at programming in AWK.
Alas, the @command{awk} on my computer was a limited version of the
language described in the gray book. I discovered that my computer
had ``old @command{awk}'' and the book described
``new @command{awk}.''
I learned that this was typical; the old version refused to step
aside or relinquish its name. If a system had a new @command{awk}, it was
invariably called @command{nawk}, and few systems had it.
The best way to get a new @command{awk} was to @command{ftp} the source code for
@command{gawk} from @code{prep.ai.mit.edu}. @command{gawk} was a version of
new @command{awk} written by David Trueman and Arnold, and available under
the GNU General Public License.
(Incidentally,
it's no longer difficult to find a new @command{awk}. @command{gawk} ships with
GNU/Linux, and you can download binaries or source code for almost
any system; my wife uses @command{gawk} on her VMS box.)
My Unix system started out unplugged from the wall; it certainly was not
plugged into a network. So, oblivious to the existence of @command{gawk}
and the Unix community in general, and desiring a new @command{awk}, I wrote
my own, called @command{mawk}.
Before I was finished, I knew about @command{gawk},
but it was too late to stop, so I eventually posted
to a @code{comp.sources} newsgroup.
A few days after my posting, I got a friendly email
from Arnold introducing
himself. He suggested we share design and algorithms and
attached a draft of the POSIX standard so
that I could update @command{mawk} to support language extensions added
after publication of @cite{The AWK Programming Language}.
Frankly, if our roles had
been reversed, I would not have been so open and we probably would
have never met. I'm glad we did meet.
He is an AWK expert's AWK expert and a genuinely nice person.
Arnold contributes significant amounts of his
expertise and time to the Free Software Foundation.
This book is the @command{gawk} reference manual, but at its core it
is a book about AWK programming that
will appeal to a wide audience.
It is a definitive reference to the AWK language as defined by the
1987 Bell Laboratories release and codified in the 1992 POSIX Utilities
standard.
On the other hand, the novice AWK programmer can study
a wealth of practical programs that emphasize
the power of AWK's basic idioms:
data-driven control flow, pattern matching with regular expressions,
and associative arrays.
Those looking for something new can try out @command{gawk}'s
interface to network protocols via special @file{/inet} files.
The programs in this book make clear that an AWK program is
typically much smaller and faster to develop than
a counterpart written in C.
Consequently, there is often a payoff to prototyping an
algorithm or design in AWK to get it running quickly and expose
problems early. Often, the interpreted performance is adequate
and the AWK prototype becomes the product.
The new @command{pgawk} (profiling @command{gawk}), produces
program execution counts.
I recently experimented with an algorithm that for
@ifnotdocbook
@math{n}
@end ifnotdocbook
@ifdocbook
@i{n}
@end ifdocbook
lines of input, exhibited
@tex
$\sim\! Cn^2$
@end tex
@ifnottex
@ifnotdocbook
~ C n^2
@end ifnotdocbook
@end ifnottex
@docbook
<emphasis>∼ Cn<superscript>2</superscript></emphasis>
@end docbook
performance, while
theory predicted
@tex
$\sim\! Cn\log n$
@end tex
@ifnottex
@ifnotdocbook
~ C n log n
@end ifnotdocbook
@end ifnottex
@docbook
<emphasis>∼ Cn log n</emphasis>
@end docbook
behavior. A few minutes poring
over the @file{awkprof.out} profile pinpointed the problem to
a single line of code. @command{pgawk} is a welcome addition to
my programmer's toolbox.
Arnold has distilled over a decade of experience writing and
using AWK programs, and developing @command{gawk}, into this book. If you use
AWK or want to learn how, then read this book.
@ifnotdocbook
@cindex Brennan, Michael
@display
Michael Brennan
Author of @command{mawk}
March 2001
@end display
@end ifnotdocbook
@node Foreword4
@unnumbered Foreword to the Fourth Edition
@c This bit is post-processed by a script which turns the chapter
@c tag into a preface tag, and moves this stuff to before the title.
@c Bleah.
@docbook
<prefaceinfo>
<author>
<firstname>Michael</firstname>
<surname>Brennan</surname>
<!-- can't put mawk into command tags. sigh. -->
<affiliation><jobtitle>Author of mawk</jobtitle></affiliation>
</author>
<date>October 2014</date>
</prefaceinfo>
@end docbook
Some things don't change. Thirteen years ago I wrote:
``If you use AWK or want to learn how, then read this book.''
True then, and still true today.
Learning to use a programming language is about more than mastering the
syntax. One needs to acquire an understanding of how to use the
features of the language to solve practical programming problems.
A focus of this book is many examples that show how to use AWK.
Some things do change. Our computers are much faster and have more memory.
Consequently, speed and storage inefficiencies of a high-level language
matter less. Prototyping in AWK and then rewriting in C for performance
reasons happens less, because more often the prototype is fast enough.
Of course, there are computing operations that are best done in C or C++.
With @command{gawk} 4.1 and later, you do not have to choose between writing
your program in AWK or in C/C++. You can write most of your
program in AWK and the aspects that require C/C++ capabilities can be written
in C/C++, and then the pieces glued together when the @command{gawk} module loads
the C/C++ module as a dynamic plug-in.
@c Chapter 16
@ref{Dynamic Extensions},
has all the
details, and, as expected, many examples to help you learn the ins and outs.
I enjoy programming in AWK and had fun (re)reading this book.
I think you will too.
@ifnotdocbook
@cindex Brennan, Michael
@display
Michael Brennan
Author of @command{mawk}
October 2014
@end display
@end ifnotdocbook
@node Preface
@unnumbered Preface
@c I saw a comment somewhere that the preface should describe the book itself,
@c and the introduction should describe what the book covers.
@c
@c 12/2000: Chuck wants the preface & intro combined.
@c This bit is post-processed by a script which turns the chapter
@c tag into a preface tag, and moves this stuff to before the title.
@c Bleah.
@docbook
<prefaceinfo>
<author>
<firstname>Arnold</firstname>
<surname>Robbins</surname>
<affiliation><jobtitle>Nof Ayalon</jobtitle></affiliation>
<affiliation><jobtitle>Israel</jobtitle></affiliation>
</author>
<date>February 2015</date>
</prefaceinfo>
@end docbook
@cindex @command{awk}
Several kinds of tasks occur repeatedly when working with text files.
You might want to extract certain lines and discard the rest. Or you
may need to make changes wherever certain patterns appear, but leave the
rest of the file alone. Such jobs are often easy with @command{awk}.
The @command{awk} utility interprets a special-purpose programming
language that makes it easy to handle simple data-reformatting jobs.
@cindex @command{gawk}
The GNU implementation of @command{awk} is called @command{gawk}; if you
invoke it with the proper options or environment variables,
it is fully compatible with
the POSIX@footnote{The 2018 POSIX standard is accessible online at
@w{@url{https://pubs.opengroup.org/onlinepubs/9699919799/}.}}
specification of the @command{awk} language
and with the Unix version of @command{awk} maintained
by Brian Kernighan.
This means that all
properly written @command{awk} programs should work with @command{gawk}.
So most of the time, we don't distinguish between @command{gawk} and other
@command{awk} implementations.
@cindex @command{awk} @subentry POSIX and @seealso{POSIX @command{awk}}
@cindex @command{awk} @subentry POSIX and
@cindex POSIX @subentry @command{awk} and
@cindex @command{gawk} @subentry @command{awk} and
@cindex @command{awk} @subentry @command{gawk} and
@cindex @command{awk} @subentry uses for
Using @command{awk} you can:
@itemize @value{BULLET}
@item
Manage small, personal databases
@item
Generate reports
@item
Validate data
@item
Produce indexes and perform other document-preparation tasks
@item
Experiment with algorithms that you can adapt later to other computer
languages
@end itemize
@cindex @command{awk} @seealso{@command{gawk}}
@cindex @command{gawk} @seealso{@command{awk}}
@cindex @command{gawk} @subentry uses for
In addition,
@command{gawk}
provides facilities that make it easy to:
@itemize @value{BULLET}
@item
Extract bits and pieces of data for processing
@item
Sort data
@item
Perform simple network communications
@item
Profile and debug @command{awk} programs
@item
Extend the language with functions written in C or C++
@end itemize
This @value{DOCUMENT} teaches you about the @command{awk} language and
how you can use it effectively. You should already be familiar with basic
system commands, such as @command{cat} and @command{ls},@footnote{These utilities
are available on POSIX-compliant systems, as well as on traditional
Unix-based systems. If you are using some other operating system, you still need to
be familiar with the ideas of I/O redirection and pipes.} as well as basic shell
facilities, such as input/output (I/O) redirection and pipes.
@cindex GNU @command{awk} @seeentry{@command{gawk}}
Implementations of the @command{awk} language are available for many
different computing environments. This @value{DOCUMENT}, while describing
the @command{awk} language in general, also describes the particular
implementation of @command{awk} called @command{gawk} (which stands for
``GNU @command{awk}''). @command{gawk} runs on a broad range of Unix systems,
ranging from Intel-architecture PC-based computers
up through large-scale systems.
@command{gawk} has also been ported to Mac OS X,
Microsoft Windows
(all versions),
and OpenVMS.@footnote{Some other, obsolete systems to which @command{gawk}
was once ported are no longer supported and the code for those systems
has been removed.}
@menu
* History:: The history of @command{gawk} and
@command{awk}.
* Names:: What name to use to find @command{awk}.
* This Manual:: Using this @value{DOCUMENT}. Includes sample
input files that you can use.
* Conventions:: Typographical Conventions.
* Manual History:: Brief history of the GNU project and this
@value{DOCUMENT}.
* How To Contribute:: Helping to save the world.
* Acknowledgments:: Acknowledgments.
@end menu
@node History
@unnumberedsec History of @command{awk} and @command{gawk}
@cindex recipe for a programming language
@cindex programming language, recipe for
@cindex sidebar @subentry Recipe for a Programming Language
@ifdocbook
@docbook
<sidebar><title>Recipe for a Programming Language</title>
@end docbook
@multitable {2 parts} {1 part @code{egrep}} {1 part @code{snobol}}
@item @tab 1 part @code{egrep} @tab 1 part @code{snobol}
@item @tab 2 parts @code{ed} @tab 3 parts C
@end multitable
Blend all parts well using @code{lex} and @code{yacc}.
Document minimally and release.
After eight years, add another part @code{egrep} and two
more parts C. Document very well and release.
@docbook
</sidebar>
@end docbook
@end ifdocbook
@ifnotdocbook
@cartouche
@center @b{Recipe for a Programming Language}
@multitable {2 parts} {1 part @code{egrep}} {1 part @code{snobol}}
@item @tab 1 part @code{egrep} @tab 1 part @code{snobol}
@item @tab 2 parts @code{ed} @tab 3 parts C
@end multitable
Blend all parts well using @code{lex} and @code{yacc}.
Document minimally and release.
After eight years, add another part @code{egrep} and two
more parts C. Document very well and release.
@end cartouche
@end ifnotdocbook
@cindex Aho, Alfred
@cindex Weinberger, Peter
@cindex Kernighan, Brian
@cindex @command{awk} @subentry history of
The name @command{awk} comes from the initials of its designers: Alfred V.@:
Aho, Peter J.@: Weinberger, and Brian W.@: Kernighan. The original version of
@command{awk} was written in 1977 at AT&T Bell Laboratories.
In 1985, a new version made the programming
language more powerful, introducing user-defined functions, multiple input
streams, and computed regular expressions.
This new version became widely available with Unix System V
Release 3.1 (1987).
The version in System V Release 4 (1989) added some new features and cleaned
up the behavior in some of the ``dark corners'' of the language.
The specification for @command{awk} in the POSIX Command Language
and Utilities standard further clarified the language.
Both the @command{gawk} designers and the original @command{awk} designers at Bell Laboratories
provided feedback for the POSIX specification.
@cindex Rubin, Paul
@cindex Fenlason, Jay
@cindex Trueman, David
Paul Rubin wrote @command{gawk} in 1986.
Jay Fenlason completed it, with advice from Richard Stallman. John Woods
contributed parts of the code as well. In 1988 and 1989, David Trueman, with
help from me, thoroughly reworked @command{gawk} for compatibility
with the newer @command{awk}.
Circa 1994, I became the primary maintainer.
Current development focuses on bug fixes,
performance improvements, standards compliance, and, occasionally, new features.
In May 1997, J@"urgen Kahrs felt the need for network access
from @command{awk}, and with a little help from me, set about adding
features to do this for @command{gawk}. At that time, he also
wrote the bulk of
@cite{@value{GAWKINETTITLE}}
(a separate document, available as part of the @command{gawk} distribution).
His code finally became part of the main @command{gawk} distribution
with @command{gawk} @value{PVERSION} 3.1.
John Haque rewrote the @command{gawk} internals, in the process providing
an @command{awk}-level debugger. This version became available as
@command{gawk} @value{PVERSION} 4.0 in 2011.
@xref{Contributors}
for a full list of those who have made important contributions to @command{gawk}.
@node Names
@unnumberedsec A Rose by Any Other Name
@cindex @command{awk} @subentry new vs.@: old
The @command{awk} language has evolved over the years. Full details are
provided in @ref{Language History}.
The language described in this @value{DOCUMENT}
is often referred to as ``new @command{awk}.''
By analogy, the original version of @command{awk} is
referred to as ``old @command{awk}.''
On most current systems, when you run the @command{awk} utility
you get some version of new @command{awk}.@footnote{Only
Solaris systems still use an old @command{awk} for the
default @command{awk} utility. A more modern @command{awk} lives in
@file{/usr/xpg6/bin} on these systems.} If your system's standard
@command{awk} is the old one, you will see something like this
if you try the following test program:
@example
@group
$ @kbd{awk 1 /dev/null}
@error{} awk: syntax error near line 1
@error{} awk: bailing out near line 1
@end group
@end example
@noindent
In this case, you should find a version of new @command{awk},
or just install @command{gawk}!
Throughout this @value{DOCUMENT}, whenever we refer to a language feature
that should be available in any complete implementation of POSIX @command{awk},
we simply use the term @command{awk}. When referring to a feature that is
specific to the GNU implementation, we use the term @command{gawk}.
@node This Manual
@unnumberedsec Using This Book
@cindex @command{awk} @subentry terms describing
The term @command{awk} refers to a particular program as well as to the language you
use to tell this program what to do. When we need to be careful, we call
the language ``the @command{awk} language,''
and the program ``the @command{awk} utility.''
This @value{DOCUMENT} explains
both how to write programs in the @command{awk} language and how to
run the @command{awk} utility.
The term ``@command{awk} program'' refers to a program written by you in
the @command{awk} programming language.
@cindex @command{gawk} @subentry @command{awk} and
@cindex @command{awk} @subentry @command{gawk} and
@cindex POSIX @command{awk}
Primarily, this @value{DOCUMENT} explains the features of @command{awk}
as defined in the POSIX standard. It does so in the context of the
@command{gawk} implementation. While doing so, it also
attempts to describe important differences between @command{gawk}
and other @command{awk}
@ifclear FOR_PRINT
implementations.@footnote{All such differences
appear in the index under the
entry ``differences in @command{awk} and @command{gawk}.''}
@end ifclear
@ifset FOR_PRINT
implementations.
@end ifset
Finally, it notes any @command{gawk} features that are not in
the POSIX standard for @command{awk}.
@ifnotinfo
This @value{DOCUMENT} has the difficult task of being both a tutorial and a reference.
If you are a novice, feel free to skip over details that seem too complex.
You should also ignore the many cross-references; they are for the
expert user and for the Info and
@uref{https://www.gnu.org/software/gawk/manual/, HTML}
versions of the @value{DOCUMENT}.
@end ifnotinfo
There are sidebars
scattered throughout the @value{DOCUMENT}.
They add a more complete explanation of points that are relevant, but not likely
to be of interest on first reading.
@ifclear FOR_PRINT
All appear in the index, under the heading ``sidebar.''
@end ifclear
Most of the time, the examples use complete @command{awk} programs.
Some of the more advanced @value{SECTION}s show only the part of the @command{awk}
program that illustrates the concept being described.
Although this @value{DOCUMENT} is aimed principally at people who have not been
exposed
to @command{awk}, there is a lot of information here that even the @command{awk}
expert should find useful. In particular, the description of POSIX
@command{awk} and the example programs in
@ref{Library Functions}, and
@ifnotdocbook
in
@end ifnotdocbook
@ref{Sample Programs},
should be of interest.
This @value{DOCUMENT} is split into several parts, as follows:
@c FULLXREF ON
@itemize @value{BULLET}
@item
Part I describes the @command{awk} language and the @command{gawk} program in detail.
It starts with the basics, and continues through all of the features of @command{awk}.
It contains the following chapters:
@c nested
@itemize @value{MINUS}
@item
@ref{Getting Started},
provides the essentials you need to know to begin using @command{awk}.
@item
@ref{Invoking Gawk},
describes how to run @command{gawk}, the meaning of its
command-line options, and how it finds @command{awk}
program source files.
@item
@ref{Regexp},
introduces regular expressions in general, and in particular the flavors
supported by POSIX @command{awk} and @command{gawk}.
@item
@ref{Reading Files},
describes how @command{awk} reads your data.
It introduces the concepts of records and fields, as well
as the @code{getline} command.
I/O redirection is first described here.
Network I/O is also briefly introduced here.
@item
@ref{Printing},
describes how @command{awk} programs can produce output with
@code{print} and @code{printf}.
@item
@ref{Expressions},
describes expressions, which are the basic building blocks
for getting most things done in a program.
@item
@ref{Patterns and Actions},
describes how to write patterns for matching records, actions for
doing something when a record is matched, and the predefined variables
@command{awk} and @command{gawk} use.
@item
@ref{Arrays},
covers @command{awk}'s one-and-only data structure: the associative array.
Deleting array elements and whole arrays is described, as well as
sorting arrays in @command{gawk}. The @value{CHAPTER} also describes how
@command{gawk} provides arrays of arrays.
@item
@ref{Functions},
describes the built-in functions @command{awk} and @command{gawk} provide,
as well as how to define your own functions. It also discusses how
@command{gawk} lets you call functions indirectly.
@end itemize
@item
Part II shows how to use @command{awk} and @command{gawk} for problem solving.
There is lots of code here for you to read and learn from.
This part contains the following chapters:
@c nested
@itemize @value{MINUS}
@item
@ref{Library Functions}, provides a number of functions meant to
be used from main @command{awk} programs.
@item
@ref{Sample Programs},
provides many sample @command{awk} programs.
@end itemize
Reading these two chapters allows you to see @command{awk}
solving real problems.
@item
Part III focuses on features specific to @command{gawk}.
It contains the following chapters:
@c nested
@itemize @value{MINUS}
@item
@ref{Advanced Features},
describes a number of advanced features.
Of particular note
are the abilities to control the order of array traversal,
have two-way communications with another process,
perform TCP/IP networking, and
profile your @command{awk} programs.
@item
@ref{Internationalization},
describes special features for translating program
messages into different languages at runtime.
@item
@ref{Debugger}, describes the @command{gawk} debugger.
@item
@ref{Namespaces}, describes how @command{gawk} allows variables and/or
functions of the same name to be in different namespaces.
@item
@ref{Arbitrary Precision Arithmetic},
describes advanced arithmetic facilities.
@item
@ref{Dynamic Extensions}, describes how to add new variables and
functions to @command{gawk} by writing extensions in C or C++.
@end itemize
@item
@ifclear FOR_PRINT
Part IV provides the appendices, the Glossary, and two licenses that cover
the @command{gawk} source code and this @value{DOCUMENT}, respectively.
It contains the following appendices:
@end ifclear
@ifset FOR_PRINT
Part IV provides the following appendices,
including the GNU General Public License:
@end ifset
@itemize @value{MINUS}
@item
@ref{Language History},
describes how the @command{awk} language has evolved since
its first release to the present. It also describes how @command{gawk}
has acquired features over time.
@item
@ref{Installation},
describes how to get @command{gawk}, how to compile it
on POSIX-compatible systems,
and how to compile and use it on different
non-POSIX systems. It also describes how to report bugs
in @command{gawk} and where to get other freely
available @command{awk} implementations.
@ifset FOR_PRINT
@item
@ref{Copying},
presents the license that covers the @command{gawk} source code.
@end ifset
@ifclear FOR_PRINT
@item
@ref{Notes},
describes how to disable @command{gawk}'s extensions, as
well as how to contribute new code to @command{gawk},
and some possible future directions for @command{gawk} development.
@item
@ref{Basic Concepts},
provides some very cursory background material for those who
are completely unfamiliar with computer programming.
@item
The @ref{Glossary}, defines most, if not all, of the significant terms used
throughout the @value{DOCUMENT}. If you find terms that you aren't familiar with,
try looking them up here.
@item
@ref{Copying}, and
@ref{GNU Free Documentation License},
present the licenses that cover the @command{gawk} source code
and this @value{DOCUMENT}, respectively.
@end ifclear
@end itemize
@end itemize
@ifset FOR_PRINT
The version of this @value{DOCUMENT} distributed with @command{gawk}
contains additional appendices and other end material.
To save space, we have omitted them from the
printed edition. You may find them online, as follows:
@itemize @value{BULLET}
@item
@uref{https://www.gnu.org/software/gawk/manual/html_node/Notes.html,
The appendix on implementation notes}
describes how to disable @command{gawk}'s extensions, how to contribute
new code to @command{gawk}, where to find information on some possible
future directions for @command{gawk} development, and the design decisions
behind the extension API.
@item
@uref{https://www.gnu.org/software/gawk/manual/html_node/Basic-Concepts.html,
The appendix on basic concepts}
provides some very cursory background material for those who
are completely unfamiliar with computer programming.
@item
@uref{https://www.gnu.org/software/gawk/manual/html_node/Glossary.html,
The Glossary}
defines most, if not all, of the significant terms used
throughout the @value{DOCUMENT}. If you find terms that you aren't familiar with,
try looking them up here.
@item
@uref{https://www.gnu.org/software/gawk/manual/html_node/GNU-Free-Documentation-License.html,
The GNU FDL}
is the license that covers this @value{DOCUMENT}.
@end itemize
@c ok not to use CHAPTER / SECTION here
Some of the chapters have exercise sections; these have also been
omitted from the print edition but are available online.
@end ifset
@c FULLXREF OFF
@node Conventions
@unnumberedsec Typographical Conventions
@cindex Texinfo
This @value{DOCUMENT} is written in @uref{https://www.gnu.org/software/texinfo/, Texinfo},
the GNU documentation formatting language.
A single Texinfo source file is used to produce both the printed and online
versions of the documentation.
@ifnotinfo
Because of this, the typographical conventions
are slightly different than in other books you may have read.
@end ifnotinfo
@ifinfo
This @value{SECTION} briefly documents the typographical conventions used in Texinfo.
@end ifinfo
Examples you would type at the command line are preceded by the common
shell primary and secondary prompts, @samp{$} and @samp{>}, respectively.
Input that you type is shown @kbd{like this}.
@c 8/2014: @print{} is stripped from the texi to make docbook.
@ifclear FOR_PRINT
Output from the command is preceded by the glyph ``@print{}''.
This typically represents the command's standard output.
@end ifclear
@ifset FOR_PRINT
Output from the command, usually its standard output, appears
@code{like this}.
@end ifset
Error messages and other output on the command's standard error are preceded
by the glyph ``@error{}''. For example:
@example
$ @kbd{echo hi on stdout}
@print{} hi on stdout
$ @kbd{echo hello on stderr 1>&2}
@error{} hello on stderr
@end example
@ifnotinfo
In the text, almost anything related to programming, such as
command names,
variable and function names, and string, numeric and regexp constants
appear in @code{this font}. Code fragments
appear in the same font and quoted, @samp{like this}.
Things that are replaced by the user or programmer
appear in @var{this font}.
Options look like this: @option{-f}.
@value{FFN}s are indicated like this: @file{/path/to/ourfile}.
@ifclear FOR_PRINT
Some things are
emphasized @emph{like this}, and if a point needs to be made
strongly, it is done @strong{like this}.
@end ifclear
The first occurrence of
a new term is usually its @dfn{definition} and appears in the same
font as the previous occurrence of ``definition'' in this sentence.
@end ifnotinfo
Characters that you type at the keyboard look @kbd{like this}. In particular,
there are special characters called ``control characters.'' These are
characters that you type by holding down both the @kbd{CONTROL} key and
another key, at the same time. For example, a @kbd{Ctrl-d} is typed
by first pressing and holding the @kbd{CONTROL} key, next
pressing the @kbd{d} key, and finally releasing both keys.
For the sake of brevity, throughout this @value{DOCUMENT}, we refer to
Brian Kernighan's version of @command{awk} as ``BWK @command{awk}.''
(@xref{Other Versions} for information on his and other versions.)
@ifset FOR_PRINT
@quotation NOTE
Notes of interest look like this.
@end quotation
@quotation CAUTION
Cautionary or warning notes look like this.
@end quotation
@end ifset
@c fakenode --- for prepinfo
@unnumberedsubsec Dark Corners
@cindex Kernighan, Brian
@quotation
@i{Dark corners are basically fractal---no matter how much
you illuminate, there's always a smaller but darker one.}
@author Brian Kernighan
@end quotation
@cindex d.c. @seeentry{dark corner}
@cindex dark corner
Until the POSIX standard (and @cite{@value{TITLE}}),
many features of @command{awk} were either poorly documented or not
documented at all. Descriptions of such features
(often called ``dark corners'') are noted in this @value{DOCUMENT} with
@iftex
the picture of a flashlight in the margin, as shown here.
@value{DARKCORNER}
@end iftex
@ifnottex
``(d.c.).''
@end ifnottex
@ifclear FOR_PRINT
They also appear in the index under the heading ``dark corner.''
@end ifclear
But, as noted by the opening quote, any coverage of dark
corners is by definition incomplete.
@cindex c.e. @seeentry{common extensions}
Extensions to the standard @command{awk} language that are supported by
more than one @command{awk} implementation are marked
@ifclear FOR_PRINT
``@value{COMMONEXT},'' and listed in the index under ``common extensions''
and ``extensions, common.''
@end ifclear
@ifset FOR_PRINT
``@value{COMMONEXT}'' for ``common extension.''
@end ifset
@node Manual History
@unnumberedsec The GNU Project and This Book
@cindex FSF (Free Software Foundation)
@cindex Free Software Foundation (FSF)
@cindex Stallman, Richard
The Free Software Foundation (FSF) is a nonprofit organization dedicated
to the production and distribution of freely distributable software.
It was founded by Richard M.@: Stallman, the author of the original
Emacs editor. GNU Emacs is the most widely used version of Emacs today.
@cindex GNU Project
@cindex GPL (General Public License)
@cindex GNU General Public License @seeentry{GPL}
@cindex General Public License @seeentry{GPL}
@cindex documentation @subentry online
The GNU@footnote{GNU stands for ``GNU's Not Unix.''}
Project is an ongoing effort on the part of the Free Software
Foundation to create a complete, freely distributable, POSIX-compliant
computing environment.
The FSF uses the GNU General Public License (GPL) to ensure that
its software's
source code is always available to the end user.
@ifclear FOR_PRINT
A copy of the GPL is included
@ifnotinfo
in this @value{DOCUMENT}
@end ifnotinfo
for your reference
(@pxref{Copying}).
@end ifclear
The GPL applies to the C language source code for @command{gawk}.
To find out more about the FSF and the GNU Project online,
see @uref{https://www.gnu.org, the GNU Project's home page}.
This @value{DOCUMENT} may also be read from
@uref{https://www.gnu.org/software/gawk/manual/, GNU's website}.
@ifclear FOR_PRINT
A shell, an editor (Emacs), highly portable optimizing C, C++, and
Objective-C compilers, a symbolic debugger and dozens of large and
small utilities (such as @command{gawk}), have all been completed and are
freely available. The GNU operating
system kernel (the HURD), has been released but remains in an early
stage of development.
@cindex Linux @seeentry{GNU/Linux}
@cindex GNU/Linux
@cindex operating systems @subentry BSD-based
Until the GNU operating system is more fully developed, you should
consider using GNU/Linux, a freely distributable, Unix-like operating
system for Intel,
Power Architecture,
Sun SPARC, IBM S/390, and other
systems.@footnote{The terminology ``GNU/Linux'' is explained
in the @ref{Glossary}.}
Many GNU/Linux distributions are
available for download from the Internet.
@end ifclear
@ifnotinfo
The @value{DOCUMENT} you are reading is actually free---at least, the
information in it is free to anyone. The machine-readable
source code for the @value{DOCUMENT} comes with @command{gawk}.
@ifclear FOR_PRINT
(Take a moment to check the Free Documentation
License in @ref{GNU Free Documentation License}.)
@end ifclear
@end ifnotinfo
@cindex Close, Diane
The @value{DOCUMENT} itself has gone through multiple previous editions.
Paul Rubin wrote the very first draft of @cite{The GAWK Manual};
it was around 40 pages long.
Diane Close and Richard Stallman improved it, yielding a
version that was
around 90 pages and barely described the original, ``old''
version of @command{awk}.
I started working with that version in the fall of 1988.
As work on it progressed,
the FSF published several preliminary versions (numbered 0.@var{x}).
In 1996, edition 1.0 was released with @command{gawk} 3.0.0.
The FSF published the first two editions under
the title @cite{The GNU Awk User's Guide}.
@ifset FOR_PRINT
SSC published two editions of the @value{DOCUMENT} under the
title @cite{Effective awk Programming}, and O'Reilly published
the third edition in 2001.
@end ifset
This edition maintains the basic structure of the previous editions.
For FSF edition 4.0, the content was thoroughly reviewed and updated. All
references to @command{gawk} versions prior to 4.0 were removed.
Of significant note for that edition was the addition of @ref{Debugger}.
For FSF edition
@ifclear FOR_PRINT
5.0,
@end ifclear
@ifset FOR_PRINT
@value{EDITION}
(the fourth edition as published by O'Reilly),
@end ifset
the content has been reorganized into parts,
and the major new additions are @ref{Arbitrary Precision Arithmetic},
and @ref{Dynamic Extensions}.
This @value{DOCUMENT} will undoubtedly continue to evolve. If you
find an error in the @value{DOCUMENT}, please report it! @xref{Bugs}
for information on submitting problem reports electronically.
@ifset FOR_PRINT
@c fakenode --- for prepinfo
@unnumberedsec How to Stay Current
You may have a newer version of @command{gawk} than the
one described here. To find out what has changed,
you should first look at the @file{NEWS} file in the @command{gawk}
distribution, which provides a high-level summary of the changes in
each release.
You can then look at the @uref{https://www.gnu.org/software/gawk/manual/,
online version} of this @value{DOCUMENT} to read about any new features.
@end ifset
@ifclear FOR_PRINT
@node How To Contribute
@unnumberedsec How to Contribute
As the maintainer of GNU @command{awk}, I once thought that I would be
able to manage a collection of publicly available @command{awk} programs
and I even solicited contributions. Making things available on the Internet
helps keep the @command{gawk} distribution down to manageable size.
The initial collection of material, such as it is, is still available
at @uref{ftp://ftp.freefriends.org/arnold/Awkstuff}.
In the hopes of doing something more broad, I acquired the
@code{awklang.org} domain. Late in 2017, a volunteer took on the task
of managing it.
If you have written an interesting @command{awk} program, that
you would like to share with the rest of the world, please see
@uref{http://www.awklang.org} and use the ``Contact'' link.
If you have written a @command{gawk} extension, please see
@ref{gawkextlib}.
@end ifclear
@node Acknowledgments
@unnumberedsec Acknowledgments
The initial draft of @cite{The GAWK Manual} had the following acknowledgments:
@quotation
Many people need to be thanked for their assistance in producing this
manual. Jay Fenlason contributed many ideas and sample programs. Richard
Mlynarik and Robert Chassell gave helpful comments on drafts of this
manual. The paper @cite{A Supplemental Document for AWK} by John W.@:
Pierce of the Chemistry Department at UC San Diego, pinpointed several
issues relevant both to @command{awk} implementation and to this manual, that
would otherwise have escaped us.
@end quotation
@cindex Stallman, Richard
I would like to acknowledge Richard M.@: Stallman, for his vision of a
better world and for his courage in founding the FSF and starting the
GNU Project.
@ifclear FOR_PRINT
Earlier editions of this @value{DOCUMENT} had the following acknowledgements:
@end ifclear
@ifset FOR_PRINT
The previous edition of this @value{DOCUMENT} had
the following acknowledgements:
@end ifset
@quotation
The following people (in alphabetical order)
provided helpful comments on various
versions of this book:
Rick Adams,
Dr.@: Nelson H.F. Beebe,
Karl Berry,
Dr.@: Michael Brennan,
Rich Burridge,
Claire Cloutier,
Diane Close,
Scott Deifik,
Christopher (``Topher'') Eliot,
Jeffrey Friedl,
Dr.@: Darrel Hankerson,
Michal Jaegermann,
Dr.@: Richard J.@: LeBlanc,
Michael Lijewski,
Pat Rankin,
Miriam Robbins,
Mary Sheehan,
and
Chuck Toporek.
@cindex Berry, Karl
@cindex Chassell, Robert J.@:
@c @cindex Texinfo
Robert J.@: Chassell provided much valuable advice on
the use of Texinfo.
He also deserves special thanks for
convincing me @emph{not} to title this @value{DOCUMENT}
@cite{How to Gawk Politely}.
Karl Berry helped significantly with the @TeX{} part of Texinfo.
@cindex Hartholz @subentry Marshall
@cindex Hartholz @subentry Elaine
@cindex Schreiber @subentry Bert
@cindex Schreiber @subentry Rita
I would like to thank Marshall and Elaine Hartholz of Seattle and
Dr.@: Bert and Rita Schreiber of Detroit for large amounts of quiet vacation
time in their homes, which allowed me to make significant progress on
this @value{DOCUMENT} and on @command{gawk} itself.
@cindex Hughes, Phil
Phil Hughes of SSC
contributed in a very important way by loaning me his laptop GNU/Linux
system, not once, but twice, which allowed me to do a lot of work while
away from home.
@cindex Trueman, David
David Trueman deserves special credit; he has done a yeoman job
of evolving @command{gawk} so that it performs well and without bugs.
Although he is no longer involved with @command{gawk},
working with him on this project was a significant pleasure.
@cindex Drepper, Ulrich
@cindex GNITS mailing list
@cindex mailing list, GNITS
The intrepid members of the GNITS mailing list, and most notably Ulrich
Drepper, provided invaluable help and feedback for the design of the
internationalization features.
Chuck Toporek, Mary Sheehan, and Claire Cloutier of O'Reilly & Associates contributed
significant editorial help for this @value{DOCUMENT} for the
3.1 release of @command{gawk}.
@end quotation
@cindex Beebe, Nelson H.F.@:
@cindex Buening, Andreas
@cindex Collado, Manuel
@cindex Colombo, Antonio
@cindex Davies, Stephen
@cindex Deifik, Scott
@cindex Demaille, Akim
@cindex G., Daniel Richard
@cindex Guerrero, Juan Manuel
@cindex Hankerson, Darrel
@cindex Jaegermann, Michal
@cindex Kahrs, J@"urgen
@cindex Kasal, Stepan
@cindex Malmberg, John
@cindex Ramey, Chet
@cindex Rankin, Pat
@cindex Schorr, Andrew
@cindex Vinschen, Corinna
@cindex Zaretskii, Eli
Dr.@: Nelson Beebe,
Andreas Buening,
Dr.@: Manuel Collado,
Antonio Colombo,
Stephen Davies,
Scott Deifik,
Akim Demaille,
Daniel Richard G.,
Juan Manuel Guerrero,
Darrel Hankerson,
Michal Jaegermann,
J@"urgen Kahrs,
Stepan Kasal,
John Malmberg,
Chet Ramey,
Pat Rankin,
Andrew Schorr,
Corinna Vinschen,
and Eli Zaretskii
(in alphabetical order)
make up the current @command{gawk} ``crack portability team.'' Without
their hard work and help, @command{gawk} would not be nearly the robust,
portable program it is today. It has been and continues to be a pleasure
working with this team of fine people.
Notable code and documentation contributions were made by
a number of people. @xref{Contributors} for the full list.
@ifset FOR_PRINT
@cindex Oram, Andy
Thanks to Andy Oram of O'Reilly Media for initiating
the fourth edition and for his support during the work.
Thanks to Jasmine Kwityn for her copyediting work.
@end ifset
Thanks to Michael Brennan for the Forewords.
@cindex Duman, Patrice
@cindex Berry, Karl
@cindex Smith, Gavin
Thanks to Patrice Dumas for the new @command{makeinfo} program.
Thanks to Karl Berry for his past work on Texinfo, and
to Gavin Smith, who continues to work to improve
the Texinfo markup language.
@cindex Kernighan, Brian
@cindex Brennan, Michael
@cindex Day, Robert P.J.@:
Robert P.J.@: Day, Michael Brennan, and Brian Kernighan kindly acted as
reviewers for the 2015 edition of this @value{DOCUMENT}. Their feedback
helped improve the final work.
I would also like to thank Brian Kernighan for his invaluable assistance during the
testing and debugging of @command{gawk}, and for his ongoing
help and advice in clarifying numerous points about the language.
We could not have done nearly as good a job on either @command{gawk}
or its documentation without his help.
Brian is in a class by himself as a programmer and technical
author. I have to thank him (yet again) for his ongoing friendship
and for being a role model to me for over 30 years!
Having him as a reviewer is an exciting privilege. It has also
been extremely humbling@enddots{}
@cindex Robbins @subentry Miriam
@cindex Robbins @subentry Jean
@cindex Robbins @subentry Harry
@cindex G-d
I must thank my wonderful wife, Miriam, for her patience through
the many versions of this project, for her proofreading,
and for sharing me with the computer.
I would like to thank my parents for their love, and for the grace with
which they raised and educated me.
Finally, I also must acknowledge my gratitude to G-d, for the many opportunities
He has sent my way, as well as for the gifts He has given me with which to
take advantage of those opportunities.
@ifnotdocbook
@sp 2
@noindent
Arnold Robbins @*
Nof Ayalon @*
Israel @*
March, 2020
@end ifnotdocbook
@ifnotinfo
@part @value{PART1}The @command{awk} Language
@end ifnotinfo
@ifdocbook
Part I describes the @command{awk} language and @command{gawk} program
in detail. It starts with the basics, and continues through all of
the features of @command{awk}. Included also are many, but not all,
of the features of @command{gawk}. This part contains the
following chapters:
@itemize @value{BULLET}
@item
@ref{Getting Started}
@item
@ref{Invoking Gawk}
@item
@ref{Regexp}
@item
@ref{Reading Files}
@item
@ref{Printing}
@item
@ref{Expressions}
@item
@ref{Patterns and Actions}
@item
@ref{Arrays}
@item
@ref{Functions}
@end itemize
@end ifdocbook
@node Getting Started
@chapter Getting Started with @command{awk}
@c @cindex script, definition of
@c @cindex rule, definition of
@c @cindex program, definition of
@c @cindex basic function of @command{awk}
@cindex @command{awk} @subentry function of
The basic function of @command{awk} is to search files for lines (or other
units of text) that contain certain patterns. When a line matches one
of the patterns, @command{awk} performs specified actions on that line.
@command{awk} continues to process input lines in this way until it reaches
the end of the input files.
@cindex @command{awk} @subentry uses for
@cindex programming languages @subentry data-driven vs.@: procedural
@cindex @command{awk} programs
Programs in @command{awk} are different from programs in most other languages,
because @command{awk} programs are @dfn{data driven} (i.e., you describe
the data you want to work with and then what to do when you find it).
Most other languages are @dfn{procedural}; you have to describe, in great
detail, every step the program should take. When working with procedural
languages, it is usually much
harder to clearly describe the data your program will process.
For this reason, @command{awk} programs are often refreshingly easy to
read and write.
@cindex program, definition of
@cindex rule, definition of
When you run @command{awk}, you specify an @command{awk} @dfn{program} that
tells @command{awk} what to do. The program consists of a series of
@dfn{rules} (it may also contain @dfn{function definitions},
an advanced feature that we will ignore for now;
@pxref{User-defined}). Each rule specifies one
pattern to search for and one action to perform
upon finding the pattern.
Syntactically, a rule consists of a @dfn{pattern} followed by an
@dfn{action}. The action is enclosed in braces to separate it from the
pattern. Newlines usually separate rules. Therefore, an @command{awk}
program looks like this:
@example
@var{pattern} @{ @var{action} @}
@var{pattern} @{ @var{action} @}
@dots{}
@end example
@menu
* Running gawk:: How to run @command{gawk} programs; includes
command-line syntax.
* Sample Data Files:: Sample data files for use in the @command{awk}
programs illustrated in this @value{DOCUMENT}.
* Very Simple:: A very simple example.
* Two Rules:: A less simple one-line example using two
rules.
* More Complex:: A more complex example.
* Statements/Lines:: Subdividing or combining statements into
lines.
* Other Features:: Other Features of @command{awk}.
* When:: When to use @command{gawk} and when to use
other things.
* Intro Summary:: Summary of the introduction.
@end menu
@node Running gawk
@section How to Run @command{awk} Programs
@cindex @command{awk} programs @subentry running
There are several ways to run an @command{awk} program. If the program is
short, it is easiest to include it in the command that runs @command{awk},
like this:
@example
awk '@var{program}' @var{input-file1} @var{input-file2} @dots{}
@end example
@cindex command line @subentry formats
When the program is long, it is usually more convenient to put it in a file
and run it with a command like this:
@example
awk -f @var{program-file} @var{input-file1} @var{input-file2} @dots{}
@end example
This @value{SECTION} discusses both mechanisms, along with several
variations of each.
@menu
* One-shot:: Running a short throwaway @command{awk}
program.
* Read Terminal:: Using no input files (input from the keyboard
instead).
* Long:: Putting permanent @command{awk} programs in
files.
* Executable Scripts:: Making self-contained @command{awk} programs.
* Comments:: Adding documentation to @command{gawk}
programs.
* Quoting:: More discussion of shell quoting issues.
@end menu
@node One-shot
@subsection One-Shot Throwaway @command{awk} Programs
Once you are familiar with @command{awk}, you will often type in simple
programs the moment you want to use them. Then you can write the
program as the first argument of the @command{awk} command, like this:
@example
awk '@var{program}' @var{input-file1} @var{input-file2} @dots{}
@end example
@noindent
where @var{program} consists of a series of patterns and
actions, as described earlier.
@cindex single quote (@code{'})
@cindex @code{'} (single quote)
This command format instructs the @dfn{shell}, or command interpreter,
to start @command{awk} and use the @var{program} to process records in the
input file(s). There are single quotes around @var{program} so
the shell won't interpret any @command{awk} characters as special shell
characters. The quotes also cause the shell to treat all of @var{program} as
a single argument for @command{awk}, and allow @var{program} to be more
than one line long.
@cindex shells @subentry scripts
@cindex @command{awk} programs @subentry running @subentry from shell scripts
This format is also useful for running short or medium-sized @command{awk}
programs from shell scripts, because it avoids the need for a separate
file for the @command{awk} program. A self-contained shell script is more
reliable because there are no other files to misplace.
Later in this chapter, in
@ifdocbook
the @value{SECTION}
@end ifdocbook
@ref{Very Simple},
we'll see examples of several short,
self-contained programs.
@node Read Terminal
@subsection Running @command{awk} Without Input Files
@cindex standard input
@cindex input @subentry standard
@cindex input files @subentry running @command{awk} without
You can also run @command{awk} without any input files. If you type the
following command line:
@example
awk '@var{program}'
@end example
@noindent
@command{awk} applies the @var{program} to the @dfn{standard input},
which usually means whatever you type on the keyboard. This continues
until you indicate end-of-file by typing @kbd{Ctrl-d}.
(On non-POSIX operating systems, the end-of-file character may be different.)
@cindex files @subentry input @seeentry{input files}
@cindex input files @subentry running @command{awk} without
@cindex @command{awk} programs @subentry running @subentry without input files
As an example, the following program prints a friendly piece of advice
(from Douglas Adams's @cite{The Hitchhiker's Guide to the Galaxy}),
to keep you from worrying about the complexities of computer
programming:
@example
$ @kbd{awk 'BEGIN @{ print "Don\47t Panic!" @}'}
@print{} Don't Panic!
@end example
@command{awk} executes statements associated with @code{BEGIN} before
reading any input. If there are no other statements in your program,
as is the case here, @command{awk} just stops, instead of trying to read
input it doesn't know how to process.
The @samp{\47} is a magic way (explained later) of getting a single quote into
the program, without having to engage in ugly shell quoting tricks.
@quotation NOTE
If you use Bash as your shell, you should execute the
command @samp{set +H} before running this program interactively, to
disable the C shell-style command history, which treats @samp{!} as a
special character. We recommend putting this command into your personal
startup file.
@end quotation
This next simple @command{awk} program
emulates the @command{cat} utility; it copies whatever you type on the
keyboard to its standard output (why this works is explained shortly):
@example
$ @kbd{awk '@{ print @}'}
@kbd{Now is the time for all good men}
@print{} Now is the time for all good men
@kbd{to come to the aid of their country.}
@print{} to come to the aid of their country.
@kbd{Four score and seven years ago, ...}
@print{} Four score and seven years ago, ...
@kbd{What, me worry?}
@print{} What, me worry?
@kbd{Ctrl-d}
@end example
@node Long
@subsection Running Long Programs
@cindex @command{awk} programs @subentry running
@cindex @command{awk} programs @subentry lengthy
@cindex files @subentry @command{awk} programs in
Sometimes @command{awk} programs are very long. In these cases, it is
more convenient to put the program into a separate file. In order to tell
@command{awk} to use that file for its program, you type:
@example
awk -f @var{source-file} @var{input-file1} @var{input-file2} @dots{}
@end example
@cindex @option{-f} option
@cindex command line @subentry option @option{-f}
The @option{-f} instructs the @command{awk} utility to get the
@command{awk} program from the file @var{source-file} (@pxref{Options}).
Any @value{FN} can be used for @var{source-file}. For example, you
could put the program:
@example
BEGIN @{ print "Don't Panic!" @}
@end example
@noindent
into the file @file{advice}. Then this command:
@example
awk -f advice
@end example
@noindent
does the same thing as this one:
@example
awk 'BEGIN @{ print "Don\47t Panic!" @}'
@end example
@cindex quoting @subentry in @command{gawk} command lines
@noindent
This was explained earlier
(@pxref{Read Terminal}).
Note that you don't usually need single quotes around the @value{FN} that you
specify with @option{-f}, because most @value{FN}s don't contain any of the shell's
special characters. Notice that in @file{advice}, the @command{awk}
program did not have single quotes around it. The quotes are only needed
for programs that are provided on the @command{awk} command line.
(Also, placing the program in a file allows us to use a literal single quote in the program
text, instead of the magic @samp{\47}.)
@cindex single quote (@code{'}) @subentry in @command{gawk} command lines
@cindex @code{'} (single quote) @subentry in @command{gawk} command lines
If you want to clearly identify an @command{awk} program file as such,
you can add the extension @file{.awk} to the @value{FN}. This doesn't
affect the execution of the @command{awk} program but it does make
``housekeeping'' easier.
@node Executable Scripts
@subsection Executable @command{awk} Programs
@cindex @command{awk} programs
@cindex @code{#} (number sign) @subentry @code{#!} (executable scripts)
@cindex Unix @subentry @command{awk} scripts and
@cindex number sign (@code{#}) @subentry @code{#!} (executable scripts)
Once you have learned @command{awk}, you may want to write self-contained
@command{awk} scripts, using the @samp{#!} script mechanism. You can do
this on many systems.@footnote{The @samp{#!} mechanism works on
GNU/Linux systems, BSD-based systems, and commercial Unix systems.}
For example, you could update the file @file{advice} to look like this:
@example
#! /bin/awk -f
BEGIN @{ print "Don't Panic!" @}
@end example
@noindent
After making this file executable (with the @command{chmod} utility),
simply type @samp{advice}
at the shell and the system arranges to run @command{awk} as if you had
typed @samp{awk -f advice}:
@example
$ @kbd{chmod +x advice}
$ @kbd{./advice}
@print{} Don't Panic!
@end example
@noindent
Self-contained @command{awk} scripts are useful when you want to write a
program that users can invoke without their having to know that the program is
written in @command{awk}.
@cindex sidebar @subentry Understanding @samp{#!}
@ifdocbook
@docbook
<sidebar><title>Understanding @samp{#!}</title>
@end docbook
@cindex portability @subentry @code{#!} (executable scripts)
@command{awk} is an @dfn{interpreted} language. This means that the
@command{awk} utility reads your program and then processes your data
according to the instructions in your program. (This is different
from a @dfn{compiled} language such as C, where your program is first
compiled into machine code that is executed directly by your system's
processor.) The @command{awk} utility is thus termed an @dfn{interpreter}.
Many modern languages are interpreted.
The line beginning with @samp{#!} lists the full @value{FN} of an
interpreter to run and a single optional initial command-line argument
to pass to that interpreter. The operating system then runs the
interpreter with the given argument and the full argument list of the
executed program. The first argument in the list is the full @value{FN}
of the @command{awk} program. The rest of the argument list contains
either options to @command{awk}, or @value{DF}s, or both. (Note that on
many systems @command{awk} is found in @file{/usr/bin} instead of
in @file{/bin}.)
Some systems limit the length of the interpreter name to 32 characters.
Often, this can be dealt with by using a symbolic link.
You should not put more than one argument on the @samp{#!}
line after the path to @command{awk}. It does not work. The operating system
treats the rest of the line as a single argument and passes it to @command{awk}.
Doing this leads to confusing behavior---most likely a usage diagnostic
of some sort from @command{awk}.
@cindex @code{ARGC}/@code{ARGV} variables @subentry portability and
@cindex portability @subentry @code{ARGV} variable
@cindex dark corner @subentry @code{ARGV} variable, value of
Finally, the value of @code{ARGV[0]}
(@pxref{Built-in Variables})
varies depending upon your operating system.
Some systems put @samp{awk} there, some put the full pathname
of @command{awk} (such as @file{/bin/awk}), and some put the name
of your script (@samp{advice}). @value{DARKCORNER}
Don't rely on the value of @code{ARGV[0]}
to provide your script name.
@docbook
</sidebar>
@end docbook
@end ifdocbook
@ifnotdocbook
@cartouche
@center @b{Understanding @samp{#!}}
@cindex portability @subentry @code{#!} (executable scripts)
@command{awk} is an @dfn{interpreted} language. This means that the
@command{awk} utility reads your program and then processes your data
according to the instructions in your program. (This is different
from a @dfn{compiled} language such as C, where your program is first
compiled into machine code that is executed directly by your system's
processor.) The @command{awk} utility is thus termed an @dfn{interpreter}.
Many modern languages are interpreted.
The line beginning with @samp{#!} lists the full @value{FN} of an
interpreter to run and a single optional initial command-line argument
to pass to that interpreter. The operating system then runs the
interpreter with the given argument and the full argument list of the
executed program. The first argument in the list is the full @value{FN}
of the @command{awk} program. The rest of the argument list contains
either options to @command{awk}, or @value{DF}s, or both. (Note that on
many systems @command{awk} is found in @file{/usr/bin} instead of
in @file{/bin}.)
Some systems limit the length of the interpreter name to 32 characters.
Often, this can be dealt with by using a symbolic link.
You should not put more than one argument on the @samp{#!}
line after the path to @command{awk}. It does not work. The operating system
treats the rest of the line as a single argument and passes it to @command{awk}.
Doing this leads to confusing behavior---most likely a usage diagnostic
of some sort from @command{awk}.
@cindex @code{ARGC}/@code{ARGV} variables @subentry portability and
@cindex portability @subentry @code{ARGV} variable
@cindex dark corner @subentry @code{ARGV} variable, value of
Finally, the value of @code{ARGV[0]}
(@pxref{Built-in Variables})
varies depending upon your operating system.
Some systems put @samp{awk} there, some put the full pathname
of @command{awk} (such as @file{/bin/awk}), and some put the name
of your script (@samp{advice}). @value{DARKCORNER}
Don't rely on the value of @code{ARGV[0]}
to provide your script name.
@end cartouche
@end ifnotdocbook
@node Comments
@subsection Comments in @command{awk} Programs
@cindex @code{#} (number sign) @subentry commenting
@cindex number sign (@code{#}) @subentry commenting
@cindex commenting
@cindex @command{awk} programs @subentry documenting
A @dfn{comment} is some text that is included in a program for the sake
of human readers; it is not really an executable part of the program. Comments
can explain what the program does and how it works. Nearly all
programming languages have provisions for comments, as programs are
typically hard to understand without them.
In the @command{awk} language, a comment starts with the number sign
character (@samp{#}) and continues to the end of the line.
The @samp{#} does not have to be the first character on the line. The
@command{awk} language ignores the rest of a line following a number sign.
For example, we could have put the following into @file{advice}:
@example
# This program prints a nice, friendly message. It helps
# keep novice users from being afraid of the computer.
BEGIN @{ print "Don't Panic!" @}
@end example
You can put comment lines into keyboard-composed throwaway @command{awk}
programs, but this usually isn't very useful; the purpose of a
comment is to help you or another person understand the program
when reading it at a later time.
@cindex quoting @subentry for small awk programs
@cindex single quote (@code{'}) @subentry vs.@: apostrophe
@cindex @code{'} (single quote) @subentry vs.@: apostrophe
@quotation CAUTION
As mentioned in
@ref{One-shot},
you can enclose short to medium-sized programs in single quotes,
in order to keep
your shell scripts self-contained. When doing so, @emph{don't} put
an apostrophe (i.e., a single quote) into a comment (or anywhere else
in your program). The shell interprets the quote as the closing
quote for the entire program. As a result, usually the shell
prints a message about mismatched quotes, and if @command{awk} actually
runs, it will probably print strange messages about syntax errors.
For example, look at the following:
@example
$ @kbd{awk 'BEGIN @{ print "hello" @} # let's be cute'}
>
@end example
The shell sees that the first two quotes match, and that
a new quoted object begins at the end of the command line.
It therefore prompts with the secondary prompt, waiting for more input.
With Unix @command{awk}, closing the quoted string produces this result:
@example
$ @kbd{awk '@{ print "hello" @} # let's be cute'}
> @kbd{'}
@error{} awk: can't open file be
@error{} source line number 1
@end example
@cindex @code{\} (backslash)
@cindex backslash (@code{\})
Putting a backslash before the single quote in @samp{let's} wouldn't help,
because backslashes are not special inside single quotes.
The next @value{SUBSECTION} describes the shell's quoting rules.
@end quotation
@node Quoting
@subsection Shell Quoting Issues
@cindex shell quoting, rules for
@menu
* DOS Quoting:: Quoting in Windows Batch Files.
@end menu
For short to medium-length @command{awk} programs, it is most convenient
to enter the program on the @command{awk} command line.
This is best done by enclosing the entire program in single quotes.
This is true whether you are entering the program interactively at
the shell prompt, or writing it as part of a larger shell script:
@example
awk '@var{program text}' @var{input-file1} @var{input-file2} @dots{}
@end example
@cindex shells @subentry quoting @subentry rules for
@cindex Bourne shell, quoting rules for
Once you are working with the shell, it is helpful to have a basic
knowledge of shell quoting rules. The following rules apply only to
POSIX-compliant, Bourne-style shells (such as Bash, the GNU Bourne-Again
Shell). If you use the C shell, you're on your own.
Before diving into the rules, we introduce a concept that appears
throughout this @value{DOCUMENT}, which is that of the @dfn{null},
or empty, string.
The null string is character data that has no value.
In other words, it is empty. It is written in @command{awk} programs
like this: @code{""}. In the shell, it can be written using single
or double quotes: @code{""} or @code{''}. Although the null string has
no characters in it, it does exist. For example, consider this command:
@example
$ @kbd{echo ""}
@end example
@noindent
Here, the @command{echo} utility receives a single argument, even
though that argument has no characters in it. In the rest of this
@value{DOCUMENT}, we use the terms @dfn{null string} and @dfn{empty string}
interchangeably. Now, on to the quoting rules:
@itemize @value{BULLET}
@item
Quoted items can be concatenated with nonquoted items as well as with other
quoted items. The shell turns everything into one argument for
the command.
@item
Preceding any single character with a backslash (@samp{\}) quotes
that character. The shell removes the backslash and passes the quoted
character on to the command.
@item
@cindex @code{\} (backslash) @subentry in shell commands
@cindex backslash (@code{\}) @subentry in shell commands
@cindex single quote (@code{'}) @subentry in shell commands
@cindex @code{'} (single quote) @subentry in shell commands
Single quotes protect everything between the opening and closing quotes.
The shell does no interpretation of the quoted text, passing it on verbatim
to the command.
It is @emph{impossible} to embed a single quote inside single-quoted text.
Refer back to
@ref{Comments}
for an example of what happens if you try.
@item
@cindex double quote (@code{"}) @subentry in shell commands
@cindex @code{"} (double quote) @subentry in shell commands
Double quotes protect most things between the opening and closing quotes.
The shell does at least variable and command substitution on the quoted text.
Different shells may do additional kinds of processing on double-quoted text.
Because certain characters within double-quoted text are processed by the shell,
they must be @dfn{escaped} within the text. Of note are the characters
@samp{$}, @samp{`}, @samp{\}, and @samp{"}, all of which must be preceded by
a backslash within double-quoted text if they are to be passed on literally
to the program. (The leading backslash is stripped first.)
Thus, the example seen
@ifnotinfo
previously
@end ifnotinfo
in @ref{Read Terminal}:
@example
awk 'BEGIN @{ print "Don\47t Panic!" @}'
@end example
@noindent
could instead be written this way:
@example
$ @kbd{awk "BEGIN @{ print \"Don't Panic!\" @}"}
@print{} Don't Panic!
@end example
@cindex single quote (@code{'}) @subentry with double quotes
@cindex @code{'} (single quote) @subentry with double quotes
Note that the single quote is not special within double quotes.
@item
Null strings are removed when they occur as part of a non-null
command-line argument, while explicit null objects are kept.
For example, to specify that the field separator @code{FS} should
be set to the null string, use:
@example
awk -F "" '@var{program}' @var{files} # correct
@end example
@noindent
@cindex null strings @subentry in @command{gawk} arguments, quoting and
Don't use this:
@example
awk -F"" '@var{program}' @var{files} # wrong!
@end example
@noindent
In the second case, @command{awk} attempts to use the text of the program
as the value of @code{FS}, and the first @value{FN} as the text of the program!
This results in syntax errors at best, and confusing behavior at worst.
@end itemize
@cindex quoting @subentry in @command{gawk} command lines @subentry tricks for
Mixing single and double quotes is difficult. You have to resort
to shell quoting tricks, like this:
@example
$ @kbd{awk 'BEGIN @{ print "Here is a single quote <'"'"'>" @}'}
@print{} Here is a single quote <'>
@end example
@noindent
This program consists of three concatenated quoted strings. The first and the
third are single-quoted, and the second is double-quoted.
This can be ``simplified'' to:
@example
$ @kbd{awk 'BEGIN @{ print "Here is a single quote <'\''>" @}'}
@print{} Here is a single quote <'>
@end example
@noindent
Judge for yourself which of these two is the more readable.
Another option is to use double quotes, escaping the embedded, @command{awk}-level
double quotes:
@example
$ @kbd{awk "BEGIN @{ print \"Here is a single quote <'>\" @}"}
@print{} Here is a single quote <'>
@end example
@noindent
This option is also painful, because double quotes, backslashes, and dollar signs
are very common in more advanced @command{awk} programs.
A third option is to use the octal escape sequence equivalents
(@pxref{Escape Sequences})
for the
single- and double-quote characters, like so:
@example
@group
$ @kbd{awk 'BEGIN @{ print "Here is a single quote <\47>" @}'}
@print{} Here is a single quote <'>
$ @kbd{awk 'BEGIN @{ print "Here is a double quote <\42>" @}'}
@print{} Here is a double quote <">
@end group
@end example
@noindent
This works nicely, but you should comment clearly what the
escape sequences mean.
A fourth option is to use command-line variable assignment, like this:
@example
$ @kbd{awk -v sq="'" 'BEGIN @{ print "Here is a single quote <" sq ">" @}'}
@print{} Here is a single quote <'>
@end example
(Here, the two string constants and the value of @code{sq} are concatenated
into a single string that is printed by @code{print}.)
If you really need both single and double quotes in your @command{awk}
program, it is probably best to move it into a separate file, where
the shell won't be part of the picture and you can say what you mean.
@node DOS Quoting
@subsubsection Quoting in MS-Windows Batch Files
@ignore
Date: Wed, 21 May 2008 09:58:43 +0200 (CEST)
From: jeroen.brink@inter.NL.net
Subject: (g)awk "contribution"
To: arnold@skeeve.com
Message-id: <42220.193.172.132.34.1211356723.squirrel@webmail.internl.net>
Hello Arnold,
maybe you can help me out. Found your email on the GNU/awk online manual
pages.
I've searched hard to figure out how, on Windows, to print double quotes.
Couldn't find it in the Quotes area, nor on google or elsewhere. Finally i
figured out how to do this myself.
How to print all lines in a file surrounded by double quotes (on Windows):
gawk "{ print \"\042\" $0 \"\042\" }" <file>
Maybe this is a helpfull tip for other (Windows) gawk users. However, i
don't have a clue as to where to "publish" this tip! Do you?
Kind regards,
Jeroen Brink
@end ignore
Although this @value{DOCUMENT} generally only worries about POSIX systems and the
POSIX shell, the following issue arises often enough for many users that
it is worth addressing.
@cindex Brink, Jeroen
The ``shells'' on Microsoft Windows systems use the double-quote
character for quoting, and make it difficult or impossible to include an
escaped double-quote character in a command-line script. The following
example, courtesy of Jeroen Brink, shows how to escape the double quotes
from this one liner script that prints all lines in a file surrounded by
double quotes:
@example
@{ print "\"" $0 "\"" @}
@end example
@noindent
In an MS-Windows command-line the one-liner script above may be passed as
follows:
@example
gawk "@{ print \"\042\" $0 \"\042\" @}" @var{file}
@end example
In this example the @samp{\042} is the octal code for a double-quote;
@command{gawk} converts it into a real double-quote for output by
the @code{print} statement.
In MS-Windows escaping double-quotes is a little tricky because you use
backslashes to escape double-quotes, but backslashes themselves are not
escaped in the usual way; indeed they are either duplicated or not,
depending upon whether there is a subsequent double-quote. The MS-Windows
rule for double-quoting a string is the following:
@enumerate
@item
For each double quote in the original string, let @var{N} be the number
of backslash(es) before it, @var{N} might be zero. Replace these @var{N}
backslash(es) by @math{2@value{TIMES}@var{N}+1} backslash(es)
@item
Let @var{N} be the number of backslash(es) tailing the original string,
@var{N} might be zero. Replace these @var{N} backslash(es) by
@math{2@value{TIMES}@var{N}} backslash(es)
@item
Surround the resulting string by double-quotes.
@end enumerate
So to double-quote the one-liner script @samp{@{ print "\"" $0 "\"" @}}
from the previous example you would do it this way:
@example
gawk "@{ print \"\\\"\" $0 \"\\\"\" @}" @var{file}
@end example
@noindent
However, the use of @samp{\042} instead of @samp{\\\"} is also possible
and easier to read, because backslashes that are not followed by a
double-quote don't need duplication.
@node Sample Data Files
@section @value{DDF}s for the Examples
@cindex input files @subentry examples
@cindex @code{mail-list} file
Many of the examples in this @value{DOCUMENT} take their input from two sample
@value{DF}s. The first, @file{mail-list}, represents a list of peoples' names
together with their email addresses and information about those people.
The second @value{DF}, called @file{inventory-shipped}, contains
information about monthly shipments. In both files,
each line is considered to be one @dfn{record}.
In @file{mail-list}, each record contains the name of a person,
his/her phone number, his/her email address, and a code for his/her relationship
with the author of the list.
The columns are aligned using spaces.
An @samp{A} in the last column
means that the person is an acquaintance. An @samp{F} in the last
column means that the person is a friend.
An @samp{R} means that the person is a relative:
@example
@c system if test ! -d eg ; then mkdir eg ; fi
@c system if test ! -d eg/lib ; then mkdir eg/lib ; fi
@c system if test ! -d eg/data ; then mkdir eg/data ; fi
@c system if test ! -d eg/prog ; then mkdir eg/prog ; fi
@c system if test ! -d eg/misc ; then mkdir eg/misc ; fi
@c file eg/data/mail-list
Amelia 555-5553 amelia.zodiacusque@@gmail.com F
Anthony 555-3412 anthony.asserturo@@hotmail.com A
Becky 555-7685 becky.algebrarum@@gmail.com A
Bill 555-1675 bill.drowning@@hotmail.com A
Broderick 555-0542 broderick.aliquotiens@@yahoo.com R
Camilla 555-2912 camilla.infusarum@@skynet.be R
Fabius 555-1234 fabius.undevicesimus@@ucb.edu F
Julie 555-6699 julie.perscrutabor@@skeeve.com F
Martin 555-6480 martin.codicibus@@hotmail.com A
Samuel 555-3430 samuel.lanceolis@@shu.edu A
Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R
@c endfile
@end example
@cindex @code{inventory-shipped} file
The @value{DF} @file{inventory-shipped} represents
information about shipments during the year.
Each record contains the month, the number
of green crates shipped, the number of red boxes shipped, the number of
orange bags shipped, and the number of blue packages shipped,
respectively. There are 16 entries, covering the 12 months of last year
and the first four months of the current year.
An empty line separates the data for the two years:
@example
@c file eg/data/inventory-shipped
Jan 13 25 15 115
Feb 15 32 24 226
Mar 15 24 34 228
Apr 31 52 63 420
May 16 34 29 208
Jun 31 42 75 492
Jul 24 34 67 436
Aug 15 34 47 316
Sep 13 55 37 277
Oct 29 54 68 525
Nov 20 87 82 577
Dec 17 35 61 401
Jan 21 36 64 620
Feb 26 58 80 652
Mar 24 75 70 495
Apr 21 70 74 514
@c endfile
@end example
The sample files are included in the @command{gawk} distribution,
in the directory @file{awklib/eg/data}.
@node Very Simple
@section Some Simple Examples
The following command runs a simple @command{awk} program that searches the
input file @file{mail-list} for the character string @samp{li} (a
grouping of characters is usually called a @dfn{string};
the term @dfn{string} is based on similar usage in English, such
as ``a string of pearls'' or ``a string of cars in a train''):
@example
awk '/li/ @{ print $0 @}' mail-list
@end example
@noindent
When lines containing @samp{li} are found, they are printed because
@w{@samp{print $0}} means print the current line. (Just @samp{print} by
itself means the same thing, so we could have written that
instead.)
You will notice that slashes (@samp{/}) surround the string @samp{li}
in the @command{awk} program. The slashes indicate that @samp{li}
is the pattern to search for. This type of pattern is called a
@dfn{regular expression}, which is covered in more detail later
(@pxref{Regexp}).
The pattern is allowed to match parts of words.
There are
single quotes around the @command{awk} program so that the shell won't
interpret any of it as special shell characters.
Here is what this program prints:
@example
$ @kbd{awk '/li/ @{ print $0 @}' mail-list}
@print{} Amelia 555-5553 amelia.zodiacusque@@gmail.com F
@print{} Broderick 555-0542 broderick.aliquotiens@@yahoo.com R
@print{} Julie 555-6699 julie.perscrutabor@@skeeve.com F
@print{} Samuel 555-3430 samuel.lanceolis@@shu.edu A
@end example
@cindex actions @subentry default
@cindex patterns @subentry default
In an @command{awk} rule, either the pattern or the action can be omitted,
but not both. If the pattern is omitted, then the action is performed
for @emph{every} input line. If the action is omitted, the default
action is to print all lines that match the pattern.
@cindex actions @subentry empty
Thus, we could leave out the action (the @code{print} statement and the
braces) in the previous example and the result would be the same:
@command{awk} prints all lines matching the pattern @samp{li}. By comparison,
omitting the @code{print} statement but retaining the braces makes an
empty action that does nothing (i.e., no lines are printed).
@cindex @command{awk} programs @subentry one-line examples
Many practical @command{awk} programs are just a line or two long. Following is a
collection of useful, short programs to get you started. Some of these
programs contain constructs that haven't been covered yet. (The description
of the program will give you a good idea of what is going on, but you'll
need to read the rest of the @value{DOCUMENT} to become an @command{awk} expert!)
Most of the examples use a @value{DF} named @file{data}. This is just a
placeholder; if you use these programs yourself, substitute
your own @value{FN}s for @file{data}.
For future reference, note that there is often more than
one way to do things in @command{awk}. At some point, you may want
to look back at these examples and see if
you can come up with different ways to do the same things shown here:
@itemize @value{BULLET}
@item
Print every line that is longer than 80 characters:
@example
awk 'length($0) > 80' data
@end example
The sole rule has a relational expression as its pattern and has no
action---so it uses the default action, printing the record.
@item
Print the length of the longest input line:
@example
@group
awk '@{ if (length($0) > max) max = length($0) @}
END @{ print max @}' data
@end group
@end example
The code associated with @code{END} executes after all
input has been read; it's the other side of the coin to @code{BEGIN}.
@cindex @command{expand} utility
@item
Print the length of the longest line in @file{data}:
@example
expand data | awk '@{ if (x < length($0)) x = length($0) @}
END @{ print "maximum line length is " x @}'
@end example
This example differs slightly from the previous one:
the input is processed by the @command{expand} utility to change TABs
into spaces, so the widths compared are actually the right-margin columns,
as opposed to the number of input characters on each line.
@item
Print every line that has at least one field:
@example
awk 'NF > 0' data
@end example
This is an easy way to delete blank lines from a file (or rather, to
create a new file similar to the old file but from which the blank lines
have been removed).
@item
Print seven random numbers from 0 to 100, inclusive:
@example
awk 'BEGIN @{ for (i = 1; i <= 7; i++)
print int(101 * rand()) @}'
@end example
@item
Print the total number of bytes used by @var{files}:
@example
ls -l @var{files} | awk '@{ x += $5 @}
END @{ print "total bytes: " x @}'
@end example
@item
Print the total number of kilobytes used by @var{files}:
@c Don't use \ continuation, not discussed yet
@c Remember that awk does floating point division,
@c no need for (x+1023) / 1024
@example
ls -l @var{files} | awk '@{ x += $5 @}
END @{ print "total K-bytes:", x / 1024 @}'
@end example
@item
Print a sorted list of the login names of all users:
@example
awk -F: '@{ print $1 @}' /etc/passwd | sort
@end example
@item
Count the lines in a file:
@example
awk 'END @{ print NR @}' data
@end example
@item
Print the even-numbered lines in the @value{DF}:
@example
awk 'NR % 2 == 0' data
@end example
If you used the expression @samp{NR % 2 == 1} instead,
the program would print the odd-numbered lines.
@end itemize
@node Two Rules
@section An Example with Two Rules
@cindex @command{awk} programs
The @command{awk} utility reads the input files one line at a
time. For each line, @command{awk} tries the patterns of each rule.
If several patterns match, then several actions execute in the order in
which they appear in the @command{awk} program. If no patterns match, then
no actions run.
After processing all the rules that match the line (and perhaps there are none),
@command{awk} reads the next line. (However,
@pxref{Next Statement}
@ifdocbook
and @ref{Nextfile Statement}.)
@end ifdocbook
@ifnotdocbook
and also @pxref{Nextfile Statement}.)
@end ifnotdocbook
This continues until the program reaches the end of the file.
For example, the following @command{awk} program contains two rules:
@example
/12/ @{ print $0 @}
/21/ @{ print $0 @}
@end example
@noindent
The first rule has the string @samp{12} as the
pattern and @samp{print $0} as the action. The second rule has the
string @samp{21} as the pattern and also has @samp{print $0} as the
action. Each rule's action is enclosed in its own pair of braces.
This program prints every line that contains the string
@samp{12} @emph{or} the string @samp{21}. If a line contains both
strings, it is printed twice, once by each rule.
This is what happens if we run this program on our two sample @value{DF}s,
@file{mail-list} and @file{inventory-shipped}:
@example
$ @kbd{awk '/12/ @{ print $0 @}}
> @kbd{/21/ @{ print $0 @}' mail-list inventory-shipped}
@print{} Anthony 555-3412 anthony.asserturo@@hotmail.com A
@print{} Camilla 555-2912 camilla.infusarum@@skynet.be R
@print{} Fabius 555-1234 fabius.undevicesimus@@ucb.edu F
@print{} Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R
@print{} Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R
@print{} Jan 21 36 64 620
@print{} Apr 21 70 74 514
@end example
@noindent
Note how the line beginning with @samp{Jean-Paul}
in @file{mail-list} was printed twice, once for each rule.
@node More Complex
@section A More Complex Example
Now that we've mastered some simple tasks, let's look at
what typical @command{awk}
programs do. This example shows how @command{awk} can be used to
summarize, select, and rearrange the output of another utility. It uses
features that haven't been covered yet, so don't worry if you don't
understand all the details:
@example
ls -l | awk '$6 == "Nov" @{ sum += $5 @}
END @{ print sum @}'
@end example
@cindex @command{ls} utility
This command prints the total number of bytes in all the files in the
current directory that were last modified in November (of any year).
The @w{@samp{ls -l}} part of this example is a system command that gives
you a listing of the files in a directory, including each file's size and the date
the file was last modified. Its output looks like this:
@example
-rw-r--r-- 1 arnold user 1933 Nov 7 13:05 Makefile
-rw-r--r-- 1 arnold user 10809 Nov 7 13:03 awk.h
-rw-r--r-- 1 arnold user 983 Apr 13 12:14 awk.tab.h
-rw-r--r-- 1 arnold user 31869 Jun 15 12:20 awkgram.y
-rw-r--r-- 1 arnold user 22414 Nov 7 13:03 awk1.c
-rw-r--r-- 1 arnold user 37455 Nov 7 13:03 awk2.c
-rw-r--r-- 1 arnold user 27511 Dec 9 13:07 awk3.c
-rw-r--r-- 1 arnold user 7989 Nov 7 13:03 awk4.c
@end example
@noindent
@cindex line continuations @subentry with C shell
The first field contains read-write permissions, the second field contains
the number of links to the file, and the third field identifies the file's owner.
The fourth field identifies the file's group.
The fifth field contains the file's size in bytes. The
sixth, seventh, and eighth fields contain the month, day, and time,
respectively, that the file was last modified. Finally, the ninth field
contains the @value{FN}.
@c @cindex automatic initialization
@cindex initialization, automatic
The @samp{$6 == "Nov"} in our @command{awk} program is an expression that
tests whether the sixth field of the output from @w{@samp{ls -l}}
matches the string @samp{Nov}. Each time a line has the string
@samp{Nov} for its sixth field, @command{awk} performs the action
@samp{sum += $5}. This adds the fifth field (the file's size) to the variable
@code{sum}. As a result, when @command{awk} has finished reading all the
input lines, @code{sum} is the total of the sizes of the files whose
lines matched the pattern. (This works because @command{awk} variables
are automatically initialized to zero.)
After the last line of output from @command{ls} has been processed, the
@code{END} rule executes and prints the value of @code{sum}.
In this example, the value of @code{sum} is 80600.
These more advanced @command{awk} techniques are covered in later
@value{SECTION}s
(@pxref{Action Overview}). Before you can move on to more
advanced @command{awk} programming, you have to know how @command{awk} interprets
your input and displays your output. By manipulating fields and using
@code{print} statements, you can produce some very useful and
impressive-looking reports.
@node Statements/Lines
@section @command{awk} Statements Versus Lines
@cindex line breaks
@cindex newlines
Most often, each line in an @command{awk} program is a separate statement or
separate rule, like this:
@example
awk '/12/ @{ print $0 @}
/21/ @{ print $0 @}' mail-list inventory-shipped
@end example
@cindex @command{gawk} @subentry newlines in
However, @command{gawk} ignores newlines after any of the following
symbols and keywords:
@example
, @{ ? : || && do else
@end example
@noindent
A newline at any other point is considered the end of the
statement.@footnote{The @samp{?} and @samp{:} referred to here is the
three-operand conditional expression described in
@ref{Conditional Exp}.
Splitting lines after @samp{?} and @samp{:} is a minor @command{gawk}
extension; if @option{--posix} is specified
(@pxref{Options}), then this extension is disabled.}
@cindex @code{\} (backslash) @subentry continuing lines and
@cindex backslash (@code{\}) @subentry continuing lines and
If you would like to split a single statement into two lines at a point
where a newline would terminate it, you can @dfn{continue} it by ending the
first line with a backslash character (@samp{\}). The backslash must be
the final character on the line in order to be recognized as a continuation
character. A backslash followed by a newline is allowed anywhere in the statement, even
in the middle of a string or regular expression. For example:
@example
awk '/This regular expression is too long, so continue it\
on the next line/ @{ print $1 @}'
@end example
@noindent
@cindex portability @subentry backslash continuation and
We have generally not used backslash continuation in our sample programs.
@command{gawk} places no limit on the
length of a line, so backslash continuation is never strictly necessary;
it just makes programs more readable. For this same reason, as well as
for clarity, we have kept most statements short in the programs
presented throughout the @value{DOCUMENT}.
Backslash continuation is
most useful when your @command{awk} program is in a separate source file
instead of entered from the command line. You should also note that
many @command{awk} implementations are more particular about where you
may use backslash continuation. For example, they may not allow you to
split a string constant using backslash continuation. Thus, for maximum
portability of your @command{awk} programs, it is best not to split your
lines in the middle of a regular expression or a string.
@c 10/2000: gawk, mawk, and current bell labs awk allow it,
@c solaris 2.7 nawk does not. Solaris /usr/xpg4/bin/awk does though! sigh.
@cindex @command{csh} utility
@cindex backslash (@code{\}) @subentry continuing lines and @subentry in @command{csh}
@cindex @code{\} (backslash) @subentry continuing lines and @subentry in @command{csh}
@quotation CAUTION
@emph{Backslash continuation does not work as described
with the C shell.} It works for @command{awk} programs in files and
for one-shot programs, @emph{provided} you are using a POSIX-compliant
shell, such as the Unix Bourne shell or Bash. But the C shell behaves
differently! There you must use two backslashes in a row, followed by
a newline. Note also that when using the C shell, @emph{every} newline
in your @command{awk} program must be escaped with a backslash. To illustrate:
@example
% @kbd{awk 'BEGIN @{ \}
? @kbd{ print \\}
? @kbd{ "hello, world" \}
? @kbd{@}'}
@print{} hello, world
@end example
@noindent
Here, the @samp{%} and @samp{?} are the C shell's primary and secondary
prompts, analogous to the standard shell's @samp{$} and @samp{>}.
Compare the previous example to how it is done with a POSIX-compliant shell:
@example
$ @kbd{awk 'BEGIN @{}
> @kbd{print \}
> @kbd{"hello, world"}
> @kbd{@}'}
@print{} hello, world
@end example
@end quotation
@command{awk} is a line-oriented language. Each rule's action has to
begin on the same line as the pattern. To have the pattern and action
on separate lines, you @emph{must} use backslash continuation; there
is no other option.
@cindex backslash (@code{\}) @subentry continuing lines and @subentry comments and
@cindex @code{\} (backslash) @subentry continuing lines and @subentry comments and
@cindex commenting @subentry backslash continuation and
Another thing to keep in mind is that backslash continuation and
comments do not mix. As soon as @command{awk} sees the @samp{#} that
starts a comment, it ignores @emph{everything} on the rest of the
line. For example:
@example
@group
$ @kbd{gawk 'BEGIN @{ print "dont panic" # a friendly \}
> @kbd{ BEGIN rule}
> @kbd{@}'}
@error{} gawk: cmd. line:2: BEGIN rule
@error{} gawk: cmd. line:2: ^ syntax error
@end group
@end example
@noindent
In this case, it looks like the backslash would continue the comment onto the
next line. However, the backslash-newline combination is never even
noticed because it is ``hidden'' inside the comment. Thus, the
@code{BEGIN} is noted as a syntax error.
@cindex statements @subentry multiple
@cindex @code{;} (semicolon) @subentry separating statements in actions
@cindex semicolon (@code{;}) @subentry separating statements in actions
@cindex @code{;} (semicolon) @subentry separating rules
@cindex semicolon (@code{;}) @subentry separating rules
When @command{awk} statements within one rule are short, you might want to put
more than one of them on a line. This is accomplished by separating the statements
with a semicolon (@samp{;}).
This also applies to the rules themselves.
Thus, the program shown at the start of this @value{SECTION}
could also be written this way:
@example
/12/ @{ print $0 @} ; /21/ @{ print $0 @}
@end example
@quotation NOTE
The requirement that states that rules on the same line must be
separated with a semicolon was not in the original @command{awk}
language; it was added for consistency with the treatment of statements
within an action.
@end quotation
@node Other Features
@section Other Features of @command{awk}
@cindex variables
The @command{awk} language provides a number of predefined, or
@dfn{built-in}, variables that your programs can use to get information
from @command{awk}. There are other variables your program can set
as well to control how @command{awk} processes your data.
In addition, @command{awk} provides a number of built-in functions for doing
common computational and string-related operations.
@command{gawk} provides built-in functions for working with timestamps,
performing bit manipulation, for runtime string translation (internationalization),
determining the type of a variable,
and array sorting.
As we develop our presentation of the @command{awk} language, we will introduce
most of the variables and many of the functions. They are described
systematically in @ref{Built-in Variables} and in
@ref{Built-in}.
@node When
@section When to Use @command{awk}
@cindex @command{awk} @subentry uses for
Now that you've seen some of what @command{awk} can do,
you might wonder how @command{awk} could be useful for you. By using
utility programs, advanced patterns, field separators, arithmetic
statements, and other selection criteria, you can produce much more
complex output. The @command{awk} language is very useful for producing
reports from large amounts of raw data, such as summarizing information
from the output of other utility programs like @command{ls}.
(@xref{More Complex}.)
Programs written with @command{awk} are usually much smaller than they would
be in other languages. This makes @command{awk} programs easy to compose and
use. Often, @command{awk} programs can be quickly composed at your keyboard,
used once, and thrown away. Because @command{awk} programs are interpreted, you
can avoid the (usually lengthy) compilation part of the typical
edit-compile-test-debug cycle of software development.
@cindex Brian Kernighan's @command{awk}
Complex programs have been written in @command{awk}, including a complete
retargetable assembler for
@ifclear FOR_PRINT
eight-bit microprocessors (@pxref{Glossary}, for more information),
@end ifclear
@ifset FOR_PRINT
eight-bit microprocessors,
@end ifset
and a microcode assembler for a special-purpose Prolog
computer.
The original @command{awk}'s capabilities were strained by tasks
of such complexity, but modern versions are more capable.
@cindex @command{awk} programs @subentry complex
If you find yourself writing @command{awk} scripts of more than, say,
a few hundred lines, you might consider using a different programming
language. The shell is good at string and pattern matching; in addition,
it allows powerful use of the system utilities. Python offers a nice
balance between high-level ease of programming and access to system
facilities.@footnote{Other popular scripting languages include Ruby
and Perl.}
@node Intro Summary
@section Summary
@c FIXME: Review this chapter for summary of builtin functions called.
@itemize @value{BULLET}
@item
Programs in @command{awk} consist of @var{pattern}--@var{action} pairs.
@item
An @var{action} without a @var{pattern} always runs. The default
@var{action} for a pattern without one is @samp{@{ print $0 @}}.
@item
Use either
@samp{awk '@var{program}' @var{files}}
or
@samp{awk -f @var{program-file} @var{files}}
to run @command{awk}.
@item
You may use the special @samp{#!} header line to create @command{awk}
programs that are directly executable.
@item
Comments in @command{awk} programs start with @samp{#} and continue to
the end of the same line.
@item
Be aware of quoting issues when writing @command{awk} programs as
part of a larger shell script (or MS-Windows batch file).
@item
You may use backslash continuation to continue a source line.
Lines are automatically continued after
a comma, open brace, question mark, colon,
@samp{||}, @samp{&&}, @code{do}, and @code{else}.
@end itemize
@node Invoking Gawk
@chapter Running @command{awk} and @command{gawk}
This @value{CHAPTER} covers how to run @command{awk}, both POSIX-standard
and @command{gawk}-specific command-line options, and what
@command{awk} and
@command{gawk} do with nonoption arguments.
It then proceeds to cover how @command{gawk} searches for source files,
reading standard input along with other files, @command{gawk}'s
environment variables, @command{gawk}'s exit status, using include files,
and obsolete and undocumented options and/or features.
Many of the options and features described here are discussed in
more detail later in the @value{DOCUMENT}; feel free to skip over
things in this @value{CHAPTER} that don't interest you right now.
@menu
* Command Line:: How to run @command{awk}.
* Options:: Command-line options and their meanings.
* Other Arguments:: Input file names and variable assignments.
* Naming Standard Input:: How to specify standard input with other
files.
* Environment Variables:: The environment variables @command{gawk} uses.
* Exit Status:: @command{gawk}'s exit status.
* Include Files:: Including other files into your program.
* Loading Shared Libraries:: Loading shared libraries into your program.
* Obsolete:: Obsolete Options and/or features.
* Undocumented:: Undocumented Options and Features.
* Invoking Summary:: Invocation summary.
@end menu
@node Command Line
@section Invoking @command{awk}
@cindex command line @subentry invoking @command{awk} from
@cindex @command{awk} @subentry invoking
@cindex arguments @subentry command-line @subentry invoking @command{awk}
@cindex options @subentry command-line @subentry invoking @command{awk}
There are two ways to run @command{awk}---with an explicit program or with
one or more program files. Here are templates for both of them; items
enclosed in [@dots{}] in these templates are optional:
@display
@command{awk} [@var{options}] @option{-f} @var{progfile} [@option{--}] @var{file} @dots{}
@command{awk} [@var{options}] [@option{--}] @code{'@var{program}'} @var{file} @dots{}
@end display
@cindex GNU long options
@cindex long options
@cindex options @subentry long
In addition to traditional one-letter POSIX-style options, @command{gawk} also
supports GNU long options.
@cindex dark corner @subentry invoking @command{awk}
@cindex lint checking @subentry empty programs
It is possible to invoke @command{awk} with an empty program:
@example
awk '' datafile1 datafile2
@end example
@cindex @option{--lint} option
@cindex dark corner @subentry empty programs
@noindent
Doing so makes little sense, though; @command{awk} exits
silently when given an empty program.
@value{DARKCORNER}
If @option{--lint} has
been specified on the command line, @command{gawk} issues a
warning that the program is empty.
@node Options
@section Command-Line Options
@cindex options @subentry command-line
@cindex command line @subentry options
@cindex GNU long options
@cindex options @subentry long
Options begin with a dash and consist of a single character.
GNU-style long options consist of two dashes and a keyword.
The keyword can be abbreviated, as long as the abbreviation allows the option
to be uniquely identified. If the option takes an argument, either the
keyword is immediately followed by an equals sign (@samp{=}) and the
argument's value, or the keyword and the argument's value are separated
by whitespace (spaces or TABs).
If a particular option with a value is given more than once, it is the
last value that counts.
@cindex POSIX @command{awk} @subentry GNU long options and
Each long option for @command{gawk} has a corresponding
POSIX-style short option.
The long and short options are
interchangeable in all contexts.
The following list describes options mandated by the POSIX standard:
@table @code
@item -F @var{fs}
@itemx --field-separator @var{fs}
@cindex @option{-F} option
@cindex @option{--field-separator} option
@cindex @code{FS} variable @subentry @code{--field-separator} option and
Set the @code{FS} variable to @var{fs}
(@pxref{Field Separators}).
@item -f @var{source-file}
@itemx --file @var{source-file}
@cindex @option{-f} option
@cindex @option{--file} option
@cindex @command{awk} programs @subentry location of
Read the @command{awk} program source from @var{source-file}
instead of in the first nonoption argument.
This option may be given multiple times; the @command{awk}
program consists of the concatenation of the contents of
each specified @var{source-file}.
Files named with @option{-f} are treated as if they had @samp{@@namespace "awk"}
at their beginning. @xref{Changing The Namespace}, for more information
on this advanced feature.
@item -v @var{var}=@var{val}
@itemx --assign @var{var}=@var{val}
@cindex @option{-v} option
@cindex @option{--assign} option
@cindex variables @subentry setting
Set the variable @var{var} to the value @var{val} @emph{before}
execution of the program begins. Such variable values are available
inside the @code{BEGIN} rule
(@pxref{Other Arguments}).
The @option{-v} option can only set one variable, but it can be used
more than once, setting another variable each time, like this:
@samp{awk @w{-v foo=1} @w{-v bar=2} @dots{}}.
@cindex predefined variables @subentry @code{-v} option, setting with
@cindex variables @subentry predefined @subentry @code{-v} option, setting with
@quotation CAUTION
Using @option{-v} to set the values of the built-in
variables may lead to surprising results. @command{awk} will reset the
values of those variables as it needs to, possibly ignoring any
initial value you may have given.
@end quotation
@item -W @var{gawk-opt}
@cindex @option{-W} option
Provide an implementation-specific option.
This is the POSIX convention for providing implementation-specific options.
These options
also have corresponding GNU-style long options.
Note that the long options may be abbreviated, as long as
the abbreviations remain unique.
The full list of @command{gawk}-specific options is provided next.
@item --
@cindex command line @subentry options @subentry end of
@cindex options @subentry command-line @subentry end of
Signal the end of the command-line options. The following arguments
are not treated as options even if they begin with @samp{-}. This
interpretation of @option{--} follows the POSIX argument parsing
conventions.
@cindex @code{-} (hyphen) @subentry file names beginning with
@cindex hyphen (@code{-}) @subentry file names beginning with
This is useful if you have @value{FN}s that start with @samp{-},
or in shell scripts, if you have @value{FN}s that will be specified
by the user that could start with @samp{-}.
It is also useful for passing options on to the @command{awk}
program; see @ref{Getopt Function}.
@end table
The following list describes @command{gawk}-specific options:
@c Have to use @asis here to get docbook to come out right.
@table @asis
@item @option{-b}
@itemx @option{--characters-as-bytes}
@cindex @option{-b} option
@cindex @option{--characters-as-bytes} option
Cause @command{gawk} to treat all input data as single-byte characters.
In addition, all output written with @code{print} or @code{printf}
is treated as single-byte characters.
Normally, @command{gawk} follows the POSIX standard and attempts to process
its input data according to the current locale (@pxref{Locales}). This can often involve
converting multibyte characters into wide characters (internally), and
can lead to problems or confusion if the input data does not contain valid
multibyte characters. This option is an easy way to tell @command{gawk},
``Hands off my data!''
@item @option{-c}
@itemx @option{--traditional}
@cindex @option{-c} option
@cindex @option{--traditional} option
@cindex compatibility mode (@command{gawk}) @subentry specifying
Specify @dfn{compatibility mode}, in which the GNU extensions to
the @command{awk} language are disabled, so that @command{gawk} behaves just
like BWK @command{awk}.
@xref{POSIX/GNU},
which summarizes the extensions.
@ifclear FOR_PRINT
Also see
@ref{Compatibility Mode}.
@end ifclear
@item @option{-C}
@itemx @option{--copyright}
@cindex @option{-C} option
@cindex @option{--copyright} option
@cindex GPL (General Public License) @subentry printing
Print the short version of the General Public License and then exit.
@item @option{-d}[@var{file}]
@itemx @option{--dump-variables}[@code{=}@var{file}]
@cindex @option{-d} option
@cindex @option{--dump-variables} option
@cindex dump all variables of a program
@cindex @file{awkvars.out} file
@cindex files @subentry @file{awkvars.out}
@cindex variables @subentry global @subentry printing list of
Print a sorted list of global variables, their types, and final values
to @var{file}. If no @var{file} is provided, print this
list to a file named @file{awkvars.out} in the current directory.
No space is allowed between the @option{-d} and @var{file}, if
@var{file} is supplied.
@cindex troubleshooting @subentry typographical errors, global variables
Having a list of all global variables is a good way to look for
typographical errors in your programs.
You would also use this option if you have a large program with a lot of
functions, and you want to be sure that your functions don't
inadvertently use global variables that you meant to be local.
(This is a particularly easy mistake to make with simple variable
names like @code{i}, @code{j}, etc.)
@item @option{-D}[@var{file}]
@itemx @option{--debug}[@code{=}@var{file}]
@cindex @option{-D} option
@cindex @option{--debug} option
@cindex @command{awk} programs @subentry debugging, enabling
Enable debugging of @command{awk} programs
(@pxref{Debugging}).
By default, the debugger reads commands interactively from the keyboard
(standard input).
The optional @var{file} argument allows you to specify a file with a list
of commands for the debugger to execute noninteractively.
No space is allowed between the @option{-D} and @var{file}, if
@var{file} is supplied.
@item @option{-e} @var{program-text}
@itemx @option{--source} @var{program-text}
@cindex @option{-e} option
@cindex @option{--source} option
@cindex source code @subentry mixing
Provide program source code in the @var{program-text}.
This option allows you to mix source code in files with source
code that you enter on the command line.
This is particularly useful
when you have library functions that you want to use from your command-line
programs (@pxref{AWKPATH Variable}).
Note that @command{gawk} treats each string as if it ended with
a newline character (even if it doesn't). This makes building
the total program easier.
@quotation CAUTION
Prior to @value{PVERSION} 5.0, there was
no requirement that each @var{program-text}
be a full syntactic unit. I.e., the following worked:
@example
$ @kbd{gawk -e 'BEGIN @{ a = 5 ;' -e 'print a @}'}
@print{} 5
@end example
@noindent
However, this is no longer true. If you have any scripts that
rely upon this feature, you should revise them.
This is because each @var{program-text} is treated as if it had
@samp{@@namespace "awk"} at its beginning. @xref{Changing The Namespace},
for more information.
@end quotation
@item @option{-E} @var{file}
@itemx @option{--exec} @var{file}
@cindex @option{-E} option
@cindex @option{--exec} option
@cindex @command{awk} programs @subentry location of
@cindex CGI, @command{awk} scripts for
Similar to @option{-f}, read @command{awk} program text from @var{file}.
There are two differences from @option{-f}:
@itemize @value{BULLET}
@item
This option terminates option processing; anything
else on the command line is passed on directly to the @command{awk} program.
@item
Command-line variable assignments of the form
@samp{@var{var}=@var{value}} are disallowed.
@end itemize
This option is particularly necessary for World Wide Web CGI applications
that pass arguments through the URL; using this option prevents a malicious
(or other) user from passing in options, assignments, or @command{awk} source
code (via @option{-e}) to the CGI application.@footnote{For more detail,
please see Section 4.4 of @uref{http://www.ietf.org/rfc/rfc3875,
RFC 3875}. Also see the
@uref{https://lists.gnu.org/archive/html/bug-gawk/2014-11/msg00022.html,
explanatory note sent to the @command{gawk} bug
mailing list}.}
This option should be used
with @samp{#!} scripts (@pxref{Executable Scripts}), like so:
@example
#! /usr/local/bin/gawk -E
@var{awk program here @dots{}}
@end example
@item @option{-g}
@itemx @option{--gen-pot}
@cindex @option{-g} option
@cindex @option{--gen-pot} option
@cindex portable object @subentry files @subentry generating
@cindex files @subentry portable object @subentry generating
Analyze the source program and
generate a GNU @command{gettext} portable object template file on standard
output for all string constants that have been marked for translation.
@xref{Internationalization},
for information about this option.
@item @option{-h}
@itemx @option{--help}
@cindex @option{-h} option
@cindex @option{--help} option
@cindex GNU long options @subentry printing list of
@cindex options @subentry printing list of
@cindex printing @subentry list of options
Print a ``usage'' message summarizing the short- and long-style options
that @command{gawk} accepts and then exit.
@item @option{-i} @var{source-file}
@itemx @option{--include} @var{source-file}
@cindex @option{-i} option
@cindex @option{--include} option
@cindex @command{awk} programs @subentry location of
Read an @command{awk} source library from @var{source-file}. This option
is completely equivalent to using the @code{@@include} directive inside
your program. It is very similar to the @option{-f} option,
but there are two important differences. First, when @option{-i} is
used, the program source is not loaded if it has been previously
loaded, whereas with @option{-f}, @command{gawk} always loads the file.
Second, because this option is intended to be used with code libraries,
@command{gawk} does not recognize such files as constituting main program
input. Thus, after processing an @option{-i} argument, @command{gawk}
still expects to find the main source code via the @option{-f} option
or on the command line.
Files named with @option{-i} are treated as if they had @samp{@@namespace "awk"}
at their beginning. @xref{Changing The Namespace}, for more information.
@item @option{-l} @var{ext}
@itemx @option{--load} @var{ext}
@cindex @option{-l} option
@cindex @option{--load} option
@cindex loading extensions
Load a dynamic extension named @var{ext}. Extensions
are stored as system shared libraries.
This option searches for the library using the @env{AWKLIBPATH}
environment variable. The correct library suffix for your platform will be
supplied by default, so it need not be specified in the extension name.
The extension initialization routine should be named @code{dl_load()}.
An alternative is to use the @code{@@load} keyword inside the program to load
a shared library. This advanced feature is described in detail in @ref{Dynamic Extensions}.
@item @option{-L}[@var{value}]
@itemx @option{--lint}[@code{=}@var{value}]
@cindex @option{-l} option
@cindex @option{--lint} option
@cindex lint checking @subentry issuing warnings
@cindex warnings, issuing
Warn about constructs that are dubious or nonportable to
other @command{awk} implementations.
No space is allowed between the @option{-L} and @var{value}, if
@var{value} is supplied.
Some warnings are issued when @command{gawk} first reads your program. Others
are issued at runtime, as your program executes. The optional
argument may be one of the following:
@table @code
@item fatal
Cause lint warnings become fatal errors.
This may be drastic, but its use will certainly encourage the
development of cleaner @command{awk} programs.
@item invalid
Only issue warnings about things
that are actually invalid are issued. (This is not fully implemented yet.)
@item no-ext
Disable warnings about @command{gawk} extensions.
@end table
Some warnings are only printed once, even if the dubious constructs they
warn about occur multiple times in your @command{awk} program. Thus,
when eliminating problems pointed out by @option{--lint}, you should take
care to search for all occurrences of each inappropriate construct. As
@command{awk} programs are usually short, doing so is not burdensome.
@item @option{-M}
@itemx @option{--bignum}
@cindex @option{-M} option
@cindex @option{--bignum} option
Select arbitrary-precision arithmetic on numbers. This option has no effect
if @command{gawk} is not compiled to use the GNU MPFR and MP libraries
(@pxref{Arbitrary Precision Arithmetic}).
@item @option{-n}
@itemx @option{--non-decimal-data}
@cindex @option{-n} option
@cindex @option{--non-decimal-data} option
@cindex hexadecimal values, enabling interpretation of
@cindex octal values, enabling interpretation of
@cindex troubleshooting @subentry @code{--non-decimal-data} option
Enable automatic interpretation of octal and hexadecimal
values in input data
(@pxref{Nondecimal Data}).
@quotation CAUTION
This option can severely break old programs. Use with care. Also note
that this option may disappear in a future version of @command{gawk}.
@end quotation
@item @option{-N}
@itemx @option{--use-lc-numeric}
@cindex @option{-N} option
@cindex @option{--use-lc-numeric} option
Force the use of the locale's decimal point character
when parsing numeric input data (@pxref{Locales}).
@cindex pretty printing
@item @option{-o}[@var{file}]
@itemx @option{--pretty-print}[@code{=}@var{file}]
@cindex @option{-o} option
@cindex @option{--pretty-print} option
Enable pretty-printing of @command{awk} programs.
Implies @option{--no-optimize}.
By default, the output program is created in a file named @file{awkprof.out}
(@pxref{Profiling}).
The optional @var{file} argument allows you to specify a different
@value{FN} for the output.
No space is allowed between the @option{-o} and @var{file}, if
@var{file} is supplied.
@quotation NOTE
In the past, this option would also execute your program.
This is no longer the case.
@end quotation
@item @option{-O}
@itemx @option{--optimize}
@cindex @option{--optimize} option
@cindex @option{-O} option
Enable @command{gawk}'s default optimizations on the internal
representation of the program. At the moment, this includes just simple
constant folding.
Optimization is enabled by default.
This option remains primarily for backwards compatibility. However, it may
be used to cancel the effect of an earlier @option{-s} option
(see later in this list).
@item @option{-p}[@var{file}]
@itemx @option{--profile}[@code{=}@var{file}]
@cindex @option{-p} option
@cindex @option{--profile} option
@cindex @command{awk} @subentry profiling, enabling
Enable profiling of @command{awk} programs
(@pxref{Profiling}).
Implies @option{--no-optimize}.
By default, profiles are created in a file named @file{awkprof.out}.
The optional @var{file} argument allows you to specify a different
@value{FN} for the profile file.
No space is allowed between the @option{-p} and @var{file}, if
@var{file} is supplied.
The profile contains execution counts for each statement in the program
in the left margin, and function call counts for each function.
@item @option{-P}
@itemx @option{--posix}
@cindex @option{-P} option
@cindex @option{--posix} option
@cindex POSIX mode
@cindex @command{gawk} @subentry extensions, disabling
Operate in strict POSIX mode. This disables all @command{gawk}
extensions (just like @option{--traditional}) and
disables all extensions not allowed by POSIX.
@xref{Common Extensions} for a summary of the extensions
in @command{gawk} that are disabled by this option.
Also,
the following additional
restrictions apply:
@itemize @value{BULLET}
@cindex newlines
@cindex whitespace @subentry newlines as
@item
Newlines are not allowed after @samp{?} or @samp{:}
(@pxref{Conditional Exp}).
@cindex @code{FS} variable @subentry TAB character as
@item
Specifying @samp{-Ft} on the command line does not set the value
of @code{FS} to be a single TAB character
(@pxref{Field Separators}).
@cindex locale decimal point character
@cindex decimal point character, locale specific
@item
The locale's decimal point character is used for parsing input
data (@pxref{Locales}).
@end itemize
@c @cindex automatic warnings
@c @cindex warnings, automatic
@cindex @option{--traditional} option @subentry @code{--posix} option and
@cindex @option{--posix} option @subentry @code{--traditional} option and
If you supply both @option{--traditional} and @option{--posix} on the
command line, @option{--posix} takes precedence. @command{gawk}
issues a warning if both options are supplied.
@item @option{-r}
@itemx @option{--re-interval}
@cindex @option{-r} option
@cindex @option{--re-interval} option
@cindex regular expressions @subentry interval expressions and
Allow interval expressions
(@pxref{Regexp Operators})
in regexps.
This is now @command{gawk}'s default behavior.
Nevertheless, this option remains (both for backward compatibility
and for use in combination with @option{--traditional}).
@item @option{-s}
@itemx @option{--no-optimize}
@cindex @option{--no-optimize} option
@cindex @option{-s} option
Disable @command{gawk}'s default optimizations on the internal
representation of the program.
@item @option{-S}
@itemx @option{--sandbox}
@cindex @option{-S} option
@cindex @option{--sandbox} option
@cindex sandbox mode
@cindex @code{ARGV} array
Disable the @code{system()} function,
input redirections with @code{getline},
output redirections with @code{print} and @code{printf},
and dynamic extensions.
Also, disallow adding filenames to @code{ARGV} that were
not there when @command{gawk} started running.
This is particularly useful when you want to run @command{awk} scripts
from questionable sources and need to make sure the scripts
can't access your system (other than the specified input @value{DF}s).
@item @option{-t}
@itemx @option{--lint-old}
@cindex @option{-L} option
@cindex @option{--lint-old} option
Warn about constructs that are not available in the original version of
@command{awk} from Version 7 Unix
(@pxref{V7/SVR3.1}).
@item @option{-V}
@itemx @option{--version}
@cindex @option{-V} option
@cindex @option{--version} option
@cindex @command{gawk} @subentry version of @subentry printing information about
Print version information for this particular copy of @command{gawk}.
This allows you to determine if your copy of @command{gawk} is up to date
with respect to whatever the Free Software Foundation is currently
distributing.
It is also useful for bug reports
(@pxref{Bugs}).
@cindex @code{-} (hyphen) @subentry @code{--} end of options marker
@cindex hyphen (@code{-}) @subentry @code{--} end of options marker
@item @code{--}
Mark the end of all options.
Any command-line arguments following @code{--} are placed in @code{ARGV},
even if they start with a minus sign.
@end table
As long as program text has been supplied,
any other options are flagged as invalid with a warning message but
are otherwise ignored.
@cindex @option{-F} option @subentry @option{-Ft} sets @code{FS} to TAB
In compatibility mode, as a special case, if the value of @var{fs} supplied
to the @option{-F} option is @samp{t}, then @code{FS} is set to the TAB
character (@code{"\t"}). This is true only for @option{--traditional} and not
for @option{--posix}
(@pxref{Field Separators}).
@cindex @option{-f} option @subentry multiple uses
The @option{-f} option may be used more than once on the command line.
If it is, @command{awk} reads its program source from all of the named files, as
if they had been concatenated together into one big file. This is
useful for creating libraries of @command{awk} functions. These functions
can be written once and then retrieved from a standard place, instead
of having to be included in each individual program.
The @option{-i} option is similar in this regard.
(As mentioned in
@ref{Definition Syntax},
function names must be unique.)
With standard @command{awk}, library functions can still be used, even
if the program is entered at the keyboard,
by specifying @samp{-f /dev/tty}. After typing your program,
type @kbd{Ctrl-d} (the end-of-file character) to terminate it.
(You may also use @samp{-f -} to read program source from the standard
input, but then you will not be able to also use the standard input as a
source of data.)
Because it is clumsy using the standard @command{awk} mechanisms to mix
source file and command-line @command{awk} programs, @command{gawk}
provides the @option{-e} option. This does not require you to
preempt the standard input for your source code, and it allows you to easily
mix command-line and library source code (@pxref{AWKPATH Variable}).
As with @option{-f}, the @option{-e} and @option{-i}
options may also be used multiple times on the command line.
@cindex @option{-e} option
If no @option{-f} option (or @option{-e} option for @command{gawk})
is specified, then @command{awk} uses the first nonoption command-line
argument as the text of the program source code. Arguments on
the command line that follow the program text are entered into the
@code{ARGV} array; @command{awk} does @emph{not} continue to parse the
command line looking for options.
@cindex @env{POSIXLY_CORRECT} environment variable
@cindex environment variables @subentry @env{POSIXLY_CORRECT}
@cindex lint checking @subentry @env{POSIXLY_CORRECT} environment variable
@cindex POSIX mode
If the environment variable @env{POSIXLY_CORRECT} exists,
then @command{gawk} behaves in strict POSIX mode, exactly as if
you had supplied @option{--posix}.
Many GNU programs look for this environment variable to suppress
extensions that conflict with POSIX, but @command{gawk} behaves
differently: it suppresses all extensions, even those that do not
conflict with POSIX, and behaves in
strict POSIX mode. If @option{--lint} is supplied on the command line
and @command{gawk} turns on POSIX mode because of @env{POSIXLY_CORRECT},
then it issues a warning message indicating that POSIX
mode is in effect.
You would typically set this variable in your shell's startup file.
For a Bourne-compatible shell (such as Bash), you would add these
lines to the @file{.profile} file in your home directory:
@example
POSIXLY_CORRECT=true
export POSIXLY_CORRECT
@end example
@cindex @command{csh} utility @subentry @env{POSIXLY_CORRECT} environment variable
For a C shell-compatible
shell,@footnote{Not recommended.}
you would add this line to the @file{.login} file in your home directory:
@example
setenv POSIXLY_CORRECT true
@end example
@cindex portability @subentry @env{POSIXLY_CORRECT} environment variable
Having @env{POSIXLY_CORRECT} set is not recommended for daily use,
but it is good for testing the portability of your programs to other
environments.
@node Other Arguments
@section Other Command-Line Arguments
@cindex command line @subentry arguments
@cindex arguments @subentry command-line
Any additional arguments on the command line are normally treated as
input files to be processed in the order specified. However, an
argument that has the form @code{@var{var}=@var{value}}, assigns
the value @var{value} to the variable @var{var}---it does not specify a
file at all. (See @ref{Assignment Options}.) In the following example,
@var{count=1} is a variable assignment, not a @value{FN}:
@example
awk -f program.awk file1 count=1 file2
@end example
@noindent
As a side point, should you really need to have @command{awk}
process a file named @file{count=1} (or any file whose name looks like
a variable assignment), precede the file name with @samp{./}, like so:
@example
awk -f program.awk file1 ./count=1 file2
@end example
@cindex @command{gawk} @subentry @code{ARGIND} variable in
@cindex @code{ARGIND} variable @subentry command-line arguments
@cindex @code{ARGV} array, indexing into
@cindex @code{ARGC}/@code{ARGV} variables @subentry command-line arguments
@cindex @command{gawk} @subentry @code{PROCINFO} array in
All the command-line arguments are made available to your @command{awk} program in the
@code{ARGV} array (@pxref{Built-in Variables}). Command-line options
and the program text (if present) are omitted from @code{ARGV}.
All other arguments, including variable assignments, are
included. As each element of @code{ARGV} is processed, @command{gawk}
sets @code{ARGIND} to the index in @code{ARGV} of the
current element. (@command{gawk} makes the full command line,
including program text and options, available in @code{PROCINFO["argv"]};
@pxref{Auto-set}.)
@c FIXME: One day, move the ARGC and ARGV node closer to here.
Changing @code{ARGC} and @code{ARGV} in your @command{awk} program lets
you control how @command{awk} processes the input files; this is described
in more detail in @ref{ARGC and ARGV}.
@cindex input files @subentry variable assignments and
@cindex variable assignments and input files
The distinction between @value{FN} arguments and variable-assignment
arguments is made when @command{awk} is about to open the next input file.
At that point in execution, it checks the @value{FN} to see whether
it is really a variable assignment; if so, @command{awk} sets the variable
instead of reading a file.
Therefore, the variables actually receive the given values after all
previously specified files have been read. In particular, the values of
variables assigned in this fashion are @emph{not} available inside a
@code{BEGIN} rule
(@pxref{BEGIN/END}),
because such rules are run before @command{awk} begins scanning the argument list.
@cindex dark corner @subentry escape sequences
The variable values given on the command line are processed for escape
sequences (@pxref{Escape Sequences}).
@value{DARKCORNER}
In some very early implementations of @command{awk}, when a variable assignment
occurred before any @value{FN}s, the assignment would happen @emph{before}
the @code{BEGIN} rule was executed. @command{awk}'s behavior was thus
inconsistent; some command-line assignments were available inside the
@code{BEGIN} rule, while others were not. Unfortunately,
some applications came to depend
upon this ``feature.'' When @command{awk} was changed to be more consistent,
the @option{-v} option was added to accommodate applications that depended
upon the old behavior.
The variable assignment feature is most useful for assigning to variables
such as @code{RS}, @code{OFS}, and @code{ORS}, which control input and
output formats, before scanning the @value{DF}s. It is also useful for
controlling state if multiple passes are needed over a @value{DF}. For
example:
@cindex files @subentry multiple passes over
@example
awk 'pass == 1 @{ @var{pass 1 stuff} @}
pass == 2 @{ @var{pass 2 stuff} @}' pass=1 mydata pass=2 mydata
@end example
Given the variable assignment feature, the @option{-F} option for setting
the value of @code{FS} is not
strictly necessary. It remains for historical compatibility.
@node Naming Standard Input
@section Naming Standard Input
Often, you may wish to read standard input together with other files.
For example, you may wish to read one file, read standard input coming
from a pipe, and then read another file.
The way to name the standard input, with all versions of @command{awk},
is to use a single, standalone minus sign or dash, @samp{-}. For example:
@example
@var{some_command} | awk -f myprog.awk file1 - file2
@end example
@noindent
Here, @command{awk} first reads @file{file1}, then it reads
the output of @var{some_command}, and finally it reads
@file{file2}.
You may also use @code{"-"} to name standard input when reading
files with @code{getline} (@pxref{Getline/File}).
And, you can even use @code{"-"} with the @option{-f} option
to read program source code from standard input (@pxref{Options}).
In addition, @command{gawk} allows you to specify the special
@value{FN} @file{/dev/stdin}, both on the command line and
with @code{getline}.
Some other versions of @command{awk} also support this, but it
is not standard.
(Some operating systems provide a @file{/dev/stdin} file
in the filesystem; however, @command{gawk} always processes
this @value{FN} itself.)
@node Environment Variables
@section The Environment Variables @command{gawk} Uses
@cindex environment variables @subentry used by @command{gawk}
A number of environment variables influence how @command{gawk}
behaves.
@menu
* AWKPATH Variable:: Searching directories for @command{awk}
programs.
* AWKLIBPATH Variable:: Searching directories for @command{awk} shared
libraries.
* Other Environment Variables:: The environment variables.
@end menu
@node AWKPATH Variable
@subsection The @env{AWKPATH} Environment Variable
@cindex @env{AWKPATH} environment variable
@cindex environment variables @subentry @env{AWKPATH}
@cindex directories @subentry searching @subentry for source files
@cindex search paths @subentry for source files
@cindex differences in @command{awk} and @command{gawk} @subentry @env{AWKPATH} environment variable
@ifinfo
The previous @value{SECTION} described how @command{awk} program files can be named
on the command line with the @option{-f} option.
@end ifinfo
In most @command{awk}
implementations, you must supply a precise pathname for each program
file, unless the file is in the current directory.
But with @command{gawk}, if the @value{FN} supplied to the @option{-f}
or @option{-i} options
does not contain a directory separator @samp{/}, then @command{gawk} searches a list of
directories (called the @dfn{search path}) one by one, looking for a
file with the specified name.
The search path is a string consisting of directory names
separated by colons.@footnote{Semicolons on MS-Windows.}
@command{gawk} gets its search path from the
@env{AWKPATH} environment variable. If that variable does not exist,
or if it has an empty value,
@command{gawk} uses a default path (described shortly).
The search path feature is particularly helpful for building libraries
of useful @command{awk} functions. The library files can be placed in a
standard directory in the default path and then specified on
the command line with a short @value{FN}. Otherwise, you would have to
type the full @value{FN} for each file.
By using the @option{-i} or @option{-f} options, your command-line
@command{awk} programs can use facilities in @command{awk} library files
(@pxref{Library Functions}).
Path searching is not done if @command{gawk} is in compatibility mode.
This is true for both @option{--traditional} and @option{--posix}.
@xref{Options}.
If the source code file is not found after the initial search, the path is searched
again after adding the suffix @samp{.awk} to the @value{FN}.
@command{gawk}'s path search mechanism is similar
to the shell's.
(See @uref{https://www.gnu.org/software/bash/manual/,
@cite{The Bourne-Again SHell manual}}.)
It treats a null entry in the path as indicating the current
directory.
(A null entry is indicated by starting or ending the path with a
colon or by placing two colons next to each other [@samp{::}].)
@quotation NOTE
To include the current directory in the path, either place @file{.}
as an entry in the path or write a null entry in the path.
Different past versions of @command{gawk} would also look explicitly in
the current directory, either before or after the path search. As of
@value{PVERSION} 4.1.2, this no longer happens; if you wish to look
in the current directory, you must include @file{.} either as a separate
entry or as a null entry in the search path.
@end quotation
The default value for @env{AWKPATH} is
@samp{.:/usr/local/share/awk}.@footnote{Your version of @command{gawk}
may use a different directory; it
will depend upon how @command{gawk} was built and installed. The actual
directory is the value of @code{$(pkgdatadir)} generated when
@command{gawk} was configured.
(For more detail, see the @file{INSTALL} file in the source distribution,
and see @ref{Quick Installation}.
You probably don't need to worry about this,
though.)} Since @file{.} is included at the beginning, @command{gawk}
searches first in the current directory and then in @file{/usr/local/share/awk}.
In practice, this means that you will rarely need to change the
value of @env{AWKPATH}.
@xref{Shell Startup Files}, for information on functions that help to
manipulate the @env{AWKPATH} variable.
@command{gawk} places the value of the search path that it used into
@code{ENVIRON["AWKPATH"]}. This provides access to the actual search
path value from within an @command{awk} program.
Although you can change @code{ENVIRON["AWKPATH"]} within your @command{awk}
program, this has no effect on the running program's behavior. This makes
sense: the @env{AWKPATH} environment variable is used to find the program
source files. Once your program is running, all the files have been
found, and @command{gawk} no longer needs to use @env{AWKPATH}.
@node AWKLIBPATH Variable
@subsection The @env{AWKLIBPATH} Environment Variable
@cindex @env{AWKLIBPATH} environment variable
@cindex environment variables @subentry @env{AWKLIBPATH}
@cindex directories @subentry searching @subentry for loadable extensions
@cindex search paths @subentry for loadable extensions
@cindex differences in @command{awk} and @command{gawk} @subentry @code{AWKLIBPATH} environment variable
The @env{AWKLIBPATH} environment variable is similar to the @env{AWKPATH}
variable, but it is used to search for loadable extensions (stored as
system shared libraries) specified with the @option{-l} option rather
than for source files. If the extension is not found, the path is
searched again after adding the appropriate shared library suffix for
the platform. For example, on GNU/Linux systems, the suffix @samp{.so}
is used. The search path specified is also used for extensions loaded
via the @code{@@load} keyword (@pxref{Loading Shared Libraries}).
If @env{AWKLIBPATH} does not exist in the environment, or if it has
an empty value, @command{gawk} uses a default path; this
is typically @samp{/usr/local/lib/gawk}, although it can vary depending
upon how @command{gawk} was built.@footnote{Your version of @command{gawk}
may use a different directory; it
will depend upon how @command{gawk} was built and installed. The actual
directory is the value of @code{$(pkgextensiondir)} generated when
@command{gawk} was configured.
(For more detail, see the @file{INSTALL} file in the source distribution,
and see @ref{Quick Installation}.
You probably don't need to worry about this,
though.)}
@xref{Shell Startup Files}, for information on functions that help to
manipulate the @env{AWKLIBPATH} variable.
@command{gawk} places the value of the search path that it used into
@code{ENVIRON["AWKLIBPATH"]}. This provides access to the actual search
path value from within an @command{awk} program.
Although you can change @code{ENVIRON["AWKLIBPATH"]} within your
@command{awk} program, this has no effect on the running program's
behavior. This makes sense: the @env{AWKLIBPATH} environment variable
is used to find any requested extensions, and they are loaded before
the program starts to run. Once your program is running, all the
extensions have been found, and @command{gawk} no longer needs to use
@env{AWKLIBPATH}.
@node Other Environment Variables
@subsection Other Environment Variables
A number of other environment variables affect @command{gawk}'s
behavior, but they are more specialized. Those in the following
list are meant to be used by regular users:
@table @env
@item GAWK_MSEC_SLEEP
Specifies the interval between connection retries,
in milliseconds. On systems that do not support
the @code{usleep()} system call,
the value is rounded up to an integral number of seconds.
@item GAWK_READ_TIMEOUT
Specifies the time, in milliseconds, for @command{gawk} to
wait for input before returning with an error.
@xref{Read Timeout}.
@item GAWK_SOCK_RETRIES
Controls the number of times @command{gawk} attempts to
retry a two-way TCP/IP (socket) connection before giving up.
@xref{TCP/IP Networking}.
Note that when nonfatal I/O is enabled (@pxref{Nonfatal}),
@command{gawk} only tries to open a TCP/IP socket once.
@item POSIXLY_CORRECT
Causes @command{gawk} to switch to POSIX-compatibility
mode, disabling all traditional and GNU extensions.
@xref{Options}.
@end table
The environment variables in the following list are meant
for use by the @command{gawk} developers for testing and tuning.
They are subject to change. The variables are:
@table @env
@item AWKBUFSIZE
This variable only affects @command{gawk} on POSIX-compliant systems.
With a value of @samp{exact}, @command{gawk} uses the size of each input
file as the size of the memory buffer to allocate for I/O. Otherwise,
the value should be a number, and @command{gawk} uses that number as
the size of the buffer to allocate. (When this variable is not set,
@command{gawk} uses the smaller of the file's size and the ``default''
blocksize, which is usually the filesystem's I/O blocksize.)
@item AWK_HASH
If this variable exists with a value of @samp{gst}, @command{gawk}
switches to using the hash function from GNU Smalltalk for
managing arrays.
This function may be marginally faster than the standard function.
@item AWKREADFUNC
If this variable exists, @command{gawk} switches to reading source
files one line at a time, instead of reading in blocks. This exists
for debugging problems on filesystems on non-POSIX operating systems
where I/O is performed in records, not in blocks.
@item GAWK_MSG_SRC
If this variable exists, @command{gawk} includes the @value{FN}
and line number within the @command{gawk} source code
from which warning and/or fatal messages
are generated. Its purpose is to help isolate the source of a
message, as there are multiple places that produce the
same warning or error message.
@item GAWK_LOCALE_DIR
Specifies the location of compiled message object files
for @command{gawk} itself. This is passed to the @code{bindtextdomain()}
function when @command{gawk} starts up.
@item GAWK_NO_DFA
If this variable exists, @command{gawk} does not use the DFA regexp matcher
for ``does it match'' kinds of tests. This can cause @command{gawk}
to be slower. Its purpose is to help isolate differences between the
two regexp matchers that @command{gawk} uses internally. (There aren't
supposed to be differences, but occasionally theory and practice don't
coordinate with each other.)
@item GAWK_STACKSIZE
This specifies the amount by which @command{gawk} should grow its
internal evaluation stack, when needed.
@item INT_CHAIN_MAX
This specifies intended maximum number of items @command{gawk} will maintain on a
hash chain for managing arrays indexed by integers.
@item STR_CHAIN_MAX
This specifies intended maximum number of items @command{gawk} will maintain on a
hash chain for managing arrays indexed by strings.
@item TIDYMEM
If this variable exists, @command{gawk} uses the @code{mtrace()} library
calls from the GNU C library to help track down possible memory leaks.
@end table
@node Exit Status
@section @command{gawk}'s Exit Status
@cindex exit status, of @command{gawk}
If the @code{exit} statement is used with a value
(@pxref{Exit Statement}), then @command{gawk} exits with
the numeric value given to it.
Otherwise, if there were no problems during execution,
@command{gawk} exits with the value of the C constant
@code{EXIT_SUCCESS}. This is usually zero.
If an error occurs, @command{gawk} exits with the value of
the C constant @code{EXIT_FAILURE}. This is usually one.
If @command{gawk} exits because of a fatal error, the exit
status is two. On non-POSIX systems, this value may be mapped
to @code{EXIT_FAILURE}.
@node Include Files
@section Including Other Files into Your Program
@c Panos Papadopoulos <panos1962@gmail.com> contributed the original
@c text for this section.
This @value{SECTION} describes a feature that is specific to @command{gawk}.
@cindex @code{@@} (at-sign) @subentry @code{@@include} directive
@cindex at-sign (@code{@@}) @subentry @code{@@include} directive
@cindex file inclusion, @code{@@include} directive
@cindex including files, @code{@@include} directive
@cindex @code{@@include} directive @sortas{include directive}
The @code{@@include} keyword can be used to read external @command{awk} source
files. This gives you the ability to split large @command{awk} source files
into smaller, more manageable pieces, and also lets you reuse common @command{awk}
code from various @command{awk} scripts. In other words, you can group
together @command{awk} functions used to carry out specific tasks
into external files. These files can be used just like function libraries,
using the @code{@@include} keyword in conjunction with the @env{AWKPATH}
environment variable. Note that source files may also be included
using the @option{-i} option.
Let's see an example.
We'll start with two (trivial) @command{awk} scripts, namely
@file{test1} and @file{test2}. Here is the @file{test1} script:
@example
BEGIN @{
print "This is script test1."
@}
@end example
@noindent
and here is @file{test2}:
@example
@@include "test1"
BEGIN @{
print "This is script test2."
@}
@end example
Running @command{gawk} with @file{test2}
produces the following result:
@example
$ @kbd{gawk -f test2}
@print{} This is script test1.
@print{} This is script test2.
@end example
@command{gawk} runs the @file{test2} script, which includes @file{test1}
using the @code{@@include}
keyword. So, to include external @command{awk} source files, you just
use @code{@@include} followed by the name of the file to be included,
enclosed in double quotes.
@quotation NOTE
Keep in mind that this is a language construct and the @value{FN} cannot
be a string variable, but rather just a literal string constant in double quotes.
@end quotation
The files to be included may be nested; e.g., given a third
script, namely @file{test3}:
@example
@group
@@include "test2"
BEGIN @{
print "This is script test3."
@}
@end group
@end example
@noindent
Running @command{gawk} with the @file{test3} script produces the
following results:
@example
$ @kbd{gawk -f test3}
@print{} This is script test1.
@print{} This is script test2.
@print{} This is script test3.
@end example
The @value{FN} can, of course, be a pathname. For example:
@example
@@include "../io_funcs"
@end example
@noindent
and:
@example
@@include "/usr/awklib/network"
@end example
@noindent
are both valid. The @env{AWKPATH} environment variable can be of great
value when using @code{@@include}. The same rules for the use
of the @env{AWKPATH} variable in command-line file searches
(@pxref{AWKPATH Variable}) apply to
@code{@@include} also.
This is very helpful in constructing @command{gawk} function libraries.
If you have a large script with useful, general-purpose @command{awk}
functions, you can break it down into library files and put those files
in a special directory. You can then include those ``libraries,''
either by using the full pathnames of the files, or by setting the @env{AWKPATH}
environment variable accordingly and then using @code{@@include} with
just the file part of the full pathname. Of course,
you can keep library files in more than one directory;
the more complex the working
environment is, the more directories you may need to organize the files
to be included.
Given the ability to specify multiple @option{-f} options, the
@code{@@include} mechanism is not strictly necessary.
However, the @code{@@include} keyword
can help you in constructing self-contained @command{gawk} programs,
thus reducing the need for writing complex and tedious command lines.
In particular, @code{@@include} is very useful for writing CGI scripts
to be run from web pages.
The rules for finding a source file described in @ref{AWKPATH Variable} also
apply to files loaded with @code{@@include}.
Finally, files included with @code{@@include}
are treated as if they had @samp{@@namespace "awk"}
at their beginning. @xref{Changing The Namespace}, for more information.
@node Loading Shared Libraries
@section Loading Dynamic Extensions into Your Program
This @value{SECTION} describes a feature that is specific to @command{gawk}.
@cindex @code{@@} (at-sign) @subentry @code{@@load} directive
@cindex at-sign (@code{@@}) @subentry @code{@@load} directive
@cindex loading extensions @subentry @code{@@load} directive
@cindex extensions @subentry loadable @subentry loading, @code{@@load} directive
@cindex @code{@@load} directive @sortas{load directive}
The @code{@@load} keyword can be used to read external @command{awk} extensions
(stored as system shared libraries).
This allows you to link in compiled code that may offer superior
performance and/or give you access to extended capabilities not supported
by the @command{awk} language. The @env{AWKLIBPATH} variable is used to
search for the extension. Using @code{@@load} is completely equivalent
to using the @option{-l} command-line option.
If the extension is not initially found in @env{AWKLIBPATH}, another
search is conducted after appending the platform's default shared library
suffix to the @value{FN}. For example, on GNU/Linux systems, the suffix
@samp{.so} is used:
@example
$ @kbd{gawk '@@load "ordchr"; BEGIN @{print chr(65)@}'}
@print{} A
@end example
@noindent
This is equivalent to the following example:
@example
@group
$ @kbd{gawk -lordchr 'BEGIN @{print chr(65)@}'}
@print{} A
@end group
@end example
@noindent
For command-line usage, the @option{-l} option is more convenient,
but @code{@@load} is useful for embedding inside an @command{awk} source file
that requires access to an extension.
@ref{Dynamic Extensions}, describes how to write extensions (in C or C++)
that can be loaded with either @code{@@load} or the @option{-l} option.
It also describes the @code{ordchr} extension.
@node Obsolete
@section Obsolete Options and/or Features
@c update this section for each release!
@cindex options @subentry deprecated
@cindex features @subentry deprecated
@cindex obsolete features
This @value{SECTION} describes features and/or command-line options from
previous releases of @command{gawk} that either are not available in the
current version or are still supported but deprecated (meaning that
they will @emph{not} be in the next release).
The process-related special files @file{/dev/pid}, @file{/dev/ppid},
@file{/dev/pgrpid}, and @file{/dev/user} were deprecated in @command{gawk}
3.1, but still worked. As of @value{PVERSION} 4.0, they are no longer
interpreted specially by @command{gawk}. (Use @code{PROCINFO} instead;
see @ref{Auto-set}.)
@ignore
This @value{SECTION}
is thus essentially a place holder,
in case some option becomes obsolete in a future version of @command{gawk}.
@end ignore
@node Undocumented
@section Undocumented Options and Features
@cindex undocumented features
@cindex features @subentry undocumented
@cindex Skywalker, Luke
@cindex Kenobi, Obi-Wan
@cindex jedi knights
@cindex knights, jedi
@quotation
@i{Use the Source, Luke!}
@author Obi-Wan
@end quotation
@cindex shells @subentry sea
This @value{SECTION} intentionally left
blank.
@ignore
@c If these came out in the Info file or TeX document, then they wouldn't
@c be undocumented, would they?
@command{gawk} has one undocumented option:
@table @code
@item -W nostalgia
@itemx --nostalgia
Print the message @samp{awk: bailing out near line 1} and dump core.
This option was inspired by the common behavior of very early versions of
Unix @command{awk} and by a t--shirt.
The message is @emph{not} subject to translation in non-English locales.
@c so there! nyah, nyah.
@end table
Early versions of @command{awk} used to not require any separator (either
a newline or @samp{;}) between the rules in @command{awk} programs. Thus,
it was common to see one-line programs like:
@example
awk '@{ sum += $1 @} END @{ print sum @}'
@end example
@command{gawk} actually supports this but it is purposely undocumented
because it is bad style. The correct way to write such a program
is either:
@example
awk '@{ sum += $1 @} ; END @{ print sum @}'
@end example
@noindent
or:
@example
awk '@{ sum += $1 @}
END @{ print sum @}' data
@end example
@noindent
@xref{Statements/Lines}, for a fuller explanation.
You can insert newlines after the @samp{;} in @code{for} loops.
This seems to have been a long-undocumented feature in Unix @command{awk}.
Similarly, you may use @code{print} or @code{printf} statements in the
@var{init} and @var{increment} parts of a @code{for} loop. This is another
long-undocumented ``feature'' of Unix @command{awk}.
@command{gawk} lets you use the names of built-in functions that are
@command{gawk} extensions as the names of parameters in user-defined functions.
This is intended to ``future-proof'' old code that happens to use
function names added by @command{gawk} after the code was written.
Standard @command{awk} built-in functions, such as @code{sin()} or
@code{substr()} are @emph{not} shadowed in this way.
You can use a @samp{P} modifier for the @code{printf()} floating-point
format control letters to use the underlying C library's result for
NaN and Infinity values, instead of the special values @command{gawk}
usually produces, as described in @ref{POSIX Floating Point Problems}.
This is mainly useful for the included unit tests.
The @code{typeof()} built-in function
(@pxref{Type Functions})
takes an optional second array argument that, if present, will be cleared
and populated with some information about the internal implementation of
the variable. This can be useful for debugging. At the moment, this
returns a textual version of the flags for scalar variables, and the
array back-end implementation type for arrays. This interface is subject
to change and may not be stable.
When not in POSIX or compatibility mode, if you set @code{LINENO} to a
numeric value using the @option{-v} option, @command{gawk} adds that value
to the real line number for use in error messages. This is intended for
use within Bash shell scripts, such that the error message will reflect
the line number in the shell script, instead of in the @command{awk}
program. To demonstrate:
@example
$ @kbd{gawk -v LINENO=10 'BEGIN @{ print("hi" @}'}
@error{} gawk: cmd. line:11: BEGIN @{ print("hi" @}
@error{} gawk: cmd. line:11: ^ syntax error
@end example
@end ignore
@node Invoking Summary
@section Summary
@itemize @value{BULLET}
@c From Neil R. Ormos
@item
@command{gawk} parses arguments on the command line, left to right, to
determine if they should be treated as options or as non-option arguments.
@item
@command{gawk} recognizes several options which control its operation,
as described in @ref{Options}. All options begin with @samp{-}.
@item
Any argument that is not recognized as an option is treated as a
non-option argument, even if it begins with @samp{-}.
@itemize @value{MINUS}
@item
However, when an option itself requires an argument, and the option is separated
from that argument on the command line by at least one space, the space
is ignored, and the argument is considered to be related to the option. Thus, in
the invocation, @samp{gawk -F x}, the @samp{x} is treated as belonging to the
@option{-F} option, not as a separate non-option argument.
@end itemize
@item
Once @command{gawk} finds a non-option argument, it stops looking for
options. Therefore, all following arguments are also non-option arguments,
even if they resemble recognized options.
@item
If no @option{-e} or @option{-f} options are present, @command{gawk}
expects the program text to be in the first non-option argument.
@item
All non-option arguments, except program text provided in the first
non-option argument, are placed in @code{ARGV} as explained in
@ref{ARGC and ARGV}, and are processed as described in @ref{Other Arguments}.
@c And I wrote:
Adjusting @code{ARGC} and @code{ARGV}
affects how @command{awk} processes input.
@c ----------------------------------------
@item
The three standard options for all versions of @command{awk} are
@option{-f}, @option{-F}, and @option{-v}. @command{gawk} supplies these
and many others, as well as corresponding GNU-style long options.
@item
Nonoption command-line arguments are usually treated as @value{FN}s,
unless they have the form @samp{@var{var}=@var{value}}, in which case
they are taken as variable assignments to be performed at that point
in processing the input.
@item
You can use a single minus sign (@samp{-}) to refer to standard input
on the command line. @command{gawk} also lets you use the special
@value{FN} @file{/dev/stdin}.
@item
@command{gawk} pays attention to a number of environment variables.
@env{AWKPATH}, @env{AWKLIBPATH}, and @env{POSIXLY_CORRECT} are the
most important ones.
@item
@command{gawk}'s exit status conveys information to the program
that invoked it. Use the @code{exit} statement from within
an @command{awk} program to set the exit status.
@item
@command{gawk} allows you to include other @command{awk} source files into
your program using the @code{@@include} statement and/or the @option{-i}
and @option{-f} command-line options.
@item
@command{gawk} allows you to load additional functions written in C
or C++ using the @code{@@load} statement and/or the @option{-l} option.
(This advanced feature is described later, in @ref{Dynamic Extensions}.)
@end itemize
@node Regexp
@chapter Regular Expressions
@cindex regexp
@cindex regular expressions
A @dfn{regular expression}, or @dfn{regexp}, is a way of describing a
set of strings.
Because regular expressions are such a fundamental part of @command{awk}
programming, their format and use deserve a separate @value{CHAPTER}.
@cindex forward slash (@code{/}) @subentry to enclose regular expressions
@cindex @code{/} (forward slash) @subentry to enclose regular expressions
A regular expression enclosed in slashes (@samp{/})
is an @command{awk} pattern that matches every input record whose text
belongs to that set.
The simplest regular expression is a sequence of letters, numbers, or
both. Such a regexp matches any string that contains that sequence.
Thus, the regexp @samp{foo} matches any string containing @samp{foo}.
Thus, the pattern @code{/foo/} matches any input record containing
the three adjacent characters @samp{foo} @emph{anywhere} in the record. Other
kinds of regexps let you specify more complicated classes of strings.
@ifnotinfo
Initially, the examples in this @value{CHAPTER} are simple.
As we explain more about how
regular expressions work, we present more complicated instances.
@end ifnotinfo
@menu
* Regexp Usage:: How to Use Regular Expressions.
* Escape Sequences:: How to write nonprinting characters.
* Regexp Operators:: Regular Expression Operators.
* Bracket Expressions:: What can go between @samp{[...]}.
* Leftmost Longest:: How much text matches.
* Computed Regexps:: Using Dynamic Regexps.
* GNU Regexp Operators:: Operators specific to GNU software.
* Case-sensitivity:: How to do case-insensitive matching.
* Regexp Summary:: Regular expressions summary.
@end menu
@node Regexp Usage
@section How to Use Regular Expressions
@cindex patterns @subentry regexp constants as
@cindex regular expressions @subentry as patterns
A regular expression can be used as a pattern by enclosing it in
slashes. Then the regular expression is tested against the
entire text of each record. (Normally, it only needs
to match some part of the text in order to succeed.) For example, the
following prints the second field of each record where the string
@samp{li} appears anywhere in the record:
@example
$ @kbd{awk '/li/ @{ print $2 @}' mail-list}
@print{} 555-5553
@print{} 555-0542
@print{} 555-6699
@print{} 555-3430
@end example
@cindex regular expressions @subentry operators
@cindex operators @subentry string-matching
@c @cindex operators, @code{~}
@cindex string-matching operators
@cindex @code{~} (tilde), @code{~} operator
@cindex tilde (@code{~}), @code{~} operator
@cindex @code{!} (exclamation point) @subentry @code{!~} operator
@cindex exclamation point (@code{!}) @subentry @code{!~} operator
@c @cindex operators, @code{!~}
@cindex @code{if} statement @subentry use of regexps in
@cindex @code{while} statement @subentry use of regexps in
@cindex @code{do}-@code{while} statement @subentry use of regexps in
@c @cindex statements, @code{if}
@c @cindex statements, @code{while}
@c @cindex statements, @code{do}
Regular expressions can also be used in matching expressions. These
expressions allow you to specify the string to match against; it need
not be the entire current input record. The two operators @samp{~}
and @samp{!~} perform regular expression comparisons. Expressions
using these operators can be used as patterns, or in @code{if},
@code{while}, @code{for}, and @code{do} statements.
(@xref{Statements}.)
For example, the following is true if the expression @var{exp} (taken
as a string) matches @var{regexp}:
@example
@var{exp} ~ /@var{regexp}/
@end example
@noindent
This example matches, or selects, all input records with the uppercase
letter @samp{J} somewhere in the first field:
@example
$ @kbd{awk '$1 ~ /J/' inventory-shipped}
@print{} Jan 13 25 15 115
@print{} Jun 31 42 75 492
@print{} Jul 24 34 67 436
@print{} Jan 21 36 64 620
@end example
So does this:
@example
awk '@{ if ($1 ~ /J/) print @}' inventory-shipped
@end example
This next example is true if the expression @var{exp}
(taken as a character string)
does @emph{not} match @var{regexp}:
@example
@var{exp} !~ /@var{regexp}/
@end example
The following example matches,
or selects, all input records whose first field @emph{does not} contain
the uppercase letter @samp{J}:
@example
$ @kbd{awk '$1 !~ /J/' inventory-shipped}
@print{} Feb 15 32 24 226
@print{} Mar 15 24 34 228
@print{} Apr 31 52 63 420
@print{} May 16 34 29 208
@dots{}
@end example
@cindex regexp constants
@cindex constants @subentry regexp
@cindex regular expressions, constants @seeentry{regexp constants}
When a regexp is enclosed in slashes, such as @code{/foo/}, we call it
a @dfn{regexp constant}, much like @code{5.27} is a numeric constant and
@code{"foo"} is a string constant.
@node Escape Sequences
@section Escape Sequences
@cindex escape sequences
@cindex escape sequences @seealso{backslash}
@cindex backslash (@code{\}) @subentry in escape sequences
@cindex @code{\} (backslash) @subentry in escape sequences
Some characters cannot be included literally in string constants
(@code{"foo"}) or regexp constants (@code{/foo/}).
Instead, they should be represented with @dfn{escape sequences},
which are character sequences beginning with a backslash (@samp{\}).
One use of an escape sequence is to include a double-quote character in
a string constant. Because a plain double quote ends the string, you
must use @samp{\"} to represent an actual double-quote character as a
part of the string. For example:
@example
$ @kbd{awk 'BEGIN @{ print "He said \"hi!\" to her." @}'}
@print{} He said "hi!" to her.
@end example
The backslash character itself is another character that cannot be
included normally; you must write @samp{\\} to put one backslash in the
string or regexp. Thus, the string whose contents are the two characters
@samp{"} and @samp{\} must be written @code{"\"\\"}.
Other escape sequences represent unprintable characters
such as TAB or newline. There is nothing to stop you from entering most
unprintable characters directly in a string constant or regexp constant,
but they may look ugly.
The following list presents
all the escape sequences used in @command{awk} and
what they represent. Unless noted otherwise, all these escape
sequences apply to both string constants and regexp constants:
@cindex ASCII
@table @code
@item \\
A literal backslash, @samp{\}.
@c @cindex @command{awk} language, V.4 version
@cindex @code{\} (backslash) @subentry @code{\a} escape sequence
@cindex backslash (@code{\}) @subentry @code{\a} escape sequence
@item \a
The ``alert'' character, @kbd{Ctrl-g}, ASCII code 7 (BEL).
(This often makes some sort of audible noise.)
@cindex @code{\} (backslash) @subentry @code{\b} escape sequence
@cindex backslash (@code{\}) @subentry @code{\b} escape sequence
@item \b
Backspace, @kbd{Ctrl-h}, ASCII code 8 (BS).
@cindex @code{\} (backslash) @subentry @code{\f} escape sequence
@cindex backslash (@code{\}) @subentry @code{\f} escape sequence
@item \f
Formfeed, @kbd{Ctrl-l}, ASCII code 12 (FF).
@cindex @code{\} (backslash) @subentry @code{\n} escape sequence
@cindex backslash (@code{\}) @subentry @code{\n} escape sequence
@item \n
Newline, @kbd{Ctrl-j}, ASCII code 10 (LF).
@cindex @code{\} (backslash) @subentry @code{\r} escape sequence
@cindex backslash (@code{\}) @subentry @code{\r} escape sequence
@item \r
Carriage return, @kbd{Ctrl-m}, ASCII code 13 (CR).
@cindex @code{\} (backslash) @subentry @code{\t} escape sequence
@cindex backslash (@code{\}) @subentry @code{\t} escape sequence
@item \t
Horizontal TAB, @kbd{Ctrl-i}, ASCII code 9 (HT).
@c @cindex @command{awk} language, V.4 version
@cindex @code{\} (backslash) @subentry @code{\v} escape sequence
@cindex backslash (@code{\}) @subentry @code{\v} escape sequence
@item \v
Vertical TAB, @kbd{Ctrl-k}, ASCII code 11 (VT).
@cindex @code{\} (backslash) @subentry @code{\}@var{nnn} escape sequence
@cindex backslash (@code{\}) @subentry @code{\}@var{nnn} escape sequence
@item \@var{nnn}
The octal value @var{nnn}, where @var{nnn} stands for 1 to 3 digits
between @samp{0} and @samp{7}. For example, the code for the ASCII ESC
(escape) character is @samp{\033}.
@c @cindex @command{awk} language, V.4 version
@c @cindex @command{awk} language, POSIX version
@cindex @code{\} (backslash) @subentry @code{\x} escape sequence
@cindex backslash (@code{\}) @subentry @code{\x} escape sequence
@cindex common extensions @subentry @code{\x} escape sequence
@cindex extensions @subentry common @subentry @code{\x} escape sequence
@item \x@var{hh}@dots{}
The hexadecimal value @var{hh}, where @var{hh} stands for a sequence
of hexadecimal digits (@samp{0}--@samp{9}, and either @samp{A}--@samp{F}
or @samp{a}--@samp{f}). A maximum of two digts are allowed after
the @samp{\x}. Any further hexadecimal digits are treated as simple
letters or numbers. @value{COMMONEXT}
(The @samp{\x} escape sequence is not allowed in POSIX awk.)
@quotation CAUTION
In ISO C, the escape sequence continues until the first nonhexadecimal
digit is seen.
For many years, @command{gawk} would continue incorporating
hexadecimal digits into the value until a non-hexadecimal digit
or the end of the string was encountered.
However, using more than two hexadecimal digits produced
undefined results.
As of @value{PVERSION} 4.2, only two digits
are processed.
@end quotation
@cindex @code{\} (backslash) @subentry @code{\/} escape sequence
@cindex backslash (@code{\}) @subentry @code{\/} escape sequence
@item \/
A literal slash (should be used for regexp constants only).
This sequence is used when you want to write a regexp
constant that contains a slash
(such as @code{/.*:\/home\/[[:alnum:]]+:.*/}; the @samp{[[:alnum:]]}
notation is discussed in @ref{Bracket Expressions}).
Because the regexp is delimited by
slashes, you need to escape any slash that is part of the pattern,
in order to tell @command{awk} to keep processing the rest of the regexp.
@cindex @code{\} (backslash) @subentry @code{\"} escape sequence
@cindex backslash (@code{\}) @subentry @code{\"} escape sequence
@item \"
A literal double quote (should be used for string constants only).
This sequence is used when you want to write a string
constant that contains a double quote
(such as @code{"He said \"hi!\" to her."}).
Because the string is delimited by
double quotes, you need to escape any quote that is part of the string,
in order to tell @command{awk} to keep processing the rest of the string.
@end table
In @command{gawk}, a number of additional two-character sequences that begin
with a backslash have special meaning in regexps.
@xref{GNU Regexp Operators}.
In a regexp, a backslash before any character that is not in the previous list
and not listed in
@ref{GNU Regexp Operators}
means that the next character should be taken literally, even if it would
normally be a regexp operator. For example, @code{/a\+b/} matches the three
characters @samp{a+b}.
@cindex backslash (@code{\}) @subentry in escape sequences
@cindex @code{\} (backslash) @subentry in escape sequences
@cindex portability
For complete portability, do not use a backslash before any character not
shown in the previous list or that is not an operator.
@c 11/2014: Moved so as to not stack sidebars
@cindex sidebar @subentry Backslash Before Regular Characters
@ifdocbook
@docbook
<sidebar><title>Backslash Before Regular Characters</title>
@end docbook
@cindex portability @subentry backslash in escape sequences
@cindex POSIX @command{awk} @subentry backslashes in string constants
@cindex backslash (@code{\}) @subentry in escape sequences @subentry POSIX and
@cindex @code{\} (backslash) @subentry in escape sequences @subentry POSIX and
@cindex troubleshooting @subentry backslash before nonspecial character
If you place a backslash in a string constant before something that is
not one of the characters previously listed, POSIX @command{awk} purposely
leaves what happens as undefined. There are two choices:
@c @cindex automatic warnings
@c @cindex warnings, automatic
@cindex Brian Kernighan's @command{awk}
@table @asis
@item Strip the backslash out
This is what BWK @command{awk} and @command{gawk} both do.
For example, @code{"a\qc"} is the same as @code{"aqc"}.
(Because this is such an easy bug both to introduce and to miss,
@command{gawk} warns you about it.)
Consider @samp{FS = @w{"[ \t]+\|[ \t]+"}} to use vertical bars
surrounded by whitespace as the field separator. There should be
two backslashes in the string: @samp{FS = @w{"[ \t]+\\|[ \t]+"}}.)
@c I did this! This is why I added the warning.
@cindex @command{gawk} @subentry escape sequences
@cindex @command{gawk} @subentry escape sequences @seealso{backslash}
@cindex Unix @command{awk} @subentry backslashes in escape sequences
@cindex @command{mawk} utility
@item Leave the backslash alone
Some other @command{awk} implementations do this.
In such implementations, typing @code{"a\qc"} is the same as typing
@code{"a\\qc"}.
@end table
@docbook
</sidebar>
@end docbook
@end ifdocbook
@ifnotdocbook
@cartouche
@center @b{Backslash Before Regular Characters}
@cindex portability @subentry backslash in escape sequences
@cindex POSIX @command{awk} @subentry backslashes in string constants
@cindex backslash (@code{\}) @subentry in escape sequences @subentry POSIX and
@cindex @code{\} (backslash) @subentry in escape sequences @subentry POSIX and
@cindex troubleshooting @subentry backslash before nonspecial character
If you place a backslash in a string constant before something that is
not one of the characters previously listed, POSIX @command{awk} purposely
leaves what happens as undefined. There are two choices:
@c @cindex automatic warnings
@c @cindex warnings, automatic
@cindex Brian Kernighan's @command{awk}
@table @asis
@item Strip the backslash out
This is what BWK @command{awk} and @command{gawk} both do.
For example, @code{"a\qc"} is the same as @code{"aqc"}.
(Because this is such an easy bug both to introduce and to miss,
@command{gawk} warns you about it.)
Consider @samp{FS = @w{"[ \t]+\|[ \t]+"}} to use vertical bars
surrounded by whitespace as the field separator. There should be
two backslashes in the string: @samp{FS = @w{"[ \t]+\\|[ \t]+"}}.)
@c I did this! This is why I added the warning.
@cindex @command{gawk} @subentry escape sequences
@cindex @command{gawk} @subentry escape sequences @seealso{backslash}
@cindex Unix @command{awk} @subentry backslashes in escape sequences
@cindex @command{mawk} utility
@item Leave the backslash alone
Some other @command{awk} implementations do this.
In such implementations, typing @code{"a\qc"} is the same as typing
@code{"a\\qc"}.
@end table
@end cartouche
@end ifnotdocbook
To summarize:
@itemize @value{BULLET}
@item
The escape sequences in the preceding list are always processed first,
for both string constants and regexp constants. This happens very early,
as soon as @command{awk} reads your program.
@item
@command{gawk} processes both regexp constants and dynamic regexps
(@pxref{Computed Regexps}),
for the special operators listed in
@ref{GNU Regexp Operators}.
@item
A backslash before any other character means to treat that character
literally.
@end itemize
@cindex sidebar @subentry Escape Sequences for Metacharacters
@ifdocbook
@docbook
<sidebar><title>Escape Sequences for Metacharacters</title>
@end docbook
@cindex metacharacters @subentry escape sequences for
Suppose you use an octal or hexadecimal
escape to represent a regexp metacharacter.
(See @ref{Regexp Operators}.)
Does @command{awk} treat the character as a literal character or as a regexp
operator?
@cindex dark corner @subentry escape sequences @subentry for metacharacters
Historically, such characters were taken literally.
@value{DARKCORNER}
However, the POSIX standard indicates that they should be treated
as real metacharacters, which is what @command{gawk} does.
In compatibility mode (@pxref{Options}),
@command{gawk} treats the characters represented by octal and hexadecimal
escape sequences literally when used in regexp constants. Thus,
@code{/a\52b/} is equivalent to @code{/a\*b/}.
@docbook
</sidebar>
@end docbook
@end ifdocbook
@ifnotdocbook
@cartouche
@center @b{Escape Sequences for Metacharacters}
@cindex metacharacters @subentry escape sequences for
Suppose you use an octal or hexadecimal
escape to represent a regexp metacharacter.
(See @ref{Regexp Operators}.)
Does @command{awk} treat the character as a literal character or as a regexp
operator?
@cindex dark corner @subentry escape sequences @subentry for metacharacters
Historically, such characters were taken literally.
@value{DARKCORNER}
However, the POSIX standard indicates that they should be treated
as real metacharacters, which is what @command{gawk} does.
In compatibility mode (@pxref{Options}),
@command{gawk} treats the characters represented by octal and hexadecimal
escape sequences literally when used in regexp constants. Thus,
@code{/a\52b/} is equivalent to @code{/a\*b/}.
@end cartouche
@end ifnotdocbook
@node Regexp Operators
@section Regular Expression Operators
@cindex regular expressions @subentry operators
@cindex metacharacters @subentry in regular expressions
You can combine regular expressions with special characters,
called @dfn{regular expression operators} or @dfn{metacharacters}, to
increase the power and versatility of regular expressions.
@menu
* Regexp Operator Details:: The actual details.
* Interval Expressions:: Notes on interval expressions.
@end menu
@node Regexp Operator Details
@subsection Regexp Operators in @command{awk}
The escape sequences described
@ifnotinfo
earlier
@end ifnotinfo
in @ref{Escape Sequences}
are valid inside a regexp. They are introduced by a @samp{\} and
are recognized and converted into corresponding real characters as
the very first step in processing regexps.
Here is a list of metacharacters. All characters that are not escape
sequences and that are not listed here stand for themselves:
@c Use @asis so the docbook comes out ok. Sigh.
@table @asis
@cindex backslash (@code{\}) @subentry regexp operator
@cindex @code{\} (backslash) @subentry regexp operator
@item @code{\}
This suppresses the special meaning of a character when
matching. For example, @samp{\$}
matches the character @samp{$}.
@cindex regular expressions @subentry anchors in
@cindex Texinfo @subentry chapter beginnings in files
@cindex @code{^} (caret) @subentry regexp operator
@cindex caret (@code{^}) @subentry regexp operator
@item @code{^}
This matches the beginning of a string. @samp{^@@chapter}
matches @samp{@@chapter} at the beginning of a string,
for example, and can be used
to identify chapter beginnings in Texinfo source files.
The @samp{^} is known as an @dfn{anchor}, because it anchors the pattern to
match only at the beginning of the string.
It is important to realize that @samp{^} does not match the beginning of
a line (the point right after a @samp{\n} newline character) embedded in a string.
The condition is not true in the following example:
@example
if ("line1\nLINE 2" ~ /^L/) @dots{}
@end example
@cindex @code{$} (dollar sign) @subentry regexp operator
@cindex dollar sign (@code{$}) @subentry regexp operator
@item @code{$}
This is similar to @samp{^}, but it matches only at the end of a string.
For example, @samp{p$}
matches a record that ends with a @samp{p}. The @samp{$} is an anchor
and does not match the end of a line
(the point right before a @samp{\n} newline character)
embedded in a string.
The condition in the following example is not true:
@example
if ("line1\nLINE 2" ~ /1$/) @dots{}
@end example
@cindex @code{.} (period), regexp operator
@cindex period (@code{.}), regexp operator
@item @code{.} (period)
This matches any single character,
@emph{including} the newline character. For example, @samp{.P}
matches any single character followed by a @samp{P} in a string. Using
concatenation, we can make a regular expression such as @samp{U.A}, which
matches any three-character sequence that begins with @samp{U} and ends
with @samp{A}.
@cindex POSIX mode
@cindex POSIX @command{awk} @subentry period (@code{.}), using
In strict POSIX mode (@pxref{Options}),
@samp{.} does not match the @sc{nul}
character, which is a character with all bits equal to zero.
Otherwise, @sc{nul} is just another character. Other versions of @command{awk}
may not be able to match the @sc{nul} character.
@cindex @code{[]} (square brackets), regexp operator
@cindex square brackets (@code{[]}), regexp operator
@cindex bracket expressions
@cindex character sets (in regular expressions) @seeentry{bracket expressions}
@cindex character lists @seeentry{bracket expressions}
@cindex character classes @seeentry{bracket expressions}
@item @code{[}@dots{}@code{]}
This is called a @dfn{bracket expression}.@footnote{In other literature,
you may see a bracket expression referred to as either a
@dfn{character set}, a @dfn{character class}, or a @dfn{character list}.}
It matches any @emph{one} of the characters that are enclosed in
the square brackets. For example, @samp{[MVX]} matches any one of
the characters @samp{M}, @samp{V}, or @samp{X} in a string. A full
discussion of what can be inside the square brackets of a bracket expression
is given in
@ref{Bracket Expressions}.
@cindex bracket expressions @subentry complemented
@item @code{[^}@dots{}@code{]}
This is a @dfn{complemented bracket expression}. The first character after
the @samp{[} @emph{must} be a @samp{^}. It matches any characters
@emph{except} those in the square brackets. For example, @samp{[^awk]}
matches any character that is not an @samp{a}, @samp{w},
or @samp{k}.
@cindex @code{|} (vertical bar)
@cindex vertical bar (@code{|})
@item @code{|}
This is the @dfn{alternation operator} and it is used to specify
alternatives. The @samp{|} has the lowest precedence of all the regular
expression operators. For example, @samp{^P|[aeiouy]} matches any string
that matches either @samp{^P} or @samp{[aeiouy]}. This means it matches
any string that starts with @samp{P} or contains (anywhere within it)
a lowercase English vowel.
The alternation applies to the largest possible regexps on either side.
@cindex @code{()} (parentheses) @subentry regexp operator
@cindex parentheses @code{()} @subentry regexp operator
@item @code{(}@dots{}@code{)}
Parentheses are used for grouping in regular expressions, as in
arithmetic. They can be used to concatenate regular expressions
containing the alternation operator, @samp{|}. For example,
@samp{@@(samp|code)\@{[^@}]+\@}} matches both @samp{@@code@{foo@}} and
@samp{@@samp@{bar@}}.
(These are Texinfo formatting control sequences. The @samp{+} is
explained further on in this list.)
The left or opening parenthesis is always a metacharacter; to match
one literally, precede it with a backslash. However, the right or
closing parenthesis is only special when paired with a left parenthesis;
an unpaired right parenthesis is (silently) treated as a regular character.
@cindex @code{*} (asterisk) @subentry @code{*} operator @subentry as regexp operator
@cindex asterisk (@code{*}) @subentry @code{*} operator @subentry as regexp operator
@item @code{*}
This symbol means that the preceding regular expression should be
repeated as many times as necessary to find a match. For example, @samp{ph*}
applies the @samp{*} symbol to the preceding @samp{h} and looks for matches
of one @samp{p} followed by any number of @samp{h}s. This also matches
just @samp{p} if no @samp{h}s are present.
There are two subtle points to understand about how @samp{*} works.
First, the @samp{*} applies only to the single preceding regular expression
component (e.g., in @samp{ph*}, it applies just to the @samp{h}).
To cause @samp{*} to apply to a larger subexpression, use parentheses:
@samp{(ph)*} matches @samp{ph}, @samp{phph}, @samp{phphph}, and so on.
Second, @samp{*} finds as many repetitions as possible. If the text
to be matched is @samp{phhhhhhhhhhhhhhooey}, @samp{ph*} matches all of
the @samp{h}s.
@cindex @code{+} (plus sign) @subentry regexp operator
@cindex plus sign (@code{+}) @subentry regexp operator
@item @code{+}
This symbol is similar to @samp{*}, except that the preceding expression must be
matched at least once. This means that @samp{wh+y}
would match @samp{why} and @samp{whhy}, but not @samp{wy}, whereas
@samp{wh*y} would match all three.
@cindex @code{?} (question mark) @subentry regexp operator
@cindex question mark (@code{?}) @subentry regexp operator
@item @code{?}
This symbol is similar to @samp{*}, except that the preceding expression can be
matched either once or not at all. For example, @samp{fe?d}
matches @samp{fed} and @samp{fd}, but nothing else.
@cindex @code{@{@}} (braces) @subentry regexp operator
@cindex braces (@code{@{@}}) @subentry regexp operator
@cindex interval expressions, regexp operator
@item @code{@{}@var{n}@code{@}}
@itemx @code{@{}@var{n}@code{,@}}
@itemx @code{@{}@var{n}@code{,}@var{m}@code{@}}
One or two numbers inside braces denote an @dfn{interval expression}.
If there is one number in the braces, the preceding regexp is repeated
@var{n} times.
If there are two numbers separated by a comma, the preceding regexp is
repeated @var{n} to @var{m} times.
If there is one number followed by a comma, then the preceding regexp
is repeated at least @var{n} times:
@table @code
@item wh@{3@}y
Matches @samp{whhhy}, but not @samp{why} or @samp{whhhhy}.
@item wh@{3,5@}y
Matches @samp{whhhy}, @samp{whhhhy}, or @samp{whhhhhy} only.
@item wh@{2,@}y
Matches @samp{whhy}, @samp{whhhy}, and so on.
@end table
@end table
@cindex precedence @subentry regexp operators
@cindex regular expressions @subentry operators @subentry precedence of
In regular expressions, the @samp{*}, @samp{+}, and @samp{?} operators,
as well as the braces @samp{@{} and @samp{@}},
have
the highest precedence, followed by concatenation, and finally by @samp{|}.
As in arithmetic, parentheses can change how operators are grouped.
@cindex POSIX @command{awk} @subentry regular expressions and
@cindex @command{gawk} @subentry regular expressions @subentry precedence
In POSIX @command{awk} and @command{gawk}, the @samp{*}, @samp{+}, and
@samp{?} operators stand for themselves when there is nothing in the
regexp that precedes them. For example, @code{/+/} matches a literal
plus sign. However, many other versions of @command{awk} treat such a
usage as a syntax error.
@node Interval Expressions
@subsection Some Notes On Interval Expressions
@cindex POSIX @command{awk} @subentry interval expressions in
Interval expressions were not traditionally available in @command{awk}.
They were added as part of the POSIX standard to make @command{awk}
and @command{egrep} consistent with each other.
@cindex @command{gawk} @subentry interval expressions and
Initially, because old programs may use @samp{@{} and @samp{@}} in regexp
constants,
@command{gawk} did @emph{not} match interval expressions
in regexps.
However, beginning with @value{PVERSION} 4.0,
@command{gawk} does match interval expressions by default.
This is because compatibility with POSIX has become more
important to most @command{gawk} users than compatibility with
old programs.
For programs that use @samp{@{} and @samp{@}} in regexp constants,
it is good practice to always escape them with a backslash. Then the
regexp constants are valid and work the way you want them to, using
any version of @command{awk}.@footnote{Use two backslashes if you're
using a string constant with a regexp operator or function.}
Finally, when @samp{@{} and @samp{@}} appear in regexp constants
in a way that cannot be interpreted as an interval expression
(such as @code{/q@{a@}/}), then they stand for themselves.
As mentioned, interval expressions were not traditionally available
in @command{awk}. In March of 2019, BWK @command{awk} (finally) acquired them.
Nonetheless, because they were not available for
so many decades, @command{gawk} continues to not supply them
when in compatibility mode (@pxref{Options}).
@node Bracket Expressions
@section Using Bracket Expressions
@cindex bracket expressions
@cindex bracket expressions @subentry range expressions
@cindex range expressions (regexps)
@cindex bracket expressions @subentry character lists
As mentioned earlier, a bracket expression matches any character among
those listed between the opening and closing square brackets.
Within a bracket expression, a @dfn{range expression} consists of two
characters separated by a hyphen. It matches any single character that
sorts between the two characters, based upon the system's native character
set. For example, @samp{[0-9]} is equivalent to @samp{[0123456789]}.
(See @ref{Ranges and Locales} for an explanation of how the POSIX
standard and @command{gawk} have changed over time. This is mainly
of historical interest.)
With the increasing popularity of the
@uref{http://www.unicode.org, Unicode character standard},
there is an additional wrinkle to consider. Octal and hexadecimal
escape sequences inside bracket expressions are taken to represent
only single-byte characters (characters whose values fit within
the range 0--256). To match a range of characters where the endpoints
of the range are larger than 256, enter the multibyte encodings of
the characters directly.
@cindex @code{\} (backslash) @subentry in bracket expressions
@cindex backslash (@code{\}) @subentry in bracket expressions
@cindex @code{^} (caret) @subentry in bracket expressions
@cindex caret (@code{^}) @subentry in bracket expressions
@cindex @code{-} (hyphen) @subentry in bracket expressions
@cindex hyphen (@code{-}) @subentry in bracket expressions
To include one of the characters @samp{\}, @samp{]}, @samp{-}, or @samp{^} in a
bracket expression, put a @samp{\} in front of it. For example:
@example
[d\]]
@end example
@noindent
matches either @samp{d} or @samp{]}.
Additionally, if you place @samp{]} right after the opening
@samp{[}, the closing bracket is treated as one of the
characters to be matched.
@cindex POSIX @command{awk} @subentry bracket expressions and
@cindex Extended Regular Expressions (EREs)
@cindex EREs (Extended Regular Expressions)
@cindex @command{egrep} utility
The treatment of @samp{\} in bracket expressions
is compatible with other @command{awk}
implementations and is also mandated by POSIX.
The regular expressions in @command{awk} are a superset
of the POSIX specification for Extended Regular Expressions (EREs).
POSIX EREs are based on the regular expressions accepted by the
traditional @command{egrep} utility.
@cindex bracket expressions @subentry character classes
@cindex POSIX @command{awk} @subentry bracket expressions and @subentry character classes
@dfn{Character classes} are a feature introduced in the POSIX standard.
A character class is a special notation for describing
lists of characters that have a specific attribute, but the
actual characters can vary from country to country and/or
from character set to character set. For example, the notion of what
is an alphabetic character differs between the United States and France.
A character class is only valid in a regexp @emph{inside} the
brackets of a bracket expression. Character classes consist of @samp{[:},
a keyword denoting the class, and @samp{:]}.
@ref{table-char-classes} lists the character classes defined by the
POSIX standard.
@float Table,table-char-classes
@caption{POSIX character classes}
@multitable @columnfractions .15 .85
@headitem Class @tab Meaning
@item @code{[:alnum:]} @tab Alphanumeric characters
@item @code{[:alpha:]} @tab Alphabetic characters
@item @code{[:blank:]} @tab Space and TAB characters
@item @code{[:cntrl:]} @tab Control characters
@item @code{[:digit:]} @tab Numeric characters
@item @code{[:graph:]} @tab Characters that are both printable and visible
(a space is printable but not visible, whereas an @samp{a} is both)
@item @code{[:lower:]} @tab Lowercase alphabetic characters
@item @code{[:print:]} @tab Printable characters (characters that are not control characters)
@item @code{[:punct:]} @tab Punctuation characters (characters that are not letters, digits,
control characters, or space characters)
@item @code{[:space:]} @tab Space characters (these are: space, TAB, newline, carriage return, formfeed and vertical tab)
@item @code{[:upper:]} @tab Uppercase alphabetic characters
@item @code{[:xdigit:]} @tab Characters that are hexadecimal digits
@end multitable
@end float
For example, before the POSIX standard, you had to write @code{/[A-Za-z0-9]/}
to match alphanumeric characters. If your
character set had other alphabetic characters in it, this would not
match them.
With the POSIX character classes, you can write
@code{/[[:alnum:]]/} to match the alphabetic
and numeric characters in your character set.
@ignore
From eliz@gnu.org Fri Feb 15 03:38:41 2019
Date: Fri, 15 Feb 2019 12:38:23 +0200
From: Eli Zaretskii <eliz@gnu.org>
To: arnold@skeeve.com
CC: pengyu.ut@gmail.com, bug-gawk@gnu.org
Subject: Re: [bug-gawk] Does gawk character classes follow this?
> From: arnold@skeeve.com
> Date: Fri, 15 Feb 2019 03:01:34 -0700
> Cc: pengyu.ut@gmail.com, bug-gawk@gnu.org
>
> I get the feeling that there's something really bothering you, but
> I don't understand what.
>
> Can you clarify, please?
I thought I already did: we cannot be expected to provide a definitive
description of what the named classes stand for, because the answer
depends on various factors out of our control.
@end ignore
@c Thanks to
@c Date: Tue, 01 Jul 2014 07:39:51 +0200
@c From: Hermann Peifer <peifer@gmx.eu>
@cindex ASCII
Some utilities that match regular expressions provide a nonstandard
@samp{[:ascii:]} character class; @command{awk} does not. However, you
can simulate such a construct using @samp{[\x00-\x7F]}. This matches
all values numerically between zero and 127, which is the defined
range of the ASCII character set. Use a complemented character list
(@samp{[^\x00-\x7F]}) to match any single-byte characters that are not
in the ASCII range.
@quotation NOTE
Some older versions of Unix @command{awk}
treat @code{[:blank:]} like @code{[:space:]}, incorrectly matching
more characters than they should. Caveat Emptor.
@end quotation
@cindex bracket expressions @subentry collating elements
@cindex bracket expressions @subentry non-ASCII
@cindex collating elements
Two additional special sequences can appear in bracket expressions.
These apply to non-ASCII character sets, which can have single symbols
(called @dfn{collating elements}) that are represented with more than one
character. They can also have several characters that are equivalent for
@dfn{collating}, or sorting, purposes. (For example, in French, a plain ``e''
and a grave-accented ``@`e'' are equivalent.)
These sequences are:
@table @asis
@cindex bracket expressions @subentry collating symbols
@cindex collating symbols
@item Collating symbols
Multicharacter collating elements enclosed between
@samp{[.} and @samp{.]}. For example, if @samp{ch} is a collating element,
then @samp{[[.ch.]]} is a regexp that matches this collating element, whereas
@samp{[ch]} is a regexp that matches either @samp{c} or @samp{h}.
@cindex bracket expressions @subentry equivalence classes
@item Equivalence classes
Locale-specific names for a list of
characters that are equal. The name is enclosed between
@samp{[=} and @samp{=]}.
For example, the name @samp{e} might be used to represent all of
``e,'' ``@^e,'' ``@`e,'' and ``@'e.'' In this case, @samp{[[=e=]]} is a regexp
that matches any of @samp{e}, @samp{@^e}, @samp{@'e}, or @samp{@`e}.
@end table
These features are very valuable in non-English-speaking locales.
@cindex internationalization @subentry localization @subentry character classes
@cindex @command{gawk} @subentry character classes and
@cindex POSIX @command{awk} @subentry bracket expressions and @subentry character classes
@quotation CAUTION
The library functions that @command{gawk} uses for regular
expression matching currently recognize only POSIX character classes;
they do not recognize collating symbols or equivalence classes.
@end quotation
@c maybe one day ...
Inside a bracket expression, an opening bracket (@samp{[}) that does
not start a character class, collating element or equivalence class is
taken literally. This is also true of @samp{.} and @samp{*}.
@node Leftmost Longest
@section How Much Text Matches?
@cindex regular expressions @subentry leftmost longest match
@c @cindex matching, leftmost longest
Consider the following:
@example
echo aaaabcd | awk '@{ sub(/a+/, "<A>"); print @}'
@end example
This example uses the @code{sub()} function to make a change to the input
record. (@code{sub()} replaces the first instance of any text matched
by the first argument with the string provided as the second argument;
@pxref{String Functions}.) Here, the regexp @code{/a+/} indicates ``one
or more @samp{a} characters,'' and the replacement text is @samp{<A>}.
The input contains four @samp{a} characters.
@command{awk} (and POSIX) regular expressions always match
the leftmost, @emph{longest} sequence of input characters that can
match. Thus, all four @samp{a} characters are
replaced with @samp{<A>} in this example:
@example
$ @kbd{echo aaaabcd | awk '@{ sub(/a+/, "<A>"); print @}'}
@print{} <A>bcd
@end example
For simple match/no-match tests, this is not so important. But when doing
text matching and substitutions with the @code{match()}, @code{sub()}, @code{gsub()},
and @code{gensub()} functions, it is very important.
@ifinfo
@xref{String Functions},
for more information on these functions.
@end ifinfo
Understanding this principle is also important for regexp-based record
and field splitting (@pxref{Records},
and also @pxref{Field Separators}).
@node Computed Regexps
@section Using Dynamic Regexps
@cindex regular expressions @subentry computed
@cindex regular expressions @subentry dynamic
@cindex @code{~} (tilde), @code{~} operator
@cindex tilde (@code{~}), @code{~} operator
@cindex @code{!} (exclamation point) @subentry @code{!~} operator
@cindex exclamation point (@code{!}) @subentry @code{!~} operator
@c @cindex operators, @code{~}
@c @cindex operators, @code{!~}
The righthand side of a @samp{~} or @samp{!~} operator need not be a
regexp constant (i.e., a string of characters between slashes). It may
be any expression. The expression is evaluated and converted to a string
if necessary; the contents of the string are then used as the
regexp. A regexp computed in this way is called a @dfn{dynamic
regexp} or a @dfn{computed regexp}:
@example
BEGIN @{ digits_regexp = "[[:digit:]]+" @}
$0 ~ digits_regexp @{ print @}
@end example
@noindent
This sets @code{digits_regexp} to a regexp that describes one or more digits,
and tests whether the input record matches this regexp.
@quotation NOTE
When using the @samp{~} and @samp{!~}
operators, be aware that there is a difference between a regexp constant
enclosed in slashes and a string constant enclosed in double quotes.
If you are going to use a string constant, you have to understand that
the string is, in essence, scanned @emph{twice}: the first time when
@command{awk} reads your program, and the second time when it goes to
match the string on the lefthand side of the operator with the pattern
on the right. This is true of any string-valued expression (such as
@code{digits_regexp}, shown in the previous example), not just string constants.
@end quotation
@cindex regexp constants @subentry slashes vs.@: quotes
@cindex @code{\} (backslash) @subentry in regexp constants
@cindex backslash (@code{\}) @subentry in regexp constants
@cindex @code{"} (double quote) @subentry in regexp constants
@cindex double quote (@code{"}) @subentry in regexp constants
What difference does it make if the string is
scanned twice? The answer has to do with escape sequences, and particularly
with backslashes. To get a backslash into a regular expression inside a
string, you have to type two backslashes.
For example, @code{/\*/} is a regexp constant for a literal @samp{*}.
Only one backslash is needed. To do the same thing with a string,
you have to type @code{"\\*"}. The first backslash escapes the
second one so that the string actually contains the
two characters @samp{\} and @samp{*}.
@cindex troubleshooting @subentry regexp constants vs.@: string constants
@cindex regexp constants @subentry vs.@: string constants
@cindex string @subentry constants @subentry vs.@: regexp constants
Given that you can use both regexp and string constants to describe
regular expressions, which should you use? The answer is ``regexp
constants,'' for several reasons:
@itemize @value{BULLET}
@item
String constants are more complicated to write and
more difficult to read. Using regexp constants makes your programs
less error-prone. Not understanding the difference between the two
kinds of constants is a common source of errors.
@item
It is more efficient to use regexp constants. @command{awk} can note
that you have supplied a regexp and store it internally in a form that
makes pattern matching more efficient. When using a string constant,
@command{awk} must first convert the string into this internal form and
then perform the pattern matching.
@item
Using regexp constants is better form; it shows clearly that you
intend a regexp match.
@end itemize
@cindex sidebar @subentry Using @code{\n} in Bracket Expressions of Dynamic Regexps
@ifdocbook
@docbook
<sidebar><title>Using @code{\n} in Bracket Expressions of Dynamic Regexps</title>
@end docbook
@cindex regular expressions @subentry dynamic @subentry with embedded newlines
@cindex newlines @subentry in dynamic regexps
Some older versions of @command{awk} do not allow the newline
character to be used inside a bracket expression for a dynamic regexp:
@example
$ @kbd{awk '$0 ~ "[ \t\n]"'}
@error{} awk: newline in character class [
@error{} ]...
@error{} source line number 1
@error{} context is
@error{} $0 ~ "[ >>> \t\n]" <<<
@end example
@cindex newlines @subentry in regexp constants
But a newline in a regexp constant works with no problem:
@example
$ @kbd{awk '$0 ~ /[ \t\n]/'}
@kbd{here is a sample line}
@print{} here is a sample line
@kbd{Ctrl-d}
@end example
@command{gawk} does not have this problem, and it isn't likely to
occur often in practice, but it's worth noting for future reference.
@docbook
</sidebar>
@end docbook
@end ifdocbook
@ifnotdocbook
@cartouche
@center @b{Using @code{\n} in Bracket Expressions of Dynamic Regexps}
@cindex regular expressions @subentry dynamic @subentry with embedded newlines
@cindex newlines @subentry in dynamic regexps
Some older versions of @command{awk} do not allow the newline
character to be used inside a bracket expression for a dynamic regexp:
@example
$ @kbd{awk '$0 ~ "[ \t\n]"'}
@error{} awk: newline in character class [
@error{} ]...
@error{} source line number 1
@error{} context is
@error{} $0 ~ "[ >>> \t\n]" <<<
@end example
@cindex newlines @subentry in regexp constants
But a newline in a regexp constant works with no problem:
@example
$ @kbd{awk '$0 ~ /[ \t\n]/'}
@kbd{here is a sample line}
@print{} here is a sample line
@kbd{Ctrl-d}
@end example
@command{gawk} does not have this problem, and it isn't likely to
occur often in practice, but it's worth noting for future reference.
@end cartouche
@end ifnotdocbook
@node GNU Regexp Operators
@section @command{gawk}-Specific Regexp Operators
@c This section adapted (long ago) from the regex-0.12 manual
@cindex regular expressions @subentry operators @subentry @command{gawk}
@cindex @command{gawk} @subentry regular expressions @subentry operators
@cindex operators @subentry GNU-specific
@cindex regular expressions @subentry operators @subentry for words
@cindex word, regexp definition of
GNU software that deals with regular expressions provides a number of
additional regexp operators. These operators are described in this
@value{SECTION} and are specific to @command{gawk};
they are not available in other @command{awk} implementations.
Most of the additional operators deal with word matching.
For our purposes, a @dfn{word} is a sequence of one or more letters, digits,
or underscores (@samp{_}):
@table @code
@c @cindex operators, @code{\s} (@command{gawk})
@cindex backslash (@code{\}) @subentry @code{\s} operator (@command{gawk})
@cindex @code{\} (backslash) @subentry @code{\s} operator (@command{gawk})
@item \s
Matches any space character as defined by the current locale.
Think of it as shorthand for
@w{@samp{[[:space:]]}}.
@c @cindex operators, @code{\S} (@command{gawk})
@cindex backslash (@code{\}) @subentry @code{\S} operator (@command{gawk})
@cindex @code{\} (backslash) @subentry @code{\S} operator (@command{gawk})
@item \S
Matches any character that is not a space, as defined by the current locale.
Think of it as shorthand for
@w{@samp{[^[:space:]]}}.
@c @cindex operators, @code{\w} (@command{gawk})
@cindex backslash (@code{\}) @subentry @code{\w} operator (@command{gawk})
@cindex @code{\} (backslash) @subentry @code{\w} operator (@command{gawk})
@item \w
Matches any word-constituent character---that is, it matches any
letter, digit, or underscore. Think of it as shorthand for
@w{@samp{[[:alnum:]_]}}.
@c @cindex operators, @code{\W} (@command{gawk})
@cindex backslash (@code{\}) @subentry @code{\W} operator (@command{gawk})
@cindex @code{\} (backslash) @subentry @code{\W} operator (@command{gawk})
@item \W
Matches any character that is not word-constituent.
Think of it as shorthand for
@w{@samp{[^[:alnum:]_]}}.
@c @cindex operators, @code{\<} (@command{gawk})
@cindex backslash (@code{\}) @subentry @code{\<} operator (@command{gawk})
@cindex @code{\} (backslash) @subentry @code{\<} operator (@command{gawk})
@item \<
Matches the empty string at the beginning of a word.
For example, @code{/\<away/} matches @samp{away} but not
@samp{stowaway}.
@c @cindex operators, @code{\>} (@command{gawk})
@cindex backslash (@code{\}) @subentry @code{\>} operator (@command{gawk})
@cindex @code{\} (backslash) @subentry @code{\>} operator (@command{gawk})
@item \>
Matches the empty string at the end of a word.
For example, @code{/stow\>/} matches @samp{stow} but not @samp{stowaway}.
@c @cindex operators, @code{\y} (@command{gawk})
@cindex backslash (@code{\}) @subentry @code{\y} operator (@command{gawk})
@cindex @code{\} (backslash) @subentry @code{\y} operator (@command{gawk})
@cindex word boundaries, matching
@item \y
Matches the empty string at either the beginning or the
end of a word (i.e., the word boundar@strong{y}). For example, @samp{\yballs?\y}
matches either @samp{ball} or @samp{balls}, as a separate word.
@c @cindex operators, @code{\B} (@command{gawk})
@cindex backslash (@code{\}) @subentry @code{\B} operator (@command{gawk})
@cindex @code{\} (backslash) @subentry @code{\B} operator (@command{gawk})
@item \B
Matches the empty string that occurs between two
word-constituent characters. For example,
@code{/\Brat\B/} matches @samp{crate}, but it does not match @samp{dirty rat}.
@samp{\B} is essentially the opposite of @samp{\y}.
@end table
@cindex buffers @subentry operators for
@cindex regular expressions @subentry operators @subentry for buffers
@cindex operators @subentry string-matching @subentry for buffers
There are two other operators that work on buffers. In Emacs, a
@dfn{buffer} is, naturally, an Emacs buffer.
Other GNU programs, including @command{gawk},
consider the entire string to match as the buffer.
The operators are:
@table @code
@item \`
@c @cindex operators, @code{\`} (@command{gawk})
@cindex backslash (@code{\}) @subentry @code{\`} operator (@command{gawk})
@cindex @code{\} (backslash) @subentry @code{\`} operator (@command{gawk})
Matches the empty string at the
beginning of a buffer (string)
@c @cindex operators, @code{\'} (@command{gawk})
@cindex backslash (@code{\}) @subentry @code{\'} operator (@command{gawk})
@cindex @code{\} (backslash) @subentry @code{\'} operator (@command{gawk})
@item \'
Matches the empty string at the
end of a buffer (string)
@end table
@cindex @code{^} (caret) @subentry regexp operator
@cindex caret (@code{^}) @subentry regexp operator
@cindex @code{?} (question mark) @subentry regexp operator
@cindex question mark (@code{?}) @subentry regexp operator
Because @samp{^} and @samp{$} always work in terms of the beginning
and end of strings, these operators don't add any new capabilities
for @command{awk}. They are provided for compatibility with other
GNU software.
@cindex @command{gawk} @subentry word-boundary operator
@cindex word-boundary operator (@command{gawk})
@cindex operators @subentry word-boundary (@command{gawk})
In other GNU software, the word-boundary operator is @samp{\b}. However,
that conflicts with the @command{awk} language's definition of @samp{\b}
as backspace, so @command{gawk} uses a different letter.
An alternative method would have been to require two backslashes in the
GNU operators, but this was deemed too confusing. The current
method of using @samp{\y} for the GNU @samp{\b} appears to be the
lesser of two evils.
@cindex regular expressions @subentry @command{gawk}, command-line options
@cindex @command{gawk} @subentry command-line options, regular expressions and
The various command-line options
(@pxref{Options})
control how @command{gawk} interprets characters in regexps:
@table @asis
@item No options
In the default case, @command{gawk} provides all the facilities of
POSIX regexps and the
@ifnotinfo
previously described
GNU regexp operators.
@end ifnotinfo
@ifnottex
@ifnotdocbook
GNU regexp operators described
in @ref{Regexp Operators}.
@end ifnotdocbook
@end ifnottex
@item @code{--posix}
Match only POSIX regexps; the GNU operators are not special
(e.g., @samp{\w} matches a literal @samp{w}). Interval expressions
are allowed.
@cindex Brian Kernighan's @command{awk}
@item @code{--traditional}
Match traditional Unix @command{awk} regexps. The GNU operators
are not special, and interval expressions are not available.
Because BWK @command{awk} supports them,
the POSIX character classes (@samp{[[:alnum:]]}, etc.) are available.
Characters described by octal and hexadecimal escape sequences are
treated literally, even if they represent regexp metacharacters.
@item @code{--re-interval}
Allow interval expressions in regexps, if @option{--traditional}
has been provided.
Otherwise, interval expressions are available by default.
@end table
@node Case-sensitivity
@section Case Sensitivity in Matching
@cindex regular expressions @subentry case sensitivity
@cindex case sensitivity @subentry regexps and
Case is normally significant in regular expressions, both when matching
ordinary characters (i.e., not metacharacters) and inside bracket
expressions. Thus, a @samp{w} in a regular expression matches only a lowercase
@samp{w} and not an uppercase @samp{W}.
The simplest way to do a case-independent match is to use a bracket
expression---for example, @samp{[Ww]}. However, this can be cumbersome if
you need to use it often, and it can make the regular expressions harder
to read. There are two alternatives that you might prefer.
One way to perform a case-insensitive match at a particular point in the
program is to convert the data to a single case, using the
@code{tolower()} or @code{toupper()} built-in string functions (which we
haven't discussed yet;
@pxref{String Functions}).
For example:
@example
tolower($1) ~ /foo/ @{ @dots{} @}
@end example
@noindent
converts the first field to lowercase before matching against it.
This works in any POSIX-compliant @command{awk}.
@cindex @command{gawk} @subentry regular expressions @subentry case sensitivity
@cindex case sensitivity @subentry @command{gawk}
@cindex differences in @command{awk} and @command{gawk} @subentry regular expressions
@cindex @code{~} (tilde), @code{~} operator
@cindex tilde (@code{~}), @code{~} operator
@cindex @code{!} (exclamation point) @subentry @code{!~} operator
@cindex exclamation point (@code{!}) @subentry @code{!~} operator
@cindex @code{IGNORECASE} variable @subentry with @code{~} and @code{!~} operators
@cindex @command{gawk} @subentry @code{IGNORECASE} variable in
@c @cindex variables, @code{IGNORECASE}
Another method, specific to @command{gawk}, is to set the variable
@code{IGNORECASE} to a nonzero value (@pxref{Built-in Variables}).
When @code{IGNORECASE} is not zero, @emph{all} regexp and string
operations ignore case.
Changing the value of @code{IGNORECASE} dynamically controls the
case sensitivity of the program as it runs. Case is significant by
default because @code{IGNORECASE} (like most variables) is initialized
to zero:
@example
x = "aB"
if (x ~ /ab/) @dots{} # this test will fail
IGNORECASE = 1
if (x ~ /ab/) @dots{} # now it will succeed
@end example
In general, you cannot use @code{IGNORECASE} to make certain rules
case insensitive and other rules case sensitive, as there is no
straightforward way
to set @code{IGNORECASE} just for the pattern of
a particular rule.@footnote{Experienced C and C++ programmers will note
that it is possible, using something like
@samp{IGNORECASE = 1 && /foObAr/ @{ @dots{} @}}
and
@samp{IGNORECASE = 0 || /foobar/ @{ @dots{} @}}.
However, this is somewhat obscure and we don't recommend it.}
To do this, use either bracket expressions or @code{tolower()}. However, one
thing you can do with @code{IGNORECASE} only is dynamically turn
case sensitivity on or off for all the rules at once.
@code{IGNORECASE} can be set on the command line or in a @code{BEGIN} rule
(@pxref{Other Arguments}; also
@pxref{Using BEGIN/END}).
Setting @code{IGNORECASE} from the command line is a way to make
a program case insensitive without having to edit it.
@c @cindex ISO 8859-1
@c @cindex ISO Latin-1
In multibyte locales, the equivalences between upper- and lowercase
characters are tested based on the wide-character values of the locale's
character set. Prior to @value{PVERSION} 5.0, single-byte characters were
tested based on the ISO-8859-1 (ISO Latin-1) character set. However, as
of @value{PVERSION} 5.0, single-byte characters are also tested based on
the values of the locale's character set.@footnote{If you don't understand
this, don't worry about it; it just means that @command{gawk} does the
right thing.}
The value of @code{IGNORECASE} has no effect if @command{gawk} is in
compatibility mode (@pxref{Options}).
Case is always significant in compatibility mode.
@node Regexp Summary
@section Summary
@itemize @value{BULLET}
@item
Regular expressions describe sets of strings to be matched.
In @command{awk}, regular expression constants are written enclosed
between slashes: @code{/}@dots{}@code{/}.
@item
Regexp constants may be used standalone in patterns and
in conditional expressions, or as part of matching expressions
using the @samp{~} and @samp{!~} operators.
@item
Escape sequences let you represent nonprintable characters and
also let you represent regexp metacharacters as literal characters
to be matched.
@item
Regexp operators provide grouping, alternation, and repetition.
@item
Bracket expressions give you a shorthand for specifying sets
of characters that can match at a particular point in a regexp.
Within bracket expressions, POSIX character classes let you specify
certain groups of characters in a locale-independent fashion.
@item
Regular expressions match the leftmost longest text in the string being
matched. This matters for cases where you need to know the extent of
the match, such as for text substitution and when the record separator
is a regexp.
@item
Matching expressions may use dynamic regexps (i.e., string values
treated as regular expressions).
@item
@command{gawk}'s @code{IGNORECASE} variable lets you control the
case sensitivity of regexp matching. In other @command{awk}
versions, use @code{tolower()} or @code{toupper()}.
@end itemize
@node Reading Files
@chapter Reading Input Files
@cindex reading input files
@cindex input files @subentry reading
@cindex input files
@cindex @code{FILENAME} variable
In the typical @command{awk} program,
@command{awk} reads all input either from the
standard input (by default, this is the keyboard, but often it is a pipe from another
command) or from files whose names you specify on the @command{awk}
command line. If you specify input files, @command{awk} reads them
in order, processing all the data from one before going on to the next.
The name of the current input file can be found in the predefined variable
@code{FILENAME}
(@pxref{Built-in Variables}).
@cindex records
@cindex fields
The input is read in units called @dfn{records}, and is processed by the
rules of your program one record at a time.
By default, each record is one line. Each
record is automatically split into chunks called @dfn{fields}.
This makes it more convenient for programs to work on the parts of a record.
@cindex @code{getline} command
On rare occasions, you may need to use the @code{getline} command.
The @code{getline} command is valuable both because it
can do explicit input from any number of files, and because the files
used with it do not have to be named on the @command{awk} command line
(@pxref{Getline}).
@menu
* Records:: Controlling how data is split into records.
* Fields:: An introduction to fields.
* Nonconstant Fields:: Nonconstant Field Numbers.
* Changing Fields:: Changing the Contents of a Field.
* Field Separators:: The field separator and how to change it.
* Constant Size:: Reading constant width data.
* Splitting By Content:: Defining Fields By Content
* Testing field creation:: Checking how @command{gawk} is splitting
records.
* Multiple Line:: Reading multiline records.
* Getline:: Reading files under explicit program control
using the @code{getline} function.
* Read Timeout:: Reading input with a timeout.
* Retrying Input:: Retrying input after certain errors.
* Command-line directories:: What happens if you put a directory on the
command line.
* Input Summary:: Input summary.
* Input Exercises:: Exercises.
@end menu
@node Records
@section How Input Is Split into Records
@cindex input @subentry splitting into records
@cindex records @subentry splitting input into
@cindex @code{NR} variable
@cindex @code{FNR} variable
@command{awk} divides the input for your program into records and fields.
It keeps track of the number of records that have been read so far from
the current input file. This value is stored in a predefined variable
called @code{FNR}, which is reset to zero every time a new file is started.
Another predefined variable, @code{NR}, records the total number of input
records read so far from all @value{DF}s. It starts at zero, but is
never automatically reset to zero.
Normally, records are separated by newline characters. You can control how
records are separated by assigning values to the built-in variable @code{RS}.
If @code{RS} is any single character, that character separates records.
Otherwise (in @command{gawk}), @code{RS} is treated as a regular expression.
This mechanism is explained in greater detail shortly.
@menu
* awk split records:: How standard @command{awk} splits records.
* gawk split records:: How @command{gawk} splits records.
@end menu
@node awk split records
@subsection Record Splitting with Standard @command{awk}
@cindex separators @subentry for records
@cindex record separators
Records are separated by a character called the @dfn{record separator}.
By default, the record separator is the newline character.
This is why records are, by default, single lines.
To use a different character for the record separator,
simply assign that character to the predefined variable @code{RS}.
@cindex record separators @subentry newlines as
@cindex newlines @subentry as record separators
@cindex @code{RS} variable
Like any other variable,
the value of @code{RS} can be changed in the @command{awk} program
with the assignment operator, @samp{=}
(@pxref{Assignment Ops}).
The new record-separator character should be enclosed in quotation marks,
which indicate a string constant. Often, the right time to do this is
at the beginning of execution, before any input is processed,
so that the very first record is read with the proper separator.
To do this, use the special @code{BEGIN} pattern
(@pxref{BEGIN/END}).
For example:
@example
awk 'BEGIN @{ RS = "u" @}
@{ print $0 @}' mail-list
@end example
@noindent
changes the value of @code{RS} to @samp{u}, before reading any input.
The new value is a string whose first character is the letter ``u''; as a result, records
are separated by the letter ``u''. Then the input file is read, and the second
rule in the @command{awk} program (the action with no pattern) prints each
record. Because each @code{print} statement adds a newline at the end of
its output, this @command{awk} program copies the input
with each @samp{u} changed to a newline. Here are the results of running
the program on @file{mail-list}:
@example
@group
$ @kbd{awk 'BEGIN @{ RS = "u" @}}
> @kbd{@{ print $0 @}' mail-list}
@end group
@print{} Amelia 555-5553 amelia.zodiac
@print{} sq
@print{} e@@gmail.com F
@print{} Anthony 555-3412 anthony.assert
@print{} ro@@hotmail.com A
@print{} Becky 555-7685 becky.algebrar
@print{} m@@gmail.com A
@print{} Bill 555-1675 bill.drowning@@hotmail.com A
@print{} Broderick 555-0542 broderick.aliq
@print{} otiens@@yahoo.com R
@print{} Camilla 555-2912 camilla.inf
@print{} sar
@print{} m@@skynet.be R
@print{} Fabi
@print{} s 555-1234 fabi
@print{} s.
@print{} ndevicesim
@print{} s@@
@print{} cb.ed
@print{} F
@print{} J
@print{} lie 555-6699 j
@print{} lie.perscr
@print{} tabor@@skeeve.com F
@print{} Martin 555-6480 martin.codicib
@print{} s@@hotmail.com A
@print{} Sam
@print{} el 555-3430 sam
@print{} el.lanceolis@@sh
@print{} .ed
@print{} A
@print{} Jean-Pa
@print{} l 555-2127 jeanpa
@print{} l.campanor
@print{} m@@ny
@print{} .ed
@print{} R
@print{}
@end example
@noindent
Note that the entry for the name @samp{Bill} is not split.
In the original @value{DF}
(@pxref{Sample Data Files}),
the line looks like this:
@example
Bill 555-1675 bill.drowning@@hotmail.com A
@end example
@noindent
It contains no @samp{u}, so there is no reason to split the record,
unlike the others, which each have one or more occurrences of the @samp{u}.
In fact, this record is treated as part of the previous record;
the newline separating them in the output
is the original newline in the @value{DF}, not the one added by
@command{awk} when it printed the record!
@cindex record separators @subentry changing
@cindex separators @subentry for records
Another way to change the record separator is on the command line,
using the variable-assignment feature
(@pxref{Other Arguments}):
@example
awk '@{ print $0 @}' RS="u" mail-list
@end example
@noindent
This sets @code{RS} to @samp{u} before processing @file{mail-list}.
Using an alphabetic character such as @samp{u} for the record separator
is highly likely to produce strange results.
Using an unusual character such as @samp{/} is more likely to
produce correct behavior in the majority of cases, but there
are no guarantees. The moral is: Know Your Data.
@command{gawk} allows @code{RS} to be a full regular expression
(discussed shortly; @pxref{gawk split records}). Even so, using
a regular expression metacharacter, such as @samp{.} as the single
character in the value of @code{RS} has no special effect: it is
treated literally. This is required for backwards compatibility with
both Unix @command{awk} and with POSIX.
When using regular characters as the record separator,
there is one unusual case that occurs when @command{gawk} is
being fully POSIX-compliant (@pxref{Options}).
Then, the following (extreme) pipeline prints a surprising @samp{1}:
@example
$ @kbd{echo | gawk --posix 'BEGIN @{ RS = "a" @} ; @{ print NF @}'}
@print{} 1
@end example
There is one field, consisting of a newline. The value of the built-in
variable @code{NF} is the number of fields in the current record.
(In the normal case, @command{gawk} treats the newline as whitespace,
printing @samp{0} as the result. Most other versions of @command{awk}
also act this way.)
@cindex dark corner @subentry input files
Reaching the end of an input file terminates the current input record,
even if the last character in the file is not the character in @code{RS}.
@value{DARKCORNER}
@cindex empty strings @seeentry{null strings}
@cindex null strings
@cindex strings @subentry empty @seeentry{null strings}
The empty string @code{""} (a string without any characters)
has a special meaning
as the value of @code{RS}. It means that records are separated
by one or more blank lines and nothing else.
@xref{Multiple Line} for more details.
If you change the value of @code{RS} in the middle of an @command{awk} run,
the new value is used to delimit subsequent records, but the record
currently being processed, as well as records already processed, are not
affected.
@cindex @command{gawk} @subentry @code{RT} variable in
@cindex @code{RT} variable
@cindex records @subentry terminating
@cindex terminating records
@cindex differences in @command{awk} and @command{gawk} @subentry record separators
@cindex differences in @command{awk} and @command{gawk} @subentry @code{RS}/@code{RT} variables
@cindex regular expressions @subentry as record separators
@cindex record separators @subentry regular expressions as
@cindex separators @subentry for records @subentry regular expressions as
After the end of the record has been determined, @command{gawk}
sets the variable @code{RT} to the text in the input that matched
@code{RS}.
@node gawk split records
@subsection Record Splitting with @command{gawk}
@cindex common extensions @subentry @code{RS} as a regexp
@cindex extensions @subentry common @subentry @code{RS} as a regexp
When using @command{gawk}, the value of @code{RS} is not limited to a
one-character string. If it contains more than one character, it is
treated as a regular expression
(@pxref{Regexp}). @value{COMMONEXT}
In general, each record
ends at the next string that matches the regular expression; the next
record starts at the end of the matching string. This general rule is
actually at work in the usual case, where @code{RS} contains just a
newline: a record ends at the beginning of the next matching string (the
next newline in the input), and the following record starts just after
the end of this string (at the first character of the following line).
The newline, because it matches @code{RS}, is not part of either record.
When @code{RS} is a single character, @code{RT}
contains the same single character. However, when @code{RS} is a
regular expression, @code{RT} contains
the actual input text that matched the regular expression.
If the input file ends without any text matching @code{RS},
@command{gawk} sets @code{RT} to the null string.
The following example illustrates both of these features.
It sets @code{RS} equal to a regular expression that
matches either a newline or a series of one or more uppercase letters
with optional leading and/or trailing whitespace:
@example
@group
$ @kbd{echo record 1 AAAA record 2 BBBB record 3 |}
> @kbd{gawk 'BEGIN @{ RS = "\n|( *[[:upper:]]+ *)" @}}
> @kbd{@{ print "Record =", $0,"and RT = [" RT "]" @}'}
@end group
@print{} Record = record 1 and RT = [ AAAA ]
@print{} Record = record 2 and RT = [ BBBB ]
@print{} Record = record 3 and RT = [
@print{} ]
@end example
@noindent
The square brackets delineate the contents of @code{RT}, letting you
see the leading and trailing whitespace. The final value of
@code{RT} is a newline.
@xref{Simple Sed} for a more useful example
of @code{RS} as a regexp and @code{RT}.
If you set @code{RS} to a regular expression that allows optional
trailing text, such as @samp{RS = "abc(XYZ)?"}, it is possible, due
to implementation constraints, that @command{gawk} may match the leading
part of the regular expression, but not the trailing part, particularly
if the input text that could match the trailing part is fairly long.
@command{gawk} attempts to avoid this problem, but currently, there's
no guarantee that this will never happen.
@quotation NOTE
Remember that in @command{awk}, the @samp{^} and @samp{$} anchor
metacharacters match the beginning and end of a @emph{string}, and not
the beginning and end of a @emph{line}. As a result, something like
@samp{RS = "^[[:upper:]]"} can only match at the beginning of a file.
This is because @command{gawk} views the input file as one long string
that happens to contain newline characters.
It is thus best to avoid anchor metacharacters in the value of @code{RS}.
@end quotation
@cindex @command{gawk} @subentry @code{RT} variable in
@cindex @code{RT} variable
@cindex differences in @command{awk} and @command{gawk} @subentry @code{RS}/@code{RT} variables
The use of @code{RS} as a regular expression and the @code{RT}
variable are @command{gawk} extensions; they are not available in
compatibility mode
(@pxref{Options}).
In compatibility mode, only the first character of the value of
@code{RS} determines the end of the record.
@cindex Brian Kernighan's @command{awk}
@command{mawk} has allowed @code{RS} to be a regexp for decades.
As of October, 2019, BWK @command{awk} also supports it. Neither
version supplies @code{RT}, however.
@cindex sidebar @subentry @code{RS = "\0"} Is Not Portable
@ifdocbook
@docbook
<sidebar><title>@code{RS = "\0"} Is Not Portable</title>
@end docbook
@cindex portability @subentry data files as single record
There are times when you might want to treat an entire @value{DF} as a
single record. The only way to make this happen is to give @code{RS}
a value that you know doesn't occur in the input file. This is hard
to do in a general way, such that a program always works for arbitrary
input files.
You might think that for text files, the @sc{nul} character, which
consists of a character with all bits equal to zero, is a good
value to use for @code{RS} in this case:
@example
BEGIN @{ RS = "\0" @} # whole file becomes one record?
@end example
@cindex differences in @command{awk} and @command{gawk} @subentry strings @subentry storing
@command{gawk} in fact accepts this, and uses the @sc{nul}
character for the record separator.
This works for certain special files, such as @file{/proc/environ} on
GNU/Linux systems, where the @sc{nul} character is in fact the record separator.
However, this usage is @emph{not} portable
to most other @command{awk} implementations.
@cindex dark corner @subentry strings, storing
Almost all other @command{awk} implementations@footnote{At least that we know
about.} store strings internally as C-style strings. C strings use the
@sc{nul} character as the string terminator. In effect, this means that
@samp{RS = "\0"} is the same as @samp{RS = ""}.
@value{DARKCORNER}
It happens that recent versions of @command{mawk} can use the @sc{nul}
character as a record separator. However, this is a special case:
@command{mawk} does not allow embedded @sc{nul} characters in strings.
(This may change in a future version of @command{mawk}.)
@cindex records @subentry treating files as
@cindex treating files, as single records
@cindex single records, treating files as
@xref{Readfile Function} for an interesting way to read
whole files. If you are using @command{gawk}, see @ref{Extension Sample
Readfile} for another option.
@docbook
</sidebar>
@end docbook
@end ifdocbook
@ifnotdocbook
@cartouche
@center @b{@code{RS = "\0"} Is Not Portable}
@cindex portability @subentry data files as single record
There are times when you might want to treat an entire @value{DF} as a
single record. The only way to make this happen is to give @code{RS}
a value that you know doesn't occur in the input file. This is hard
to do in a general way, such that a program always works for arbitrary
input files.
You might think that for text files, the @sc{nul} character, which
consists of a character with all bits equal to zero, is a good
value to use for @code{RS} in this case:
@example
BEGIN @{ RS = "\0" @} # whole file becomes one record?
@end example
@cindex differences in @command{awk} and @command{gawk} @subentry strings @subentry storing
@command{gawk} in fact accepts this, and uses the @sc{nul}
character for the record separator.
This works for certain special files, such as @file{/proc/environ} on
GNU/Linux systems, where the @sc{nul} character is in fact the record separator.
However, this usage is @emph{not} portable
to most other @command{awk} implementations.
@cindex dark corner @subentry strings, storing
Almost all other @command{awk} implementations@footnote{At least that we know
about.} store strings internally as C-style strings. C strings use the
@sc{nul} character as the string terminator. In effect, this means that
@samp{RS = "\0"} is the same as @samp{RS = ""}.
@value{DARKCORNER}
It happens that recent versions of @command{mawk} can use the @sc{nul}
character as a record separator. However, this is a special case:
@command{mawk} does not allow embedded @sc{nul} characters in strings.
(This may change in a future version of @command{mawk}.)
@cindex records @subentry treating files as
@cindex treating files, as single records
@cindex single records, treating files as
@xref{Readfile Function} for an interesting way to read
whole files. If you are using @command{gawk}, see @ref{Extension Sample
Readfile} for another option.
@end cartouche
@end ifnotdocbook
@node Fields
@section Examining Fields
@cindex examining fields
@cindex fields
@cindex accessing fields
@cindex fields @subentry examining
@cindex whitespace @subentry definition of
When @command{awk} reads an input record, the record is
automatically @dfn{parsed} or separated by the @command{awk} utility into chunks
called @dfn{fields}. By default, fields are separated by @dfn{whitespace},
like words in a line.
Whitespace in @command{awk} means any string of one or more spaces,
TABs, or newlines; other characters
that are considered whitespace by other languages
(such as formfeed, vertical tab, etc.) are @emph{not} considered
whitespace by @command{awk}.
The purpose of fields is to make it more convenient for you to refer to
these pieces of the record. You don't have to use them---you can
operate on the whole record if you want---but fields are what make
simple @command{awk} programs so powerful.
@cindex field operator @code{$}
@cindex @code{$} (dollar sign) @subentry @code{$} field operator
@cindex dollar sign (@code{$}) @subentry @code{$} field operator
@cindex field operators, dollar sign as
You use a dollar sign (@samp{$})
to refer to a field in an @command{awk} program,
followed by the number of the field you want. Thus, @code{$1}
refers to the first field, @code{$2} to the second, and so on.
(Unlike in the Unix shells, the field numbers are not limited to single digits.
@code{$127} is the 127th field in the record.)
For example, suppose the following is a line of input:
@example
This seems like a pretty nice example.
@end example
@noindent
Here the first field, or @code{$1}, is @samp{This}, the second field, or
@code{$2}, is @samp{seems}, and so on. Note that the last field,
@code{$7}, is @samp{example.}. Because there is no space between the
@samp{e} and the @samp{.}, the period is considered part of the seventh
field.
@cindex @code{NF} variable
@cindex fields @subentry number of
@code{NF} is a predefined variable whose value is the number of fields
in the current record. @command{awk} automatically updates the value
of @code{NF} each time it reads a record. No matter how many fields
there are, the last field in a record can be represented by @code{$NF}.
So, @code{$NF} is the same as @code{$7}, which is @samp{example.}.
If you try to reference a field beyond the last
one (such as @code{$8} when the record has only seven fields), you get
the empty string. (If used in a numeric operation, you get zero.)
The use of @code{$0}, which looks like a reference to the ``zeroth'' field, is
a special case: it represents the whole input record. Use it
when you are not interested in specific fields.
Here are some more examples:
@example
$ @kbd{awk '$1 ~ /li/ @{ print $0 @}' mail-list}
@print{} Amelia 555-5553 amelia.zodiacusque@@gmail.com F
@print{} Julie 555-6699 julie.perscrutabor@@skeeve.com F
@end example
@noindent
This example prints each record in the file @file{mail-list} whose first
field contains the string @samp{li}.
By contrast, the following example looks for @samp{li} in @emph{the
entire record} and prints the first and last fields for each matching
input record:
@example
$ @kbd{awk '/li/ @{ print $1, $NF @}' mail-list}
@print{} Amelia F
@print{} Broderick R
@print{} Julie F
@print{} Samuel A
@end example
@node Nonconstant Fields
@section Nonconstant Field Numbers
@cindex fields @subentry numbers
@cindex field numbers
A field number need not be a constant. Any expression in
the @command{awk} language can be used after a @samp{$} to refer to a
field. The value of the expression specifies the field number. If the
value is a string, rather than a number, it is converted to a number.
Consider this example:
@example
awk '@{ print $NR @}'
@end example
@noindent
Recall that @code{NR} is the number of records read so far: one in the
first record, two in the second, and so on. So this example prints the first
field of the first record, the second field of the second record, and so
on. For the twentieth record, field number 20 is printed; most likely,
the record has fewer than 20 fields, so this prints a blank line.
Here is another example of using expressions as field numbers:
@example
awk '@{ print $(2*2) @}' mail-list
@end example
@command{awk} evaluates the expression @samp{(2*2)} and uses
its value as the number of the field to print. The @samp{*}
represents multiplication, so the expression @samp{2*2} evaluates to four.
The parentheses are used so that the multiplication is done before the
@samp{$} operation; they are necessary whenever there is a binary
operator@footnote{A @dfn{binary operator}, such as @samp{*} for
multiplication, is one that takes two operands. The distinction
is required because @command{awk} also has unary (one-operand)
and ternary (three-operand) operators.}
in the field-number expression. This example, then, prints the
type of relationship (the fourth field) for every line of the file
@file{mail-list}. (All of the @command{awk} operators are listed, in
order of decreasing precedence, in
@ref{Precedence}.)
If the field number you compute is zero, you get the entire record.
Thus, @samp{$(2-2)} has the same value as @code{$0}. Negative field
numbers are not allowed; trying to reference one usually terminates
the program. (The POSIX standard does not define
what happens when you reference a negative field number. @command{gawk}
notices this and terminates your program. Other @command{awk}
implementations may behave differently.)
As mentioned in @ref{Fields},
@command{awk} stores the current record's number of fields in the built-in
variable @code{NF} (also @pxref{Built-in Variables}). Thus, the expression
@code{$NF} is not a special feature---it is the direct consequence of
evaluating @code{NF} and using its value as a field number.
@node Changing Fields
@section Changing the Contents of a Field
@cindex fields @subentry changing contents of
The contents of a field, as seen by @command{awk}, can be changed within an
@command{awk} program; this changes what @command{awk} perceives as the
current input record. (The actual input is untouched; @command{awk} @emph{never}
modifies the input file.)
Consider the following example and its output:
@example
$ @kbd{awk '@{ nboxes = $3 ; $3 = $3 - 10}
> @kbd{print nboxes, $3 @}' inventory-shipped}
@print{} 25 15
@print{} 32 22
@print{} 24 14
@dots{}
@end example
@noindent
The program first saves the original value of field three in the variable
@code{nboxes}.
The @samp{-} sign represents subtraction, so this program reassigns
field three, @code{$3}, as the original value of field three minus ten:
@samp{$3 - 10}. (@xref{Arithmetic Ops}.)
Then it prints the original and new values for field three.
(Someone in the warehouse made a consistent mistake while inventorying
the red boxes.)
For this to work, the text in @code{$3} must make sense
as a number; the string of characters must be converted to a number
for the computer to do arithmetic on it. The number resulting
from the subtraction is converted back to a string of characters that
then becomes field three.
@xref{Conversion}.
When the value of a field is changed (as perceived by @command{awk}), the
text of the input record is recalculated to contain the new field where
the old one was. In other words, @code{$0} changes to reflect the altered
field. Thus, this program
prints a copy of the input file, with 10 subtracted from the second
field of each line:
@example
$ @kbd{awk '@{ $2 = $2 - 10; print $0 @}' inventory-shipped}
@print{} Jan 3 25 15 115
@print{} Feb 5 32 24 226
@print{} Mar 5 24 34 228
@dots{}
@end example
It is also possible to assign contents to fields that are out
of range. For example:
@example
$ @kbd{awk '@{ $6 = ($5 + $4 + $3 + $2)}
> @kbd{ print $6 @}' inventory-shipped}
@print{} 168
@print{} 297
@print{} 301
@dots{}
@end example
@cindex adding @subentry fields
@cindex fields @subentry adding
@noindent
We've just created @code{$6}, whose value is the sum of fields
@code{$2}, @code{$3}, @code{$4}, and @code{$5}. The @samp{+} sign
represents addition. For the file @file{inventory-shipped}, @code{$6}
represents the total number of parcels shipped for a particular month.
Creating a new field changes @command{awk}'s internal copy of the current
input record, which is the value of @code{$0}. Thus, if you do @samp{print $0}
after adding a field, the record printed includes the new field, with
the appropriate number of field separators between it and the previously
existing fields.
@cindex @code{OFS} variable
@cindex output field separator @seeentry{@code{OFS} variable}
@cindex field separator @seealso{@code{OFS}}
This recomputation affects and is affected by
@code{NF} (the number of fields; @pxref{Fields}).
For example, the value of @code{NF} is set to the number of the highest
field you create.
The exact format of @code{$0} is also affected by a feature that has not been discussed yet:
the @dfn{output field separator}, @code{OFS},
used to separate the fields (@pxref{Output Separators}).
Note, however, that merely @emph{referencing} an out-of-range field
does @emph{not} change the value of either @code{$0} or @code{NF}.
Referencing an out-of-range field only produces an empty string. For
example:
@example
if ($(NF+1) != "")
print "can't happen"
else
print "everything is normal"
@end example
@noindent
should print @samp{everything is normal}, because @code{NF+1} is certain
to be out of range. (@xref{If Statement}
for more information about @command{awk}'s @code{if-else} statements.
@xref{Typing and Comparison}
for more information about the @samp{!=} operator.)
It is important to note that making an assignment to an existing field
changes the
value of @code{$0} but does not change the value of @code{NF},
even when you assign the empty string to a field. For example:
@example
$ @kbd{echo a b c d | awk '@{ OFS = ":"; $2 = ""}
> @kbd{print $0; print NF @}'}
@print{} a::c:d
@print{} 4
@end example
@noindent
The field is still there; it just has an empty value, delimited by
the two colons between @samp{a} and @samp{c}.
This example shows what happens if you create a new field:
@example
$ @kbd{echo a b c d | awk '@{ OFS = ":"; $2 = ""; $6 = "new"}
> @kbd{print $0; print NF @}'}
@print{} a::c:d::new
@print{} 6
@end example
@noindent
The intervening field, @code{$5}, is created with an empty value
(indicated by the second pair of adjacent colons),
and @code{NF} is updated with the value six.
@cindex dark corner @subentry @code{NF} variable, decrementing
@cindex @code{NF} variable @subentry decrementing
Decrementing @code{NF} throws away the values of the fields
after the new value of @code{NF} and recomputes @code{$0}.
@value{DARKCORNER}
Here is an example:
@example
$ @kbd{echo a b c d e f | awk '@{ print "NF =", NF;}
> @kbd{ NF = 3; print $0 @}'}
@print{} NF = 6
@print{} a b c
@end example
@cindex portability @subentry @code{NF} variable, decrementing
@quotation CAUTION
Some versions of @command{awk} don't
rebuild @code{$0} when @code{NF} is decremented.
Until August, 2018, this included BWK @command{awk}; fortunately
his version now handles this correctly.
@end quotation
Finally, there are times when it is convenient to force
@command{awk} to rebuild the entire record, using the current
values of the fields and @code{OFS}. To do this, use the
seemingly innocuous assignment:
@example
@group
$1 = $1 # force record to be reconstituted
print $0 # or whatever else with $0
@end group
@end example
@noindent
This forces @command{awk} to rebuild the record. It does help
to add a comment, as we've shown here.
There is a flip side to the relationship between @code{$0} and
the fields. Any assignment to @code{$0} causes the record to be
reparsed into fields using the @emph{current} value of @code{FS}.
This also applies to any built-in function that updates @code{$0},
such as @code{sub()} and @code{gsub()}
(@pxref{String Functions}).
@cindex sidebar @subentry Understanding @code{$0}
@ifdocbook
@docbook
<sidebar><title>Understanding @code{$0}</title>
@end docbook
It is important to remember that @code{$0} is the @emph{full}
record, exactly as it was read from the input. This includes
any leading or trailing whitespace, and the exact whitespace (or other
characters) that separates the fields.
It is a common error to try to change the field separators
in a record simply by setting @code{FS} and @code{OFS}, and then
expecting a plain @samp{print} or @samp{print $0} to print the
modified record.
But this does not work, because nothing was done to change the record
itself. Instead, you must force the record to be rebuilt, typically
with a statement such as @samp{$1 = $1}, as described earlier.
@docbook
</sidebar>
@end docbook
@end ifdocbook
@ifnotdocbook
@cartouche
@center @b{Understanding @code{$0}}
It is important to remember that @code{$0} is the @emph{full}
record, exactly as it was read from the input. This includes
any leading or trailing whitespace, and the exact whitespace (or other
characters) that separates the fields.
It is a common error to try to change the field separators
in a record simply by setting @code{FS} and @code{OFS}, and then
expecting a plain @samp{print} or @samp{print $0} to print the
modified record.
But this does not work, because nothing was done to change the record
itself. Instead, you must force the record to be rebuilt, typically
with a statement such as @samp{$1 = $1}, as described earlier.
@end cartouche
@end ifnotdocbook
@node Field Separators
@section Specifying How Fields Are Separated
@menu
* Default Field Splitting:: How fields are normally separated.
* Regexp Field Splitting:: Using regexps as the field separator.
* Single Character Fields:: Making each character a separate field.
* Command Line Field Separator:: Setting @code{FS} from the command line.
* Full Line Fields:: Making the full line be a single field.
* Field Splitting Summary:: Some final points and a summary table.
@end menu
@cindex @code{FS} variable
@cindex fields @subentry separating
@cindex field separator
@cindex fields @subentry separating
The @dfn{field separator}, which is either a single character or a regular
expression, controls the way @command{awk} splits an input record into fields.
@command{awk} scans the input record for character sequences that
match the separator; the fields themselves are the text between the matches.
In the examples that follow, we use the bullet symbol (@bullet{}) to
represent spaces in the output.
If the field separator is @samp{oo}, then the following line:
@example
moo goo gai pan
@end example
@noindent
is split into three fields: @samp{m}, @samp{@bullet{}g}, and
@samp{@bullet{}gai@bullet{}pan}.
Note the leading spaces in the values of the second and third fields.
@cindex troubleshooting @subentry @command{awk} uses @code{FS} not @code{IFS}
The field separator is represented by the predefined variable @code{FS}.
Shell programmers take note: @command{awk} does @emph{not} use the
name @code{IFS} that is used by the POSIX-compliant shells (such as
the Unix Bourne shell, @command{sh}, or Bash).
@cindex @code{FS} variable @subentry changing value of
The value of @code{FS} can be changed in the @command{awk} program with the
assignment operator, @samp{=} (@pxref{Assignment Ops}).
Often, the right time to do this is at the beginning of execution
before any input has been processed, so that the very first record
is read with the proper separator. To do this, use the special
@code{BEGIN} pattern
(@pxref{BEGIN/END}).
For example, here we set the value of @code{FS} to the string
@code{","}:
@example
awk 'BEGIN @{ FS = "," @} ; @{ print $2 @}'
@end example
@cindex @code{BEGIN} pattern
@noindent
Given the input line:
@example
John Q. Smith, 29 Oak St., Walamazoo, MI 42139
@end example
@noindent
this @command{awk} program extracts and prints the string
@samp{@bullet{}29@bullet{}Oak@bullet{}St.}.
@cindex field separator @subentry choice of
@cindex regular expressions @subentry as field separators
@cindex field separator @subentry regular expression as
Sometimes the input data contains separator characters that don't
separate fields the way you thought they would. For instance, the
person's name in the example we just used might have a title or
suffix attached, such as:
@example
John Q. Smith, LXIX, 29 Oak St., Walamazoo, MI 42139
@end example
@noindent
The same program would extract @samp{@bullet{}LXIX} instead of
@samp{@bullet{}29@bullet{}Oak@bullet{}St.}.
If you were expecting the program to print the
address, you would be surprised. The moral is to choose your data layout and
separator characters carefully to prevent such problems.
(If the data is not in a form that is easy to process, perhaps you
can massage it first with a separate @command{awk} program.)
@node Default Field Splitting
@subsection Whitespace Normally Separates Fields
@cindex field separator @subentry whitespace as
@cindex whitespace @subentry as field separators
@cindex field separator @subentry @code{FS} variable and
@cindex separators @subentry field @subentry @code{FS} variable and
Fields are normally separated by whitespace sequences
(spaces, TABs, and newlines), not by single spaces. Two spaces in a row do not
delimit an empty field. The default value of the field separator @code{FS}
is a string containing a single space, @w{@code{" "}}. If @command{awk}
interpreted this value in the usual way, each space character would separate
fields, so two spaces in a row would make an empty field between them.
The reason this does not happen is that a single space as the value of
@code{FS} is a special case---it is taken to specify the default manner
of delimiting fields.
If @code{FS} is any other single character, such as @code{","}, then
each occurrence of that character separates two fields. Two consecutive
occurrences delimit an empty field. If the character occurs at the
beginning or the end of the line, that too delimits an empty field. The
space character is the only single character that does not follow these
rules.
@node Regexp Field Splitting
@subsection Using Regular Expressions to Separate Fields
@cindex regular expressions @subentry as field separators
@cindex field separator @subentry regular expression as
The previous @value{SUBSECTION}
discussed the use of single characters or simple strings as the
value of @code{FS}.
More generally, the value of @code{FS} may be a string containing any
regular expression. In this case, each match in the record for the regular
expression separates fields. For example, the assignment:
@example
FS = ", \t"
@end example
@noindent
makes every area of an input line that consists of a comma followed by a
space and a TAB into a field separator.
@ifinfo
(@samp{\t}
is an @dfn{escape sequence} that stands for a TAB;
@pxref{Escape Sequences},
for the complete list of similar escape sequences.)
@end ifinfo
For a less trivial example of a regular expression, try using
single spaces to separate fields the way single commas are used.
@code{FS} can be set to @w{@code{"[@ ]"}} (left bracket, space, right
bracket). This regular expression matches a single space and nothing else
(@pxref{Regexp}).
There is an important difference between the two cases of @samp{FS = @w{" "}}
(a single space) and @samp{FS = @w{"[ \t\n]+"}}
(a regular expression matching one or more spaces, TABs, or newlines).
For both values of @code{FS}, fields are separated by @dfn{runs}
(multiple adjacent occurrences) of spaces, TABs,
and/or newlines. However, when the value of @code{FS} is @w{@code{" "}},
@command{awk} first strips leading and trailing whitespace from
the record and then decides where the fields are.
For example, the following pipeline prints @samp{b}:
@example
$ @kbd{echo ' a b c d ' | awk '@{ print $2 @}'}
@print{} b
@end example
@noindent
However, this pipeline prints @samp{a} (note the extra spaces around
each letter):
@example
$ @kbd{echo ' a b c d ' | awk 'BEGIN @{ FS = "[ \t\n]+" @}}
> @kbd{@{ print $2 @}'}
@print{} a
@end example
@noindent
@cindex null strings
@cindex strings @subentry null
In this case, the first field is null, or empty.
The stripping of leading and trailing whitespace also comes into
play whenever @code{$0} is recomputed. For instance, study this pipeline:
@example
$ @kbd{echo ' a b c d' | awk '@{ print; $2 = $2; print @}'}
@print{} a b c d
@print{} a b c d
@end example
@noindent
The first @code{print} statement prints the record as it was read,
with leading whitespace intact. The assignment to @code{$2} rebuilds
@code{$0} by concatenating @code{$1} through @code{$NF} together,
separated by the value of @code{OFS} (which is a space by default).
Because the leading whitespace was ignored when finding @code{$1},
it is not part of the new @code{$0}. Finally, the last @code{print}
statement prints the new @code{$0}.
@cindex @code{FS} variable @subentry containing @code{^}
@cindex @code{^} (caret) @subentry in @code{FS}
@cindex dark corner @subentry @code{^}, in @code{FS}
There is an additional subtlety to be aware of when using regular expressions
for field splitting.
It is not well specified in the POSIX standard, or anywhere else, what @samp{^}
means when splitting fields. Does the @samp{^} match only at the beginning of
the entire record? Or is each field separator a new string? It turns out that
different @command{awk} versions answer this question differently, and you
should not rely on any specific behavior in your programs.
@value{DARKCORNER}
@cindex Brian Kernighan's @command{awk}
As a point of information, BWK @command{awk} allows @samp{^}
to match only at the beginning of the record. @command{gawk}
also works this way. For example:
@example
$ @kbd{echo 'xxAA xxBxx C' |}
> @kbd{gawk -F '(^x+)|( +)' '@{ for (i = 1; i <= NF; i++)}
> @kbd{ printf "-->%s<--\n", $i @}'}
@print{} --><--
@print{} -->AA<--
@print{} -->xxBxx<--
@print{} -->C<--
@end example
@node Single Character Fields
@subsection Making Each Character a Separate Field
@cindex common extensions @subentry single character fields
@cindex extensions @subentry common @subentry single character fields
@cindex differences in @command{awk} and @command{gawk} @subentry single-character fields
@cindex single-character fields
@cindex fields @subentry single-character
There are times when you may want to examine each character
of a record separately. This can be done in @command{gawk} by
simply assigning the null string (@code{""}) to @code{FS}. @value{COMMONEXT}
In this case,
each individual character in the record becomes a separate field.
For example:
@example
$ @kbd{echo a b | gawk 'BEGIN @{ FS = "" @}}
> @kbd{@{}
> @kbd{for (i = 1; i <= NF; i = i + 1)}
> @kbd{print "Field", i, "is", $i}
> @kbd{@}'}
@print{} Field 1 is a
@print{} Field 2 is
@print{} Field 3 is b
@end example
@cindex dark corner @subentry @code{FS} as null string
@cindex @code{FS} variable @subentry null string as
Traditionally, the behavior of @code{FS} equal to @code{""} was not defined.
In this case, most versions of Unix @command{awk} simply treat the entire record
as only having one field.
@value{DARKCORNER}
In compatibility mode
(@pxref{Options}),
if @code{FS} is the null string, then @command{gawk} also
behaves this way.
@node Command Line Field Separator
@subsection Setting @code{FS} from the Command Line
@cindex @option{-F} option @subentry command-line
@cindex field separator @subentry on command line
@cindex command line @subentry @code{FS} on, setting
@cindex @code{FS} variable @subentry setting from command line
@code{FS} can be set on the command line. Use the @option{-F} option to
do so. For example:
@example
awk -F, '@var{program}' @var{input-files}
@end example
@noindent
sets @code{FS} to the @samp{,} character. Notice that the option uses
an uppercase @samp{F} instead of a lowercase @samp{f}. The latter
option (@option{-f}) specifies a file containing an @command{awk} program.
The value used for the argument to @option{-F} is processed in exactly the
same way as assignments to the predefined variable @code{FS}.
Any special characters in the field separator must be escaped
appropriately. For example, to use a @samp{\} as the field separator
on the command line, you would have to type:
@example
# same as FS = "\\"
awk -F\\\\ '@dots{}' files @dots{}
@end example
@noindent
@cindex field separator @subentry backslash (@code{\}) as
@cindex @code{\} (backslash) @subentry as field separator
@cindex backslash (@code{\}) @subentry as field separator
Because @samp{\} is used for quoting in the shell, @command{awk} sees
@samp{-F\\}. Then @command{awk} processes the @samp{\\} for escape
characters (@pxref{Escape Sequences}), finally yielding
a single @samp{\} to use for the field separator.
@c @cindex historical features
As a special case, in compatibility mode
(@pxref{Options}),
if the argument to @option{-F} is @samp{t}, then @code{FS} is set to
the TAB character. If you type @samp{-F\t} at the
shell, without any quotes, the @samp{\} gets deleted, so @command{awk}
figures that you really want your fields to be separated with TABs and
not @samp{t}s. Use @samp{-v FS="t"} or @samp{-F"[t]"} on the command line
if you really do want to separate your fields with @samp{t}s.
Use @samp{-F '\t'} when not in compatibility mode to specify that TABs
separate fields.
As an example, let's use an @command{awk} program file called @file{edu.awk}
that contains the pattern @code{/edu/} and the action @samp{print $1}:
@example
/edu/ @{ print $1 @}
@end example
Let's also set @code{FS} to be the @samp{-} character and run the
program on the file @file{mail-list}. The following command prints a
list of the names of the people that work at or attend a university, and
the first three digits of their phone numbers:
@example
$ @kbd{awk -F- -f edu.awk mail-list}
@print{} Fabius 555
@print{} Samuel 555
@print{} Jean
@end example
@noindent
Note the third line of output. The third line
in the original file looked like this:
@example
Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R
@end example
The @samp{-} as part of the person's name was used as the field
separator, instead of the @samp{-} in the phone number that was
originally intended. This demonstrates why you have to be careful in
choosing your field and record separators.
@cindex Unix @command{awk} @subentry password files, field separators and
Perhaps the most common use of a single character as the field separator
occurs when processing the Unix system password file. On many Unix
systems, each user has a separate entry in the system password file, with one
line per user. The information in these lines is separated by colons.
The first field is the user's login name and the second is the user's
encrypted or shadow password. (A shadow password is indicated by the
presence of a single @samp{x} in the second field.) A password file
entry might look like this:
@cindex Robbins @subentry Arnold
@example
arnold:x:2076:10:Arnold Robbins:/home/arnold:/bin/bash
@end example
The following program searches the system password file and prints
the entries for users whose full name is not indicated:
@example
awk -F: '$5 == ""' /etc/passwd
@end example
@node Full Line Fields
@subsection Making the Full Line Be a Single Field
Occasionally, it's useful to treat the whole input line as a
single field. This can be done easily and portably simply by
setting @code{FS} to @code{"\n"} (a newline):@footnote{Thanks to
Andrew Schorr for this tip.}
@example
awk -F'\n' '@var{program}' @var{files @dots{}}
@end example
@noindent
When you do this, @code{$1} is the same as @code{$0}.
@cindex sidebar @subentry Changing @code{FS} Does Not Affect the Fields
@ifdocbook
@docbook
<sidebar><title>Changing @code{FS} Does Not Affect the Fields</title>
@end docbook
@cindex POSIX @command{awk} @subentry field separators and
@cindex field separator @subentry POSIX and
According to the POSIX standard, @command{awk} is supposed to behave
as if each record is split into fields at the time it is read.
In particular, this means that if you change the value of @code{FS}
after a record is read, the values of the fields (i.e., how they were split)
should reflect the old value of @code{FS}, not the new one.
@cindex dark corner @subentry field separators
@cindex @command{sed} utility
@cindex stream editors
However, many older implementations of @command{awk} do not work this way. Instead,
they defer splitting the fields until a field is actually
referenced. The fields are split
using the @emph{current} value of @code{FS}!
@value{DARKCORNER}
This behavior can be difficult
to diagnose. The following example illustrates the difference
between the two methods:
@example
sed 1q /etc/passwd | awk '@{ FS = ":" ; print $1 @}'
@end example
@noindent
which usually prints:
@example
root
@end example
@noindent
on an incorrect implementation of @command{awk}, while @command{gawk}
prints the full first line of the file, something like:
@example
root:x:0:0:Root:/:
@end example
(The @command{sed}@footnote{The @command{sed} utility is a ``stream editor.''
Its behavior is also defined by the POSIX standard.}
command prints just the first line of @file{/etc/passwd}.)
@docbook
</sidebar>
@end docbook
@end ifdocbook
@ifnotdocbook
@cartouche
@center @b{Changing @code{FS} Does Not Affect the Fields}
@cindex POSIX @command{awk} @subentry field separators and
@cindex field separator @subentry POSIX and
According to the POSIX standard, @command{awk} is supposed to behave
as if each record is split into fields at the time it is read.
In particular, this means that if you change the value of @code{FS}
after a record is read, the values of the fields (i.e., how they were split)
should reflect the old value of @code{FS}, not the new one.
@cindex dark corner @subentry field separators
@cindex @command{sed} utility
@cindex stream editors
However, many older implementations of @command{awk} do not work this way. Instead,
they defer splitting the fields until a field is actually
referenced. The fields are split
using the @emph{current} value of @code{FS}!
@value{DARKCORNER}
This behavior can be difficult
to diagnose. The following example illustrates the difference
between the two methods:
@example
sed 1q /etc/passwd | awk '@{ FS = ":" ; print $1 @}'
@end example
@noindent
which usually prints:
@example
root
@end example
@noindent
on an incorrect implementation of @command{awk}, while @command{gawk}
prints the full first line of the file, something like:
@example
root:x:0:0:Root:/:
@end example
(The @command{sed}@footnote{The @command{sed} utility is a ``stream editor.''
Its behavior is also defined by the POSIX standard.}
command prints just the first line of @file{/etc/passwd}.)
@end cartouche
@end ifnotdocbook
@node Field Splitting Summary
@subsection Field-Splitting Summary
It is important to remember that when you assign a string constant
as the value of @code{FS}, it undergoes normal @command{awk} string
processing. For example, with Unix @command{awk} and @command{gawk},
the assignment @samp{FS = "\.."} assigns the character string @code{".."}
to @code{FS} (the backslash is stripped). This creates a regexp meaning
``fields are separated by occurrences of any two characters.''
If instead you want fields to be separated by a literal period followed
by any single character, use @samp{FS = "\\.."}.
The following list summarizes how fields are split, based on the value
of @code{FS} (@samp{==} means ``is equal to''):
@table @code
@item FS == " "
Fields are separated by runs of whitespace. Leading and trailing
whitespace are ignored. This is the default.
@item FS == @var{any other single character}
Fields are separated by each occurrence of the character. Multiple
successive occurrences delimit empty fields, as do leading and
trailing occurrences.
The character can even be a regexp metacharacter; it does not need
to be escaped.
@item FS == @var{regexp}
Fields are separated by occurrences of characters that match @var{regexp}.
Leading and trailing matches of @var{regexp} delimit empty fields.
@item FS == ""
Each individual character in the record becomes a separate field.
(This is a common extension; it is not specified by the POSIX standard.)
@end table
@cindex sidebar @subentry @code{FS} and @code{IGNORECASE}
@ifdocbook
@docbook
<sidebar><title>@code{FS} and @code{IGNORECASE}</title>
@end docbook
The @code{IGNORECASE} variable
(@pxref{User-modified})
affects field splitting @emph{only} when the value of @code{FS} is a regexp.
It has no effect when @code{FS} is a single character, even if
that character is a letter. Thus, in the following code:
@example
FS = "c"
IGNORECASE = 1
$0 = "aCa"
print $1
@end example
@noindent
The output is @samp{aCa}. If you really want to split fields on an
alphabetic character while ignoring case, use a regexp that will
do it for you (e.g., @samp{FS = "[c]"}). In this case, @code{IGNORECASE}
will take effect.
@docbook
</sidebar>
@end docbook
@end ifdocbook
@ifnotdocbook
@cartouche
@center @b{@code{FS} and @code{IGNORECASE}}
The @code{IGNORECASE} variable
(@pxref{User-modified})
affects field splitting @emph{only} when the value of @code{FS} is a regexp.
It has no effect when @code{FS} is a single character, even if
that character is a letter. Thus, in the following code:
@example
FS = "c"
IGNORECASE = 1
$0 = "aCa"
print $1
@end example
@noindent
The output is @samp{aCa}. If you really want to split fields on an
alphabetic character while ignoring case, use a regexp that will
do it for you (e.g., @samp{FS = "[c]"}). In this case, @code{IGNORECASE}
will take effect.
@end cartouche
@end ifnotdocbook
@node Constant Size
@section Reading Fixed-Width Data
@cindex data, fixed-width
@cindex fixed-width data
@cindex advanced features @subentry fixed-width data
@c O'Reilly doesn't like it as a note the first thing in the section.
This @value{SECTION} discusses an advanced
feature of @command{gawk}. If you are a novice @command{awk} user,
you might want to skip it on the first reading.
@command{gawk} provides a facility for dealing with fixed-width fields
with no distinctive field separator. We discuss this feature in
the following @value{SUBSECTION}s.
@menu
* Fixed width data:: Processing fixed-width data.
* Skipping intervening:: Skipping intervening fields.
* Allowing trailing data:: Capturing optional trailing data.
* Fields with fixed data:: Field values with fixed-width data.
@end menu
@node Fixed width data
@subsection Processing Fixed-Width Data
An example of fixed-width data would be the input for old Fortran programs
where numbers are run together, or the output of programs that did not
anticipate the use of their output as input for other programs.
An example of the latter is a table where all the columns are lined up
by the use of a variable number of spaces and @emph{empty fields are
just spaces}. Clearly, @command{awk}'s normal field splitting based
on @code{FS} does not work well in this case. Although a portable
@command{awk} program can use a series of @code{substr()} calls on
@code{$0} (@pxref{String Functions}), this is awkward and inefficient
for a large number of fields.
@cindex troubleshooting @subentry fatal errors @subentry field widths, specifying
@cindex @command{w} utility
@cindex @code{FIELDWIDTHS} variable
@cindex @command{gawk} @subentry @code{FIELDWIDTHS} variable in
The splitting of an input record into fixed-width fields is specified by
assigning a string containing space-separated numbers to the built-in
variable @code{FIELDWIDTHS}. Each number specifies the width of the
field, @emph{including} columns between fields. If you want to ignore
the columns between fields, you can specify the width as a separate
field that is subsequently ignored. It is a fatal error to supply a
field width that has a negative value.
The following data is the output of the Unix @command{w} utility. It is useful
to illustrate the use of @code{FIELDWIDTHS}:
@example
@group
10:06pm up 21 days, 14:04, 23 users
User tty login@ idle JCPU PCPU what
hzuo ttyV0 8:58pm 9 5 vi p24.tex
hzang ttyV3 6:37pm 50 -csh
eklye ttyV5 9:53pm 7 1 em thes.tex
dportein ttyV6 8:17pm 1:47 -csh
gierd ttyD3 10:00pm 1 elm
dave ttyD4 9:47pm 4 4 w
brent ttyp0 26Jun91 4:46 26:46 4:41 bash
dave ttyq4 26Jun9115days 46 46 wnewmail
@end group
@end example
The following program takes this input, converts the idle time to
number of seconds, and prints out the first two fields and the calculated
idle time:
@example
BEGIN @{ FIELDWIDTHS = "9 6 10 6 7 7 35" @}
NR > 2 @{
idle = $4
sub(/^ +/, "", idle) # strip leading spaces
if (idle == "")
idle = 0
if (idle ~ /:/) @{ # hh:mm
split(idle, t, ":")
idle = t[1] * 60 + t[2]
@}
if (idle ~ /days/)
idle *= 24 * 60 * 60
print $1, $2, idle
@}
@end example
@quotation NOTE
The preceding program uses a number of @command{awk} features that
haven't been introduced yet.
@end quotation
Running the program on the data produces the following results:
@example
hzuo ttyV0 0
hzang ttyV3 50
eklye ttyV5 0
dportein ttyV6 107
gierd ttyD3 1
dave ttyD4 0
brent ttyp0 286
dave ttyq4 1296000
@end example
Another (possibly more practical) example of fixed-width input data
is the input from a deck of balloting cards. In some parts of
the United States, voters mark their choices by punching holes in computer
cards. These cards are then processed to count the votes for any particular
candidate or on any particular issue. Because a voter may choose not to
vote on some issue, any column on the card may be empty. An @command{awk}
program for processing such data could use the @code{FIELDWIDTHS} feature
to simplify reading the data. (Of course, getting @command{gawk} to run on
a system with card readers is another story!)
@node Skipping intervening
@subsection Skipping Intervening Fields
Starting in @value{PVERSION} 4.2, each field width may optionally be
preceded by a colon-separated value specifying the number of characters
to skip before the field starts. Thus, the preceding program could be
rewritten to specify @code{FIELDWIDTHS} like so:
@example
BEGIN @{ FIELDWIDTHS = "8 1:5 4:7 6 1:6 1:6 2:33" @}
@end example
This strips away some of the white space separating the fields. With such
a change, the program produces the following results:
@example
hzang ttyV3 50
eklye ttyV5 0
dportein ttyV6 107
gierd ttyD3 1
dave ttyD4 0
brent ttyp0 286
dave ttyq4 1296000
@end example
@node Allowing trailing data
@subsection Capturing Optional Trailing Data
There are times when fixed-width data may be followed by additional data
that has no fixed length. Such data may or may not be present, but if
it is, it should be possible to get at it from an @command{awk} program.
Starting with @value{PVERSION} 4.2, in order to provide a way to say ``anything
else in the record after the defined fields,'' @command{gawk}
allows you to add a final @samp{*} character to the value of
@code{FIELDWIDTHS}. There can only be one such character, and it must
be the final non-whitespace character in @code{FIELDWIDTHS}.
For example:
@example
$ @kbd{cat fw.awk} @ii{Show the program}
@print{} BEGIN @{ FIELDWIDTHS = "2 2 *" @}
@print{} @{ print NF, $1, $2, $3 @}
$ @kbd{cat fw.in} @ii{Show sample input}
@print{} 1234abcdefghi
$ @kbd{gawk -f fw.awk fw.in} @ii{Run the program}
@print{} 3 12 34 abcdefghi
@end example
@node Fields with fixed data
@subsection Field Values With Fixed-Width Data
So far, so good. But what happens if there isn't as much data as there
should be based on the contents of @code{FIELDWIDTHS}? Or, what happens
if there is more data than expected?
For many years, what happens in these cases was not well defined. Starting
with @value{PVERSION} 4.2, the rules are as follows:
@table @asis
@item Enough data for some fields
For example, if @code{FIELDWIDTHS} is set to @code{"2 3 4"} and the
input record is @samp{aabbb}. In this case, @code{NF} is set to two.
@item Not enough data for a field
For example, if @code{FIELDWIDTHS} is set to @code{"2 3 4"} and the
input record is @samp{aab}. In this case, @code{NF} is set to two and
@code{$2} has the value @code{"b"}. The idea is that even though there
aren't as many characters as were expected, there are some, so the data
should be made available to the program.
@item Too much data
For example, if @code{FIELDWIDTHS} is set to @code{"2 3 4"} and the
input record is @samp{aabbbccccddd}. In this case, @code{NF} is set to
three and the extra characters (@samp{ddd}) are ignored. If you want
@command{gawk} to capture the extra characters, supply a final @samp{*}
in the value of @code{FIELDWIDTHS}.
@item Too much data, but with @samp{*} supplied
For example, if @code{FIELDWIDTHS} is set to @code{"2 3 4 *"} and the
input record is @samp{aabbbccccddd}. In this case, @code{NF} is set to
four, and @code{$4} has the value @code{"ddd"}.
@end table
@node Splitting By Content
@section Defining Fields by Content
@menu
* More CSV:: More on CSV files.
@end menu
@c O'Reilly doesn't like it as a note the first thing in the section.
This @value{SECTION} discusses an advanced
feature of @command{gawk}. If you are a novice @command{awk} user,
you might want to skip it on the first reading.
@cindex advanced features @subentry specifying field content
Normally, when using @code{FS}, @command{gawk} defines the fields as the
parts of the record that occur in between each field separator. In other
words, @code{FS} defines what a field @emph{is not}, instead of what a field
@emph{is}.
However, there are times when you really want to define the fields by
what they are, and not by what they are not.
The most notorious such case
is so-called @dfn{comma-separated values} (CSV) data. Many spreadsheet programs,
for example, can export their data into text files, where each record is
terminated with a newline, and fields are separated by commas. If
commas only separated the data, there wouldn't be an issue. The problem comes when
one of the fields contains an @emph{embedded} comma.
In such cases, most programs embed the field in double quotes.@footnote{The
CSV format lacked a formal standard definition for many years.
@uref{http://www.ietf.org/rfc/rfc4180.txt, RFC 4180}
standardizes the most common practices.}
So, we might have data like this:
@example
@c file eg/misc/addresses.csv
Robbins,Arnold,"1234 A Pretty Street, NE",MyTown,MyState,12345-6789,USA
@c endfile
@end example
@cindex @command{gawk} @subentry @code{FPAT} variable in
@cindex @code{FPAT} variable
The @code{FPAT} variable offers a solution for cases like this.
The value of @code{FPAT} should be a string that provides a regular expression.
This regular expression describes the contents of each field.
In the case of CSV data as presented here, each field is either ``anything that
is not a comma,'' or ``a double quote, anything that is not a double quote, and a
closing double quote.'' (There are more complicated definitions of CSV data,
treated shortly.)
If written as a regular expression constant
(@pxref{Regexp}),
we would have @code{/([^,]+)|("[^"]+")/}.
Writing this as a string requires us to escape the double quotes, leading to:
@example
FPAT = "([^,]+)|(\"[^\"]+\")"
@end example
Putting this to use, here is a simple program to parse the data:
@example
@c file eg/misc/simple-csv.awk
@group
BEGIN @{
FPAT = "([^,]+)|(\"[^\"]+\")"
@}
@end group
@group
@{
print "NF = ", NF
for (i = 1; i <= NF; i++) @{
printf("$%d = <%s>\n", i, $i)
@}
@}
@end group
@c endfile
@end example
When run, we get the following:
@example
$ @kbd{gawk -f simple-csv.awk addresses.csv}
NF = 7
$1 = <Robbins>
$2 = <Arnold>
$3 = <"1234 A Pretty Street, NE">
$4 = <MyTown>
$5 = <MyState>
$6 = <12345-6789>
$7 = <USA>
@end example
Note the embedded comma in the value of @code{$3}.
A straightforward improvement when processing CSV data of this sort
would be to remove the quotes when they occur, with something like this:
@example
if (substr($i, 1, 1) == "\"") @{
len = length($i)
$i = substr($i, 2, len - 2) # Get text within the two quotes
@}
@end example
@quotation NOTE
Some programs export CSV data that contains embedded newlines between
the double quotes. @command{gawk} provides no way to deal with this.
Even though a formal specification for CSV data exists, there isn't much
more to be done;
the @code{FPAT} mechanism provides an elegant solution for the majority
of cases, and the @command{gawk} developers are satisfied with that.
@end quotation
As written, the regexp used for @code{FPAT} requires that each field
contain at least one character. A straightforward modification
(changing the first @samp{+} to @samp{*}) allows fields to be empty:
@example
FPAT = "([^,]*)|(\"[^\"]+\")"
@end example
@c FIXME: 4/2015
@c Consider use of FPAT = "([^,]*)|(\"[^\"]*\")"
@c (star in latter part of value) to allow quoted strings to be empty.
@c Per email from Ed Morton <mortoneccc@comcast.net>
As with @code{FS}, the @code{IGNORECASE} variable (@pxref{User-modified})
affects field splitting with @code{FPAT}.
Assigning a value to @code{FPAT} overrides field splitting
with @code{FS} and with @code{FIELDWIDTHS}.
Finally, the @code{patsplit()} function makes the same functionality
available for splitting regular strings (@pxref{String Functions}).
@node More CSV
@subsection More on CSV Files
@cindex Collado, Manuel
Manuel Collado notes that in addition to commas, a CSV field can also
contains quotes, that have to be escaped by doubling them. The previously
described regexps fail to accept quoted fields with both commas and
quotes inside. He suggests that the simplest @code{FPAT} expression that
recognizes this kind of fields is @code{/([^,]*)|("([^"]|"")+")/}. He
provides the following input data to test these variants:
@example
@c file eg/misc/sample.csv
p,"q,r",s
p,"q""r",s
p,"q,""r",s
p,"",s
p,,s
@c endfile
@end example
@noindent
And here is his test program:
@example
@c file eg/misc/test-csv.awk
@group
BEGIN @{
fp[0] = "([^,]+)|(\"[^\"]+\")"
fp[1] = "([^,]*)|(\"[^\"]+\")"
fp[2] = "([^,]*)|(\"([^\"]|\"\")+\")"
FPAT = fp[fpat+0]
@}
@end group
@group
@{
print "<" $0 ">"
printf("NF = %s ", NF)
for (i = 1; i <= NF; i++) @{
printf("<%s>", $i)
@}
print ""
@}
@end group
@c endfile
@end example
When run on the third variant, it produces:
@example
$ @kbd{gawk -v fpat=2 -f test-csv.awk sample.csv}
@print{} <p,"q,r",s>
@print{} NF = 3 <p><"q,r"><s>
@print{} <p,"q""r",s>
@print{} NF = 3 <p><"q""r"><s>
@print{} <p,"q,""r",s>
@print{} NF = 3 <p><"q,""r"><s>
@print{} <p,"",s>
@print{} NF = 3 <p><""><s>
@print{} <p,,s>
@print{} NF = 3 <p><><s>
@end example
@node Testing field creation
@section Checking How @command{gawk} Is Splitting Records
@cindex @command{gawk} @subentry splitting fields and
As we've seen, @command{gawk} provides three independent methods to split
input records into fields. The mechanism used is based on which of the
three variables---@code{FS}, @code{FIELDWIDTHS}, or @code{FPAT}---was
last assigned to. In addition, an API input parser may choose to override
the record parsing mechanism; please refer to @ref{Input Parsers} for
further information about this feature.
To restore normal field splitting after using @code{FIELDWIDTHS}
and/or @code{FPAT}, simply assign a value to @code{FS}.
You can use @samp{FS = FS} to do this,
without having to know the current value of @code{FS}.
In order to tell which kind of field splitting is in effect,
use @code{PROCINFO["FS"]} (@pxref{Auto-set}).
The value is @code{"FS"} if regular field splitting is being used,
@code{"FIELDWIDTHS"} if fixed-width field splitting is being used,
or @code{"FPAT"} if content-based field splitting is being used:
@example
if (PROCINFO["FS"] == "FS")
@var{regular field splitting} @dots{}
else if (PROCINFO["FS"] == "FIELDWIDTHS")
@var{fixed-width field splitting} @dots{}
else if (PROCINFO["FS"] == "FPAT")
@var{content-based field splitting} @dots{}
else
@var{API input parser field splitting} @dots{} @ii{(advanced feature)}
@end example
This information is useful when writing a function that needs to
temporarily change @code{FS} or @code{FIELDWIDTHS}, read some records,
and then restore the original settings (@pxref{Passwd Functions} for an
example of such a function).
@node Multiple Line
@section Multiple-Line Records
@cindex multiple-line records
@cindex records @subentry multiline
@cindex input @subentry multiline records
@cindex files @subentry reading @subentry multiline records
@cindex input, files @seeentry{input files}
In some databases, a single line cannot conveniently hold all the
information in one entry. In such cases, you can use multiline
records. The first step in doing this is to choose your data format.
@cindex record separators @subentry with multiline records
One technique is to use an unusual character or string to separate
records. For example, you could use the formfeed character (written
@samp{\f} in @command{awk}, as in C) to separate them, making each record
a page of the file. To do this, just set the variable @code{RS} to
@code{"\f"} (a string containing the formfeed character). Any
other character could equally well be used, as long as it won't be part
of the data in a record.
@cindex @code{RS} variable @subentry multiline records and
Another technique is to have blank lines separate records. By a special
dispensation, an empty string as the value of @code{RS} indicates that
records are separated by one or more blank lines. When @code{RS} is set
to the empty string, each record always ends at the first blank line
encountered. The next record doesn't start until the first nonblank
line that follows. No matter how many blank lines appear in a row, they
all act as one record separator.
(Blank lines must be completely empty; lines that contain only
whitespace do not count.)
@cindex leftmost longest match
@cindex matching @subentry leftmost longest
You can achieve the same effect as @samp{RS = ""} by assigning the
string @code{"\n\n+"} to @code{RS}. This regexp matches the newline
at the end of the record and one or more blank lines after the record.
In addition, a regular expression always matches the longest possible
sequence when there is a choice
(@pxref{Leftmost Longest}).
So, the next record doesn't start until
the first nonblank line that follows---no matter how many blank lines
appear in a row, they are considered one record separator.
@cindex dark corner @subentry multiline records
However, there is an important difference between @samp{RS = ""} and
@samp{RS = "\n\n+"}. In the first case, leading newlines in the input
@value{DF} are ignored, and if a file ends without extra blank lines
after the last record, the final newline is removed from the record.
In the second case, this special processing is not done.
@value{DARKCORNER}
@cindex field separator @subentry in multiline records
@cindex @code{FS} variable @subentry in multiline records
Now that the input is separated into records, the second step is to
separate the fields in the records. One way to do this is to divide each
of the lines into fields in the normal manner. This happens by default
as the result of a special feature. When @code{RS} is set to the empty
string @emph{and} @code{FS} is set to a single character,
the newline character @emph{always} acts as a field separator.
This is in addition to whatever field separations result from
@code{FS}.
@quotation NOTE
When @code{FS} is the null string (@code{""})
or a regexp, this special feature of @code{RS} does not apply.
It does apply to the default field separator of a single space:
@samp{FS = @w{" "}}.
Note that language in the POSIX specification implies that
this special feature should apply when @code{FS} is a regexp.
However, Unix @command{awk} has never behaved that way, nor has
@command{gawk}. This is essentially a bug in POSIX.
@c Noted as of 4/2019; working to get the standard fixed.
@end quotation
The original motivation for this special exception was probably to provide
useful behavior in the default case (i.e., @code{FS} is equal
to @w{@code{" "}}). This feature can be a problem if you really don't
want the newline character to separate fields, because there is no way to
prevent it. However, you can work around this by using the @code{split()}
function to break up the record manually
(@pxref{String Functions}).
If you have a single-character field separator, you can work around
the special feature in a different way, by making @code{FS} into a
regexp for that single character. For example, if the field
separator is a percent character, instead of
@samp{FS = "%"}, use @samp{FS = "[%]"}.
Another way to separate fields is to
put each field on a separate line: to do this, just set the
variable @code{FS} to the string @code{"\n"}.
(This single-character separator matches a single newline.)
A practical example of a @value{DF} organized this way might be a mailing
list, where blank lines separate the entries. Consider a mailing
list in a file named @file{addresses}, which looks like this:
@example
Jane Doe
123 Main Street
Anywhere, SE 12345-6789
John Smith
456 Tree-lined Avenue
Smallville, MW 98765-4321
@dots{}
@end example
@noindent
A simple program to process this file is as follows:
@example
# addrs.awk --- simple mailing list program
# Records are separated by blank lines.
# Each line is one field.
BEGIN @{ RS = "" ; FS = "\n" @}
@{
print "Name is:", $1
print "Address is:", $2
print "City and State are:", $3
print ""
@}
@end example
Running the program produces the following output:
@example
$ @kbd{awk -f addrs.awk addresses}
@print{} Name is: Jane Doe
@print{} Address is: 123 Main Street
@print{} City and State are: Anywhere, SE 12345-6789
@print{}
@print{} Name is: John Smith
@print{} Address is: 456 Tree-lined Avenue
@print{} City and State are: Smallville, MW 98765-4321
@print{}
@dots{}
@end example
@xref{Labels Program} for a more realistic program dealing with
address lists. The following list summarizes how records are split,
based on the value of
@ifinfo
@code{RS}.
(@samp{==} means ``is equal to.'')
@end ifinfo
@ifnotinfo
@code{RS}:
@end ifnotinfo
@table @code
@item RS == "\n"
Records are separated by the newline character (@samp{\n}). In effect,
every line in the @value{DF} is a separate record, including blank lines.
This is the default.
@item RS == @var{any single character}
Records are separated by each occurrence of the character. Multiple
successive occurrences delimit empty records.
@item RS == ""
Records are separated by runs of blank lines.
When @code{FS} is a single character, then
the newline character
always serves as a field separator, in addition to whatever value
@code{FS} may have. Leading and trailing newlines in a file are ignored.
@item RS == @var{regexp}
Records are separated by occurrences of characters that match @var{regexp}.
Leading and trailing matches of @var{regexp} delimit empty records.
(This is a @command{gawk} extension; it is not specified by the
POSIX standard.)
@end table
@cindex @command{gawk} @subentry @code{RT} variable in
@cindex @code{RT} variable
@cindex differences in @command{awk} and @command{gawk} @subentry @code{RS}/@code{RT} variables
If not in compatibility mode (@pxref{Options}), @command{gawk} sets
@code{RT} to the input text that matched the value specified by @code{RS}.
But if the input file ended without any text that matches @code{RS},
then @command{gawk} sets @code{RT} to the null string.
@node Getline
@section Explicit Input with @code{getline}
@cindex @code{getline} command @subentry explicit input with
@cindex input @subentry explicit
So far we have been getting our input data from @command{awk}'s main
input stream---either the standard input (usually your keyboard, sometimes
the output from another program) or the
files specified on the command line. The @command{awk} language has a
special built-in command called @code{getline} that
can be used to read input under your explicit control.
The @code{getline} command is used in several different ways and should
@emph{not} be used by beginners.
The examples that follow the explanation of the @code{getline} command
include material that has not been covered yet. Therefore, come back
and study the @code{getline} command @emph{after} you have reviewed the
rest of
@ifinfo
this @value{DOCUMENT}
@end ifinfo
@ifhtml
this @value{DOCUMENT}
@end ifhtml
@ifnotinfo
@ifnothtml
Parts I and II
@end ifnothtml
@end ifnotinfo
and have a good knowledge of how @command{awk} works.
@cindex @command{gawk} @subentry @code{ERRNO} variable in
@cindex @code{ERRNO} variable @subentry with @command{getline} command
@cindex differences in @command{awk} and @command{gawk} @subentry @code{getline} command
@cindex @code{getline} command @subentry return values
@cindex @option{--sandbox} option @subentry input redirection with @code{getline}
The @code{getline} command returns 1 if it finds a record and 0 if
it encounters the end of the file. If there is some error in getting
a record, such as a file that cannot be opened, then @code{getline}
returns @minus{}1. In this case, @command{gawk} sets the variable
@code{ERRNO} to a string describing the error that occurred.
If @code{ERRNO} indicates that the I/O operation may be
retried, and @code{PROCINFO["@var{input}", "RETRY"]} is set,
then @code{getline} returns @minus{}2
instead of @minus{}1, and further calls to @code{getline}
may be attempted. @xref{Retrying Input} for further information about
this feature.
In the following examples, @var{command} stands for a string value that
represents a shell command.
@quotation NOTE
When @option{--sandbox} is specified (@pxref{Options}),
reading lines from files, pipes, and coprocesses is disabled.
@end quotation
@menu
* Plain Getline:: Using @code{getline} with no arguments.
* Getline/Variable:: Using @code{getline} into a variable.
* Getline/File:: Using @code{getline} from a file.
* Getline/Variable/File:: Using @code{getline} into a variable from a
file.
* Getline/Pipe:: Using @code{getline} from a pipe.
* Getline/Variable/Pipe:: Using @code{getline} into a variable from a
pipe.
* Getline/Coprocess:: Using @code{getline} from a coprocess.
* Getline/Variable/Coprocess:: Using @code{getline} into a variable from a
coprocess.
* Getline Notes:: Important things to know about @code{getline}.
* Getline Summary:: Summary of @code{getline} Variants.
@end menu
@node Plain Getline
@subsection Using @code{getline} with No Arguments
The @code{getline} command can be used without arguments to read input
from the current input file. All it does in this case is read the next
input record and split it up into fields. This is useful if you've
finished processing the current record, but want to do some special
processing on the next record @emph{right now}. For example:
@c 6/2019: Thanks to Mark Krauze <daburashka@ya.ru> for suggested
@c improvements (the inner while loop).
@example
# Remove text between /* and */, inclusive
@{
while ((start = index($0, "/*")) != 0) @{
out = substr($0, 1, start - 1) # leading part of the string
rest = substr($0, start + 2) # ... */ ...
while ((end = index(rest, "*/")) == 0) @{ # is */ in trailing part?
# get more text
if (getline <= 0) @{
print("unexpected EOF or error:", ERRNO) > "/dev/stderr"
exit
@}
# build up the line using string concatenation
rest = rest $0
@}
rest = substr(rest, end + 2) # remove comment
# build up the output line using string concatenation
$0 = out rest
@}
print $0
@}
@end example
This @command{awk} program deletes C-style comments (@samp{/* @dots{}
*/}) from the input.
It uses a number of features we haven't covered yet, including
string concatenation
(@pxref{Concatenation})
and the @code{index()} and @code{substr()} built-in
functions
(@pxref{String Functions}).
By replacing the @samp{print $0} with other
statements, you could perform more complicated processing on the
decommented input, such as searching for matches of a regular
expression.
Here is some sample input:
@example
mon/*comment*/key
rab/*commen
t*/bit
horse /*comment*/more text
part 1 /*comment*/part 2 /*comment*/part 3
no comment
@end example
When run, the output is:
@example
$ @kbd{awk -f strip_comments.awk example_text}
@print{} monkey
@print{} rabbit
@print{} horse more text
@print{} part 1 part 2 part 3
@print{} no comment
@end example
This form of the @code{getline} command sets @code{NF},
@code{NR}, @code{FNR}, @code{RT}, and the value of @code{$0}.
@quotation NOTE
The new value of @code{$0} is used to test
the patterns of any subsequent rules. The original value
of @code{$0} that triggered the rule that executed @code{getline}
is lost.
By contrast, the @code{next} statement reads a new record
but immediately begins processing it normally, starting with the first
rule in the program. @xref{Next Statement}.
@end quotation
@node Getline/Variable
@subsection Using @code{getline} into a Variable
@cindex @code{getline} command @subentry into a variable
@cindex variables @subentry @code{getline} command into, using
You can use @samp{getline @var{var}} to read the next record from
@command{awk}'s input into the variable @var{var}. No other processing is
done.
For example, suppose the next line is a comment or a special string,
and you want to read it without triggering
any rules. This form of @code{getline} allows you to read that line
and store it in a variable so that the main
read-a-line-and-check-each-rule loop of @command{awk} never sees it.
The following example swaps every two lines of input:
@example
@group
@{
if ((getline tmp) > 0) @{
print tmp
print $0
@} else
print $0
@}
@end group
@end example
@noindent
It takes the following list:
@example
wan
tew
free
phore
@end example
@noindent
and produces these results:
@example
tew
wan
phore
free
@end example
The @code{getline} command used in this way sets only the variables
@code{NR}, @code{FNR}, and @code{RT} (and, of course, @var{var}).
The record is not
split into fields, so the values of the fields (including @code{$0}) and
the value of @code{NF} do not change.
@node Getline/File
@subsection Using @code{getline} from a File
@cindex @code{getline} command @subentry from a file
@cindex input redirection
@cindex redirection @subentry of input
@cindex @code{<} (left angle bracket) @subentry @code{<} operator (I/O)
@cindex left angle bracket (@code{<}) @subentry @code{<} operator (I/O)
@cindex operators @subentry input/output
Use @samp{getline < @var{file}} to read the next record from @var{file}.
Here, @var{file} is a string-valued expression that
specifies the @value{FN}. @samp{< @var{file}} is called a @dfn{redirection}
because it directs input to come from a different place.
For example, the following
program reads its input record from the file @file{secondary.input} when it
encounters a first field with a value equal to 10 in the current input
file:
@example
@{
if ($1 == 10) @{
getline < "secondary.input"
print
@} else
print
@}
@end example
Because the main input stream is not used, the values of @code{NR} and
@code{FNR} are not changed. However, the record it reads is split into fields in
the normal manner, so the values of @code{$0} and the other fields are
changed, resulting in a new value of @code{NF}.
@code{RT} is also set.
@cindex POSIX @command{awk} @subentry @code{<} operator and
@c Thanks to Paul Eggert for initial wording here
According to POSIX, @samp{getline < @var{expression}} is ambiguous if
@var{expression} contains unparenthesized operators other than
@samp{$}; for example, @samp{getline < dir "/" file} is ambiguous
because the concatenation operator (not discussed yet; @pxref{Concatenation})
is not parenthesized. You should write it as @samp{getline < (dir "/" file)} if
you want your program to be portable to all @command{awk} implementations.
@node Getline/Variable/File
@subsection Using @code{getline} into a Variable from a File
@cindex variables @subentry @code{getline} command into, using
Use @samp{getline @var{var} < @var{file}} to read input
from the file
@var{file}, and put it in the variable @var{var}. As earlier, @var{file}
is a string-valued expression that specifies the file from which to read.
In this version of @code{getline}, none of the predefined variables are
changed and the record is not split into fields. The only variable
changed is @var{var}.@footnote{This is not quite true. @code{RT} could
be changed if @code{RS} is a regular expression.}
For example, the following program copies all the input files to the
output, except for records that say @w{@samp{@@include @var{filename}}}.
Such a record is replaced by the contents of the file
@var{filename}:
@example
@{
if (NF == 2 && $1 == "@@include") @{
while ((getline line < $2) > 0)
print line
close($2)
@} else
print
@}
@end example
Note here how the name of the extra input file is not built into
the program; it is taken directly from the data, specifically from the second field on
the @code{@@include} line.
The @code{close()} function is called to ensure that if two identical
@code{@@include} lines appear in the input, the entire specified file is
included twice.
@xref{Close Files And Pipes}.
One deficiency of this program is that it does not process nested
@code{@@include} statements
(i.e., @code{@@include} statements in included files)
the way a true macro preprocessor would.
@xref{Igawk Program} for a program
that does handle nested @code{@@include} statements.
@node Getline/Pipe
@subsection Using @code{getline} from a Pipe
@c From private email, dated October 2, 1988. Used by permission, March 2013.
@cindex Kernighan, Brian
@quotation
@i{Omniscience has much to recommend it.
Failing that, attention to details would be useful.}
@author Brian Kernighan
@end quotation
@cindex @code{|} (vertical bar) @subentry @code{|} operator (I/O)
@cindex vertical bar (@code{|}) @subentry @code{|} operator (I/O)
@cindex input pipeline
@cindex pipe @subentry input
@cindex operators @subentry input/output
The output of a command can also be piped into @code{getline}, using
@samp{@var{command} | getline}. In
this case, the string @var{command} is run as a shell command and its output
is piped into @command{awk} to be used as input. This form of @code{getline}
reads one record at a time from the pipe.
For example, the following program copies its input to its output, except for
lines that begin with @samp{@@execute}, which are replaced by the output
produced by running the rest of the line as a shell command:
@example
@group
@{
if ($1 == "@@execute") @{
tmp = substr($0, 10) # Remove "@@execute"
while ((tmp | getline) > 0)
print
close(tmp)
@} else
print
@}
@end group
@end example
@noindent
The @code{close()} function is called to ensure that if two identical
@samp{@@execute} lines appear in the input, the command is run for
each one.
@ifnottex
@ifnotdocbook
@xref{Close Files And Pipes}.
@end ifnotdocbook
@end ifnottex
@c This example is unrealistic, since you could just use system
Given the input:
@example
foo
bar
baz
@@execute who
bletch
@end example
@noindent
the program might produce:
@cindex Robbins @subentry Bill
@cindex Robbins @subentry Miriam
@cindex Robbins @subentry Arnold
@example
foo
bar
baz
arnold ttyv0 Jul 13 14:22
miriam ttyp0 Jul 13 14:23 (murphy:0)
bill ttyp1 Jul 13 14:23 (murphy:0)
bletch
@end example
@noindent
Notice that this program ran the command @command{who} and printed the result.
(If you try this program yourself, you will of course get different results,
depending upon who is logged in on your system.)
This variation of @code{getline} splits the record into fields, sets the
value of @code{NF}, and recomputes the value of @code{$0}. The values of
@code{NR} and @code{FNR} are not changed.
@code{RT} is set.
@cindex POSIX @command{awk} @subentry @code{|} I/O operator and
@c Thanks to Paul Eggert for initial wording here
According to POSIX, @samp{@var{expression} | getline} is ambiguous if
@var{expression} contains unparenthesized operators other than
@samp{$}---for example, @samp{@w{"echo "} "date" | getline} is ambiguous
because the concatenation operator is not parenthesized. You should
write it as @samp{(@w{"echo "} "date") | getline} if you want your program
to be portable to all @command{awk} implementations.
@cindex Brian Kernighan's @command{awk}
@cindex @command{mawk} utility
@quotation NOTE
Unfortunately, @command{gawk} has not been consistent in its treatment
of a construct like @samp{@w{"echo "} "date" | getline}.
Most versions, including the current version, treat it as
@samp{@w{("echo "} "date") | getline}.
(This is also how BWK @command{awk} behaves.)
Some versions instead treat it as
@samp{@w{"echo "} ("date" | getline)}.
(This is how @command{mawk} behaves.)
In short, @emph{always} use explicit parentheses, and then you won't
have to worry.
@end quotation
@node Getline/Variable/Pipe
@subsection Using @code{getline} into a Variable from a Pipe
@cindex variables @subentry @code{getline} command into, using
When you use @samp{@var{command} | getline @var{var}}, the
output of @var{command} is sent through a pipe to
@code{getline} and into the variable @var{var}. For example, the
following program reads the current date and time into the variable
@code{current_time}, using the @command{date} utility, and then
prints it:
@example
BEGIN @{
"date" | getline current_time
close("date")
print "Report printed on " current_time
@}
@end example
In this version of @code{getline}, none of the predefined variables are
changed and the record is not split into fields. However, @code{RT} is set.
@ifinfo
@c Thanks to Paul Eggert for initial wording here
According to POSIX, @samp{@var{expression} | getline @var{var}} is ambiguous if
@var{expression} contains unparenthesized operators other than
@samp{$}; for example, @samp{@w{"echo "} "date" | getline @var{var}} is ambiguous
because the concatenation operator is not parenthesized. You should
write it as @samp{(@w{"echo "} "date") | getline @var{var}} if you want your
program to be portable to other @command{awk} implementations.
@end ifinfo
@node Getline/Coprocess
@subsection Using @code{getline} from a Coprocess
@cindex coprocesses @subentry @code{getline} from
@cindex @code{getline} command @subentry coprocesses, using from
@cindex @code{|} (vertical bar) @subentry @code{|&} operator (I/O)
@cindex vertical bar (@code{|}) @subentry @code{|&} operator (I/O)
@cindex operators @subentry input/output
@cindex differences in @command{awk} and @command{gawk} @subentry input/output operators
Reading input into @code{getline} from a pipe is a one-way operation.
The command that is started with @samp{@var{command} | getline} only
sends data @emph{to} your @command{awk} program.
On occasion, you might want to send data to another program
for processing and then read the results back.
@command{gawk} allows you to start a @dfn{coprocess}, with which two-way
communications are possible. This is done with the @samp{|&}
operator.
Typically, you write data to the coprocess first and then
read the results back, as shown in the following:
@example
print "@var{some query}" |& "db_server"
"db_server" |& getline
@end example
@noindent
which sends a query to @command{db_server} and then reads the results.
The values of @code{NR} and
@code{FNR} are not changed,
because the main input stream is not used.
However, the record is split into fields in
the normal manner, thus changing the values of @code{$0}, of the other fields,
and of @code{NF} and @code{RT}.
Coprocesses are an advanced feature. They are discussed here only because
this is the @value{SECTION} on @code{getline}.
@xref{Two-way I/O},
where coprocesses are discussed in more detail.
@node Getline/Variable/Coprocess
@subsection Using @code{getline} into a Variable from a Coprocess
@cindex variables @subentry @code{getline} command into, using
When you use @samp{@var{command} |& getline @var{var}}, the output from
the coprocess @var{command} is sent through a two-way pipe to @code{getline}
and into the variable @var{var}.
In this version of @code{getline}, none of the predefined variables are
changed and the record is not split into fields. The only variable
changed is @var{var}.
However, @code{RT} is set.
@ifinfo
Coprocesses are an advanced feature. They are discussed here only because
this is the @value{SECTION} on @code{getline}.
@xref{Two-way I/O},
where coprocesses are discussed in more detail.
@end ifinfo
@node Getline Notes
@subsection Points to Remember About @code{getline}
Here are some miscellaneous points about @code{getline} that
you should bear in mind:
@itemize @value{BULLET}
@item
When @code{getline} changes the value of @code{$0} and @code{NF},
@command{awk} does @emph{not} automatically jump to the start of the
program and start testing the new record against every pattern.
However, the new record is tested against any subsequent rules.
@cindex differences in @command{awk} and @command{gawk} @subentry implementation limitations
@cindex implementation issues, @command{gawk} @subentry limits
@cindex @command{awk} @subentry implementations @subentry limits
@cindex @command{gawk} @subentry implementation issues @subentry limits
@item
Some very old @command{awk} implementations limit the number of pipelines that an @command{awk}
program may have open to just one. In @command{gawk}, there is no such limit.
You can open as many pipelines (and coprocesses) as the underlying operating
system permits.
@cindex side effects @subentry @code{FILENAME} variable
@cindex @code{FILENAME} variable @subentry @code{getline}, setting with
@cindex dark corner @subentry @code{FILENAME} variable
@cindex @code{getline} command @subentry @code{FILENAME} variable and
@cindex @code{BEGIN} pattern @subentry @code{getline} and
@item
An interesting side effect occurs if you use @code{getline} without a
redirection inside a @code{BEGIN} rule. Because an unredirected @code{getline}
reads from the command-line @value{DF}s, the first @code{getline} command
causes @command{awk} to set the value of @code{FILENAME}. Normally,
@code{FILENAME} does not have a value inside @code{BEGIN} rules, because you
have not yet started to process the command-line @value{DF}s.
@value{DARKCORNER}
(See @ref{BEGIN/END};
also @pxref{Auto-set}.)
@item
Using @code{FILENAME} with @code{getline}
(@samp{getline < FILENAME})
is likely to be a source of
confusion. @command{awk} opens a separate input stream from the
current input file. However, by not using a variable, @code{$0}
and @code{NF} are still updated. If you're doing this, it's
probably by accident, and you should reconsider what it is you're
trying to accomplish.
@item
@ifdocbook
The next @value{SECTION}
@end ifdocbook
@ifnotdocbook
@ref{Getline Summary},
@end ifnotdocbook
presents a table summarizing the
@code{getline} variants and which variables they can affect.
It is worth noting that those variants that do not use redirection
can cause @code{FILENAME} to be updated if they cause
@command{awk} to start reading a new input file.
@item
@cindex Moore, Duncan
If the variable being assigned is an expression with side effects,
different versions of @command{awk} behave differently upon encountering
end-of-file. Some versions don't evaluate the expression; many versions
(including @command{gawk}) do. Here is an example, courtesy of Duncan Moore:
@ignore
Date: Sun, 01 Apr 2012 11:49:33 +0100
From: Duncan Moore <duncan.moore@@gmx.com>
@end ignore
@example
BEGIN @{
system("echo 1 > f")
while ((getline a[++c] < "f") > 0) @{ @}
print c
@}
@end example
@noindent
Here, the side effect is the @samp{++c}. Is @code{c} incremented if
end-of-file is encountered before the element in @code{a} is assigned?
@command{gawk} treats @code{getline} like a function call, and evaluates
the expression @samp{a[++c]} before attempting to read from @file{f}.
However, some versions of @command{awk} only evaluate the expression once they
know that there is a string value to be assigned.
@end itemize
@node Getline Summary
@subsection Summary of @code{getline} Variants
@cindex @code{getline} command @subentry variants
@ref{table-getline-variants}
summarizes the eight variants of @code{getline},
listing which predefined variables are set by each one,
and whether the variant is standard or a @command{gawk} extension.
Note: for each variant, @command{gawk} sets the @code{RT} predefined variable.
@float Table,table-getline-variants
@caption{@code{getline} variants and what they set}
@multitable @columnfractions .33 .38 .27
@headitem Variant @tab Effect @tab @command{awk} / @command{gawk}
@item @code{getline} @tab Sets @code{$0}, @code{NF}, @code{FNR}, @code{NR}, and @code{RT} @tab @command{awk}
@item @code{getline} @var{var} @tab Sets @var{var}, @code{FNR}, @code{NR}, and @code{RT} @tab @command{awk}
@item @code{getline <} @var{file} @tab Sets @code{$0}, @code{NF}, and @code{RT} @tab @command{awk}
@item @code{getline @var{var} < @var{file}} @tab Sets @var{var} and @code{RT} @tab @command{awk}
@item @var{command} @code{| getline} @tab Sets @code{$0}, @code{NF}, and @code{RT} @tab @command{awk}
@item @var{command} @code{| getline} @var{var} @tab Sets @var{var} and @code{RT} @tab @command{awk}
@item @var{command} @code{|& getline} @tab Sets @code{$0}, @code{NF}, and @code{RT} @tab @command{gawk}
@item @var{command} @code{|& getline} @var{var} @tab Sets @var{var} and @code{RT} @tab @command{gawk}
@end multitable
@end float
@node Read Timeout
@section Reading Input with a Timeout
@cindex timeout, reading input
@cindex differences in @command{awk} and @command{gawk} @subentry read timeouts
This @value{SECTION} describes a feature that is specific to @command{gawk}.
You may specify a timeout in milliseconds for reading input from the keyboard,
a pipe, or two-way communication, including TCP/IP sockets. This can be done
on a per-input, per-command, or per-connection basis, by setting a special
element in the @code{PROCINFO} array (@pxref{Auto-set}):
@example
PROCINFO["input_name", "READ_TIMEOUT"] = @var{timeout in milliseconds}
@end example
When set, this causes @command{gawk} to time out and return failure
if no data is available to read within the specified timeout period.
For example, a TCP client can decide to give up on receiving
any response from the server after a certain amount of time:
@example
@group
Service = "/inet/tcp/0/localhost/daytime"
PROCINFO[Service, "READ_TIMEOUT"] = 100
if ((Service |& getline) > 0)
print $0
else if (ERRNO != "")
print ERRNO
@end group
@end example
Here is how to read interactively from the user@footnote{This assumes
that standard input is the keyboard.} without waiting
for more than five seconds:
@example
PROCINFO["/dev/stdin", "READ_TIMEOUT"] = 5000
while ((getline < "/dev/stdin") > 0)
print $0
@end example
@command{gawk} terminates the read operation if input does not
arrive after waiting for the timeout period, returns failure,
and sets @code{ERRNO} to an appropriate string value.
A negative or zero value for the timeout is the same as specifying
no timeout at all.
A timeout can also be set for reading from the keyboard in the implicit
loop that reads input records and matches them against patterns,
like so:
@example
$ @kbd{gawk 'BEGIN @{ PROCINFO["-", "READ_TIMEOUT"] = 5000 @}}
> @kbd{@{ print "You entered: " $0 @}'}
@kbd{gawk}
@print{} You entered: gawk
@end example
In this case, failure to respond within five seconds results in the following
error message:
@example
@error{} gawk: cmd. line:2: (FILENAME=- FNR=1) fatal: error reading input file `-': Connection timed out
@end example
The timeout can be set or changed at any time, and will take effect on the
next attempt to read from the input device. In the following example,
we start with a timeout value of one second, and progressively
reduce it by one-tenth of a second until we wait indefinitely
for the input to arrive:
@example
PROCINFO[Service, "READ_TIMEOUT"] = 1000
while ((Service |& getline) > 0) @{
print $0
PROCINFO[Service, "READ_TIMEOUT"] -= 100
@}
@end example
@quotation NOTE
You should not assume that the read operation will block
exactly after the tenth record has been printed. It is possible that
@command{gawk} will read and buffer more than one record's
worth of data the first time. Because of this, changing the value
of timeout like in the preceding example is not very useful.
@end quotation
@cindex @env{GAWK_READ_TIMEOUT} environment variable
@cindex environment variables @subentry @env{GAWK_READ_TIMEOUT}
If the @code{PROCINFO} element is not present and the
@env{GAWK_READ_TIMEOUT} environment variable exists,
@command{gawk} uses its value to initialize the timeout value.
The exclusive use of the environment variable to specify timeout
has the disadvantage of not being able to control it
on a per-command or per-connection basis.
@command{gawk} considers a timeout event to be an error even though
the attempt to read from the underlying device may
succeed in a later attempt. This is a limitation, and it also
means that you cannot use this to multiplex input from
two or more sources. @xref{Retrying Input} for a way to enable
later I/O attempts to succeed.
Assigning a timeout value prevents read operations from
blocking indefinitely. But bear in mind that there are other ways
@command{gawk} can stall waiting for an input device to be ready.
A network client can sometimes take a long time to establish
a connection before it can start reading any data,
or the attempt to open a FIFO special file for reading can block
indefinitely until some other process opens it for writing.
@node Retrying Input
@section Retrying Reads After Certain Input Errors
@cindex retrying input
@cindex differences in @command{awk} and @command{gawk} @subentry retrying input
This @value{SECTION} describes a feature that is specific to @command{gawk}.
When @command{gawk} encounters an error while reading input, by
default @code{getline} returns @minus{}1, and subsequent attempts to
read from that file result in an end-of-file indication. However, you
may optionally instruct @command{gawk} to allow I/O to be retried when
certain errors are encountered by setting a special element in
the @code{PROCINFO} array (@pxref{Auto-set}):
@example
PROCINFO["@var{input_name}", "RETRY"] = 1
@end example
When this element exists, @command{gawk} checks the value of the system
(C language)
@code{errno} variable when an I/O error occurs. If @code{errno} indicates
a subsequent I/O attempt may succeed, @code{getline} instead returns
@minus{}2 and
further calls to @code{getline} may succeed. This applies to the @code{errno}
values @code{EAGAIN}, @code{EWOULDBLOCK}, @code{EINTR}, or @code{ETIMEDOUT}.
This feature is useful in conjunction with
@code{PROCINFO["@var{input_name}", "READ_TIMEOUT"]} or situations where a file
descriptor has been configured to behave in a non-blocking fashion.
@node Command-line directories
@section Directories on the Command Line
@cindex differences in @command{awk} and @command{gawk} @subentry command-line directories
@cindex directories @subentry command-line
@cindex command line @subentry directories on
According to the POSIX standard, files named on the @command{awk}
command line must be text files; it is a fatal error if they are not.
Most versions of @command{awk} treat a directory on the command line as
a fatal error.
By default, @command{gawk} produces a warning for a directory on the
command line, but otherwise ignores it. This makes it easier to use
shell wildcards with your @command{awk} program:
@example
$ @kbd{gawk -f whizprog.awk *} @ii{Directories could kill this program}
@end example
If either of the @option{--posix}
or @option{--traditional} options is given, then @command{gawk} reverts
to treating a directory on the command line as a fatal error.
@xref{Extension Sample Readdir} for a way to treat directories
as usable data from an @command{awk} program.
@node Input Summary
@section Summary
@itemize @value{BULLET}
@item
Input is split into records based on the value of @code{RS}.
The possibilities are as follows:
@multitable @columnfractions .25 .35 .40
@headitem Value of @code{RS} @tab Records are split on @dots{} @tab @command{awk} / @command{gawk}
@item Any single character @tab That character @tab @command{awk}
@item The empty string (@code{""}) @tab Runs of two or more newlines @tab @command{awk}
@item A regexp @tab Text that matches the regexp @tab @command{gawk}
@end multitable
@item
@code{FNR} indicates how many records have been read from the current input file;
@code{NR} indicates how many records have been read in total.
@item
@command{gawk} sets @code{RT} to the text matched by @code{RS}.
@item
After splitting the input into records, @command{awk} further splits
the records into individual fields, named @code{$1}, @code{$2}, and so
on. @code{$0} is the whole record, and @code{NF} indicates how many
fields there are. The default way to split fields is between whitespace
characters.
@item
Fields may be referenced using a variable, as in @code{$NF}. Fields
may also be assigned values, which causes the value of @code{$0} to be
recomputed when it is later referenced. Assigning to a field with a number
greater than @code{NF} creates the field and rebuilds the record, using
@code{OFS} to separate the fields. Incrementing @code{NF} does the same
thing. Decrementing @code{NF} throws away fields and rebuilds the record.
@item
Field splitting is more complicated than record splitting:
@multitable @columnfractions .40 .40 .20
@headitem Field separator value @tab Fields are split @dots{} @tab @command{awk} / @command{gawk}
@item @code{FS == " "} @tab On runs of whitespace @tab @command{awk}
@item @code{FS == @var{any single character}} @tab On that character @tab @command{awk}
@item @code{FS == @var{regexp}} @tab On text matching the regexp @tab @command{awk}
@item @code{FS == ""} @tab Such that each individual character is a separate field @tab @command{gawk}
@item @code{FIELDWIDTHS == @var{list of columns}} @tab Based on character position @tab @command{gawk}
@item @code{FPAT == @var{regexp}} @tab On the text surrounding text matching the regexp @tab @command{gawk}
@end multitable
@item
Using @samp{FS = "\n"} causes the entire record to be a single field
(assuming that newlines separate records).
@item
@code{FS} may be set from the command line using the @option{-F} option.
This can also be done using command-line variable assignment.
@item
Use @code{PROCINFO["FS"]} to see how fields are being split.
@item
Use @code{getline} in its various forms to read additional records
from the default input stream, from a file, or from a pipe or coprocess.
@item
Use @code{PROCINFO[@var{file}, "READ_TIMEOUT"]} to cause reads to time out
for @var{file}.
@cindex POSIX mode
@item
Directories on the command line are fatal for standard @command{awk};
@command{gawk} ignores them if not in POSIX mode.
@end itemize
@c EXCLUDE START
@node Input Exercises
@section Exercises
@enumerate
@item
Using the @code{FIELDWIDTHS} variable (@pxref{Constant Size}),
write a program to read election data, where each record represents
one voter's votes. Come up with a way to define which columns are
associated with each ballot item, and print the total votes,
including abstentions, for each item.
@end enumerate
@c EXCLUDE END
@node Printing
@chapter Printing Output
@cindex printing
@cindex output, printing @seeentry{printing}
One of the most common programming actions is to @dfn{print}, or output,
some or all of the input. Use the @code{print} statement
for simple output, and the @code{printf} statement
for fancier formatting.
The @code{print} statement is not limited when
computing @emph{which} values to print. However, with two exceptions,
you cannot specify @emph{how} to print them---how many
columns, whether to use exponential notation or not, and so on.
(For the exceptions, @pxref{Output Separators} and
@ref{OFMT}.)
For printing with specifications, you need the @code{printf} statement
(@pxref{Printf}).
@cindex @code{print} statement
@cindex @code{printf} statement
Besides basic and formatted printing, this @value{CHAPTER}
also covers I/O redirections to files and pipes, introduces
the special @value{FN}s that @command{gawk} processes internally,
and discusses the @code{close()} built-in function.
@menu
* Print:: The @code{print} statement.
* Print Examples:: Simple examples of @code{print} statements.
* Output Separators:: The output separators and how to change them.
* OFMT:: Controlling Numeric Output With @code{print}.
* Printf:: The @code{printf} statement.
* Redirection:: How to redirect output to multiple files and
pipes.
* Special FD:: Special files for I/O.
* Special Files:: File name interpretation in @command{gawk}.
@command{gawk} allows access to inherited file
descriptors.
* Close Files And Pipes:: Closing Input and Output Files and Pipes.
* Nonfatal:: Enabling Nonfatal Output.
* Output Summary:: Output summary.
* Output Exercises:: Exercises.
@end menu
@node Print
@section The @code{print} Statement
Use the @code{print} statement to produce output with simple, standardized
formatting. You specify only the strings or numbers to print, in a
list separated by commas. They are output, separated by single spaces,
followed by a newline. The statement looks like this:
@example
print @var{item1}, @var{item2}, @dots{}
@end example
@noindent
The entire list of items may be optionally enclosed in parentheses. The
parentheses are necessary if any of the item expressions uses the @samp{>}
relational operator; otherwise it could be confused with an output redirection
(@pxref{Redirection}).
The items to print can be constant strings or numbers, fields of the
current record (such as @code{$1}), variables, or any @command{awk}
expression. Numeric values are converted to strings and then printed.
@cindex records @subentry printing
@cindex lines @subentry blank, printing
@cindex text, printing
The simple statement @samp{print} with no items is equivalent to
@samp{print $0}: it prints the entire current record. To print a blank
line, use @samp{print ""}.
To print a fixed piece of text, use a string constant, such as
@w{@code{"Don't Panic"}}, as one item. If you forget to use the
double-quote characters, your text is taken as an @command{awk}
expression, and you will probably get an error. Keep in mind that a
space is printed between any two items.
Note that the @code{print} statement is a statement and not an
expression---you can't use it in the pattern part of a
pattern--action statement, for example.
@node Print Examples
@section @code{print} Statement Examples
Each @code{print} statement makes at least one line of output. However, it
isn't limited to only one line. If an item value is a string containing a
newline, the newline is output along with the rest of the string. A
single @code{print} statement can make any number of lines this way.
@cindex newlines @subentry printing
The following is an example of printing a string that contains embedded
@ifinfo
newlines
(the @samp{\n} is an escape sequence, used to represent the newline
character; @pxref{Escape Sequences}):
@end ifinfo
@ifhtml
newlines
(the @samp{\n} is an escape sequence, used to represent the newline
character; @pxref{Escape Sequences}):
@end ifhtml
@ifnotinfo
@ifnothtml
newlines:
@end ifnothtml
@end ifnotinfo
@example
@group
$ @kbd{awk 'BEGIN @{ print "line one\nline two\nline three" @}'}
@print{} line one
@print{} line two
@print{} line three
@end group
@end example
@cindex fields @subentry printing
The next example, which is run on the @file{inventory-shipped} file,
prints the first two fields of each input record, with a space between
them:
@example
$ @kbd{awk '@{ print $1, $2 @}' inventory-shipped}
@print{} Jan 13
@print{} Feb 15
@print{} Mar 15
@dots{}
@end example
@cindex @code{print} statement @subentry commas, omitting
@cindex troubleshooting @subentry @code{print} statement, omitting commas
A common mistake in using the @code{print} statement is to omit the comma
between two items. This often has the effect of making the items run
together in the output, with no space. The reason for this is that
juxtaposing two string expressions in @command{awk} means to concatenate
them. Here is the same program, without the comma:
@example
$ @kbd{awk '@{ print $1 $2 @}' inventory-shipped}
@print{} Jan13
@print{} Feb15
@print{} Mar15
@dots{}
@end example
@cindex @code{BEGIN} pattern @subentry headings, adding
To someone unfamiliar with the @file{inventory-shipped} file, neither
example's output makes much sense. A heading line at the beginning
would make it clearer. Let's add some headings to our table of months
(@code{$1}) and green crates shipped (@code{$2}). We do this using
a @code{BEGIN} rule (@pxref{BEGIN/END}) so that the headings are only
printed once:
@example
awk 'BEGIN @{ print "Month Crates"
print "----- ------" @}
@{ print $1, $2 @}' inventory-shipped
@end example
@noindent
When run, the program prints the following:
@example
Month Crates
----- ------
Jan 13
Feb 15
Mar 15
@dots{}
@end example
@noindent
The only problem, however, is that the headings and the table data
don't line up! We can fix this by printing some spaces between the
two fields:
@example
@group
awk 'BEGIN @{ print "Month Crates"
print "----- ------" @}
@{ print $1, " ", $2 @}' inventory-shipped
@end group
@end example
@cindex @code{printf} statement @subentry columns, aligning
@cindex columns @subentry aligning
Lining up columns this way can get pretty
complicated when there are many columns to fix. Counting spaces for two
or three columns is simple, but any more than this can take up
a lot of time. This is why the @code{printf} statement was
created (@pxref{Printf});
one of its specialties is lining up columns of data.
@cindex line continuations @subentry in @code{print} statement
@cindex @code{print} statement @subentry line continuations and
@quotation NOTE
You can continue either a @code{print} or
@code{printf} statement simply by putting a newline after any comma
(@pxref{Statements/Lines}).
@end quotation
@node Output Separators
@section Output Separators
@cindex @code{OFS} variable
As mentioned previously, a @code{print} statement contains a list
of items separated by commas. In the output, the items are normally
separated by single spaces. However, this doesn't need to be the case;
a single space is simply the default. Any string of
characters may be used as the @dfn{output field separator} by setting the
predefined variable @code{OFS}. The initial value of this variable
is the string @w{@code{" "}} (i.e., a single space).
The output from an entire @code{print} statement is called an @dfn{output
record}. Each @code{print} statement outputs one output record, and
then outputs a string called the @dfn{output record separator} (or
@code{ORS}). The initial value of @code{ORS} is the string @code{"\n"}
(i.e., a newline character). Thus, each @code{print} statement normally
makes a separate line.
@cindex output @subentry records
@cindex output record separator @seeentry{@code{ORS} variable}
@cindex @code{ORS} variable
@cindex @code{BEGIN} pattern @subentry @code{OFS}/@code{ORS} variables, assigning values to
In order to change how output fields and records are separated, assign
new values to the variables @code{OFS} and @code{ORS}. The usual
place to do this is in the @code{BEGIN} rule
(@pxref{BEGIN/END}), so
that it happens before any input is processed. It can also be done
with assignments on the command line, before the names of the input
files, or using the @option{-v} command-line option
(@pxref{Options}).
The following example prints the first and second fields of each input
record, separated by a semicolon, with a blank line added after each
newline:
@example
$ @kbd{awk 'BEGIN @{ OFS = ";"; ORS = "\n\n" @}}
> @kbd{@{ print $1, $2 @}' mail-list}
@print{} Amelia;555-5553
@print{}
@print{} Anthony;555-3412
@print{}
@print{} Becky;555-7685
@print{}
@print{} Bill;555-1675
@print{}
@print{} Broderick;555-0542
@print{}
@print{} Camilla;555-2912
@print{}
@print{} Fabius;555-1234
@print{}
@print{} Julie;555-6699
@print{}
@print{} Martin;555-6480
@print{}
@print{} Samuel;555-3430
@print{}
@print{} Jean-Paul;555-2127
@print{}
@end example
If the value of @code{ORS} does not contain a newline, the program's output
runs together on a single line.
@node OFMT
@section Controlling Numeric Output with @code{print}
@cindex numeric @subentry output format
@cindex formats, numeric output
When printing numeric values with the @code{print} statement,
@command{awk} internally converts each number to a string of characters
and prints that string. @command{awk} uses the @code{sprintf()} function
to do this conversion
(@pxref{String Functions}).
For now, it suffices to say that the @code{sprintf()}
function accepts a @dfn{format specification} that tells it how to format
numbers (or strings), and that there are a number of different ways in which
numbers can be formatted. The different format specifications are discussed
more fully in
@ref{Control Letters}.
@cindexawkfunc{sprintf}
@cindex @code{OFMT} variable
@cindex output @subentry format specifier, @code{OFMT}
The predefined variable @code{OFMT} contains the format specification
that @code{print} uses with @code{sprintf()} when it wants to convert a
number to a string for printing.
The default value of @code{OFMT} is @code{"%.6g"}.
The way @code{print} prints numbers can be changed
by supplying a different format specification
for the value of @code{OFMT}, as shown in the following example:
@example
$ @kbd{awk 'BEGIN @{}
> @kbd{OFMT = "%.0f" # print numbers as integers (rounds)}
> @kbd{print 17.23, 17.54 @}'}
@print{} 17 18
@end example
@noindent
@cindex dark corner @subentry @code{OFMT} variable
@cindex POSIX @command{awk} @subentry @code{OFMT} variable and
@cindex @code{OFMT} variable @subentry POSIX @command{awk} and
According to the POSIX standard, @command{awk}'s behavior is undefined
if @code{OFMT} contains anything but a floating-point conversion specification.
@value{DARKCORNER}
@node Printf
@section Using @code{printf} Statements for Fancier Printing
@cindex @code{printf} statement
@cindex output @subentry formatted
@cindex formatting @subentry output
For more precise control over the output format than what is
provided by @code{print}, use @code{printf}.
With @code{printf} you can
specify the width to use for each item, as well as various
formatting choices for numbers (such as what output base to use, whether to
print an exponent, whether to print a sign, and how many digits to print
after the decimal point).
@menu
* Basic Printf:: Syntax of the @code{printf} statement.
* Control Letters:: Format-control letters.
* Format Modifiers:: Format-specification modifiers.
* Printf Examples:: Several examples.
@end menu
@node Basic Printf
@subsection Introduction to the @code{printf} Statement
@cindex @code{printf} statement @subentry syntax of
A simple @code{printf} statement looks like this:
@example
printf @var{format}, @var{item1}, @var{item2}, @dots{}
@end example
@noindent
As for @code{print}, the entire list of arguments may optionally be
enclosed in parentheses. Here too, the parentheses are necessary if any
of the item expressions uses the @samp{>} relational operator; otherwise,
it can be confused with an output redirection (@pxref{Redirection}).
@cindex format specifiers
The difference between @code{printf} and @code{print} is the @var{format}
argument. This is an expression whose value is taken as a string; it
specifies how to output each of the other arguments. It is called the
@dfn{format string}.
The format string is very similar to that in the ISO C library function
@code{printf()}. Most of @var{format} is text to output verbatim.
Scattered among this text are @dfn{format specifiers}---one per item.
Each format specifier says to output the next item in the argument list
at that place in the format.
The @code{printf} statement does not automatically append a newline
to its output. It outputs only what the format string specifies.
So if a newline is needed, you must include one in the format string.
The output separator variables @code{OFS} and @code{ORS} have no effect
on @code{printf} statements. For example:
@example
@group
$ @kbd{awk 'BEGIN @{}
> @kbd{ORS = "\nOUCH!\n"; OFS = "+"}
> @kbd{msg = "Don\47t Panic!"}
> @kbd{printf "%s\n", msg}
> @kbd{@}'}
@print{} Don't Panic!
@end group
@end example
@noindent
Here, neither the @samp{+} nor the @samp{OUCH!} appears in
the output message.
@node Control Letters
@subsection Format-Control Letters
@cindex @code{printf} statement @subentry format-control characters
@cindex format specifiers @subentry @code{printf} statement
A format specifier starts with the character @samp{%} and ends with
a @dfn{format-control letter}---it tells the @code{printf} statement
how to output one item. The format-control letter specifies what @emph{kind}
of value to print. The rest of the format specifier is made up of
optional @dfn{modifiers} that control @emph{how} to print the value, such as
the field width. Here is a list of the format-control letters:
@c @asis for docbook to come out right
@table @asis
@item @code{%a}, @code{%A}
A floating point number of the form
[@code{-}]@code{0x@var{h}.@var{hhhh}p+-@var{dd}}
(C99 hexadecimal floating point format).
For @code{%A},
uppercase letters are used instead of lowercase ones.
@quotation NOTE
The current POSIX standard requires support for @code{%a} and @code{%A} in
@command{awk}. As far as we know, besides @command{gawk}, the only other
version of @command{awk} that actually implements it is BWK @command{awk}.
It's use is thus highly nonportable!
Furthermore, these formats are not available on any system where the
underlying C library @code{printf()} function does not support them. As
of this writing, among current systems, only OpenVMS is known to not
support them.
@end quotation
@item @code{%c}
Print a number as a character; thus, @samp{printf "%c",
65} outputs the letter @samp{A}. The output for a string value is
the first character of the string.
@cindex dark corner @subentry format-control characters
@cindex @command{gawk} @subentry format-control characters
@quotation NOTE
The POSIX standard says the first character of a string is printed.
In locales with multibyte characters, @command{gawk} attempts to
convert the leading bytes of the string into a valid wide character
and then to print the multibyte encoding of that character.
Similarly, when printing a numeric value, @command{gawk} allows the
value to be within the numeric range of values that can be held
in a wide character.
If the conversion to multibyte encoding fails, @command{gawk}
uses the low eight bits of the value as the character to print.
Other @command{awk} versions generally restrict themselves to printing
the first byte of a string or to numeric values within the range of
a single byte (0--255).
@value{DARKCORNER}
@end quotation
@item @code{%d}, @code{%i}
Print a decimal integer.
The two control letters are equivalent.
(The @samp{%i} specification is for compatibility with ISO C.)
@item @code{%e}, @code{%E}
Print a number in scientific (exponential) notation.
For example:
@example
printf "%4.3e\n", 1950
@end example
@noindent
prints @samp{1.950e+03}, with a total of four significant figures, three of
which follow the decimal point.
(The @samp{4.3} represents two modifiers,
discussed in the next @value{SUBSECTION}.)
@samp{%E} uses @samp{E} instead of @samp{e} in the output.
@item @code{%f}
Print a number in floating-point notation.
For example:
@example
printf "%4.3f", 1950
@end example
@noindent
prints @samp{1950.000}, with a minimum of four significant figures, three of
which follow the decimal point.
(The @samp{4.3} represents two modifiers,
discussed in the next @value{SUBSECTION}.)
On systems supporting IEEE 754 floating-point format, values
representing negative
infinity are formatted as
@samp{-inf} or @samp{-infinity},
and positive infinity as
@samp{inf} or @samp{infinity}.
The special ``not a number'' value formats as @samp{-nan} or @samp{nan}
(@pxref{Math Definitions}).
@item @code{%F}
Like @samp{%f}, but the infinity and ``not a number'' values are spelled
using uppercase letters.
The @samp{%F} format is a POSIX extension to ISO C; not all systems
support it. On those that don't, @command{gawk} uses @samp{%f} instead.
@item @code{%g}, @code{%G}
Print a number in either scientific notation or in floating-point
notation, whichever uses fewer characters; if the result is printed in
scientific notation, @samp{%G} uses @samp{E} instead of @samp{e}.
@item @code{%o}
Print an unsigned octal integer
(@pxref{Nondecimal-numbers}).
@item @code{%s}
Print a string.
@item @code{%u}
Print an unsigned decimal integer.
(This format is of marginal use, because all numbers in @command{awk}
are floating point; it is provided primarily for compatibility with C.)
@item @code{%x}, @code{%X}
Print an unsigned hexadecimal integer;
@samp{%X} uses the letters @samp{A} through @samp{F}
instead of @samp{a} through @samp{f}
(@pxref{Nondecimal-numbers}).
@item @code{%%}
Print a single @samp{%}.
This does not consume an
argument and it ignores any modifiers.
@end table
@cindex dark corner @subentry format-control characters
@cindex @command{gawk} @subentry format-control characters
@quotation NOTE
When using the integer format-control letters for values that are
outside the range of the widest C integer type, @command{gawk} switches to
the @samp{%g} format specifier. If @option{--lint} is provided on the
command line (@pxref{Options}), @command{gawk}
warns about this. Other versions of @command{awk} may print invalid
values or do something else entirely.
@value{DARKCORNER}
@end quotation
@quotation NOTE
The IEEE 754 standard for floating-point arithmetic allows for special
values that represent ``infinity'' (positive and negative) and values
that are ``not a number'' (NaN).
Input and output of these values occurs as text strings. This is
somewhat problematic for the @command{awk} language, which predates
the IEEE standard. Further details are provided in
@ref{POSIX Floating Point Problems}; please see there.
@end quotation
@node Format Modifiers
@subsection Modifiers for @code{printf} Formats
@cindex @code{printf} statement @subentry modifiers
@cindex modifiers, in format specifiers
A format specification can also include @dfn{modifiers} that can control
how much of the item's value is printed, as well as how much space it gets.
The modifiers come between the @samp{%} and the format-control letter.
We use the bullet symbol ``@bullet{}'' in the following examples to
represent
spaces in the output. Here are the possible modifiers, in the order in
which they may appear:
@table @asis
@cindex differences in @command{awk} and @command{gawk} @subentry @code{print}/@code{printf} statements
@cindex @code{printf} statement @subentry positional specifiers
@c the code{} does NOT start a secondary
@cindex positional specifiers, @code{printf} statement
@item @code{@var{N}$}
An integer constant followed by a @samp{$} is a @dfn{positional specifier}.
Normally, format specifications are applied to arguments in the order
given in the format string. With a positional specifier, the format
specification is applied to a specific argument, instead of what
would be the next argument in the list. Positional specifiers begin
counting with one. Thus:
@example
printf "%s %s\n", "don't", "panic"
printf "%2$s %1$s\n", "panic", "don't"
@end example
@noindent
prints the famous friendly message twice.
At first glance, this feature doesn't seem to be of much use.
It is in fact a @command{gawk} extension, intended for use in translating
messages at runtime.
@xref{Printf Ordering},
which describes how and why to use positional specifiers.
For now, we ignore them.
@item @code{-} (Minus)
The minus sign, used before the width modifier (see later on in
this list),
says to left-justify
the argument within its specified width. Normally, the argument
is printed right-justified in the specified width. Thus:
@example
printf "%-4s", "foo"
@end example
@noindent
prints @samp{foo@bullet{}}.
@item @var{space}
For numeric conversions, prefix positive values with a space and
negative values with a minus sign.
@item @code{+}
The plus sign, used before the width modifier (see later on in
this list),
says to always supply a sign for numeric conversions, even if the data
to format is positive. The @samp{+} overrides the space modifier.
@item @code{#}
Use an ``alternative form'' for certain control letters.
For @samp{%o}, supply a leading zero.
For @samp{%x} and @samp{%X}, supply a leading @samp{0x} or @samp{0X} for
a nonzero result.
For @samp{%e}, @samp{%E}, @samp{%f}, and @samp{%F}, the result always
contains a decimal point.
For @samp{%g} and @samp{%G}, trailing zeros are not removed from the result.
@item @code{0}
A leading @samp{0} (zero) acts as a flag indicating that output should be
padded with zeros instead of spaces.
This applies only to the numeric output formats.
This flag only has an effect when the field width is wider than the
value to print.
@item @code{'}
A single quote or apostrophe character is a POSIX extension to ISO C.
It indicates that the integer part of a floating-point value, or the
entire part of an integer decimal value, should have a thousands-separator
character in it. This only works in locales that support such characters.
For example:
@example
$ @kbd{cat thousands.awk} @ii{Show source program}
@print{} BEGIN @{ printf "%'d\n", 1234567 @}
$ @kbd{LC_ALL=C gawk -f thousands.awk}
@print{} 1234567 @ii{Results in} "C" @ii{locale}
$ @kbd{LC_ALL=en_US.UTF-8 gawk -f thousands.awk}
@print{} 1,234,567 @ii{Results in US English UTF locale}
@end example
@noindent
For more information about locales and internationalization issues,
see @ref{Locales}.
@quotation NOTE
The @samp{'} flag is a nice feature, but its use complicates things: it
becomes difficult to use it in command-line programs. For information
on appropriate quoting tricks, see @ref{Quoting}.
@end quotation
@item @var{width}
This is a number specifying the desired minimum width of a field. Inserting any
number between the @samp{%} sign and the format-control character forces the
field to expand to this width. The default way to do this is to
pad with spaces on the left. For example:
@example
printf "%4s", "foo"
@end example
@noindent
prints @samp{@bullet{}foo}.
The value of @var{width} is a minimum width, not a maximum. If the item
value requires more than @var{width} characters, it can be as wide as
necessary. Thus, the following:
@example
printf "%4s", "foobar"
@end example
@noindent
prints @samp{foobar}.
Preceding the @var{width} with a minus sign causes the output to be
padded with spaces on the right, instead of on the left.
@item @code{.@var{prec}}
A period followed by an integer constant
specifies the precision to use when printing.
The meaning of the precision varies by control letter:
@table @asis
@item @code{%d}, @code{%i}, @code{%o}, @code{%u}, @code{%x}, @code{%X}
Minimum number of digits to print.
@item @code{%e}, @code{%E}, @code{%f}, @code{%F}
Number of digits to the right of the decimal point.
@item @code{%g}, @code{%G}
Maximum number of significant digits.
@item @code{%s}
Maximum number of characters from the string that should print.
@end table
Thus, the following:
@example
printf "%.4s", "foobar"
@end example
@noindent
prints @samp{foob}.
@end table
The C library @code{printf}'s dynamic @var{width} and @var{prec}
capability (e.g., @code{"%*.*s"}) is supported. Instead of
supplying explicit @var{width} and/or @var{prec} values in the format
string, they are passed in the argument list. For example:
@example
w = 5
p = 3
s = "abcdefg"
printf "%*.*s\n", w, p, s
@end example
@noindent
is exactly equivalent to:
@example
s = "abcdefg"
printf "%5.3s\n", s
@end example
@noindent
Both programs output @samp{@w{@bullet{}@bullet{}abc}}.
Earlier versions of @command{awk} did not support this capability.
If you must use such a version, you may simulate this feature by using
concatenation to build up the format string, like so:
@example
w = 5
p = 3
s = "abcdefg"
printf "%" w "." p "s\n", s
@end example
@noindent
This is not particularly easy to read, but it does work.
@c @cindex lint checks
@cindex troubleshooting @subentry fatal errors @subentry @code{printf} format strings
@cindex POSIX @command{awk} @subentry @code{printf} format strings and
C programmers may be used to supplying additional modifiers (@samp{h},
@samp{j}, @samp{l}, @samp{L}, @samp{t}, and @samp{z}) in @code{printf}
format strings. These are not valid in @command{awk}. Most @command{awk}
implementations silently ignore them. If @option{--lint} is provided
on the command line (@pxref{Options}), @command{gawk} warns about their
use. If @option{--posix} is supplied, their use is a fatal error.
@node Printf Examples
@subsection Examples Using @code{printf}
The following simple example shows
how to use @code{printf} to make an aligned table:
@example
awk '@{ printf "%-10s %s\n", $1, $2 @}' mail-list
@end example
@noindent
This command
prints the names of the people (@code{$1}) in the file
@file{mail-list} as a string of 10 characters that are left-justified. It also
prints the phone numbers (@code{$2}) next on the line. This
produces an aligned two-column table of names and phone numbers,
as shown here:
@example
$ @kbd{awk '@{ printf "%-10s %s\n", $1, $2 @}' mail-list}
@print{} Amelia 555-5553
@print{} Anthony 555-3412
@print{} Becky 555-7685
@print{} Bill 555-1675
@print{} Broderick 555-0542
@print{} Camilla 555-2912
@print{} Fabius 555-1234
@print{} Julie 555-6699
@print{} Martin 555-6480
@print{} Samuel 555-3430
@print{} Jean-Paul 555-2127
@end example
In this case, the phone numbers had to be printed as strings because
the numbers are separated by dashes. Printing the phone numbers as
numbers would have produced just the first three digits: @samp{555}.
This would have been pretty confusing.
It wasn't necessary to specify a width for the phone numbers because
they are last on their lines. They don't need to have spaces
after them.
The table could be made to look even nicer by adding headings to the
tops of the columns. This is done using a @code{BEGIN} rule
(@pxref{BEGIN/END})
so that the headers are only printed once, at the beginning of
the @command{awk} program:
@example
awk 'BEGIN @{ print "Name Number"
print "---- ------" @}
@{ printf "%-10s %s\n", $1, $2 @}' mail-list
@end example
The preceding example mixes @code{print} and @code{printf} statements in
the same program. Using just @code{printf} statements can produce the
same results:
@example
awk 'BEGIN @{ printf "%-10s %s\n", "Name", "Number"
printf "%-10s %s\n", "----", "------" @}
@{ printf "%-10s %s\n", $1, $2 @}' mail-list
@end example
@noindent
Printing each column heading with the same format specification
used for the column elements ensures that the headings
are aligned just like the columns.
The fact that the same format specification is used three times can be
emphasized by storing it in a variable, like this:
@example
awk 'BEGIN @{ format = "%-10s %s\n"
printf format, "Name", "Number"
printf format, "----", "------" @}
@{ printf format, $1, $2 @}' mail-list
@end example
@node Redirection
@section Redirecting Output of @code{print} and @code{printf}
@cindex output redirection
@cindex redirection @subentry of output
@cindex @option{--sandbox} option @subentry output redirection with @code{print} @subentry @code{printf}
So far, the output from @code{print} and @code{printf} has gone
to the standard
output, usually the screen. Both @code{print} and @code{printf} can
also send their output to other places.
This is called @dfn{redirection}.
@quotation NOTE
When @option{--sandbox} is specified (@pxref{Options}),
redirecting output to files, pipes, and coprocesses is disabled.
@end quotation
A redirection appears after the @code{print} or @code{printf} statement.
Redirections in @command{awk} are written just like redirections in shell
commands, except that they are written inside the @command{awk} program.
@c the commas here are part of the see also
@cindex @code{print} statement @seealso{redirection of output}
@cindex @code{printf} statement @seealso{redirection of output}
There are four forms of output redirection: output to a file, output
appended to a file, output through a pipe to another command, and output
to a coprocess. We show them all for the @code{print} statement,
but they work identically for @code{printf}:
@table @code
@cindex @code{>} (right angle bracket) @subentry @code{>} operator (I/O)
@cindex right angle bracket (@code{>}) @subentry @code{>} operator (I/O)
@cindex operators @subentry input/output
@item print @var{items} > @var{output-file}
This redirection prints the items into the output file named
@var{output-file}. The @value{FN} @var{output-file} can be any
expression. Its value is changed to a string and then used as a
@value{FN} (@pxref{Expressions}).
When this type of redirection is used, the @var{output-file} is erased
before the first output is written to it. Subsequent writes to the same
@var{output-file} do not erase @var{output-file}, but append to it.
(This is different from how you use redirections in shell scripts.)
If @var{output-file} does not exist, it is created. For example, here
is how an @command{awk} program can write a list of peoples' names to one
file named @file{name-list}, and a list of phone numbers to another file
named @file{phone-list}:
@example
$ @kbd{awk '@{ print $2 > "phone-list"}
> @kbd{print $1 > "name-list" @}' mail-list}
$ @kbd{cat phone-list}
@print{} 555-5553
@print{} 555-3412
@dots{}
$ @kbd{cat name-list}
@print{} Amelia
@print{} Anthony
@dots{}
@end example
@noindent
Each output file contains one name or number per line.
@cindex @code{>} (right angle bracket) @subentry @code{>>} operator (I/O)
@cindex right angle bracket (@code{>}) @subentry @code{>>} operator (I/O)
@item print @var{items} >> @var{output-file}
This redirection prints the items into the preexisting output file
named @var{output-file}. The difference between this and the
single-@samp{>} redirection is that the old contents (if any) of
@var{output-file} are not erased. Instead, the @command{awk} output is
appended to the file.
If @var{output-file} does not exist, then it is created.
@cindex @code{|} (vertical bar) @subentry @code{|} operator (I/O)
@cindex pipe @subentry output
@cindex output @subentry pipes
@item print @var{items} | @var{command}
It is possible to send output to another program through a pipe
instead of into a file. This redirection opens a pipe to
@var{command}, and writes the values of @var{items} through this pipe
to another process created to execute @var{command}.
The redirection argument @var{command} is actually an @command{awk}
expression. Its value is converted to a string whose contents give
the shell command to be run. For example, the following produces two
files, one unsorted list of peoples' names, and one list sorted in reverse
alphabetical order:
@ignore
10/2000:
This isn't the best style, since COMMAND is assigned for each
record. It's done to avoid overfull hboxes in TeX. Leave it
alone for now and let's hope no-one notices.
@end ignore
@example
@group
awk '@{ print $1 > "names.unsorted"
command = "sort -r > names.sorted"
print $1 | command @}' mail-list
@end group
@end example
The unsorted list is written with an ordinary redirection, while
the sorted list is written by piping through the @command{sort} utility.
The next example uses redirection to mail a message to the mailing
list @code{bug-system}. This might be useful when trouble is encountered
in an @command{awk} script run periodically for system maintenance:
@example
report = "mail bug-system"
print("Awk script failed:", $0) | report
print("at record number", FNR, "of", FILENAME) | report
close(report)
@end example
The @code{close()} function is called here because it's a good idea to close
the pipe as soon as all the intended output has been sent to it.
@xref{Close Files And Pipes}
for more information.
This example also illustrates the use of a variable to represent
a @var{file} or @var{command}---it is not necessary to always
use a string constant. Using a variable is generally a good idea,
because (if you mean to refer to that same file or command)
@command{awk} requires that the string value be written identically
every time.
@cindex coprocesses
@cindex @code{|} (vertical bar) @subentry @code{|&} operator (I/O)
@cindex operators @subentry input/output
@cindex differences in @command{awk} and @command{gawk} @subentry input/output operators
@item print @var{items} |& @var{command}
This redirection prints the items to the input of @var{command}.
The difference between this and the
single-@samp{|} redirection is that the output from @var{command}
can be read with @code{getline}.
Thus, @var{command} is a @dfn{coprocess}, which works together with
but is subsidiary to the @command{awk} program.
This feature is a @command{gawk} extension, and is not available in
POSIX @command{awk}.
@ifnotdocbook
@xref{Getline/Coprocess},
for a brief discussion.
@xref{Two-way I/O},
for a more complete discussion.
@end ifnotdocbook
@ifdocbook
@xref{Getline/Coprocess}
for a brief discussion and
@ref{Two-way I/O}
for a more complete discussion.
@end ifdocbook
@end table
Redirecting output using @samp{>}, @samp{>>}, @samp{|}, or @samp{|&}
asks the system to open a file, pipe, or coprocess only if the particular
@var{file} or @var{command} you specify has not already been written
to by your program or if it has been closed since it was last written to.
@cindex troubleshooting @subentry printing
It is a common error to use @samp{>} redirection for the first @code{print}
to a file, and then to use @samp{>>} for subsequent output:
@example
# clear the file
print "Don't panic" > "guide.txt"
@dots{}
# append
print "Avoid improbability generators" >> "guide.txt"
@end example
@noindent
This is indeed how redirections must be used from the shell. But in
@command{awk}, it isn't necessary. In this kind of case, a program should
use @samp{>} for all the @code{print} statements, because the output file
is only opened once. (It happens that if you mix @samp{>} and @samp{>>}
output is produced in the expected order. However, mixing the operators
for the same file is definitely poor style, and is confusing to readers
of your program.)
@cindex differences in @command{awk} and @command{gawk} @subentry implementation limitations
@cindex implementation issues, @command{gawk} @subentry limits
@cindex @command{awk} @subentry implementation issues @subentry pipes
@cindex @command{gawk} @subentry implementation issues @subentry pipes
@ifnotinfo
As mentioned earlier
(@pxref{Getline Notes}),
many
@end ifnotinfo
@ifnottex
@ifnotdocbook
Many
@end ifnotdocbook
@end ifnottex
older
@command{awk} implementations limit the number of pipelines that an @command{awk}
program may have open to just one! In @command{gawk}, there is no such limit.
@command{gawk} allows a program to
open as many pipelines as the underlying operating system permits.
@cindex sidebar @subentry Piping into @command{sh}
@ifdocbook
@docbook
<sidebar><title>Piping into @command{sh}</title>
@end docbook
@cindex shells @subentry piping commands into
A particularly powerful way to use redirection is to build command lines
and pipe them into the shell, @command{sh}. For example, suppose you
have a list of files brought over from a system where all the @value{FN}s
are stored in uppercase, and you wish to rename them to have names in
all lowercase. The following program is both simple and efficient:
@c @cindex @command{mv} utility
@example
@{ printf("mv %s %s\n", $0, tolower($0)) | "sh" @}
END @{ close("sh") @}
@end example
The @code{tolower()} function returns its argument string with all
uppercase characters converted to lowercase
(@pxref{String Functions}).
The program builds up a list of command lines,
using the @command{mv} utility to rename the files.
It then sends the list to the shell for execution.
@xref{Shell Quoting} for a function that can help in generating
command lines to be fed to the shell.
@docbook
</sidebar>
@end docbook
@end ifdocbook
@ifnotdocbook
@cartouche
@center @b{Piping into @command{sh}}
@cindex shells @subentry piping commands into
A particularly powerful way to use redirection is to build command lines
and pipe them into the shell, @command{sh}. For example, suppose you
have a list of files brought over from a system where all the @value{FN}s
are stored in uppercase, and you wish to rename them to have names in
all lowercase. The following program is both simple and efficient:
@c @cindex @command{mv} utility
@example
@{ printf("mv %s %s\n", $0, tolower($0)) | "sh" @}
END @{ close("sh") @}
@end example
The @code{tolower()} function returns its argument string with all
uppercase characters converted to lowercase
(@pxref{String Functions}).
The program builds up a list of command lines,
using the @command{mv} utility to rename the files.
It then sends the list to the shell for execution.
@xref{Shell Quoting} for a function that can help in generating
command lines to be fed to the shell.
@end cartouche
@end ifnotdocbook
@node Special FD
@section Special Files for Standard Preopened Data Streams
@cindex standard input
@cindex input @subentry standard
@cindex standard output
@cindex output @subentry standard
@cindex error output
@cindex standard error
@cindex file descriptors
@cindex files @subentry descriptors @seeentry{file descriptors}
Running programs conventionally have three input and output streams
already available to them for reading and writing. These are known
as the @dfn{standard input}, @dfn{standard output}, and @dfn{standard
error output}. These open streams (and any other open files or pipes)
are often referred to by the technical term @dfn{file descriptors}.
These streams are, by default, connected to your keyboard and screen, but
they are often redirected with the shell, via the @samp{<}, @samp{<<},
@samp{>}, @samp{>>}, @samp{>&}, and @samp{|} operators. Standard error
is typically used for writing error messages; the reason there are two separate
streams, standard output and standard error, is so that they can be
redirected separately.
@cindex differences in @command{awk} and @command{gawk} @subentry error messages
@cindex error handling
In traditional implementations of @command{awk}, the only way to write an error
message to standard error in an @command{awk} program is as follows:
@example
print "Serious error detected!" | "cat 1>&2"
@end example
@noindent
This works by opening a pipeline to a shell command that can access the
standard error stream that it inherits from the @command{awk} process.
@c 8/2014: Mike Brennan says not to cite this as inefficient. So, fixed.
This is far from elegant, and it also requires a
separate process. So people writing @command{awk} programs often
don't do this. Instead, they send the error messages to the
screen, like this:
@example
print "Serious error detected!" > "/dev/tty"
@end example
@noindent
(@file{/dev/tty} is a special file supplied by the operating system
that is connected to your keyboard and screen. It represents the
``terminal,''@footnote{The ``tty'' in @file{/dev/tty} stands for
``Teletype,'' a serial terminal.} which on modern systems is a keyboard
and screen, not a serial console.)
This generally has the same effect, but not always: although the
standard error stream is usually the screen, it can be redirected; when
that happens, writing to the screen is not correct. In fact, if
@command{awk} is run from a background job, it may not have a
terminal at all.
Then opening @file{/dev/tty} fails.
@command{gawk}, BWK @command{awk}, and @command{mawk} provide
special @value{FN}s for accessing the three standard streams.
If the @value{FN} matches one of these special names when @command{gawk}
(or one of the others) redirects input or output, then it directly uses
the descriptor that the @value{FN} stands for. These special
@value{FN}s work for all operating systems that @command{gawk}
has been ported to, not just those that are POSIX-compliant:
@cindex common extensions @subentry @code{/dev/stdin} special file
@cindex common extensions @subentry @code{/dev/stdout} special file
@cindex common extensions @subentry @code{/dev/stderr} special file
@cindex extensions @subentry common @subentry @code{/dev/stdin} special file
@cindex extensions @subentry common @subentry @code{/dev/stdout} special file
@cindex extensions @subentry common @subentry @code{/dev/stderr} special file
@cindex file names @subentry standard streams in @command{gawk}
@cindex @code{/dev/@dots{}} special files
@cindex files @subentry @code{/dev/@dots{}} special files
@cindex @code{/dev/fd/@var{N}} special files (@command{gawk})
@table @file
@item /dev/stdin
The standard input (file descriptor 0).
@item /dev/stdout
The standard output (file descriptor 1).
@item /dev/stderr
The standard error output (file descriptor 2).
@end table
With these facilities,
the proper way to write an error message then becomes:
@example
print "Serious error detected!" > "/dev/stderr"
@end example
@cindex troubleshooting @subentry quotes with file names
Note the use of quotes around the @value{FN}.
Like with any other redirection, the value must be a string.
It is a common error to omit the quotes, which leads
to confusing results.
@command{gawk} does not treat these @value{FN}s as special when
in POSIX-compatibility mode. However, because BWK @command{awk}
supports them, @command{gawk} does support them even when
invoked with the @option{--traditional} option (@pxref{Options}).
@node Special Files
@section Special @value{FFN}s in @command{gawk}
@cindex @command{gawk} @subentry file names in
Besides access to standard input, standard output, and standard error,
@command{gawk} provides access to any open file descriptor.
Additionally, there are special @value{FN}s reserved for
TCP/IP networking.
@menu
* Other Inherited Files:: Accessing other open files with
@command{gawk}.
* Special Network:: Special files for network communications.
* Special Caveats:: Things to watch out for.
@end menu
@node Other Inherited Files
@subsection Accessing Other Open Files with @command{gawk}
Besides the @code{/dev/stdin}, @code{/dev/stdout}, and @code{/dev/stderr}
special @value{FN}s mentioned earlier, @command{gawk} provides syntax
for accessing any other inherited open file:
@table @file
@item /dev/fd/@var{N}
The file associated with file descriptor @var{N}. Such a file must
be opened by the program initiating the @command{awk} execution (typically
the shell). Unless special pains are taken in the shell from which
@command{gawk} is invoked, only descriptors 0, 1, and 2 are available.
@end table
The @value{FN}s @file{/dev/stdin}, @file{/dev/stdout}, and @file{/dev/stderr}
are essentially aliases for @file{/dev/fd/0}, @file{/dev/fd/1}, and
@file{/dev/fd/2}, respectively. However, those names are more self-explanatory.
Note that using @code{close()} on a @value{FN} of the
form @code{"/dev/fd/@var{N}"}, for file descriptor numbers
above two, does actually close the given file descriptor.
@node Special Network
@subsection Special Files for Network Communications
@cindex networks @subentry support for
@cindex TCP/IP @subentry support for
@command{gawk} programs
can open a two-way
TCP/IP connection, acting as either a client or a server.
This is done using a special @value{FN} of the form:
@example
@file{/@var{net-type}/@var{protocol}/@var{local-port}/@var{remote-host}/@var{remote-port}}
@end example
The @var{net-type} is one of @samp{inet}, @samp{inet4}, or @samp{inet6}.
The @var{protocol} is one of @samp{tcp} or @samp{udp},
and the other fields represent the other essential pieces of information
for making a networking connection.
These @value{FN}s are used with the @samp{|&} operator for communicating
with @w{a coprocess}
(@pxref{Two-way I/O}).
This is an advanced feature, mentioned here only for completeness.
Full discussion is delayed until
@ref{TCP/IP Networking}.
@node Special Caveats
@subsection Special @value{FFN} Caveats
Here are some things to bear in mind when using the
special @value{FN}s that @command{gawk} provides:
@itemize @value{BULLET}
@cindex compatibility mode (@command{gawk}) @subentry file names
@cindex file names @subentry in compatibility mode
@cindex POSIX mode
@item
Recognition of the @value{FN}s for the three standard preopened
files is disabled only in POSIX mode.
@item
Recognition of the other special @value{FN}s is disabled if @command{gawk} is in
compatibility mode (either @option{--traditional} or @option{--posix};
@pxref{Options}).
@item
@command{gawk} @emph{always}
interprets these special @value{FN}s.
For example, using @samp{/dev/fd/4}
for output actually writes on file descriptor 4, and not on a new
file descriptor that is @code{dup()}ed from file descriptor 4. Most of
the time this does not matter; however, it is important to @emph{not}
close any of the files related to file descriptors 0, 1, and 2.
Doing so results in unpredictable behavior.
@end itemize
@node Close Files And Pipes
@section Closing Input and Output Redirections
@cindex files @subentry output @seeentry{output files}
@cindex input files @subentry closing
@cindex output @subentry files, closing
@cindex pipe @subentry closing
@cindex coprocesses @subentry closing
@cindex @code{getline} command @subentry coprocesses, using from
If the same @value{FN} or the same shell command is used with @code{getline}
more than once during the execution of an @command{awk} program
(@pxref{Getline}),
the file is opened (or the command is executed) the first time only.
At that time, the first record of input is read from that file or command.
The next time the same file or command is used with @code{getline},
another record is read from it, and so on.
Similarly, when a file or pipe is opened for output, @command{awk} remembers
the @value{FN} or command associated with it, and subsequent
writes to the same file or command are appended to the previous writes.
The file or pipe stays open until @command{awk} exits.
@cindexawkfunc{close}
This implies that special steps are necessary in order to read the same
file again from the beginning, or to rerun a shell command (rather than
reading more output from the same command). The @code{close()} function
makes these things possible:
@example
close(@var{filename})
@end example
@noindent
or:
@example
close(@var{command})
@end example
The argument @var{filename} or @var{command} can be any expression. Its
value must @emph{exactly} match the string that was used to open the file or
start the command (spaces and other ``irrelevant'' characters
included). For example, if you open a pipe with this:
@example
"sort -r names" | getline foo
@end example
@noindent
then you must close it with this:
@example
close("sort -r names")
@end example
Once this function call is executed, the next @code{getline} from that
file or command, or the next @code{print} or @code{printf} to that
file or command, reopens the file or reruns the command.
Because the expression that you use to close a file or pipeline must
exactly match the expression used to open the file or run the command,
it is good practice to use a variable to store the @value{FN} or command.
The previous example becomes the following:
@example
@group
sortcom = "sort -r names"
sortcom | getline foo
@end group
@group
@dots{}
close(sortcom)
@end group
@end example
@noindent
This helps avoid hard-to-find typographical errors in your @command{awk}
programs. Here are some of the reasons for closing an output file:
@itemize @value{BULLET}
@item
To write a file and read it back later on in the same @command{awk}
program. Close the file after writing it, then
begin reading it with @code{getline}.
@item
To write numerous files, successively, in the same @command{awk}
program. If the files aren't closed, eventually @command{awk} may exceed a
system limit on the number of open files in one process. It is best to
close each one when the program has finished writing it.
@item
To make a command finish. When output is redirected through a pipe,
the command reading the pipe normally continues to try to read input
as long as the pipe is open. Often this means the command cannot
really do its work until the pipe is closed. For example, if
output is redirected to the @command{mail} program, the message is not
actually sent until the pipe is closed.
@item
To run the same program a second time, with the same arguments.
This is not the same thing as giving more input to the first run!
For example, suppose a program pipes output to the @command{mail} program.
If it outputs several lines redirected to this pipe without closing
it, they make a single message of several lines. By contrast, if the
program closes the pipe after each line of output, then each line makes
a separate message.
@end itemize
@cindex differences in @command{awk} and @command{gawk} @subentry @code{close()} function
@cindex portability @subentry @code{close()} function and
@cindex @code{close()} function @subentry portability
If you use more files than the system allows you to have open,
@command{gawk} attempts to multiplex the available open files among
your @value{DF}s. @command{gawk}'s ability to do this depends upon the
facilities of your operating system, so it may not always work. It is
therefore both good practice and good portability advice to always
use @code{close()} on your files when you are done with them.
In fact, if you are using a lot of pipes, it is essential that
you close commands when done. For example, consider something like this:
@example
@{
@dots{}
command = ("grep " $1 " /some/file | my_prog -q " $3)
while ((command | getline) > 0) @{
@var{process output of} command
@}
# need close(command) here
@}
@end example
This example creates a new pipeline based on data in @emph{each} record.
Without the call to @code{close()} indicated in the comment, @command{awk}
creates child processes to run the commands, until it eventually
runs out of file descriptors for more pipelines.
Even though each command has finished (as indicated by the end-of-file
return status from @code{getline}), the child process is not
terminated;@footnote{The technical terminology is rather morbid.
The finished child is called a ``zombie,'' and cleaning up after
it is referred to as ``reaping.''}
@c Good old UNIX: give the marketing guys fits, that's the ticket
more importantly, the file descriptor for the pipe
is not closed and released until @code{close()} is called or
@command{awk} exits.
@code{close()} silently does nothing if given an argument that
does not represent a file, pipe, or coprocess that was opened with
a redirection. In such a case, it returns a negative value,
indicating an error. In addition, @command{gawk} sets @code{ERRNO}
to a string indicating the error.
Note also that @samp{close(FILENAME)} has no ``magic'' effects on the
implicit loop that reads through the files named on the command line.
It is, more likely, a close of a file that was never opened with a
redirection, so @command{awk} silently does nothing, except return
a negative value.
@cindex @code{|} (vertical bar) @subentry @code{|&} operator (I/O) @subentry pipes, closing
When using the @samp{|&} operator to communicate with a coprocess,
it is occasionally useful to be able to close one end of the two-way
pipe without closing the other.
This is done by supplying a second argument to @code{close()}.
As in any other call to @code{close()},
the first argument is the name of the command or special file used
to start the coprocess.
The second argument should be a string, with either of the values
@code{"to"} or @code{"from"}. Case does not matter.
As this is an advanced feature, discussion is
delayed until
@ref{Two-way I/O},
which describes it in more detail and gives an example.
@cindex sidebar @subentry Using @code{close()}'s Return Value
@ifdocbook
@docbook
<sidebar><title>Using @code{close()}'s Return Value</title>
@end docbook
@cindex dark corner @subentry @code{close()} function
@cindex @code{close()} function @subentry return value
@cindex return value, @code{close()} function
@cindex differences in @command{awk} and @command{gawk} @subentry @code{close()} function
@cindex Unix @command{awk} @subentry @code{close()} function and
In many older versions of Unix @command{awk}, the @code{close()} function
is actually a statement.
@value{DARKCORNER}
It is a syntax error to try and use the return
value from @code{close()}:
@example
command = "@dots{}"
command | getline info
retval = close(command) # syntax error in many Unix awks
@end example
@cindex @command{gawk} @subentry @code{ERRNO} variable in
@cindex @code{ERRNO} variable @subentry with @command{close()} function
@command{gawk} treats @code{close()} as a function.
The return value is @minus{}1 if the argument names something
that was never opened with a redirection, or if there is
a system problem closing the file or process.
In these cases, @command{gawk} sets the predefined variable
@code{ERRNO} to a string describing the problem.
In @command{gawk}, starting with @value{PVERSION} 4.2, when closing a pipe or
coprocess (input or output), the return value is the exit status of the
command, as described in @ref{table-close-pipe-return-values}.@footnote{Prior
to @value{PVERSION} 4.2, the return value from closing a pipe or co-process
was the full 16-bit exit value as defined by the @code{wait()} system
call.} Otherwise, it is the return value from the system's @code{close()}
or @code{fclose()} C functions when closing input or output files,
respectively. This value is zero if the close succeeds, or @minus{}1
if it fails.
@float Table,table-close-pipe-return-values
@caption{Return values from @code{close()} of a pipe}
@multitable @columnfractions .50 .50
@headitem Situation @tab Return value from @code{close()}
@item Normal exit of command @tab Command's exit status
@item Death by signal of command @tab 256 + number of murderous signal
@item Death by signal of command with core dump @tab 512 + number of murderous signal
@item Some kind of error @tab @minus{}1
@end multitable
@end float
@cindex POSIX mode
The POSIX standard is very vague; it says that @code{close()}
returns zero on success and a nonzero value otherwise. In general,
different implementations vary in what they report when closing
pipes; thus, the return value cannot be used portably.
@value{DARKCORNER}
In POSIX mode (@pxref{Options}), @command{gawk} just returns zero
when closing a pipe.
@docbook
</sidebar>
@end docbook
@end ifdocbook
@ifnotdocbook
@cartouche
@center @b{Using @code{close()}'s Return Value}
@cindex dark corner @subentry @code{close()} function
@cindex @code{close()} function @subentry return value
@cindex return value, @code{close()} function
@cindex differences in @command{awk} and @command{gawk} @subentry @code{close()} function
@cindex Unix @command{awk} @subentry @code{close()} function and
In many older versions of Unix @command{awk}, the @code{close()} function
is actually a statement.
@value{DARKCORNER}
It is a syntax error to try and use the return
value from @code{close()}:
@example
command = "@dots{}"
command | getline info
retval = close(command) # syntax error in many Unix awks
@end example
@cindex @command{gawk} @subentry @code{ERRNO} variable in
@cindex @code{ERRNO} variable @subentry with @command{close()} function
@command{gawk} treats @code{close()} as a function.
The return value is @minus{}1 if the argument names something
that was never opened with a redirection, or if there is
a system problem closing the file or process.
In these cases, @command{gawk} sets the predefined variable
@code{ERRNO} to a string describing the problem.
In @command{gawk}, starting with @value{PVERSION} 4.2, when closing a pipe or
coprocess (input or output), the return value is the exit status of the
command, as described in @ref{table-close-pipe-return-values}.@footnote{Prior
to @value{PVERSION} 4.2, the return value from closing a pipe or co-process
was the full 16-bit exit value as defined by the @code{wait()} system
call.} Otherwise, it is the return value from the system's @code{close()}
or @code{fclose()} C functions when closing input or output files,
respectively. This value is zero if the close succeeds, or @minus{}1
if it fails.
@float Table,table-close-pipe-return-values
@caption{Return values from @code{close()} of a pipe}
@multitable @columnfractions .50 .50
@headitem Situation @tab Return value from @code{close()}
@item Normal exit of command @tab Command's exit status
@item Death by signal of command @tab 256 + number of murderous signal
@item Death by signal of command with core dump @tab 512 + number of murderous signal
@item Some kind of error @tab @minus{}1
@end multitable
@end float
@cindex POSIX mode
The POSIX standard is very vague; it says that @code{close()}
returns zero on success and a nonzero value otherwise. In general,
different implementations vary in what they report when closing
pipes; thus, the return value cannot be used portably.
@value{DARKCORNER}
In POSIX mode (@pxref{Options}), @command{gawk} just returns zero
when closing a pipe.
@end cartouche
@end ifnotdocbook
@node Nonfatal
@section Enabling Nonfatal Output
This @value{SECTION} describes a @command{gawk}-specific feature.
In standard @command{awk}, output with @code{print} or @code{printf}
to a nonexistent file, or some other I/O error (such as filling up the
disk) is a fatal error.
@example
$ @kbd{gawk 'BEGIN @{ print "hi" > "/no/such/file" @}'}
@error{} gawk: cmd. line:1: fatal: can't redirect to `/no/such/file' (No
@error{} such file or directory)
@end example
@command{gawk} makes it possible to detect that an error has
occurred, allowing you to possibly recover from the error, or
at least print an error message of your choosing before exiting.
You can do this in one of two ways:
@itemize @bullet
@item
For all output files, by assigning any value to @code{PROCINFO["NONFATAL"]}.
@item
On a per-file basis, by assigning any value to
@code{PROCINFO[@var{filename}, "NONFATAL"]}.
Here, @var{filename} is the name of the file to which
you wish output to be nonfatal.
@end itemize
Once you have enabled nonfatal output, you must check @code{ERRNO}
after every relevant @code{print} or @code{printf} statement to
see if something went wrong. It is also a good idea to initialize
@code{ERRNO} to zero before attempting the output. For example:
@example
$ @kbd{gawk '}
> @kbd{BEGIN @{}
> @kbd{ PROCINFO["NONFATAL"] = 1}
> @kbd{ ERRNO = 0}
> @kbd{ print "hi" > "/no/such/file"}
> @kbd{ if (ERRNO) @{}
> @kbd{ print("Output failed:", ERRNO) > "/dev/stderr"}
> @kbd{ exit 1}
> @kbd{ @}}
> @kbd{@}'}
@error{} Output failed: No such file or directory
@end example
Here, @command{gawk} did not produce a fatal error; instead
it let the @command{awk} program code detect the problem and handle it.
This mechanism works also for standard output and standard error.
For standard output, you may use @code{PROCINFO["-", "NONFATAL"]}
or @code{PROCINFO["/dev/stdout", "NONFATAL"]}. For standard error, use
@code{PROCINFO["/dev/stderr", "NONFATAL"]}.
@cindex @env{GAWK_SOCK_RETRIES} environment variable
@cindex environment variables @subentry @env{GAWK_SOCK_RETRIES}
When attempting to open a TCP/IP socket (@pxref{TCP/IP Networking}),
@command{gawk} tries multiple times. The @env{GAWK_SOCK_RETRIES}
environment variable (@pxref{Other Environment Variables}) allows you to
override @command{gawk}'s builtin default number of attempts. However,
once nonfatal I/O is enabled for a given socket, @command{gawk} only
retries once, relying on @command{awk}-level code to notice that there
was a problem.
@node Output Summary
@section Summary
@itemize @value{BULLET}
@item
The @code{print} statement prints comma-separated expressions. Each
expression is separated by the value of @code{OFS} and terminated by
the value of @code{ORS}. @code{OFMT} provides the conversion format
for numeric values for the @code{print} statement.
@item
The @code{printf} statement provides finer-grained control over output,
with format-control letters for different data types and various flags
that modify the behavior of the format-control letters.
@item
Output from both @code{print} and @code{printf} may be redirected to
files, pipes, and coprocesses.
@item
@command{gawk} provides special @value{FN}s for access to standard input,
output, and error, and for network communications.
@item
Use @code{close()} to close open file, pipe, and coprocess redirections.
For coprocesses, it is possible to close only one direction of the
communications.
@item
Normally errors with @code{print} or @code{printf} are fatal.
@command{gawk} lets you make output errors be nonfatal either for
all files or on a per-file basis. You must then check for errors
after every relevant output statement.
@end itemize
@c EXCLUDE START
@node Output Exercises
@section Exercises
@enumerate
@item
Rewrite the program:
@example
awk 'BEGIN @{ print "Month Crates"
print "----- ------" @}
@{ print $1, " ", $2 @}' inventory-shipped
@end example
@noindent
from @ref{Output Separators}, by using a new value of @code{OFS}.
@item
Use the @code{printf} statement to line up the headings and table data
for the @file{inventory-shipped} example that was covered in @ref{Print}.
@item
What happens if you forget the double quotes when redirecting
output, as follows:
@example
BEGIN @{ print "Serious error detected!" > /dev/stderr @}
@end example
@end enumerate
@c EXCLUDE END
@node Expressions
@chapter Expressions
@cindex expressions
Expressions are the basic building blocks of @command{awk} patterns
and actions. An expression evaluates to a value that you can print, test,
or pass to a function. Additionally, an expression
can assign a new value to a variable or a field by using an assignment operator.
An expression can serve as a pattern or action statement on its own.
Most other kinds of
statements contain one or more expressions that specify the data on which to
operate. As in other languages, expressions in @command{awk} can include
variables, array references, constants, and function calls, as well as
combinations of these with various operators.
@menu
* Values:: Constants, Variables, and Regular Expressions.
* All Operators:: @command{gawk}'s operators.
* Truth Values and Conditions:: Testing for true and false.
* Function Calls:: A function call is an expression.
* Precedence:: How various operators nest.
* Locales:: How the locale affects things.
* Expressions Summary:: Expressions summary.
@end menu
@node Values
@section Constants, Variables, and Conversions
Expressions are built up from values and the operations performed
upon them. This @value{SECTION} describes the elementary objects
that provide the values used in expressions.
@menu
* Constants:: String, numeric and regexp constants.
* Using Constant Regexps:: When and how to use a regexp constant.
* Variables:: Variables give names to values for later use.
* Conversion:: The conversion of strings to numbers and vice
versa.
@end menu
@node Constants
@subsection Constant Expressions
@cindex constants @subentry types of
The simplest type of expression is the @dfn{constant}, which always has
the same value. There are three types of constants: numeric,
string, and regular expression.
Each is used in the appropriate context when you need a data
value that isn't going to change. Numeric constants can
have different forms, but are internally stored in an identical manner.
@menu
* Scalar Constants:: Numeric and string constants.
* Nondecimal-numbers:: What are octal and hex numbers.
* Regexp Constants:: Regular Expression constants.
@end menu
@node Scalar Constants
@subsubsection Numeric and String Constants
@cindex constants @subentry numeric
@cindex numeric @subentry constants
A @dfn{numeric constant} stands for a number. This number can be an
integer, a decimal fraction, or a number in scientific (exponential)
notation.@footnote{The internal representation of all numbers,
including integers, uses double-precision floating-point numbers.
On most modern systems, these are in IEEE 754 standard format.
@xref{Arbitrary Precision Arithmetic}, for much more information.}
Here are some examples of numeric constants that all
have the same value:
@example
105
1.05e+2
1050e-1
@end example
@cindex string @subentry constants
@cindex constants @subentry string
A @dfn{string constant} consists of a sequence of characters enclosed in
double quotation marks. For example:
@example
"parrot"
@end example
@noindent
@cindex differences in @command{awk} and @command{gawk} @subentry strings
@cindex strings @subentry length limitations
@cindex ASCII
represents the string whose contents are @samp{parrot}. Strings in
@command{gawk} can be of any length, and they can contain any of the possible
eight-bit ASCII characters, including ASCII @sc{nul} (character code zero).
Other @command{awk}
implementations may have difficulty with some character codes.
Some languages allow you to continue long strings across
multiple lines by ending the line with a backslash. For example in C:
@example
#include <stdio.h>
int main()
@{
printf("hello, \
world\n");
return 0;
@}
@end example
@noindent
In such a case, the C compiler removes both the backslash and the newline,
producing a string as if it had been typed @samp{"hello, world\n"}.
This is useful when a single string needs to contain a large amount of text.
The POSIX standard says explicitly that newlines are not allowed inside string
constants. And indeed, all @command{awk} implementations report an error
if you try to do so. For example:
@example
$ @kbd{gawk 'BEGIN @{ print "hello, }
> @kbd{world" @}'}
@print{} gawk: cmd. line:1: BEGIN @{ print "hello,
@print{} gawk: cmd. line:1: ^ unterminated string
@print{} gawk: cmd. line:1: BEGIN @{ print "hello,
@print{} gawk: cmd. line:1: ^ syntax error
@end example
@cindex dark corner @subentry string continuation
@cindex strings @subentry continuation across lines
@cindex differences in @command{awk} and @command{gawk} @subentry strings
Although POSIX doesn't define what happens if you use an escaped
newline, as in the previous C example, all known versions of
@command{awk} allow you to do so. Unfortunately, what each one
does with such a string varies. @value{DARKCORNER} @command{gawk},
@command{mawk}, and the OpenSolaris POSIX @command{awk}
(@pxref{Other Versions}) elide the backslash and newline, as in C:
@example
$ @kbd{gawk 'BEGIN @{ print "hello, \}
> @kbd{world" @}'}
@print{} hello, world
@end example
@cindex POSIX mode
In POSIX mode (@pxref{Options}), @command{gawk} does not
allow escaped newlines. Otherwise, it behaves as just described.
Brian Kernighan's @command{awk} and BusyBox @command{awk}
remove the backslash but leave the newline
intact, as part of the string:
@example
$ @kbd{nawk 'BEGIN @{ print "hello, \}
> @kbd{world" @}'}
@print{} hello,
@print{} world
@end example
@node Nondecimal-numbers
@subsubsection Octal and Hexadecimal Numbers
@cindex octal numbers
@cindex hexadecimal numbers
@cindex numbers @subentry octal
@cindex numbers @subentry hexadecimal
In @command{awk}, all numbers are in decimal (i.e., base 10). Many other
programming languages allow you to specify numbers in other bases, often
octal (base 8) and hexadecimal (base 16).
In octal, the numbers go 0, 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, and so on.
Just as @samp{11} in decimal is 1 times 10 plus 1, so
@samp{11} in octal is 1 times 8 plus 1. This equals 9 in decimal.
In hexadecimal, there are 16 digits. Because the everyday decimal
number system only has ten digits (@samp{0}--@samp{9}), the letters
@samp{a} through @samp{f} represent the rest.
(Case in the letters is usually irrelevant; hexadecimal @samp{a} and @samp{A}
have the same value.)
Thus, @samp{11} in
hexadecimal is 1 times 16 plus 1, which equals 17 in decimal.
Just by looking at plain @samp{11}, you can't tell what base it's in.
So, in C, C++, and other languages derived from C,
@c such as PERL, but we won't mention that....
there is a special notation to signify the base.
Octal numbers start with a leading @samp{0},
and hexadecimal numbers start with a leading @samp{0x} or @samp{0X}:
@table @code
@item 11
Decimal value 11
@item 011
Octal 11, decimal value 9
@item 0x11
Hexadecimal 11, decimal value 17
@end table
This example shows the difference:
@example
$ @kbd{gawk 'BEGIN @{ printf "%d, %d, %d\n", 011, 11, 0x11 @}'}
@print{} 9, 11, 17
@end example
Being able to use octal and hexadecimal constants in your programs is most
useful when working with data that cannot be represented conveniently as
characters or as regular numbers, such as binary data of various sorts.
@cindex @command{gawk} @subentry octal numbers and
@cindex @command{gawk} @subentry hexadecimal numbers and
@command{gawk} allows the use of octal and hexadecimal
constants in your program text. However, such numbers in the input data
are not treated differently; doing so by default would break old
programs.
(If you really need to do this, use the @option{--non-decimal-data}
command-line option;
@pxref{Nondecimal Data}.)
If you have octal or hexadecimal data,
you can use the @code{strtonum()} function
(@pxref{String Functions})
to convert the data into a number.
Most of the time, you will want to use octal or hexadecimal constants
when working with the built-in bit-manipulation functions;
see @ref{Bitwise Functions}
for more information.
Unlike in some early C implementations, @samp{8} and @samp{9} are not
valid in octal constants. For example, @command{gawk} treats @samp{018}
as decimal 18:
@example
$ @kbd{gawk 'BEGIN @{ print "021 is", 021 ; print 018 @}'}
@print{} 021 is 17
@print{} 18
@end example
@cindex compatibility mode (@command{gawk}) @subentry octal numbers
@cindex compatibility mode (@command{gawk}) @subentry hexadecimal numbers
Octal and hexadecimal source code constants are a @command{gawk} extension.
If @command{gawk} is in compatibility mode
(@pxref{Options}),
they are not available.
@cindex sidebar @subentry A Constant's Base Does Not Affect Its Value
@ifdocbook
@docbook
<sidebar><title>A Constant's Base Does Not Affect Its Value</title>
@end docbook
Once a numeric constant has
been converted internally into a number,
@command{gawk} no longer remembers
what the original form of the constant was; the internal value is
always used. This has particular consequences for conversion of
numbers to strings:
@example
$ @kbd{gawk 'BEGIN @{ printf "0x11 is <%s>\n", 0x11 @}'}
@print{} 0x11 is <17>
@end example
@docbook
</sidebar>
@end docbook
@end ifdocbook
@ifnotdocbook
@cartouche
@center @b{A Constant's Base Does Not Affect Its Value}
Once a numeric constant has
been converted internally into a number,
@command{gawk} no longer remembers
what the original form of the constant was; the internal value is
always used. This has particular consequences for conversion of
numbers to strings:
@example
$ @kbd{gawk 'BEGIN @{ printf "0x11 is <%s>\n", 0x11 @}'}
@print{} 0x11 is <17>
@end example
@end cartouche
@end ifnotdocbook
@node Regexp Constants
@subsubsection Regular Expression Constants
@cindex regexp constants
@cindex @code{~} (tilde), @code{~} operator
@cindex tilde (@code{~}), @code{~} operator
@cindex @code{!} (exclamation point) @subentry @code{!~} operator
@cindex exclamation point (@code{!}) @subentry @code{!~} operator
A @dfn{regexp constant} is a regular expression description enclosed in
slashes, such as @code{@w{/^beginning and end$/}}. Most regexps used in
@command{awk} programs are constant, but the @samp{~} and @samp{!~}
matching operators can also match computed or dynamic regexps
(which are typically just ordinary strings or variables that contain a regexp,
but could be more complex expressions).
@node Using Constant Regexps
@subsection Using Regular Expression Constants
Regular expression constants consist of text describing
a regular expression enclosed in slashes (such as @code{/the +answer/}).
This @value{SECTION} describes how such constants work in
POSIX @command{awk} and @command{gawk}, and then goes on to describe
@dfn{strongly typed regexp constants}, which are a @command{gawk} extension.
@menu
* Standard Regexp Constants:: Regexp constants in standard @command{awk}.
* Strong Regexp Constants:: Strongly typed regexp constants.
@end menu
@node Standard Regexp Constants
@subsubsection Standard Regular Expression Constants
@cindex dark corner @subentry regexp constants
When used on the righthand side of the @samp{~} or @samp{!~}
operators, a regexp constant merely stands for the regexp that is to be
matched.
However, regexp constants (such as @code{/foo/}) may be used like simple expressions.
When a
regexp constant appears by itself, it has the same meaning as if it appeared
in a pattern (i.e., @samp{($0 ~ /foo/)}).
@value{DARKCORNER}
@xref{Expression Patterns}.
This means that the following two code segments:
@example
if ($0 ~ /barfly/ || $0 ~ /camelot/)
print "found"
@end example
@noindent
and:
@example
if (/barfly/ || /camelot/)
print "found"
@end example
@noindent
are exactly equivalent.
One rather bizarre consequence of this rule is that the following
Boolean expression is valid, but does not do what its author probably
intended:
@example
# Note that /foo/ is on the left of the ~
if (/foo/ ~ $1) print "found foo"
@end example
@c @cindex automatic warnings
@c @cindex warnings, automatic
@cindex @command{gawk} @subentry regexp constants and
@cindex regexp constants @subentry in @command{gawk}
@noindent
This code is ``obviously'' testing @code{$1} for a match against the regexp
@code{/foo/}. But in fact, the expression @samp{/foo/ ~ $1} really means
@samp{($0 ~ /foo/) ~ $1}. In other words, first match the input record
against the regexp @code{/foo/}. The result is either zero or one,
depending upon the success or failure of the match. That result
is then matched against the first field in the record.
Because it is unlikely that you would ever really want to make this kind of
test, @command{gawk} issues a warning when it sees this construct in
a program.
Another consequence of this rule is that the assignment statement:
@example
matches = /foo/
@end example
@noindent
assigns either zero or one to the variable @code{matches}, depending
upon the contents of the current input record.
@cindex differences in @command{awk} and @command{gawk} @subentry regexp constants
@cindex dark corner @subentry regexp constants @subentry as arguments to user-defined functions
@cindexgawkfunc{gensub}
@cindexawkfunc{sub}
@cindexawkfunc{gsub}
Constant regular expressions are also used as the first argument for
the @code{gensub()}, @code{sub()}, and @code{gsub()} functions, as the
second argument of the @code{match()} function,
and as the third argument of the @code{split()} and @code{patsplit()} functions
(@pxref{String Functions}).
Modern implementations of @command{awk}, including @command{gawk}, allow
the third argument of @code{split()} to be a regexp constant, but some
older implementations do not.
@value{DARKCORNER}
Because some built-in functions accept regexp constants as arguments,
confusion can arise when attempting to use regexp constants as arguments
to user-defined functions (@pxref{User-defined}). For example:
@example
@group
function mysub(pat, repl, str, global)
@{
if (global)
gsub(pat, repl, str)
else
sub(pat, repl, str)
return str
@}
@end group
@group
@{
@dots{}
text = "hi! hi yourself!"
mysub(/hi/, "howdy", text, 1)
@dots{}
@}
@end group
@end example
@c @cindex automatic warnings
@c @cindex warnings, automatic
In this example, the programmer wants to pass a regexp constant to the
user-defined function @code{mysub()}, which in turn passes it on to
either @code{sub()} or @code{gsub()}. However, what really happens is that
the @code{pat} parameter is assigned a value of either one or zero, depending upon whether
or not @code{$0} matches @code{/hi/}.
@command{gawk} issues a warning when it sees a regexp constant used as
a parameter to a user-defined function, because passing a truth value in
this way is probably not what was intended.
@node Strong Regexp Constants
@subsubsection Strongly Typed Regexp Constants
This @value{SECTION} describes a @command{gawk}-specific feature.
As we saw in the previous @value{SECTION},
regexp constants (@code{/@dots{}/}) hold a strange position in the
@command{awk} language. In most contexts, they act like an expression:
@samp{$0 ~ /@dots{}/}. In other contexts, they denote only a regexp to
be matched. In no case are they really a ``first class citizen'' of the
language. That is, you cannot define a scalar variable whose type is
``regexp'' in the same sense that you can define a variable to be a
number or a string:
@example
num = 42 @ii{Numeric variable}
str = "hi" @ii{String variable}
re = /foo/ @ii{Wrong!} re @ii{is the result of} $0 ~ /foo/
@end example
For a number of more advanced use cases,
it would be nice to have regexp constants that
are @dfn{strongly typed}; in other words, that denote a regexp useful
for matching, and not an expression.
@cindex values @subentry regexp
@command{gawk} provides this feature. A strongly typed regexp constant
looks almost like a regular regexp constant, except that it is preceded
by an @samp{@@} sign:
@example
re = @@/foo/ @ii{Regexp variable}
@end example
Strongly typed regexp constants @emph{cannot} be used everywhere that a
regular regexp constant can, because this would make the language even more
confusing. Instead, you may use them only in certain contexts:
@itemize @bullet
@item
On the righthand side of the @samp{~} and @samp{!~} operators: @samp{some_var ~ @@/foo/}
(@pxref{Regexp Usage}).
@item
In the @code{case} part of a @code{switch} statement
(@pxref{Switch Statement}).
@item
As an argument to one of the built-in functions that accept regexp constants:
@code{gensub()},
@code{gsub()},
@code{match()},
@code{patsplit()},
@code{split()},
and
@code{sub()}
(@pxref{String Functions}).
@item
As a parameter in a call to a user-defined function
(@pxref{User-defined}).
@item
On the righthand side of an assignment to a variable: @samp{some_var = @@/foo/}.
In this case, the type of @code{some_var} is regexp. Additionally, @code{some_var}
can be used with @samp{~} and @samp{!~}, passed to one of the built-in functions
listed above, or passed as a parameter to a user-defined function.
@end itemize
You may use the @code{typeof()} built-in function
(@pxref{Type Functions})
to determine if a variable or function parameter is
a regexp variable.
The true power of this feature comes from the ability to create variables that
have regexp type. Such variables can be passed on to user-defined functions,
without the confusing aspects of computed regular expressions created from
strings or string constants. They may also be passed through indirect function
calls (@pxref{Indirect Calls})
and on to the built-in functions that accept regexp constants.
When used in numeric conversions, strongly typed regexp variables convert
to zero. When used in string conversions, they convert to the string
value of the original regexp text.
@node Variables
@subsection Variables
@cindex variables @subentry user-defined
@cindex user-defined @subentry variables
@dfn{Variables} are ways of storing values at one point in your program for
use later in another part of your program. They can be manipulated
entirely within the program text, and they can also be assigned values
on the @command{awk} command line.
@menu
* Using Variables:: Using variables in your programs.
* Assignment Options:: Setting variables on the command line and a
summary of command-line syntax. This is an
advanced method of input.
@end menu
@node Using Variables
@subsubsection Using Variables in a Program
Variables let you give names to values and refer to them later. Variables
have already been used in many of the examples. The name of a variable
must be a sequence of letters, digits, or underscores, and it may not begin
with a digit.
Here, a @dfn{letter} is any one of the 52 upper- and lowercase
English letters. Other characters that may be defined as letters
in non-English locales are not valid in variable names.
Case is significant in variable names; @code{a} and @code{A}
are distinct variables.
A variable name is a valid expression by itself; it represents the
variable's current value. Variables are given new values with
@dfn{assignment operators}, @dfn{increment operators}, and
@dfn{decrement operators}
(@pxref{Assignment Ops}).
In addition, the @code{sub()} and @code{gsub()} functions can
change a variable's value, and the @code{match()}, @code{split()},
and @code{patsplit()} functions can change the contents of their
array parameters (@pxref{String Functions}).
@cindex variables @subentry built-in
@cindex variables @subentry initializing
A few variables have special built-in meanings, such as @code{FS} (the
field separator) and @code{NF} (the number of fields in the current input
record). @xref{Built-in Variables} for a list of the predefined variables.
These predefined variables can be used and assigned just like all other
variables, but their values are also used or changed automatically by
@command{awk}. All predefined variables' names are entirely uppercase.
Variables in @command{awk} can be assigned either numeric or string values.
The kind of value a variable holds can change over the life of a program.
By default, variables are initialized to the empty string, which
is zero if converted to a number. There is no need to explicitly
initialize a variable in @command{awk},
which is what you would do in C and in most other traditional languages.
@node Assignment Options
@subsubsection Assigning Variables on the Command Line
@cindex variables @subentry assigning on command line
@cindex command line @subentry variables, assigning on
Any @command{awk} variable can be set by including a @dfn{variable assignment}
among the arguments on the command line when @command{awk} is invoked
(@pxref{Other Arguments}).
Such an assignment has the following form:
@example
@var{variable}=@var{text}
@end example
@cindex @option{-v} option
@noindent
With it, a variable is set either at the beginning of the
@command{awk} run or in between input files.
When the assignment is preceded with the @option{-v} option,
as in the following:
@example
-v @var{variable}=@var{text}
@end example
@noindent
the variable is set at the very beginning, even before the
@code{BEGIN} rules execute. The @option{-v} option and its assignment
must precede all the @value{FN} arguments, as well as the program text.
(@xref{Options} for more information about
the @option{-v} option.)
Otherwise, the variable assignment is performed at a time determined by
its position among the input file arguments---after the processing of the
preceding input file argument. For example:
@example
awk '@{ print $n @}' n=4 inventory-shipped n=2 mail-list
@end example
@noindent
prints the value of field number @code{n} for all input records. Before
the first file is read, the command line sets the variable @code{n}
equal to four. This causes the fourth field to be printed in lines from
@file{inventory-shipped}. After the first file has finished,
but before the second file is started, @code{n} is set to two, so that the
second field is printed in lines from @file{mail-list}:
@example
$ @kbd{awk '@{ print $n @}' n=4 inventory-shipped n=2 mail-list}
@print{} 15
@print{} 24
@dots{}
@print{} 555-5553
@print{} 555-3412
@dots{}
@end example
@cindex dark corner @subentry command-line arguments
Command-line arguments are made available for explicit examination by
the @command{awk} program in the @code{ARGV} array
(@pxref{ARGC and ARGV}).
@command{awk} processes the values of command-line assignments for escape
sequences
(@pxref{Escape Sequences}).
@value{DARKCORNER}
Normally, variables assigned on the command line (with or without the
@option{-v} option) are treated as strings. When such variables are
used as numbers, @command{awk}'s normal automatic conversion of strings
to numbers takes place, and everything ``just works.''
However, @command{gawk} supports variables whose types are ``regexp''.
You can assign variables of this type using the following syntax:
@example
gawk -v 're1=@@/foo|bar/' '@dots{}' /path/to/file1 're2=@@/baz|quux/' /path/to/file2
@end example
@noindent
Strongly typed regexps are an advanced feature (@pxref{Strong Regexp Constants}).
We mention them here only for completeness.
@node Conversion
@subsection Conversion of Strings and Numbers
Number-to-string and string-to-number conversion are generally
straightforward. There can be subtleties to be aware of;
this @value{SECTION} discusses this important facet of @command{awk}.
@menu
* Strings And Numbers:: How @command{awk} Converts Between Strings And
Numbers.
* Locale influences conversions:: How the locale may affect conversions.
@end menu
@node Strings And Numbers
@subsubsection How @command{awk} Converts Between Strings and Numbers
@cindex converting @subentry string to numbers
@cindex strings @subentry converting
@cindex numbers @subentry converting
@cindex converting @subentry numbers to strings
Strings are converted to numbers and numbers are converted to strings, if the context
of the @command{awk} program demands it. For example, if the value of
either @code{foo} or @code{bar} in the expression @samp{foo + bar}
happens to be a string, it is converted to a number before the addition
is performed. If numeric values appear in string concatenation, they
are converted to strings. Consider the following:
@example
@group
two = 2; three = 3
print (two three) + 4
@end group
@end example
@noindent
This prints the (numeric) value 27. The numeric values of
the variables @code{two} and @code{three} are converted to strings and
concatenated together. The resulting string is converted back to the
number 23, to which 4 is then added.
@cindex null strings @subentry converting numbers to strings
@cindex type @subentry conversion
If, for some reason, you need to force a number to be converted to a
string, concatenate that number with the empty string, @code{""}.
To force a string to be converted to a number, add zero to that string.
A string is converted to a number by interpreting any numeric prefix
of the string as numerals:
@code{"2.5"} converts to 2.5, @code{"1e3"} converts to 1,000, and @code{"25fix"}
has a numeric value of 25.
Strings that can't be interpreted as valid numbers convert to zero.
@cindex @code{CONVFMT} variable
The exact manner in which numbers are converted into strings is controlled
by the @command{awk} predefined variable @code{CONVFMT} (@pxref{Built-in Variables}).
Numbers are converted using the @code{sprintf()} function
with @code{CONVFMT} as the format
specifier
(@pxref{String Functions}).
@code{CONVFMT}'s default value is @code{"%.6g"}, which creates a value with
at most six significant digits. For some applications, you might want to
change it to specify more precision.
On most modern machines,
17 digits is usually enough to capture a floating-point number's
value exactly.@footnote{Pathological cases can require up to
752 digits (!), but we doubt that you need to worry about this.}
@cindex dark corner @subentry @code{CONVFMT} variable
Strange results can occur if you set @code{CONVFMT} to a string that doesn't
tell @code{sprintf()} how to format floating-point numbers in a useful way.
For example, if you forget the @samp{%} in the format, @command{awk} converts
all numbers to the same constant string.
As a special case, if a number is an integer, then the result of converting
it to a string is @emph{always} an integer, no matter what the value of
@code{CONVFMT} may be. Given the following code fragment:
@example
CONVFMT = "%2.2f"
a = 12
b = a ""
@end example
@noindent
@code{b} has the value @code{"12"}, not @code{"12.00"}.
@value{DARKCORNER}
@cindex sidebar @subentry Pre-POSIX @command{awk} Used @code{OFMT} for String Conversion
@ifdocbook
@docbook
<sidebar><title>Pre-POSIX @command{awk} Used @code{OFMT} for String Conversion</title>
@end docbook
@cindex POSIX @command{awk} @subentry @code{OFMT} variable and
@cindex @code{OFMT} variable
@cindex portability @subentry new @command{awk} vs.@: old @command{awk}
@cindex @command{awk} @subentry new vs.@: old @subentry @code{OFMT} variable
Prior to the POSIX standard, @command{awk} used the value
of @code{OFMT} for converting numbers to strings. @code{OFMT}
specifies the output format to use when printing numbers with @code{print}.
@code{CONVFMT} was introduced in order to separate the semantics of
conversion from the semantics of printing. Both @code{CONVFMT} and
@code{OFMT} have the same default value: @code{"%.6g"}. In the vast majority
of cases, old @command{awk} programs do not change their behavior.
@xref{Print} for more information on the @code{print} statement.
@docbook
</sidebar>
@end docbook
@end ifdocbook
@ifnotdocbook
@cartouche
@center @b{Pre-POSIX @command{awk} Used @code{OFMT} for String Conversion}
@cindex POSIX @command{awk} @subentry @code{OFMT} variable and
@cindex @code{OFMT} variable
@cindex portability @subentry new @command{awk} vs.@: old @command{awk}
@cindex @command{awk} @subentry new vs.@: old @subentry @code{OFMT} variable
Prior to the POSIX standard, @command{awk} used the value
of @code{OFMT} for converting numbers to strings. @code{OFMT}
specifies the output format to use when printing numbers with @code{print}.
@code{CONVFMT} was introduced in order to separate the semantics of
conversion from the semantics of printing. Both @code{CONVFMT} and
@code{OFMT} have the same default value: @code{"%.6g"}. In the vast majority
of cases, old @command{awk} programs do not change their behavior.
@xref{Print} for more information on the @code{print} statement.
@end cartouche
@end ifnotdocbook
@node Locale influences conversions
@subsubsection Locales Can Influence Conversion
Where you are can matter when it comes to converting between numbers and
strings. The local character set and language---the @dfn{locale}---can
affect numeric formats. In particular, for @command{awk} programs,
it affects the decimal point character and the thousands-separator
character. The @code{"C"} locale, and most English-language locales,
use the period character (@samp{.}) as the decimal point and don't
have a thousands separator. However, many (if not most) European and
non-English locales use the comma (@samp{,}) as the decimal point
character. European locales often use either a space or a period as
the thousands separator, if they have one.
@cindex dark corner @subentry locale's decimal point character
The POSIX standard says that @command{awk} always uses the period as the decimal
point when reading the @command{awk} program source code, and for
command-line variable assignments (@pxref{Other Arguments}). However,
when interpreting input data, for @code{print} and @code{printf} output,
and for number-to-string conversion, the local decimal point character
is used. @value{DARKCORNER} In all cases, numbers in source code and
in input data cannot have a thousands separator. Here are some examples
indicating the difference in behavior, on a GNU/Linux system:
@example
$ @kbd{export POSIXLY_CORRECT=1} @ii{Force POSIX behavior}
$ @kbd{gawk 'BEGIN @{ printf "%g\n", 3.1415927 @}'}
@print{} 3.14159
$ @kbd{LC_ALL=en_DK.utf-8 gawk 'BEGIN @{ printf "%g\n", 3.1415927 @}'}
@print{} 3,14159
$ @kbd{echo 4,321 | gawk '@{ print $1 + 1 @}'}
@print{} 5
$ @kbd{echo 4,321 | LC_ALL=en_DK.utf-8 gawk '@{ print $1 + 1 @}'}
@print{} 5,321
@end example
@noindent
The @code{en_DK.utf-8} locale is for English in Denmark, where the comma acts as
the decimal point separator. In the normal @code{"C"} locale, @command{gawk}
treats @samp{4,321} as 4, while in the Danish locale, it's treated
as the full number including the fractional part, 4.321.
@cindex POSIX mode
Some earlier versions of @command{gawk} fully complied with this aspect
of the standard. However, many users in non-English locales complained
about this behavior, because their data used a period as the decimal
point, so the default behavior was restored to use a period as the
decimal point character. You can use the @option{--use-lc-numeric}
option (@pxref{Options}) to force @command{gawk} to use the locale's
decimal point character. (@command{gawk} also uses the locale's decimal
point character when in POSIX mode, either via @option{--posix} or the
@env{POSIXLY_CORRECT} environment variable, as shown previously.)
@ref{table-locale-affects} describes the cases in which the locale's decimal
point character is used and when a period is used. Some of these
features have not been described yet.
@float Table,table-locale-affects
@caption{Locale decimal point versus a period}
@multitable @columnfractions .15 .20 .45
@headitem Feature @tab Default @tab @option{--posix} or @option{--use-lc-numeric}
@item @code{%'g} @tab Use locale @tab Use locale
@item @code{%g} @tab Use period @tab Use locale
@item Input @tab Use period @tab Use locale
@item @code{strtonum()} @tab Use period @tab Use locale
@end multitable
@end float
Finally, modern-day formal standards and the IEEE standard floating-point
representation can have an unusual but important effect on the way
@command{gawk} converts some special string values to numbers. The details
are presented in @ref{POSIX Floating Point Problems}.
@node All Operators
@section Operators: Doing Something with Values
This @value{SECTION} introduces the @dfn{operators} that make use
of the values provided by constants and variables.
@menu
* Arithmetic Ops:: Arithmetic operations (@samp{+}, @samp{-},
etc.)
* Concatenation:: Concatenating strings.
* Assignment Ops:: Changing the value of a variable or a field.
* Increment Ops:: Incrementing the numeric value of a variable.
@end menu
@node Arithmetic Ops
@subsection Arithmetic Operators
@cindex arithmetic operators
@cindex operators @subentry arithmetic
@c @cindex addition
@c @cindex subtraction
@c @cindex multiplication
@c @cindex division
@c @cindex remainder
@c @cindex quotient
@c @cindex exponentiation
The @command{awk} language uses the common arithmetic operators when
evaluating expressions. All of these arithmetic operators follow normal
precedence rules and work as you would expect them to.
The following example uses a file named @file{grades}, which contains
a list of student names as well as three test scores per student (it's
a small class):
@example
Pat 100 97 58
Sandy 84 72 93
Chris 72 92 89
@end example
@noindent
This program takes the file @file{grades} and prints the average
of the scores:
@example
$ @kbd{awk '@{ sum = $2 + $3 + $4 ; avg = sum / 3}
> @kbd{print $1, avg @}' grades}
@print{} Pat 85
@print{} Sandy 83
@print{} Chris 84.3333
@end example
The following list provides the arithmetic operators in @command{awk},
in order from the highest precedence to the lowest:
@table @code
@cindex common extensions @subentry @code{**} operator
@cindex extensions @subentry common @subentry @code{**} operator
@cindex POSIX @command{awk} @subentry arithmetic operators and
@item @var{x} ^ @var{y}
@itemx @var{x} ** @var{y}
Exponentiation; @var{x} raised to the @var{y} power. @samp{2 ^ 3} has
the value eight; the character sequence @samp{**} is equivalent to
@samp{^}. @value{COMMONEXT}
@item - @var{x}
Negation.
@item + @var{x}
Unary plus; the expression is converted to a number.
@item @var{x} * @var{y}
Multiplication.
@cindex troubleshooting @subentry division
@cindex division
@item @var{x} / @var{y}
Division; because all numbers in @command{awk} are floating-point
numbers, the result is @emph{not} rounded to an integer---@samp{3 / 4} has
the value 0.75. (It is a common mistake, especially for C programmers,
to forget that @emph{all} numbers in @command{awk} are floating point,
and that division of integer-looking constants produces a real number,
not an integer.)
@item @var{x} % @var{y}
Remainder; further discussion is provided in the text, just
after this list.
@item @var{x} + @var{y}
Addition.
@item @var{x} - @var{y}
Subtraction.
@end table
Unary plus and minus have the same precedence,
the multiplication operators all have the same precedence, and
addition and subtraction have the same precedence.
@cindex differences in @command{awk} and @command{gawk} @subentry trunc-mod operation
@cindex trunc-mod operation
When computing the remainder of @samp{@var{x} % @var{y}},
the quotient is rounded toward zero to an integer and
multiplied by @var{y}. This result is subtracted from @var{x};
this operation is sometimes known as ``trunc-mod.'' The following
relation always holds:
@example
b * int(a / b) + (a % b) == a
@end example
One possibly undesirable effect of this definition of remainder is that
@samp{@var{x} % @var{y}} is negative if @var{x} is negative. Thus:
@example
-17 % 8 = -1
@end example
In other @command{awk} implementations, the signedness of the remainder
may be machine-dependent.
@c FIXME !!! what does posix say?
@cindex portability @subentry @code{**} operator and
@cindex @code{*} (asterisk) @subentry @code{**} operator
@cindex asterisk (@code{*}) @subentry @code{**} operator
@quotation NOTE
The POSIX standard only specifies the use of @samp{^}
for exponentiation.
For maximum portability, do not use the @samp{**} operator.
@end quotation
@node Concatenation
@subsection String Concatenation
@cindex Kernighan, Brian
@quotation
@i{It seemed like a good idea at the time.}
@author Brian Kernighan
@end quotation
@cindex string @subentry operators
@cindex operators @subentry string
@cindex concatenating
There is only one string operation: concatenation. It does not have a
specific operator to represent it. Instead, concatenation is performed by
writing expressions next to one another, with no operator. For example:
@example
$ @kbd{awk '@{ print "Field number one: " $1 @}' mail-list}
@print{} Field number one: Amelia
@print{} Field number one: Anthony
@dots{}
@end example
Without the space in the string constant after the @samp{:}, the line
runs together. For example:
@example
$ @kbd{awk '@{ print "Field number one:" $1 @}' mail-list}
@print{} Field number one:Amelia
@print{} Field number one:Anthony
@dots{}
@end example
@cindex troubleshooting @subentry string concatenation
Because string concatenation does not have an explicit operator, it is
often necessary to ensure that it happens at the right time by using
parentheses to enclose the items to concatenate. For example,
you might expect that the
following code fragment concatenates @code{file} and @code{name}:
@example
file = "file"
name = "name"
print "something meaningful" > file name
@end example
@cindex Brian Kernighan's @command{awk}
@cindex @command{mawk} utility
@noindent
This produces a syntax error with some versions of Unix
@command{awk}.@footnote{It happens that BWK
@command{awk}, @command{gawk}, and @command{mawk} all ``get it right,''
but you should not rely on this.}
It is necessary to use the following:
@example
print "something meaningful" > (file name)
@end example
@cindex order of evaluation, concatenation
@cindex evaluation order @subentry concatenation
@cindex side effects
Parentheses should be used around concatenation in all but the
most common contexts, such as on the righthand side of @samp{=}.
Be careful about the kinds of expressions used in string concatenation.
In particular, the order of evaluation of expressions used for concatenation
is undefined in the @command{awk} language. Consider this example:
@example
BEGIN @{
a = "don't"
print (a " " (a = "panic"))
@}
@end example
@noindent
It is not defined whether the second assignment to @code{a} happens
before or after the value of @code{a} is retrieved for producing the
concatenated value. The result could be either @samp{don't panic},
or @samp{panic panic}.
@c see test/nasty.awk for a worse example
The precedence of concatenation, when mixed with other operators, is often
counter-intuitive. Consider this example:
@ignore
> To: bug-gnu-utils@@gnu.org
> CC: arnold@@gnu.org
> Subject: gawk 3.0.4 bug with {print -12 " " -24}
> From: Russell Schulz <Russell_Schulz@locutus.ofB.ORG>
> Date: Tue, 8 Feb 2000 19:56:08 -0700
>
> gawk 3.0.4 on NT gives me:
>
> prompt> cat bad.awk
> BEGIN { print -12 " " -24; }
>
> prompt> gawk -f bad.awk
> -12-24
>
> when I would expect
>
> -12 -24
>
> I have not investigated the source, or other implementations. The
> bug is there on my NT and DOS versions 2.15.6 .
@end ignore
@example
$ @kbd{awk 'BEGIN @{ print -12 " " -24 @}'}
@print{} -12-24
@end example
This ``obviously'' is concatenating @minus{}12, a space, and @minus{}24.
But where did the space disappear to?
The answer lies in the combination of operator precedences and
@command{awk}'s automatic conversion rules. To get the desired result,
write the program this way:
@example
$ @kbd{awk 'BEGIN @{ print -12 " " (-24) @}'}
@print{} -12 -24
@end example
This forces @command{awk} to treat the @samp{-} on the @samp{-24} as unary.
Otherwise, it's parsed as follows:
@display
@minus{}12 (@code{"@ "} @minus{} 24)
@result{} @minus{}12 (0 @minus{} 24)
@result{} @minus{}12 (@minus{}24)
@result{} @minus{}12@minus{}24
@end display
As mentioned earlier,
when mixing concatenation with other operators, @emph{parenthesize}. Otherwise,
you're never quite sure what you'll get.
@node Assignment Ops
@subsection Assignment Expressions
@cindex assignment operators
@cindex operators @subentry assignment
@cindex expressions @subentry assignment
@cindex @code{=} (equals sign) @subentry @code{=} operator
@cindex equals sign (@code{=}) @subentry @code{=} operator
An @dfn{assignment} is an expression that stores a (usually different)
value into a variable. For example, let's assign the value one to the variable
@code{z}:
@example
z = 1
@end example
After this expression is executed, the variable @code{z} has the value one.
Whatever old value @code{z} had before the assignment is forgotten.
Assignments can also store string values. For example, the
following stores
the value @code{"this food is good"} in the variable @code{message}:
@example
thing = "food"
predicate = "good"
message = "this " thing " is " predicate
@end example
@noindent
@cindex side effects @subentry assignment expressions
This also illustrates string concatenation.
The @samp{=} sign is called an @dfn{assignment operator}. It is the
simplest assignment operator because the value of the righthand
operand is stored unchanged.
Most operators (addition, concatenation, and so on) have no effect
except to compute a value. If the value isn't used, there's no reason to
use the operator. An assignment operator is different; it does
produce a value, but even if you ignore it, the assignment still
makes itself felt through the alteration of the variable. We call this
a @dfn{side effect}.
@cindex lvalues/rvalues
@cindex rvalues/lvalues
@cindex assignment operators @subentry lvalues/rvalues
@cindex operators @subentry assignment
The lefthand operand of an assignment need not be a variable
(@pxref{Variables}); it can also be a field
(@pxref{Changing Fields}) or
an array element (@pxref{Arrays}).
These are all called @dfn{lvalues},
which means they can appear on the lefthand side of an assignment operator.
The righthand operand may be any expression; it produces the new value
that the assignment stores in the specified variable, field, or array
element. (Such values are called @dfn{rvalues}.)
@cindex variables @subentry types of
It is important to note that variables do @emph{not} have permanent types.
A variable's type is simply the type of whatever value was last assigned
to it. In the following program fragment, the variable
@code{foo} has a numeric value at first, and a string value later on:
@example
@group
foo = 1
print foo
@end group
@group
foo = "bar"
print foo
@end group
@end example
@noindent
When the second assignment gives @code{foo} a string value, the fact that
it previously had a numeric value is forgotten.
String values that do not begin with a digit have a numeric value of
zero. After executing the following code, the value of @code{foo} is five:
@example
foo = "a string"
foo = foo + 5
@end example
@quotation NOTE
Using a variable as a number and then later as a string
can be confusing and is poor programming style. The previous two examples
illustrate how @command{awk} works, @emph{not} how you should write your
programs!
@end quotation
An assignment is an expression, so it has a value---the same value that
is assigned. Thus, @samp{z = 1} is an expression with the value one.
One consequence of this is that you can write multiple assignments together,
such as:
@example
x = y = z = 5
@end example
@noindent
This example stores the value five in all three variables
(@code{x}, @code{y}, and @code{z}).
It does so because the
value of @samp{z = 5}, which is five, is stored into @code{y} and then
the value of @samp{y = z = 5}, which is five, is stored into @code{x}.
Assignments may be used anywhere an expression is called for. For
example, it is valid to write @samp{x != (y = 1)} to set @code{y} to one,
and then test whether @code{x} equals one. But this style tends to make
programs hard to read; such nesting of assignments should be avoided,
except perhaps in a one-shot program.
@cindex @code{+} (plus sign) @subentry @code{+=} operator
@cindex plus sign (@code{+}) @subentry @code{+=} operator
Aside from @samp{=}, there are several other assignment operators that
do arithmetic with the old value of the variable. For example, the
operator @samp{+=} computes a new value by adding the righthand value
to the old value of the variable. Thus, the following assignment adds
five to the value of @code{foo}:
@example
foo += 5
@end example
@noindent
This is equivalent to the following:
@example
foo = foo + 5
@end example
@noindent
Use whichever makes the meaning of your program clearer.
There are situations where using @samp{+=} (or any assignment operator)
is @emph{not} the same as simply repeating the lefthand operand in the
righthand expression. For example:
@cindex Rankin, Pat
@example
@group
# Thanks to Pat Rankin for this example
BEGIN @{
foo[rand()] += 5
for (x in foo)
print x, foo[x]
@end group
@group
bar[rand()] = bar[rand()] + 5
for (x in bar)
print x, bar[x]
@}
@end group
@end example
@cindex operators @subentry assignment @subentry evaluation order
@cindex assignment operators @subentry evaluation order
@noindent
The indices of @code{bar} are practically guaranteed to be different, because
@code{rand()} returns different values each time it is called.
(Arrays and the @code{rand()} function haven't been covered yet.
@xref{Arrays},
and
@ifnotdocbook
@pxref{Numeric Functions}
@end ifnotdocbook
@ifdocbook
@ref{Numeric Functions}
@end ifdocbook
for more information.)
This example illustrates an important fact about assignment
operators: the lefthand expression is only evaluated @emph{once}.
It is up to the implementation as to which expression is evaluated
first, the lefthand or the righthand.
Consider this example:
@example
i = 1
a[i += 2] = i + 1
@end example
@noindent
The value of @code{a[3]} could be either two or four.
@ref{table-assign-ops} lists the arithmetic assignment operators. In each
case, the righthand operand is an expression whose value is converted
to a number.
@cindex @code{-} (hyphen) @subentry @code{-=} operator
@cindex hyphen (@code{-}) @subentry @code{-=} operator
@cindex @code{*} (asterisk) @subentry @code{*=} operator
@cindex asterisk (@code{*}) @subentry @code{*=} operator
@cindex @code{/} (forward slash) @subentry @code{/=} operator
@cindex forward slash (@code{/}) @subentry @code{/=} operator
@cindex @code{%} (percent sign) @subentry @code{%=} operator
@cindex percent sign (@code{%}) @subentry @code{%=} operator
@cindex @code{^} (caret) @subentry @code{^=} operator
@cindex caret (@code{^}) @subentry @code{^=} operator
@cindex @code{*} (asterisk) @subentry @code{**=} operator
@cindex asterisk (@code{*}) @subentry @code{**=} operator
@float Table,table-assign-ops
@caption{Arithmetic assignment operators}
@multitable @columnfractions .30 .70
@headitem Operator @tab Effect
@item @var{lvalue} @code{+=} @var{increment} @tab Add @var{increment} to the value of @var{lvalue}.
@item @var{lvalue} @code{-=} @var{decrement} @tab Subtract @var{decrement} from the value of @var{lvalue}.
@item @var{lvalue} @code{*=} @var{coefficient} @tab Multiply the value of @var{lvalue} by @var{coefficient}.
@item @var{lvalue} @code{/=} @var{divisor} @tab Divide the value of @var{lvalue} by @var{divisor}.
@item @var{lvalue} @code{%=} @var{modulus} @tab Set @var{lvalue} to its remainder by @var{modulus}.
@cindex common extensions @subentry @code{**=} operator
@cindex extensions @subentry common @subentry @code{**=} operator
@cindex @command{awk} @subentry language, POSIX version
@cindex POSIX @command{awk}
@item @var{lvalue} @code{^=} @var{power} @tab Raise @var{lvalue} to the power @var{power}.
@item @var{lvalue} @code{**=} @var{power} @tab Raise @var{lvalue} to the power @var{power}. @value{COMMONEXT}
@end multitable
@end float
@cindex POSIX @command{awk} @subentry @code{**=} operator and
@cindex portability @subentry @code{**=} operator and
@quotation NOTE
Only the @samp{^=} operator is specified by POSIX.
For maximum portability, do not use the @samp{**=} operator.
@end quotation
@cindex sidebar @subentry Syntactic Ambiguities Between @samp{/=} and Regular Expressions
@ifdocbook
@docbook
<sidebar><title>Syntactic Ambiguities Between @samp{/=} and Regular Expressions</title>
@end docbook
@cindex dark corner @subentry regexp constants @subentry @code{/=} operator and
@cindex @code{/} (forward slash) @subentry @code{/=} operator @subentry vs. @code{/=@dots{}/} regexp constant
@cindex forward slash (@code{/}) @subentry @code{/=} operator @subentry vs. @code{/=@dots{}/} regexp constant
@cindex regexp constants @subentry @code{/=@dots{}/} @subentry @code{/=} operator and
@c derived from email from "Nelson H. F. Beebe" <beebe@math.utah.edu>
@c Date: Mon, 1 Sep 1997 13:38:35 -0600 (MDT)
@cindex dark corner @subentry @code{/=} operator vs. @code{/=@dots{}/} regexp constant
@cindex ambiguity, syntactic: @code{/=} operator vs. @code{/=@dots{}/} regexp constant
@cindex syntactic ambiguity: @code{/=} operator vs. @code{/=@dots{}/} regexp constant
@cindex @code{/=} operator vs. @code{/=@dots{}/} regexp constant
There is a syntactic ambiguity between the @code{/=} assignment
operator and regexp constants whose first character is an @samp{=}.
@value{DARKCORNER}
This is most notable in some commercial @command{awk} versions.
For example:
@example
$ @kbd{awk /==/ /dev/null}
@error{} awk: syntax error at source line 1
@error{} context is
@error{} >>> /= <<<
@error{} awk: bailing out at source line 1
@end example
@noindent
A workaround is:
@example
awk '/[=]=/' /dev/null
@end example
@command{gawk} does not have this problem; BWK @command{awk}
and @command{mawk} also do not.
@docbook
</sidebar>
@end docbook
@end ifdocbook
@ifnotdocbook
@cartouche
@center @b{Syntactic Ambiguities Between @samp{/=} and Regular Expressions}
@cindex dark corner @subentry regexp constants @subentry @code{/=} operator and
@cindex @code{/} (forward slash) @subentry @code{/=} operator @subentry vs. @code{/=@dots{}/} regexp constant
@cindex forward slash (@code{/}) @subentry @code{/=} operator @subentry vs. @code{/=@dots{}/} regexp constant
@cindex regexp constants @subentry @code{/=@dots{}/} @subentry @code{/=} operator and
@c derived from email from "Nelson H. F. Beebe" <beebe@math.utah.edu>
@c Date: Mon, 1 Sep 1997 13:38:35 -0600 (MDT)
@cindex dark corner @subentry @code{/=} operator vs. @code{/=@dots{}/} regexp constant
@cindex ambiguity, syntactic: @code{/=} operator vs. @code{/=@dots{}/} regexp constant
@cindex syntactic ambiguity: @code{/=} operator vs. @code{/=@dots{}/} regexp constant
@cindex @code{/=} operator vs. @code{/=@dots{}/} regexp constant
There is a syntactic ambiguity between the @code{/=} assignment
operator and regexp constants whose first character is an @samp{=}.
@value{DARKCORNER}
This is most notable in some commercial @command{awk} versions.
For example:
@example
$ @kbd{awk /==/ /dev/null}
@error{} awk: syntax error at source line 1
@error{} context is
@error{} >>> /= <<<
@error{} awk: bailing out at source line 1
@end example
@noindent
A workaround is:
@example
awk '/[=]=/' /dev/null
@end example
@command{gawk} does not have this problem; BWK @command{awk}
and @command{mawk} also do not.
@end cartouche
@end ifnotdocbook
@node Increment Ops
@subsection Increment and Decrement Operators
@cindex increment operators
@cindex operators @subentry decrement/increment
@dfn{Increment} and @dfn{decrement operators} increase or decrease the value of
a variable by one. An assignment operator can do the same thing, so
the increment operators add no power to the @command{awk} language; however, they
are convenient abbreviations for very common operations.
@cindex side effects
@cindex @code{+} (plus sign) @subentry @code{++} operator
@cindex plus sign (@code{+}) @subentry @code{++} operator
@cindex side effects @subentry decrement/increment operators
The operator used for adding one is written @samp{++}. It can be used to increment
a variable either before or after taking its value.
To @dfn{pre-increment} a variable @code{v}, write @samp{++v}. This adds
one to the value of @code{v}---that new value is also the value of the
expression. (The assignment expression @samp{v += 1} is completely equivalent.)
Writing the @samp{++} after the variable specifies @dfn{post-increment}. This
increments the variable value just the same; the difference is that the
value of the increment expression itself is the variable's @emph{old}
value. Thus, if @code{foo} has the value four, then the expression @samp{foo++}
has the value four, but it changes the value of @code{foo} to five.
In other words, the operator returns the old value of the variable,
but with the side effect of incrementing it.
The post-increment @samp{foo++} is nearly the same as writing @samp{(foo
+= 1) - 1}. It is not perfectly equivalent because all numbers in
@command{awk} are floating point---in floating point, @samp{foo + 1 - 1} does
not necessarily equal @code{foo}. But the difference is minute as
long as you stick to numbers that are fairly small (less than
@iftex
@math{10^{12}}).
@end iftex
@ifinfo
10e12).
@end ifinfo
@ifnottex
@ifnotinfo
10@sup{12}).
@end ifnotinfo
@end ifnottex
@cindex @code{$} (dollar sign) @subentry incrementing fields and arrays
@cindex dollar sign (@code{$}) @subentry incrementing fields and arrays
Fields and array elements are incremented
just like variables. (Use @samp{$(i++)} when you want to do a field reference
and a variable increment at the same time. The parentheses are necessary
because of the precedence of the field reference operator @samp{$}.)
@cindex decrement operators
The decrement operator @samp{--} works just like @samp{++}, except that
it subtracts one instead of adding it. As with @samp{++}, it can be used before
the lvalue to pre-decrement or after it to post-decrement.
Following is a summary of increment and decrement expressions:
@table @code
@cindex @code{+} (plus sign) @subentry @code{++} operator
@cindex plus sign (@code{+}) @subentry @code{++} operator
@item ++@var{lvalue}
Increment @var{lvalue}, returning the new value as the
value of the expression.
@item @var{lvalue}++
Increment @var{lvalue}, returning the @emph{old} value of @var{lvalue}
as the value of the expression.
@cindex @code{-} (hyphen) @subentry @code{--} operator
@cindex hyphen (@code{-}) @subentry @code{--} operator
@item --@var{lvalue}
Decrement @var{lvalue}, returning the new value as the
value of the expression.
(This expression is
like @samp{++@var{lvalue}}, but instead of adding, it subtracts.)
@item @var{lvalue}--
Decrement @var{lvalue}, returning the @emph{old} value of @var{lvalue}
as the value of the expression.
(This expression is
like @samp{@var{lvalue}++}, but instead of adding, it subtracts.)
@end table
@cindex sidebar @subentry Operator Evaluation Order
@ifdocbook
@docbook
<sidebar><title>Operator Evaluation Order</title>
@end docbook
@cindex precedence
@cindex operators @subentry precedence of
@cindex portability @subentry operators
@cindex evaluation order
@cindex Marx, Groucho
@quotation
@i{Doctor, it hurts when I do this!@*
Then don't do that!}
@author Groucho Marx
@end quotation
@noindent
What happens for something like the following?
@example
b = 6
print b += b++
@end example
@noindent
Or something even stranger?
@example
b = 6
b += ++b + b++
print b
@end example
@cindex side effects
In other words, when do the various side effects prescribed by the
postfix operators (@samp{b++}) take effect?
When side effects happen is @dfn{implementation-defined}.
In other words, it is up to the particular version of @command{awk}.
The result for the first example may be 12 or 13, and for the second, it
may be 22 or 23.
In short, doing things like this is not recommended and definitely
not anything that you can rely upon for portability.
You should avoid such things in your own programs.
@c You'll sleep better at night and be able to look at yourself
@c in the mirror in the morning.
@docbook
</sidebar>
@end docbook
@end ifdocbook
@ifnotdocbook
@cartouche
@center @b{Operator Evaluation Order}
@cindex precedence
@cindex operators @subentry precedence of
@cindex portability @subentry operators
@cindex evaluation order
@cindex Marx, Groucho
@quotation
@i{Doctor, it hurts when I do this!@*
Then don't do that!}
@author Groucho Marx
@end quotation
@noindent
What happens for something like the following?
@example
b = 6
print b += b++
@end example
@noindent
Or something even stranger?
@example
b = 6
b += ++b + b++
print b
@end example
@cindex side effects
In other words, when do the various side effects prescribed by the
postfix operators (@samp{b++}) take effect?
When side effects happen is @dfn{implementation-defined}.
In other words, it is up to the particular version of @command{awk}.
The result for the first example may be 12 or 13, and for the second, it
may be 22 or 23.
In short, doing things like this is not recommended and definitely
not anything that you can rely upon for portability.
You should avoid such things in your own programs.
@c You'll sleep better at night and be able to look at yourself
@c in the mirror in the morning.
@end cartouche
@end ifnotdocbook
@node Truth Values and Conditions
@section Truth Values and Conditions
In certain contexts, expression values also serve as ``truth values''; i.e.,
they determine what should happen next as the program runs. This
@value{SECTION} describes how @command{awk} defines ``true'' and ``false''
and how values are compared.
@menu
* Truth Values:: What is ``true'' and what is ``false''.
* Typing and Comparison:: How variables acquire types and how this
affects comparison of numbers and strings with
@samp{<}, etc.
* Boolean Ops:: Combining comparison expressions using boolean
operators @samp{||} (``or''), @samp{&&}
(``and'') and @samp{!} (``not'').
* Conditional Exp:: Conditional expressions select between two
subexpressions under control of a third
subexpression.
@end menu
@node Truth Values
@subsection True and False in @command{awk}
@cindex truth values
@cindex logical false/true
@cindex false, logical
@cindex true, logical
@cindex null strings
Many programming languages have a special representation for the concepts
of ``true'' and ``false.'' Such languages usually use the special
constants @code{true} and @code{false}, or perhaps their uppercase
equivalents.
However, @command{awk} is different.
It borrows a very simple concept of true and
false from C. In @command{awk}, any nonzero numeric value @emph{or} any
nonempty string value is true. Any other value (zero or the null
string, @code{""}) is false. The following program prints @samp{A strange
truth value} three times:
@example
BEGIN @{
if (3.1415927)
print "A strange truth value"
if ("Four Score And Seven Years Ago")
print "A strange truth value"
if (j = 57)
print "A strange truth value"
@}
@end example
@cindex dark corner @subentry @code{"0"} is actually true
There is a surprising consequence of the ``nonzero or non-null'' rule:
the string constant @code{"0"} is actually true, because it is non-null.
@value{DARKCORNER}
@node Typing and Comparison
@subsection Variable Typing and Comparison Expressions
@quotation
@i{The Guide is definitive. Reality is frequently inaccurate.}
@author Douglas Adams, @cite{The Hitchhiker's Guide to the Galaxy}
@end quotation
@c 2/2015: Antonio Colombo points out that this is really from
@c The Restaurant at the End of the Universe. But I'm going to
@c leave it alone.
@cindex comparison expressions
@cindex expressions @subentry comparison
@cindex expressions, matching @seeentry{comparison expressions}
@cindex matching @subentry expressions @seeentry{comparison expressions}
@cindex relational operators @seeentry{comparison operators}
@cindex operators, relational @seeentry{operators, comparison}
@cindex variables @subentry types of @subentry comparison expressions and
Unlike in other programming languages, in @command{awk} variables do not have a
fixed type. Instead, they can be either a number or a string, depending
upon the value that is assigned to them.
We look now at how variables are typed, and how @command{awk}
compares variables.
@menu
* Variable Typing:: String type versus numeric type.
* Comparison Operators:: The comparison operators.
* POSIX String Comparison:: String comparison with POSIX rules.
@end menu
@node Variable Typing
@subsubsection String Type versus Numeric Type
Scalar objects in @command{awk} (variables, array elements, and fields)
are @emph{dynamically} typed. This means their type can change as the
program runs, from @dfn{untyped} before any use,@footnote{@command{gawk}
calls this @dfn{unassigned}, as the following example shows.} to string
or number, and then from string to number or number to string, as the
program progresses. (@command{gawk} also provides regexp-typed scalars,
but let's ignore that for now; @pxref{Strong Regexp Constants}.)
You can't do much with untyped variables, other than tell that they
are untyped. The following program tests @code{a} against @code{""}
and @code{0}; the test succeeds when @code{a} has never been assigned
a value. It also uses the built-in @code{typeof()} function
(not presented yet; @pxref{Type Functions}) to show @code{a}'s type:
@example
$ @kbd{gawk 'BEGIN @{ print (a == "" && a == 0 ?}
> @kbd{"a is untyped" : "a has a type!") ; print typeof(a) @}'}
@print{} a is untyped
@print{} unassigned
@end example
A scalar has numeric type when assigned a numeric value,
such as from a numeric constant, or from another scalar
with numeric type:
@example
$ @kbd{gawk 'BEGIN @{ a = 42 ; print typeof(a)}
> @kbd{b = a ; print typeof(b) @}'}
number
number
@end example
Similarly, a scalar has string type when assigned a string
value, such as from a string constant, or from another scalar
with string type:
@example
$ @kbd{gawk 'BEGIN @{ a = "forty two" ; print typeof(a)}
> @kbd{b = a ; print typeof(b) @}'}
string
string
@end example
So far, this is all simple and straightforward. What happens, though,
when @command{awk} has to process data from a user? Let's start with
field data. What should the following command produce as output?
@example
echo hello | awk '@{ printf("%s %s < 42\n", $1,
($1 < 42 ? "is" : "is not")) @}'
@end example
@noindent
Since @samp{hello} is alphabetic data, @command{awk} can only do a string
comparison. Internally, it converts @code{42} into @code{"42"} and compares
the two string values @code{"hello"} and @code{"42"}. Here's the result:
@example
$ @kbd{echo hello | awk '@{ printf("%s %s < 42\n", $1,}
> @kbd{ ($1 < 42 ? "is" : "is not")) @}'}
@print{} hello is not < 42
@end example
However, what happens when data from a user @emph{looks like} a number?
On the one hand, in reality, the input data consists of characters, not
binary numeric
values. But, on the other hand, the data looks numeric, and @command{awk}
really ought to treat it as such. And indeed, it does:
@example
$ @kbd{echo 37 | awk '@{ printf("%s %s < 42\n", $1,}
> @kbd{ ($1 < 42 ? "is" : "is not")) @}'}
@print{} 37 is < 42
@end example
Here are the rules for when @command{awk}
treats data as a number, and for when it treats data as a string.
@cindex numeric @subentry strings
@cindex strings @subentry numeric
@cindex POSIX @command{awk} @subentry numeric strings and
The POSIX standard uses the term @dfn{numeric string} for input data that
looks numeric. The @samp{37} in the previous example is a numeric string.
So what is the type of a numeric string? Answer: numeric.
The type of a variable is important because the types of two variables
determine how they are compared.
Variable typing follows these definitions and rules:
@itemize @value{BULLET}
@item
A numeric constant or the result of a numeric operation has the @dfn{numeric}
attribute.
@item
A string constant or the result of a string operation has the @dfn{string}
attribute.
@item
Fields, @code{getline} input, @code{FILENAME}, @code{ARGV} elements,
@code{ENVIRON} elements, and the elements of an array created by
@code{match()}, @code{split()}, and @code{patsplit()} that are numeric
strings have the @dfn{strnum} attribute.@footnote{Thus, a POSIX
numeric string and @command{gawk}'s strnum are the same thing.}
Otherwise, they have
the @dfn{string} attribute. Uninitialized variables also have the
@dfn{strnum} attribute.
@item
Attributes propagate across assignments but are not changed by
any use.
@c (Although a use may cause the entity to acquire an additional
@c value such that it has both a numeric and string value, this leaves the
@c attribute unchanged.)
@c This is important but not relevant
@end itemize
The last rule is particularly important. In the following program,
@code{a} has numeric type, even though it is later used in a string
operation:
@example
BEGIN @{
a = 12.345
b = a " is a cute number"
print b
@}
@end example
When two operands are compared, either string comparison or numeric comparison
may be used. This depends upon the attributes of the operands, according to the
following symmetric matrix:
@c thanks to Karl Berry, kb@cs.umb.edu, for major help with TeX tables
@tex
\centerline{
\vbox{\bigskip % space above the table (about 1 linespace)
% Because we have vertical rules, we can't let TeX insert interline space
% in its usual way.
\offinterlineskip
%
% Define the table template. & separates columns, and \cr ends the
% template (and each row). # is replaced by the text of that entry on
% each row. The template for the first column breaks down like this:
% \strut -- a way to make each line have the height and depth
% of a normal line of type, since we turned off interline spacing.
% \hfil -- infinite glue; has the effect of right-justifying in this case.
% # -- replaced by the text (for instance, `STRNUM', in the last row).
% \quad -- about the width of an `M'. Just separates the columns.
%
% The second column (\vrule#) is what generates the vertical rule that
% spans table rows.
%
% The doubled && before the next entry means `repeat the following
% template as many times as necessary on each line' -- in our case, twice.
%
% The template itself, \quad#\hfil, left-justifies with a little space before.
%
\halign{\strut\hfil#\quad&\vrule#&&\quad#\hfil\cr
&&STRING &NUMERIC &STRNUM\cr
% The \omit tells TeX to skip inserting the template for this column on
% this particular row. In this case, we only want a little extra space
% to separate the heading row from the rule below it. the depth 2pt --
% `\vrule depth 2pt' is that little space.
\omit &depth 2pt\cr
% This is the horizontal rule below the heading. Since it has nothing to
% do with the columns of the table, we use \noalign to get it in there.
\noalign{\hrule}
% Like above, this time a little more space.
\omit &depth 4pt\cr
% The remaining rows have nothing special about them.
STRING &&string &string &string\cr
NUMERIC &&string &numeric &numeric\cr
STRNUM &&string &numeric &numeric\cr
}}}
@end tex
@ifnottex
@ifnotdocbook
@verbatim
+----------------------------------------------
| STRING NUMERIC STRNUM
--------+----------------------------------------------
|
STRING | string string string
|
NUMERIC | string numeric numeric
|
STRNUM | string numeric numeric
--------+----------------------------------------------
@end verbatim
@end ifnotdocbook
@end ifnottex
@docbook
<informaltable>
<tgroup cols="4">
<colspec colname="1" align="left"/>
<colspec colname="2" align="left"/>
<colspec colname="3" align="left"/>
<colspec colname="4" align="left"/>
<thead>
<row>
<entry/>
<entry>STRING</entry>
<entry>NUMERIC</entry>
<entry>STRNUM</entry>
</row>
</thead>
<tbody>
<row>
<entry><emphasis role="bold">STRING</emphasis></entry>
<entry>string</entry>
<entry>string</entry>
<entry>string</entry>
</row>
<row>
<entry><emphasis role="bold">NUMERIC</emphasis></entry>
<entry>string</entry>
<entry>numeric</entry>
<entry>numeric</entry>
</row>
<row>
<entry><emphasis role="bold">STRNUM</emphasis></entry>
<entry>string</entry>
<entry>numeric</entry>
<entry>numeric</entry>
</row>
</tbody>
</tgroup>
</informaltable>
@end docbook
The basic idea is that user input that looks numeric---and @emph{only}
user input---should be treated as numeric, even though it is actually
made of characters and is therefore also a string.
Thus, for example, the string constant @w{@code{" +3.14"}},
when it appears in program source code,
is a string---even though it looks numeric---and
is @emph{never} treated as a number for comparison
purposes.
In short, when one operand is a ``pure'' string, such as a string
constant, then a string comparison is performed. Otherwise, a
numeric comparison is performed.
(The primary difference between a number and a strnum is that
for strnums @command{gawk} preserves the original string value that
the scalar had when it came in.)
This point bears additional emphasis:
Input that looks numeric @emph{is} numeric.
All other input is treated as strings.
Thus, the six-character input string @w{@samp{ +3.14}} receives the
strnum attribute. In contrast, the eight characters
@w{@code{" +3.14"}} appearing in program text comprise a string constant.
The following examples print @samp{1} when the comparison between
the two different constants is true, and @samp{0} otherwise:
@c 22.9.2014: Tested with mawk and BWK awk, got same results.
@example
$ @kbd{echo ' +3.14' | awk '@{ print($0 == " +3.14") @}'} @ii{True}
@print{} 1
$ @kbd{echo ' +3.14' | awk '@{ print($0 == "+3.14") @}'} @ii{False}
@print{} 0
$ @kbd{echo ' +3.14' | awk '@{ print($0 == "3.14") @}'} @ii{False}
@print{} 0
$ @kbd{echo ' +3.14' | awk '@{ print($0 == 3.14) @}'} @ii{True}
@print{} 1
$ @kbd{echo ' +3.14' | awk '@{ print($1 == " +3.14") @}'} @ii{False}
@print{} 0
$ @kbd{echo ' +3.14' | awk '@{ print($1 == "+3.14") @}'} @ii{True}
@print{} 1
$ @kbd{echo ' +3.14' | awk '@{ print($1 == "3.14") @}'} @ii{False}
@print{} 0
$ @kbd{echo ' +3.14' | awk '@{ print($1 == 3.14) @}'} @ii{True}
@print{} 1
@end example
You can see the type of an input field (or other user input)
using @code{typeof()}:
@example
$ @kbd{echo hello 37 | gawk '@{ print typeof($1), typeof($2) @}'}
@print{} string strnum
@end example
@node Comparison Operators
@subsubsection Comparison Operators
@cindex operators @subentry comparison
@dfn{Comparison expressions} compare strings or numbers for
relationships such as equality. They are written using @dfn{relational
operators}, which are a superset of those in C.
@ref{table-relational-ops} describes them.
@cindex @code{<} (left angle bracket) @subentry @code{<} operator
@cindex left angle bracket (@code{<}) @subentry @code{<} operator
@cindex @code{<} (left angle bracket) @subentry @code{<=} operator
@cindex left angle bracket (@code{<}) @subentry @code{<=} operator
@cindex @code{>} (right angle bracket) @subentry @code{>=} operator
@cindex right angle bracket (@code{>}) @subentry @code{>=} operator
@cindex @code{>} (right angle bracket) @subentry @code{>} operator
@cindex right angle bracket (@code{>}) @subentry @code{>} operator
@cindex @code{=} (equals sign) @subentry @code{==} operator
@cindex equals sign (@code{=}) @subentry @code{==} operator
@cindex @code{!} (exclamation point) @subentry @code{!=} operator
@cindex exclamation point (@code{!}) @subentry @code{!=} operator
@cindex @code{~} (tilde), @code{~} operator
@cindex tilde (@code{~}), @code{~} operator
@cindex @code{!} (exclamation point) @subentry @code{!~} operator
@cindex exclamation point (@code{!}) @subentry @code{!~} operator
@cindex @code{in} operator
@float Table,table-relational-ops
@caption{Relational operators}
@multitable @columnfractions .25 .75
@headitem Expression @tab Result
@item @var{x} @code{<} @var{y} @tab True if @var{x} is less than @var{y}
@item @var{x} @code{<=} @var{y} @tab True if @var{x} is less than or equal to @var{y}
@item @var{x} @code{>} @var{y} @tab True if @var{x} is greater than @var{y}
@item @var{x} @code{>=} @var{y} @tab True if @var{x} is greater than or equal to @var{y}
@item @var{x} @code{==} @var{y} @tab True if @var{x} is equal to @var{y}
@item @var{x} @code{!=} @var{y} @tab True if @var{x} is not equal to @var{y}
@item @var{x} @code{~} @var{y} @tab True if the string @var{x} matches the regexp denoted by @var{y}
@item @var{x} @code{!~} @var{y} @tab True if the string @var{x} does not match the regexp denoted by @var{y}
@item @var{subscript} @code{in} @var{array} @tab True if the array @var{array} has an element with the subscript @var{subscript}
@end multitable
@end float
Comparison expressions have the value one if true and zero if false.
When comparing operands of mixed types, numeric operands are converted
to strings using the value of @code{CONVFMT}
(@pxref{Conversion}).
Strings are compared
by comparing the first character of each, then the second character of each,
and so on. Thus, @code{"10"} is less than @code{"9"}. If there are two
strings where one is a prefix of the other, the shorter string is less than
the longer one. Thus, @code{"abc"} is less than @code{"abcd"}.
@cindex troubleshooting @subentry @code{==} operator
It is very easy to accidentally mistype the @samp{==} operator and
leave off one of the @samp{=} characters. The result is still valid
@command{awk} code, but the program does not do what is intended:
@example
@group
if (a = b) # oops! should be a == b
@dots{}
else
@dots{}
@end group
@end example
@noindent
Unless @code{b} happens to be zero or the null string, the @code{if}
part of the test always succeeds. Because the operators are
so similar, this kind of error is very difficult to spot when
scanning the source code.
The following list of expressions illustrates the kinds of comparisons
@command{awk} performs, as well as what the result of each comparison is:
@table @code
@item 1.5 <= 2.0
Numeric comparison (true)
@item "abc" >= "xyz"
String comparison (false)
@item 1.5 != " +2"
String comparison (true)
@item "1e2" < "3"
String comparison (true)
@item a = 2; b = "2"
@itemx a == b
String comparison (true)
@item a = 2; b = " +2"
@itemx a == b
String comparison (false)
@end table
In this example:
@example
$ @kbd{echo 1e2 3 | awk '@{ print ($1 < $2) ? "true" : "false" @}'}
@print{} false
@end example
@cindex comparison expressions @subentry string vs.@: regexp
@c @cindex string comparison vs.@: regexp comparison
@c @cindex regexp comparison vs.@: string comparison
@noindent
the result is @samp{false} because both @code{$1} and @code{$2}
are user input. They are numeric strings---therefore both have
the strnum attribute, dictating a numeric comparison.
The purpose of the comparison rules and the use of numeric strings is
to attempt to produce the behavior that is ``least surprising,'' while
still ``doing the right thing.''
String comparisons and regular expression comparisons are very different.
For example:
@example
x == "foo"
@end example
@noindent
has the value one, or is true if the variable @code{x}
is precisely @samp{foo}. By contrast:
@example
x ~ /foo/
@end example
@noindent
has the value one if @code{x} contains @samp{foo}, such as
@code{"Oh, what a fool am I!"}.
@cindex @code{~} (tilde), @code{~} operator
@cindex tilde (@code{~}), @code{~} operator
@cindex @code{!} (exclamation point) @subentry @code{!~} operator
@cindex exclamation point (@code{!}) @subentry @code{!~} operator
The righthand operand of the @samp{~} and @samp{!~} operators may be
either a regexp constant (@code{/}@dots{}@code{/}) or an ordinary
expression. In the latter case, the value of the expression as a string is used as a
dynamic regexp (@pxref{Regexp Usage}; also
@pxref{Computed Regexps}).
@cindex @command{awk} @subentry regexp constants and
@cindex regexp constants
A constant regular
expression in slashes by itself is also an expression.
@code{/@var{regexp}/} is an abbreviation for the following comparison expression:
@example
$0 ~ /@var{regexp}/
@end example
One special place where @code{/foo/} is @emph{not} an abbreviation for
@samp{$0 ~ /foo/} is when it is the righthand operand of @samp{~} or
@samp{!~}.
@xref{Using Constant Regexps},
where this is discussed in more detail.
@node POSIX String Comparison
@subsubsection String Comparison Based on Locale Collating Order
The POSIX standard used to say that all string comparisons are
performed based on the locale's @dfn{collating order}. This
is the order in which characters sort, as defined by the locale
(for more discussion, @pxref{Locales}). This order is usually very
different from the results obtained when doing straight byte-by-byte
comparison.@footnote{Technically, string comparison is supposed to behave
the same way as if the strings were compared with the C @code{strcoll()}
function.}
@cindex POSIX mode
Because this behavior differs considerably from existing practice,
@command{gawk} only implemented it when in POSIX mode (@pxref{Options}).
Here is an example to illustrate the difference, in an @code{en_US.UTF-8}
locale:
@example
$ @kbd{gawk 'BEGIN @{ printf("ABC < abc = %s\n",}
> @kbd{("ABC" < "abc" ? "TRUE" : "FALSE")) @}'}
@print{} ABC < abc = TRUE
$ @kbd{gawk --posix 'BEGIN @{ printf("ABC < abc = %s\n",}
> @kbd{("ABC" < "abc" ? "TRUE" : "FALSE")) @}'}
@print{} ABC < abc = FALSE
@end example
Fortunately, as of August 2016, comparison based on locale
collating order is no longer required for the @code{==} and @code{!=}
operators.@footnote{See @uref{http://austingroupbugs.net/view.php?id=1070,
the Austin Group website}.} However, comparison based on locales is still
required for @code{<}, @code{<=}, @code{>}, and @code{>=}. POSIX thus
recommends as follows:
@quotation
Since the @code{==} operator checks whether strings are identical,
not whether they collate equally, applications needing to check whether
strings collate equally can use:
@example
a <= b && a >= b
@end example
@end quotation
@cindex POSIX mode
As of @value{PVERSION} 4.2, @command{gawk} continues to use locale
collating order for @code{<}, @code{<=}, @code{>}, and @code{>=} only
in POSIX mode.
@ignore
References: http://austingroupbugs.net/view.php?id=963
and http://austingroupbugs.net/view.php?id=1070.
@end ignore
@node Boolean Ops
@subsection Boolean Expressions
@cindex and Boolean-logic operator
@cindex or Boolean-logic operator
@cindex not Boolean-logic operator
@cindex expressions @subentry Boolean
@cindex Boolean expressions
@cindex operators, Boolean @seeentry{Boolean expressions}
@cindex Boolean operators @seeentry{Boolean expressions}
@cindex logical operators @seeentry{Boolean expressions}
@cindex operators, logical @seeentry{Boolean expressions}
A @dfn{Boolean expression} is a combination of comparison expressions or
matching expressions, using the Boolean operators ``or''
(@samp{||}), ``and'' (@samp{&&}), and ``not'' (@samp{!}), along with
parentheses to control nesting. The truth value of the Boolean expression is
computed by combining the truth values of the component expressions.
Boolean expressions are also referred to as @dfn{logical expressions}.
The terms are equivalent.
Boolean expressions can be used wherever comparison and matching
expressions can be used. They can be used in @code{if}, @code{while},
@code{do}, and @code{for} statements
(@pxref{Statements}).
They have numeric values (one if true, zero if false) that come into play
if the result of the Boolean expression is stored in a variable or
used in arithmetic.
In addition, every Boolean expression is also a valid pattern, so
you can use one as a pattern to control the execution of rules.
The Boolean operators are:
@table @code
@item @var{boolean1} && @var{boolean2}
True if both @var{boolean1} and @var{boolean2} are true. For example,
the following statement prints the current input record if it contains
both @samp{edu} and @samp{li}:
@example
if ($0 ~ /edu/ && $0 ~ /li/) print
@end example
@cindex side effects @subentry Boolean operators
The subexpression @var{boolean2} is evaluated only if @var{boolean1}
is true. This can make a difference when @var{boolean2} contains
expressions that have side effects. In the case of @samp{$0 ~ /foo/ &&
($2 == bar++)}, the variable @code{bar} is not incremented if there is
no substring @samp{foo} in the record.
@item @var{boolean1} || @var{boolean2}
True if at least one of @var{boolean1} or @var{boolean2} is true.
For example, the following statement prints all records in the input
that contain @emph{either} @samp{edu} or
@samp{li}:
@example
if ($0 ~ /edu/ || $0 ~ /li/) print
@end example
The subexpression @var{boolean2} is evaluated only if @var{boolean1}
is false. This can make a difference when @var{boolean2} contains
expressions that have side effects.
(Thus, this test never really distinguishes records that contain both
@samp{edu} and @samp{li}---as soon as @samp{edu} is matched,
the full test succeeds.)
@item ! @var{boolean}
True if @var{boolean} is false. For example,
the following program prints @samp{no home!} in
the unusual event that the @env{HOME} environment
variable is not defined:
@example
BEGIN @{ if (! ("HOME" in ENVIRON))
print "no home!" @}
@end example
(The @code{in} operator is described in
@ref{Reference to Elements}.)
@end table
@cindex short-circuit operators
@cindex operators @subentry short-circuit
@cindex @code{&} (ampersand) @subentry @code{&&} operator
@cindex ampersand (@code{&}) @subentry @code{&&} operator
@cindex @code{|} (vertical bar) @subentry @code{||} operator
@cindex vertical bar (@code{|}) @subentry @code{||} operator
The @samp{&&} and @samp{||} operators are called @dfn{short-circuit}
operators because of the way they work. Evaluation of the full expression
is ``short-circuited'' if the result can be determined partway through
its evaluation.
@cindex line continuations
Statements that end with @samp{&&} or @samp{||} can be continued simply
by putting a newline after them. But you cannot put a newline in front
of either of these operators without using backslash continuation
(@pxref{Statements/Lines}).
@cindex @code{!} (exclamation point) @subentry @code{!} operator
@cindex exclamation point (@code{!}) @subentry @code{!} operator
@cindex newlines
@cindex variables @subentry flag
@cindex flag variables
The actual value of an expression using the @samp{!} operator is
either one or zero, depending upon the truth value of the expression it
is applied to.
The @samp{!} operator is often useful for changing the sense of a flag
variable from false to true and back again. For example, the following
program is one way to print lines in between special bracketing lines:
@example
$1 == "START" @{ interested = ! interested; next @}
interested @{ print @}
$1 == "END" @{ interested = ! interested; next @}
@end example
@noindent
The variable @code{interested}, as with all @command{awk} variables, starts
out initialized to zero, which is also false. When a line is seen whose
first field is @samp{START}, the value of @code{interested} is toggled
to true, using @samp{!}. The next rule prints lines as long as
@code{interested} is true. When a line is seen whose first field is
@samp{END}, @code{interested} is toggled back to false.@footnote{This
program has a bug; it prints lines starting with @samp{END}. How
would you fix it?}
@ignore
Scott Deifik points out that this program isn't robust against
bogus input data, but the point is to illustrate the use of `!',
so we'll leave well enough alone.
@end ignore
Most commonly, the @samp{!} operator is used in the conditions of
@code{if} and @code{while} statements, where it often makes more
sense to phrase the logic in the negative:
@example
if (! @var{some condition} || @var{some other condition}) @{
@var{@dots{} do whatever processing @dots{}}
@}
@end example
@cindex @code{next} statement
@quotation NOTE
The @code{next} statement is discussed in
@ref{Next Statement}.
@code{next} tells @command{awk} to skip the rest of the rules, get the
next record, and start processing the rules over again at the top.
The reason it's there is to avoid printing the bracketing
@samp{START} and @samp{END} lines.
@end quotation
@node Conditional Exp
@subsection Conditional Expressions
@cindex conditional expressions
@cindex expressions @subentry conditional
@cindex expressions @subentry selecting
A @dfn{conditional expression} is a special kind of expression that has
three operands. It allows you to use one expression's value to select
one of two other expressions.
The conditional expression in @command{awk} is the same as in the C
language, as shown here:
@example
@var{selector} ? @var{if-true-exp} : @var{if-false-exp}
@end example
@noindent
There are three subexpressions. The first, @var{selector}, is always
computed first. If it is ``true'' (not zero or not null), then
@var{if-true-exp} is computed next, and its value becomes the value of
the whole expression. Otherwise, @var{if-false-exp} is computed next,
and its value becomes the value of the whole expression.
For example, the following expression produces the absolute value of @code{x}:
@example
x >= 0 ? x : -x
@end example
@cindex side effects @subentry conditional expressions
Each time the conditional expression is computed, only one of
@var{if-true-exp} and @var{if-false-exp} is used; the other is ignored.
This is important when the expressions have side effects. For example,
this conditional expression examines element @code{i} of either array
@code{a} or array @code{b}, and increments @code{i}:
@example
x == y ? a[i++] : b[i++]
@end example
@noindent
This is guaranteed to increment @code{i} exactly once, because each time
only one of the two increment expressions is executed
and the other is not.
@xref{Arrays},
for more information about arrays.
@cindex differences in @command{awk} and @command{gawk} @subentry line continuations
@cindex line continuations @subentry @command{gawk}
@cindex @command{gawk} @subentry line continuation in
As a minor @command{gawk} extension,
a statement that uses @samp{?:} can be continued simply
by putting a newline after either character.
However, putting a newline in front
of either character does not work without using backslash continuation
(@pxref{Statements/Lines}).
If @option{--posix} is specified
(@pxref{Options}), this extension is disabled.
@node Function Calls
@section Function Calls
@cindex function calls
A @dfn{function} is a name for a particular calculation.
This enables you to
ask for it by name at any point in the program. For
example, the function @code{sqrt()} computes the square root of a number.
@cindex functions @subentry built-in
A fixed set of functions are @dfn{built in}, which means they are
available in every @command{awk} program. The @code{sqrt()} function is one
of these. @xref{Built-in} for a list of built-in
functions and their descriptions. In addition, you can define
functions for use in your program.
@xref{User-defined}
for instructions on how to do this.
Finally, @command{gawk} lets you write functions in C or C++
that may be called from your program (@pxref{Dynamic Extensions}).
@cindex arguments @subentry in function calls
The way to use a function is with a @dfn{function call} expression,
which consists of the function name followed immediately by a list of
@dfn{arguments} in parentheses. The arguments are expressions that
provide the raw materials for the function's calculations.
When there is more than one argument, they are separated by commas. If
there are no arguments, just write @samp{()} after the function name.
The following examples show function calls with and without arguments:
@example
sqrt(x^2 + y^2) @ii{one argument}
atan2(y, x) @ii{two arguments}
rand() @ii{no arguments}
@end example
@cindex troubleshooting @subentry function call syntax
@quotation CAUTION
Do not put any space between the function name and the opening parenthesis!
A user-defined function name looks just like the name of a
variable---a space would make the expression look like concatenation of
a variable with an expression inside parentheses.
With built-in functions, space before the parenthesis is harmless, but
it is best not to get into the habit of using space to avoid mistakes
with user-defined functions.
@end quotation
Each function expects a particular number
of arguments. For example, the @code{sqrt()} function must be called with
a single argument, the number of which to take the square root:
@example
sqrt(@var{argument})
@end example
Some of the built-in functions have one or
more optional arguments.
If those arguments are not supplied, the functions
use a reasonable default value.
@xref{Built-in} for full details. If arguments
are omitted in calls to user-defined functions, then those arguments are
treated as local variables. Such local variables act like the
empty string if referenced where a string value is required,
and like zero if referenced where a numeric value is required
(@pxref{User-defined}).
As an advanced feature, @command{gawk} provides indirect function calls,
which is a way to choose the function to call at runtime, instead of
when you write the source code to your program. We defer discussion of
this feature until later; see @ref{Indirect Calls}.
@cindex side effects @subentry function calls
Like every other expression, the function call has a value, often
called the @dfn{return value}, which is computed by the function
based on the arguments you give it. In this example, the return value
of @samp{sqrt(@var{argument})} is the square root of @var{argument}.
The following program reads numbers, one number per line, and prints
the square root of each one:
@example
$ @kbd{awk '@{ print "The square root of", $1, "is", sqrt($1) @}'}
@kbd{1}
@print{} The square root of 1 is 1
@kbd{3}
@print{} The square root of 3 is 1.73205
@kbd{5}
@print{} The square root of 5 is 2.23607
@kbd{Ctrl-d}
@end example
A function can also have side effects, such as assigning
values to certain variables or doing I/O.
This program shows how the @code{match()} function
(@pxref{String Functions})
changes the variables @code{RSTART} and @code{RLENGTH}:
@example
@{
if (match($1, $2))
print RSTART, RLENGTH
else
print "no match"
@}
@end example
@noindent
Here is a sample run:
@example
$ @kbd{awk -f matchit.awk}
@kbd{aaccdd c+}
@print{} 3 2
@kbd{foo bar}
@print{} no match
@kbd{abcdefg e}
@print{} 5 1
@end example
@node Precedence
@section Operator Precedence (How Operators Nest)
@cindex precedence
@cindex operators @subentry precedence of
@dfn{Operator precedence} determines how operators are grouped when
different operators appear close by in one expression. For example,
@samp{*} has higher precedence than @samp{+}; thus, @samp{a + b * c}
means to multiply @code{b} and @code{c}, and then add @code{a} to the
product (i.e., @samp{a + (b * c)}).
The normal precedence of the operators can be overruled by using parentheses.
Think of the precedence rules as saying where the
parentheses are assumed to be. In
fact, it is wise to always use parentheses whenever there is an unusual
combination of operators, because other people who read the program may
not remember what the precedence is in this case.
Even experienced programmers occasionally forget the exact rules,
which leads to mistakes.
Explicit parentheses help prevent
any such mistakes.
When operators of equal precedence are used together, the leftmost
operator groups first, except for the assignment, conditional, and
exponentiation operators, which group in the opposite order.
Thus, @samp{a - b + c} groups as @samp{(a - b) + c} and
@samp{a = b = c} groups as @samp{a = (b = c)}.
Normally the precedence of prefix unary operators does not matter,
because there is only one way to interpret
them: innermost first. Thus, @samp{$++i} means @samp{$(++i)} and
@samp{++$x} means @samp{++($x)}. However, when another operator follows
the operand, then the precedence of the unary operators can matter.
@samp{$x^2} means @samp{($x)^2}, but @samp{-x^2} means
@samp{-(x^2)}, because @samp{-} has lower precedence than @samp{^},
whereas @samp{$} has higher precedence.
Also, operators cannot be combined in a way that violates the
precedence rules; for example, @samp{$$0++--} is not a valid
expression because the first @samp{$} has higher precedence than the
@samp{++}; to avoid the problem the expression can be rewritten as
@samp{$($0++)--}.
This list presents @command{awk}'s operators, in order of highest
to lowest precedence:
@c @asis for docbook to come out right
@table @asis
@item @code{(}@dots{}@code{)}
Grouping.
@cindex @code{$} (dollar sign) @subentry @code{$} field operator
@cindex dollar sign (@code{$}) @subentry @code{$} field operator
@item @code{$}
Field reference.
@cindex @code{+} (plus sign) @subentry @code{++} operator
@cindex plus sign (@code{+}) @subentry @code{++} operator
@cindex @code{-} (hyphen) @subentry @code{--} operator
@cindex hyphen (@code{-}) @subentry @code{--} operator
@item @code{++ --}
Increment, decrement.
@cindex @code{^} (caret) @subentry @code{^} operator
@cindex caret (@code{^}) @subentry @code{^} operator
@cindex @code{*} (asterisk) @subentry @code{**} operator
@cindex asterisk (@code{*}) @subentry @code{**} operator
@item @code{^ **}
Exponentiation. These operators group right to left.
@cindex @code{+} (plus sign) @subentry @code{+} operator
@cindex plus sign (@code{+}) @subentry @code{+} operator
@cindex @code{-} (hyphen) @subentry @code{-} operator
@cindex hyphen (@code{-}) @subentry @code{-} operator
@cindex @code{!} (exclamation point) @subentry @code{!} operator
@cindex exclamation point (@code{!}) @subentry @code{!} operator
@item @code{+ - !}
Unary plus, minus, logical ``not.''
@cindex @code{*} (asterisk) @subentry @code{*} operator @subentry as multiplication operator
@cindex asterisk (@code{*}) @subentry @code{*} operator @subentry as multiplication operator
@cindex @code{/} (forward slash) @subentry @code{/} operator
@cindex forward slash (@code{/}) @subentry @code{/} operator
@cindex @code{%} (percent sign) @subentry @code{%} operator
@cindex percent sign (@code{%}) @subentry @code{%} operator
@item @code{* / %}
Multiplication, division, remainder.
@cindex @code{+} (plus sign) @subentry @code{+} operator
@cindex plus sign (@code{+}) @subentry @code{+} operator
@cindex @code{-} (hyphen) @subentry @code{-} operator
@cindex hyphen (@code{-}) @subentry @code{-} operator
@item @code{+ -}
Addition, subtraction.
@item String concatenation
There is no special symbol for concatenation.
The operands are simply written side by side
(@pxref{Concatenation}).
@cindex @code{<} (left angle bracket) @subentry @code{<} operator
@cindex left angle bracket (@code{<}) @subentry @code{<} operator
@cindex @code{<} (left angle bracket) @subentry @code{<=} operator
@cindex left angle bracket (@code{<}) @subentry @code{<=} operator
@cindex @code{>} (right angle bracket) @subentry @code{>=} operator
@cindex right angle bracket (@code{>}) @subentry @code{>=} operator
@cindex @code{>} (right angle bracket) @subentry @code{>} operator
@cindex right angle bracket (@code{>}) @subentry @code{>} operator
@cindex @code{=} (equals sign) @subentry @code{==} operator
@cindex equals sign (@code{=}) @subentry @code{==} operator
@cindex @code{!} (exclamation point) @subentry @code{!=} operator
@cindex exclamation point (@code{!}) @subentry @code{!=} operator
@cindex @code{>} (right angle bracket) @subentry @code{>>} operator (I/O)
@cindex right angle bracket (@code{>}) @subentry @code{>>} operator (I/O)
@cindex operators @subentry input/output
@cindex @code{|} (vertical bar) @subentry @code{|} operator (I/O)
@cindex vertical bar (@code{|}) @subentry @code{|} operator (I/O)
@cindex operators @subentry input/output
@cindex @code{|} (vertical bar) @subentry @code{|&} operator (I/O)
@cindex vertical bar (@code{|}) @subentry @code{|&} operator (I/O)
@cindex operators @subentry input/output
@item @code{< <= == != > >= >> | |&}
Relational and redirection.
The relational operators and the redirections have the same precedence
level. Characters such as @samp{>} serve both as relationals and as
redirections; the context distinguishes between the two meanings.
@cindex @code{print} statement @subentry I/O operators in
@cindex @code{printf} statement @subentry I/O operators in
Note that the I/O redirection operators in @code{print} and @code{printf}
statements belong to the statement level, not to expressions. The
redirection does not produce an expression that could be the operand of
another operator. As a result, it does not make sense to use a
redirection operator near another operator of lower precedence without
parentheses. Such combinations (e.g., @samp{print foo > a ? b : c})
result in syntax errors.
The correct way to write this statement is @samp{print foo > (a ? b : c)}.
@cindex @code{~} (tilde), @code{~} operator
@cindex tilde (@code{~}), @code{~} operator
@cindex @code{!} (exclamation point) @subentry @code{!~} operator
@cindex exclamation point (@code{!}) @subentry @code{!~} operator
@item @code{~ !~}
Matching, nonmatching.
@cindex @code{in} operator
@item @code{in}
Array membership.
@cindex @code{&} (ampersand) @subentry @code{&&} operator
@cindex ampersand (@code{&}) @subentry @code{&&} operator
@item @code{&&}
Logical ``and.''
@cindex @code{|} (vertical bar) @subentry @code{||} operator
@cindex vertical bar (@code{|}) @subentry @code{||} operator
@item @code{||}
Logical ``or.''
@cindex @code{?} (question mark) @subentry @code{?:} operator
@cindex question mark (@code{?}) @subentry @code{?:} operator
@cindex @code{:} (colon) @subentry @code{?:} operator
@cindex colon (@code{:}) @subentry @code{?:} operator
@item @code{?:}
Conditional. This operator groups right to left.
@cindex @code{+} (plus sign) @subentry @code{+=} operator
@cindex plus sign (@code{+}) @subentry @code{+=} operator
@cindex @code{-} (hyphen) @subentry @code{-=} operator
@cindex hyphen (@code{-}) @subentry @code{-=} operator
@cindex @code{*} (asterisk) @subentry @code{*=} operator
@cindex asterisk (@code{*}) @subentry @code{*=} operator
@cindex @code{*} (asterisk) @subentry @code{**=} operator
@cindex asterisk (@code{*}) @subentry @code{**=} operator
@cindex @code{/} (forward slash) @subentry @code{/=} operator
@cindex forward slash (@code{/}) @subentry @code{/=} operator
@cindex @code{%} (percent sign) @subentry @code{%=} operator
@cindex percent sign (@code{%}) @subentry @code{%=} operator
@cindex @code{^} (caret) @subentry @code{^=} operator
@cindex caret (@code{^}) @subentry @code{^=} operator
@item @code{= += -= *= /= %= ^= **=}
Assignment. These operators group right to left.
@end table
@cindex POSIX @command{awk} @subentry @code{**} operator and
@cindex portability @subentry operators @subentry not in POSIX @command{awk}
@quotation NOTE
The @samp{|&}, @samp{**}, and @samp{**=} operators are not specified by POSIX.
For maximum portability, do not use them.
@end quotation
@node Locales
@section Where You Are Makes a Difference
@cindex locale, definition of
Modern systems support the notion of @dfn{locales}: a way to tell the
system about the local character set and language. The ISO C standard
defines a default @code{"C"} locale, which is an environment that is
typical of what many C programmers are used to.
Once upon a time, the locale setting used to affect regexp matching,
but this is no longer true (@pxref{Ranges and Locales}).
Locales can affect record splitting. For the normal case of @samp{RS =
"\n"}, the locale is largely irrelevant. For other single-character
record separators, setting @samp{LC_ALL=C} in the environment will
give you much better performance when reading records. Otherwise,
@command{gawk} has to make several function calls, @emph{per input
character}, to find the record terminator.
Locales can affect how dates and times are formatted (@pxref{Time
Functions}). For example, a common way to abbreviate the date September
4, 2015, in the United States is ``9/4/15.'' In many countries in
Europe, however, it is abbreviated ``4.9.15.'' Thus, the @samp{%x}
specification in a @code{"US"} locale might produce @samp{9/4/15},
while in a @code{"EUROPE"} locale, it might produce @samp{4.9.15}.
According to POSIX, string comparison is also affected by locales (similar
to regular expressions). The details are presented in @ref{POSIX String
Comparison}.
Finally, the locale affects the value of the decimal point character
used when @command{gawk} parses input data. This is discussed in detail
in @ref{Conversion}.
@node Expressions Summary
@section Summary
@itemize @value{BULLET}
@item
Expressions are the basic elements of computation in programs. They are
built from constants, variables, function calls, and combinations of the
various kinds of values with operators.
@item
@command{awk} supplies three kinds of constants: numeric, string, and
regexp. @command{gawk} lets you specify numeric constants in octal
and hexadecimal (bases 8 and 16) as well as decimal (base 10).
In certain contexts, a standalone regexp constant such as @code{/foo/}
has the same meaning as @samp{$0 ~ /foo/}.
@item
Variables hold values between uses in computations. A number of built-in
variables provide information to your @command{awk} program, and a number
of others let you control how @command{awk} behaves.
@item
Numbers are automatically converted to strings, and strings to numbers,
as needed by @command{awk}. Numeric values are converted as if they were
formatted with @code{sprintf()} using the format in @code{CONVFMT}.
Locales can influence the conversions.
@item
@command{awk} provides the usual arithmetic operators (addition,
subtraction, multiplication, division, modulus), and unary plus and minus.
It also provides comparison operators, Boolean operators, an array membership
testing operator, and regexp
matching operators. String concatenation is accomplished by placing
two expressions next to each other; there is no explicit operator.
The three-operand @samp{?:} operator provides an ``if-else'' test within
expressions.
@item
Assignment operators provide convenient shorthands for common arithmetic
operations.
@item
In @command{awk}, a value is considered to be true if it is nonzero
@emph{or} non-null. Otherwise, the value is false.
@item
A variable's type is set upon each assignment and may change over its
lifetime. The type determines how it behaves in comparisons (string
or numeric).
@item
Function calls return a value that may be used as part of a larger
expression. Expressions used to pass parameter values are fully
evaluated before the function is called. @command{awk} provides
built-in and user-defined functions; this is described in
@ref{Functions}.
@item
Operator precedence specifies the order in which operations are performed,
unless explicitly overridden by parentheses. @command{awk}'s operator
precedence is compatible with that of C.
@item
Locales can affect the format of data as output by an @command{awk}
program, and occasionally the format for data read as input.
@end itemize
@node Patterns and Actions
@chapter Patterns, Actions, and Variables
@cindex patterns
As you have already seen, each @command{awk} statement consists of
a pattern with an associated action. This @value{CHAPTER} describes how
you build patterns and actions, what kinds of things you can do within
actions, and @command{awk}'s predefined variables.
The pattern--action rules and the statements available for use
within actions form the core of @command{awk} programming.
In a sense, everything covered
up to here has been the foundation
that programs are built on top of. Now it's time to start
building something useful.
@menu
* Pattern Overview:: What goes into a pattern.
* Using Shell Variables:: How to use shell variables with @command{awk}.
* Action Overview:: What goes into an action.
* Statements:: Describes the various control statements in
detail.
* Built-in Variables:: Summarizes the predefined variables.
* Pattern Action Summary:: Patterns and Actions summary.
@end menu
@node Pattern Overview
@section Pattern Elements
@menu
* Regexp Patterns:: Using regexps as patterns.
* Expression Patterns:: Any expression can be used as a pattern.
* Ranges:: Pairs of patterns specify record ranges.
* BEGIN/END:: Specifying initialization and cleanup rules.
* BEGINFILE/ENDFILE:: Two special patterns for advanced control.
* Empty:: The empty pattern, which matches every record.
@end menu
@cindex patterns @subentry types of
Patterns in @command{awk} control the execution of rules---a rule is
executed when its pattern matches the current input record.
The following is a summary of the types of @command{awk} patterns:
@table @code
@item /@var{regular expression}/
A regular expression. It matches when the text of the
input record fits the regular expression.
(@xref{Regexp}.)
@item @var{expression}
A single expression. It matches when its value
is nonzero (if a number) or non-null (if a string).
(@xref{Expression Patterns}.)
@item @var{begpat}, @var{endpat}
A pair of patterns separated by a comma, specifying a @dfn{range} of records.
The range includes both the initial record that matches @var{begpat} and
the final record that matches @var{endpat}.
(@xref{Ranges}.)
@item BEGIN
@itemx END
Special patterns for you to supply startup or cleanup actions for your
@command{awk} program.
(@xref{BEGIN/END}.)
@item BEGINFILE
@itemx ENDFILE
Special patterns for you to supply startup or cleanup actions to be
done on a per-file basis.
(@xref{BEGINFILE/ENDFILE}.)
@item @var{empty}
The empty pattern matches every input record.
(@xref{Empty}.)
@end table
@node Regexp Patterns
@subsection Regular Expressions as Patterns
@cindex patterns @subentry regexp constants as
@cindex regular expressions @subentry as patterns
Regular expressions are one of the first kinds of patterns presented
in this book.
This kind of pattern is simply a regexp constant in the pattern part of
a rule. Its meaning is @samp{$0 ~ /@var{pattern}/}.
The pattern matches when the input record matches the regexp.
For example:
@example
/foo|bar|baz/ @{ buzzwords++ @}
END @{ print buzzwords, "buzzwords seen" @}
@end example
@node Expression Patterns
@subsection Expressions as Patterns
@cindex expressions @subentry as patterns
@cindex patterns @subentry expressions as
Any @command{awk} expression is valid as an @command{awk} pattern.
The pattern matches if the expression's value is nonzero (if a
number) or non-null (if a string).
The expression is reevaluated each time the rule is tested against a new
input record. If the expression uses fields such as @code{$1}, the
value depends directly on the new input record's text; otherwise, it
depends on only what has happened so far in the execution of the
@command{awk} program.
@cindex comparison expressions @subentry as patterns
@cindex patterns @subentry comparison expressions as
Comparison expressions, using the comparison operators described in
@ref{Typing and Comparison},
are a very common kind of pattern.
Regexp matching and nonmatching are also very common expressions.
The left operand of the @samp{~} and @samp{!~} operators is a string.
The right operand is either a constant regular expression enclosed in
slashes (@code{/@var{regexp}/}), or any expression whose string value
is used as a dynamic regular expression
(@pxref{Computed Regexps}).
The following example prints the second field of each input record
whose first field is precisely @samp{li}:
@cindex @code{/} (forward slash) @subentry patterns and
@cindex forward slash (@code{/}) @subentry patterns and
@cindex @code{~} (tilde), @code{~} operator
@cindex tilde (@code{~}), @code{~} operator
@cindex @code{!} (exclamation point) @subentry @code{!~} operator
@cindex exclamation point (@code{!}) @subentry @code{!~} operator
@example
$ @kbd{awk '$1 == "li" @{ print $2 @}' mail-list}
@end example
@noindent
(There is no output, because there is no person with the exact name @samp{li}.)
Contrast this with the following regular expression match, which
accepts any record with a first field that contains @samp{li}:
@example
$ @kbd{awk '$1 ~ /li/ @{ print $2 @}' mail-list}
@print{} 555-5553
@print{} 555-6699
@end example
@cindex regexp constants @subentry as patterns
@cindex patterns @subentry regexp constants as
A regexp constant as a pattern is also a special case of an expression
pattern. The expression @code{/li/} has the value one if @samp{li}
appears in the current input record. Thus, as a pattern, @code{/li/}
matches any record containing @samp{li}.
@cindex Boolean expressions @subentry as patterns
@cindex patterns @subentry Boolean expressions as
Boolean expressions are also commonly used as patterns.
Whether the pattern
matches an input record depends on whether its subexpressions match.
For example, the following command prints all the records in
@file{mail-list} that contain both @samp{edu} and @samp{li}:
@example
$ @kbd{awk '/edu/ && /li/' mail-list}
@print{} Samuel 555-3430 samuel.lanceolis@@shu.edu A
@end example
The following command prints all records in
@file{mail-list} that contain @emph{either} @samp{edu} or @samp{li}
(or both, of course):
@example
$ @kbd{awk '/edu/ || /li/' mail-list}
@print{} Amelia 555-5553 amelia.zodiacusque@@gmail.com F
@print{} Broderick 555-0542 broderick.aliquotiens@@yahoo.com R
@print{} Fabius 555-1234 fabius.undevicesimus@@ucb.edu F
@print{} Julie 555-6699 julie.perscrutabor@@skeeve.com F
@print{} Samuel 555-3430 samuel.lanceolis@@shu.edu A
@print{} Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R
@end example
The following command prints all records in
@file{mail-list} that do @emph{not} contain the string @samp{li}:
@example
$ @kbd{awk '! /li/' mail-list}
@print{} Anthony 555-3412 anthony.asserturo@@hotmail.com A
@print{} Becky 555-7685 becky.algebrarum@@gmail.com A
@print{} Bill 555-1675 bill.drowning@@hotmail.com A
@print{} Camilla 555-2912 camilla.infusarum@@skynet.be R
@print{} Fabius 555-1234 fabius.undevicesimus@@ucb.edu F
@group
@print{} Martin 555-6480 martin.codicibus@@hotmail.com A
@print{} Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R
@end group
@end example
@cindex @code{BEGIN} pattern @subentry Boolean patterns and
@cindex @code{END} pattern @subentry Boolean patterns and
@cindex @code{BEGINFILE} pattern @subentry Boolean patterns and
@cindex @code{ENDFILE} pattern @subentry Boolean patterns and
The subexpressions of a Boolean operator in a pattern can be constant regular
expressions, comparisons, or any other @command{awk} expressions. Range
patterns are not expressions, so they cannot appear inside Boolean
patterns. Likewise, the special patterns @code{BEGIN}, @code{END},
@code{BEGINFILE}, and @code{ENDFILE},
which never match any input record, are not expressions and cannot
appear inside Boolean patterns.
The precedence of the different operators that can appear in
patterns is described in @ref{Precedence}.
@node Ranges
@subsection Specifying Record Ranges with Patterns
@cindex range patterns
@cindex patterns @subentry ranges in
@cindex lines @subentry matching ranges of
@cindex @code{,} (comma), in range patterns
@cindex comma (@code{,}), in range patterns
A @dfn{range pattern} is made of two patterns separated by a comma, in
the form @samp{@var{begpat}, @var{endpat}}. It is used to match ranges of
consecutive input records. The first pattern, @var{begpat}, controls
where the range begins, while @var{endpat} controls where
the pattern ends. For example, the following:
@example
awk '$1 == "on", $1 == "off"' myfile
@end example
@noindent
prints every record in @file{myfile} between @samp{on}/@samp{off} pairs, inclusive.
A range pattern starts out by matching @var{begpat} against every
input record. When a record matches @var{begpat}, the range pattern is
@dfn{turned on}, and the range pattern matches this record as well. As long as
the range pattern stays turned on, it automatically matches every input
record read. The range pattern also matches @var{endpat} against every
input record; when this succeeds, the range pattern is @dfn{turned off} again
for the following record. Then the range pattern goes back to checking
@var{begpat} against each record.
@cindex @code{if} statement @subentry actions, changing
The record that turns on the range pattern and the one that turns it
off both match the range pattern. If you don't want to operate on
these records, you can write @code{if} statements in the rule's action
to distinguish them from the records you are interested in.
It is possible for a pattern to be turned on and off by the same
record. If the record satisfies both conditions, then the action is
executed for just that record.
For example, suppose there is text between two identical markers (e.g.,
the @samp{%} symbol), each on its own line, that should be ignored.
A first attempt would be to
combine a range pattern that describes the delimited text with the
@code{next} statement
(not discussed yet, @pxref{Next Statement}).
This causes @command{awk} to skip any further processing of the current
record and start over again with the next input record. Such a program
looks like this:
@example
/^%$/,/^%$/ @{ next @}
@{ print @}
@end example
@noindent
@cindex lines @subentry skipping between markers
@c @cindex flag variables
This program fails because the range pattern is both turned on and turned off
by the first line, which just has a @samp{%} on it. To accomplish this task,
write the program in the following manner, using a flag:
@cindex @code{!} (exclamation point) @subentry @code{!} operator
@example
/^%$/ @{ skip = ! skip; next @}
skip == 1 @{ next @} # skip lines with `skip' set
@end example
In a range pattern, the comma (@samp{,}) has the lowest precedence of
all the operators (i.e., it is evaluated last). Thus, the following
program attempts to combine a range pattern with another, simpler test:
@example
echo Yes | awk '/1/,/2/ || /Yes/'
@end example
The intent of this program is @samp{(/1/,/2/) || /Yes/}.
However, @command{awk} interprets this as @samp{/1/, (/2/ || /Yes/)}.
This cannot be changed or worked around; range patterns do not combine
with other patterns:
@example
$ @kbd{echo Yes | gawk '(/1/,/2/) || /Yes/'}
@error{} gawk: cmd. line:1: (/1/,/2/) || /Yes/
@error{} gawk: cmd. line:1: ^ syntax error
@end example
@cindex range patterns @subentry line continuation and
@cindex dark corner @subentry range patterns, line continuation and
As a minor point of interest, although it is poor style,
POSIX allows you to put a newline after the comma in
a range pattern. @value{DARKCORNER}
@node BEGIN/END
@subsection The @code{BEGIN} and @code{END} Special Patterns
@cindex @code{BEGIN} pattern
@cindex @code{END} pattern
All the patterns described so far are for matching input records.
The @code{BEGIN} and @code{END} special patterns are different.
They supply startup and cleanup actions for @command{awk} programs.
@code{BEGIN} and @code{END} rules must have actions; there is no default
action for these rules because there is no current record when they run.
@code{BEGIN} and @code{END} rules are often referred to as
``@code{BEGIN} and @code{END} blocks'' by longtime @command{awk}
programmers.
@menu
* Using BEGIN/END:: How and why to use BEGIN/END rules.
* I/O And BEGIN/END:: I/O issues in BEGIN/END rules.
@end menu
@node Using BEGIN/END
@subsubsection Startup and Cleanup Actions
@cindex @code{BEGIN} pattern
@cindex @code{END} pattern
A @code{BEGIN} rule is executed once only, before the first input record
is read. Likewise, an @code{END} rule is executed once only, after all the
input is read. For example:
@example
$ @kbd{awk '}
> @kbd{BEGIN @{ print "Analysis of \"li\"" @}}
> @kbd{/li/ @{ ++n @}}
> @kbd{END @{ print "\"li\" appears in", n, "records." @}' mail-list}
@print{} Analysis of "li"
@print{} "li" appears in 4 records.
@end example
@cindex @code{BEGIN} pattern @subentry operators and
@cindex @code{END} pattern @subentry operators and
This program finds the number of records in the input file @file{mail-list}
that contain the string @samp{li}. The @code{BEGIN} rule prints a title
for the report. There is no need to use the @code{BEGIN} rule to
initialize the counter @code{n} to zero, as @command{awk} does this
automatically (@pxref{Variables}).
The second rule increments the variable @code{n} every time a
record containing the pattern @samp{li} is read. The @code{END} rule
prints the value of @code{n} at the end of the run.
The special patterns @code{BEGIN} and @code{END} cannot be used in ranges
or with Boolean operators (indeed, they cannot be used with any operators).
An @command{awk} program may have multiple @code{BEGIN} and/or @code{END}
rules. They are executed in the order in which they appear: all the @code{BEGIN}
rules at startup and all the @code{END} rules at termination.
@code{BEGIN} and @code{END} rules may be intermixed with other rules.
This feature was added in the 1987 version of @command{awk} and is included
in the POSIX standard.
The original (1978) version of @command{awk}
required the @code{BEGIN} rule to be placed at the beginning of the
program, the @code{END} rule to be placed at the end, and only allowed one of
each.
This is no longer required, but it is a good idea to follow this template
in terms of program organization and readability.
Multiple @code{BEGIN} and @code{END} rules are useful for writing
library functions, because each library file can have its own @code{BEGIN} and/or
@code{END} rule to do its own initialization and/or cleanup.
The order in which library functions are named on the command line
controls the order in which their @code{BEGIN} and @code{END} rules are
executed. Therefore, you have to be careful when writing such rules in
library files so that the order in which they are executed doesn't matter.
@xref{Options} for more information on
using library functions.
@xref{Library Functions},
for a number of useful library functions.
If an @command{awk} program has only @code{BEGIN} rules and no
other rules, then the program exits after the @code{BEGIN} rules are
run.@footnote{The original version of @command{awk} kept
reading and ignoring input until the end of the file was seen.} However, if an
@code{END} rule exists, then the input is read, even if there are
no other rules in the program. This is necessary in case the @code{END}
rule checks the @code{FNR} and @code{NR} variables.
@node I/O And BEGIN/END
@subsubsection Input/Output from @code{BEGIN} and @code{END} Rules
@cindex input/output @subentry from @code{BEGIN} and @code{END}
There are several (sometimes subtle) points to be aware of when doing I/O
from a @code{BEGIN} or @code{END} rule.
The first has to do with the value of @code{$0} in a @code{BEGIN}
rule. Because @code{BEGIN} rules are executed before any input is read,
there simply is no input record, and therefore no fields, when
executing @code{BEGIN} rules. References to @code{$0} and the fields
yield a null string or zero, depending upon the context. One way
to give @code{$0} a real value is to execute a @code{getline} command
without a variable (@pxref{Getline}).
Another way is simply to assign a value to @code{$0}.
@cindex Brian Kernighan's @command{awk}
@cindex differences in @command{awk} and @command{gawk} @subentry @code{BEGIN}/@code{END} patterns
@cindex POSIX @command{awk} @subentry @code{BEGIN}/@code{END} patterns
@cindex @code{print} statement @subentry @code{BEGIN}/@code{END} patterns and
@cindex @code{BEGIN} pattern @subentry @code{print} statement and
@cindex @code{END} pattern @subentry @code{print} statement and
The second point is similar to the first, but from the other direction.
Traditionally, due largely to implementation issues, @code{$0} and
@code{NF} were @emph{undefined} inside an @code{END} rule.
The POSIX standard specifies that @code{NF} is available in an @code{END}
rule. It contains the number of fields from the last input record.
Most probably due to an oversight, the standard does not say that @code{$0}
is also preserved, although logically one would think that it should be.
In fact, all of BWK @command{awk}, @command{mawk}, and @command{gawk}
preserve the value of @code{$0} for use in @code{END} rules. Be aware,
however, that some other implementations and many older versions
of Unix @command{awk} do not.
The third point follows from the first two. The meaning of @samp{print}
inside a @code{BEGIN} or @code{END} rule is the same as always:
@samp{print $0}. If @code{$0} is the null string, then this prints an
empty record. Many longtime @command{awk} programmers use an unadorned
@samp{print} in @code{BEGIN} and @code{END} rules, to mean @samp{@w{print ""}},
relying on @code{$0} being null. Although one might generally get away with
this in @code{BEGIN} rules, it is a very bad idea in @code{END} rules,
at least in @command{gawk}. It is also poor style, because if an empty
line is needed in the output, the program should print one explicitly.
@cindex @code{next} statement @subentry @code{BEGIN}/@code{END} patterns and
@cindex @code{nextfile} statement @subentry @code{BEGIN}/@code{END} patterns and
@cindex @code{BEGIN} pattern @subentry @code{next}/@code{nextfile} statements and
@cindex @code{END} pattern @subentry @code{next}/@code{nextfile} statements and
Finally, the @code{next} and @code{nextfile} statements are not allowed
in a @code{BEGIN} rule, because the implicit
read-a-record-and-match-against-the-rules loop has not started yet. Similarly, those statements
are not valid in an @code{END} rule, because all the input has been read.
(@xref{Next Statement} and
@ifnotdocbook
@pxref{Nextfile Statement}.)
@end ifnotdocbook
@ifdocbook
@ref{Nextfile Statement}.)
@end ifdocbook
@node BEGINFILE/ENDFILE
@subsection The @code{BEGINFILE} and @code{ENDFILE} Special Patterns
@cindex @code{BEGINFILE} pattern
@cindex @code{ENDFILE} pattern
@cindex differences in @command{awk} and @command{gawk} @subentry @code{BEGINFILE}/@code{ENDFILE} patterns
This @value{SECTION} describes a @command{gawk}-specific feature.
Two special kinds of rule, @code{BEGINFILE} and @code{ENDFILE}, give
you ``hooks'' into @command{gawk}'s command-line file processing loop.
As with the @code{BEGIN} and @code{END} rules
@ifnottex
@ifnotdocbook
(@pxref{BEGIN/END}),
@end ifnotdocbook
@end ifnottex
@iftex
(see the previous @value{SECTION}),
@end iftex
@ifdocbook
(see the previous @value{SECTION}),
@end ifdocbook
all @code{BEGINFILE} rules in a program are merged, in the order they are
read by @command{gawk}, and all @code{ENDFILE} rules are merged as well.
The body of the @code{BEGINFILE} rules is executed just before
@command{gawk} reads the first record from a file. @code{FILENAME}
is set to the name of the current file, and @code{FNR} is set to zero.
The @code{BEGINFILE} rule provides you the opportunity to accomplish two tasks
that would otherwise be difficult or impossible to perform:
@itemize @value{BULLET}
@item
You can test if the file is readable. Normally, it is a fatal error if a
file named on the command line cannot be opened for reading. However,
you can bypass the fatal error and move on to the next file on the
command line.
@cindex @command{gawk} @subentry @code{ERRNO} variable in
@cindex @code{ERRNO} variable @subentry with @code{BEGINFILE} pattern
@cindex @code{nextfile} statement @subentry @code{BEGINFILE}/@code{ENDFILE} patterns and
You do this by checking if the @code{ERRNO} variable is not the empty
string; if so, then @command{gawk} was not able to open the file. In
this case, your program can execute the @code{nextfile} statement
(@pxref{Nextfile Statement}). This causes @command{gawk} to skip
the file entirely. Otherwise, @command{gawk} exits with the usual
fatal error.
@item
If you have written extensions that modify the record handling (by
inserting an ``input parser''; @pxref{Input Parsers}), you can invoke
them at this point, before @command{gawk} has started processing the file.
(This is a @emph{very} advanced feature, currently used only by the
@uref{https://sourceforge.net/projects/gawkextlib, @code{gawkextlib} project}.)
@end itemize
The @code{ENDFILE} rule is called when @command{gawk} has finished processing
the last record in an input file. For the last input file,
it will be called before any @code{END} rules.
The @code{ENDFILE} rule is executed even for empty input files.
Normally, when an error occurs when reading input in the normal
input-processing loop, the error is fatal. However, if an @code{ENDFILE}
rule is present, the error becomes non-fatal, and instead @code{ERRNO}
is set. This makes it possible to catch and process I/O errors at the
level of the @command{awk} program.
@cindex @code{next} statement @subentry @code{BEGINFILE}/@code{ENDFILE} patterns and
The @code{next} statement (@pxref{Next Statement}) is not allowed inside
either a @code{BEGINFILE} or an @code{ENDFILE} rule. The @code{nextfile}
statement is allowed only inside a
@code{BEGINFILE} rule, not inside an @code{ENDFILE} rule.
@cindex @code{getline} command @subentry @code{BEGINFILE}/@code{ENDFILE} patterns and
The @code{getline} statement (@pxref{Getline}) is restricted inside
both @code{BEGINFILE} and @code{ENDFILE}: only redirected
forms of @code{getline} are allowed.
@code{BEGINFILE} and @code{ENDFILE} are @command{gawk} extensions.
In most other @command{awk} implementations, or if @command{gawk} is in
compatibility mode (@pxref{Options}), they are not special.
@c FIXME: For 4.2 maybe deal with this?
@ignore
Date: Tue, 17 May 2011 02:06:10 PDT
From: rankin@pactechdata.com (Pat Rankin)
Message-Id: <110517015127.20240f4a@pactechdata.com>
Subject: BEGINFILE
To: arnold@skeeve.com
The documentation for BEGINFILE states that FNR is 0, which seems
pretty obvious. It doesn't mention what the value of $0 is, and that's
not obvious. I think setting it to null before starting the BEGINFILE
action would be preferable to leaving whatever was there in the last
record of the previous file.
ENDFILE can retain the last record in $0. I guess it has to if
the END rule's actions see that value too. But the beginning of a new
file doesn't just mean that the old one has been closed; the old file
is being superseded, so leaving the old data around feels wrong to me.
[If the user wants to keep it on hand, he or she can use an ENDFILE
rule to grab it before moving on to the next file.]
@end ignore
@node Empty
@subsection The Empty Pattern
@cindex empty pattern
@cindex patterns @subentry empty
An empty (i.e., nonexistent) pattern is considered to match @emph{every}
input record. For example, the program:
@example
awk '@{ print $1 @}' mail-list
@end example
@noindent
prints the first field of every record.
@node Using Shell Variables
@section Using Shell Variables in Programs
@cindex shells @subentry variables
@cindex @command{awk} programs @subentry shell variables in
@c @cindex shell and @command{awk} interaction
@command{awk} programs are often used as components in larger
programs written in shell.
For example, it is very common to use a shell variable to
hold a pattern that the @command{awk} program searches for.
There are two ways to get the value of the shell variable
into the body of the @command{awk} program.
@cindex shells @subentry quoting
A common method is to use shell quoting to substitute
the variable's value into the program inside the script.
For example, consider the following program:
@example
@group
printf "Enter search pattern: "
read pattern
awk "/$pattern/ "'@{ nmatches++ @}
END @{ print nmatches, "found" @}' /path/to/data
@end group
@end example
@noindent
The @command{awk} program consists of two pieces of quoted text
that are concatenated together to form the program.
The first part is double-quoted, which allows substitution of
the @code{pattern} shell variable inside the quotes.
The second part is single-quoted.
Variable substitution via quoting works, but can potentially be
messy. It requires a good understanding of the shell's quoting rules
(@pxref{Quoting}),
and it's often difficult to correctly
match up the quotes when reading the program.
A better method is to use @command{awk}'s variable assignment feature
(@pxref{Assignment Options})
to assign the shell variable's value to an @command{awk} variable.
Then use dynamic regexps to match the pattern
(@pxref{Computed Regexps}).
The following shows how to redo the
previous example using this technique:
@example
printf "Enter search pattern: "
read pattern
awk -v pat="$pattern" '$0 ~ pat @{ nmatches++ @}
END @{ print nmatches, "found" @}' /path/to/data
@end example
@noindent
Now, the @command{awk} program is just one single-quoted string.
The assignment @samp{-v pat="$pattern"} still requires double quotes,
in case there is whitespace in the value of @code{$pattern}.
The @command{awk} variable @code{pat} could be named @code{pattern}
too, but that would be more confusing. Using a variable also
provides more flexibility, as the variable can be used anywhere inside
the program---for printing, as an array subscript, or for any other
use---without requiring the quoting tricks at every point in the program.
@node Action Overview
@section Actions
@c @cindex action, definition of
@c @cindex curly braces
@c @cindex action, curly braces
@c @cindex action, separating statements
@cindex actions
An @command{awk} program or script consists of a series of
rules and function definitions interspersed. (Functions are
described later. @xref{User-defined}.)
A rule contains a pattern and an action, either of which (but not
both) may be omitted. The purpose of the @dfn{action} is to tell
@command{awk} what to do once a match for the pattern is found. Thus,
in outline, an @command{awk} program generally looks like this:
@display
[@var{pattern}] @code{@{ @var{action} @}}
@var{pattern} [@code{@{ @var{action} @}}]
@dots{}
@code{function @var{name}(@var{args}) @{ @dots{} @}}
@dots{}
@end display
@cindex @code{@{@}} (braces) @subentry actions and
@cindex braces (@code{@{@}}) @subentry actions and
@cindex separators @subentry for statements in actions
@cindex newlines @subentry separating statements in actions
@cindex @code{;} (semicolon) @subentry separating statements in actions
@cindex semicolon (@code{;}) @subentry separating statements in actions
An action consists of one or more @command{awk} @dfn{statements}, enclosed
in braces (@samp{@{@r{@dots{}}@}}). Each statement specifies one
thing to do. The statements are separated by newlines or semicolons.
The braces around an action must be used even if the action
contains only one statement, or if it contains no statements at
all. However, if you omit the action entirely, omit the braces as
well. An omitted action is equivalent to @samp{@{ print $0 @}}:
@example
/foo/ @{ @} @ii{match @code{foo}, do nothing --- empty action}
/foo/ @ii{match @code{foo}, print the record --- omitted action}
@end example
The following types of statements are supported in @command{awk}:
@table @asis
@cindex side effects @subentry statements
@item Expressions
Call functions or assign values to variables
(@pxref{Expressions}). Executing
this kind of statement simply computes the value of the expression.
This is useful when the expression has side effects
(@pxref{Assignment Ops}).
@item Control statements
Specify the control flow of @command{awk}
programs. The @command{awk} language gives you C-like constructs
(@code{if}, @code{for}, @code{while}, and @code{do}) as well as a few
special ones (@pxref{Statements}).
@item Compound statements
Enclose one or more statements in braces. A compound statement
is used in order to put several statements together in the body of an
@code{if}, @code{while}, @code{do}, or @code{for} statement.
@item Input statements
Use the @code{getline} command
(@pxref{Getline}).
Also supplied in @command{awk} are the @code{next}
statement (@pxref{Next Statement})
and the @code{nextfile} statement
(@pxref{Nextfile Statement}).
@item Output statements
Such as @code{print} and @code{printf}.
@xref{Printing}.
@item Deletion statements
For deleting array elements.
@xref{Delete}.
@end table
@node Statements
@section Control Statements in Actions
@cindex control statements
@cindex statements @subentry control, in actions
@cindex actions @subentry control statements in
@dfn{Control statements}, such as @code{if}, @code{while}, and so on,
control the flow of execution in @command{awk} programs. Most of @command{awk}'s
control statements are patterned after similar statements in C.
@cindex compound statements, control statements and
@cindex statements @subentry compound, control statements and
@cindex body @subentry in actions
@cindex @code{@{@}} (braces) @subentry statements, grouping
@cindex braces (@code{@{@}}) @subentry statements, grouping
@cindex newlines @subentry separating statements in actions
@cindex @code{;} (semicolon) @subentry separating statements in actions
@cindex semicolon (@code{;}) @subentry separating statements in actions
All the control statements start with special keywords, such as @code{if}
and @code{while}, to distinguish them from simple expressions.
Many control statements contain other statements. For example, the
@code{if} statement contains another statement that may or may not be
executed. The contained statement is called the @dfn{body}.
To include more than one statement in the body, group them into a
single @dfn{compound statement} with braces, separating them with
newlines or semicolons.
@menu
* If Statement:: Conditionally execute some @command{awk}
statements.
* While Statement:: Loop until some condition is satisfied.
* Do Statement:: Do specified action while looping until some
condition is satisfied.
* For Statement:: Another looping statement, that provides
initialization and increment clauses.
* Switch Statement:: Switch/case evaluation for conditional
execution of statements based on a value.
* Break Statement:: Immediately exit the innermost enclosing loop.
* Continue Statement:: Skip to the end of the innermost enclosing
loop.
* Next Statement:: Stop processing the current input record.
* Nextfile Statement:: Stop processing the current file.
* Exit Statement:: Stop execution of @command{awk}.
@end menu
@node If Statement
@subsection The @code{if}-@code{else} Statement
@cindex @code{if} statement
The @code{if}-@code{else} statement is @command{awk}'s decision-making
statement. It looks like this:
@display
@code{if (@var{condition}) @var{then-body}} [@code{else @var{else-body}}]
@end display
@noindent
The @var{condition} is an expression that controls what the rest of the
statement does. If the @var{condition} is true, @var{then-body} is
executed; otherwise, @var{else-body} is executed.
The @code{else} part of the statement is
optional. The condition is considered false if its value is zero or
the null string; otherwise, the condition is true.
Refer to the following:
@example
@group
if (x % 2 == 0)
print "x is even"
else
print "x is odd"
@end group
@end example
In this example, if the expression @samp{x % 2 == 0} is true (i.e.,
if the value of @code{x} is evenly divisible by two), then the first
@code{print} statement is executed; otherwise, the second @code{print}
statement is executed.
If the @code{else} keyword appears on the same line as @var{then-body} and
@var{then-body} is not a compound statement (i.e., not surrounded by
braces), then a semicolon must separate @var{then-body} from
the @code{else}.
To illustrate this, the previous example can be rewritten as:
@example
if (x % 2 == 0) print "x is even"; else
print "x is odd"
@end example
@noindent
If the @samp{;} is left out, @command{awk} can't interpret the statement and
it produces a syntax error. Don't actually write programs this way,
because a human reader might fail to see the @code{else} if it is not
the first thing on its line.
@node While Statement
@subsection The @code{while} Statement
@cindex @code{while} statement
@cindex loops
@cindex loops @subentry @code{while}
@cindex loops @seealso{@code{while} statement}
In programming, a @dfn{loop} is a part of a program that can
be executed two or more times in succession.
The @code{while} statement is the simplest looping statement in
@command{awk}. It repeatedly executes a statement as long as a condition is
true. For example:
@example
while (@var{condition})
@var{body}
@end example
@cindex body @subentry in loops
@noindent
@var{body} is a statement called the @dfn{body} of the loop,
and @var{condition} is an expression that controls how long the loop
keeps running.
The first thing the @code{while} statement does is test the @var{condition}.
If the @var{condition} is true, it executes the statement @var{body}.
@ifinfo
(The @var{condition} is true when the value
is not zero and not a null string.)
@end ifinfo
After @var{body} has been executed,
@var{condition} is tested again, and if it is still true, @var{body}
executes again. This process repeats until the @var{condition} is no longer
true. If the @var{condition} is initially false, the body of the loop
never executes and @command{awk} continues with the statement following
the loop.
This example prints the first three fields of each record, one per line:
@example
awk '
@{
i = 1
while (i <= 3) @{
print $i
i++
@}
@}' inventory-shipped
@end example
@noindent
The body of this loop is a compound statement enclosed in braces,
containing two statements.
The loop works in the following manner: first, the value of @code{i} is set to one.
Then, the @code{while} statement tests whether @code{i} is less than or equal to
three. This is true when @code{i} equals one, so the @code{i}th
field is printed. Then the @samp{i++} increments the value of @code{i}
and the loop repeats. The loop terminates when @code{i} reaches four.
A newline is not required between the condition and the
body; however, using one makes the program clearer unless the body is a
compound statement or else is very simple. The newline after the open brace
that begins the compound statement is not required either, but the
program is harder to read without it.
@node Do Statement
@subsection The @code{do}-@code{while} Statement
@cindex @code{do}-@code{while} statement
@cindex loops @subentry @code{do}-@code{while}
The @code{do} loop is a variation of the @code{while} looping statement.
The @code{do} loop executes the @var{body} once and then repeats the
@var{body} as long as the @var{condition} is true. It looks like this:
@example
do
@var{body}
while (@var{condition})
@end example
Even if the @var{condition} is false at the start, the @var{body}
executes at least once (and only once, unless executing @var{body}
makes @var{condition} true). Contrast this with the corresponding
@code{while} statement:
@example
while (@var{condition})
@var{body}
@end example
@noindent
This statement does not execute the @var{body} even once if the
@var{condition} is false to begin with. The following is an example of
a @code{do} statement:
@example
@{
i = 1
do @{
print $0
i++
@} while (i <= 10)
@}
@end example
@noindent
This program prints each input record 10 times. However, it isn't a very
realistic example, because in this case an ordinary @code{while} would do
just as well. This situation reflects actual experience; only
occasionally is there a real use for a @code{do} statement.
@node For Statement
@subsection The @code{for} Statement
@cindex @code{for} statement
@cindex loops @subentry @code{for} @subentry iterative
The @code{for} statement makes it more convenient to count iterations of a
loop. The general form of the @code{for} statement looks like this:
@example
for (@var{initialization}; @var{condition}; @var{increment})
@var{body}
@end example
@noindent
The @var{initialization}, @var{condition}, and @var{increment} parts are
arbitrary @command{awk} expressions, and @var{body} stands for any
@command{awk} statement.
The @code{for} statement starts by executing @var{initialization}.
Then, as long
as the @var{condition} is true, it repeatedly executes @var{body} and then
@var{increment}. Typically, @var{initialization} sets a variable to
either zero or one, @var{increment} adds one to it, and @var{condition}
compares it against the desired number of iterations.
For example:
@example
awk '
@{
for (i = 1; i <= 3; i++)
print $i
@}' inventory-shipped
@end example
@noindent
This prints the first three fields of each input record, with one
input field per output line.
It isn't possible to
set more than one variable in the
@var{initialization} part without using a multiple assignment statement
such as @samp{x = y = 0}. This makes sense only if all the initial values
are equal. (But it is possible to initialize additional variables by writing
their assignments as separate statements preceding the @code{for} loop.)
@c @cindex comma operator, not supported
The same is true of the @var{increment} part. Incrementing additional
variables requires separate statements at the end of the loop.
The C compound expression, using C's comma operator, is useful in
this context, but it is not supported in @command{awk}.
Most often, @var{increment} is an increment expression, as in the previous
example. But this is not required; it can be any expression
whatsoever. For example, the following statement prints all the powers of two
between 1 and 100:
@example
for (i = 1; i <= 100; i *= 2)
print i
@end example
If there is nothing to be done, any of the three expressions in the
parentheses following the @code{for} keyword may be omitted. Thus,
@w{@samp{for (; x > 0;)}} is equivalent to @w{@samp{while (x > 0)}}. If the
@var{condition} is omitted, it is treated as true, effectively
yielding an @dfn{infinite loop} (i.e., a loop that never terminates).
In most cases, a @code{for} loop is an abbreviation for a @code{while}
loop, as shown here:
@example
@var{initialization}
while (@var{condition}) @{
@var{body}
@var{increment}
@}
@end example
@cindex loops @subentry @code{continue} statement and
@noindent
The only exception is when the @code{continue} statement
(@pxref{Continue Statement}) is used
inside the loop. Changing a @code{for} statement to a @code{while}
statement in this way can change the effect of the @code{continue}
statement inside the loop.
The @command{awk} language has a @code{for} statement in addition to a
@code{while} statement because a @code{for} loop is often both less work to
type and more natural to think of. Counting the number of iterations is
very common in loops. It can be easier to think of this counting as part
of looping rather than as something to do inside the loop.
@cindex @code{in} operator
There is an alternative version of the @code{for} loop, for iterating over
all the indices of an array:
@example
for (i in array)
@var{do something with} array[i]
@end example
@noindent
@xref{Scanning an Array}
for more information on this version of the @code{for} loop.
@node Switch Statement
@subsection The @code{switch} Statement
@cindex @code{switch} statement
@cindex @code{case} keyword
@cindex @code{default} keyword
This @value{SECTION} describes a @command{gawk}-specific feature.
If @command{gawk} is in compatibility mode (@pxref{Options}),
it is not available.
The @code{switch} statement allows the evaluation of an expression and
the execution of statements based on a @code{case} match. Case statements
are checked for a match in the order they are defined. If no suitable
@code{case} is found, the @code{default} section is executed, if supplied.
Each @code{case} contains a single constant, be it numeric, string, or
regexp. The @code{switch} expression is evaluated, and then each
@code{case}'s constant is compared against the result in turn. The type of constant
determines the comparison: numeric or string do the usual comparisons.
A regexp constant does a regular expression match against the string
value of the original expression. The general form of the @code{switch}
statement looks like this:
@example
switch (@var{expression}) @{
case @var{value or regular expression}:
@var{case-body}
default:
@var{default-body}
@}
@end example
Control flow in
the @code{switch} statement works as it does in C. Once a match to a given
case is made, the case statement bodies execute until a @code{break},
@code{continue}, @code{next}, @code{nextfile}, or @code{exit} is encountered,
or the end of the @code{switch} statement itself. For example:
@example
while ((c = getopt(ARGC, ARGV, "aksx")) != -1) @{
switch (c) @{
case "a":
# report size of all files
all_files = TRUE;
break
case "k":
BLOCK_SIZE = 1024 # 1K block size
break
case "s":
# do sums only
sum_only = TRUE
break
case "x":
# don't cross filesystems
fts_flags = or(fts_flags, FTS_XDEV)
break
case "?":
default:
usage()
break
@}
@}
@end example
Note that if none of the statements specified here halt execution
of a matched @code{case} statement, execution falls through to the
next @code{case} until execution halts. In this example, the
@code{case} for @code{"?"} falls through to the @code{default}
case, which is to call a function named @code{usage()}.
(The @code{getopt()} function being called here is
described in @ref{Getopt Function}.)
@node Break Statement
@subsection The @code{break} Statement
@cindex @code{break} statement
@cindex loops @subentry exiting
@cindex loops @subentry @code{break} statement and
The @code{break} statement jumps out of the innermost @code{for},
@code{while}, or @code{do} loop that encloses it. The following example
finds the smallest divisor of any integer, and also identifies prime
numbers:
@example
@group
# find smallest divisor of num
@{
num = $1
for (divisor = 2; divisor * divisor <= num; divisor++) @{
if (num % divisor == 0)
break
@}
@end group
@group
if (num % divisor == 0)
printf "Smallest divisor of %d is %d\n", num, divisor
else
printf "%d is prime\n", num
@}
@end group
@end example
When the remainder is zero in the first @code{if} statement, @command{awk}
immediately @dfn{breaks out} of the containing @code{for} loop. This means
that @command{awk} proceeds immediately to the statement following the loop
and continues processing. (This is very different from the @code{exit}
statement, which stops the entire @command{awk} program.
@xref{Exit Statement}.)
The following program illustrates how the @var{condition} of a @code{for}
or @code{while} statement could be replaced with a @code{break} inside
an @code{if}:
@example
# find smallest divisor of num
@{
num = $1
for (divisor = 2; ; divisor++) @{
if (num % divisor == 0) @{
printf "Smallest divisor of %d is %d\n", num, divisor
break
@}
if (divisor * divisor > num) @{
printf "%d is prime\n", num
break
@}
@}
@}
@end example
The @code{break} statement is also used to break out of the
@code{switch} statement.
This is discussed in @ref{Switch Statement}.
@c @cindex @code{break}, outside of loops
@c @cindex historical features
@c @cindex @command{awk} language, POSIX version
@cindex POSIX @command{awk} @subentry @code{break} statement and
@cindex dark corner @subentry @code{break} statement
@cindex @command{gawk} @subentry @code{break} statement in
@cindex Brian Kernighan's @command{awk}
The @code{break} statement has no meaning when
used outside the body of a loop or @code{switch}.
However, although it was never documented,
historical implementations of @command{awk} treated the @code{break}
statement outside of a loop as if it were a @code{next} statement
(@pxref{Next Statement}).
@value{DARKCORNER}
Recent versions of BWK @command{awk} no longer allow this usage,
nor does @command{gawk}.
@node Continue Statement
@subsection The @code{continue} Statement
@cindex @code{continue} statement
Similar to @code{break}, the @code{continue} statement is used only inside
@code{for}, @code{while}, and @code{do} loops. It skips
over the rest of the loop body, causing the next cycle around the loop
to begin immediately. Contrast this with @code{break}, which jumps out
of the loop altogether.
The @code{continue} statement in a @code{for} loop directs @command{awk} to
skip the rest of the body of the loop and resume execution with the
increment-expression of the @code{for} statement. The following program
illustrates this fact:
@example
BEGIN @{
for (x = 0; x <= 20; x++) @{
if (x == 5)
continue
printf "%d ", x
@}
print ""
@}
@end example
@noindent
This program prints all the numbers from 0 to 20---except for 5, for
which the @code{printf} is skipped. Because the increment @samp{x++}
is not skipped, @code{x} does not remain stuck at 5. Contrast the
@code{for} loop from the previous example with the following @code{while} loop:
@example
BEGIN @{
x = 0
while (x <= 20) @{
if (x == 5)
continue
printf "%d ", x
x++
@}
print ""
@}
@end example
@noindent
This program loops forever once @code{x} reaches 5, because
the increment (@samp{x++}) is never reached.
@c @cindex @code{continue}, outside of loops
@c @cindex historical features
@c @cindex @command{awk} language, POSIX version
@cindex POSIX @command{awk} @subentry @code{continue} statement and
@cindex dark corner @subentry @code{continue} statement
@cindex @command{gawk} @subentry @code{continue} statement in
@cindex Brian Kernighan's @command{awk}
The @code{continue} statement has no special meaning with respect to the
@code{switch} statement, nor does it have any meaning when used outside the
body of a loop. Historical versions of @command{awk} treated a @code{continue}
statement outside a loop the same way they treated a @code{break}
statement outside a loop: as if it were a @code{next}
statement
@ifset FOR_PRINT
(discussed in the following @value{SECTION}).
@end ifset
@ifclear FOR_PRINT
(@pxref{Next Statement}).
@end ifclear
@value{DARKCORNER}
Recent versions of BWK @command{awk} no longer work this way, nor
does @command{gawk}.
@node Next Statement
@subsection The @code{next} Statement
@cindex @code{next} statement
The @code{next} statement forces @command{awk} to immediately stop processing
the current record and go on to the next record. This means that no
further rules are executed for the current record, and the rest of the
current rule's action isn't executed.
Contrast this with the effect of the @code{getline} function
(@pxref{Getline}). That also causes
@command{awk} to read the next record immediately, but it does not alter the
flow of control in any way (i.e., the rest of the current action executes
with a new input record).
@cindex @command{awk} programs @subentry execution of
At the highest level, @command{awk} program execution is a loop that reads
an input record and then tests each rule's pattern against it. If you
think of this loop as a @code{for} statement whose body contains the
rules, then the @code{next} statement is analogous to a @code{continue}
statement. It skips to the end of the body of this implicit loop and
executes the increment (which reads another record).
For example, suppose an @command{awk} program works only on records
with four fields, and it shouldn't fail when given bad input. To avoid
complicating the rest of the program, write a ``weed out'' rule near
the beginning, in the following manner:
@example
NF != 4 @{
printf("%s:%d: skipped: NF != 4\n", FILENAME, FNR) > "/dev/stderr"
next
@}
@end example
@noindent
Because of the @code{next} statement,
the program's subsequent rules won't see the bad record. The error
message is redirected to the standard error output stream, as error
messages should be.
For more detail, see
@ref{Special Files}.
If the @code{next} statement causes the end of the input to be reached,
then the code in any @code{END} rules is executed.
@xref{BEGIN/END}.
The @code{next} statement is not allowed inside @code{BEGINFILE} and
@code{ENDFILE} rules. @xref{BEGINFILE/ENDFILE}.
@c @cindex @code{next}, inside a user-defined function
@cindex @command{awk} @subentry language, POSIX version
@cindex @code{BEGIN} pattern @subentry @code{next}/@code{nextfile} statements and
@cindex @code{END} pattern @subentry @code{next}/@code{nextfile} statements and
@cindex POSIX @command{awk} @subentry @code{next}/@code{nextfile} statements and
@cindex @code{next} statement @subentry user-defined functions and
@cindex functions @subentry user-defined @subentry @code{next}/@code{nextfile} statements and
According to the POSIX standard, the behavior is undefined if the
@code{next} statement is used in a @code{BEGIN} or @code{END} rule.
@command{gawk} treats it as a syntax error. Although POSIX does not disallow it,
most other @command{awk} implementations don't allow the @code{next}
statement inside function bodies (@pxref{User-defined}). Just as with any
other @code{next} statement, a @code{next} statement inside a function
body reads the next record and starts processing it with the first rule
in the program.
@node Nextfile Statement
@subsection The @code{nextfile} Statement
@cindex @code{nextfile} statement
The @code{nextfile} statement
is similar to the @code{next} statement.
However, instead of abandoning processing of the current record, the
@code{nextfile} statement instructs @command{awk} to stop processing the
current @value{DF}.
Upon execution of the @code{nextfile} statement,
@code{FILENAME} is
updated to the name of the next @value{DF} listed on the command line,
@code{FNR} is reset to one,
and processing
starts over with the first rule in the program.
If the @code{nextfile} statement causes the end of the input to be reached,
then the code in any @code{END} rules is executed. An exception to this is
when @code{nextfile} is invoked during execution of any statement in an
@code{END} rule; in this case, it causes the program to stop immediately.
@xref{BEGIN/END}.
The @code{nextfile} statement is useful when there are many @value{DF}s
to process but it isn't necessary to process every record in every file.
Without @code{nextfile},
in order to move on to the next @value{DF}, a program
would have to continue scanning the unwanted records. The @code{nextfile}
statement accomplishes this much more efficiently.
In @command{gawk}, execution of @code{nextfile} causes additional things
to happen: any @code{ENDFILE} rules are executed if @command{gawk} is
not currently in an @code{END} or @code{BEGINFILE} rule, @code{ARGIND} is
incremented, and any @code{BEGINFILE} rules are executed. (@code{ARGIND}
hasn't been introduced yet. @xref{Built-in Variables}.)
With @command{gawk}, @code{nextfile} is useful inside a @code{BEGINFILE}
rule to skip over a file that would otherwise cause @command{gawk}
to exit with a fatal error. In this case, @code{ENDFILE} rules are not
executed. @xref{BEGINFILE/ENDFILE}.
Although it might seem that @samp{close(FILENAME)} would accomplish
the same as @code{nextfile}, this isn't true. @code{close()} is
reserved for closing files, pipes, and coprocesses that are
opened with redirections. It is not related to the main processing that
@command{awk} does with the files listed in @code{ARGV}.
@quotation NOTE
For many years, @code{nextfile} was a
common extension. In September 2012, it was accepted for
inclusion into the POSIX standard.
See @uref{http://austingroupbugs.net/view.php?id=607, the Austin Group website}.
@end quotation
@cindex functions @subentry user-defined @subentry @code{next}/@code{nextfile} statements and
@cindex @code{nextfile} statement @subentry user-defined functions and
@cindex Brian Kernighan's @command{awk}
@cindex @command{mawk} utility
The current version of BWK @command{awk} and @command{mawk}
also support @code{nextfile}. However, they don't allow the
@code{nextfile} statement inside function bodies (@pxref{User-defined}).
@command{gawk} does; a @code{nextfile} inside a function body reads the
first record from the next file and starts processing it with the first
rule in the program, just as any other @code{nextfile} statement.
@node Exit Statement
@subsection The @code{exit} Statement
@cindex @code{exit} statement
The @code{exit} statement causes @command{awk} to immediately stop
executing the current rule and to stop processing input; any remaining input
is ignored. The @code{exit} statement is written as follows:
@display
@code{exit} [@var{return code}]
@end display
@cindex @code{BEGIN} pattern @subentry @code{exit} statement and
@cindex @code{END} pattern @subentry @code{exit} statement and
When an @code{exit} statement is executed from a @code{BEGIN} rule, the
program stops processing everything immediately. No input records are
read. However, if an @code{END} rule is present,
as part of executing the @code{exit} statement,
the @code{END} rule is executed
(@pxref{BEGIN/END}).
If @code{exit} is used in the body of an @code{END} rule, it causes
the program to stop immediately.
An @code{exit} statement that is not part of a @code{BEGIN} or @code{END}
rule stops the execution of any further automatic rules for the current
record, skips reading any remaining input records, and executes the
@code{END} rule if there is one. @command{gawk} also skips
any @code{ENDFILE} rules; they do not execute.
In such a case,
if you don't want the @code{END} rule to do its job, set a variable
to a nonzero value before the @code{exit} statement and check that variable in
the @code{END} rule.
@xref{Assert Function}
for an example that does this.
@cindex dark corner @subentry @code{exit} statement
If an argument is supplied to @code{exit}, its value is used as the exit
status code for the @command{awk} process. If no argument is supplied,
@code{exit} causes @command{awk} to return a ``success'' status.
In the case where an argument
is supplied to a first @code{exit} statement, and then @code{exit} is
called a second time from an @code{END} rule with no argument,
@command{awk} uses the previously supplied exit value. @value{DARKCORNER}
@xref{Exit Status} for more information.
@cindex programming conventions @subentry @code{exit} statement
For example, suppose an error condition occurs that is difficult or
impossible to handle. Conventionally, programs report this by
exiting with a nonzero status. An @command{awk} program can do this
using an @code{exit} statement with a nonzero argument, as shown
in the following example:
@example
@group
BEGIN @{
if (("date" | getline date_now) <= 0) @{
print "Can't get system date" > "/dev/stderr"
exit 1
@}
@end group
@group
print "current date is", date_now
close("date")
@}
@end group
@end example
@quotation NOTE
For full portability, exit values should be between zero and 126, inclusive.
Negative values, and values of 127 or greater, may not produce consistent
results across different operating systems.
@end quotation
@node Built-in Variables
@section Predefined Variables
@cindex predefined variables
@cindex variables @subentry predefined
Most @command{awk} variables are available to use for your own
purposes; they never change unless your program assigns values to
them, and they never affect anything unless your program examines them.
However, a few variables in @command{awk} have special built-in meanings.
@command{awk} examines some of these automatically, so that they enable you
to tell @command{awk} how to do certain things. Others are set
automatically by @command{awk}, so that they carry information from the
internal workings of @command{awk} to your program.
@cindex @command{gawk} @subentry predefined variables and
This @value{SECTION} documents all of @command{gawk}'s predefined variables,
most of which are also documented in the @value{CHAPTER}s describing
their areas of activity.
@menu
* User-modified:: Built-in variables that you change to control
@command{awk}.
* Auto-set:: Built-in variables where @command{awk} gives
you information.
* ARGC and ARGV:: Ways to use @code{ARGC} and @code{ARGV}.
@end menu
@node User-modified
@subsection Built-in Variables That Control @command{awk}
@cindex predefined variables @subentry user-modifiable
@cindex user-modifiable variables
The following is an alphabetical list of variables that you can change to
control how @command{awk} does certain things.
The variables that are specific to @command{gawk} are marked with a pound
sign (@samp{#}). These variables are @command{gawk} extensions. In other
@command{awk} implementations or if @command{gawk} is in compatibility
mode (@pxref{Options}), they are not special. (Any exceptions are noted
in the description of each variable.)
@table @code
@cindex @code{BINMODE} variable
@cindex binary input/output
@cindex input/output @subentry binary
@cindex differences in @command{awk} and @command{gawk} @subentry @code{BINMODE} variable
@item BINMODE #
On non-POSIX systems, this variable specifies use of binary mode
for all I/O. Numeric values of one, two, or three specify that input
files, output files, or all files, respectively, should use binary I/O.
A numeric value less than zero is treated as zero, and a numeric value
greater than three is treated as three. Alternatively, string values
of @code{"r"} or @code{"w"} specify that input files and output files,
respectively, should use binary I/O. A string value of @code{"rw"} or
@code{"wr"} indicates that all files should use binary I/O. Any other
string value is treated the same as @code{"rw"}, but causes @command{gawk}
to generate a warning message. @code{BINMODE} is described in more
detail in @ref{PC Using}. @command{mawk} (@pxref{Other Versions})
also supports this variable, but only using numeric values.
@cindex @code{CONVFMT} variable
@cindex POSIX @command{awk} @subentry @code{CONVFMT} variable and
@cindex numbers @subentry converting @subentry to strings
@cindex strings @subentry converting @subentry numbers to
@item @code{CONVFMT}
A string that controls the conversion of numbers to
strings (@pxref{Conversion}).
It works by being passed, in effect, as the first argument to the
@code{sprintf()} function
(@pxref{String Functions}).
Its default value is @code{"%.6g"}.
@code{CONVFMT} was introduced by the POSIX standard.
@cindex @command{gawk} @subentry @code{FIELDWIDTHS} variable in
@cindex @code{FIELDWIDTHS} variable
@cindex differences in @command{awk} and @command{gawk} @subentry @code{FIELDWIDTHS} variable
@cindex field separator @subentry @code{FIELDWIDTHS} variable and
@cindex separators @subentry field @subentry @code{FIELDWIDTHS} variable and
@item FIELDWIDTHS #
A space-separated list of columns that tells @command{gawk}
how to split input with fixed columnar boundaries.
Starting in @value{PVERSION} 4.2, each field width may optionally be
preceded by a colon-separated value specifying the number of characters to skip
before the field starts.
Assigning a value to @code{FIELDWIDTHS}
overrides the use of @code{FS} and @code{FPAT} for field splitting.
@xref{Constant Size} for more information.
@cindex @command{gawk} @subentry @code{FPAT} variable in
@cindex @code{FPAT} variable
@cindex differences in @command{awk} and @command{gawk} @subentry @code{FPAT} variable
@cindex field separator @subentry @code{FPAT} variable and
@cindex separators @subentry field @subentry @code{FPAT} variable and
@item FPAT #
A regular expression (as a string) that tells @command{gawk}
to create the fields based on text that matches the regular expression.
Assigning a value to @code{FPAT}
overrides the use of @code{FS} and @code{FIELDWIDTHS} for field splitting.
@xref{Splitting By Content} for more information.
@cindex @code{FS} variable
@cindex separators @subentry field
@cindex field separator
@item FS
The input field separator (@pxref{Field Separators}).
The value is a single-character string or a multicharacter regular
expression that matches the separations between fields in an input
record. If the value is the null string (@code{""}), then each
character in the record becomes a separate field.
(This behavior is a @command{gawk} extension. POSIX @command{awk} does not
specify the behavior when @code{FS} is the null string.
Nonetheless, some other versions of @command{awk} also treat
@code{""} specially.)
The default value is @w{@code{" "}}, a string consisting of a single
space. As a special exception, this value means that any sequence of
spaces, TABs, and/or newlines is a single separator. It also causes
spaces, TABs, and newlines at the beginning and end of a record to
be ignored.
You can set the value of @code{FS} on the command line using the
@option{-F} option:
@example
awk -F, '@var{program}' @var{input-files}
@end example
@cindex @command{gawk} @subentry field separators and
If @command{gawk} is using @code{FIELDWIDTHS} or @code{FPAT}
for field splitting,
assigning a value to @code{FS} causes @command{gawk} to return to
the normal, @code{FS}-based field splitting. An easy way to do this
is to simply say @samp{FS = FS}, perhaps with an explanatory comment.
@cindex @command{gawk} @subentry @code{IGNORECASE} variable in
@cindex @code{IGNORECASE} variable
@cindex differences in @command{awk} and @command{gawk} @subentry @code{IGNORECASE} variable
@cindex case sensitivity @subentry string comparisons and
@cindex case sensitivity @subentry regexps and
@cindex regular expressions @subentry case sensitivity
@item IGNORECASE #
If @code{IGNORECASE} is nonzero or non-null, then all string comparisons
and all regular expression matching are case-independent.
This applies to
regexp matching with @samp{~} and @samp{!~},
the @code{gensub()}, @code{gsub()}, @code{index()}, @code{match()},
@code{patsplit()}, @code{split()}, and @code{sub()} functions,
record termination with @code{RS}, and field splitting with
@code{FS} and @code{FPAT}.
However, the value of @code{IGNORECASE} does @emph{not} affect array subscripting
and it does not affect field splitting when using a single-character
field separator.
@xref{Case-sensitivity}.
@cindex @command{gawk} @subentry @code{LINT} variable in
@cindex @code{LINT} variable
@cindex differences in @command{awk} and @command{gawk} @subentry @code{LINT} variable
@cindex lint checking
@item LINT #
When this variable is true (nonzero or non-null), @command{gawk}
behaves as if the @option{--lint} command-line option is in effect
(@pxref{Options}).
With a value of @code{"fatal"}, lint warnings become fatal errors.
With a value of @code{"invalid"}, only warnings about things that are
actually invalid are issued. (This is not fully implemented yet.)
Any other true value prints nonfatal warnings.
Assigning a false value to @code{LINT} turns off the lint warnings.
This variable is a @command{gawk} extension. It is not special
in other @command{awk} implementations. Unlike with the other special variables,
changing @code{LINT} does affect the production of lint warnings,
even if @command{gawk} is in compatibility mode. Much as
the @option{--lint} and @option{--traditional} options independently
control different aspects of @command{gawk}'s behavior, the control
of lint warnings during program execution is independent of the flavor
of @command{awk} being executed.
@cindex @code{OFMT} variable
@cindex numbers @subentry converting @subentry to strings
@cindex strings @subentry converting @subentry numbers to
@item OFMT
A string that controls conversion of numbers to
strings (@pxref{Conversion}) for
printing with the @code{print} statement. It works by being passed
as the first argument to the @code{sprintf()} function
(@pxref{String Functions}).
Its default value is @code{"%.6g"}. Earlier versions of @command{awk}
used @code{OFMT} to specify the format for converting numbers to
strings in general expressions; this is now done by @code{CONVFMT}.
@cindex @code{print} statement @subentry @code{OFMT} variable and
@cindex @code{OFS} variable
@cindex separators @subentry field
@cindex field separator
@item OFS
The output field separator (@pxref{Output Separators}). It is
output between the fields printed by a @code{print} statement. Its
default value is @w{@code{" "}}, a string consisting of a single space.
@cindex @code{ORS} variable
@item ORS
The output record separator. It is output at the end of every
@code{print} statement. Its default value is @code{"\n"}, the newline
character. (@xref{Output Separators}.)
@cindex @code{PREC} variable
@item PREC #
The working precision of arbitrary-precision floating-point numbers,
53 bits by default (@pxref{Setting precision}).
@cindex @code{ROUNDMODE} variable
@item ROUNDMODE #
The rounding mode to use for arbitrary-precision arithmetic on
numbers, by default @code{"N"} (@code{roundTiesToEven} in
the IEEE 754 standard; @pxref{Setting the rounding mode}).
@cindex @code{RS} variable
@cindex separators @subentry for records
@cindex record separators
@item @code{RS}
The input record separator. Its default value is a string
containing a single newline character, which means that an input record
consists of a single line of text.
It can also be the null string, in which case records are separated by
runs of blank lines.
If it is a regexp, records are separated by
matches of the regexp in the input text.
(@xref{Records}.)
The ability for @code{RS} to be a regular expression
is a @command{gawk} extension.
In most other @command{awk} implementations,
or if @command{gawk} is in compatibility mode
(@pxref{Options}),
just the first character of @code{RS}'s value is used.
@cindex @code{SUBSEP} variable
@cindex separators @subentry subscript
@cindex subscript separators
@item @code{SUBSEP}
The subscript separator. It has the default value of
@code{"\034"} and is used to separate the parts of the indices of a
multidimensional array. Thus, the expression @samp{@w{foo["A", "B"]}}
really accesses @code{foo["A\034B"]}
(@pxref{Multidimensional}).
@cindex @command{gawk} @subentry @code{TEXTDOMAIN} variable in
@cindex @code{TEXTDOMAIN} variable
@cindex differences in @command{awk} and @command{gawk} @subentry @code{TEXTDOMAIN} variable
@cindex internationalization @subentry localization
@item TEXTDOMAIN #
Used for internationalization of programs at the
@command{awk} level. It sets the default text domain for specially
marked string constants in the source text, as well as for the
@code{dcgettext()}, @code{dcngettext()}, and @code{bindtextdomain()} functions
(@pxref{Internationalization}).
The default value of @code{TEXTDOMAIN} is @code{"messages"}.
@end table
@node Auto-set
@subsection Built-in Variables That Convey Information
@cindex predefined variables @subentry conveying information
@cindex variables @subentry predefined @subentry conveying information
The following is an alphabetical list of variables that @command{awk}
sets automatically on certain occasions in order to provide
information to your program.
The variables that are specific to @command{gawk} are marked with a pound
sign (@samp{#}). These variables are @command{gawk} extensions. In other
@command{awk} implementations or if @command{gawk} is in compatibility
mode (@pxref{Options}), they are not special:
@c @asis for docbook
@table @asis
@cindex @code{ARGC}/@code{ARGV} variables
@cindex arguments @subentry command-line
@cindex command line @subentry arguments
@item @code{ARGC}, @code{ARGV}
The command-line arguments available to @command{awk} programs are stored in
an array called @code{ARGV}. @code{ARGC} is the number of command-line
arguments present. @xref{Other Arguments}.
Unlike most @command{awk} arrays,
@code{ARGV} is indexed from 0 to @code{ARGC} @minus{} 1.
In the following example:
@example
@group
$ @kbd{awk 'BEGIN @{}
> @kbd{for (i = 0; i < ARGC; i++)}
> @kbd{print ARGV[i]}
> @kbd{@}' inventory-shipped mail-list}
@print{} awk
@print{} inventory-shipped
@print{} mail-list
@end group
@end example
@noindent
@code{ARGV[0]} contains @samp{awk}, @code{ARGV[1]}
contains @samp{inventory-shipped}, and @code{ARGV[2]} contains
@samp{mail-list}. The value of @code{ARGC} is three, one more than the
index of the last element in @code{ARGV}, because the elements are numbered
from zero.
@cindex programming conventions @subentry @code{ARGC}/@code{ARGV} variables
The names @code{ARGC} and @code{ARGV}, as well as the convention of indexing
the array from 0 to @code{ARGC} @minus{} 1, are derived from the C language's
method of accessing command-line arguments.
@cindex dark corner @subentry value of @code{ARGV[0]}
The value of @code{ARGV[0]} can vary from system to system.
Also, you should note that the program text is @emph{not} included in
@code{ARGV}, nor are any of @command{awk}'s command-line options.
@xref{ARGC and ARGV} for information
about how @command{awk} uses these variables.
@value{DARKCORNER}
@cindex @code{ARGIND} variable
@cindex differences in @command{awk} and @command{gawk} @subentry @code{ARGIND} variable
@item @code{ARGIND #}
The index in @code{ARGV} of the current file being processed.
Every time @command{gawk} opens a new @value{DF} for processing, it sets
@code{ARGIND} to the index in @code{ARGV} of the @value{FN}.
When @command{gawk} is processing the input files,
@samp{FILENAME == ARGV[ARGIND]} is always true.
@cindex files @subentry processing, @code{ARGIND} variable and
This variable is useful in file processing; it allows you to tell how far
along you are in the list of @value{DF}s as well as to distinguish between
successive instances of the same @value{FN} on the command line.
@cindex file names @subentry distinguishing
While you can change the value of @code{ARGIND} within your @command{awk}
program, @command{gawk} automatically sets it to a new value when it
opens the next file.
@cindex @code{ENVIRON} array
@cindex environment variables @subentry in @code{ENVIRON} array
@item @code{ENVIRON}
An associative array containing the values of the environment. The array
indices are the environment variable names; the elements are the values of
the particular environment variables. For example,
@code{ENVIRON["HOME"]} might be @code{/home/arnold}.
For POSIX @command{awk}, changing this array does not affect the
environment passed on to any programs that @command{awk} may spawn via
redirection or the @code{system()} function.
However, beginning with @value{PVERSION} 4.2, if not in POSIX
compatibility mode, @command{gawk} does update its own environment when
@code{ENVIRON} is changed, thus changing the environment seen by programs
that it creates. You should therefore be especially careful if you
modify @code{ENVIRON["PATH"]}, which is the search path for finding
executable programs.
This can also affect the running @command{gawk} program, since some of the
built-in functions may pay attention to certain environment variables.
The most notable instance of this is @code{mktime()} (@pxref{Time
Functions}), which pays attention the value of the @env{TZ} environment
variable on many systems.
Some operating systems may not have environment variables.
On such systems, the @code{ENVIRON} array is empty (except for
@w{@code{ENVIRON["AWKPATH"]}} and
@w{@code{ENVIRON["AWKLIBPATH"]}};
@pxref{AWKPATH Variable} and
@ifdocbook
@ref{AWKLIBPATH Variable}).
@end ifdocbook
@ifnotdocbook
@pxref{AWKLIBPATH Variable}).
@end ifnotdocbook
@cindex @command{gawk} @subentry @code{ERRNO} variable in
@cindex @code{ERRNO} variable
@cindex differences in @command{awk} and @command{gawk} @subentry @code{ERRNO} variable
@cindex error handling @subentry @code{ERRNO} variable and
@item @code{ERRNO #}
If a system error occurs during a redirection for @code{getline}, during
a read for @code{getline}, or during a @code{close()} operation, then
@code{ERRNO} contains a string describing the error.
In addition, @command{gawk} clears @code{ERRNO} before opening each
command-line input file. This enables checking if the file is readable
inside a @code{BEGINFILE} pattern (@pxref{BEGINFILE/ENDFILE}).
Otherwise, @code{ERRNO} works similarly to the C variable @code{errno}.
Except for the case just mentioned, @command{gawk} @emph{never} clears
it (sets it to zero or @code{""}). Thus, you should only expect its
value to be meaningful when an I/O operation returns a failure value,
such as @code{getline} returning @minus{}1. You are, of course, free
to clear it yourself before doing an I/O operation.
If the value of @code{ERRNO} corresponds to a system error in the C
@code{errno} variable, then @code{PROCINFO["errno"]} will be set to the value
of @code{errno}. For non-system errors, @code{PROCINFO["errno"]} will
be zero.
@cindex @code{FILENAME} variable
@cindex dark corner @subentry @code{FILENAME} variable
@item @code{FILENAME}
The name of the current input file. When no @value{DF}s are listed
on the command line, @command{awk} reads from the standard input and
@code{FILENAME} is set to @code{"-"}. @code{FILENAME} changes each
time a new file is read (@pxref{Reading Files}). Inside a @code{BEGIN}
rule, the value of @code{FILENAME} is @code{""}, because there are no input
files being processed yet.@footnote{Some early implementations of Unix
@command{awk} initialized @code{FILENAME} to @code{"-"}, even if there
were @value{DF}s to be processed. This behavior was incorrect and should
not be relied upon in your programs.} @value{DARKCORNER} Note, though,
that using @code{getline} (@pxref{Getline}) inside a @code{BEGIN} rule
can give @code{FILENAME} a value.
@cindex @code{FNR} variable
@item @code{FNR}
The current record number in the current file. @command{awk} increments
@code{FNR} each time it reads a new record (@pxref{Records}).
@command{awk} resets @code{FNR} to zero each time it starts a new
input file.
@cindex @code{NF} variable
@item @code{NF}
The number of fields in the current input record.
@code{NF} is set each time a new record is read, when a new field is
created, or when @code{$0} changes (@pxref{Fields}).
Unlike most of the variables described in this @value{SUBSECTION},
assigning a value to @code{NF} has the potential to affect
@command{awk}'s internal workings. In particular, assignments
to @code{NF} can be used to create fields in or remove fields from the
current record. @xref{Changing Fields}.
@cindex @code{FUNCTAB} array
@cindex @command{gawk} @subentry @code{FUNCTAB} array in
@cindex differences in @command{awk} and @command{gawk} @subentry @code{FUNCTAB} variable
@item @code{FUNCTAB #}
An array whose indices and corresponding values are the names of all
the built-in, user-defined, and extension functions in the program.
@quotation NOTE
Attempting to use the @code{delete} statement with the @code{FUNCTAB}
array causes a fatal error. Any attempt to assign to an element of
@code{FUNCTAB} also causes a fatal error.
@end quotation
@cindex @code{NR} variable
@item @code{NR}
The number of input records @command{awk} has processed since
the beginning of the program's execution
(@pxref{Records}).
@command{awk} increments @code{NR} each time it reads a new record.
@cindex @command{gawk} @subentry @code{PROCINFO} array in
@cindex @code{PROCINFO} array
@cindex differences in @command{awk} and @command{gawk} @subentry @code{PROCINFO} array
@item @code{PROCINFO #}
The elements of this array provide access to information about the
running @command{awk} program.
The following elements (listed alphabetically)
are guaranteed to be available:
@table @code
@item PROCINFO["argv"]
@cindex command line @subentry arguments
The @code{PROCINFO["argv"]} array contains all of the command-line arguments
(after glob expansion and redirection processing on platforms where that must
be done manually by the program) with subscripts ranging from 0 through
@code{argc} @minus{} 1. For example, @code{PROCINFO["argv"][0]} will contain
the name by which @command{gawk} was invoked. Here is an example of how this
feature may be used:
@example
gawk '
BEGIN @{
for (i = 0; i < length(PROCINFO["argv"]); i++)
print i, PROCINFO["argv"][i]
@}'
@end example
Please note that this differs from the standard @code{ARGV} array which does
not include command-line arguments that have already been processed by
@command{gawk} (@pxref{ARGC and ARGV}).
@cindex effective group ID of @command{gawk} user
@item PROCINFO["egid"]
The value of the @code{getegid()} system call.
@item PROCINFO["errno"]
The value of the C @code{errno} variable when @code{ERRNO} is set to
the associated error message.
@item PROCINFO["euid"]
@cindex effective user ID of @command{gawk} user
The value of the @code{geteuid()} system call.
@item PROCINFO["FS"]
This is
@code{"FS"} if field splitting with @code{FS} is in effect,
@code{"FIELDWIDTHS"} if field splitting with @code{FIELDWIDTHS} is in effect,
@code{"FPAT"} if field matching with @code{FPAT} is in effect,
or @code{"API"} if field splitting is controlled by an API input parser.
@item PROCINFO["gid"]
@cindex group ID of @command{gawk} user
The value of the @code{getgid()} system call.
@item PROCINFO["identifiers"]
@cindex program identifiers
A subarray, indexed by the names of all identifiers used in the text of
the @command{awk} program. An @dfn{identifier} is simply the name of a variable
(be it scalar or array), built-in function, user-defined function, or
extension function. For each identifier, the value of the element is
one of the following:
@table @code
@item "array"
The identifier is an array.
@item "builtin"
The identifier is a built-in function.
@item "extension"
The identifier is an extension function loaded via
@code{@@load} or @option{-l}.
@item "scalar"
The identifier is a scalar.
@item "untyped"
The identifier is untyped (could be used as a scalar or an array;
@command{gawk} doesn't know yet).
@item "user"
The identifier is a user-defined function.
@end table
@noindent
The values indicate what @command{gawk} knows about the identifiers
after it has finished parsing the program; they are @emph{not} updated
while the program runs.
@item PROCINFO["platform"]
@cindex platform running on
@cindex @code{PROCINFO} array @subentry platform running on
This element gives a string indicating the platform for which
@command{gawk} was compiled. The value will be one of the following:
@c nested table
@table @code
@item "djgpp"
@itemx "mingw"
Microsoft Windows, using either DJGPP or MinGW, respectively.
@item "os2"
OS/2.
@item "os390"
OS/390.
@item "posix"
GNU/Linux, Cygwin, Mac OS X, and legacy Unix systems.
@item "vms"
OpenVMS or Vax/VMS.
@end table
@item PROCINFO["pgrpid"]
@cindex process group ID of @command{gawk} process
The process group ID of the current process.
@item PROCINFO["pid"]
@cindex process ID of @command{gawk} process
The process ID of the current process.
@item PROCINFO["ppid"]
@cindex parent process ID of @command{gawk} process
The parent process ID of the current process.
@item PROCINFO["strftime"]
The default time format string for @code{strftime()}.
Assigning a new value to this element changes the default.
@xref{Time Functions}.
@item PROCINFO["uid"]
The value of the @code{getuid()} system call.
@item PROCINFO["version"]
@cindex version of @subentry @command{gawk}
@cindex @command{gawk} @subentry version of
The version of @command{gawk}.
@end table
The following additional elements in the array
are available to provide information about the MPFR and GMP libraries
if your version of @command{gawk} supports arbitrary-precision arithmetic
(@pxref{Arbitrary Precision Arithmetic}):
@table @code
@item PROCINFO["gmp_version"]
@cindex version of @subentry GNU MP library
The version of the GNU MP library.
@cindex version of @subentry GNU MPFR library
@item PROCINFO["mpfr_version"]
The version of the GNU MPFR library.
@item PROCINFO["prec_max"]
@cindex maximum precision supported by MPFR library
The maximum precision supported by MPFR.
@item PROCINFO["prec_min"]
@cindex minimum precision required by MPFR library
The minimum precision required by MPFR.
@end table
The following additional elements in the array are available to provide
information about the version of the extension API, if your version
of @command{gawk} supports dynamic loading of extension functions
(@pxref{Dynamic Extensions}):
@table @code
@item PROCINFO["api_major"]
@cindex version of @subentry @command{gawk} extension API
@cindex extension API @subentry version number
The major version of the extension API.
@item PROCINFO["api_minor"]
The minor version of the extension API.
@end table
@cindex supplementary groups of @command{gawk} process
On some systems, there may be elements in the array, @code{"group1"}
through @code{"group@var{N}"} for some @var{N}. @var{N} is the number of
supplementary groups that the process has. Use the @code{in} operator
to test for these elements
(@pxref{Reference to Elements}).
The following elements allow you to change @command{gawk}'s behavior:
@table @code
@item PROCINFO["NONFATAL"]
If this element exists, then I/O errors for all redirections become nonfatal.
@xref{Nonfatal}.
@item PROCINFO["@var{name}", "NONFATAL"]
Make I/O errors for @var{name} be nonfatal.
@xref{Nonfatal}.
@item PROCINFO["@var{command}", "pty"]
For two-way communication to @var{command}, use a pseudo-tty instead
of setting up a two-way pipe.
@xref{Two-way I/O} for more information.
@item PROCINFO["@var{input_name}", "READ_TIMEOUT"]
Set a timeout for reading from input redirection @var{input_name}.
@xref{Read Timeout} for more information.
@item PROCINFO["@var{input_name}", "RETRY"]
If an I/O error that may be retried occurs when reading data from
@var{input_name}, and this array entry exists, then @code{getline} returns
@minus{}2 instead of following the default behavior of returning @minus{}1
and configuring @var{input_name} to return no further data. An I/O error
that may be retried is one where @code{errno} has the value @code{EAGAIN},
@code{EWOULDBLOCK}, @code{EINTR}, or @code{ETIMEDOUT}. This may be useful
in conjunction with @code{PROCINFO["@var{input_name}", "READ_TIMEOUT"]}
or situations where a file descriptor has been configured to behave in
a non-blocking fashion.
@xref{Retrying Input} for more information.
@item PROCINFO["sorted_in"]
If this element exists in @code{PROCINFO}, its value controls the
order in which array indices will be processed by
@samp{for (@var{indx} in @var{array})} loops.
This is an advanced feature, so we defer the
full description until later; see
@ref{Controlling Scanning}.
@end table
@cindex @code{RLENGTH} variable
@item @code{RLENGTH}
The length of the substring matched by the
@code{match()} function
(@pxref{String Functions}).
@code{RLENGTH} is set by invoking the @code{match()} function. Its value
is the length of the matched string, or @minus{}1 if no match is found.
@cindex @code{RSTART} variable
@item @code{RSTART}
The start index in characters of the substring that is matched by the
@code{match()} function
(@pxref{String Functions}).
@code{RSTART} is set by invoking the @code{match()} function. Its value
is the position of the string where the matched substring starts, or zero
if no match was found.
@cindex @command{gawk} @subentry @code{RT} variable in
@cindex @code{RT} variable
@cindex differences in @command{awk} and @command{gawk} @subentry @code{RS}/@code{RT} variables
@item @code{RT #}
The input text that matched the text denoted by @code{RS},
the record separator. It is set every time a record is read.
@cindex @command{gawk} @subentry @code{SYMTAB} array in
@cindex @code{SYMTAB} array
@cindex differences in @command{awk} and @command{gawk} @subentry @code{SYMTAB} variable
@item @code{SYMTAB #}
An array whose indices are the names of all defined global variables and
arrays in the program. @code{SYMTAB} makes @command{gawk}'s symbol table
visible to the @command{awk} programmer. It is built as @command{gawk}
parses the program and is complete before the program starts to run.
The array may be used for indirect access to read or write the value of
a variable:
@example
foo = 5
SYMTAB["foo"] = 4
print foo # prints 4
@end example
@noindent
The @code{isarray()} function (@pxref{Type Functions}) may be used to test
if an element in @code{SYMTAB} is an array.
Also, you may not use the @code{delete} statement with the
@code{SYMTAB} array.
Prior to @value{PVERSION} 5.0 of @command{gawk}, you could
use an index for @code{SYMTAB} that was not a predefined identifier:
@example
SYMTAB["xxx"] = 5
print SYMTAB["xxx"]
@end example
@noindent
This no longer works, instead producing a fatal error, as it led
to rampant confusion.
@cindex Schorr, Andrew
The @code{SYMTAB} array is more interesting than it looks. Andrew Schorr
points out that it effectively gives @command{awk} data pointers. Consider his
example:
@example
@group
# Indirect multiply of any variable by amount, return result
function multiply(variable, amount)
@{
return SYMTAB[variable] *= amount
@}
@end group
@end example
@noindent
You would use it like this:
@example
BEGIN @{
answer = 10.5
multiply("answer", 4)
print "The answer is", answer
@}
@end example
@noindent
When run, this produces:
@example
$ @kbd{gawk -f answer.awk}
@print{} The answer is 42
@end example
@quotation NOTE
In order to avoid severe time-travel paradoxes,@footnote{Not to mention
difficult implementation issues.} neither @code{FUNCTAB} nor @code{SYMTAB}
is available as an element within the @code{SYMTAB} array.
@end quotation
@end table
@cindex sidebar @subentry Changing @code{NR} and @code{FNR}
@ifdocbook
@docbook
<sidebar><title>Changing @code{NR} and @code{FNR}</title>
@end docbook
@cindex @code{NR} variable @subentry changing
@cindex @code{FNR} variable @subentry changing
@cindex dark corner @subentry @code{FNR}/@code{NR} variables
@command{awk} increments @code{NR} and @code{FNR}
each time it reads a record, instead of setting them to the absolute
value of the number of records read. This means that a program can
change these variables and their new values are incremented for
each record.
@value{DARKCORNER}
The following example shows this:
@example
$ @kbd{echo '1}
> @kbd{2}
> @kbd{3}
> @kbd{4' | awk 'NR == 2 @{ NR = 17 @}}
> @kbd{@{ print NR @}'}
@print{} 1
@print{} 17
@print{} 18
@print{} 19
@end example
@noindent
Before @code{FNR} was added to the @command{awk} language
(@pxref{V7/SVR3.1}),
many @command{awk} programs used this feature to track the number of
records in a file by resetting @code{NR} to zero when @code{FILENAME}
changed.
@docbook
</sidebar>
@end docbook
@end ifdocbook
@ifnotdocbook
@cartouche
@center @b{Changing @code{NR} and @code{FNR}}
@cindex @code{NR} variable @subentry changing
@cindex @code{FNR} variable @subentry changing
@cindex dark corner @subentry @code{FNR}/@code{NR} variables
@command{awk} increments @code{NR} and @code{FNR}
each time it reads a record, instead of setting them to the absolute
value of the number of records read. This means that a program can
change these variables and their new values are incremented for
each record.
@value{DARKCORNER}
The following example shows this:
@example
$ @kbd{echo '1}
> @kbd{2}
> @kbd{3}
> @kbd{4' | awk 'NR == 2 @{ NR = 17 @}}
> @kbd{@{ print NR @}'}
@print{} 1
@print{} 17
@print{} 18
@print{} 19
@end example
@noindent
Before @code{FNR} was added to the @command{awk} language
(@pxref{V7/SVR3.1}),
many @command{awk} programs used this feature to track the number of
records in a file by resetting @code{NR} to zero when @code{FILENAME}
changed.
@end cartouche
@end ifnotdocbook
@node ARGC and ARGV
@subsection Using @code{ARGC} and @code{ARGV}
@cindex @code{ARGC}/@code{ARGV} variables @subentry how to use
@cindex arguments @subentry command-line
@cindex command line @subentry arguments
@ref{Auto-set}
presented the following program describing the information contained in @code{ARGC}
and @code{ARGV}:
@example
@group
$ @kbd{awk 'BEGIN @{}
> @kbd{for (i = 0; i < ARGC; i++)}
> @kbd{print ARGV[i]}
> @kbd{@}' inventory-shipped mail-list}
@print{} awk
@print{} inventory-shipped
@print{} mail-list
@end group
@end example
@noindent
In this example, @code{ARGV[0]} contains @samp{awk}, @code{ARGV[1]}
contains @samp{inventory-shipped}, and @code{ARGV[2]} contains
@samp{mail-list}.
Notice that the @command{awk} program is not entered in @code{ARGV}. The
other command-line options, with their arguments, are also not
entered. This includes variable assignments done with the @option{-v}
option (@pxref{Options}).
Normal variable assignments on the command line @emph{are}
treated as arguments and do show up in the @code{ARGV} array.
Given the following program in a file named @file{showargs.awk}:
@example
BEGIN @{
printf "A=%d, B=%d\n", A, B
for (i = 0; i < ARGC; i++)
printf "\tARGV[%d] = %s\n", i, ARGV[i]
@}
END @{ printf "A=%d, B=%d\n", A, B @}
@end example
@noindent
Running it produces the following:
@example
$ @kbd{awk -v A=1 -f showargs.awk B=2 /dev/null}
@print{} A=1, B=0
@print{} ARGV[0] = awk
@print{} ARGV[1] = B=2
@print{} ARGV[2] = /dev/null
@print{} A=1, B=2
@end example
A program can alter @code{ARGC} and the elements of @code{ARGV}.
Each time @command{awk} reaches the end of an input file, it uses the next
element of @code{ARGV} as the name of the next input file. By storing a
different string there, a program can change which files are read.
Use @code{"-"} to represent the standard input. Storing
additional elements and incrementing @code{ARGC} causes
additional files to be read.
If the value of @code{ARGC} is decreased, that eliminates input files
from the end of the list. By recording the old value of @code{ARGC}
elsewhere, a program can treat the eliminated arguments as
something other than @value{FN}s.
To eliminate a file from the middle of the list, store the null string
(@code{""}) into @code{ARGV} in place of the file's name. As a
special feature, @command{awk} ignores @value{FN}s that have been
replaced with the null string.
Another option is to
use the @code{delete} statement to remove elements from
@code{ARGV} (@pxref{Delete}).
All of these actions are typically done in the @code{BEGIN} rule,
before actual processing of the input begins.
@xref{Split Program} and
@ifnotdocbook
@pxref{Tee Program}
@end ifnotdocbook
@ifdocbook
@ref{Tee Program}
@end ifdocbook
for examples
of each way of removing elements from @code{ARGV}.
To actually get options into an @command{awk} program,
end the @command{awk} options with @option{--} and then supply
the @command{awk} program's options, in the following manner:
@example
awk -f myprog.awk -- -v -q file1 file2 @dots{}
@end example
The following fragment processes @code{ARGV} in order to examine, and
then remove, the previously mentioned command-line options:
@example
BEGIN @{
for (i = 1; i < ARGC; i++) @{
if (ARGV[i] == "-v")
verbose = 1
else if (ARGV[i] == "-q")
debug = 1
else if (ARGV[i] ~ /^-./) @{
e = sprintf("%s: unrecognized option -- %c",
ARGV[0], substr(ARGV[i], 2, 1))
print e > "/dev/stderr"
@} else
break
delete ARGV[i]
@}
@}
@end example
@cindex differences in @command{awk} and @command{gawk} @subentry @code{ARGC}/@code{ARGV} variables
Ending the @command{awk} options with @option{--} isn't
necessary in @command{gawk}. Unless @option{--posix} has
been specified, @command{gawk} silently puts any unrecognized options
into @code{ARGV} for the @command{awk} program to deal with. As soon
as it sees an unknown option, @command{gawk} stops looking for other
options that it might otherwise recognize. The previous command line with
@command{gawk} would be:
@example
gawk -f myprog.awk -q -v file1 file2 @dots{}
@end example
@noindent
Because @option{-q} is not a valid @command{gawk} option, it and the
following @option{-v} are passed on to the @command{awk} program.
(@xref{Getopt Function} for an @command{awk} library function that
parses command-line options.)
When designing your program, you should choose options that don't
conflict with @command{gawk}'s, because it will process any options
that it accepts before passing the rest of the command line on to
your program. Using @samp{#!} with the @option{-E} option may help
(@pxref{Executable Scripts}
and
@ifnotdocbook
@pxref{Options}).
@end ifnotdocbook
@ifdocbook
@ref{Options}).
@end ifdocbook
@node Pattern Action Summary
@section Summary
@itemize @value{BULLET}
@item
Pattern--action pairs make up the basic elements of an @command{awk}
program. Patterns are either normal expressions, range expressions,
or regexp constants; one of the special keywords @code{BEGIN}, @code{END},
@code{BEGINFILE}, or @code{ENDFILE}; or empty. The action executes if
the current record matches the pattern. Empty (missing) patterns match
all records.
@item
I/O from @code{BEGIN} and @code{END} rules has certain constraints.
This is also true, only more so, for @code{BEGINFILE} and @code{ENDFILE}
rules. The latter two give you ``hooks'' into @command{gawk}'s file
processing, allowing you to recover from a file that otherwise would
cause a fatal error (such as a file that cannot be opened).
@item
Shell variables can be used in @command{awk} programs by careful
use of shell quoting. It is easier to pass a shell variable into
@command{awk} by using the @option{-v} option and an @command{awk}
variable.
@item
Actions consist of statements enclosed in curly braces. Statements
are built up from expressions, control statements, compound statements,
input and output statements, and deletion statements.
@item
The control statements in @command{awk} are @code{if}-@code{else},
@code{while}, @code{for}, and @code{do}-@code{while}. @command{gawk}
adds the @code{switch} statement. There are two flavors of @code{for}
statement: one for performing general looping, and the other for iterating
through an array.
@item
@code{break} and @code{continue} let you exit early or start the next
iteration of a loop (or get out of a @code{switch}).
@item
@code{next} and @code{nextfile} let you read the next record and start
over at the top of your program or skip to the next input file and
start over, respectively.
@item
The @code{exit} statement terminates your program. When executed
from an action (or function body), it transfers control to the
@code{END} statements. From an @code{END} statement body, it exits
immediately. You may pass an optional numeric value to be used
as @command{awk}'s exit status.
@item
Some predefined variables provide control over @command{awk}, mainly for I/O.
Other variables convey information from @command{awk} to your program.
@item
@code{ARGC} and @code{ARGV} make the command-line arguments available
to your program. Manipulating them from a @code{BEGIN} rule lets you
control how @command{awk} will process the provided @value{DF}s.
@end itemize
@node Arrays
@chapter Arrays in @command{awk}
@cindex arrays
An @dfn{array} is a table of values called @dfn{elements}. The
elements of an array are distinguished by their @dfn{indices}. Indices
may be either numbers or strings.
This @value{CHAPTER} describes how arrays work in @command{awk},
how to use array elements, how to scan through every element in an array,
and how to remove array elements.
It also describes how @command{awk} simulates multidimensional
arrays, as well as some of the less obvious points about array usage.
The @value{CHAPTER} moves on to discuss @command{gawk}'s facility
for sorting arrays, and ends with a brief description of @command{gawk}'s
ability to support true arrays of arrays.
@menu
* Array Basics:: The basics of arrays.
* Numeric Array Subscripts:: How to use numbers as subscripts in
@command{awk}.
* Uninitialized Subscripts:: Using Uninitialized variables as subscripts.
* Delete:: The @code{delete} statement removes an element
from an array.
* Multidimensional:: Emulating multidimensional arrays in
@command{awk}.
* Arrays of Arrays:: True multidimensional arrays.
* Arrays Summary:: Summary of arrays.
@end menu
@node Array Basics
@section The Basics of Arrays
This @value{SECTION} presents the basics: working with elements
in arrays one at a time, and traversing all of the elements in
an array.
@menu
* Array Intro:: Introduction to Arrays
* Reference to Elements:: How to examine one element of an array.
* Assigning Elements:: How to change an element of an array.
* Array Example:: Basic Example of an Array
* Scanning an Array:: A variation of the @code{for} statement. It
loops through the indices of an array's
existing elements.
* Controlling Scanning:: Controlling the order in which arrays are
scanned.
@end menu
@node Array Intro
@subsection Introduction to Arrays
@cindex Wall, Larry
@quotation
@i{Doing linear scans over an associative array is like trying to club someone
to death with a loaded Uzi.}
@author Larry Wall
@end quotation
The @command{awk} language provides one-dimensional arrays
for storing groups of related strings or numbers.
Every @command{awk} array must have a name. Array names have the same
syntax as variable names; any valid variable name would also be a valid
array name. But one name cannot be used in both ways (as an array and
as a variable) in the same @command{awk} program.
Arrays in @command{awk} superficially resemble arrays in other programming
languages, but there are fundamental differences. In @command{awk}, it
isn't necessary to specify the size of an array before starting to use it.
Additionally, any number or string, not just consecutive integers,
may be used as an array index.
In most other languages, arrays must be @dfn{declared} before use,
including a specification of
how many elements or components they contain. In such languages, the
declaration causes a contiguous block of memory to be allocated for that
many elements. Usually, an index in the array must be a nonnegative integer.
For example, the index zero specifies the first element in the array, which is
actually stored at the beginning of the block of memory. Index one
specifies the second element, which is stored in memory right after the
first element, and so on. It is impossible to add more elements to the
array, because it has room only for as many elements as given in
the declaration.
(Some languages allow arbitrary starting and ending
indices---e.g., @samp{15 .. 27}---but the size of the array is still fixed when
the array is declared.)
@c 1/2015: Do not put the numeric values into @code. Array element
@c values are no different than scalar variable values.
A contiguous array of four elements might look like
@ifnotdocbook
@ref{figure-array-elements},
@end ifnotdocbook
@ifdocbook
@inlineraw{docbook, <xref linkend="figure-array-elements"/>},
@end ifdocbook
conceptually, if the element values are eight, @code{"foo"},
@code{""}, and 30.
@ifnotdocbook
@float Figure,figure-array-elements
@caption{A contiguous array}
@center @image{gawk_array-elements, , , A Contiguous Array}
@end float
@end ifnotdocbook
@docbook
<figure id="figure-array-elements" float="0">
<title>A contiguous array</title>
<mediaobject>
<imageobject role="web"><imagedata fileref="gawk_array-elements.png" format="PNG"/></imageobject>
</mediaobject>
</figure>
@end docbook
@noindent
Only the values are stored; the indices are implicit from the order of
the values. Here, eight is the value at index zero, because eight appears in the
position with zero elements before it.
@cindex arrays @subentry indexing
@cindex indexing arrays
@cindex associative arrays
@cindex arrays @subentry associative
Arrays in @command{awk} are different---they are @dfn{associative}. This means
that each array is a collection of pairs---an index and its corresponding
array element value:
@ifnotdocbook
@c extra empty column to indent it right
@multitable @columnfractions .1 .1 .1
@headitem @tab Index @tab Value
@item @tab @code{3} @tab @code{30}
@item @tab @code{1} @tab @code{"foo"}
@item @tab @code{0} @tab @code{8}
@item @tab @code{2} @tab @code{""}
@end multitable
@end ifnotdocbook
@docbook
<informaltable>
<tgroup cols="2">
<colspec colname="1" align="left"/>
<colspec colname="2" align="left"/>
<thead>
<row>
<entry>Index</entry>
<entry>Value</entry>
</row>
</thead>
<tbody>
<row>
<entry><literal>3</literal></entry>
<entry><literal>30</literal></entry>
</row>
<row>
<entry><literal>1</literal></entry>
<entry><literal>"foo"</literal></entry>
</row>
<row>
<entry><literal>0</literal></entry>
<entry><literal>8</literal></entry>
</row>
<row>
<entry><literal>2</literal></entry>
<entry><literal>""</literal></entry>
</row>
</tbody>
</tgroup>
</informaltable>
@end docbook
@noindent
The pairs are shown in jumbled order because their order is
irrelevant.@footnote{The ordering will vary among @command{awk}
implementations, which typically use hash tables to store array elements
and values.}
One advantage of associative arrays is that new pairs can be added
at any time. For example, suppose a tenth element is added to the array
whose value is @w{@code{"number ten"}}. The result is:
@ifnotdocbook
@c extra empty column to indent it right
@multitable @columnfractions .1 .1 .2
@headitem @tab Index @tab Value
@item @tab @code{10} @tab @code{"number ten"}
@item @tab @code{3} @tab @code{30}
@item @tab @code{1} @tab @code{"foo"}
@item @tab @code{0} @tab @code{8}
@item @tab @code{2} @tab @code{""}
@end multitable
@end ifnotdocbook
@docbook
<informaltable>
<tgroup cols="2">
<colspec colname="1" align="left"/>
<colspec colname="2" align="left"/>
<thead>
<row>
<entry>Index</entry>
<entry>Value</entry>
</row>
</thead>
<tbody>
<row>
<entry><literal>10</literal></entry>
<entry><literal>"number ten"</literal></entry>
</row>
<row>
<entry><literal>3</literal></entry>
<entry><literal>30</literal></entry>
</row>
<row>
<entry><literal>1</literal></entry>
<entry><literal>"foo"</literal></entry>
</row>
<row>
<entry><literal>0</literal></entry>
<entry><literal>8</literal></entry>
</row>
<row>
<entry><literal>2</literal></entry>
<entry><literal>""</literal></entry>
</row>
</tbody>
</tgroup>
</informaltable>
@end docbook
@noindent
@cindex sparse arrays
@cindex arrays @subentry sparse
Now the array is @dfn{sparse}, which just means some indices are missing.
It has elements 0--3 and 10, but doesn't have elements 4, 5, 6, 7, 8, or 9.
Another consequence of associative arrays is that the indices don't
have to be nonnegative integers. Any number, or even a string, can be
an index. For example, the following is an array that translates words from
English to French:
@ifnotdocbook
@multitable @columnfractions .1 .1 .1
@headitem @tab Index @tab Value
@item @tab @code{"dog"} @tab @code{"chien"}
@item @tab @code{"cat"} @tab @code{"chat"}
@item @tab @code{"one"} @tab @code{"un"}
@item @tab @code{1} @tab @code{"un"}
@end multitable
@end ifnotdocbook
@docbook
<informaltable>
<tgroup cols="2">
<colspec colname="1" align="left"/>
<colspec colname="2" align="left"/>
<thead>
<row>
<entry>Index</entry>
<entry>Value</entry>
</row>
</thead>
<tbody>
<row>
<entry><literal>"dog"</literal></entry>
<entry><literal>"chien"</literal></entry>
</row>
<row>
<entry><literal>"cat"</literal></entry>
<entry><literal>"chat"</literal></entry>
</row>
<row>
<entry><literal>"one"</literal></entry>
<entry><literal>"un"</literal></entry>
</row>
<row>
<entry><literal>1</literal></entry>
<entry><literal>"un"</literal></entry>
</row>
</tbody>
</tgroup>
</informaltable>
@end docbook
@noindent
Here we decided to translate the number one in both spelled-out and
numeric form---thus illustrating that a single array can have both
numbers and strings as indices.
(In fact, array subscripts are always strings.
There are some subtleties to how numbers work when used as
array subscripts; this is discussed in more detail in
@ref{Numeric Array Subscripts}.)
Here, the number @code{1} isn't double-quoted, because @command{awk}
automatically converts it to a string.
@cindex @command{gawk} @subentry @code{IGNORECASE} variable in
@cindex case sensitivity @subentry array indices and
@cindex arrays @subentry @code{IGNORECASE} variable and
@cindex @code{IGNORECASE} variable @subentry array indices and
The value of @code{IGNORECASE} has no effect upon array subscripting.
The identical string value used to store an array element must be used
to retrieve it.
When @command{awk} creates an array (e.g., with the @code{split()}
built-in function),
that array's indices are consecutive integers starting at one.
(@xref{String Functions}.)
@command{awk}'s arrays are efficient---the time to access an element
is independent of the number of elements in the array.
@node Reference to Elements
@subsection Referring to an Array Element
@cindex arrays @subentry referencing elements
@cindex array members
@cindex elements in arrays
The principal way to use an array is to refer to one of its elements.
An @dfn{array reference} is an expression as follows:
@example
@var{array}[@var{index-expression}]
@end example
@noindent
Here, @var{array} is the name of an array. The expression @var{index-expression} is
the index of the desired element of the array.
@c 1/2015: Having the 4.3 in @samp is a little iffy. It's essentially
@c an expression though, so leave be. It's to early in the discussion
@c to mention that it's really a string.
The value of the array reference is the current value of that array
element. For example, @code{foo[4.3]} is an expression referencing the element
of array @code{foo} at index @samp{4.3}.
@cindex arrays @subentry unassigned elements
@cindex unassigned array elements
@cindex empty array elements
A reference to an array element that has no recorded value yields a value of
@code{""}, the null string. This includes elements
that have not been assigned any value as well as elements that have been
deleted (@pxref{Delete}).
@cindex non-existent array elements
@cindex arrays @subentry elements @subentry that don't exist
@quotation NOTE
A reference to an element that does not exist @emph{automatically} creates
that array element, with the null string as its value. (In some cases,
this is unfortunate, because it might waste memory inside @command{awk}.)
Novice @command{awk} programmers often make the mistake of checking if
an element exists by checking if the value is empty:
@example
# Check if "foo" exists in a: @ii{Incorrect!}
if (a["foo"] != "") @dots{}
@end example
@noindent
This is incorrect for two reasons. First, it @emph{creates} @code{a["foo"]}
if it didn't exist before! Second, it is valid (if a bit unusual) to set
an array element equal to the empty string.
@end quotation
@c @cindex arrays, @code{in} operator and
@cindex @code{in} operator @subentry testing if array element exists
To determine whether an element exists in an array at a certain index, use
the following expression:
@example
@var{indx} in @var{array}
@end example
@cindex side effects @subentry array indexing
@noindent
This expression tests whether the particular index @var{indx} exists,
without the side effect of creating that element if it is not present.
The expression has the value one (true) if @code{@var{array}[@var{indx}]}
exists and zero (false) if it does not exist.
(We use @var{indx} here, because @samp{index} is the name of a built-in
function.)
For example, this statement tests whether the array @code{frequencies}
contains the index @samp{2}:
@example
@group
if (2 in frequencies)
print "Subscript 2 is present."
@end group
@end example
Note that this is @emph{not} a test of whether the array
@code{frequencies} contains an element whose @emph{value} is two.
There is no way to do that except to scan all the elements. Also, this
@emph{does not} create @code{frequencies[2]}, while the following
(incorrect) alternative does:
@example
@group
if (frequencies[2] != "")
print "Subscript 2 is present."
@end group
@end example
@node Assigning Elements
@subsection Assigning Array Elements
@cindex arrays @subentry elements @subentry assigning values
@cindex elements in arrays @subentry assigning values
Array elements can be assigned values just like
@command{awk} variables:
@example
@var{array}[@var{index-expression}] = @var{value}
@end example
@noindent
@var{array} is the name of an array. The expression
@var{index-expression} is the index of the element of the array that is
assigned a value. The expression @var{value} is the value to
assign to that element of the array.
@node Array Example
@subsection Basic Array Example
@cindex arrays @subentry example of using
The following program takes a list of lines, each beginning with a line
number, and prints them out in order of line number. The line numbers
are not in order when they are first read---instead, they
are scrambled. This program sorts the lines by making an array using
the line numbers as subscripts. The program then prints out the lines
in sorted order of their numbers. It is a very simple program and gets
confused upon encountering repeated numbers, gaps, or lines that don't
begin with a number:
@example
@c file eg/misc/arraymax.awk
@{
if ($1 > max)
max = $1
arr[$1] = $0
@}
END @{
for (x = 1; x <= max; x++)
print arr[x]
@}
@c endfile
@end example
The first rule keeps track of the largest line number seen so far;
it also stores each line into the array @code{arr}, at an index that
is the line's number.
The second rule runs after all the input has been read, to print out
all the lines.
When this program is run with the following input:
@example
@group
@c file eg/misc/arraymax.data
5 I am the Five man
2 Who are you? The new number two!
4 . . . And four on the floor
1 Who is number one?
3 I three you.
@c endfile
@end group
@end example
@noindent
Its output is:
@example
@group
1 Who is number one?
2 Who are you? The new number two!
3 I three you.
4 . . . And four on the floor
5 I am the Five man
@end group
@end example
If a line number is repeated, the last line with a given number overrides
the others.
Gaps in the line numbers can be handled with an easy improvement to the
program's @code{END} rule, as follows:
@example
@group
END @{
for (x = 1; x <= max; x++)
if (x in arr)
print arr[x]
@}
@end group
@end example
@node Scanning an Array
@subsection Scanning All Elements of an Array
@cindex elements in arrays @subentry scanning
@cindex scanning arrays
@cindex arrays @subentry scanning
@cindex loops @subentry @code{for} @subentry array scanning
In programs that use arrays, it is often necessary to use a loop that
executes once for each element of an array. In other languages, where
arrays are contiguous and indices are limited to nonnegative integers,
this is easy: all the valid indices can be found by counting from
the lowest index up to the highest. This technique won't do the job
in @command{awk}, because any number or string can be an array index.
So @command{awk} has a special kind of @code{for} statement for scanning
an array:
@example
@group
for (@var{var} in @var{array})
@var{body}
@end group
@end example
@noindent
@cindex @code{in} operator @subentry use in loops
This loop executes @var{body} once for each index in @var{array} that the
program has previously used, with the variable @var{var} set to that index.
@cindex arrays @subentry @code{for} statement and
@cindex @code{for} statement @subentry looping over arrays
The following program uses this form of the @code{for} statement. The
first rule scans the input records and notes which words appear (at
least once) in the input, by storing a one into the array @code{used} with
the word as the index. The second rule scans the elements of @code{used} to
find all the distinct words that appear in the input. It prints each
word that is more than 10 characters long and also prints the number of
such words.
@xref{String Functions}
for more information on the built-in function @code{length()}.
@example
@group
# Record a 1 for each word that is used at least once
@{
for (i = 1; i <= NF; i++)
used[$i] = 1
@}
@end group
@group
# Find number of distinct words more than 10 characters long
END @{
for (x in used) @{
if (length(x) > 10) @{
++num_long_words
print x
@}
@}
print num_long_words, "words longer than 10 characters"
@}
@end group
@end example
@noindent
@xref{Word Sorting}
for a more detailed example of this type.
@cindex arrays @subentry elements @subentry order of access by @code{in} operator
@cindex elements in arrays @subentry order of access by @code{in} operator
@cindex @code{in} operator @subentry order of array access
The order in which elements of the array are accessed by this statement
is determined by the internal arrangement of the array elements within
@command{awk} and in standard @command{awk} cannot be controlled
or changed. This can lead to problems if new elements are added to
@var{array} by statements in the loop body; it is not predictable whether
the @code{for} loop will reach them. Similarly, changing @var{var} inside
the loop may produce strange results. It is best to avoid such things.
As a point of information, @command{gawk} sets up the list of elements
to be iterated over before the loop starts, and does not change it.
But not all @command{awk} versions do so. Consider this program, named
@file{loopcheck.awk}:
@example
BEGIN @{
a["here"] = "here"
a["is"] = "is"
a["a"] = "a"
a["loop"] = "loop"
for (i in a) @{
j++
a[j] = j
print i
@}
@}
@end example
Here is what happens when run with @command{gawk} (and @command{mawk}):
@example
$ @kbd{gawk -f loopcheck.awk}
@print{} here
@print{} loop
@print{} a
@print{} is
@end example
Contrast this to BWK @command{awk}:
@example
$ @kbd{nawk -f loopcheck.awk}
@print{} loop
@print{} here
@print{} is
@print{} a
@print{} 1
@end example
@node Controlling Scanning
@subsection Using Predefined Array Scanning Orders with @command{gawk}
This @value{SUBSECTION} describes a feature that is specific to @command{gawk}.
By default, when a @code{for} loop traverses an array, the order
is undefined, meaning that the @command{awk} implementation
determines the order in which the array is traversed.
This order is usually based on the internal implementation of arrays
and will vary from one version of @command{awk} to the next.
@cindex array scanning order, controlling
@cindex controlling array scanning order
Often, though, you may wish to do something simple, such as
``traverse the array by comparing the indices in ascending order,''
or ``traverse the array by comparing the values in descending order.''
@command{gawk} provides two mechanisms that give you this control:
@itemize @value{BULLET}
@item
Set @code{PROCINFO["sorted_in"]} to one of a set of predefined values.
We describe this now.
@item
Set @code{PROCINFO["sorted_in"]} to the name of a user-defined function
to use for comparison of array elements. This advanced feature
is described later in @ref{Array Sorting}.
@end itemize
@cindex @code{PROCINFO} array @subentry values of @code{sorted_in}
The following special values for @code{PROCINFO["sorted_in"]} are available:
@table @code
@item "@@unsorted"
Array elements are processed in arbitrary order, which is the default
@command{awk} behavior.
@item "@@ind_str_asc"
Order by indices in ascending order compared as strings; this is the most basic sort.
(Internally, array indices are always strings, so with @samp{a[2*5] = 1}
the index is @code{"10"} rather than numeric 10.)
@item "@@ind_num_asc"
Order by indices in ascending order but force them to be treated as numbers in the process.
Any index with a non-numeric value will end up positioned as if it were zero.
@item "@@val_type_asc"
Order by element values in ascending order (rather than by indices).
Ordering is by the type assigned to the element
(@pxref{Typing and Comparison}).
All numeric values come before all string values,
which in turn come before all subarrays.
(Subarrays have not been described yet;
@pxref{Arrays of Arrays}.)
If you choose to use this feature in traversing @code{FUNCTAB}
(@pxref{Auto-set}), then the order is built-in functions first
(@pxref{Built-in}), then user-defined functions (@pxref{User-defined})
next, and finally functions loaded from an extension
(@pxref{Dynamic Extensions}).
@item "@@val_str_asc"
Order by element values in ascending order (rather than by indices). Scalar values are
compared as strings.
If the string values are identical,
the index string values are compared instead.
When comparing non-scalar values,
@code{"@@val_type_asc"} sort ordering is used, so subarrays, if present,
come out last.
@item "@@val_num_asc"
Order by element values in ascending order (rather than by indices). Scalar values are
compared as numbers.
Non-scalar values are compared using @code{"@@val_type_asc"} sort ordering,
so subarrays, if present, come out last.
When numeric values are equal, the string values are used to provide
an ordering: this guarantees consistent results across different
versions of the C @code{qsort()} function,@footnote{When two elements
compare as equal, the C @code{qsort()} function does not guarantee
that they will maintain their original relative order after sorting.
Using the string value to provide a unique ordering when the numeric
values are equal ensures that @command{gawk} behaves consistently
across different environments.} which @command{gawk} uses internally
to perform the sorting.
If the string values are also identical,
the index string values are compared instead.
@item "@@ind_str_desc"
Like @code{"@@ind_str_asc"}, but the
string indices are ordered from high to low.
@item "@@ind_num_desc"
Like @code{"@@ind_num_asc"}, but the
numeric indices are ordered from high to low.
@item "@@val_type_desc"
Like @code{"@@val_type_asc"}, but the
element values, based on type, are ordered from high to low.
Subarrays, if present, come out first.
@item "@@val_str_desc"
Like @code{"@@val_str_asc"}, but the
element values, treated as strings, are ordered from high to low.
If the string values are identical,
the index string values are compared instead.
When comparing non-scalar values,
@code{"@@val_type_desc"} sort ordering is used, so subarrays, if present,
come out first.
@item "@@val_num_desc"
Like @code{"@@val_num_asc"}, but the
element values, treated as numbers, are ordered from high to low.
If the numeric values are equal, the string values are compared instead.
If they are also identical, the index string values are compared instead.
Non-scalar values are compared using @code{"@@val_type_desc"} sort ordering,
so subarrays, if present, come out first.
@end table
The array traversal order is determined before the @code{for} loop
starts to run. Changing @code{PROCINFO["sorted_in"]} in the loop body
does not affect the loop.
For example:
@example
$ @kbd{gawk '}
> @kbd{BEGIN @{}
> @kbd{ a[4] = 4}
> @kbd{ a[3] = 3}
> @kbd{ for (i in a)}
> @kbd{ print i, a[i]}
> @kbd{@}'}
@print{} 4 4
@print{} 3 3
$ @kbd{gawk '}
> @kbd{BEGIN @{}
> @kbd{ PROCINFO["sorted_in"] = "@@ind_str_asc"}
> @kbd{ a[4] = 4}
> @kbd{ a[3] = 3}
> @kbd{ for (i in a)}
> @kbd{ print i, a[i]}
> @kbd{@}'}
@print{} 3 3
@print{} 4 4
@end example
When sorting an array by element values, if a value happens to be
a subarray then it is considered to be greater than any string or
numeric value, regardless of what the subarray itself contains,
and all subarrays are treated as being equal to each other. Their
order relative to each other is determined by their index strings.
Here are some additional things to bear in mind about sorted
array traversal:
@itemize @value{BULLET}
@item
The value of @code{PROCINFO["sorted_in"]} is global. That is, it affects
all array traversal @code{for} loops. If you need to change it within your
own code, you should see if it's defined and save and restore the value:
@example
@dots{}
if ("sorted_in" in PROCINFO) @{
save_sorted = PROCINFO["sorted_in"]
PROCINFO["sorted_in"] = "@@val_str_desc" # or whatever
@}
@dots{}
if (save_sorted)
PROCINFO["sorted_in"] = save_sorted
@end example
@item
As already mentioned, the default array traversal order is represented by
@code{"@@unsorted"}. You can also get the default behavior by assigning
the null string to @code{PROCINFO["sorted_in"]} or by just deleting the
@code{"sorted_in"} element from the @code{PROCINFO} array with
the @code{delete} statement.
(The @code{delete} statement hasn't been described yet; @pxref{Delete}.)
@end itemize
In addition, @command{gawk} provides built-in functions for
sorting arrays; see @ref{Array Sorting Functions}.
@node Numeric Array Subscripts
@section Using Numbers to Subscript Arrays
@cindex numbers @subentry as array subscripts
@cindex array subscripts @subentry numbers as
@cindex arrays @subentry numeric subscripts
@cindex subscripts in arrays @subentry numbers as
@cindex @code{CONVFMT} variable @subentry array subscripts and
An important aspect to remember about arrays is that @emph{array subscripts
are always strings}. When a numeric value is used as a subscript,
it is converted to a string value before being used for subscripting
(@pxref{Conversion}).
This means that the value of the predefined variable @code{CONVFMT} can
affect how your program accesses elements of an array. For example:
@example
xyz = 12.153
data[xyz] = 1
CONVFMT = "%2.2f"
if (xyz in data)
printf "%s is in data\n", xyz
else
printf "%s is not in data\n", xyz
@end example
@noindent
This prints @samp{12.15 is not in data}. The first statement gives
@code{xyz} a numeric value. Assigning to
@code{data[xyz]} subscripts @code{data} with the string value @code{"12.153"}
(using the default conversion value of @code{CONVFMT}, @code{"%.6g"}).
Thus, the array element @code{data["12.153"]} is assigned the value one.
The program then changes
the value of @code{CONVFMT}. The test @samp{(xyz in data)} generates a new
string value from @code{xyz}---this time @code{"12.15"}---because the value of
@code{CONVFMT} only allows two significant digits. This test fails,
because @code{"12.15"} is different from @code{"12.153"}.
@cindex converting @subentry integer array subscripts to strings
@cindex integer array indices
According to the rules for conversions
(@pxref{Conversion}), integer
values always convert to strings as integers, no matter what the
value of @code{CONVFMT} may happen to be. So the usual case of
the following works:
@example
for (i = 1; i <= maxsub; i++)
@ii{do something with} array[i]
@end example
The ``integer values always convert to strings as integers'' rule
has an additional consequence for array indexing.
Octal and hexadecimal constants
@ifnotdocbook
(@pxref{Nondecimal-numbers})
@end ifnotdocbook
@ifdocbook
(covered in @ref{Nondecimal-numbers})
@end ifdocbook
are converted internally into numbers, and their original form
is forgotten. This means, for example, that @code{array[17]},
@code{array[021]}, and @code{array[0x11]} all refer to the same element!
As with many things in @command{awk}, the majority of the time
things work as you would expect them to. But it is useful to have a precise
knowledge of the actual rules, as they can sometimes have a subtle
effect on your programs.
@node Uninitialized Subscripts
@section Using Uninitialized Variables as Subscripts
@cindex variables @subentry uninitialized, as array subscripts
@cindex uninitialized variables, as array subscripts
@cindex subscripts in arrays @subentry uninitialized variables as
@cindex arrays @subentry subscripts, uninitialized variables as
Suppose it's necessary to write a program
to print the input data in reverse order.
A reasonable attempt to do so (with some test
data) might look like this:
@example
$ @kbd{echo 'line 1}
> @kbd{line 2}
> @kbd{line 3' | awk '@{ l[lines] = $0; ++lines @}}
> @kbd{END @{}
> @kbd{for (i = lines - 1; i >= 0; i--)}
> @kbd{print l[i]}
> @kbd{@}'}
@print{} line 3
@print{} line 2
@end example
Unfortunately, the very first line of input data did not appear in the
output!
Upon first glance, we would think that this program should have worked.
The variable @code{lines}
is uninitialized, and uninitialized variables have the numeric value zero.
So, @command{awk} should have printed the value of @code{l[0]}.
The issue here is that subscripts for @command{awk} arrays are @emph{always}
strings. Uninitialized variables, when used as strings, have the
value @code{""}, not zero. Thus, @samp{line 1} ends up stored in
@code{l[""]}.
The following version of the program works correctly:
@example
@{ l[lines++] = $0 @}
END @{
for (i = lines - 1; i >= 0; i--)
print l[i]
@}
@end example
Here, the @samp{++} forces @code{lines} to be numeric, thus making
the ``old value'' numeric zero. This is then converted to @code{"0"}
as the array subscript.
@cindex array subscripts @subentry null string as
@cindex null strings @subentry as array subscripts
@cindex dark corner @subentry array subscripts
@cindex lint checking @subentry array subscripts
Even though it is somewhat unusual, the null string
(@code{""}) is a valid array subscript.
@value{DARKCORNER}
@command{gawk} warns about the use of the null string as a subscript
if @option{--lint} is provided
on the command line (@pxref{Options}).
@node Delete
@section The @code{delete} Statement
@cindex @code{delete} statement
@cindex deleting @subentry elements in arrays
@cindex arrays @subentry elements @subentry deleting
@cindex elements in arrays @subentry deleting
To remove an individual element of an array, use the @code{delete}
statement:
@example
delete @var{array}[@var{index-expression}]
@end example
Once an array element has been deleted, any value the element once
had is no longer available. It is as if the element had never
been referred to or been given a value.
The following is an example of deleting elements in an array:
@example
for (i in frequencies)
delete frequencies[i]
@end example
@noindent
This example removes all the elements from the array @code{frequencies}.
Once an element is deleted, a subsequent @code{for} statement to scan the array
does not report that element and using the @code{in} operator to check for
the presence of that element returns zero (i.e., false):
@example
delete foo[4]
if (4 in foo)
print "This will never be printed"
@end example
@cindex null strings @subentry deleting array elements and
It is important to note that deleting an element is @emph{not} the
same as assigning it a null value (the empty string, @code{""}).
For example:
@example
@group
foo[4] = ""
if (4 in foo)
print "This is printed, even though foo[4] is empty"
@end group
@end example
@cindex lint checking @subentry array subscripts
It is not an error to delete an element that does not exist.
However, if @option{--lint} is provided on the command line
(@pxref{Options}),
@command{gawk} issues a warning message when an element that
is not in the array is deleted.
@cindex common extensions @subentry @code{delete} to delete entire arrays
@cindex extensions @subentry common @subentry @code{delete} to delete entire arrays
@cindex arrays @subentry deleting entire contents
@cindex deleting @subentry entire arrays
@cindex @code{delete} @var{array}
@cindex differences in @command{awk} and @command{gawk} @subentry array elements, deleting
All the elements of an array may be deleted with a single statement
by leaving off the subscript in the @code{delete} statement,
as follows:
@example
delete @var{array}
@end example
Using this version of the @code{delete} statement is about three times
more efficient than the equivalent loop that deletes each element one
at a time.
This form of the @code{delete} statement is also supported
by BWK @command{awk} and @command{mawk}, as well as
by a number of other implementations.
@cindex Brian Kernighan's @command{awk}
@quotation NOTE
For many years, using @code{delete} without a subscript was a common
extension. In September 2012, it was accepted for inclusion into the
POSIX standard. See @uref{http://austingroupbugs.net/view.php?id=544,
the Austin Group website}.
@end quotation
@cindex portability @subentry deleting array elements
@cindex Brennan, Michael
The following statement provides a portable but nonobvious way to clear
out an array:@footnote{Thanks to Michael Brennan for pointing this out.}
@example
split("", array)
@end example
@cindex @code{split()} function @subentry array elements, deleting
The @code{split()} function
(@pxref{String Functions})
clears out the target array first. This call asks it to split
apart the null string. Because there is no data to split out, the
function simply clears the array and then returns.
@quotation CAUTION
Deleting all the elements from an array does not change its type; you cannot
clear an array and then use the array's name as a scalar
(i.e., a regular variable). For example, the following does not work:
@example
a[1] = 3
delete a
a = 3
@end example
@end quotation
@node Multidimensional
@section Multidimensional Arrays
@menu
* Multiscanning:: Scanning multidimensional arrays.
@end menu
@cindex subscripts in arrays @subentry multidimensional
@cindex arrays @subentry multidimensional
A @dfn{multidimensional array} is an array in which an element is identified
by a sequence of indices instead of a single index. For example, a
two-dimensional array requires two indices. The usual way (in many
languages, including @command{awk}) to refer to an element of a
two-dimensional array named @code{grid} is with
@code{grid[@var{x},@var{y}]}.
@cindex @code{SUBSEP} variable @subentry multidimensional arrays and
Multidimensional arrays are supported in @command{awk} through
concatenation of indices into one string.
@command{awk} converts the indices into strings
(@pxref{Conversion}) and
concatenates them together, with a separator between them. This creates
a single string that describes the values of the separate indices. The
combined string is used as a single index into an ordinary,
one-dimensional array. The separator used is the value of the built-in
variable @code{SUBSEP}.
For example, suppose we evaluate the expression @samp{foo[5,12] = "value"}
when the value of @code{SUBSEP} is @code{"@@"}. The numbers 5 and 12 are
converted to strings and
concatenated with an @samp{@@} between them, yielding @code{"5@@12"}; thus,
the array element @code{foo["5@@12"]} is set to @code{"value"}.
Once the element's value is stored, @command{awk} has no record of whether
it was stored with a single index or a sequence of indices. The two
expressions @samp{foo[5,12]} and @w{@samp{foo[5 SUBSEP 12]}} are always
equivalent.
The default value of @code{SUBSEP} is the string @code{"\034"},
which contains a nonprinting character that is unlikely to appear in an
@command{awk} program or in most input data.
The usefulness of choosing an unlikely character comes from the fact
that index values that contain a string matching @code{SUBSEP} can lead to
combined strings that are ambiguous. Suppose that @code{SUBSEP} is
@code{"@@"}; then @w{@samp{foo["a@@b", "c"]}} and @w{@samp{foo["a",
"b@@c"]}} are indistinguishable because both are actually
stored as @samp{foo["a@@b@@c"]}.
@cindex @code{in} operator @subentry index existence in multidimensional arrays
To test whether a particular index sequence exists in a
multidimensional array, use the same operator (@code{in}) that is
used for single-dimensional arrays. Write the whole sequence of indices
in parentheses, separated by commas, as the left operand:
@example
if ((@var{subscript1}, @var{subscript2}, @dots{}) in @var{array})
@dots{}
@end example
Here is an example that treats its input as a two-dimensional array of
fields; it rotates this array 90 degrees clockwise and prints the
result. It assumes that all lines have the same number of
elements:
@example
@{
if (max_nf < NF)
max_nf = NF
max_nr = NR
for (x = 1; x <= NF; x++)
vector[x, NR] = $x
@}
END @{
for (x = 1; x <= max_nf; x++) @{
for (y = max_nr; y >= 1; --y)
printf("%s ", vector[x, y])
printf("\n")
@}
@}
@end example
@noindent
When given the input:
@example
@group
1 2 3 4 5 6
2 3 4 5 6 1
3 4 5 6 1 2
4 5 6 1 2 3
@end group
@end example
@noindent
the program produces the following output:
@example
@group
4 3 2 1
5 4 3 2
6 5 4 3
1 6 5 4
2 1 6 5
3 2 1 6
@end group
@end example
@node Multiscanning
@subsection Scanning Multidimensional Arrays
There is no special @code{for} statement for scanning a
``multidimensional'' array. There cannot be one, because, in truth,
@command{awk} does not have
multidimensional arrays or elements---there is only a
multidimensional @emph{way of accessing} an array.
@cindex subscripts in arrays @subentry multidimensional @subentry scanning
@cindex arrays @subentry multidimensional @subentry scanning
@cindex scanning multidimensional arrays
However, if your program has an array that is always accessed as
multidimensional, you can get the effect of scanning it by combining
the scanning @code{for} statement
(@pxref{Scanning an Array}) with the
built-in @code{split()} function
(@pxref{String Functions}).
It works in the following manner:
@example
for (combined in array) @{
split(combined, separate, SUBSEP)
@dots{}
@}
@end example
@noindent
This sets the variable @code{combined} to
each concatenated combined index in the array, and splits it
into the individual indices by breaking it apart where the value of
@code{SUBSEP} appears. The individual indices then become the elements of
the array @code{separate}.
Thus, if a value is previously stored in @code{array[1, "foo"]}, then
an element with index @code{"1\034foo"} exists in @code{array}. (Recall
that the default value of @code{SUBSEP} is the character with code 034.)
Sooner or later, the @code{for} statement finds that index and does an
iteration with the variable @code{combined} set to @code{"1\034foo"}.
Then the @code{split()} function is called as follows:
@example
split("1\034foo", separate, "\034")
@end example
@noindent
The result is to set @code{separate[1]} to @code{"1"} and
@code{separate[2]} to @code{"foo"}. Presto! The original sequence of
separate indices is recovered.
@node Arrays of Arrays
@section Arrays of Arrays
@cindex arrays @subentry arrays of arrays
@command{gawk} goes beyond standard @command{awk}'s multidimensional
array access and provides true arrays of
arrays. Elements of a subarray are referred to by their own indices
enclosed in square brackets, just like the elements of the main array.
For example, the following creates a two-element subarray at index @code{1}
of the main array @code{a}:
@example
a[1][1] = 1
a[1][2] = 2
@end example
This simulates a true two-dimensional array. Each subarray element can
contain another subarray as a value, which in turn can hold other arrays
as well. In this way, you can create arrays of three or more dimensions.
The indices can be any @command{awk} expressions, including scalars
separated by commas (i.e., a regular @command{awk} simulated
multidimensional subscript). So the following is valid in
@command{gawk}:
@example
a[1][3][1, "name"] = "barney"
@end example
Each subarray and the main array can be of different length. In fact, the
elements of an array or its subarray do not all have to have the same
type. This means that the main array and any of its subarrays can be
nonrectangular, or jagged in structure. You can assign a scalar value to
the index @code{4} of the main array @code{a}, even though @code{a[1]}
is itself an array and not a scalar:
@example
a[4] = "An element in a jagged array"
@end example
The terms @dfn{dimension}, @dfn{row}, and @dfn{column} are
meaningless when applied
to such an array, but we will use ``dimension'' henceforth to imply the
maximum number of indices needed to refer to an existing element. The
type of any element that has already been assigned cannot be changed
by assigning a value of a different type. You have to first delete the
current element, which effectively makes @command{gawk} forget about
the element at that index:
@example
delete a[4]
a[4][5][6][7] = "An element in a four-dimensional array"
@end example
@noindent
This removes the scalar value from index @code{4} and then inserts a
three-level nested subarray
containing a scalar. You can also
delete an entire subarray or subarray of subarrays:
@example
delete a[4][5]
a[4][5] = "An element in subarray a[4]"
@end example
But recall that you can not delete the main array @code{a} and then use it
as a scalar.
The built-in functions that take array arguments can also be used
with subarrays. For example, the following code fragment uses @code{length()}
(@pxref{String Functions})
to determine the number of elements in the main array @code{a} and
its subarrays:
@example
print length(a), length(a[1]), length(a[1][3])
@end example
@noindent
This results in the following output for our main array @code{a}:
@example
2, 3, 1
@end example
@noindent
The @samp{@var{subscript} in @var{array}} expression
(@pxref{Reference to Elements}) works similarly for both
regular @command{awk}-style
arrays and arrays of arrays. For example, the tests @samp{1 in a},
@samp{3 in a[1]}, and @samp{(1, "name") in a[1][3]} all evaluate to
one (true) for our array @code{a}.
The @samp{for (item in array)} statement (@pxref{Scanning an Array})
can be nested to scan all the
elements of an array of arrays if it is rectangular in structure. In order
to print the contents (scalar values) of a two-dimensional array of arrays
(i.e., in which each first-level element is itself an
array, not necessarily of the same length),
you could use the following code:
@example
for (i in array)
for (j in array[i])
print array[i][j]
@end example
The @code{isarray()} function (@pxref{Type Functions})
lets you test if an array element is itself an array:
@example
for (i in array) @{
if (isarray(array[i])) @{
for (j in array[i]) @{
print array[i][j]
@}
@}
else
print array[i]
@}
@end example
If the structure of a jagged array of arrays is known in advance,
you can often devise workarounds using control statements. For example,
the following code prints the elements of our main array @code{a}:
@example
@group
for (i in a) @{
for (j in a[i]) @{
if (j == 3) @{
for (k in a[i][j])
print a[i][j][k]
@end group
@group
@} else
print a[i][j]
@}
@}
@end group
@end example
@noindent
@xref{Walking Arrays} for a user-defined function that ``walks'' an
arbitrarily dimensioned array of arrays.
Recall that a reference to an uninitialized array element yields a value
of @code{""}, the null string. This has one important implication when you
intend to use a subarray as an argument to a function, as illustrated by
the following example:
@example
$ @kbd{gawk 'BEGIN @{ split("a b c d", b[1]); print b[1][1] @}'}
@error{} gawk: cmd. line:1: fatal: split: second argument is not an array
@end example
The way to work around this is to first force @code{b[1]} to be an array by
creating an arbitrary index:
@example
$ @kbd{gawk 'BEGIN @{ b[1][1] = ""; split("a b c d", b[1]); print b[1][1] @}'}
@print{} a
@end example
@node Arrays Summary
@section Summary
@itemize @value{BULLET}
@item
Standard @command{awk} provides one-dimensional associative arrays
(arrays indexed by string values). All arrays are associative; numeric
indices are converted automatically to strings.
@item
Array elements are referenced as @code{@var{array}[@var{indx}]}.
Referencing an element creates it if it did not exist previously.
@item
The proper way to see if an array has an element with a given index
is to use the @code{in} operator: @samp{@var{indx} in @var{array}}.
@item
Use @samp{for (@var{indx} in @var{array}) @dots{}} to scan through all the
individual elements of an array. In the body of the loop, @var{indx} takes
on the value of each element's index in turn.
@item
The order in which a @samp{for (@var{indx} in @var{array})} loop
traverses an array is undefined in POSIX @command{awk} and varies among
implementations. @command{gawk} lets you control the order by assigning
special predefined values to @code{PROCINFO["sorted_in"]}.
@item
Use @samp{delete @var{array}[@var{indx}]} to delete an individual element.
To delete all of the elements in an array,
use @samp{delete @var{array}}.
This latter feature has been a common extension for many
years and is now standard, but may not be supported by all commercial
versions of @command{awk}.
@item
Standard @command{awk} simulates multidimensional arrays by separating
subscript values with commas. The values are concatenated into a
single string, separated by the value of @code{SUBSEP}. The fact
that such a subscript was created in this way is not retained; thus,
changing @code{SUBSEP} may have unexpected consequences. You can use
@samp{(@var{sub1}, @var{sub2}, @dots{}) in @var{array}} to see if such
a multidimensional subscript exists in @var{array}.
@item
@command{gawk} provides true arrays of arrays. You use a separate
set of square brackets for each dimension in such an array:
@code{data[row][col]}, for example. Array elements may thus be either
scalar values (number or string) or other arrays.
@item
Use the @code{isarray()} built-in function to determine if an array
element is itself a subarray.
@end itemize
@node Functions
@chapter Functions
@cindex functions @subentry built-in
@cindex built-in functions
This @value{CHAPTER} describes @command{awk}'s built-in functions,
which fall into three categories: numeric, string, and I/O.
@command{gawk} provides additional groups of functions
to work with values that represent time, do
bit manipulation, sort arrays,
provide type information, and internationalize and localize programs.
Besides the built-in functions, @command{awk} has provisions for
writing new functions that the rest of a program can use.
The second half of this @value{CHAPTER} describes these
@dfn{user-defined} functions.
Finally, we explore indirect function calls, a @command{gawk}-specific
extension that lets you determine at runtime what function is to
be called.
@menu
* Built-in:: Summarizes the built-in functions.
* User-defined:: Describes User-defined functions in detail.
* Indirect Calls:: Choosing the function to call at runtime.
* Functions Summary:: Summary of functions.
@end menu
@node Built-in
@section Built-in Functions
@dfn{Built-in} functions are always available for your @command{awk}
program to call. This @value{SECTION} defines all the built-in functions
in @command{awk}; some of these are mentioned in other @value{SECTION}s
but are summarized here for your convenience.
@menu
* Calling Built-in:: How to call built-in functions.
* Numeric Functions:: Functions that work with numbers, including
@code{int()}, @code{sin()} and @code{rand()}.
* String Functions:: Functions for string manipulation, such as
@code{split()}, @code{match()} and
@code{sprintf()}.
* I/O Functions:: Functions for files and shell commands.
* Time Functions:: Functions for dealing with timestamps.
* Bitwise Functions:: Functions for bitwise operations.
* Type Functions:: Functions for type information.
* I18N Functions:: Functions for string translation.
@end menu
@node Calling Built-in
@subsection Calling Built-in Functions
To call one of @command{awk}'s built-in functions, write the name of
the function followed
by arguments in parentheses. For example, @samp{atan2(y + z, 1)}
is a call to the function @code{atan2()} and has two arguments.
@cindex programming conventions @subentry functions @subentry calling
@cindex whitespace @subentry functions, calling
Whitespace is ignored between the built-in function name and the
opening parenthesis, but nonetheless it is good practice to avoid using whitespace
there. User-defined functions do not permit whitespace in this way, and
it is easier to avoid mistakes by following a simple
convention that always works---no whitespace after a function name.
@cindex troubleshooting @subentry @command{gawk} @subentry fatal errors, function arguments
@cindex @command{gawk} @subentry function arguments and
@cindex differences in @command{awk} and @command{gawk} @subentry function arguments
Each built-in function accepts a certain number of arguments.
In some cases, arguments can be omitted. The defaults for omitted
arguments vary from function to function and are described under the
individual functions. In some @command{awk} implementations, extra
arguments given to built-in functions are ignored. However, in @command{gawk},
it is a fatal error to give extra arguments to a built-in function.
When a function is called, expressions that create the function's actual
parameters are evaluated completely before the call is performed.
For example, in the following code fragment:
@example
i = 4
j = sqrt(i++)
@end example
@cindex evaluation order @subentry functions
@cindex functions @subentry built-in @subentry evaluation order
@cindex built-in functions @subentry evaluation order
@noindent
the variable @code{i} is incremented to the value five before @code{sqrt()}
is called with a value of four for its actual parameter.
The order of evaluation of the expressions used for the function's
parameters is undefined. Thus, avoid writing programs that
assume that parameters are evaluated from left to right or from
right to left. For example:
@example
i = 5
j = atan2(++i, i *= 2)
@end example
If the order of evaluation is left to right, then @code{i} first becomes
six, and then 12, and @code{atan2()} is called with the two arguments six
and 12. But if the order of evaluation is right to left, @code{i}
first becomes 10, then 11, and @code{atan2()} is called with the
two arguments 11 and 10.
@node Numeric Functions
@subsection Numeric Functions
@cindex numeric @subentry functions
The following list describes all of
the built-in functions that work with numbers.
Optional parameters are enclosed in square brackets@w{ ([ ]):}
@c @asis for docbook
@table @asis
@item @code{atan2(@var{y}, @var{x})}
@cindexawkfunc{atan2}
@cindex arctangent
Return the arctangent of @code{@var{y} / @var{x}} in radians.
You can use @samp{pi = atan2(0, -1)} to retrieve the value of
@value{PI}.
@item @code{cos(@var{x})}
@cindexawkfunc{cos}
@cindex cosine
Return the cosine of @var{x}, with @var{x} in radians.
@item @code{exp(@var{x})}
@cindexawkfunc{exp}
@cindex exponent
Return the exponential of @var{x} (@code{e ^ @var{x}}) or report
an error if @var{x} is out of range. The range of values @var{x} can have
depends on your machine's floating-point representation.
@item @code{int(@var{x})}
@cindexawkfunc{int}
@cindex round to nearest integer
Return the nearest integer to @var{x}, located between @var{x} and zero and
truncated toward zero.
For example, @code{int(3)} is 3, @code{int(3.9)} is 3, @code{int(-3.9)}
is @minus{}3, and @code{int(-3)} is @minus{}3 as well.
@ifset INTDIV
@item @code{intdiv0(@var{numerator}, @var{denominator}, @var{result})}
@cindexawkfunc{intdiv0}
@cindex intdiv0
Perform integer division, similar to the standard C @code{div()} function.
First, truncate @code{numerator} and @code{denominator}
towards zero, creating integer values. Clear the @code{result}
array, and then set @code{result["quotient"]} to the result of
@samp{numerator / denominator}, truncated towards zero to an integer,
and set @code{result["remainder"]} to the result of @samp{numerator %
denominator}, truncated towards zero to an integer.
Attempting division by zero causes a fatal error.
The function returns zero upon success, and @minus{}1 upon error.
This function is
primarily intended for use with arbitrary length integers; it avoids
creating MPFR arbitrary precision floating-point values (@pxref{Arbitrary
Precision Integers}).
This function is a @code{gawk} extension. It is not available in
compatibility mode (@pxref{Options}).
@end ifset
@item @code{log(@var{x})}
@cindexawkfunc{log}
@cindex logarithm
Return the natural logarithm of @var{x}, if @var{x} is positive;
otherwise, return @code{NaN} (``not a number'') on IEEE 754 systems.
Additionally, @command{gawk} prints a warning message when @code{x}
is negative.
@cindex Beebe, Nelson H.F.@:
@item @code{rand()}
@cindexawkfunc{rand}
@cindex random numbers @subentry @code{rand()}/@code{srand()} functions
Return a random number. The values of @code{rand()} are
uniformly distributed between zero and one.
The value could be zero but is never one.@footnote{The C version of
@code{rand()} on many Unix systems is known to produce fairly poor
sequences of random numbers. However, nothing requires that an
@command{awk} implementation use the C @code{rand()} to implement the
@command{awk} version of @code{rand()}. In fact, for many years,
@command{gawk} used the BSD @code{random()} function, which is
considerably better than @code{rand()}, to produce random numbers.
From @value{PVERSION} 4.1.4, courtesy of Nelson H.F.@: Beebe, @command{gawk}
uses the Bayes-Durham shuffle buffer algorithm which considerably extends
the period of the random number generator, and eliminates short-range and
long-range correlations that might exist in the original generator.}
Often random integers are needed instead. Following is a user-defined function
that can be used to obtain a random nonnegative integer less than @var{n}:
@example
function randint(n)
@{
return int(n * rand())
@}
@end example
@noindent
The multiplication produces a random number greater than or equal to
zero and less than @code{n}. Using @code{int()}, this result is made into
an integer between zero and @code{n} @minus{} 1, inclusive.
The following example uses a similar function to produce random integers
between one and @var{n}. This program prints a new random number for
each input record:
@example
# Function to roll a simulated die.
function roll(n) @{ return 1 + int(rand() * n) @}
# Roll 3 six-sided dice and
# print total number of points.
@{
printf("%d points\n", roll(6) + roll(6) + roll(6))
@}
@end example
@cindex seeding random number generator
@cindex random numbers @subentry seed of
@quotation CAUTION
In most @command{awk} implementations, including @command{gawk},
@code{rand()} starts generating numbers from the same
starting number, or @dfn{seed}, each time you run @command{awk}.@footnote{@command{mawk}
uses a different seed each time.} Thus,
a program generates the same results each time you run it.
The numbers are random within one @command{awk} run but predictable
from run to run. This is convenient for debugging, but if you want
a program to do different things each time it is used, you must change
the seed to a value that is different in each run. To do this,
use @code{srand()}.
@end quotation
@item @code{sin(@var{x})}
@cindexawkfunc{sin}
@cindex sine
Return the sine of @var{x}, with @var{x} in radians.
@item @code{sqrt(@var{x})}
@cindexawkfunc{sqrt}
@cindex square root
Return the positive square root of @var{x}.
@command{gawk} prints a warning message
if @var{x} is negative. Thus, @code{sqrt(4)} is 2.
@item @code{srand(}[@var{x}]@code{)}
@cindexawkfunc{srand}
Set the starting point, or seed,
for generating random numbers to the value @var{x}.
Each seed value leads to a particular sequence of random
numbers.@footnote{Computer-generated random numbers really are not truly
random. They are technically known as @dfn{pseudorandom}. This means
that although the numbers in a sequence appear to be random, you can in
fact generate the same sequence of random numbers over and over again.}
Thus, if the seed is set to the same value a second time,
the same sequence of random numbers is produced again.
@quotation CAUTION
Different @command{awk} implementations use different random-number
generators internally. Don't expect the same @command{awk} program
to produce the same series of random numbers when executed by
different versions of @command{awk}.
@end quotation
If the argument @var{x} is omitted, as in @samp{srand()}, then the current
date and time of day are used for a seed. This is the way to get random
numbers that are truly unpredictable.
The return value of @code{srand()} is the previous seed. This makes it
easy to keep track of the seeds in case you need to consistently reproduce
sequences of random numbers.
POSIX does not specify the initial seed; it differs among @command{awk}
implementations.
@end table
@node String Functions
@subsection String-Manipulation Functions
@cindex string-manipulation functions
The functions in this @value{SECTION} look at or change the text of one
or more strings.
@command{gawk} understands locales (@pxref{Locales}) and does all
string processing in terms of @emph{characters}, not @emph{bytes}.
This distinction is particularly important to understand for locales
where one character may be represented by multiple bytes. Thus, for
example, @code{length()} returns the number of characters in a string,
and not the number of bytes used to represent those characters. Similarly,
@code{index()} works with character indices, and not byte indices.
@quotation CAUTION
A number of functions deal with indices into strings. For these
functions, the first character of a string is at position (index) one.
This is different from C and the languages descended from it, where the
first character is at position zero. You need to remember this when
doing index calculations, particularly if you are used to C.
@end quotation
In the following list, optional parameters are enclosed in square brackets@w{ ([ ]).}
Several functions perform string substitution; the full discussion is
provided in the description of the @code{sub()} function, which comes
toward the end, because the list is presented alphabetically.
Those functions that are specific to @command{gawk} are marked with a
pound sign (@samp{#}). They are not available in compatibility mode
(@pxref{Options}):
@menu
* Gory Details:: More than you want to know about @samp{\} and
@samp{&} with @code{sub()}, @code{gsub()}, and
@code{gensub()}.
@end menu
@c @asis for docbook
@table @asis
@item @code{asort(}@var{source} [@code{,} @var{dest} [@code{,} @var{how} ] ]@code{) #}
@itemx @code{asorti(}@var{source} [@code{,} @var{dest} [@code{,} @var{how} ] ]@code{) #}
@cindexgawkfunc{asorti}
@cindex sort array
@cindex arrays @subentry elements @subentry retrieving number of
@cindexgawkfunc{asort}
@cindex sort array indices
These two functions are similar in behavior, so they are described
together.
@quotation NOTE
The following description ignores the third argument, @var{how}, as it
requires understanding features that we have not discussed yet. Thus,
the discussion here is a deliberate simplification. (We do provide all
the details later on; see @ref{Array Sorting Functions} for the full story.)
@end quotation
Both functions return the number of elements in the array @var{source}.
For @command{asort()}, @command{gawk} sorts the values of @var{source}
and replaces the indices of the sorted values of @var{source} with
sequential integers starting with one. If the optional array @var{dest}
is specified, then @var{source} is duplicated into @var{dest}. @var{dest}
is then sorted, leaving the indices of @var{source} unchanged.
@cindex @command{gawk} @subentry @code{IGNORECASE} variable in
When comparing strings, @code{IGNORECASE} affects the sorting
(@pxref{Array Sorting Functions}). If the
@var{source} array contains subarrays as values (@pxref{Arrays of
Arrays}), they will come last, after all scalar values.
Subarrays are @emph{not} recursively sorted.
For example, if the contents of @code{a} are as follows:
@example
a["last"] = "de"
a["first"] = "sac"
a["middle"] = "cul"
@end example
@noindent
A call to @code{asort()}:
@example
asort(a)
@end example
@noindent
results in the following contents of @code{a}:
@example
@group
a[1] = "cul"
a[2] = "de"
a[3] = "sac"
@end group
@end example
The @code{asorti()} function works similarly to @code{asort()}; however,
the @emph{indices} are sorted, instead of the values. Thus, in the
previous example, starting with the same initial set of indices and
values in @code{a}, calling @samp{asorti(a)} would yield:
@example
a[1] = "first"
a[2] = "last"
a[3] = "middle"
@end example
@quotation NOTE
Due to implementation limitations, you may not use either @code{SYMTAB}
or @code{FUNCTAB} as arguments to these functions, even if providing a
second array to use for the actual sorting. Attempting to do so produces
a fatal error. This restriction may be lifted in the future.
@end quotation
@item @code{gensub(@var{regexp}, @var{replacement}, @var{how}} [@code{, @var{target}}]@code{) #}
@cindexgawkfunc{gensub}
@cindex search and replace in strings
@cindex substitute in string
Search the target string @var{target} for matches of the regular
expression @var{regexp}. If @var{how} is a string beginning with
@samp{g} or @samp{G} (short for ``global''), then replace all matches
of @var{regexp} with @var{replacement}. Otherwise, treat @var{how}
as a number indicating which match of @var{regexp} to replace. Treat
numeric values less than one as if they were one. If no @var{target}
is supplied, use @code{$0}. Return the modified string as the result
of the function. The original target string is @emph{not} changed.
@code{gensub()} is a general substitution function. Its purpose is
to provide more features than the standard @code{sub()} and @code{gsub()}
functions.
@code{gensub()} provides an additional feature that is not available
in @code{sub()} or @code{gsub()}: the ability to specify components of a
regexp in the replacement text. This is done by using parentheses in
the regexp to mark the components and then specifying @samp{\@var{N}}
in the replacement text, where @var{N} is a digit from 1 to 9.
For example:
@example
$ @kbd{gawk '}
> @kbd{BEGIN @{}
> @kbd{a = "abc def"}
> @kbd{b = gensub(/(.+) (.+)/, "\\2 \\1", "g", a)}
> @kbd{print b}
> @kbd{@}'}
@print{} def abc
@end example
@noindent
As with @code{sub()}, you must type two backslashes in order
to get one into the string.
In the replacement text, the sequence @samp{\0} represents the entire
matched text, as does the character @samp{&}.
The following example shows how you can use the third argument to control
which match of the regexp should be changed:
@example
$ @kbd{echo a b c a b c |}
> @kbd{gawk '@{ print gensub(/a/, "AA", 2) @}'}
@print{} a b c AA b c
@end example
In this case, @code{$0} is the default target string.
@code{gensub()} returns the new string as its result, which is
passed directly to @code{print} for printing.
@c @cindex automatic warnings
@c @cindex warnings, automatic
If the @var{how} argument is a string that does not begin with @samp{g} or
@samp{G}, or if it is a number that is less than or equal to zero, only one
substitution is performed. If @var{how} is zero, @command{gawk} issues
a warning message.
If @var{regexp} does not match @var{target}, @code{gensub()}'s return value
is the original unchanged value of @var{target}.
@item @code{gsub(@var{regexp}, @var{replacement}} [@code{, @var{target}}]@code{)}
@cindexawkfunc{gsub}
Search @var{target} for
@emph{all} of the longest, leftmost, @emph{nonoverlapping} matching
substrings it can find and replace them with @var{replacement}.
The @samp{g} in @code{gsub()} stands for
``global,'' which means replace everywhere. For example:
@example
@{ gsub(/Britain/, "United Kingdom"); print @}
@end example
@noindent
replaces all occurrences of the string @samp{Britain} with @samp{United
Kingdom} for all input records.
The @code{gsub()} function returns the number of substitutions made. If
the variable to search and alter (@var{target}) is
omitted, then the entire input record (@code{$0}) is used.
As in @code{sub()}, the characters @samp{&} and @samp{\} are special,
and the third argument must be assignable.
@item @code{index(@var{in}, @var{find})}
@cindexawkfunc{index}
@cindex search for substring
@cindex find substring in string
Search the string @var{in} for the first occurrence of the string
@var{find}, and return the position in characters where that occurrence
begins in the string @var{in}. Consider the following example:
@example
$ @kbd{awk 'BEGIN @{ print index("peanut", "an") @}'}
@print{} 3
@end example
@noindent
If @var{find} is not found, @code{index()} returns zero.
@cindex dark corner @subentry regexp as second argument to @code{index()}
With BWK @command{awk} and @command{gawk},
it is a fatal error to use a regexp constant for @var{find}.
Other implementations allow it, simply treating the regexp
constant as an expression meaning @samp{$0 ~ /regexp/}. @value{DARKCORNER}
@item @code{length(}[@var{string}]@code{)}
@cindexawkfunc{length}
@cindex string @subentry length
@cindex length of string
Return the number of characters in @var{string}. If
@var{string} is a number, the length of the digit string representing
that number is returned. For example, @code{length("abcde")} is five. By
contrast, @code{length(15 * 35)} works out to three. In this example,
@iftex
@math{15 @cdot 35 = 525},
@end iftex
@ifnottex
@ifnotdocbook
15 * 35 = 525,
@end ifnotdocbook
@end ifnottex
@docbook
15 ⋅ 35 = 525,
@end docbook
and 525 is then converted to the string @code{"525"}, which has
three characters.
@cindex length of input record
@cindex input record, length of
If no argument is supplied, @code{length()} returns the length of @code{$0}.
@c @cindex historical features
@cindex portability @subentry @code{length()} function
@cindex POSIX @command{awk} @subentry functions and @subentry @code{length()}
@quotation NOTE
In older versions of @command{awk}, the @code{length()} function could
be called
without any parentheses. Doing so is considered poor practice,
although the 2008 POSIX standard explicitly allows it, to
support historical practice. For programs to be maximally portable,
always supply the parentheses.
@end quotation
@cindex dark corner @subentry @code{length()} function
If @code{length()} is called with a variable that has not been used,
@command{gawk} forces the variable to be a scalar. Other
implementations of @command{awk} leave the variable without a type.
@value{DARKCORNER}
Consider:
@example
$ @kbd{gawk 'BEGIN @{ print length(x) ; x[1] = 1 @}'}
@print{} 0
@error{} gawk: fatal: attempt to use scalar `x' as array
$ @kbd{nawk 'BEGIN @{ print length(x) ; x[1] = 1 @}'}
@print{} 0
@end example
@noindent
If @option{--lint} has
been specified on the command line, @command{gawk} issues a
warning about this.
@cindex common extensions @subentry @code{length()} applied to an array
@cindex extensions @subentry common @subentry @code{length()} applied to an array
@cindex differences in @command{awk} and @command{gawk} @subentry @code{length()} function
@cindex number of array elements
@cindex arrays @subentry number of elements
With @command{gawk} and several other @command{awk} implementations, when given an
array argument, the @code{length()} function returns the number of elements
in the array. @value{COMMONEXT}
This is less useful than it might seem at first, as the
array is not guaranteed to be indexed from one to the number of elements
in it.
If @option{--lint} is provided on the command line
(@pxref{Options}),
@command{gawk} warns that passing an array argument is not portable.
If @option{--posix} is supplied, using an array argument is a fatal error
(@pxref{Arrays}).
@item @code{match(@var{string}, @var{regexp}} [@code{, @var{array}}]@code{)}
@cindexawkfunc{match}
@cindex string @subentry regular expression match of
@cindex match regexp in string
Search @var{string} for the
longest, leftmost substring matched by the regular expression
@var{regexp} and return the character position (index)
at which that substring begins (one, if it starts at the beginning of
@var{string}). If no match is found, return zero.
The @var{regexp} argument may be either a regexp constant
(@code{/}@dots{}@code{/}) or a string constant (@code{"}@dots{}@code{"}).
In the latter case, the string is treated as a regexp to be matched.
@xref{Computed Regexps} for a
discussion of the difference between the two forms, and the
implications for writing your program correctly.
The order of the first two arguments is the opposite of most other string
functions that work with regular expressions, such as
@code{sub()} and @code{gsub()}. It might help to remember that
for @code{match()}, the order is the same as for the @samp{~} operator:
@samp{@var{string} ~ @var{regexp}}.
@cindex @code{RSTART} variable @subentry @code{match()} function and
@cindex @code{RLENGTH} variable @subentry @code{match()} function and
@cindex @code{match()} function @subentry @code{RSTART}/@code{RLENGTH} variables
@cindex @code{match()} function @subentry side effects
@cindex side effects @subentry @code{match()} function
The @code{match()} function sets the predefined variable @code{RSTART} to
the index. It also sets the predefined variable @code{RLENGTH} to the
length in characters of the matched substring. If no match is found,
@code{RSTART} is set to zero, and @code{RLENGTH} to @minus{}1.
For example:
@example
@c file eg/misc/findpat.awk
@{
if ($1 == "FIND")
regex = $2
else @{
where = match($0, regex)
if (where != 0)
print "Match of", regex, "found at", where, "in", $0
@}
@}
@c endfile
@end example
@noindent
This program looks for lines that match the regular expression stored in
the variable @code{regex}. This regular expression can be changed. If the
first word on a line is @samp{FIND}, @code{regex} is changed to be the
second word on that line. Therefore, if given:
@example
@c file eg/misc/findpat.data
FIND ru+n
My program runs
but not very quickly
FIND Melvin
JF+KM
This line is property of Reality Engineering Co.
Melvin was here.
@c endfile
@end example
@noindent
@command{awk} prints:
@example
Match of ru+n found at 12 in My program runs
Match of Melvin found at 1 in Melvin was here.
@end example
@cindex differences in @command{awk} and @command{gawk} @subentry @code{match()} function
If @var{array} is present, it is cleared, and then the zeroth element
of @var{array} is set to the entire portion of @var{string}
matched by @var{regexp}. If @var{regexp} contains parentheses,
the integer-indexed elements of @var{array} are set to contain the
portion of @var{string} matching the corresponding parenthesized
subexpression.
For example:
@example
$ @kbd{echo foooobazbarrrrr |}
> @kbd{gawk '@{ match($0, /(fo+).+(bar*)/, arr)}
> @kbd{print arr[1], arr[2] @}'}
@print{} foooo barrrrr
@end example
In addition,
multidimensional subscripts are available providing
the start index and length of each matched subexpression:
@example
$ @kbd{echo foooobazbarrrrr |}
> @kbd{gawk '@{ match($0, /(fo+).+(bar*)/, arr)}
> @kbd{print arr[1], arr[2]}
> @kbd{print arr[1, "start"], arr[1, "length"]}
> @kbd{print arr[2, "start"], arr[2, "length"]}
> @kbd{@}'}
@print{} foooo barrrrr
@print{} 1 5
@print{} 9 7
@end example
There may not be subscripts for the start and index for every parenthesized
subexpression, because they may not all have matched text; thus, they
should be tested for with the @code{in} operator
(@pxref{Reference to Elements}).
@cindex troubleshooting @subentry @code{match()} function
The @var{array} argument to @code{match()} is a
@command{gawk} extension. In compatibility mode
(@pxref{Options}),
using a third argument is a fatal error.
@item @code{patsplit(@var{string}, @var{array}} [@code{, @var{fieldpat}} [@code{, @var{seps}} ] ]@code{) #}
@cindexgawkfunc{patsplit}
@cindex split string into array
Divide
@var{string} into pieces (or ``fields'') defined by @var{fieldpat}
and store the pieces in @var{array} and the separator strings in the
@var{seps} array. The first piece is stored in
@code{@var{array}[1]}, the second piece in @code{@var{array}[2]}, and so
forth. The third argument, @var{fieldpat}, is
a regexp describing the fields in @var{string} (just as @code{FPAT} is
a regexp describing the fields in input records).
It may be either a regexp constant or a string.
If @var{fieldpat} is omitted, the value of @code{FPAT} is used.
@code{patsplit()} returns the number of elements created.
@code{@var{seps}[@var{i}]} is
the possibly null separator string
after @code{@var{array}[@var{i}]}.
The possibly null leading separator will be in @code{@var{seps}[0]}.
So a non-null @var{string} with @var{n} fields will have @var{n+1} separators.
A null @var{string} will not have neither fields nor separators.
The @code{patsplit()} function splits strings into pieces in a
manner similar to the way input lines are split into fields using @code{FPAT}
(@pxref{Splitting By Content}).
Before splitting the string, @code{patsplit()} deletes any previously existing
elements in the arrays @var{array} and @var{seps}.
@item @code{split(@var{string}, @var{array}} [@code{, @var{fieldsep}} [@code{, @var{seps}} ] ]@code{)}
@cindexawkfunc{split}
Divide @var{string} into pieces separated by @var{fieldsep}
and store the pieces in @var{array} and the separator strings in the
@var{seps} array. The first piece is stored in
@code{@var{array}[1]}, the second piece in @code{@var{array}[2]}, and so
forth. The string value of the third argument, @var{fieldsep}, is
a regexp describing where to split @var{string} (much as @code{FS} can
be a regexp describing where to split input records).
If @var{fieldsep} is omitted, the value of @code{FS} is used.
@code{split()} returns the number of elements created.
@var{seps} is a @command{gawk} extension, with @code{@var{seps}[@var{i}]}
being the separator string
between @code{@var{array}[@var{i}]} and @code{@var{array}[@var{i}+1]}.
If @var{fieldsep} is a single
space, then any leading whitespace goes into @code{@var{seps}[0]} and
any trailing
whitespace goes into @code{@var{seps}[@var{n}]}, where @var{n} is the
return value of
@code{split()} (i.e., the number of elements in @var{array}).
The @code{split()} function splits strings into pieces in the same way
that input lines are split into fields. For example:
@example
split("cul-de-sac", a, "-", seps)
@end example
@noindent
@cindex strings @subentry splitting, example
splits the string @code{"cul-de-sac"} into three fields using @samp{-} as the
separator. It sets the contents of the array @code{a} as follows:
@example
a[1] = "cul"
a[2] = "de"
a[3] = "sac"
@end example
and sets the contents of the array @code{seps} as follows:
@example
seps[1] = "-"
seps[2] = "-"
@end example
@noindent
The value returned by this call to @code{split()} is three.
@cindex differences in @command{awk} and @command{gawk} @subentry @code{split()} function
As with input field-splitting, when the value of @var{fieldsep} is
@w{@code{" "}}, leading and trailing whitespace is ignored in values assigned to
the elements of
@var{array} but not in @var{seps}, and the elements
are separated by runs of whitespace.
Also, as with input field splitting, if @var{fieldsep} is the null string, each
individual character in the string is split into its own array element.
@value{COMMONEXT}
Additionally, if @var{fieldsep} is a single-character string, that string acts
as the separator, even if its value is a regular expression metacharacter.
Note, however, that @code{RS} has no effect on the way @code{split()}
works. Even though @samp{RS = ""} causes the newline character to also be an input
field separator, this does not affect how @code{split()} splits strings.
@cindex dark corner @subentry @code{split()} function
Modern implementations of @command{awk}, including @command{gawk}, allow
the third argument to be a regexp constant (@w{@code{/}@dots{}@code{/}})
as well as a string. @value{DARKCORNER}
The POSIX standard allows this as well.
@xref{Computed Regexps} for a
discussion of the difference between using a string constant or a regexp constant,
and the implications for writing your program correctly.
Before splitting the string, @code{split()} deletes any previously existing
elements in the arrays @var{array} and @var{seps}.
If @var{string} is null, the array has no elements. (So this is a portable
way to delete an entire array with one statement.
@xref{Delete}.)
If @var{string} does not match @var{fieldsep} at all (but is not null),
@var{array} has one element only. The value of that element is the original
@var{string}.
@cindex POSIX mode
In POSIX mode (@pxref{Options}), the fourth argument is not allowed.
@item @code{sprintf(@var{format}, @var{expression1}, @dots{})}
@cindexawkfunc{sprintf}
@cindex formatting @subentry strings
Return (without printing) the string that @code{printf} would
have printed out with the same arguments
(@pxref{Printf}).
For example:
@example
pival = sprintf("pi = %.2f (approx.)", 22/7)
@end example
@noindent
assigns the string @w{@samp{pi = 3.14 (approx.)}} to the variable @code{pival}.
@cindexgawkfunc{strtonum}
@cindex converting @subentry string to numbers
@item @code{strtonum(@var{str}) #}
Examine @var{str} and return its numeric value. If @var{str}
begins with a leading @samp{0}, @code{strtonum()} assumes that @var{str}
is an octal number. If @var{str} begins with a leading @samp{0x} or
@samp{0X}, @code{strtonum()} assumes that @var{str} is a hexadecimal number.
For example:
@example
$ @kbd{echo 0x11 |}
> @kbd{gawk '@{ printf "%d\n", strtonum($1) @}'}
@print{} 17
@end example
Using the @code{strtonum()} function is @emph{not} the same as adding zero
to a string value; the automatic coercion of strings to numbers
works only for decimal data, not for octal or hexadecimal.@footnote{Unless
you use the @option{--non-decimal-data} option, which isn't recommended.
@xref{Nondecimal Data} for more information.}
Note also that @code{strtonum()} uses the current locale's decimal point
for recognizing numbers (@pxref{Locales}).
@item @code{sub(@var{regexp}, @var{replacement}} [@code{, @var{target}}]@code{)}
@cindexawkfunc{sub}
@cindex replace in string
Search @var{target}, which is treated as a string, for the
leftmost, longest substring matched by the regular expression @var{regexp}.
Modify the entire string
by replacing the matched text with @var{replacement}.
The modified string becomes the new value of @var{target}.
Return the number of substitutions made (zero or one).
The @var{regexp} argument may be either a regexp constant
(@code{/}@dots{}@code{/}) or a string constant (@code{"}@dots{}@code{"}).
In the latter case, the string is treated as a regexp to be matched.
@xref{Computed Regexps} for a
discussion of the difference between the two forms, and the
implications for writing your program correctly.
This function is peculiar because @var{target} is not simply
used to compute a value, and not just any expression will do---it
must be a variable, field, or array element so that @code{sub()} can
store a modified value there. If this argument is omitted, then the
default is to use and alter @code{$0}.@footnote{Note that this means
that the record will first be regenerated using the value of @code{OFS} if
any fields have been changed, and that the fields will be updated
after the substitution, even if the operation is a ``no-op'' such
as @samp{sub(/^/, "")}.}
For example:
@example
str = "water, water, everywhere"
sub(/at/, "ith", str)
@end example
@noindent
sets @code{str} to @w{@samp{wither, water, everywhere}}, by replacing the
leftmost longest occurrence of @samp{at} with @samp{ith}.
If the special character @samp{&} appears in @var{replacement}, it
stands for the precise substring that was matched by @var{regexp}. (If
the regexp can match more than one string, then this precise substring
may vary.) For example:
@example
@{ sub(/candidate/, "& and his wife"); print @}
@end example
@noindent
changes the first occurrence of @samp{candidate} to @samp{candidate
and his wife} on each input line.
Here is another example:
@example
$ @kbd{awk 'BEGIN @{}
> @kbd{str = "daabaaa"}
> @kbd{sub(/a+/, "C&C", str)}
> @kbd{print str}
> @kbd{@}'}
@print{} dCaaCbaaa
@end example
@noindent
This shows how @samp{&} can represent a nonconstant string and also
illustrates the ``leftmost, longest'' rule in regexp matching
(@pxref{Leftmost Longest}).
The effect of this special character (@samp{&}) can be turned off by putting a
backslash before it in the string. As usual, to insert one backslash in
the string, you must write two backslashes. Therefore, write @samp{\\&}
in a string constant to include a literal @samp{&} in the replacement.
For example, the following shows how to replace the first @samp{|} on each line with
an @samp{&}:
@example
@{ sub(/\|/, "\\&"); print @}
@end example
@cindex @code{sub()} function @subentry arguments of
@cindex @code{gsub()} function @subentry arguments of
@cindex side effects @subentry @code{sub()} function
@cindex side effects @subentry @code{gsub()} function
As mentioned, the third argument to @code{sub()} must
be a variable, field, or array element.
Some versions of @command{awk} allow the third argument to
be an expression that is not an lvalue. In such a case, @code{sub()}
still searches for the pattern and returns zero or one, but the result of
the substitution (if any) is thrown away because there is no place
to put it. Such versions of @command{awk} accept expressions
like the following:
@example
sub(/USA/, "United States", "the USA and Canada")
@end example
@noindent
@cindex troubleshooting @subentry @code{gsub()}/@code{sub()} functions
For historical compatibility, @command{gawk} accepts such erroneous code.
However, using any other nonchangeable
object as the third parameter causes a fatal error and your program
will not run.
Finally, if the @var{regexp} is not a regexp constant, it is converted into a
string, and then the value of that string is treated as the regexp to match.
@item @code{substr(@var{string}, @var{start}} [@code{, @var{length}} ]@code{)}
@cindexawkfunc{substr}
@cindex substring
Return a @var{length}-character-long substring of @var{string},
starting at character number @var{start}. The first character of a
string is character number one.@footnote{This is different from
C and C++, in which the first character is number zero.}
For example, @code{substr("washington", 5, 3)} returns @code{"ing"}.
If @var{length} is not present, @code{substr()} returns the whole suffix of
@var{string} that begins at character number @var{start}. For example,
@code{substr("washington", 5)} returns @code{"ington"}. The whole
suffix is also returned
if @var{length} is greater than the number of characters remaining
in the string, counting from character @var{start}.
@cindex Brian Kernighan's @command{awk}
If @var{start} is less than one, @code{substr()} treats it as
if it was one. (POSIX doesn't specify what to do in this case:
BWK @command{awk} acts this way, and therefore @command{gawk}
does too.)
If @var{start} is greater than the number of characters
in the string, @code{substr()} returns the null string.
Similarly, if @var{length} is present but less than or equal to zero,
the null string is returned.
@cindex troubleshooting @subentry @code{substr()} function
The string returned by @code{substr()} @emph{cannot} be
assigned. Thus, it is a mistake to attempt to change a portion of
a string, as shown in the following example:
@example
string = "abcdef"
# try to get "abCDEf", won't work
substr(string, 3, 3) = "CDE"
@end example
@noindent
It is also a mistake to use @code{substr()} as the third argument
of @code{sub()} or @code{gsub()}:
@example
gsub(/xyz/, "pdq", substr($0, 5, 20)) # WRONG
@end example
@cindex portability @subentry @code{substr()} function
(Some commercial versions of @command{awk} treat
@code{substr()} as assignable, but doing so is not portable.)
If you need to replace bits and pieces of a string, combine @code{substr()}
with string concatenation, in the following manner:
@example
string = "abcdef"
@dots{}
string = substr(string, 1, 2) "CDE" substr(string, 6)
@end example
@cindex case sensitivity @subentry converting case
@cindex strings @subentry converting letter case
@item @code{tolower(@var{string})}
@cindexawkfunc{tolower}
@cindex converting @subentry string to lower case
Return a copy of @var{string}, with each uppercase character
in the string replaced with its corresponding lowercase character.
Nonalphabetic characters are left unchanged. For example,
@code{tolower("MiXeD cAsE 123")} returns @code{"mixed case 123"}.
@item @code{toupper(@var{string})}
@cindexawkfunc{toupper}
@cindex converting @subentry string to upper case
Return a copy of @var{string}, with each lowercase character
in the string replaced with its corresponding uppercase character.
Nonalphabetic characters are left unchanged. For example,
@code{toupper("MiXeD cAsE 123")} returns @code{"MIXED CASE 123"}.
@end table
@cindex sidebar @subentry Matching the Null String
@ifdocbook
@docbook
<sidebar><title>Matching the Null String</title>
@end docbook
@cindex matching @subentry null strings
@cindex null strings @subentry matching
@cindex @code{*} (asterisk) @subentry @code{*} operator @subentry null strings, matching
@cindex asterisk (@code{*}) @subentry @code{*} operator @subentry null strings, matching
In @command{awk}, the @samp{*} operator can match the null string.
This is particularly important for the @code{sub()}, @code{gsub()},
and @code{gensub()} functions. For example:
@example
$ @kbd{echo abc | awk '@{ gsub(/m*/, "X"); print @}'}
@print{} XaXbXcX
@end example
@noindent
Although this makes a certain amount of sense, it can be surprising.
@docbook
</sidebar>
@end docbook
@end ifdocbook
@ifnotdocbook
@cartouche
@center @b{Matching the Null String}
@cindex matching @subentry null strings
@cindex null strings @subentry matching
@cindex @code{*} (asterisk) @subentry @code{*} operator @subentry null strings, matching
@cindex asterisk (@code{*}) @subentry @code{*} operator @subentry null strings, matching
In @command{awk}, the @samp{*} operator can match the null string.
This is particularly important for the @code{sub()}, @code{gsub()},
and @code{gensub()} functions. For example:
@example
$ @kbd{echo abc | awk '@{ gsub(/m*/, "X"); print @}'}
@print{} XaXbXcX
@end example
@noindent
Although this makes a certain amount of sense, it can be surprising.
@end cartouche
@end ifnotdocbook
@node Gory Details
@subsubsection More about @samp{\} and @samp{&} with @code{sub()}, @code{gsub()}, and @code{gensub()}
@cindex escape processing @subentry @code{gsub()}/@code{gensub()}/@code{sub()} functions
@cindex @code{sub()} function @subentry escape processing
@cindex @code{gsub()} function @subentry escape processing
@cindex @code{gensub()} function (@command{gawk}) @subentry escape processing
@cindex @code{\} (backslash) @subentry @code{gsub()}/@code{gensub()}/@code{sub()} functions and
@cindex backslash (@code{\}) @subentry @code{gsub()}/@code{gensub()}/@code{sub()} functions and
@cindex @code{&} (ampersand) @subentry @code{gsub()}/@code{gensub()}/@code{sub()} functions and
@cindex ampersand (@code{&}) @subentry @code{gsub()}/@code{gensub()}/@code{sub()} functions and
@quotation CAUTION
This subsubsection has been reported to cause headaches.
You might want to skip it upon first reading.
@end quotation
When using @code{sub()}, @code{gsub()}, or @code{gensub()}, and trying to get literal
backslashes and ampersands into the replacement text, you need to remember
that there are several levels of @dfn{escape processing} going on.
First, there is the @dfn{lexical} level, which is when @command{awk} reads
your program
and builds an internal copy of it to execute.
Then there is the runtime level, which is when @command{awk} actually scans the
replacement string to determine what to generate.
@cindex Brian Kernighan's @command{awk}
At both levels, @command{awk} looks for a defined set of characters that
can come after a backslash. At the lexical level, it looks for the
escape sequences listed in @ref{Escape Sequences}.
Thus, for every @samp{\} that @command{awk} processes at the runtime
level, you must type two backslashes at the lexical level.
When a character that is not valid for an escape sequence follows the
@samp{\}, BWK @command{awk} and @command{gawk} both simply remove the initial
@samp{\} and put the next character into the string. Thus, for
example, @code{"a\qb"} is treated as @code{"aqb"}.
At the runtime level, the various functions handle sequences of
@samp{\} and @samp{&} differently. The situation is (sadly) somewhat complex.
Historically, the @code{sub()} and @code{gsub()} functions treated the
two-character sequence @samp{\&} specially; this sequence was replaced in
the generated text with a single @samp{&}. Any other @samp{\} within
the @var{replacement} string that did not precede an @samp{&} was passed
through unchanged. This is illustrated in @ref{table-sub-escapes}.
@c Thank to Karl Berry for help with the TeX stuff.
@float Table,table-sub-escapes
@caption{Historical escape sequence processing for @code{sub()} and @code{gsub()}}
@tex
\vbox{\bigskip
% We need more characters for escape and tab ...
\catcode`_ = 0
\catcode`! = 4
% ... since this table has lots of &'s and \'s, so we unspecialize them.
\catcode`\& = \other \catcode`\\ = \other
_halign{_hfil#!_qquad_hfil#!_qquad#_hfil_cr
You type!@code{sub()} sees!@code{sub()} generates_cr
_hrulefill!_hrulefill!_hrulefill_cr
@code{\&}! @code{&}!The matched text_cr
@code{\\&}! @code{\&}!A literal @samp{&}_cr
@code{\\\&}! @code{\&}!A literal @samp{&}_cr
@code{\\\\&}! @code{\\&}!A literal @samp{\&}_cr
@code{\\\\\&}! @code{\\&}!A literal @samp{\&}_cr
@code{\\\\\\&}! @code{\\\&}!A literal @samp{\\&}_cr
@code{\\q}! @code{\q}!A literal @samp{\q}_cr
}
_bigskip}
@end tex
@ifdocbook
@multitable @columnfractions .20 .20 .60
@headitem You type @tab @code{sub()} sees @tab @code{sub()} generates
@item @code{\&} @tab @code{&} @tab The matched text
@item @code{\\&} @tab @code{\&} @tab A literal @samp{&}
@item @code{\\\&} @tab @code{\&} @tab A literal @samp{&}
@item @code{\\\\&} @tab @code{\\&} @tab A literal @samp{\&}
@item @code{\\\\\&} @tab @code{\\&} @tab A literal @samp{\&}
@item @code{\\\\\\&} @tab @code{\\\&} @tab A literal @samp{\\&}
@item @code{\\q} @tab @code{\q} @tab A literal @samp{\q}
@end multitable
@end ifdocbook
@ifnottex
@ifnotdocbook
@display
You type @code{sub()} sees @code{sub()} generates
-------- ---------- ---------------
@code{\&} @code{&} The matched text
@code{\\&} @code{\&} A literal @samp{&}
@code{\\\&} @code{\&} A literal @samp{&}
@code{\\\\&} @code{\\&} A literal @samp{\&}
@code{\\\\\&} @code{\\&} A literal @samp{\&}
@code{\\\\\\&} @code{\\\&} A literal @samp{\\&}
@code{\\q} @code{\q} A literal @samp{\q}
@end display
@end ifnotdocbook
@end ifnottex
@end float
@noindent
This table shows the lexical-level processing, where
an odd number of backslashes becomes an even number at the runtime level,
as well as the runtime processing done by @code{sub()}.
(For the sake of simplicity, the rest of the following tables only show the
case of even numbers of backslashes entered at the lexical level.)
The problem with the historical approach is that there is no way to get
a literal @samp{\} followed by the matched text.
Several editions of the POSIX standard attempted to fix this problem
but weren't successful. The details are irrelevant at this point in time.
At one point, the @command{gawk} maintainer submitted
proposed text for a revised standard that
reverts to rules that correspond more closely to the original existing
practice. The proposed rules have special cases that make it possible
to produce a @samp{\} preceding the matched text.
This is shown in
@ref{table-sub-proposed}.
@float Table,table-sub-proposed
@caption{@command{gawk} rules for @code{sub()} and backslash}
@tex
\vbox{\bigskip
% We need more characters for escape and tab ...
\catcode`_ = 0
\catcode`! = 4
% ... since this table has lots of &'s and \'s, so we unspecialize them.
\catcode`\& = \other \catcode`\\ = \other
_halign{_hfil#!_qquad_hfil#!_qquad#_hfil_cr
You type!@code{sub()} sees!@code{sub()} generates_cr
_hrulefill!_hrulefill!_hrulefill_cr
@code{\\\\\\&}! @code{\\\&}!A literal @samp{\&}_cr
@code{\\\\&}! @code{\\&}!A literal @samp{\}, followed by the matched text_cr
@code{\\&}! @code{\&}!A literal @samp{&}_cr
@code{\\q}! @code{\q}!A literal @samp{\q}_cr
@code{\\\\}! @code{\\}!@code{\\}_cr
}
_bigskip}
@end tex
@ifdocbook
@multitable @columnfractions .20 .20 .60
@headitem You type @tab @code{sub()} sees @tab @code{sub()} generates
@item @code{\\\\\\&} @tab @code{\\\&} @tab A literal @samp{\&}
@item @code{\\\\&} @tab @code{\\&} @tab A literal @samp{\}, followed by the matched text
@item @code{\\&} @tab @code{\&} @tab A literal @samp{&}
@item @code{\\q} @tab @code{\q} @tab A literal @samp{\q}
@item @code{\\\\} @tab @code{\\} @tab @code{\\}
@end multitable
@end ifdocbook
@ifnottex
@ifnotdocbook
@display
You type @code{sub()} sees @code{sub()} generates
-------- ---------- ---------------
@code{\\\\\\&} @code{\\\&} A literal @samp{\&}
@code{\\\\&} @code{\\&} A literal @samp{\}, followed by the matched text
@code{\\&} @code{\&} A literal @samp{&}
@code{\\q} @code{\q} A literal @samp{\q}
@code{\\\\} @code{\\} @code{\\}
@end display
@end ifnotdocbook
@end ifnottex
@end float
In a nutshell, at the runtime level, there are now three special sequences
of characters (@samp{\\\&}, @samp{\\&}, and @samp{\&}) whereas historically
there was only one. However, as in the historical case, any @samp{\} that
is not part of one of these three sequences is not special and appears
in the output literally.
@command{gawk} 3.0 and 3.1 follow these rules for @code{sub()} and
@code{gsub()}. The POSIX standard took much longer to be revised than
was expected. In addition, the @command{gawk} maintainer's proposal was
lost during the standardization process. The final rules are
somewhat simpler. The results are similar except for one case.
@cindex POSIX @command{awk} @subentry functions and @subentry @code{gsub()}/@code{sub()}
The POSIX rules state that @samp{\&} in the replacement string produces
a literal @samp{&}, @samp{\\} produces a literal @samp{\}, and @samp{\} followed
by anything else is not special; the @samp{\} is placed straight into the output.
These rules are presented in @ref{table-posix-sub}.
@float Table,table-posix-sub
@caption{POSIX rules for @code{sub()} and @code{gsub()}}
@tex
\vbox{\bigskip
% We need more characters for escape and tab ...
\catcode`_ = 0
\catcode`! = 4
% ... since this table has lots of &'s and \'s, so we unspecialize them.
\catcode`\& = \other \catcode`\\ = \other
_halign{_hfil#!_qquad_hfil#!_qquad#_hfil_cr
You type!@code{sub()} sees!@code{sub()} generates_cr
_hrulefill!_hrulefill!_hrulefill_cr
@code{\\\\\\&}! @code{\\\&}!A literal @samp{\&}_cr
@code{\\\\&}! @code{\\&}!A literal @samp{\}, followed by the matched text_cr
@code{\\&}! @code{\&}!A literal @samp{&}_cr
@code{\\q}! @code{\q}!A literal @samp{\q}_cr
@code{\\\\}! @code{\\}!@code{\}_cr
}
_bigskip}
@end tex
@ifdocbook
@multitable @columnfractions .20 .20 .60
@headitem You type @tab @code{sub()} sees @tab @code{sub()} generates
@item @code{\\\\\\&} @tab @code{\\\&} @tab A literal @samp{\&}
@item @code{\\\\&} @tab @code{\\&} @tab A literal @samp{\}, followed by the matched text
@item @code{\\&} @tab @code{\&} @tab A literal @samp{&}
@item @code{\\q} @tab @code{\q} @tab A literal @samp{\q}
@item @code{\\\\} @tab @code{\\} @tab @code{\}
@end multitable
@end ifdocbook
@ifnottex
@ifnotdocbook
@display
You type @code{sub()} sees @code{sub()} generates
-------- ---------- ---------------
@code{\\\\\\&} @code{\\\&} A literal @samp{\&}
@code{\\\\&} @code{\\&} A literal @samp{\}, followed by the matched text
@code{\\&} @code{\&} A literal @samp{&}
@code{\\q} @code{\q} A literal @samp{\q}
@code{\\\\} @code{\\} @code{\}
@end display
@end ifnotdocbook
@end ifnottex
@end float
The only case where the difference is noticeable is the last one: @samp{\\\\}
is seen as @samp{\\} and produces @samp{\} instead of @samp{\\}.
Starting with @value{PVERSION} 3.1.4, @command{gawk} followed the POSIX rules
when @option{--posix} was specified (@pxref{Options}). Otherwise,
it continued to follow the proposed rules, as
that had been its behavior for many years.
When @value{PVERSION} 4.0.0 was released, the @command{gawk} maintainer
made the POSIX rules the default, breaking well over a decade's worth
of backward compatibility.@footnote{This was rather naive of him, despite
there being a note in this @value{SECTION} indicating that the next major version
would move to the POSIX rules.} Needless to say, this was a bad idea,
and as of @value{PVERSION} 4.0.1, @command{gawk} resumed its historical
behavior, and only follows the POSIX rules when @option{--posix} is given.
The rules for @code{gensub()} are considerably simpler. At the runtime
level, whenever @command{gawk} sees a @samp{\}, if the following character
is a digit, then the text that matched the corresponding parenthesized
subexpression is placed in the generated output. Otherwise,
no matter what character follows the @samp{\}, it
appears in the generated text and the @samp{\} does not,
as shown in @ref{table-gensub-escapes}.
@float Table,table-gensub-escapes
@caption{Escape sequence processing for @code{gensub()}}
@tex
\vbox{\bigskip
% We need more characters for escape and tab ...
\catcode`_ = 0
\catcode`! = 4
% ... since this table has lots of &'s and \'s, so we unspecialize them.
\catcode`\& = \other \catcode`\\ = \other
_halign{_hfil#!_qquad_hfil#!_qquad#_hfil_cr
You type!@code{gensub()} sees!@code{gensub()} generates_cr
_hrulefill!_hrulefill!_hrulefill_cr
@code{&}! @code{&}!The matched text_cr
@code{\\&}! @code{\&}!A literal @samp{&}_cr
@code{\\\\}! @code{\\}!A literal @samp{\}_cr
@code{\\\\&}! @code{\\&}!A literal @samp{\}, then the matched text_cr
@code{\\\\\\&}! @code{\\\&}!A literal @samp{\&}_cr
@code{\\q}! @code{\q}!A literal @samp{q}_cr
}
_bigskip}
@end tex
@ifdocbook
@multitable @columnfractions .20 .20 .60
@headitem You type @tab @code{gensub()} sees @tab @code{gensub()} generates
@item @code{&} @tab @code{&} @tab The matched text
@item @code{\\&} @tab @code{\&} @tab A literal @samp{&}
@item @code{\\\\} @tab @code{\\} @tab A literal @samp{\}
@item @code{\\\\&} @tab @code{\\&} @tab A literal @samp{\}, then the matched text
@item @code{\\\\\\&} @tab @code{\\\&} @tab A literal @samp{\&}
@item @code{\\q} @tab @code{\q} @tab A literal @samp{q}
@end multitable
@end ifdocbook
@ifnottex
@ifnotdocbook
@display
You type @code{gensub()} sees @code{gensub()} generates
-------- ------------- ------------------
@code{&} @code{&} The matched text
@code{\\&} @code{\&} A literal @samp{&}
@code{\\\\} @code{\\} A literal @samp{\}
@code{\\\\&} @code{\\&} A literal @samp{\}, then the matched text
@code{\\\\\\&} @code{\\\&} A literal @samp{\&}
@code{\\q} @code{\q} A literal @samp{q}
@end display
@end ifnotdocbook
@end ifnottex
@end float
Because of the complexity of the lexical- and runtime-level processing
and the special cases for @code{sub()} and @code{gsub()},
we recommend the use of @command{gawk} and @code{gensub()} when you have
to do substitutions.
@node I/O Functions
@subsection Input/Output Functions
@cindex input/output @subentry functions
The following functions relate to input/output (I/O).
Optional parameters are enclosed in square brackets ([ ]):
@table @asis
@item @code{close(}@var{filename} [@code{,} @var{how}]@code{)}
@cindexawkfunc{close}
@cindex files @subentry closing
@cindex close file or coprocess
Close the file @var{filename} for input or output. Alternatively, the
argument may be a shell command that was used for creating a coprocess, or
for redirecting to or from a pipe; then the coprocess or pipe is closed.
@xref{Close Files And Pipes}
for more information.
When closing a coprocess, it is occasionally useful to first close
one end of the two-way pipe and then to close the other. This is done
by providing a second argument to @code{close()}. This second argument
(@var{how})
should be one of the two string values @code{"to"} or @code{"from"},
indicating which end of the pipe to close. Case in the string does
not matter.
@xref{Two-way I/O},
which discusses this feature in more detail and gives an example.
Note that the second argument to @code{close()} is a @command{gawk}
extension; it is not available in compatibility mode (@pxref{Options}).
@item @code{fflush(}[@var{filename}]@code{)}
@cindexawkfunc{fflush}
@cindex flush buffered output
Flush any buffered output associated with @var{filename}, which is either a
file opened for writing or a shell command for redirecting output to
a pipe or coprocess.
@cindex buffers @subentry flushing
@cindex output @subentry buffering
Many utility programs @dfn{buffer} their output (i.e., they save information
to write to a disk file or the screen in memory until there is enough
for it to be worthwhile to send the data to the output device).
This is often more efficient than writing
every little bit of information as soon as it is ready. However, sometimes
it is necessary to force a program to @dfn{flush} its buffers (i.e.,
write the information to its destination, even if a buffer is not full).
This is the purpose of the @code{fflush()} function---@command{gawk} also
buffers its output, and the @code{fflush()} function forces
@command{gawk} to flush its buffers.
@cindex extensions @subentry common @subentry @code{fflush()} function
@cindex Brian Kernighan's @command{awk}
Brian Kernighan added @code{fflush()} to his @command{awk} in April
1992. For two decades, it was a common extension. In December
2012, it was accepted for inclusion into the POSIX standard.
See @uref{http://austingroupbugs.net/view.php?id=634, the Austin Group website}.
POSIX standardizes @code{fflush()} as follows: if there
is no argument, or if the argument is the null string (@w{@code{""}}),
then @command{awk} flushes the buffers for @emph{all} open output files
and pipes.
@quotation NOTE
Prior to @value{PVERSION} 4.0.2, @command{gawk}
would flush only the standard output if there was no argument,
and flush all output files and pipes if the argument was the null
string. This was changed in order to be compatible with Brian
Kernighan's @command{awk}, in the hope that standardizing this
feature in POSIX would then be easier (which indeed proved to be the case).
With @command{gawk},
you can use @samp{fflush("/dev/stdout")} if you wish to flush
only the standard output.
@end quotation
@c @cindex automatic warnings
@c @cindex warnings, automatic
@cindex troubleshooting @subentry @code{fflush()} function
@code{fflush()} returns zero if the buffer is successfully flushed;
otherwise, it returns a nonzero value. (@command{gawk} returns @minus{}1.)
In the case where all buffers are flushed, the return value is zero
only if all buffers were flushed successfully. Otherwise, it is
@minus{}1, and @command{gawk} warns about the problem @var{filename}.
@command{gawk} also issues a warning message if you attempt to flush
a file or pipe that was opened for reading (such as with @code{getline}),
or if @var{filename} is not an open file, pipe, or coprocess.
In such a case, @code{fflush()} returns @minus{}1, as well.
@c end the table to let the sidebar take up the full width of the page.
@end table
@cindex sidebar @subentry Interactive Versus Noninteractive Buffering
@ifdocbook
@docbook
<sidebar><title>Interactive Versus Noninteractive Buffering</title>
@end docbook
@cindex buffering @subentry interactive vs.@: noninteractive
As a side point, buffering issues can be even more confusing if
your program is @dfn{interactive} (i.e., communicating
with a user sitting at a keyboard).@footnote{A program is interactive
if the standard output is connected to a terminal device. On modern
systems, this means your keyboard and screen.}
@c Thanks to Walter.Mecky@dresdnerbank.de for this example, and for
@c motivating me to write this section.
Interactive programs generally @dfn{line buffer} their output (i.e., they
write out every line). Noninteractive programs wait until they have
a full buffer, which may be many lines of output.
Here is an example of the difference:
@example
$ @kbd{awk '@{ print $1 + $2 @}'}
@kbd{1 1}
@print{} 2
@kbd{2 3}
@print{} 5
@kbd{Ctrl-d}
@end example
@noindent
Each line of output is printed immediately. Compare that behavior
with this example:
@example
$ @kbd{awk '@{ print $1 + $2 @}' | cat}
@kbd{1 1}
@kbd{2 3}
@kbd{Ctrl-d}
@print{} 2
@print{} 5
@end example
@noindent
Here, no output is printed until after the @kbd{Ctrl-d} is typed, because
it is all buffered and sent down the pipe to @command{cat} in one shot.
@docbook
</sidebar>
@end docbook
@end ifdocbook
@ifnotdocbook
@cartouche
@center @b{Interactive Versus Noninteractive Buffering}
@cindex buffering @subentry interactive vs.@: noninteractive
As a side point, buffering issues can be even more confusing if
your program is @dfn{interactive} (i.e., communicating
with a user sitting at a keyboard).@footnote{A program is interactive
if the standard output is connected to a terminal device. On modern
systems, this means your keyboard and screen.}
@c Thanks to Walter.Mecky@dresdnerbank.de for this example, and for
@c motivating me to write this section.
Interactive programs generally @dfn{line buffer} their output (i.e., they
write out every line). Noninteractive programs wait until they have
a full buffer, which may be many lines of output.
Here is an example of the difference:
@example
$ @kbd{awk '@{ print $1 + $2 @}'}
@kbd{1 1}
@print{} 2
@kbd{2 3}
@print{} 5
@kbd{Ctrl-d}
@end example
@noindent
Each line of output is printed immediately. Compare that behavior
with this example:
@example
$ @kbd{awk '@{ print $1 + $2 @}' | cat}
@kbd{1 1}
@kbd{2 3}
@kbd{Ctrl-d}
@print{} 2
@print{} 5
@end example
@noindent
Here, no output is printed until after the @kbd{Ctrl-d} is typed, because
it is all buffered and sent down the pipe to @command{cat} in one shot.
@end cartouche
@end ifnotdocbook
@table @asis
@item @code{system(@var{command})}
@cindexawkfunc{system}
@cindex invoke shell command
@cindex interacting with other programs
Execute the operating system
command @var{command} and then return to the @command{awk} program.
Return @var{command}'s exit status (see further on).
For example, if the following fragment of code is put in your @command{awk}
program:
@example
END @{
system("date | mail -s 'awk run done' root")
@}
@end example
@noindent
the system administrator is sent mail when the @command{awk} program
finishes processing input and begins its end-of-input processing.
Note that redirecting @code{print} or @code{printf} into a pipe is often
enough to accomplish your task. If you need to run many commands, it
is more efficient to simply print them down a pipeline to the shell:
@example
while (@var{more stuff to do})
print @var{command} | "/bin/sh"
close("/bin/sh")
@end example
@noindent
@cindex troubleshooting @subentry @code{system()} function
@cindex @option{--sandbox} option @subentry disabling @code{system()} function
However, if your @command{awk}
program is interactive, @code{system()} is useful for running large
self-contained programs, such as a shell or an editor.
Some operating systems cannot implement the @code{system()} function.
@code{system()} causes a fatal error if it is not supported.
@quotation NOTE
When @option{--sandbox} is specified, the @code{system()} function is disabled
(@pxref{Options}).
@end quotation
On POSIX systems, a command's exit status is a 16-bit number. The exit
value passed to the C @code{exit()} function is held in the high-order
eight bits. The low-order bits indicate if the process was killed by a
signal (bit 7) and if so, the guilty signal number (bits 0--6).
Traditionally, @command{awk}'s @code{system()} function has simply
returned the exit status value divided by 256. In the normal case this
gives the exit status but in the case of death-by-signal it yields
a fractional floating-point value.@footnote{In private correspondence,
Dr.@: Kernighan has indicated to me that the way this was done
was probably a mistake.} POSIX states that @command{awk}'s
@code{system()} should return the full 16-bit value.
@command{gawk} steers a middle ground.
The return values are summarized in @ref{table-system-return-values}.
@float Table,table-system-return-values
@caption{Return values from @code{system()}}
@multitable @columnfractions .40 .60
@headitem Situation @tab Return value from @code{system()}
@item @option{--traditional} @tab C @code{system()}'s value divided by 256
@item @option{--posix} @tab C @code{system()}'s value
@item Normal exit of command @tab Command's exit status
@item Death by signal of command @tab 256 + number of murderous signal
@item Death by signal of command with core dump @tab 512 + number of murderous signal
@item Some kind of error @tab @minus{}1
@end multitable
@end float
@end table
As of August, 2018, BWK @command{awk} now follows @command{gawk}'s behavior
for the return value of @code{system()}.
@cindex sidebar @subentry Controlling Output Buffering with @code{system()}
@ifdocbook
@docbook
<sidebar><title>Controlling Output Buffering with @code{system()}</title>
@end docbook
@cindex buffers @subentry flushing
@cindex buffering @subentry input/output
@cindex output @subentry buffering
The @code{fflush()} function provides explicit control over output buffering for
individual files and pipes. However, its use is not portable to many older
@command{awk} implementations. An alternative method to flush output
buffers is to call @code{system()} with a null string as its argument:
@example
system("") # flush output
@end example
@noindent
@command{gawk} treats this use of the @code{system()} function as a special
case and is smart enough not to run a shell (or other command
interpreter) with the empty command. Therefore, with @command{gawk}, this
idiom is not only useful, it is also efficient. Although this method should work
with other @command{awk} implementations, it does not necessarily avoid
starting an unnecessary shell. (Other implementations may only
flush the buffer associated with the standard output and not necessarily
all buffered output.)
If you think about what a programmer expects, it makes sense that
@code{system()} should flush any pending output. The following program:
@example
BEGIN @{
print "first print"
system("echo system echo")
print "second print"
@}
@end example
@noindent
must print:
@example
first print
system echo
second print
@end example
@noindent
and not:
@example
system echo
first print
second print
@end example
If @command{awk} did not flush its buffers before calling @code{system()},
you would see the latter (undesirable) output.
@docbook
</sidebar>
@end docbook
@end ifdocbook
@ifnotdocbook
@cartouche
@center @b{Controlling Output Buffering with @code{system()}}
@cindex buffers @subentry flushing
@cindex buffering @subentry input/output
@cindex output @subentry buffering
The @code{fflush()} function provides explicit control over output buffering for
individual files and pipes. However, its use is not portable to many older
@command{awk} implementations. An alternative method to flush output
buffers is to call @code{system()} with a null string as its argument:
@example
system("") # flush output
@end example
@noindent
@command{gawk} treats this use of the @code{system()} function as a special
case and is smart enough not to run a shell (or other command
interpreter) with the empty command. Therefore, with @command{gawk}, this
idiom is not only useful, it is also efficient. Although this method should work
with other @command{awk} implementations, it does not necessarily avoid
starting an unnecessary shell. (Other implementations may only
flush the buffer associated with the standard output and not necessarily
all buffered output.)
If you think about what a programmer expects, it makes sense that
@code{system()} should flush any pending output. The following program:
@example
BEGIN @{
print "first print"
system("echo system echo")
print "second print"
@}
@end example
@noindent
must print:
@example
first print
system echo
second print
@end example
@noindent
and not:
@example
system echo
first print
second print
@end example
If @command{awk} did not flush its buffers before calling @code{system()},
you would see the latter (undesirable) output.
@end cartouche
@end ifnotdocbook
@node Time Functions
@subsection Time Functions
@cindex time functions
@cindex timestamps
@cindex log files, timestamps in
@cindex files @subentry log, timestamps in
@cindex @command{gawk} @subentry timestamps
@cindex POSIX @command{awk} @subentry timestamps and
@command{awk} programs are commonly used to process log files
containing timestamp information, indicating when a
particular log record was written. Many programs log their timestamps
in the form returned by the @code{time()} system call, which is the
number of seconds since a particular epoch. On POSIX-compliant systems,
it is the number of seconds since
1970-01-01 00:00:00 UTC, not counting leap
@ifclear FOR_PRINT
seconds.@footnote{@xref{Glossary}, especially the entries ``Epoch'' and ``UTC.''}
@end ifclear
@ifset FOR_PRINT
seconds.
@end ifset
All known POSIX-compliant systems support timestamps from 0 through
@iftex
@math{2^{31} - 1},
@end iftex
@ifinfo
2^31 - 1,
@end ifinfo
@ifnottex
@ifnotinfo
2@sup{31} @minus{} 1,
@end ifnotinfo
@end ifnottex
which is sufficient to represent times through
2038-01-19 03:14:07 UTC. Many systems support a wider range of timestamps,
including negative timestamps that represent times before the
epoch.
@cindex @command{date} utility @subentry GNU
@cindex time @subentry retrieving
In order to make it easier to process such log files and to produce
useful reports, @command{gawk} provides the following functions for
working with timestamps. They are @command{gawk} extensions; they are
not specified in the POSIX standard.@footnote{The GNU @command{date} utility can
also do many of the things described here. Its use may be preferable
for simple time-related operations in shell scripts.}
However, recent versions
of @command{mawk} (@pxref{Other Versions}) also support these functions.
Optional parameters are enclosed in square brackets ([ ]):
@c @asis for docbook
@table @asis
@item @code{mktime(@var{datespec}} [@code{, @var{utc-flag}} ]@code{)}
@cindexgawkfunc{mktime}
@cindex generate time values
Turn @var{datespec} into a timestamp in the same form
as is returned by @code{systime()}. It is similar to the function of the
same name in ISO C. The argument, @var{datespec}, is a string of the form
@w{@code{"@var{YYYY} @var{MM} @var{DD} @var{HH} @var{MM} @var{SS} [@var{DST}]"}}.
The string consists of six or seven numbers representing, respectively,
the full year including century, the month from 1 to 12, the day of the month
from 1 to 31, the hour of the day from 0 to 23, the minute from 0 to
59, the second from 0 to 60,@footnote{Occasionally there are
minutes in a year with a leap second, which is why the
seconds can go up to 60.}
and an optional daylight-savings flag.
The values of these numbers need not be within the ranges specified;
for example, an hour of @minus{}1 means 1 hour before midnight.
The origin-zero Gregorian calendar is assumed, with year 0 preceding
year 1 and year @minus{}1 preceding year 0.
If @var{utc-flag} is present and is either nonzero or non-null, the time
is assumed to be in the UTC time zone; otherwise, the
time is assumed to be in the local time zone.
If the @var{DST} daylight-savings flag is positive, the time is assumed to be
daylight savings time; if zero, the time is assumed to be standard
time; and if negative (the default), @code{mktime()} attempts to determine
whether daylight savings time is in effect for the specified time.
If @var{datespec} does not contain enough elements or if the resulting time
is out of range, @code{mktime()} returns @minus{}1.
@cindex @command{gawk} @subentry @code{PROCINFO} array in
@cindex @code{PROCINFO} array
@item @code{strftime(}[@var{format} [@code{,} @var{timestamp} [@code{,} @var{utc-flag}] ] ]@code{)}
@cindexgawkfunc{strftime}
@cindex format time string
Format the time specified by @var{timestamp}
based on the contents of the @var{format} string and return the result.
It is similar to the function of the same name in ISO C.
If @var{utc-flag} is present and is either nonzero or non-null, the value
is formatted as UTC (Coordinated Universal Time, formerly GMT or Greenwich
Mean Time). Otherwise, the value is formatted for the local time zone.
The @var{timestamp} is in the same format as the value returned by the
@code{systime()} function. If no @var{timestamp} argument is supplied,
@command{gawk} uses the current time of day as the timestamp.
Without a @var{format} argument, @code{strftime()} uses
the value of @code{PROCINFO["strftime"]} as the format string
(@pxref{Built-in Variables}).
The default string value is
@code{@w{"%a %b %e %H:%M:%S %Z %Y"}}. This format string produces
output that is equivalent to that of the @command{date} utility.
You can assign a new value to @code{PROCINFO["strftime"]} to
change the default format; see the following list for the various format directives.
@item @code{systime()}
@cindexgawkfunc{systime}
@cindex timestamps
@cindex current system time
Return the current time as the number of seconds since
the system epoch. On POSIX systems, this is the number of seconds
since 1970-01-01 00:00:00 UTC, not counting leap seconds.
It may be a different number on other systems.
@end table
The @code{systime()} function allows you to compare a timestamp from a
log file with the current time of day. In particular, it is easy to
determine how long ago a particular record was logged. It also allows
you to produce log records using the ``seconds since the epoch'' format.
@cindex converting @subentry dates to timestamps
@cindex dates @subentry converting to timestamps
@cindex timestamps @subentry converting dates to
The @code{mktime()} function allows you to convert a textual representation
of a date and time into a timestamp. This makes it easy to do before/after
comparisons of dates and times, particularly when dealing with date and
time data coming from an external source, such as a log file.
The @code{strftime()} function allows you to easily turn a timestamp
into human-readable information. It is similar in nature to the @code{sprintf()}
function
(@pxref{String Functions}),
in that it copies nonformat specification characters verbatim to the
returned string, while substituting date and time values for format
specifications in the @var{format} string.
@cindex format specifiers @subentry @code{strftime()} function (@command{gawk})
@code{strftime()} is guaranteed by the 1999 ISO C
standard@footnote{Unfortunately,
not every system's @code{strftime()} necessarily
supports all of the conversions listed here.}
to support the following date format specifications:
@table @code
@item %a
The locale's abbreviated weekday name.
@item %A
The locale's full weekday name.
@item %b
The locale's abbreviated month name.
@item %B
The locale's full month name.
@item %c
The locale's ``appropriate'' date and time representation.
(This is @samp{%A %B %d %T %Y} in the @code{"C"} locale.)
@item %C
The century part of the current year.
This is the year divided by 100 and truncated to the next
lower integer.
@item %d
The day of the month as a decimal number (01--31).
@item %D
Equivalent to specifying @samp{%m/%d/%y}.
@item %e
The day of the month, padded with a space if it is only one digit.
@item %F
Equivalent to specifying @samp{%Y-%m-%d}.
This is the ISO 8601 date format.
@item %g
The year modulo 100 of the ISO 8601 week number, as a decimal number (00--99).
For example, January 1, 2012, is in week 53 of 2011. Thus, the year
of its ISO 8601 week number is 2011, even though its year is 2012.
Similarly, December 31, 2012, is in week 1 of 2013. Thus, the year
of its ISO week number is 2013, even though its year is 2012.
@item %G
The full year of the ISO week number, as a decimal number.
@item %h
Equivalent to @samp{%b}.
@item %H
The hour (24-hour clock) as a decimal number (00--23).
@item %I
The hour (12-hour clock) as a decimal number (01--12).
@item %j
The day of the year as a decimal number (001--366).
@item %m
The month as a decimal number (01--12).
@item %M
The minute as a decimal number (00--59).
@item %n
A newline character (ASCII LF).
@item %p
The locale's equivalent of the AM/PM designations associated
with a 12-hour clock.
@item %r
The locale's 12-hour clock time.
(This is @samp{%I:%M:%S %p} in the @code{"C"} locale.)
@item %R
Equivalent to specifying @samp{%H:%M}.
@item %S
The second as a decimal number (00--60).
@item %t
A TAB character.
@item %T
Equivalent to specifying @samp{%H:%M:%S}.
@item %u
The weekday as a decimal number (1--7). Monday is day one.
@item %U
The week number of the year (with the first Sunday as the first day of week one)
as a decimal number (00--53).
@cindex ISO @subentry ISO 8601 date and time standard
@item %V
The week number of the year (with the first Monday as the first
day of week one) as a decimal number (01--53).
The method for determining the week number is as specified by ISO 8601.
(To wit: if the week containing January 1 has four or more days in the
new year, then it is week one; otherwise it is the last week
[52 or 53] of the previous year and the next week is week one.)
@item %w
The weekday as a decimal number (0--6). Sunday is day zero.
@item %W
The week number of the year (with the first Monday as the first day of week one)
as a decimal number (00--53).
@item %x
The locale's ``appropriate'' date representation.
(This is @samp{%A %B %d %Y} in the @code{"C"} locale.)
@item %X
The locale's ``appropriate'' time representation.
(This is @samp{%T} in the @code{"C"} locale.)
@item %y
The year modulo 100 as a decimal number (00--99).
@item %Y
The full year as a decimal number (e.g., 2015).
@c @cindex RFC 822
@c @cindex RFC 1036
@item %z
The time zone offset in a @samp{+@var{HHMM}} format (e.g., the format
necessary to produce RFC 822/RFC 1036 date headers).
@item %Z
The time zone name or abbreviation; no characters if
no time zone is determinable.
@item %Ec %EC %Ex %EX %Ey %EY %Od %Oe %OH
@itemx %OI %Om %OM %OS %Ou %OU %OV %Ow %OW %Oy
``Alternative representations'' for the specifications
that use only the second letter (@samp{%c}, @samp{%C},
and so on).@footnote{If you don't understand any of this, don't worry about
it; these facilities are meant to make it easier to ``internationalize''
programs.
Other internationalization features are described in
@ref{Internationalization}.}
(These facilitate compliance with the POSIX @command{date} utility.)
@item %%
A literal @samp{%}.
@end table
If a conversion specifier is not one of those just listed, the behavior is
undefined.@footnote{This is because ISO C leaves the
behavior of the C version of @code{strftime()} undefined and @command{gawk}
uses the system's version of @code{strftime()} if it's there.
Typically, the conversion specifier either does not appear in the
returned string or appears literally.}
For systems that are not yet fully standards-compliant,
@command{gawk} supplies a copy of
@code{strftime()} from the GNU C Library.
It supports all of the just-listed format specifications.
If that version is
used to compile @command{gawk} (@pxref{Installation}),
then the following additional format specifications are available:
@table @code
@item %k
The hour (24-hour clock) as a decimal number (0--23).
Single-digit numbers are padded with a space.
@item %l
The hour (12-hour clock) as a decimal number (1--12).
Single-digit numbers are padded with a space.
@ignore
@item %N
The ``Emperor/Era'' name.
Equivalent to @samp{%C}.
@item %o
The ``Emperor/Era'' year.
Equivalent to @samp{%y}.
@end ignore
@item %s
The time as a decimal timestamp in seconds since the epoch.
@ignore
@item %v
The date in VMS format (e.g., @samp{20-JUN-1991}).
@end ignore
@end table
Additionally, the alternative representations are recognized but their
normal representations are used.
@cindex @code{date} utility @subentry POSIX
@cindex POSIX @command{awk} @subentry @code{date} utility and
The following example is an @command{awk} implementation of the POSIX
@command{date} utility. Normally, the @command{date} utility prints the
current date and time of day in a well-known format. However, if you
provide an argument to it that begins with a @samp{+}, @command{date}
copies nonformat specifier characters to the standard output and
interprets the current time according to the format specifiers in
the string. For example:
@example
$ @kbd{date '+Today is %A, %B %d, %Y.'}
@print{} Today is Monday, September 22, 2014.
@end example
Here is the @command{gawk} version of the @command{date} utility.
It has a shell ``wrapper'' to handle the @option{-u} option,
which requires that @command{date} run as if the time zone
is set to UTC:
@example
#! /bin/sh
#
# date --- approximate the POSIX 'date' command
case $1 in
-u) TZ=UTC0 # use UTC
export TZ
shift ;;
esac
gawk 'BEGIN @{
format = PROCINFO["strftime"]
exitval = 0
if (ARGC > 2)
exitval = 1
else if (ARGC == 2) @{
format = ARGV[1]
if (format ~ /^\+/)
format = substr(format, 2) # remove leading +
@}
print strftime(format)
exit exitval
@}' "$@@"
@end example
@node Bitwise Functions
@subsection Bit-Manipulation Functions
@cindex bit-manipulation functions
@cindex bitwise @subentry operations
@cindex AND bitwise operation
@cindex OR bitwise operation
@cindex XOR bitwise operation
@cindex operations, bitwise
@quotation
@i{I can explain it for you, but I can't understand it for you.}
@author Anonymous
@end quotation
Many languages provide the ability to perform @dfn{bitwise} operations
on two integer numbers. In other words, the operation is performed on
each successive pair of bits in the operands.
Three common operations are bitwise AND, OR, and XOR.
The operations are described in @ref{table-bitwise-ops}.
@c 11/2014: Postprocessing turns the docbook informaltable
@c into a table. Hurray for scripting!
@float Table,table-bitwise-ops
@caption{Bitwise operations}
@ifnottex
@ifnotdocbook
@verbatim
Bit operator
| AND | OR | XOR
|---+---+---+---+---+---
Operands | 0 | 1 | 0 | 1 | 0 | 1
----------+---+---+---+---+---+---
0 | 0 0 | 0 1 | 0 1
1 | 0 1 | 1 1 | 1 0
@end verbatim
@end ifnotdocbook
@end ifnottex
@tex
\centerline{
\vbox{\bigskip % space above the table (about 1 linespace)
% Because we have vertical rules, we can't let TeX insert interline space
% in its usual way.
\offinterlineskip
\halign{\strut\hfil#\quad\hfil % operands
&\vrule#&\quad#\quad % rule, 0 (of and)
&\vrule#&\quad#\quad % rule, 1 (of and)
&\vrule# % rule between and and or
&\quad#\quad % 0 (of or)
&\vrule#&\quad#\quad % rule, 1 (of of)
&\vrule# % rule between or and xor
&\quad#\quad % 0 of xor
&\vrule#&\quad#\quad % rule, 1 of xor
\cr
&\omit&\multispan{11}\hfil\bf Bit operator\hfil\cr
\noalign{\smallskip}
& &\multispan3\hfil AND\hfil&&\multispan3\hfil OR\hfil
&&\multispan3\hfil XOR\hfil\cr
\bf Operands&&0&&1&&0&&1&&0&&1\cr
\noalign{\hrule}
\omit&height 2pt&&\omit&&&&\omit&&&&\omit\cr
\noalign{\hrule height0pt}% without this the rule does not extend; why?
0&&0&\omit&0&&0&\omit&1&&0&\omit&1\cr
1&&0&\omit&1&&1&\omit&1&&1&\omit&0\cr
}}}
@end tex
@docbook
<informaltable>
<tgroup cols="7" colsep="1">
<colspec colname="c1"/>
<colspec colname="c2"/>
<colspec colname="c3"/>
<colspec colname="c4"/>
<colspec colname="c5"/>
<colspec colname="c6"/>
<colspec colname="c7"/>
<spanspec spanname="optitle" namest="c2" nameend="c7" align="center"/>
<spanspec spanname="andspan" namest="c2" nameend="c3" align="center"/>
<spanspec spanname="orspan" namest="c4" nameend="c5" align="center"/>
<spanspec spanname="xorspan" namest="c6" nameend="c7" align="center"/>
<tbody>
<row>
<entry colsep="0"></entry>
<entry spanname="optitle"><emphasis role="bold">Bit operator</emphasis></entry>
</row>
<row rowsep="1">
<entry rowsep="0"></entry>
<entry spanname="andspan">AND</entry>
<entry spanname="orspan">OR</entry>
<entry spanname="xorspan">XOR</entry>
</row>
<row rowsep="1">
<entry ><emphasis role="bold">Operands</emphasis></entry>
<entry colsep="0">0</entry>
<entry colsep="1">1</entry>
<entry colsep="0">0</entry>
<entry colsep="1">1</entry>
<entry colsep="0">0</entry>
<entry colsep="1">1</entry>
</row>
<row>
<entry align="center">0</entry>
<entry colsep="0">0</entry>
<entry>0</entry>
<entry colsep="0">0</entry>
<entry>1</entry>
<entry colsep="0">0</entry>
<entry>1</entry>
</row>
<row>
<entry align="center">1</entry>
<entry colsep="0">0</entry>
<entry>1</entry>
<entry colsep="0">1</entry>
<entry>1</entry>
<entry colsep="0">1</entry>
<entry>0</entry>
</row>
</tbody>
</tgroup>
</informaltable>
@end docbook
@end float
@cindex bitwise @subentry complement
@cindex complement, bitwise
As you can see, the result of an AND operation is 1 only when @emph{both}
bits are 1.
The result of an OR operation is 1 if @emph{either} bit is 1.
The result of an XOR operation is 1 if either bit is 1,
but not both.
The next operation is the @dfn{complement}; the complement of 1 is 0 and
the complement of 0 is 1. Thus, this operation ``flips'' all the bits
of a given value.
@cindex bitwise @subentry shift
@cindex left shift, bitwise
@cindex right shift, bitwise
@cindex shift, bitwise
Finally, two other common operations are to shift the bits left or right.
For example, if you have a bit string @samp{10111001} and you shift it
right by three bits, you end up with @samp{00010111}.@footnote{This example
shows that zeros come in on the left side. For @command{gawk}, this is
always true, but in some languages, it's possible to have the left side
fill with ones.}
If you start over again with @samp{10111001} and shift it left by three
bits, you end up with @samp{11001000}. The following list describes
@command{gawk}'s built-in functions that implement the bitwise operations.
Optional parameters are enclosed in square brackets ([ ]):
@cindex @command{gawk} @subentry bitwise operations in
@table @asis
@cindexgawkfunc{and}
@cindex bitwise @subentry AND
@item @code{and(}@var{v1}@code{,} @var{v2} [@code{,} @dots{}]@code{)}
Return the bitwise AND of the arguments. There must be at least two.
@cindexgawkfunc{compl}
@cindex bitwise @subentry complement
@item @code{compl(@var{val})}
Return the bitwise complement of @var{val}.
@cindexgawkfunc{lshift}
@item @code{lshift(@var{val}, @var{count})}
Return the value of @var{val}, shifted left by @var{count} bits.
@cindexgawkfunc{or}
@cindex bitwise @subentry OR
@item @code{or(}@var{v1}@code{,} @var{v2} [@code{,} @dots{}]@code{)}
Return the bitwise OR of the arguments. There must be at least two.
@cindexgawkfunc{rshift}
@item @code{rshift(@var{val}, @var{count})}
Return the value of @var{val}, shifted right by @var{count} bits.
@cindexgawkfunc{xor}
@cindex bitwise @subentry XOR
@item @code{xor(}@var{v1}@code{,} @var{v2} [@code{,} @dots{}]@code{)}
Return the bitwise XOR of the arguments. There must be at least two.
@end table
@quotation CAUTION
Beginning with @command{gawk} @value{PVERSION} 4.2, negative
operands are not allowed for any of these functions. A negative
operand produces a fatal error. See the sidebar
``Beware The Smoke and Mirrors!'' for more information as to why.
@end quotation
Here is a user-defined function (@pxref{User-defined})
that illustrates the use of these functions:
@cindex @code{bits2str()} user-defined function
@cindex user-defined @subentry function @subentry @code{bits2str()}
@cindex @code{testbits.awk} program
@example
@group
@c file eg/lib/bits2str.awk
# bits2str --- turn an integer into readable ones and zeros
function bits2str(bits, data, mask)
@{
if (bits == 0)
return "0"
mask = 1
for (; bits != 0; bits = rshift(bits, 1))
data = (and(bits, mask) ? "1" : "0") data
while ((length(data) % 8) != 0)
data = "0" data
return data
@}
@c endfile
@end group
@c this is a hack to make testbits.awk self-contained
@ignore
@c file eg/prog/testbits.awk
# bits2str --- turn an integer into readable ones and zeros
function bits2str(bits, data, mask)
@{
if (bits == 0)
return "0"
mask = 1
for (; bits != 0; bits = rshift(bits, 1))
data = (and(bits, mask) ? "1" : "0") data
while ((length(data) % 8) != 0)
data = "0" data
return data
@}
@c endfile
@end ignore
@c file eg/prog/testbits.awk
BEGIN @{
printf "123 = %s\n", bits2str(123)
printf "0123 = %s\n", bits2str(0123)
printf "0x99 = %s\n", bits2str(0x99)
comp = compl(0x99)
printf "compl(0x99) = %#x = %s\n", comp, bits2str(comp)
shift = lshift(0x99, 2)
printf "lshift(0x99, 2) = %#x = %s\n", shift, bits2str(shift)
shift = rshift(0x99, 2)
printf "rshift(0x99, 2) = %#x = %s\n", shift, bits2str(shift)
@}
@c endfile
@end example
@noindent
This program produces the following output when run:
@example
$ @kbd{gawk -f testbits.awk}
@print{} 123 = 01111011
@print{} 0123 = 01010011
@print{} 0x99 = 10011001
@print{} compl(0x99) = 0x3fffffffffff66 =
@print{} 00111111111111111111111111111111111111111111111101100110
@print{} lshift(0x99, 2) = 0x264 = 0000001001100100
@print{} rshift(0x99, 2) = 0x26 = 00100110
@end example
@cindex converting @subentry string to numbers
@cindex strings @subentry converting
@cindex numbers @subentry converting
@cindex converting @subentry numbers to strings
@cindex numbers @subentry as string of bits
The @code{bits2str()} function turns a binary number into a string.
Initializing @code{mask} to one creates
a binary value where the rightmost bit
is set to one. Using this mask,
the function repeatedly checks the rightmost bit.
ANDing the mask with the value indicates whether the
rightmost bit is one or not. If so, a @code{"1"} is concatenated onto the front
of the string.
Otherwise, a @code{"0"} is added.
The value is then shifted right by one bit and the loop continues
until there are no more one bits.
If the initial value is zero, it returns a simple @code{"0"}.
Otherwise, at the end, it pads the value with zeros to represent multiples
of 8-bit quantities. This is typical in modern computers.
The main code in the @code{BEGIN} rule shows the difference between the
decimal and octal values for the same numbers
(@pxref{Nondecimal-numbers}),
and then demonstrates the
results of the @code{compl()}, @code{lshift()}, and @code{rshift()} functions.
@cindex sidebar @subentry Beware The Smoke and Mirrors!
@ifdocbook
@docbook
<sidebar><title>Beware The Smoke and Mirrors!</title>
@end docbook
It other languages, bitwise operations are performed on integer values,
not floating-point values. As a general statement, such operations work
best when performed on unsigned integers.
@command{gawk} attempts to treat the arguments to the bitwise functions
as unsigned integers. For this reason, negative arguments produce a
fatal error.
In normal operation, for all of these functions, first the
double-precision floating-point value is converted to the widest C
unsigned integer type, then the bitwise operation is performed. If the
result cannot be represented exactly as a C @code{double}, leading
nonzero bits are removed one by one until it can be represented exactly.
The result is then converted back into a C @code{double}.@footnote{If you don't
understand this paragraph, the upshot is that @command{gawk} can only
store a particular range of integer values; numbers outside that range
are reduced to fit within the range.}
However, when using arbitrary precision arithmetic with the @option{-M}
option (@pxref{Arbitrary Precision Arithmetic}), the results may differ.
This is particularly noticeable with the @code{compl()} function:
@example
$ @kbd{gawk 'BEGIN @{ print compl(42) @}'}
@print{} 9007199254740949
$ @kbd{gawk -M 'BEGIN @{ print compl(42) @}'}
@print{} -43
@end example
What's going on becomes clear when printing the results
in hexadecimal:
@example
$ @kbd{gawk 'BEGIN @{ printf "%#x\n", compl(42) @}'}
@print{} 0x1fffffffffffd5
$ @kbd{gawk -M 'BEGIN @{ printf "%#x\n", compl(42) @}'}
@print{} 0xffffffffffffffd5
@end example
When using the @option{-M} option, under the hood, @command{gawk} uses
GNU MP arbitrary precision integers which have at least 64 bits of precision.
When not using @option{-M}, @command{gawk} stores integral values in
regular double-precision floating point, which only maintain 53 bits of
precision. Furthermore, the GNU MP library treats (or at least seems to treat)
the leading bit as a sign bit; thus the result with @option{-M} in this case is
a negative number.
In short, using @command{gawk} for any but the simplest kind of bitwise
operations is probably a bad idea; caveat emptor!
@docbook
</sidebar>
@end docbook
@end ifdocbook
@ifnotdocbook
@cartouche
@center @b{Beware The Smoke and Mirrors!}
It other languages, bitwise operations are performed on integer values,
not floating-point values. As a general statement, such operations work
best when performed on unsigned integers.
@command{gawk} attempts to treat the arguments to the bitwise functions
as unsigned integers. For this reason, negative arguments produce a
fatal error.
In normal operation, for all of these functions, first the
double-precision floating-point value is converted to the widest C
unsigned integer type, then the bitwise operation is performed. If the
result cannot be represented exactly as a C @code{double}, leading
nonzero bits are removed one by one until it can be represented exactly.
The result is then converted back into a C @code{double}.@footnote{If you don't
understand this paragraph, the upshot is that @command{gawk} can only
store a particular range of integer values; numbers outside that range
are reduced to fit within the range.}
However, when using arbitrary precision arithmetic with the @option{-M}
option (@pxref{Arbitrary Precision Arithmetic}), the results may differ.
This is particularly noticeable with the @code{compl()} function:
@example
$ @kbd{gawk 'BEGIN @{ print compl(42) @}'}
@print{} 9007199254740949
$ @kbd{gawk -M 'BEGIN @{ print compl(42) @}'}
@print{} -43
@end example
What's going on becomes clear when printing the results
in hexadecimal:
@example
$ @kbd{gawk 'BEGIN @{ printf "%#x\n", compl(42) @}'}
@print{} 0x1fffffffffffd5
$ @kbd{gawk -M 'BEGIN @{ printf "%#x\n", compl(42) @}'}
@print{} 0xffffffffffffffd5
@end example
When using the @option{-M} option, under the hood, @command{gawk} uses
GNU MP arbitrary precision integers which have at least 64 bits of precision.
When not using @option{-M}, @command{gawk} stores integral values in
regular double-precision floating point, which only maintain 53 bits of
precision. Furthermore, the GNU MP library treats (or at least seems to treat)
the leading bit as a sign bit; thus the result with @option{-M} in this case is
a negative number.
In short, using @command{gawk} for any but the simplest kind of bitwise
operations is probably a bad idea; caveat emptor!
@end cartouche
@end ifnotdocbook
@node Type Functions
@subsection Getting Type Information
@command{gawk} provides two functions that let you distinguish
the type of a variable.
This is necessary for writing code
that traverses every element of an array of arrays
(@pxref{Arrays of Arrays}), and in other contexts.
@table @code
@cindexgawkfunc{isarray}
@cindex scalar or array
@item isarray(@var{x})
Return a true value if @var{x} is an array. Otherwise, return false.
@cindexgawkfunc{typeof}
@cindex variable type, @code{typeof()} function (@command{gawk})
@cindex type @subentry of variable, @code{typeof()} function (@command{gawk})
@item typeof(@var{x})
Return one of the following strings, depending upon the type of @var{x}:
@c nested table
@table @code
@item "array"
@var{x} is an array.
@item "regexp"
@var{x} is a strongly typed regexp (@pxref{Strong Regexp Constants}).
@item "number"
@var{x} is a number.
@item "string"
@var{x} is a string.
@item "strnum"
@var{x} is a number that started life as user input, such as a field or
the result of calling @code{split()}. (I.e., @var{x} has the strnum
attribute; @pxref{Variable Typing}.)
@item "unassigned"
@var{x} is a scalar variable that has not been assigned a value yet.
For example:
@example
BEGIN @{
# creates a[1] but it has no assigned value
a[1]
print typeof(a[1]) # unassigned
@}
@end example
@item "untyped"
@var{x} has not yet been used yet at all; it can become a scalar or an
array. The typing could even conceivably differ from run to run of
the same program! For example:
@example
BEGIN @{
print "initially, typeof(v) = ", typeof(v)
if ("FOO" in ENVIRON)
make_scalar(v)
else
make_array(v)
print "typeof(v) =", typeof(v)
@}
function make_scalar(p, l) @{ l = p @}
function make_array(p) @{ p[1] = 1 @}
@end example
@end table
@end table
@code{isarray()} is meant for use in two circumstances. The first is when
traversing a multidimensional array: you can test if an element is itself
an array or not. The second is inside the body of a user-defined function
(not discussed yet; @pxref{User-defined}), to test if a parameter is an
array or not.
@quotation NOTE
While you can use @code{isarray()} at the global level to test variables,
doing so makes no sense. Because @emph{you} are the one writing the
program, @emph{you} are supposed to know if your variables are arrays
or not.
@end quotation
The @code{typeof()} function is general; it allows you to determine
if a variable or function parameter is a scalar (number, string,
or strongly typed regexp) or an array.
Normally, passing a variable that has never been used to a built-in
function causes it to become a scalar variable (unassigned).
However, @code{isarray()} and @code{typeof()} are different; they do
not change their arguments from untyped to unassigned.
@node I18N Functions
@subsection String-Translation Functions
@cindex @command{gawk} @subentry string-translation functions
@cindex functions @subentry string-translation
@cindex string-translation functions
@cindex internationalization
@cindex @command{awk} programs @subentry internationalizing
@command{gawk} provides facilities for internationalizing @command{awk} programs.
These include the functions described in the following list.
The descriptions here are purposely brief.
@xref{Internationalization},
for the full story.
Optional parameters are enclosed in square brackets ([ ]):
@table @asis
@cindexgawkfunc{bindtextdomain}
@cindex set directory of message catalogs
@item @code{bindtextdomain(@var{directory}} [@code{,} @var{domain}]@code{)}
Set the directory in which
@command{gawk} will look for message translation files, in case they
will not or cannot be placed in the ``standard'' locations
(e.g., during testing).
It returns the directory in which @var{domain} is ``bound.''
The default @var{domain} is the value of @code{TEXTDOMAIN}.
If @var{directory} is the null string (@code{""}), then
@code{bindtextdomain()} returns the current binding for the
given @var{domain}.
@cindexgawkfunc{dcgettext}
@cindex translate string
@item @code{dcgettext(@var{string}} [@code{,} @var{domain} [@code{,} @var{category}] ]@code{)}
Return the translation of @var{string} in
text domain @var{domain} for locale category @var{category}.
The default value for @var{domain} is the current value of @code{TEXTDOMAIN}.
The default value for @var{category} is @code{"LC_MESSAGES"}.
@cindexgawkfunc{dcngettext}
@item @code{dcngettext(@var{string1}, @var{string2}, @var{number}} [@code{,} @var{domain} [@code{,} @var{category}] ]@code{)}
Return the plural form used for @var{number} of the
translation of @var{string1} and @var{string2} in text domain
@var{domain} for locale category @var{category}. @var{string1} is the
English singular variant of a message, and @var{string2} is the English plural
variant of the same message.
The default value for @var{domain} is the current value of @code{TEXTDOMAIN}.
The default value for @var{category} is @code{"LC_MESSAGES"}.
@end table
@node User-defined
@section User-Defined Functions
@cindex user-defined @subentry functions
@cindex functions @subentry user-defined
Complicated @command{awk} programs can often be simplified by defining
your own functions. User-defined functions can be called just like
built-in ones (@pxref{Function Calls}), but it is up to you to define
them (i.e., to tell @command{awk} what they should do).
@menu
* Definition Syntax:: How to write definitions and what they mean.
* Function Example:: An example function definition and what it
does.
* Function Calling:: Calling user-defined functions.
* Return Statement:: Specifying the value a function returns.
* Dynamic Typing:: How variable types can change at runtime.
@end menu
@node Definition Syntax
@subsection Function Definition Syntax
@quotation
@i{It's entirely fair to say that the awk syntax for local
variable definitions is appallingly awful.}
@author Brian Kernighan
@end quotation
@cindex functions @subentry defining
Definitions of functions can appear anywhere between the rules of an
@command{awk} program. Thus, the general form of an @command{awk} program is
extended to include sequences of rules @emph{and} user-defined function
definitions.
There is no need to put the definition of a function
before all uses of the function. This is because @command{awk} reads the
entire program before starting to execute any of it.
The definition of a function named @var{name} looks like this:
@display
@group
@code{function} @var{name}@code{(}[@var{parameter-list}]@code{)}
@code{@{}
@var{body-of-function}
@code{@}}
@end group
@end display
@cindex names @subentry functions
@cindex functions @subentry names of
@cindex naming issues @subentry functions
@noindent
Here, @var{name} is the name of the function to define. A valid function
name is like a valid variable name: a sequence of letters, digits, and
underscores that doesn't start with a digit.
Here too, only the 52 upper- and lowercase English letters may
be used in a function name.
Within a single @command{awk} program, any particular name can only be
used as a variable, array, or function.
@var{parameter-list} is an optional list of the function's arguments and local
variable names, separated by commas. When the function is called,
the argument names are used to hold the argument values given in
the call.
A function cannot have two parameters with the same name, nor may it
have a parameter with the same name as the function itself.
@quotation CAUTION
According to the POSIX standard, function parameters
cannot have the same name as one of the special predefined variables
(@pxref{Built-in Variables}), nor may a function parameter have the
same name as another function.
Not all versions of @command{awk} enforce
these restrictions.
@command{gawk} always enforces the first restriction.
With @option{--posix} (@pxref{Options}),
it also enforces the second restriction.
@end quotation
Local variables act like the empty string if referenced where a string
value is required, and like zero if referenced where a numeric value
is required. This is the same as the behavior of regular variables that have never been
assigned a value. (There is more to understand about local variables;
@pxref{Dynamic Typing}.)
The @var{body-of-function} consists of @command{awk} statements. It is the
most important part of the definition, because it says what the function
should actually @emph{do}. The argument names exist to give the body a
way to talk about the arguments; local variables exist to give the body
places to keep temporary values.
Argument names are not distinguished syntactically from local variable
names. Instead, the number of arguments supplied when the function is
called determines how many argument variables there are. Thus, if three
argument values are given, the first three names in @var{parameter-list}
are arguments and the rest are local variables.
It follows that if the number of arguments is not the same in all calls
to the function, some of the names in @var{parameter-list} may be
arguments on some occasions and local variables on others. Another
way to think of this is that omitted arguments default to the
null string.
@cindex programming conventions @subentry functions @subentry writing
Usually when you write a function, you know how many names you intend to
use for arguments and how many you intend to use as local variables. It is
conventional to place some extra space between the arguments and
the local variables, in order to document how your function is supposed to be used.
@cindex variables @subentry shadowing
@cindex shadowing of variable values
During execution of the function body, the arguments and local variable
values hide, or @dfn{shadow}, any variables of the same names used in the
rest of the program. The shadowed variables are not accessible in the
function definition, because there is no way to name them while their
names have been taken away for the arguments and local variables. All other variables
used in the @command{awk} program can be referenced or set normally in the
function's body.
The arguments and local variables last only as long as the function body
is executing. Once the body finishes, you can once again access the
variables that were shadowed while the function was running.
@cindex recursive functions
@cindex functions @subentry recursive
The function body can contain expressions that call functions. They
can even call this function, either directly or by way of another
function. When this happens, we say the function is @dfn{recursive}.
The act of a function calling itself is called @dfn{recursion}.
All the built-in functions return a value to their caller.
User-defined functions can do so also, using the @code{return} statement,
which is described in detail in @ref{Return Statement}.
Many of the subsequent examples in this @value{SECTION} use
the @code{return} statement.
@cindex common extensions @subentry @code{func} keyword
@cindex extensions @subentry common @subentry @code{func} keyword
@c @cindex POSIX @command{awk}
@cindex @command{awk} @subentry language, POSIX version
@cindex POSIX @command{awk} @subentry @code{function} keyword in
In many @command{awk} implementations, including @command{gawk},
the keyword @code{function} may be
abbreviated @code{func}. @value{COMMONEXT}
However, POSIX only specifies the use of
the keyword @code{function}. This actually has some practical implications.
If @command{gawk} is in POSIX-compatibility mode
(@pxref{Options}), then the following
statement does @emph{not} define a function:
@example
func foo() @{ a = sqrt($1) ; print a @}
@end example
@noindent
Instead, it defines a rule that, for each record, concatenates the value
of the variable @samp{func} with the return value of the function @samp{foo}.
If the resulting string is non-null, the action is executed.
This is probably not what is desired. (@command{awk} accepts this input as
syntactically valid, because functions may be used before they are defined
in @command{awk} programs.@footnote{This program won't actually run,
because @code{foo()} is undefined.})
@cindex portability @subentry functions, defining
To ensure that your @command{awk} programs are portable, always use the
keyword @code{function} when defining a function.
@node Function Example
@subsection Function Definition Examples
@cindex function definition example
Here is an example of a user-defined function, called @code{myprint()}, that
takes a number and prints it in a specific format:
@example
function myprint(num)
@{
printf "%6.3g\n", num
@}
@end example
@noindent
To illustrate, here is an @command{awk} rule that uses our @code{myprint()}
function:
@example
$3 > 0 @{ myprint($3) @}
@end example
@noindent
This program prints, in our special format, all the third fields that
contain a positive number in our input. Therefore, when given the following input:
@example
1.2 3.4 5.6 7.8
9.10 11.12 -13.14 15.16
17.18 19.20 21.22 23.24
@end example
@noindent
this program, using our function to format the results, prints:
@example
5.6
21.2
@end example
This function deletes all the elements in an array (recall that the
extra whitespace signifies the start of the local variable list):
@example
@group
function delarray(a, i)
@{
for (i in a)
delete a[i]
@}
@end group
@end example
When working with arrays, it is often necessary to delete all the elements
in an array and start over with a new list of elements
(@pxref{Delete}).
Instead of having
to repeat this loop everywhere that you need to clear out
an array, your program can just call @code{delarray()}.
(This guarantees portability. The use of @samp{delete @var{array}} to delete
the contents of an entire array is a relatively recent@footnote{Late in 2012.}
addition to the POSIX standard.)
The following is an example of a recursive function. It takes a string
as an input parameter and returns the string in reverse order.
Recursive functions must always have a test that stops the recursion.
In this case, the recursion terminates when the input string is
already empty:
@c 8/2014: Thanks to Mike Brennan for the improved formulation
@cindex @code{rev()} user-defined function
@cindex user-defined @subentry function @subentry @code{rev()}
@example
function rev(str)
@{
if (str == "")
return ""
return (rev(substr(str, 2)) substr(str, 1, 1))
@}
@end example
If this function is in a file named @file{rev.awk}, it can be tested
this way:
@example
$ @kbd{echo "Don't Panic!" |}
> @kbd{gawk -e '@{ print rev($0) @}' -f rev.awk}
@print{} !cinaP t'noD
@end example
The C @code{ctime()} function takes a timestamp and returns it as a string,
formatted in a well-known fashion.
The following example uses the built-in @code{strftime()} function
(@pxref{Time Functions})
to create an @command{awk} version of @code{ctime()}:
@cindex @code{ctime()} user-defined function
@cindex user-defined @subentry function @subentry @code{ctime()}
@example
@c file eg/lib/ctime.awk
# ctime.awk
#
# awk version of C ctime(3) function
function ctime(ts, format)
@{
format = "%a %b %e %H:%M:%S %Z %Y"
if (ts == 0)
ts = systime() # use current time as default
return strftime(format, ts)
@}
@c endfile
@end example
You might think that @code{ctime()} could use @code{PROCINFO["strftime"]}
for its format string. That would be a mistake, because @code{ctime()} is
supposed to return the time formatted in a standard fashion, and user-level
code could have changed @code{PROCINFO["strftime"]}.
@node Function Calling
@subsection Calling User-Defined Functions
@cindex functions @subentry user-defined @subentry calling
@dfn{Calling a function} means causing the function to run and do its job.
A function call is an expression and its value is the value returned by
the function.
@menu
* Calling A Function:: Don't use spaces.
* Variable Scope:: Controlling variable scope.
* Pass By Value/Reference:: Passing parameters.
* Function Caveats:: Other points to know about functions.
@end menu
@node Calling A Function
@subsubsection Writing a Function Call
A function call consists of the function name followed by the arguments
in parentheses. @command{awk} expressions are what you write in the
call for the arguments. Each time the call is executed, these
expressions are evaluated, and the values become the actual arguments. For
example, here is a call to @code{foo()} with three arguments (the first
being a string concatenation):
@example
foo(x y, "lose", 4 * z)
@end example
@quotation CAUTION
Whitespace characters (spaces and TABs) are not allowed
between the function name and the opening parenthesis of the argument list.
If you write whitespace by mistake, @command{awk} might think that you mean
to concatenate a variable with an expression in parentheses. However, it
notices that you used a function name and not a variable name, and reports
an error.
@end quotation
@node Variable Scope
@subsubsection Controlling Variable Scope
@cindex local variables @subentry in a function
@cindex variables @subentry local to a function
Unlike in many languages,
there is no way to make a variable local to a @code{@{} @dots{} @code{@}} block in
@command{awk}, but you can make a variable local to a function. It is
good practice to do so whenever a variable is needed only in that
function.
To make a variable local to a function, simply declare the variable as
an argument after the actual function arguments
(@pxref{Definition Syntax}).
Look at the following example, where variable
@code{i} is a global variable used by both functions @code{foo()} and
@code{bar()}:
@example
function bar()
@{
for (i = 0; i < 3; i++)
print "bar's i=" i
@}
function foo(j)
@{
i = j + 1
print "foo's i=" i
bar()
print "foo's i=" i
@}
BEGIN @{
i = 10
print "top's i=" i
foo(0)
print "top's i=" i
@}
@end example
Running this script produces the following, because the @code{i} in
functions @code{foo()} and @code{bar()} and at the top level refer to the same
variable instance:
@example
top's i=10
foo's i=1
bar's i=0
bar's i=1
bar's i=2
foo's i=3
top's i=3
@end example
If you want @code{i} to be local to both @code{foo()} and @code{bar()}, do as
follows (the extra space before @code{i} is a coding convention to
indicate that @code{i} is a local variable, not an argument):
@example
function bar( i)
@{
for (i = 0; i < 3; i++)
print "bar's i=" i
@}
function foo(j, i)
@{
i = j + 1
print "foo's i=" i
bar()
print "foo's i=" i
@}
BEGIN @{
i = 10
print "top's i=" i
foo(0)
print "top's i=" i
@}
@end example
Running the corrected script produces the following:
@example
top's i=10
foo's i=1
bar's i=0
bar's i=1
bar's i=2
foo's i=1
top's i=10
@end example
Besides scalar values (strings and numbers), you may also have
local arrays. By using a parameter name as an array, @command{awk}
treats it as an array, and it is local to the function.
In addition, recursive calls create new arrays.
Consider this example:
@example
@group
function some_func(p1, a)
@{
if (p1++ > 3)
return
@end group
a[p1] = p1
some_func(p1)
printf("At level %d, index %d %s found in a\n",
p1, (p1 - 1), (p1 - 1) in a ? "is" : "is not")
printf("At level %d, index %d %s found in a\n",
p1, p1, p1 in a ? "is" : "is not")
print ""
@}
BEGIN @{
some_func(1)
@}
@end example
When run, this program produces the following output:
@example
At level 4, index 3 is not found in a
At level 4, index 4 is found in a
At level 3, index 2 is not found in a
At level 3, index 3 is found in a
At level 2, index 1 is not found in a
At level 2, index 2 is found in a
@end example
@node Pass By Value/Reference
@subsubsection Passing Function Arguments by Value Or by Reference
In @command{awk}, when you declare a function, there is no way to
declare explicitly whether the arguments are passed @dfn{by value} or
@dfn{by reference}.
Instead, the passing convention is determined at runtime when
the function is called, according to the following rule:
if the argument is an array variable, then it is passed by reference.
Otherwise, the argument is passed by value.
@cindex call by value
Passing an argument by value means that when a function is called, it
is given a @emph{copy} of the value of this argument.
The caller may use a variable as the expression for the argument, but
the called function does not know this---it only knows what value the
argument had. For example, if you write the following code:
@example
foo = "bar"
z = myfunc(foo)
@end example
@noindent
then you should not think of the argument to @code{myfunc()} as being
``the variable @code{foo}.'' Instead, think of the argument as the
string value @code{"bar"}.
If the function @code{myfunc()} alters the values of its local variables,
this has no effect on any other variables. Thus, if @code{myfunc()}
does this:
@example
@group
function myfunc(str)
@{
print str
str = "zzz"
print str
@}
@end group
@end example
@noindent
to change its first argument variable @code{str}, it does @emph{not}
change the value of @code{foo} in the caller. The role of @code{foo} in
calling @code{myfunc()} ended when its value (@code{"bar"}) was computed.
If @code{str} also exists outside of @code{myfunc()}, the function body
cannot alter this outer value, because it is shadowed during the
execution of @code{myfunc()} and cannot be seen or changed from there.
@cindex call by reference
@cindex arrays @subentry as parameters to functions
@cindex functions @subentry arrays as parameters to
However, when arrays are the parameters to functions, they are @emph{not}
copied. Instead, the array itself is made available for direct manipulation
by the function. This is usually termed @dfn{call by reference}.
Changes made to an array parameter inside the body of a function @emph{are}
visible outside that function.
@quotation NOTE
Changing an array parameter inside a function
can be very dangerous if you do not watch what you are doing.
For example:
@example
function changeit(array, ind, nvalue)
@{
array[ind] = nvalue
@}
BEGIN @{
a[1] = 1; a[2] = 2; a[3] = 3
changeit(a, 2, "two")
printf "a[1] = %s, a[2] = %s, a[3] = %s\n",
a[1], a[2], a[3]
@}
@end example
@noindent
prints @samp{a[1] = 1, a[2] = two, a[3] = 3}, because
@code{changeit()} stores @code{"two"} in the second element of @code{a}.
@end quotation
@node Function Caveats
@subsubsection Other Points About Calling Functions
@cindex undefined functions
@cindex functions @subentry undefined
Some @command{awk} implementations allow you to call a function that
has not been defined. They only report a problem at runtime, when the
program actually tries to call the function. For example:
@example
BEGIN @{
if (0)
foo()
else
bar()
@}
function bar() @{ @dots{} @}
# note that `foo' is not defined
@end example
@noindent
Because the @samp{if} statement will never be true, it is not really a
problem that @code{foo()} has not been defined. Usually, though, it is a
problem if a program calls an undefined function.
@cindex lint checking @subentry undefined functions
If @option{--lint} is specified
(@pxref{Options}),
@command{gawk} reports calls to undefined functions.
@cindex portability @subentry @code{next} statement in user-defined functions
Some @command{awk} implementations generate a runtime
error if you use either the @code{next} statement
or the @code{nextfile} statement
(@pxref{Next Statement}, and
@ifdocbook
@ref{Nextfile Statement})
@end ifdocbook
@ifnotdocbook
@pxref{Nextfile Statement})
@end ifnotdocbook
inside a user-defined function.
@command{gawk} does not have this limitation.
You can call a function and pass it more parameters than it was declared
with, like so:
@example
function foo(p1, p2)
@{
@dots{}
@}
BEGIN @{
foo(1, 2, 3, 4)
@}
@end example
Doing so is bad practice, however. The called function cannot do
anything with the additional values being passed to it, so @command{awk}
evaluates the expressions but then just throws them away.
More importantly, such a call is confusing for whoever will next read your
program.@footnote{Said person might even be you, sometime in the future,
at which point you will wonder, ``what was I thinking?!?''} Function
parameters generally are input items that influence the computation
performed by the function. Calling a function with more parameters than
it accepts gives the false impression that those values are important
to the function, when in fact they are not.
Because this is such a bad practice, @command{gawk} @emph{unconditionally}
issues a warning whenever it executes such a function call. (If you
don't like the warning, fix your code! It's incorrect, after all.)
@node Return Statement
@subsection The @code{return} Statement
@cindex @code{return} statement, user-defined functions
As seen in several earlier examples,
the body of a user-defined function can contain a @code{return} statement.
This statement returns control to the calling part of the @command{awk} program. It
can also be used to return a value for use in the rest of the @command{awk}
program. It looks like this:
@display
@code{return} [@var{expression}]
@end display
The @var{expression} part is optional.
Due most likely to an oversight, POSIX does not define what the return
value is if you omit the @var{expression}. Technically speaking, this
makes the returned value undefined, and therefore, unpredictable.
In practice, though, all versions of @command{awk} simply return the
null string, which acts like zero if used in a numeric context.
A @code{return} statement without an @var{expression} is assumed at the end of
every function definition. So, if control reaches the end of the function
body, then technically the function returns an unpredictable value.
In practice, it returns the empty string. @command{awk}
does @emph{not} warn you if you use the return value of such a function.
Sometimes, you want to write a function for what it does, not for
what it returns. Such a function corresponds to a @code{void} function
in C, C++, or Java, or to a @code{procedure} in Ada. Thus, it may be appropriate to not
return any value; simply bear in mind that you should not be using the
return value of such a function.
The following is an example of a user-defined function that returns a value
for the largest number among the elements of an array:
@example
function maxelt(vec, i, ret)
@{
for (i in vec) @{
if (ret == "" || vec[i] > ret)
ret = vec[i]
@}
return ret
@}
@end example
@cindex programming conventions @subentry function parameters
@noindent
You call @code{maxelt()} with one argument, which is an array name. The local
variables @code{i} and @code{ret} are not intended to be arguments;
there is nothing to stop you from passing more than one argument
to @code{maxelt()} but the results would be strange. The extra space before
@code{i} in the function parameter list indicates that @code{i} and
@code{ret} are local variables.
You should follow this convention when defining functions.
The following program uses the @code{maxelt()} function. It loads an
array, calls @code{maxelt()}, and then reports the maximum number in that
array:
@example
function maxelt(vec, i, ret)
@{
for (i in vec) @{
if (ret == "" || vec[i] > ret)
ret = vec[i]
@}
return ret
@}
@group
# Load all fields of each record into nums.
@{
for(i = 1; i <= NF; i++)
nums[NR, i] = $i
@}
@end group
END @{
print maxelt(nums)
@}
@end example
Given the following input:
@example
1 5 23 8 16
44 3 5 2 8 26
256 291 1396 2962 100
-6 467 998 1101
99385 11 0 225
@end example
@noindent
the program reports (predictably) that 99,385 is the largest value
in the array.
@node Dynamic Typing
@subsection Functions and Their Effects on Variable Typing
@command{awk} is a very fluid language.
It is possible that @command{awk} can't tell if an identifier
represents a scalar variable or an array until runtime.
Here is an annotated sample program:
@example
function foo(a)
@{
a[1] = 1 # parameter is an array
@}
BEGIN @{
b = 1
foo(b) # invalid: fatal type mismatch
foo(x) # x uninitialized, becomes an array dynamically
x = 1 # now not allowed, runtime error
@}
@end example
In this example, the first call to @code{foo()} generates
a fatal error, so @command{awk} will not report the second
error. If you comment out that call, though, then @command{awk}
does report the second error.
Usually, such things aren't a big issue, but it's worth
being aware of them.
@node Indirect Calls
@section Indirect Function Calls
@cindex indirect function calls
@cindex function calls @subentry indirect
@cindex function pointers
@cindex pointers to functions
@cindex differences in @command{awk} and @command{gawk} @subentry indirect function calls
This section describes an advanced, @command{gawk}-specific extension.
Often, you may wish to defer the choice of function to call until runtime.
For example, you may have different kinds of records, each of which
should be processed differently.
Normally, you would have to use a series of @code{if}-@code{else}
statements to decide which function to call. By using @dfn{indirect}
function calls, you can specify the name of the function to call as a
string variable, and then call the function. Let's look at an example.
Suppose you have a file with your test scores for the classes you
are taking, and
you wish to get the sum and the average of
your test scores.
The first field is the class name. The following fields
are the functions to call to process the data, up to a ``marker''
field @samp{data:}. Following the marker, to the end of the record,
are the various numeric test scores.
Here is the initial file:
@example
@c file eg/data/class_data1
Biology_101 sum average data: 87.0 92.4 78.5 94.9
Chemistry_305 sum average data: 75.2 98.3 94.7 88.2
English_401 sum average data: 100.0 95.6 87.1 93.4
@c endfile
@end example
To process the data, you might write initially:
@example
@{
class = $1
for (i = 2; $i != "data:"; i++) @{
if ($i == "sum")
sum() # processes the whole record
else if ($i == "average")
average()
@dots{} # and so on
@}
@}
@end example
@noindent
This style of programming works, but can be awkward. With @dfn{indirect}
function calls, you tell @command{gawk} to use the @emph{value} of a
variable as the @emph{name} of the function to call.
@cindex @code{@@} (at-sign) @subentry @code{@@}-notation for indirect function calls
@cindex at-sign (@code{@@}) @subentry @code{@@}-notation for indirect function calls
@cindex indirect function calls @subentry @code{@@}-notation
@cindex function calls @subentry indirect @subentry @code{@@}-notation for
The syntax is similar to that of a regular function call: an identifier
immediately followed by an opening parenthesis, any arguments, and then
a closing parenthesis, with the addition of a leading @samp{@@}
character:
@example
the_func = "sum"
result = @@the_func() # calls the sum() function
@end example
Here is a full program that processes the previously shown data,
using indirect function calls:
@example
@c file eg/prog/indirectcall.awk
# indirectcall.awk --- Demonstrate indirect function calls
@c endfile
@ignore
@c file eg/prog/indirectcall.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# January 2009
@c endfile
@end ignore
@c file eg/prog/indirectcall.awk
# average --- return the average of the values in fields $first - $last
function average(first, last, sum, i)
@{
sum = 0;
for (i = first; i <= last; i++)
sum += $i
return sum / (last - first + 1)
@}
# sum --- return the sum of the values in fields $first - $last
function sum(first, last, ret, i)
@{
ret = 0;
for (i = first; i <= last; i++)
ret += $i
return ret
@}
@c endfile
@end example
These two functions expect to work on fields; thus, the parameters
@code{first} and @code{last} indicate where in the fields to start and end.
Otherwise, they perform the expected computations and are not unusual:
@example
@c file eg/prog/indirectcall.awk
# For each record, print the class name and the requested statistics
@{
class_name = $1
gsub(/_/, " ", class_name) # Replace _ with spaces
# find start
for (i = 1; i <= NF; i++) @{
if ($i == "data:") @{
start = i + 1
break
@}
@}
printf("%s:\n", class_name)
for (i = 2; $i != "data:"; i++) @{
the_function = $i
printf("\t%s: <%s>\n", $i, @@the_function(start, NF) "")
@}
print ""
@}
@c endfile
@end example
This is the main processing for each record. It prints the class name (with
underscores replaced with spaces). It then finds the start of the actual data,
saving it in @code{start}.
The last part of the code loops through each function name (from @code{$2} up to
the marker, @samp{data:}), calling the function named by the field. The indirect
function call itself occurs as a parameter in the call to @code{printf}.
(The @code{printf} format string uses @samp{%s} as the format specifier so that we
can use functions that return strings, as well as numbers. Note that the result
from the indirect call is concatenated with the empty string, in order to force
it to be a string value.)
Here is the result of running the program:
@example
$ @kbd{gawk -f indirectcall.awk class_data1}
@print{} Biology 101:
@print{} sum: <352.8>
@print{} average: <88.2>
@print{}
@print{} Chemistry 305:
@print{} sum: <356.4>
@print{} average: <89.1>
@print{}
@print{} English 401:
@print{} sum: <376.1>
@print{} average: <94.025>
@end example
The ability to use indirect function calls is more powerful than you may
think at first. The C and C++ languages provide ``function pointers,'' which
are a mechanism for calling a function chosen at runtime. One of the most
well-known uses of this ability is the C @code{qsort()} function, which sorts
an array using the famous ``quicksort'' algorithm
(see @uref{https://en.wikipedia.org/wiki/Quicksort, the Wikipedia article}
for more information). To use this function, you supply a pointer to a comparison
function. This mechanism allows you to sort arbitrary data in an arbitrary
fashion.
We can do something similar using @command{gawk}, like this:
@example
@c file eg/lib/quicksort.awk
# quicksort.awk --- Quicksort algorithm, with user-supplied
# comparison function
@c endfile
@ignore
@c file eg/lib/quicksort.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# January 2009
@c endfile
@end ignore
@c file eg/lib/quicksort.awk
# quicksort --- C.A.R. Hoare's quicksort algorithm. See Wikipedia
# or almost any algorithms or computer science text.
@c endfile
@ignore
@c file eg/lib/quicksort.awk
#
# Adapted from K&R-II, page 110
@c endfile
@end ignore
@c file eg/lib/quicksort.awk
function quicksort(data, left, right, less_than, i, last)
@{
if (left >= right) # do nothing if array contains fewer
return # than two elements
quicksort_swap(data, left, int((left + right) / 2))
last = left
for (i = left + 1; i <= right; i++)
if (@@less_than(data[i], data[left]))
quicksort_swap(data, ++last, i)
quicksort_swap(data, left, last)
quicksort(data, left, last - 1, less_than)
quicksort(data, last + 1, right, less_than)
@}
# quicksort_swap --- helper function for quicksort, should really be inline
function quicksort_swap(data, i, j, temp)
@{
temp = data[i]
data[i] = data[j]
data[j] = temp
@}
@c endfile
@end example
The @code{quicksort()} function receives the @code{data} array, the starting and ending
indices to sort (@code{left} and @code{right}), and the name of a function that
performs a ``less than'' comparison. It then implements the quicksort algorithm.
To make use of the sorting function, we return to our previous example. The
first thing to do is write some comparison functions:
@example
@c file eg/prog/indirectcall.awk
@group
# num_lt --- do a numeric less than comparison
function num_lt(left, right)
@{
return ((left + 0) < (right + 0))
@}
@end group
# num_ge --- do a numeric greater than or equal to comparison
function num_ge(left, right)
@{
return ((left + 0) >= (right + 0))
@}
@c endfile
@end example
The @code{num_ge()} function is needed to perform a descending sort; when used
to perform a ``less than'' test, it actually does the opposite (greater than
or equal to), which yields data sorted in descending order.
Next comes a sorting function. It is parameterized with the starting and
ending field numbers and the comparison function. It builds an array with
the data and calls @code{quicksort()} appropriately, and then formats the
results as a single string:
@example
@c file eg/prog/indirectcall.awk
# do_sort --- sort the data according to `compare'
# and return it as a string
function do_sort(first, last, compare, data, i, retval)
@{
delete data
for (i = 1; first <= last; first++) @{
data[i] = $first
i++
@}
quicksort(data, 1, i-1, compare)
retval = data[1]
for (i = 2; i in data; i++)
retval = retval " " data[i]
return retval
@}
@c endfile
@end example
Finally, the two sorting functions call @code{do_sort()}, passing in the
names of the two comparison functions:
@example
@c file eg/prog/indirectcall.awk
@group
# sort --- sort the data in ascending order and return it as a string
function sort(first, last)
@{
return do_sort(first, last, "num_lt")
@}
@end group
@group
# rsort --- sort the data in descending order and return it as a string
function rsort(first, last)
@{
return do_sort(first, last, "num_ge")
@}
@end group
@c endfile
@end example
Here is an extended version of the @value{DF}:
@example
@c file eg/data/class_data2
Biology_101 sum average sort rsort data: 87.0 92.4 78.5 94.9
Chemistry_305 sum average sort rsort data: 75.2 98.3 94.7 88.2
English_401 sum average sort rsort data: 100.0 95.6 87.1 93.4
@c endfile
@end example
Finally, here are the results when the enhanced program is run:
@example
$ @kbd{gawk -f quicksort.awk -f indirectcall.awk class_data2}
@print{} Biology 101:
@print{} sum: <352.8>
@print{} average: <88.2>
@print{} sort: <78.5 87.0 92.4 94.9>
@print{} rsort: <94.9 92.4 87.0 78.5>
@print{}
@print{} Chemistry 305:
@print{} sum: <356.4>
@print{} average: <89.1>
@print{} sort: <75.2 88.2 94.7 98.3>
@print{} rsort: <98.3 94.7 88.2 75.2>
@print{}
@print{} English 401:
@print{} sum: <376.1>
@print{} average: <94.025>
@print{} sort: <87.1 93.4 95.6 100.0>
@print{} rsort: <100.0 95.6 93.4 87.1>
@end example
Another example where indirect functions calls are useful can be found in
processing arrays. This is described in @ref{Walking Arrays}.
Remember that you must supply a leading @samp{@@} in front of an indirect function call.
Starting with @value{PVERSION} 4.1.2 of @command{gawk}, indirect function
calls may also be used with built-in functions and with extension functions
(@pxref{Dynamic Extensions}). There are some limitations when calling
built-in functions indirectly, as follows.
@itemize @value{BULLET}
@item
You cannot pass a regular expression constant to a built-in function
through an indirect function call.@footnote{This may change in a future
version; recheck the documentation that comes with your version of
@command{gawk} to see if it has.} This applies to the @code{sub()},
@code{gsub()}, @code{gensub()}, @code{match()}, @code{split()} and
@code{patsplit()} functions.
@item
If calling @code{sub()} or @code{gsub()}, you may only pass two arguments,
since those functions are unusual in that they update their third argument.
This means that @code{$0} will be updated.
@end itemize
@command{gawk} does its best to make indirect function calls efficient.
For example, in the following case:
@example
for (i = 1; i <= n; i++)
@@the_func()
@end example
@noindent
@command{gawk} looks up the actual function to call only once.
@node Functions Summary
@section Summary
@itemize @value{BULLET}
@item
@command{awk} provides built-in functions and lets you define your own
functions.
@item
POSIX @command{awk} provides three kinds of built-in functions: numeric,
string, and I/O. @command{gawk} provides functions that sort arrays, work
with values representing time, do bit manipulation, determine variable
type (array versus scalar), and internationalize and localize programs.
@command{gawk} also provides several extensions to some of standard
functions, typically in the form of additional arguments.
@item
Functions accept zero or more arguments and return a value. The
expressions that provide the argument values are completely evaluated
before the function is called. Order of evaluation is not defined.
The return value can be ignored.
@item
The handling of backslash in @code{sub()} and @code{gsub()} is not simple.
It is more straightforward in @command{gawk}'s @code{gensub()} function,
but that function still requires care in its use.
@item
User-defined functions provide important capabilities but come with
some syntactic inelegancies. In a function call, there cannot be any
space between the function name and the opening left parenthesis of the
argument list. Also, there is no provision for local variables, so the
convention is to add extra parameters, and to separate them visually
from the real parameters by extra whitespace.
@item
User-defined functions may call other user-defined (and built-in)
functions and may call themselves recursively. Function parameters
``hide'' any global variables of the same names.
You cannot use the name of a reserved variable (such as @code{ARGC})
as the name of a parameter in user-defined functions.
@item
Scalar values are passed to user-defined functions by value. Array
parameters are passed by reference; any changes made by the function to
array parameters are thus visible after the function has returned.
@item
Use the @code{return} statement to return from a user-defined function.
An optional expression becomes the function's return value. Only scalar
values may be returned by a function.
@item
If a variable that has never been used is passed to a user-defined
function, how that function treats the variable can set its nature:
either scalar or array.
@item
@command{gawk} provides indirect function calls using a special syntax.
By setting a variable to the name of a function, you can
determine at runtime what function will be called at that point in the
program. This is equivalent to function pointers in C and C++.
@end itemize
@ifnotinfo
@part @value{PART2}Problem Solving with @command{awk}
@end ifnotinfo
@ifdocbook
Part II shows how to use @command{awk} and @command{gawk} for problem solving.
There is lots of code here for you to read and learn from.
It contains the following chapters:
@itemize @value{BULLET}
@item
@ref{Library Functions}
@item
@ref{Sample Programs}
@end itemize
@end ifdocbook
@node Library Functions
@chapter A Library of @command{awk} Functions
@cindex libraries of @command{awk} functions
@cindex functions @subentry library
@cindex functions @subentry user-defined @subentry library of
@ref{User-defined} describes how to write
your own @command{awk} functions. Writing functions is important, because
it allows you to encapsulate algorithms and program tasks in a single
place. It simplifies programming, making program development more
manageable and making programs more readable.
@cindex Kernighan, Brian
@cindex Plauger, P.J.@:
In their seminal 1976 book, @cite{Software Tools},@footnote{Sadly, over 35
years later, many of the lessons taught by this book have yet to be
learned by a vast number of practicing programmers.} Brian Kernighan
and P.J.@: Plauger wrote:
@quotation
Good Programming is not learned from generalities, but by seeing how
significant programs can be made clean, easy to read, easy to maintain and
modify, human-engineered, efficient and reliable, by the application of
common sense and good programming practices. Careful study and imitation
of good programs leads to better writing.
@end quotation
In fact, they felt this idea was so important that they placed this
statement on the cover of their book. Because we believe strongly
that their statement is correct, this @value{CHAPTER} and @ref{Sample
Programs}, provide a good-sized body of code for you to read and, we hope,
to learn from.
This @value{CHAPTER} presents a library of useful @command{awk} functions.
Many of the sample programs presented later in this @value{DOCUMENT}
use these functions.
The functions are presented here in a progression from simple to complex.
@cindex Texinfo
@ref{Extract Program}
presents a program that you can use to extract the source code for
these example library functions and programs from the Texinfo source
for this @value{DOCUMENT}.
(This has already been done as part of the @command{gawk} distribution.)
@ifclear FOR_PRINT
If you have written one or more useful, general-purpose @command{awk} functions
and would like to contribute them to the @command{awk} user community, see
@ref{How To Contribute}, for more information.
@end ifclear
@cindex portability @subentry example programs
The programs in this @value{CHAPTER} and in
@ref{Sample Programs},
freely use @command{gawk}-specific features.
Rewriting these programs for different implementations of @command{awk}
is pretty straightforward:
@itemize @value{BULLET}
@item
Diagnostic error messages are sent to @file{/dev/stderr}.
Use @samp{| "cat 1>&2"} instead of @samp{> "/dev/stderr"} if your system
does not have a @file{/dev/stderr}, or if you cannot use @command{gawk}.
@item
A number of programs use @code{nextfile}
(@pxref{Nextfile Statement})
to skip any remaining input in the input file.
@item
@c 12/2000: Thanks to Nelson Beebe for pointing out the output issue.
@cindex case sensitivity @subentry example programs
@cindex @code{IGNORECASE} variable @subentry in example programs
Finally, some of the programs choose to ignore upper- and lowercase
distinctions in their input. They do so by assigning one to @code{IGNORECASE}.
You can achieve almost the same effect@footnote{The effects are
not identical. Output of the transformed
record will be in all lowercase, while @code{IGNORECASE} preserves the original
contents of the input record.} by adding the following rule to the
beginning of the program:
@example
# ignore case
@{ $0 = tolower($0) @}
@end example
@noindent
Also, verify that all regexp and string constants used in
comparisons use only lowercase letters.
@end itemize
@menu
* Library Names:: How to best name private global variables in
library functions.
* General Functions:: Functions that are of general use.
* Data File Management:: Functions for managing command-line data
files.
* Getopt Function:: A function for processing command-line
arguments.
* Passwd Functions:: Functions for getting user information.
* Group Functions:: Functions for getting group information.
* Walking Arrays:: A function to walk arrays of arrays.
* Library Functions Summary:: Summary of library functions.
* Library Exercises:: Exercises.
@end menu
@node Library Names
@section Naming Library Function Global Variables
@cindex names @subentry arrays/variables
@cindex names @subentry functions
@cindex naming issues
@cindex @command{awk} programs @subentry documenting
@cindex documentation @subentry of @command{awk} programs
Due to the way the @command{awk} language evolved, variables are either
@dfn{global} (usable by the entire program) or @dfn{local} (usable just by
a specific function). There is no intermediate state analogous to
@code{static} variables in C.
@cindex variables @subentry global @subentry for library functions
@cindex private variables
@cindex variables @subentry private
Library functions often need to have global variables that they can use to
preserve state information between calls to the function---for example,
@code{getopt()}'s variable @code{_opti}
(@pxref{Getopt Function}).
Such variables are called @dfn{private}, as the only functions that need to
use them are the ones in the library.
When writing a library function, you should try to choose names for your
private variables that will not conflict with any variables used by
either another library function or a user's main program. For example, a
name like @code{i} or @code{j} is not a good choice, because user programs
often use variable names like these for their own purposes.
@cindex programming conventions @subentry private variable names
The example programs shown in this @value{CHAPTER} all start the names of their
private variables with an underscore (@samp{_}). Users generally don't use
leading underscores in their variable names, so this convention immediately
decreases the chances that the variable names will be accidentally shared
with the user's program.
@cindex @code{_} (underscore) @subentry in names of private variables
@cindex underscore (@code{_}) @subentry in names of private variables
In addition, several of the library functions use a prefix that helps
indicate what function or set of functions use the variables---for example,
@code{_pw_byname()} in the user database routines
(@pxref{Passwd Functions}).
This convention is recommended, as it even further decreases the
chance of inadvertent conflict among variable names. Note that this
convention is used equally well for variable names and for private
function names.@footnote{Although all the library routines could have
been rewritten to use this convention, this was not done, in order to
show how our own @command{awk} programming style has evolved and to
provide some basis for this discussion.}
As a final note on variable naming, if a function makes global variables
available for use by a main program, it is a good convention to start those
variables' names with a capital letter---for
example, @code{getopt()}'s @code{Opterr} and @code{Optind} variables
(@pxref{Getopt Function}).
The leading capital letter indicates that it is global, while the fact that
the variable name is not all capital letters indicates that the variable is
not one of @command{awk}'s predefined variables, such as @code{FS}.
@cindex @option{--dump-variables} option @subentry using for library functions
It is also important that @emph{all} variables in library
functions that do not need to save state are, in fact, declared
local.@footnote{@command{gawk}'s @option{--dump-variables} command-line
option is useful for verifying this.} If this is not done, the variables
could accidentally be used in the user's program, leading to bugs that
are very difficult to track down:
@example
function lib_func(x, y, l1, l2)
@{
@dots{}
# some_var should be local but by oversight is not
@var{use variable} some_var
@dots{}
@}
@end example
@cindex arrays @subentry associative @subentry library functions and
@cindex libraries of @command{awk} functions @subentry associative arrays and
@cindex functions @subentry library @subentry associative arrays and
@cindex Tcl
A different convention, common in the Tcl community, is to use a single
associative array to hold the values needed by the library function(s), or
``package.'' This significantly decreases the number of actual global names
in use. For example, the functions described in
@ref{Passwd Functions}
might have used array elements @code{@w{PW_data["inited"]}}, @code{@w{PW_data["total"]}},
@code{@w{PW_data["count"]}}, and @code{@w{PW_data["awklib"]}}, instead of
@code{@w{_pw_inited}}, @code{@w{_pw_awklib}}, @code{@w{_pw_total}},
and @code{@w{_pw_count}}.
The conventions presented in this @value{SECTION} are exactly
that: conventions. You are not required to write your programs this
way---we merely recommend that you do so.
Beginning with @value{PVERSION} 5.0, @command{gawk} provides
a powerful mechanism for solving the problems described in this
section: @dfn{namespaces}. Namespaces and their use are described
in detail in @ref{Namespaces}.
@node General Functions
@section General Programming
This @value{SECTION} presents a number of functions that are of general
programming use.
@menu
* Strtonum Function:: A replacement for the built-in
@code{strtonum()} function.
* Assert Function:: A function for assertions in @command{awk}
programs.
* Round Function:: A function for rounding if @code{sprintf()}
does not do it correctly.
* Cliff Random Function:: The Cliff Random Number Generator.
* Ordinal Functions:: Functions for using characters as numbers and
vice versa.
* Join Function:: A function to join an array into a string.
* Getlocaltime Function:: A function to get formatted times.
* Readfile Function:: A function to read an entire file at once.
* Shell Quoting:: A function to quote strings for the shell.
@end menu
@node Strtonum Function
@subsection Converting Strings to Numbers
The @code{strtonum()} function (@pxref{String Functions})
is a @command{gawk} extension. The following function
provides an implementation for other versions of @command{awk}:
@example
@c file eg/lib/strtonum.awk
# mystrtonum --- convert string to number
@c endfile
@ignore
@c file eg/lib/strtonum.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# February, 2004
# Revised June, 2014
@c endfile
@end ignore
@c file eg/lib/strtonum.awk
function mystrtonum(str, ret, n, i, k, c)
@{
if (str ~ /^0[0-7]*$/) @{
# octal
n = length(str)
ret = 0
for (i = 1; i <= n; i++) @{
c = substr(str, i, 1)
# index() returns 0 if c not in string,
# includes c == "0"
k = index("1234567", c)
ret = ret * 8 + k
@}
@} else if (str ~ /^0[xX][[:xdigit:]]+$/) @{
# hexadecimal
str = substr(str, 3) # lop off leading 0x
n = length(str)
ret = 0
for (i = 1; i <= n; i++) @{
c = substr(str, i, 1)
c = tolower(c)
# index() returns 0 if c not in string,
# includes c == "0"
k = index("123456789abcdef", c)
ret = ret * 16 + k
@}
@} else if (str ~ \
/^[-+]?([0-9]+([.][0-9]*([Ee][0-9]+)?)?|([.][0-9]+([Ee][-+]?[0-9]+)?))$/) @{
# decimal number, possibly floating point
ret = str + 0
@} else
ret = "NOT-A-NUMBER"
return ret
@}
# BEGIN @{ # gawk test harness
# a[1] = "25"
# a[2] = ".31"
# a[3] = "0123"
# a[4] = "0xdeadBEEF"
# a[5] = "123.45"
# a[6] = "1.e3"
# a[7] = "1.32"
# a[8] = "1.32E2"
#
# for (i = 1; i in a; i++)
# print a[i], strtonum(a[i]), mystrtonum(a[i])
# @}
@c endfile
@end example
The function first looks for C-style octal numbers (base 8).
If the input string matches a regular expression describing octal
numbers, then @code{mystrtonum()} loops through each character in the
string. It sets @code{k} to the index in @code{"1234567"} of the current
octal digit.
The return value will either be the same number as the digit, or zero
if the character is not there, which will be true for a @samp{0}.
This is safe, because the regexp test in the @code{if} ensures that
only octal values are converted.
Similar logic applies to the code that checks for and converts a
hexadecimal value, which starts with @samp{0x} or @samp{0X}.
The use of @code{tolower()} simplifies the computation for finding
the correct numeric value for each hexadecimal digit.
Finally, if the string matches the (rather complicated) regexp for a
regular decimal integer or floating-point number, the computation
@samp{ret = str + 0} lets @command{awk} convert the value to a
number.
A commented-out test program is included, so that the function can
be tested with @command{gawk} and the results compared to the built-in
@code{strtonum()} function.
@node Assert Function
@subsection Assertions
@cindex assertions
@cindex @code{assert()} function (C library)
@cindex C library functions @subentry @code{assert()}
@cindex libraries of @command{awk} functions @subentry assertions
@cindex functions @subentry library @subentry assertions
@cindex @command{awk} programs @subentry lengthy @subentry assertions
When writing large programs, it is often useful to know
that a condition or set of conditions is true. Before proceeding with a
particular computation, you make a statement about what you believe to be
the case. Such a statement is known as an
@dfn{assertion}. The C language provides an @code{<assert.h>} header file
and corresponding @code{assert()} macro that a programmer can use to make
assertions. If an assertion fails, the @code{assert()} macro arranges to
print a diagnostic message describing the condition that should have
been true but was not, and then it kills the program. In C, using
@code{assert()} looks this:
@example
@group
#include <assert.h>
int myfunc(int a, double b)
@{
assert(a <= 5 && b >= 17.1);
@dots{}
@}
@end group
@end example
If the assertion fails, the program prints a message similar to this:
@example
prog.c:5: assertion failed: a <= 5 && b >= 17.1
@end example
@cindex @code{assert()} user-defined function
@cindex user-defined @subentry function @subentry @code{assert()}
The C language makes it possible to turn the condition into a string for use
in printing the diagnostic message. This is not possible in @command{awk}, so
this @code{assert()} function also requires a string version of the condition
that is being tested.
Following is the function:
@example
@c file eg/lib/assert.awk
# assert --- assert that a condition is true. Otherwise, exit.
@c endfile
@ignore
@c file eg/lib/assert.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# May, 1993
@c endfile
@end ignore
@c file eg/lib/assert.awk
function assert(condition, string)
@{
if (! condition) @{
printf("%s:%d: assertion failed: %s\n",
FILENAME, FNR, string) > "/dev/stderr"
_assert_exit = 1
exit 1
@}
@}
@group
END @{
if (_assert_exit)
exit 1
@}
@end group
@c endfile
@end example
The @code{assert()} function tests the @code{condition} parameter. If it
is false, it prints a message to standard error, using the @code{string}
parameter to describe the failed condition. It then sets the variable
@code{_assert_exit} to one and executes the @code{exit} statement.
The @code{exit} statement jumps to the @code{END} rule. If the @code{END}
rule finds @code{_assert_exit} to be true, it exits immediately.
The purpose of the test in the @code{END} rule is to
keep any other @code{END} rules from running. When an assertion fails, the
program should exit immediately.
If no assertions fail, then @code{_assert_exit} is still
false when the @code{END} rule is run normally, and the rest of the
program's @code{END} rules execute.
For all of this to work correctly, @file{assert.awk} must be the
first source file read by @command{awk}.
The function can be used in a program in the following way:
@example
function myfunc(a, b)
@{
assert(a <= 5 && b >= 17.1, "a <= 5 && b >= 17.1")
@dots{}
@}
@end example
@noindent
If the assertion fails, you see a message similar to the following:
@example
mydata:1357: assertion failed: a <= 5 && b >= 17.1
@end example
@cindex @code{END} pattern @subentry @code{assert()} user-defined function and
There is a small problem with this version of @code{assert()}.
An @code{END} rule is automatically added
to the program calling @code{assert()}. Normally, if a program consists
of just a @code{BEGIN} rule, the input files and/or standard input are
not read. However, now that the program has an @code{END} rule, @command{awk}
attempts to read the input @value{DF}s or standard input
(@pxref{Using BEGIN/END}),
most likely causing the program to hang as it waits for input.
@cindex @code{BEGIN} pattern @subentry @code{assert()} user-defined function and
There is a simple workaround to this:
make sure that such a @code{BEGIN} rule always ends
with an @code{exit} statement.
@node Round Function
@subsection Rounding Numbers
@cindex rounding numbers
@cindex numbers @subentry rounding
@cindex libraries of @command{awk} functions @subentry rounding numbers
@cindex functions @subentry library @subentry rounding numbers
@cindex @code{print} statement @subentry @code{sprintf()} function and
@cindex @code{printf} statement @subentry @code{sprintf()} function and
@cindex @code{sprintf()} function @subentry @code{print}/@code{printf} statements and
The way @code{printf} and @code{sprintf()}
(@pxref{Printf})
perform rounding often depends upon the system's C @code{sprintf()}
subroutine. On many machines, @code{sprintf()} rounding is @dfn{unbiased},
which means it doesn't always round a trailing .5 up, contrary
to naive expectations. In unbiased rounding, .5 rounds to even,
rather than always up, so 1.5 rounds to 2 but 4.5 rounds to 4. This means
that if you are using a format that does rounding (e.g., @code{"%.0f"}),
you should check what your system does. The following function does
traditional rounding; it might be useful if your @command{awk}'s @code{printf}
does unbiased rounding:
@cindex @code{round()} user-defined function
@cindex user-defined @subentry function @subentry @code{round()}
@example
@c file eg/lib/round.awk
# round.awk --- do normal rounding
@c endfile
@ignore
@c file eg/lib/round.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# August, 1996
@c endfile
@end ignore
@c file eg/lib/round.awk
function round(x, ival, aval, fraction)
@{
ival = int(x) # integer part, int() truncates
# see if fractional part
if (ival == x) # no fraction
return ival # ensure no decimals
if (x < 0) @{
aval = -x # absolute value
ival = int(aval)
fraction = aval - ival
if (fraction >= .5)
return int(x) - 1 # -2.5 --> -3
else
return int(x) # -2.3 --> -2
@} else @{
fraction = x - ival
if (fraction >= .5)
return ival + 1
else
return ival
@}
@}
@c endfile
@c don't include test harness in the file that gets installed
@group
# test harness
# @{ print $0, round($0) @}
@end group
@end example
@node Cliff Random Function
@subsection The Cliff Random Number Generator
@cindex random numbers @subentry Cliff
@cindex Cliff random numbers
@cindex numbers @subentry Cliff random
@cindex functions @subentry library @subentry Cliff random numbers
The
@uref{http://mathworld.wolfram.com/CliffRandomNumberGenerator.html, Cliff random number generator}
is a very simple random number generator that ``passes the noise sphere test
for randomness by showing no structure.''
It is easily programmed, in less than 10 lines of @command{awk} code:
@cindex @code{cliff_rand()} user-defined function
@cindex user-defined @subentry function @subentry @code{cliff_rand()}
@example
@c file eg/lib/cliff_rand.awk
# cliff_rand.awk --- generate Cliff random numbers
@c endfile
@ignore
@c file eg/lib/cliff_rand.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# December 2000
@c endfile
@end ignore
@c file eg/lib/cliff_rand.awk
BEGIN @{ _cliff_seed = 0.1 @}
function cliff_rand()
@{
_cliff_seed = (100 * log(_cliff_seed)) % 1
if (_cliff_seed < 0)
_cliff_seed = - _cliff_seed
return _cliff_seed
@}
@c endfile
@end example
This algorithm requires an initial ``seed'' of 0.1. Each new value
uses the current seed as input for the calculation.
If the built-in @code{rand()} function
(@pxref{Numeric Functions})
isn't random enough, you might try using this function instead.
@node Ordinal Functions
@subsection Translating Between Characters and Numbers
@cindex libraries of @command{awk} functions @subentry character values as numbers
@cindex functions @subentry library @subentry character values as numbers
@cindex characters @subentry values of as numbers
@cindex numbers @subentry as values of characters
One commercial implementation of @command{awk} supplies a built-in function,
@code{ord()}, which takes a character and returns the numeric value for that
character in the machine's character set. If the string passed to
@code{ord()} has more than one character, only the first one is used.
The inverse of this function is @code{chr()} (from the function of the same
name in Pascal), which takes a number and returns the corresponding character.
Both functions are written very nicely in @command{awk}; there is no real
reason to build them into the @command{awk} interpreter:
@cindex @code{ord()} user-defined function
@cindex user-defined @subentry function @subentry @code{ord()}
@cindex @code{chr()} user-defined function
@cindex user-defined @subentry function @subentry @code{chr()}
@cindex @code{_ord_init()} user-defined function
@cindex user-defined @subentry function @subentry @code{_ord_init()}
@example
@c file eg/lib/ord.awk
# ord.awk --- do ord and chr
# Global identifiers:
# _ord_: numerical values indexed by characters
# _ord_init: function to initialize _ord_
@c endfile
@ignore
@c file eg/lib/ord.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# 16 January, 1992
# 20 July, 1992, revised
@c endfile
@end ignore
@c file eg/lib/ord.awk
BEGIN @{ _ord_init() @}
function _ord_init( low, high, i, t)
@{
low = sprintf("%c", 7) # BEL is ascii 7
if (low == "\a") @{ # regular ascii
low = 0
high = 127
@} else if (sprintf("%c", 128 + 7) == "\a") @{
# ascii, mark parity
low = 128
high = 255
@} else @{ # ebcdic(!)
low = 0
high = 255
@}
for (i = low; i <= high; i++) @{
t = sprintf("%c", i)
_ord_[t] = i
@}
@}
@c endfile
@end example
@cindex character sets (machine character encodings)
@cindex ASCII
@cindex EBCDIC
@cindex Unicode
@cindex mark parity
Some explanation of the numbers used by @code{_ord_init()} is worthwhile.
The most prominent character set in use today is ASCII.@footnote{This
is changing; many systems use Unicode, a very large character set
that includes ASCII as a subset. On systems with full Unicode support,
a character can occupy up to 32 bits, making simple tests such as
used here prohibitively expensive.}
Although an
8-bit byte can hold 256 distinct values (from 0 to 255), ASCII only
defines characters that use the values from 0 to 127.@footnote{ASCII
has been extended in many countries to use the values from 128 to 255
for country-specific characters. If your system uses these extensions,
you can simplify @code{_ord_init()} to loop from 0 to 255.}
In the now distant past,
at least one minicomputer manufacturer
@c Pr1me, blech
used ASCII, but with mark parity, meaning that the leftmost bit in the byte
is always 1. This means that on those systems, characters
have numeric values from 128 to 255.
Finally, large mainframe systems use the EBCDIC character set, which
uses all 256 values.
There are other character sets in use on some older systems, but
they are not really worth worrying about:
@example
@c file eg/lib/ord.awk
function ord(str, c)
@{
# only first character is of interest
c = substr(str, 1, 1)
return _ord_[c]
@}
function chr(c)
@{
# force c to be numeric by adding 0
return sprintf("%c", c + 0)
@}
@c endfile
#### test code ####
# BEGIN @{
# for (;;) @{
# printf("enter a character: ")
# if (getline var <= 0)
# break
# printf("ord(%s) = %d\n", var, ord(var))
# @}
# @}
@c endfile
@end example
An obvious improvement to these functions is to move the code for the
@code{@w{_ord_init}} function into the body of the @code{BEGIN} rule. It was
written this way initially for ease of development.
There is a ``test program'' in a @code{BEGIN} rule, to test the
function. It is commented out for production use.
@node Join Function
@subsection Merging an Array into a String
@cindex libraries of @command{awk} functions @subentry merging arrays into strings
@cindex functions @subentry library @subentry merging arrays into strings
@cindex strings @subentry merging arrays into
@cindex arrays @subentry merging into strings
When doing string processing, it is often useful to be able to join
all the strings in an array into one long string. The following function,
@code{join()}, accomplishes this task. It is used later in several of
the application programs
(@pxref{Sample Programs}).
Good function design is important; this function needs to be general, but it
should also have a reasonable default behavior. It is called with an array
as well as the beginning and ending indices of the elements in the array to be
merged. This assumes that the array indices are numeric---a reasonable
assumption, as the array was likely created with @code{split()}
(@pxref{String Functions}):
@cindex @code{join()} user-defined function
@cindex user-defined @subentry function @subentry @code{join()}
@example
@c file eg/lib/join.awk
# join.awk --- join an array into a string
@c endfile
@ignore
@c file eg/lib/join.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# May 1993
@c endfile
@end ignore
@c file eg/lib/join.awk
function join(array, start, end, sep, result, i)
@{
if (sep == "")
sep = " "
else if (sep == SUBSEP) # magic value
sep = ""
result = array[start]
for (i = start + 1; i <= end; i++)
result = result sep array[i]
return result
@}
@c endfile
@end example
An optional additional argument is the separator to use when joining the
strings back together. If the caller supplies a nonempty value,
@code{join()} uses it; if it is not supplied, it has a null
value. In this case, @code{join()} uses a single space as a default
separator for the strings. If the value is equal to @code{SUBSEP},
then @code{join()} joins the strings with no separator between them.
@code{SUBSEP} serves as a ``magic'' value to indicate that there should
be no separation between the component strings.@footnote{It would
be nice if @command{awk} had an assignment operator for concatenation.
The lack of an explicit operator for concatenation makes string operations
more difficult than they really need to be.}
@node Getlocaltime Function
@subsection Managing the Time of Day
@cindex libraries of @command{awk} functions @subentry managing @subentry time
@cindex functions @subentry library @subentry managing time
@cindex timestamps @subentry formatted
@cindex time @subentry managing
The @code{systime()} and @code{strftime()} functions described in
@ref{Time Functions}
provide the minimum functionality necessary for dealing with the time of day
in human-readable form. Although @code{strftime()} is extensive, the control
formats are not necessarily easy to remember or intuitively obvious when
reading a program.
The following function, @code{getlocaltime()}, populates a user-supplied array
with preformatted time information. It returns a string with the current
time formatted in the same way as the @command{date} utility:
@cindex @code{getlocaltime()} user-defined function
@cindex user-defined @subentry function @subentry @code{getlocaltime()}
@example
@c file eg/lib/gettime.awk
# getlocaltime.awk --- get the time of day in a usable format
@c endfile
@ignore
@c file eg/lib/gettime.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain, May 1993
#
@c endfile
@end ignore
@c file eg/lib/gettime.awk
# Returns a string in the format of output of date(1)
# Populates the array argument time with individual values:
# time["second"] -- seconds (0 - 59)
# time["minute"] -- minutes (0 - 59)
# time["hour"] -- hours (0 - 23)
# time["althour"] -- hours (0 - 12)
# time["monthday"] -- day of month (1 - 31)
# time["month"] -- month of year (1 - 12)
# time["monthname"] -- name of the month
# time["shortmonth"] -- short name of the month
# time["year"] -- year modulo 100 (0 - 99)
# time["fullyear"] -- full year
# time["weekday"] -- day of week (Sunday = 0)
# time["altweekday"] -- day of week (Monday = 0)
# time["dayname"] -- name of weekday
# time["shortdayname"] -- short name of weekday
# time["yearday"] -- day of year (0 - 365)
# time["timezone"] -- abbreviation of timezone name
# time["ampm"] -- AM or PM designation
# time["weeknum"] -- week number, Sunday first day
# time["altweeknum"] -- week number, Monday first day
function getlocaltime(time, ret, now, i)
@{
# get time once, avoids unnecessary system calls
now = systime()
# return date(1)-style output
ret = strftime("%a %b %e %H:%M:%S %Z %Y", now)
# clear out target array
delete time
# fill in values, force numeric values to be
# numeric by adding 0
time["second"] = strftime("%S", now) + 0
time["minute"] = strftime("%M", now) + 0
time["hour"] = strftime("%H", now) + 0
time["althour"] = strftime("%I", now) + 0
time["monthday"] = strftime("%d", now) + 0
time["month"] = strftime("%m", now) + 0
time["monthname"] = strftime("%B", now)
time["shortmonth"] = strftime("%b", now)
time["year"] = strftime("%y", now) + 0
time["fullyear"] = strftime("%Y", now) + 0
time["weekday"] = strftime("%w", now) + 0
time["altweekday"] = strftime("%u", now) + 0
time["dayname"] = strftime("%A", now)
time["shortdayname"] = strftime("%a", now)
time["yearday"] = strftime("%j", now) + 0
time["timezone"] = strftime("%Z", now)
time["ampm"] = strftime("%p", now)
time["weeknum"] = strftime("%U", now) + 0
time["altweeknum"] = strftime("%W", now) + 0
return ret
@}
@c endfile
@end example
The string indices are easier to use and read than the various formats
required by @code{strftime()}. The @code{alarm} program presented in
@ref{Alarm Program}
uses this function.
A more general design for the @code{getlocaltime()} function would have
allowed the user to supply an optional timestamp value to use instead
of the current time.
@node Readfile Function
@subsection Reading a Whole File at Once
Often, it is convenient to have the entire contents of a file available
in memory as a single string. A straightforward but naive way to
do that might be as follows:
@example
function readfile1(file, tmp, contents)
@{
if ((getline tmp < file) < 0)
return
contents = tmp RT
while ((getline tmp < file) > 0)
contents = contents tmp RT
close(file)
return contents
@}
@end example
This function reads from @code{file} one record at a time, building
up the full contents of the file in the local variable @code{contents}.
It works, but is not necessarily efficient.
The following function, based on a suggestion by Denis Shirokov,
reads the entire contents of the named file in one shot:
@cindex @code{readfile()} user-defined function
@cindex user-defined @subentry function @subentry @code{readfile()}
@example
@c file eg/lib/readfile.awk
# readfile.awk --- read an entire file at once
@c endfile
@ignore
@c file eg/lib/readfile.awk
#
# Original idea by Denis Shirokov, cosmogen@@gmail.com, April 2013
#
@c endfile
@end ignore
@c file eg/lib/readfile.awk
function readfile(file, tmp, save_rs)
@{
save_rs = RS
RS = "^$"
getline tmp < file
close(file)
RS = save_rs
return tmp
@}
@c endfile
@end example
It works by setting @code{RS} to @samp{^$}, a regular expression that
will never match if the file has contents. @command{gawk} reads data from
the file into @code{tmp}, attempting to match @code{RS}. The match fails
after each read, but fails quickly, such that @command{gawk} fills
@code{tmp} with the entire contents of the file.
(@xref{Records} for information on @code{RT} and @code{RS}.)
In the case that @code{file} is empty, the return value is the null
string. Thus, calling code may use something like:
@example
contents = readfile("/some/path")
if (length(contents) == 0)
# file was empty @dots{}
@end example
This tests the result to see if it is empty or not. An equivalent
test would be @samp{@w{contents == ""}}.
@xref{Extension Sample Readfile} for an extension function that
also reads an entire file into memory.
@node Shell Quoting
@subsection Quoting Strings to Pass to the Shell
@c included by permission
@ignore
Date: Sun, 27 Jul 2014 17:16:16 -0700
Message-ID: <CAKuGj+iCF_obaCLDUX60aSAgbfocFVtguG39GyeoNxTFby5sqQ@mail.gmail.com>
Subject: Useful awk function
From: Mike Brennan <mike@madronabluff.com>
To: Arnold Robbins <arnold@skeeve.com>
@end ignore
Michael Brennan offers the following programming pattern,
which he uses frequently:
@example
#! /bin/sh
awkp='
@dots{}
'
@var{input_program} | awk "$awkp" | /bin/sh
@end example
For example, a program of his named @command{flac-edit} has this form:
@example
$ @kbd{flac-edit -song="Whoope! That's Great" file.flac}
@end example
It generates the following output, which is to be piped to
the shell (@file{/bin/sh}):
@example
chmod +w file.flac
metaflac --remove-tag=TITLE file.flac
LANG=en_US.88591 metaflac --set-tag=TITLE='Whoope! That'"'"'s Great' file.flac
chmod -w file.flac
@end example
Note the need for shell quoting. The function @code{shell_quote()}
does it. @code{SINGLE} is the one-character string @code{"'"} and
@code{QSINGLE} is the three-character string @code{"\"'\""}:
@example
@c file eg/lib/shellquote.awk
# shell_quote --- quote an argument for passing to the shell
@c endfile
@ignore
@c file eg/lib/shellquote.awk
#
# Michael Brennan
# brennan@@madronabluff.com
# September 2014
@c endfile
@end ignore
@c file eg/lib/shellquote.awk
function shell_quote(s, # parameter
SINGLE, QSINGLE, i, X, n, ret) # locals
@{
if (s == "")
return "\"\""
SINGLE = "\x27" # single quote
QSINGLE = "\"\x27\""
n = split(s, X, SINGLE)
ret = SINGLE X[1] SINGLE
for (i = 2; i <= n; i++)
ret = ret QSINGLE SINGLE X[i] SINGLE
return ret
@}
@c endfile
@end example
@node Data File Management
@section @value{DDF} Management
@cindex files @subentry managing
@cindex libraries of @command{awk} functions @subentry managing @subentry data files
@cindex functions @subentry library @subentry managing data files
This @value{SECTION} presents functions that are useful for managing
command-line @value{DF}s.
@menu
* Filetrans Function:: A function for handling data file transitions.
* Rewind Function:: A function for rereading the current file.
* File Checking:: Checking that data files are readable.
* Empty Files:: Checking for zero-length files.
* Ignoring Assigns:: Treating assignments as file names.
@end menu
@node Filetrans Function
@subsection Noting @value{DDF} Boundaries
@cindex files @subentry managing @subentry data file boundaries
@cindex files @subentry initialization and cleanup
The @code{BEGIN} and @code{END} rules are each executed exactly once, at
the beginning and end of your @command{awk} program, respectively
(@pxref{BEGIN/END}).
We (the @command{gawk} authors) once had a user who mistakenly thought that the
@code{BEGIN} rules were executed at the beginning of each @value{DF} and the
@code{END} rules were executed at the end of each @value{DF}.
When informed
that this was not the case, the user requested that we add new special
patterns to @command{gawk}, named @code{BEGIN_FILE} and @code{END_FILE}, that
would have the desired behavior. He even supplied us the code to do so.
Adding these special patterns to @command{gawk} wasn't necessary;
the job can be done cleanly in @command{awk} itself, as illustrated
by the following library program.
It arranges to call two user-supplied functions, @code{beginfile()} and
@code{endfile()}, at the beginning and end of each @value{DF}.
Besides solving the problem in only nine(!) lines of code, it does so
@emph{portably}; this works with any implementation of @command{awk}:
@example
# transfile.awk
#
# Give the user a hook for filename transitions
#
# The user must supply functions beginfile() and endfile()
# that each take the name of the file being started or
# finished, respectively.
@c #
@c # Arnold Robbins, arnold@@skeeve.com, Public Domain
@c # January 1992
FILENAME != _oldfilename @{
if (_oldfilename != "")
endfile(_oldfilename)
_oldfilename = FILENAME
beginfile(FILENAME)
@}
END @{ endfile(FILENAME) @}
@end example
This file must be loaded before the user's ``main'' program, so that the
rule it supplies is executed first.
This rule relies on @command{awk}'s @code{FILENAME} variable, which
automatically changes for each new @value{DF}. The current @value{FN} is
saved in a private variable, @code{_oldfilename}. If @code{FILENAME} does
not equal @code{_oldfilename}, then a new @value{DF} is being processed and
it is necessary to call @code{endfile()} for the old file. Because
@code{endfile()} should only be called if a file has been processed, the
program first checks to make sure that @code{_oldfilename} is not the null
string. The program then assigns the current @value{FN} to
@code{_oldfilename} and calls @code{beginfile()} for the file.
Because, like all @command{awk} variables, @code{_oldfilename} is
initialized to the null string, this rule executes correctly even for the
first @value{DF}.
The program also supplies an @code{END} rule to do the final processing for
the last file. Because this @code{END} rule comes before any @code{END} rules
supplied in the ``main'' program, @code{endfile()} is called first. Once
again, the value of multiple @code{BEGIN} and @code{END} rules should be clear.
@cindex @code{beginfile()} user-defined function
@cindex user-defined @subentry function @subentry @code{beginfile()}
@cindex @code{endfile()} user-defined function
@cindex user-defined @subentry function @subentry @code{endfile()}
If the same @value{DF} occurs twice in a row on the command line, then
@code{endfile()} and @code{beginfile()} are not executed at the end of the
first pass and at the beginning of the second pass.
The following version solves the problem:
@example
@c file eg/lib/ftrans.awk
# ftrans.awk --- handle datafile transitions
#
# user supplies beginfile() and endfile() functions
@c endfile
@ignore
@c file eg/lib/ftrans.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# November 1992
@c endfile
@end ignore
@c file eg/lib/ftrans.awk
FNR == 1 @{
if (_filename_ != "")
endfile(_filename_)
_filename_ = FILENAME
beginfile(FILENAME)
@}
END @{ endfile(_filename_) @}
@c endfile
@end example
@ref{Wc Program}
shows how this library function can be used and
how it simplifies writing the main program.
@cindex sidebar @subentry So Why Does @command{gawk} Have @code{BEGINFILE} and @code{ENDFILE}?
@ifdocbook
@docbook
<sidebar><title>So Why Does @command{gawk} Have @code{BEGINFILE} and @code{ENDFILE}?</title>
@end docbook
You are probably wondering, if @code{beginfile()} and @code{endfile()}
functions can do the job, why does @command{gawk} have
@code{BEGINFILE} and @code{ENDFILE} patterns?
Good question. Normally, if @command{awk} cannot open a file, this
causes an immediate fatal error. In this case, there is no way for a
user-defined function to deal with the problem, as the mechanism for
calling it relies on the file being open and at the first record. Thus,
the main reason for @code{BEGINFILE} is to give you a ``hook'' to catch
files that cannot be processed. @code{ENDFILE} exists for symmetry,
and because it provides an easy way to do per-file cleanup processing.
For more information, refer to @ref{BEGINFILE/ENDFILE}.
@docbook
</sidebar>
@end docbook
@end ifdocbook
@ifnotdocbook
@cartouche
@center @b{So Why Does @command{gawk} Have @code{BEGINFILE} and @code{ENDFILE}?}
You are probably wondering, if @code{beginfile()} and @code{endfile()}
functions can do the job, why does @command{gawk} have
@code{BEGINFILE} and @code{ENDFILE} patterns?
Good question. Normally, if @command{awk} cannot open a file, this
causes an immediate fatal error. In this case, there is no way for a
user-defined function to deal with the problem, as the mechanism for
calling it relies on the file being open and at the first record. Thus,
the main reason for @code{BEGINFILE} is to give you a ``hook'' to catch
files that cannot be processed. @code{ENDFILE} exists for symmetry,
and because it provides an easy way to do per-file cleanup processing.
For more information, refer to @ref{BEGINFILE/ENDFILE}.
@end cartouche
@end ifnotdocbook
@node Rewind Function
@subsection Rereading the Current File
@cindex files @subentry reading
Another request for a new built-in function was for a
function that would make it possible to reread the current file.
The requesting user didn't want to have to use @code{getline}
(@pxref{Getline})
inside a loop.
However, as long as you are not in the @code{END} rule, it is
quite easy to arrange to immediately close the current input file
and then start over with it from the top.
For lack of a better name, we'll call the function @code{rewind()}:
@cindex @code{rewind()} user-defined function
@cindex user-defined @subentry function @subentry @code{rewind()}
@example
@c file eg/lib/rewind.awk
# rewind.awk --- rewind the current file and start over
@c endfile
@ignore
@c file eg/lib/rewind.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# September 2000
@c endfile
@end ignore
@c file eg/lib/rewind.awk
function rewind( i)
@{
# shift remaining arguments up
for (i = ARGC; i > ARGIND; i--)
ARGV[i] = ARGV[i-1]
# make sure gawk knows to keep going
ARGC++
# make current file next to get done
ARGV[ARGIND+1] = FILENAME
# do it
nextfile
@}
@c endfile
@end example
The @code{rewind()} function relies on the @code{ARGIND} variable
(@pxref{Auto-set}), which is specific to @command{gawk}. It also
relies on the @code{nextfile} keyword (@pxref{Nextfile Statement}).
Because of this, you should not call it from an @code{ENDFILE} rule.
(This isn't necessary anyway, because @command{gawk} goes to the next
file as soon as an @code{ENDFILE} rule finishes!)
You need to be careful calling @code{rewind()}. You can end up
causing infinite recursion if you don't pay attention. Here is an
example use:
@example
$ @kbd{cat data}
@print{} a
@print{} b
@print{} c
@print{} d
@print{} e
$ cat @kbd{test.awk}
@print{} FNR == 3 && ! rewound @{
@print{} rewound = 1
@print{} rewind()
@print{} @}
@print{}
@print{} @{ print FILENAME, FNR, $0 @}
$ @kbd{gawk -f rewind.awk -f test.awk data }
@print{} data 1 a
@print{} data 2 b
@print{} data 1 a
@print{} data 2 b
@print{} data 3 c
@group
@print{} data 4 d
@print{} data 5 e
@end group
@end example
@node File Checking
@subsection Checking for Readable @value{DDF}s
@cindex troubleshooting @subentry readable data files
@cindex readable data files, checking
@cindex files @subentry skipping
Normally, if you give @command{awk} a @value{DF} that isn't readable,
it stops with a fatal error. There are times when you might want to
just ignore such files and keep going.@footnote{The @code{BEGINFILE}
special pattern (@pxref{BEGINFILE/ENDFILE}) provides an alternative
mechanism for dealing with files that can't be opened. However, the
code here provides a portable solution.} You can do this by prepending
the following program to your @command{awk} program:
@cindex @code{readable.awk} program
@example
@c file eg/lib/readable.awk
# readable.awk --- library file to skip over unreadable files
@c endfile
@ignore
@c file eg/lib/readable.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# October 2000
# December 2010
@c endfile
@end ignore
@c file eg/lib/readable.awk
BEGIN @{
for (i = 1; i < ARGC; i++) @{
if (ARGV[i] ~ /^[a-zA-Z_][a-zA-Z0-9_]*=.*/ \
|| ARGV[i] == "-" || ARGV[i] == "/dev/stdin")
continue # assignment or standard input
else if ((getline junk < ARGV[i]) < 0) # unreadable
delete ARGV[i]
else
close(ARGV[i])
@}
@}
@c endfile
@end example
@cindex troubleshooting @subentry @code{getline} command
This works, because the @code{getline} won't be fatal.
Removing the element from @code{ARGV} with @code{delete}
skips the file (because it's no longer in the list).
See also @ref{ARGC and ARGV}.
Because @command{awk} variable names only allow the English letters,
the regular expression check purposely does not use character classes
such as @samp{[:alpha:]} and @samp{[:alnum:]}
(@pxref{Bracket Expressions}).
@node Empty Files
@subsection Checking for Zero-Length Files
All known @command{awk} implementations silently skip over zero-length files.
This is a by-product of @command{awk}'s implicit
read-a-record-and-match-against-the-rules loop: when @command{awk}
tries to read a record from an empty file, it immediately receives an
end-of-file indication, closes the file, and proceeds on to the next
command-line @value{DF}, @emph{without} executing any user-level
@command{awk} program code.
Using @command{gawk}'s @code{ARGIND} variable
(@pxref{Built-in Variables}), it is possible to detect when an empty
@value{DF} has been skipped. Similar to the library file presented
in @ref{Filetrans Function}, the following library file calls a function named
@code{zerofile()} that the user must provide. The arguments passed are
the @value{FN} and the position in @code{ARGV} where it was found:
@cindex @code{zerofile.awk} program
@example
@c file eg/lib/zerofile.awk
# zerofile.awk --- library file to process empty input files
@c endfile
@ignore
@c file eg/lib/zerofile.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# June 2003
@c endfile
@end ignore
@c file eg/lib/zerofile.awk
BEGIN @{ Argind = 0 @}
ARGIND > Argind + 1 @{
for (Argind++; Argind < ARGIND; Argind++)
zerofile(ARGV[Argind], Argind)
@}
ARGIND != Argind @{ Argind = ARGIND @}
END @{
if (ARGIND > Argind)
for (Argind++; Argind <= ARGIND; Argind++)
zerofile(ARGV[Argind], Argind)
@}
@c endfile
@end example
The user-level variable @code{Argind} allows the @command{awk} program
to track its progress through @code{ARGV}. Whenever the program detects
that @code{ARGIND} is greater than @samp{Argind + 1}, it means that one or
more empty files were skipped. The action then calls @code{zerofile()} for
each such file, incrementing @code{Argind} along the way.
The @samp{Argind != ARGIND} rule simply keeps @code{Argind} up to date
in the normal case.
Finally, the @code{END} rule catches the case of any empty files at
the end of the command-line arguments. Note that the test in the
condition of the @code{for} loop uses the @samp{<=} operator,
not @samp{<}.
@node Ignoring Assigns
@subsection Treating Assignments as @value{FFN}s
@cindex assignments as file names
@cindex file names @subentry assignments as
Occasionally, you might not want @command{awk} to process command-line
variable assignments
(@pxref{Assignment Options}).
In particular, if you have a @value{FN} that contains an @samp{=} character,
@command{awk} treats the @value{FN} as an assignment and does not process it.
Some users have suggested an additional command-line option for @command{gawk}
to disable command-line assignments. However, some simple programming with
a library file does the trick:
@cindex @code{noassign.awk} program
@example
@c file eg/lib/noassign.awk
# noassign.awk --- library file to avoid the need for a
# special option that disables command-line assignments
@c endfile
@ignore
@c file eg/lib/noassign.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# October 1999
@c endfile
@end ignore
@c file eg/lib/noassign.awk
function disable_assigns(argc, argv, i)
@{
for (i = 1; i < argc; i++)
if (argv[i] ~ /^[a-zA-Z_][a-zA-Z0-9_]*=.*/)
argv[i] = ("./" argv[i])
@}
BEGIN @{
if (No_command_assign)
disable_assigns(ARGC, ARGV)
@}
@c endfile
@end example
You then run your program this way:
@example
awk -v No_command_assign=1 -f noassign.awk -f yourprog.awk *
@end example
The function works by looping through the arguments.
It prepends @samp{./} to
any argument that matches the form
of a variable assignment, turning that argument into a @value{FN}.
The use of @code{No_command_assign} allows you to disable command-line
assignments at invocation time, by giving the variable a true value.
When not set, it is initially zero (i.e., false), so the command-line arguments
are left alone.
@node Getopt Function
@section Processing Command-Line Options
@cindex libraries of @command{awk} functions @subentry command-line options
@cindex functions @subentry library @subentry command-line options
@cindex command line @subentry options @subentry processing
@cindex options @subentry command-line @subentry processing
@cindex functions @subentry library @subentry C library
@cindex arguments @subentry processing
Most utilities on POSIX-compatible systems take options on
the command line that can be used to change the way a program behaves.
@command{awk} is an example of such a program
(@pxref{Options}).
Often, options take @dfn{arguments} (i.e., data that the program needs to
correctly obey the command-line option). For example, @command{awk}'s
@option{-F} option requires a string to use as the field separator.
The first occurrence on the command line of either @option{--} or a
string that does not begin with @samp{-} ends the options.
@cindex @code{getopt()} function (C library)
@cindex C library functions @subentry @code{getopt()}
Modern Unix systems provide a C function named @code{getopt()} for processing
command-line arguments. The programmer provides a string describing the
one-letter options. If an option requires an argument, it is followed in the
string with a colon. @code{getopt()} is also passed the
count and values of the command-line arguments and is called in a loop.
@code{getopt()} processes the command-line arguments for option letters.
Each time around the loop, it returns a single character representing the
next option letter that it finds, or @samp{?} if it finds an invalid option.
When it returns @minus{}1, there are no options left on the command line.
When using @code{getopt()}, options that do not take arguments can be
grouped together. Furthermore, options that take arguments require that the
argument be present. The argument can immediately follow the option letter,
or it can be a separate command-line argument.
Given a hypothetical program that takes
three command-line options, @option{-a}, @option{-b}, and @option{-c}, where
@option{-b} requires an argument, all of the following are valid ways of
invoking the program:
@example
prog -a -b foo -c data1 data2 data3
prog -ac -bfoo -- data1 data2 data3
prog -acbfoo data1 data2 data3
@end example
Notice that when the argument is grouped with its option, the rest of
the argument is considered to be the option's argument.
In this example, @option{-acbfoo} indicates that all of the
@option{-a}, @option{-b}, and @option{-c} options were supplied,
and that @samp{foo} is the argument to the @option{-b} option.
@code{getopt()} provides four external variables that the programmer can use:
@table @code
@item optind
The index in the argument value array (@code{argv}) where the first
nonoption command-line argument can be found.
@item optarg
The string value of the argument to an option.
@item opterr
Usually @code{getopt()} prints an error message when it finds an invalid
option. Setting @code{opterr} to zero disables this feature. (An
application might want to print its own error message.)
@item optopt
The letter representing the command-line option.
@end table
The following C fragment shows how @code{getopt()} might process command-line
arguments for @command{awk}:
@example
int
main(int argc, char *argv[])
@{
@dots{}
/* print our own message */
opterr = 0;
while ((c = getopt(argc, argv, "v:f:F:W:")) != -1) @{
switch (c) @{
case 'f': /* file */
@dots{}
break;
case 'F': /* field separator */
@dots{}
break;
case 'v': /* variable assignment */
@dots{}
break;
case 'W': /* extension */
@dots{}
break;
case '?':
default:
usage();
break;
@}
@}
@dots{}
@}
@end example
The GNU project's version of the original Unix utilities popularized
the use of long command line options. For example, @option{--help}
in addition to @option{-h}. Arguments to long options are either provided
as separate command line arguments (@samp{--source '@var{program-text}'})
or separated from the option with an @samp{=} sign
(@samp{--source='@var{program-text}'}).
As a side point, @command{gawk} actually uses the GNU @code{getopt_long()}
function to process both normal and GNU-style long options
(@pxref{Options}).
The abstraction provided by @code{getopt()} is very useful and is quite
handy in @command{awk} programs as well. Following is an @command{awk}
version of @code{getopt()} that accepts both short and long options.
This function highlights one of the
greatest weaknesses in @command{awk}, which is that it is very poor at
manipulating single characters. The function needs repeated calls to
@code{substr()} in order to access individual characters
(@pxref{String Functions}).@footnote{This
function was written before @command{gawk} acquired the ability to
split strings into single characters using @code{""} as the separator.
We have left it alone, as using @code{substr()} is more portable.}
The discussion that follows walks through the code a bit at a time:
@cindex @code{getopt()} user-defined function
@cindex user-defined @subentry function @subentry @code{getopt()}
@example
@c file eg/lib/getopt.awk
# getopt.awk --- Do C library getopt(3) function in awk
# Also supports long options.
@c endfile
@ignore
@c file eg/lib/getopt.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
#
# Initial version: March, 1991
# Revised: May, 1993
# Long options added by Greg Minshall, January 2020
@c endfile
@end ignore
@c file eg/lib/getopt.awk
# External variables:
# Optind -- index in ARGV of first nonoption argument
# Optarg -- string value of argument to current option
# Opterr -- if nonzero, print our own diagnostic
# Optopt -- current option letter
# Returns:
# -1 at end of options
# "?" for unrecognized option
# <s> a string representing the current option
# Private Data:
# _opti -- index in multiflag option, e.g., -abc
@c endfile
@end example
The function starts out with comments presenting
a list of the global variables it uses,
what the return values are, what they mean, and any global variables that
are ``private'' to this library function. Such documentation is essential
for any program, and particularly for library functions.
The @code{getopt()} function first checks that it was indeed called with
a string of options (the @code{options} parameter). If both
@code{options} and @code{longoptions} have a zero length,
@code{getopt()} immediately returns @minus{}1:
@cindex @code{getopt()} user-defined function
@cindex user-defined @subentry function @subentry @code{getopt()}
@example
@c file eg/lib/getopt.awk
function getopt(argc, argv, options, longopts, thisopt, i, j)
@{
if (length(options) == 0 && length(longopts) == 0)
return -1 # no options given
@group
if (argv[Optind] == "--") @{ # all done
Optind++
_opti = 0
return -1
@end group
@} else if (argv[Optind] !~ /^-[^:[:space:]]/) @{
_opti = 0
return -1
@}
@c endfile
@end example
The next thing to check for is the end of the options. A @option{--}
ends the command-line options, as does any command-line argument that
does not begin with a @samp{-} (unless it is an argument to a preceding
option). @code{Optind} steps through
the array of command-line arguments; it retains its value across calls
to @code{getopt()}, because it is a global variable.
The regular expression @code{@w{/^-[^:[:space:]/}}
checks for a @samp{-} followed by anything
that is not whitespace and not a colon.
If the current command-line argument does not match this pattern,
it is not an option, and it ends option processing.
Now, we
check to see if we are processing a short (single letter) option, or a
long option (indicated by two dashes, e.g., @samp{--filename}). If it
is a short option, we continue on:
@example
@c file eg/lib/getopt.awk
if (argv[Optind] !~ /^--/) @{ # if this is a short option
if (_opti == 0)
_opti = 2
thisopt = substr(argv[Optind], _opti, 1)
Optopt = thisopt
i = index(options, thisopt)
if (i == 0) @{
if (Opterr)
printf("%c -- invalid option\n", thisopt) > "/dev/stderr"
if (_opti >= length(argv[Optind])) @{
Optind++
_opti = 0
@} else
_opti++
return "?"
@}
@c endfile
@end example
The @code{_opti} variable tracks the position in the current command-line
argument (@code{argv[Optind]}). If multiple options are
grouped together with one @samp{-} (e.g., @option{-abx}), it is necessary
to return them to the user one at a time.
If @code{_opti} is equal to zero, it is set to two, which is the index in
the string of the next character to look at (we skip the @samp{-}, which
is at position one). The variable @code{thisopt} holds the character,
obtained with @code{substr()}. It is saved in @code{Optopt} for the main
program to use.
If @code{thisopt} is not in the @code{options} string, then it is an
invalid option. If @code{Opterr} is nonzero, @code{getopt()} prints an error
message on the standard error that is similar to the message from the C
version of @code{getopt()}.
Because the option is invalid, it is necessary to skip it and move on to the
next option character. If @code{_opti} is greater than or equal to the
length of the current command-line argument, it is necessary to move on
to the next argument, so @code{Optind} is incremented and @code{_opti} is reset
to zero. Otherwise, @code{Optind} is left alone and @code{_opti} is merely
incremented.
In any case, because the option is invalid, @code{getopt()} returns @code{"?"}.
The main program can examine @code{Optopt} if it needs to know what the
invalid option letter actually is. Continuing on:
@example
@c file eg/lib/getopt.awk
if (substr(options, i + 1, 1) == ":") @{
# get option argument
if (length(substr(argv[Optind], _opti + 1)) > 0)
Optarg = substr(argv[Optind], _opti + 1)
else
Optarg = argv[++Optind]
_opti = 0
@} else
Optarg = ""
@c endfile
@end example
If the option requires an argument, the option letter is followed by a colon
in the @code{options} string. If there are remaining characters in the
current command-line argument (@code{argv[Optind]}), then the rest of that
string is assigned to @code{Optarg}. Otherwise, the next command-line
argument is used (@samp{-xFOO} versus @samp{@w{-x FOO}}). In either case,
@code{_opti} is reset to zero, because there are no more characters left to
examine in the current command-line argument. Continuing:
@example
@c file eg/lib/getopt.awk
if (_opti == 0 || _opti >= length(argv[Optind])) @{
Optind++
_opti = 0
@} else
_opti++
return thisopt
@c endfile
@end example
Finally, for a short option, if @code{_opti} is either zero or greater
than the length of the current command-line argument, it means this
element in @code{argv} is through being processed, so @code{Optind} is
incremented to point to the next element in @code{argv}. If neither
condition is true, then only @code{_opti} is incremented, so that the
next option letter can be processed on the next call to @code{getopt()}.
On the other hand, if the earlier test found that this was a long
option, we take a different branch:
@example
@c file eg/lib/getopt.awk
@} else @{
j = index(argv[Optind], "=")
if (j > 0)
thisopt = substr(argv[Optind], 3, j - 3)
else
thisopt = substr(argv[Optind], 3)
Optopt = thisopt
@c endfile
@end example
First, we search this option for a possible embedded equal sign, as the
specification of long options allows an argument to an option
@samp{--someopt:} to be specified as @samp{--someopt=answer} as well as
@samp{@w{--someopt answer}}.
@example
@c file eg/lib/getopt.awk
i = match(longopts, "(^|,)" thisopt "($|[,:])")
if (i == 0) @{
if (Opterr)
printf("%s -- invalid option\n", thisopt) > "/dev/stderr"
Optind++
return "?"
@}
@c endfile
@end example
Next, we try to find the current option in @code{longopts}. The regular
expression given to @code{match()}, @code{@w{"(^|,)" thisopt "($|[,:])"}},
matches this option at the beginning of @code{longopts}, or at the
beginning of a subsequent long option (the previous long option would
have been terminated by a comma), and, in any case, either at the end of
the @code{longopts} string (@samp{$}), or followed by a comma
(separating this option from a subsequent option) or a colon (indicating
this long option takes an argument (@samp{@w{[,:]}}).
Using this regular expression, we check to see if the current option
might possibly be in @code{longopts} (if @code{longopts} is not
specified, this test will also fail). In case of an error, we possibly
print an error message and then return @code{"?"}. Continuing on:
@example
@c file eg/lib/getopt.awk
if (substr(longopts, i+1+length(thisopt), 1) == ":") @{
if (j > 0)
Optarg = substr(argv[Optind], j + 1)
else
Optarg = argv[++Optind]
@} else
Optarg = ""
@c endfile
@end example
We now check to see if this option takes an argument and, if so, we set
@code{Optarg} to the value of that argument (either a value after an
equal sign specified on the command line, immediately adjoining the long
option string, or as the next argument on the command line).
@example
@c file eg/lib/getopt.awk
Optind++
return thisopt
@}
@}
@c endfile
@end example
We increase @code{Optind} (which we already increased once if a required
argument was separated from its option by an equal sign), and return the
long option (minus its leading dashes).
The @code{BEGIN} rule initializes both @code{Opterr} and @code{Optind} to one.
@code{Opterr} is set to one, because the default behavior is for @code{getopt()}
to print a diagnostic message upon seeing an invalid option. @code{Optind}
is set to one, because there's no reason to look at the program name, which is
in @code{ARGV[0]}:
@example
@c file eg/lib/getopt.awk
BEGIN @{
Opterr = 1 # default is to diagnose
Optind = 1 # skip ARGV[0]
# test program
if (_getopt_test) @{
_myshortopts = "ab:cd"
_mylongopts = "longa,longb:,otherc,otherd"
while ((_go_c = getopt(ARGC, ARGV, _myshortopts, _mylongopts)) != -1)
printf("c = <%s>, Optarg = <%s>\n", _go_c, Optarg)
printf("non-option arguments:\n")
for (; Optind < ARGC; Optind++)
printf("\tARGV[%d] = <%s>\n", Optind, ARGV[Optind])
@}
@}
@c endfile
@end example
The rest of the @code{BEGIN} rule is a simple test program. Here are the
results of some sample runs of the test program:
@example
$ @kbd{awk -f getopt.awk -v _getopt_test=1 -- -a -cbARG bax -x}
@print{} c = <a>, Optarg = <>
@print{} c = <c>, Optarg = <>
@print{} c = <b>, Optarg = <ARG>
@print{} non-option arguments:
@print{} ARGV[3] = <bax>
@print{} ARGV[4] = <-x>
$ @kbd{awk -f getopt.awk -v _getopt_test=1 -- -a -x -- xyz abc}
@print{} c = <a>, Optarg = <>
@error{} x -- invalid option
@print{} c = <?>, Optarg = <>
@print{} non-option arguments:
@print{} ARGV[4] = <xyz>
@print{} ARGV[5] = <abc>
$ @kbd{awk -f getopt.awk -v _getopt_test=1 -- -a \}
> @kbd{--longa -b xx --longb=foo=bar --otherd --otherc arg1 arg2}
@print{} c = <a>, Optarg = <>
@print{} c = <longa>, Optarg = <>
@print{} c = <b>, Optarg = <xx>
@print{} c = <longb>, Optarg = <foo=bar>
@print{} c = <otherd>, Optarg = <>
@print{} c = <otherc>, Optarg = <>
@print{} non-option arguments:
@print{} ARGV[8] = <arg1>
@print{} ARGV[9] = <arg2>
@end example
In all the runs, the first @option{--} terminates the arguments to
@command{awk}, so that it does not try to interpret the @option{-a},
etc., as its own options.
@quotation NOTE
After @code{getopt()} is through,
user-level code must clear out all the elements of @code{ARGV} from 1
to @code{Optind}, so that @command{awk} does not try to process the
command-line options as @value{FN}s.
@end quotation
Using @samp{#!} with the @option{-E} option may help avoid
conflicts between your program's options and @command{gawk}'s options,
as @option{-E} causes @command{gawk} to abandon processing of
further options
(@pxref{Executable Scripts} and
@ifnotdocbook
@pxref{Options}).
@end ifnotdocbook
@ifdocbook
@ref{Options}).
@end ifdocbook
Several of the sample programs presented in
@ref{Sample Programs},
use @code{getopt()} to process their arguments.
@node Passwd Functions
@section Reading the User Database
@cindex libraries of @command{awk} functions @subentry user database, reading
@cindex functions @subentry library @subentry user database, reading
@cindex user database, reading
@cindex database @subentry users, reading
@cindex @code{PROCINFO} array
The @code{PROCINFO} array
(@pxref{Built-in Variables})
provides access to the current user's real and effective user and group ID
numbers, and, if available, the user's supplementary group set.
However, because these are numbers, they do not provide very useful
information to the average user. There needs to be some way to find the
user information associated with the user and group ID numbers. This
@value{SECTION} presents a suite of functions for retrieving information from the
user database. @xref{Group Functions}
for a similar suite that retrieves information from the group database.
@cindex @code{getpwent()} function (C library)
@cindex C library functions @subentry @code{getpwent()}
@cindex @code{getpwent()} user-defined function
@cindex user-defined @subentry function @subentry @code{getpwent()}
@cindex users, information about @subentry retrieving
@cindex login information
@cindex account information
@cindex password file
@cindex files @subentry password
The POSIX standard does not define the file where user information is
kept. Instead, it provides the @code{<pwd.h>} header file
and several C language subroutines for obtaining user information.
The primary function is @code{getpwent()}, for ``get password entry.''
The ``password'' comes from the original user database file,
@file{/etc/passwd}, which stores user information along with the
encrypted passwords (hence the name).
@cindex @command{pwcat} program
Although an @command{awk} program could simply read @file{/etc/passwd}
directly, this file may not contain complete information about the
system's set of users.@footnote{It is often the case that password
information is stored in a network database.} To be sure you are able to
produce a readable and complete version of the user database, it is necessary
to write a small C program that calls @code{getpwent()}. @code{getpwent()}
is defined as returning a pointer to a @code{struct passwd}. Each time it
is called, it returns the next entry in the database. When there are
no more entries, it returns @code{NULL}, the null pointer. When this
happens, the C program should call @code{endpwent()} to close the database.
Following is @command{pwcat}, a C program that ``cats'' the password database:
@example
@c file eg/lib/pwcat.c
/*
* pwcat.c
*
* Generate a printable version of the password database.
*/
@c endfile
@ignore
@c file eg/lib/pwcat.c
/*
* Arnold Robbins, arnold@@skeeve.com, May 1993
* Public Domain
* December 2010, move to ANSI C definition for main().
*/
#if HAVE_CONFIG_H
#include <config.h>
#endif
@c endfile
@end ignore
@c file eg/lib/pwcat.c
#include <stdio.h>
#include <pwd.h>
@c endfile
@ignore
@c file eg/lib/pwcat.c
#if defined (STDC_HEADERS)
#include <stdlib.h>
#endif
@c endfile
@end ignore
@c file eg/lib/pwcat.c
int
main(int argc, char **argv)
@{
struct passwd *p;
while ((p = getpwent()) != NULL)
@c endfile
@ignore
@c file eg/lib/pwcat.c
#ifdef HAVE_STRUCT_PASSWD_PW_PASSWD
@c endfile
@end ignore
@c file eg/lib/pwcat.c
printf("%s:%s:%ld:%ld:%s:%s:%s\n",
p->pw_name, p->pw_passwd, (long) p->pw_uid,
(long) p->pw_gid, p->pw_gecos, p->pw_dir, p->pw_shell);
@c endfile
@ignore
@c file eg/lib/pwcat.c
#else
printf("%s:*:%ld:%ld:%s:%s\n",
p->pw_name, (long) p->pw_uid,
(long) p->pw_gid, p->pw_dir, p->pw_shell);
#endif
@c endfile
@end ignore
@c file eg/lib/pwcat.c
endpwent();
return 0;
@}
@c endfile
@end example
If you don't understand C, don't worry about it.
The output from @command{pwcat} is the user database, in the traditional
@file{/etc/passwd} format of colon-separated fields. The fields are:
@table @asis
@item Login name
The user's login name.
@item Encrypted password
The user's encrypted password. This may not be available on some systems.
@item User-ID
The user's numeric user ID number.
(On some systems, it's a C @code{long}, and not an @code{int}. Thus,
we cast it to @code{long} for all cases.)
@item Group-ID
The user's numeric group ID number.
(Similar comments about @code{long} versus @code{int} apply here.)
@item Full name
The user's full name, and perhaps other information associated with the
user.
@item Home directory
The user's login (or ``home'') directory (familiar to shell programmers as
@code{$HOME}).
@item Login shell
The program that is run when the user logs in. This is usually a
shell, such as Bash.
@end table
A few lines representative of @command{pwcat}'s output are as follows:
@cindex Jacobs, Andrew
@cindex Robbins @subentry Arnold
@cindex Robbins @subentry Miriam
@example
$ @kbd{pwcat}
@print{} root:x:0:1:Operator:/:/bin/sh
@print{} nobody:*:65534:65534::/:
@print{} daemon:*:1:1::/:
@print{} sys:*:2:2::/:/bin/csh
@print{} bin:*:3:3::/bin:
@print{} arnold:xyzzy:2076:10:Arnold Robbins:/home/arnold:/bin/sh
@print{} miriam:yxaay:112:10:Miriam Robbins:/home/miriam:/bin/sh
@print{} andy:abcca2:113:10:Andy Jacobs:/home/andy:/bin/sh
@dots{}
@end example
With that introduction, following is a group of functions for getting user
information. There are several functions here, corresponding to the C
functions of the same names:
@cindex @code{_pw_init()} user-defined function
@cindex user-defined @subentry function @subentry @code{_pw_init()}
@example
@c file eg/lib/passwdawk.in
# passwd.awk --- access password file information
@c endfile
@ignore
@c file eg/lib/passwdawk.in
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# May 1993
# Revised October 2000
# Revised December 2010
@c endfile
@end ignore
@c file eg/lib/passwdawk.in
BEGIN @{
# tailor this to suit your system
_pw_awklib = "/usr/local/libexec/awk/"
@}
function _pw_init( oldfs, oldrs, olddol0, pwcat, using_fw, using_fpat)
@{
if (_pw_inited)
return
oldfs = FS
oldrs = RS
olddol0 = $0
using_fw = (PROCINFO["FS"] == "FIELDWIDTHS")
using_fpat = (PROCINFO["FS"] == "FPAT")
FS = ":"
RS = "\n"
pwcat = _pw_awklib "pwcat"
while ((pwcat | getline) > 0) @{
_pw_byname[$1] = $0
_pw_byuid[$3] = $0
_pw_bycount[++_pw_total] = $0
@}
close(pwcat)
_pw_count = 0
_pw_inited = 1
FS = oldfs
if (using_fw)
FIELDWIDTHS = FIELDWIDTHS
else if (using_fpat)
FPAT = FPAT
RS = oldrs
$0 = olddol0
@}
@c endfile
@end example
@cindex @code{BEGIN} pattern @subentry @code{pwcat} program
The @code{BEGIN} rule sets a private variable to the directory where
@command{pwcat} is stored. Because it is used to help out an @command{awk} library
routine, we have chosen to put it in @file{/usr/local/libexec/awk};
however, you might want it to be in a different directory on your system.
The function @code{_pw_init()} fills three copies of the user information
into three associative arrays. The arrays are indexed by username
(@code{_pw_byname}), by user ID number (@code{_pw_byuid}), and by order of
occurrence (@code{_pw_bycount}).
The variable @code{_pw_inited} is used for efficiency, as @code{_pw_init()}
needs to be called only once.
@cindex @code{PROCINFO} array @subentry testing the field splitting
@cindex @code{getline} command @subentry @code{_pw_init()} function
Because this function uses @code{getline} to read information from
@command{pwcat}, it first saves the values of @code{FS}, @code{RS}, and @code{$0}.
It notes in the variable @code{using_fw} whether field splitting
with @code{FIELDWIDTHS} is in effect or not.
Doing so is necessary, as these functions could be called
from anywhere within a user's program, and the user may have his
or her own way of splitting records and fields.
This makes it possible to restore the correct
field-splitting mechanism later. The test can only be true for
@command{gawk}. It is false if using @code{FS} or @code{FPAT},
or on some other @command{awk} implementation.
The code that checks for using @code{FPAT}, using @code{using_fpat}
and @code{PROCINFO["FS"]}, is similar.
The main part of the function uses a loop to read database lines, split
the lines into fields, and then store the lines into each array as necessary.
When the loop is done, @code{@w{_pw_init()}} cleans up by closing the pipeline,
setting @code{@w{_pw_inited}} to one, and restoring @code{FS}
(and @code{FIELDWIDTHS} or @code{FPAT}
if necessary), @code{RS}, and @code{$0}.
The use of @code{@w{_pw_count}} is explained shortly.
@cindex @code{getpwnam()} function (C library)
@cindex C library functions @subentry @code{getpwnam()}
The @code{getpwnam()} function takes a username as a string argument. If that
user is in the database, it returns the appropriate line. Otherwise, it
relies on the array reference to a nonexistent
element to create the element with the null string as its value:
@cindex @code{getpwnam()} user-defined function
@cindex user-defined @subentry function @subentry @code{getpwnam()}
@example
@group
@c file eg/lib/passwdawk.in
function getpwnam(name)
@{
_pw_init()
return _pw_byname[name]
@}
@c endfile
@end group
@end example
@cindex @code{getpwuid()} function (C library)
@cindex C library functions @subentry @code{getpwuid()}
Similarly, the @code{getpwuid()} function takes a user ID number
argument. If that user number is in the database, it returns the
appropriate line. Otherwise, it returns the null string:
@cindex @code{getpwuid()} user-defined function
@cindex user-defined @subentry function @subentry @code{getpwuid()}
@example
@c file eg/lib/passwdawk.in
function getpwuid(uid)
@{
_pw_init()
return _pw_byuid[uid]
@}
@c endfile
@end example
@cindex @code{getpwent()} function (C library)
@cindex C library functions @subentry @code{getpwent()}
The @code{getpwent()} function simply steps through the database, one entry at
a time. It uses @code{_pw_count} to track its current position in the
@code{_pw_bycount} array:
@cindex @code{getpwent()} user-defined function
@cindex user-defined @subentry function @subentry @code{getpwent()}
@example
@c file eg/lib/passwdawk.in
function getpwent()
@{
_pw_init()
if (_pw_count < _pw_total)
return _pw_bycount[++_pw_count]
return ""
@}
@c endfile
@end example
@cindex @code{endpwent()} function (C library)
@cindex C library functions @subentry @code{endpwent()}
The @code{@w{endpwent()}} function resets @code{@w{_pw_count}} to zero, so that
subsequent calls to @code{getpwent()} start over again:
@cindex @code{endpwent()} user-defined function
@cindex user-defined @subentry function @subentry @code{endpwent()}
@example
@c file eg/lib/passwdawk.in
function endpwent()
@{
_pw_count = 0
@}
@c endfile
@end example
A conscious design decision in this suite is that each subroutine calls
@code{@w{_pw_init()}} to initialize the database arrays.
The overhead of running
a separate process to generate the user database, and the I/O to scan it,
are only incurred if the user's main program actually calls one of these
functions. If this library file is loaded along with a user's program, but
none of the routines are ever called, then there is no extra runtime overhead.
(The alternative is move the body of @code{@w{_pw_init()}} into a
@code{BEGIN} rule, which always runs @command{pwcat}. This simplifies the
code but runs an extra process that may never be needed.)
In turn, calling @code{_pw_init()} is not too expensive, because the
@code{_pw_inited} variable keeps the program from reading the data more than
once. If you are worried about squeezing every last cycle out of your
@command{awk} program, the check of @code{_pw_inited} could be moved out of
@code{_pw_init()} and duplicated in all the other functions. In practice,
this is not necessary, as most @command{awk} programs are I/O-bound,
and such a change would clutter up the code.
The @command{id} program in @ref{Id Program}
uses these functions.
@node Group Functions
@section Reading the Group Database
@cindex libraries of @command{awk} functions @subentry group database, reading
@cindex functions @subentry library @subentry group database, reading
@cindex group database, reading
@cindex database @subentry group, reading
@cindex @code{PROCINFO} array @subentry group membership and
@cindex @code{getgrent()} function (C library)
@cindex C library functions @subentry @code{getgrent()}
@cindex @code{getgrent()} user-defined function
@cindex user-defined @subentry function @subentry @code{getgrent()}
@cindex groups, information about
@cindex account information
@cindex group file
@cindex files @subentry group
Much of the discussion presented in
@ref{Passwd Functions}
applies to the group database as well. Although there has traditionally
been a well-known file (@file{/etc/group}) in a well-known format, the POSIX
standard only provides a set of C library routines
(@code{<grp.h>} and @code{getgrent()})
for accessing the information.
Even though this file may exist, it may not have
complete information. Therefore, as with the user database, it is necessary
to have a small C program that generates the group database as its output.
@command{grcat}, a C program that ``cats'' the group database,
is as follows:
@cindex @command{grcat} program
@example
@c file eg/lib/grcat.c
/*
* grcat.c
*
* Generate a printable version of the group database.
*/
@c endfile
@ignore
@c file eg/lib/grcat.c
/*
* Arnold Robbins, arnold@@skeeve.com, May 1993
* Public Domain
* December 2010, move to ANSI C definition for main().
*/
#if HAVE_CONFIG_H
#include <config.h>
#endif
#if defined (STDC_HEADERS)
#include <stdlib.h>
#endif
#ifndef HAVE_GETGRENT
int main() { return 0; }
#else
@c endfile
@end ignore
@c file eg/lib/grcat.c
#include <stdio.h>
#include <grp.h>
int
main(int argc, char **argv)
@{
struct group *g;
int i;
while ((g = getgrent()) != NULL) @{
@c endfile
@ignore
@c file eg/lib/grcat.c
#ifdef HAVE_STRUCT_GROUP_GR_PASSWD
@c endfile
@end ignore
@c file eg/lib/grcat.c
printf("%s:%s:%ld:", g->gr_name, g->gr_passwd,
(long) g->gr_gid);
@c endfile
@ignore
@c file eg/lib/grcat.c
#else
printf("%s:*:%ld:", g->gr_name, (long) g->gr_gid);
#endif
@c endfile
@end ignore
@c file eg/lib/grcat.c
for (i = 0; g->gr_mem[i] != NULL; i++) @{
printf("%s", g->gr_mem[i]);
@group
if (g->gr_mem[i+1] != NULL)
putchar(',');
@}
@end group
putchar('\n');
@}
endgrent();
return 0;
@}
@c endfile
@ignore
@c file eg/lib/grcat.c
#endif /* HAVE_GETGRENT */
@c endfile
@end ignore
@end example
Each line in the group database represents one group. The fields are
separated with colons and represent the following information:
@table @asis
@item Group Name
The group's name.
@item Group Password
The group's encrypted password. In practice, this field is never used;
it is usually empty or set to @samp{*}.
@item Group ID Number
The group's numeric group ID number;
the association of name to number must be unique within the file.
(On some systems it's a C @code{long}, and not an @code{int}. Thus,
we cast it to @code{long} for all cases.)
@item Group Member List
A comma-separated list of usernames. These users are members of the group.
Modern Unix systems allow users to be members of several groups
simultaneously. If your system does, then there are elements
@code{"group1"} through @code{"group@var{N}"} in @code{PROCINFO}
for those group ID numbers.
(Note that @code{PROCINFO} is a @command{gawk} extension;
@pxref{Built-in Variables}.)
@end table
Here is what running @command{grcat} might produce:
@example
$ @kbd{grcat}
@print{} wheel:*:0:arnold
@print{} nogroup:*:65534:
@print{} daemon:*:1:
@print{} kmem:*:2:
@print{} staff:*:10:arnold,miriam,andy
@print{} other:*:20:
@dots{}
@end example
Here are the functions for obtaining information from the group database.
There are several, modeled after the C library functions of the same names:
@cindex @code{getline} command @subentry @code{_gr_init()} user-defined function
@cindex @code{_gr_init()} user-defined function
@cindex user-defined @subentry function @subentry @code{_gr_init()}
@example
@c file eg/lib/groupawk.in
# group.awk --- functions for dealing with the group file
@c endfile
@ignore
@c file eg/lib/groupawk.in
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# May 1993
# Revised October 2000
# Revised December 2010
@c endfile
@end ignore
@c line break on _gr_init for smallbook
@c file eg/lib/groupawk.in
BEGIN @{
# Change to suit your system
_gr_awklib = "/usr/local/libexec/awk/"
@}
function _gr_init( oldfs, oldrs, olddol0, grcat,
using_fw, using_fpat, n, a, i)
@{
if (_gr_inited)
return
oldfs = FS
oldrs = RS
olddol0 = $0
using_fw = (PROCINFO["FS"] == "FIELDWIDTHS")
using_fpat = (PROCINFO["FS"] == "FPAT")
FS = ":"
RS = "\n"
grcat = _gr_awklib "grcat"
while ((grcat | getline) > 0) @{
if ($1 in _gr_byname)
_gr_byname[$1] = _gr_byname[$1] "," $4
else
_gr_byname[$1] = $0
if ($3 in _gr_bygid)
_gr_bygid[$3] = _gr_bygid[$3] "," $4
else
_gr_bygid[$3] = $0
n = split($4, a, "[ \t]*,[ \t]*")
for (i = 1; i <= n; i++)
if (a[i] in _gr_groupsbyuser)
_gr_groupsbyuser[a[i]] = _gr_groupsbyuser[a[i]] " " $1
else
_gr_groupsbyuser[a[i]] = $1
_gr_bycount[++_gr_count] = $0
@}
close(grcat)
_gr_count = 0
_gr_inited++
FS = oldfs
if (using_fw)
FIELDWIDTHS = FIELDWIDTHS
else if (using_fpat)
FPAT = FPAT
RS = oldrs
$0 = olddol0
@}
@c endfile
@end example
The @code{BEGIN} rule sets a private variable to the directory where
@command{grcat} is stored. Because it is used to help out an @command{awk} library
routine, we have chosen to put it in @file{/usr/local/libexec/awk}. You might
want it to be in a different directory on your system.
These routines follow the same general outline as the user database routines
(@pxref{Passwd Functions}).
The @code{@w{_gr_inited}} variable is used to
ensure that the database is scanned no more than once.
The @code{@w{_gr_init()}} function first saves @code{FS},
@code{RS}, and
@code{$0}, and then sets @code{FS} and @code{RS} to the correct values for
scanning the group information.
It also takes care to note whether @code{FIELDWIDTHS} or @code{FPAT}
is being used, and to restore the appropriate field-splitting mechanism.
The group information is stored in several associative arrays.
The arrays are indexed by group name (@code{@w{_gr_byname}}), by group ID number
(@code{@w{_gr_bygid}}), and by position in the database (@code{@w{_gr_bycount}}).
There is an additional array indexed by username (@code{@w{_gr_groupsbyuser}}),
which is a space-separated list of groups to which each user belongs.
Unlike in the user database, it is possible to have multiple records in the
database for the same group. This is common when a group has a large number
of members. A pair of such entries might look like the following:
@example
tvpeople:*:101:johnny,jay,arsenio
tvpeople:*:101:david,conan,tom,joan
@end example
For this reason, @code{_gr_init()} looks to see if a group name or
group ID number is already seen. If so, the usernames are
simply concatenated onto the previous list of users.@footnote{There is a
subtle problem with the code just presented. Suppose that
the first time there were no names. This code adds the names with
a leading comma. It also doesn't check that there is a @code{$4}.}
Finally, @code{_gr_init()} closes the pipeline to @command{grcat}, restores
@code{FS} (and @code{FIELDWIDTHS} or @code{FPAT}, if necessary), @code{RS}, and @code{$0},
initializes @code{_gr_count} to zero
(it is used later), and makes @code{_gr_inited} nonzero.
@cindex @code{getgrnam()} function (C library)
@cindex C library functions @subentry @code{getgrnam()}
The @code{getgrnam()} function takes a group name as its argument, and if that
group exists, it is returned.
Otherwise, it
relies on the array reference to a nonexistent
element to create the element with the null string as its value:
@cindex @code{getgrnam()} user-defined function
@cindex user-defined @subentry function @subentry @code{getgrnam()}
@example
@c file eg/lib/groupawk.in
function getgrnam(group)
@{
_gr_init()
return _gr_byname[group]
@}
@c endfile
@end example
@cindex @code{getgrgid()} function (C library)
@cindex C library functions @subentry @code{getgrgid()}
The @code{getgrgid()} function is similar; it takes a numeric group ID and
looks up the information associated with that group ID:
@cindex @code{getgrgid()} user-defined function
@cindex user-defined @subentry function @subentry @code{getgrgid()}
@example
@c file eg/lib/groupawk.in
function getgrgid(gid)
@{
_gr_init()
return _gr_bygid[gid]
@}
@c endfile
@end example
@cindex @code{getgruser()} function (C library)
@cindex C library functions @subentry @code{getgruser()}
The @code{getgruser()} function does not have a C counterpart. It takes a
username and returns the list of groups that have the user as a member:
@cindex @code{getgruser()} user-defined function
@cindex user-defined @subentry function @subentry @code{getgruser()}
@example
@c file eg/lib/groupawk.in
function getgruser(user)
@{
_gr_init()
return _gr_groupsbyuser[user]
@}
@c endfile
@end example
@cindex @code{getgrent()} function (C library)
@cindex C library functions @subentry @code{getgrent()}
The @code{getgrent()} function steps through the database one entry at a time.
It uses @code{_gr_count} to track its position in the list:
@cindex @code{getgrent()} user-defined function
@cindex user-defined @subentry function @subentry @code{getgrent()}
@example
@c file eg/lib/groupawk.in
function getgrent()
@{
_gr_init()
if (++_gr_count in _gr_bycount)
return _gr_bycount[_gr_count]
@group
return ""
@}
@end group
@c endfile
@end example
@cindex @code{endgrent()} function (C library)
@cindex C library functions @subentry @code{endgrent()}
The @code{endgrent()} function resets @code{_gr_count} to zero so that @code{getgrent()} can
start over again:
@cindex @code{endgrent()} user-defined function
@cindex user-defined @subentry function @subentry @code{endgrent()}
@example
@c file eg/lib/groupawk.in
function endgrent()
@{
_gr_count = 0
@}
@c endfile
@end example
As with the user database routines, each function calls @code{_gr_init()} to
initialize the arrays. Doing so only incurs the extra overhead of running
@command{grcat} if these functions are used (as opposed to moving the body of
@code{_gr_init()} into a @code{BEGIN} rule).
Most of the work is in scanning the database and building the various
associative arrays. The functions that the user calls are themselves very
simple, relying on @command{awk}'s associative arrays to do work.
The @command{id} program in @ref{Id Program}
uses these functions.
@node Walking Arrays
@section Traversing Arrays of Arrays
@ref{Arrays of Arrays} described how @command{gawk}
provides arrays of arrays. In particular, any element of
an array may be either a scalar or another array. The
@code{isarray()} function (@pxref{Type Functions})
lets you distinguish an array
from a scalar.
The following function, @code{walk_array()}, recursively traverses
an array, printing the element indices and values.
You call it with the array and a string representing the name
of the array:
@cindex @code{walk_array()} user-defined function
@cindex user-defined @subentry function @subentry @code{walk_array()}
@example
@c file eg/lib/walkarray.awk
function walk_array(arr, name, i)
@{
for (i in arr) @{
if (isarray(arr[i]))
walk_array(arr[i], (name "[" i "]"))
else
printf("%s[%s] = %s\n", name, i, arr[i])
@}
@}
@c endfile
@end example
@noindent
It works by looping over each element of the array. If any given
element is itself an array, the function calls itself recursively,
passing the subarray and a new string representing the current index.
Otherwise, the function simply prints the element's name, index, and value.
Here is a main program to demonstrate:
@example
BEGIN @{
a[1] = 1
a[2][1] = 21
a[2][2] = 22
a[3] = 3
a[4][1][1] = 411
a[4][2] = 42
walk_array(a, "a")
@}
@end example
When run, the program produces the following output:
@example
$ @kbd{gawk -f walk_array.awk}
@print{} a[1] = 1
@print{} a[2][1] = 21
@print{} a[2][2] = 22
@print{} a[3] = 3
@print{} a[4][1][1] = 411
@print{} a[4][2] = 42
@end example
The function just presented simply prints the
name and value of each scalar array element. However, it is easy to
generalize it, by passing in the name of a function to call
when walking an array. The modified function looks like this:
@example
@c file eg/lib/processarray.awk
function process_array(arr, name, process, do_arrays, i, new_name)
@{
for (i in arr) @{
new_name = (name "[" i "]")
if (isarray(arr[i])) @{
if (do_arrays)
@@process(new_name, arr[i])
process_array(arr[i], new_name, process, do_arrays)
@} else
@@process(new_name, arr[i])
@}
@}
@c endfile
@end example
The arguments are as follows:
@table @code
@item arr
The array.
@item name
The name of the array (a string).
@item process
The name of the function to call.
@item do_arrays
If this is true, the function can handle elements that are subarrays.
@end table
If subarrays are to be processed, that is done before walking them further.
When run with the following scaffolding, the function produces the same
results as does the earlier version of @code{walk_array()}:
@example
BEGIN @{
a[1] = 1
a[2][1] = 21
a[2][2] = 22
a[3] = 3
a[4][1][1] = 411
a[4][2] = 42
process_array(a, "a", "do_print", 0)
@}
function do_print(name, element)
@{
printf "%s = %s\n", name, element
@}
@end example
@node Library Functions Summary
@section Summary
@itemize @value{BULLET}
@item
Reading programs is an excellent way to learn Good Programming.
The functions and programs provided in this @value{CHAPTER} and the next
are intended to serve that purpose.
@item
When writing general-purpose library functions, put some thought into how
to name any global variables so that they won't conflict with variables
from a user's program.
@item
The functions presented here fit into the following categories:
@c nested list
@table @asis
@item General problems
Number-to-string conversion, testing assertions, rounding, random number
generation, converting characters to numbers, joining strings, getting
easily usable time-of-day information, and reading a whole file in
one shot
@item Managing @value{DF}s
Noting @value{DF} boundaries, rereading the current file, checking for
readable files, checking for zero-length files, and treating assignments
as @value{FN}s
@item Processing command-line options
An @command{awk} version of the standard C @code{getopt()} function
@item Reading the user and group databases
Two sets of routines that parallel the C library versions
@item Traversing arrays of arrays
Two functions that traverse an array of arrays to any depth
@end table
@c end nested list
@end itemize
@c EXCLUDE START
@node Library Exercises
@section Exercises
@enumerate
@item
In @ref{Empty Files}, we presented the @file{zerofile.awk} program,
which made use of @command{gawk}'s @code{ARGIND} variable. Can this
problem be solved without relying on @code{ARGIND}? If so, how?
@ignore
# zerofile2.awk --- same thing, portably
BEGIN @{
ARGIND = Argind = 0
for (i = 1; i < ARGC; i++)
Fnames[ARGV[i]]++
@}
FNR == 1 @{
while (ARGV[ARGIND] != FILENAME)
ARGIND++
Seen[FILENAME]++
if (Seen[FILENAME] == Fnames[FILENAME])
do
ARGIND++
while (ARGV[ARGIND] != FILENAME)
@}
ARGIND > Argind + 1 @{
for (Argind++; Argind < ARGIND; Argind++)
zerofile(ARGV[Argind], Argind)
@}
ARGIND != Argind @{
Argind = ARGIND
@}
END @{
if (ARGIND < ARGC - 1)
ARGIND = ARGC - 1
if (ARGIND > Argind)
for (Argind++; Argind <= ARGIND; Argind++)
zerofile(ARGV[Argind], Argind)
@}
@end ignore
@item
As a related challenge, revise that code to handle the case where
an intervening value in @code{ARGV} is a variable assignment.
@ignore
@c June 13 2015: Antonio points out that this is answered in the text. Ooops.
@item
@ref{Walking Arrays} presented a function that walked a multidimensional
array to print it out. However, walking an array and processing
each element is a general-purpose operation. Generalize the
@code{walk_array()} function by adding an additional parameter named
@code{process}.
Then, inside the loop, instead of printing the array element's index and
value, use the indirect function call syntax (@pxref{Indirect Calls})
on @code{process}, passing it the index and the value.
When calling @code{walk_array()}, you would pass the name of a
user-defined function that expects to receive an index and a value,
and then processes the element.
Test your new version by printing the array; you should end up with
output identical to that of the original version.
@end ignore
@end enumerate
@c EXCLUDE END
@node Sample Programs
@chapter Practical @command{awk} Programs
@cindex @command{awk} programs @subentry examples of
@c FULLXREF ON
@ref{Library Functions},
presents the idea that reading programs in a language contributes to
learning that language. This @value{CHAPTER} continues that theme,
presenting a potpourri of @command{awk} programs for your reading
enjoyment.
@c FULLXREF OFF
@ifnotinfo
There are three @value{SECTION}s.
The first describes how to run the programs presented
in this @value{CHAPTER}.
The second presents @command{awk}
versions of several common POSIX utilities.
These are programs that you are hopefully already familiar with,
and therefore whose problems are understood.
By reimplementing these programs in @command{awk},
you can focus on the @command{awk}-related aspects of solving
the programming problems.
The third is a grab bag of interesting programs.
These solve a number of different data-manipulation and management
problems. Many of the programs are short, which emphasizes @command{awk}'s
ability to do a lot in just a few lines of code.
@end ifnotinfo
Many of these programs use library functions presented in
@ref{Library Functions}.
@menu
* Running Examples:: How to run these examples.
* Clones:: Clones of common utilities.
* Miscellaneous Programs:: Some interesting @command{awk} programs.
* Programs Summary:: Summary of programs.
* Programs Exercises:: Exercises.
@end menu
@node Running Examples
@section Running the Example Programs
To run a given program, you would typically do something like this:
@example
awk -f @var{program} -- @var{options} @var{files}
@end example
@noindent
Here, @var{program} is the name of the @command{awk} program (such as
@file{cut.awk}), @var{options} are any command-line options for the
program that start with a @samp{-}, and @var{files} are the actual @value{DF}s.
If your system supports the @samp{#!} executable interpreter mechanism
(@pxref{Executable Scripts}),
you can instead run your program directly:
@example
cut.awk -c1-8 myfiles > results
@end example
If your @command{awk} is not @command{gawk}, you may instead need to use this:
@example
cut.awk -- -c1-8 myfiles > results
@end example
@node Clones
@section Reinventing Wheels for Fun and Profit
@cindex POSIX @subentry programs, implementing in @command{awk}
This @value{SECTION} presents a number of POSIX utilities implemented in
@command{awk}. Reinventing these programs in @command{awk} is often enjoyable,
because the algorithms can be very clearly expressed, and the code is usually
very concise and simple. This is true because @command{awk} does so much for you.
It should be noted that these programs are not necessarily intended to
replace the installed versions on your system.
Nor may all of these programs be fully compliant with the most recent
POSIX standard. This is not a problem; their
purpose is to illustrate @command{awk} language programming for ``real-world''
tasks.
The programs are presented in alphabetical order.
@menu
* Cut Program:: The @command{cut} utility.
* Egrep Program:: The @command{egrep} utility.
* Id Program:: The @command{id} utility.
* Split Program:: The @command{split} utility.
* Tee Program:: The @command{tee} utility.
* Uniq Program:: The @command{uniq} utility.
* Wc Program:: The @command{wc} utility.
@end menu
@node Cut Program
@subsection Cutting Out Fields and Columns
@cindex @command{cut} utility
@cindex @command{cut} utility
@cindex fields @subentry cutting
@cindex columns @subentry cutting
The @command{cut} utility selects, or ``cuts,'' characters or fields
from its standard input and sends them to its standard output.
Fields are separated by TABs by default,
but you may supply a command-line option to change the field
@dfn{delimiter} (i.e., the field-separator character). @command{cut}'s
definition of fields is less general than @command{awk}'s.
A common use of @command{cut} might be to pull out just the login names of
logged-on users from the output of @command{who}. For example, the following
pipeline generates a sorted, unique list of the logged-on users:
@example
who | cut -c1-8 | sort | uniq
@end example
The options for @command{cut} are:
@table @code
@item -c @var{list}
Use @var{list} as the list of characters to cut out. Items within the list
may be separated by commas, and ranges of characters can be separated with
dashes. The list @samp{1-8,15,22-35} specifies characters 1 through
8, 15, and 22 through 35.
@item -f @var{list}
Use @var{list} as the list of fields to cut out.
@item -d @var{delim}
Use @var{delim} as the field-separator character instead of the TAB
character.
@item -s
Suppress printing of lines that do not contain the field delimiter.
@end table
The @command{awk} implementation of @command{cut} uses the @code{getopt()} library
function (@pxref{Getopt Function})
and the @code{join()} library function
(@pxref{Join Function}).
The program begins with a comment describing the options, the library
functions needed, and a @code{usage()} function that prints out a usage
message and exits. @code{usage()} is called if invalid arguments are
supplied:
@cindex @code{cut.awk} program
@example
@c file eg/prog/cut.awk
# cut.awk --- implement cut in awk
@c endfile
@ignore
@c file eg/prog/cut.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# May 1993
@c endfile
@end ignore
@c file eg/prog/cut.awk
# Options:
# -f list Cut fields
# -d c Field delimiter character
# -c list Cut characters
#
# -s Suppress lines without the delimiter
#
# Requires getopt() and join() library functions
@group
function usage()
@{
print("usage: cut [-f list] [-d c] [-s] [files...]") > "/dev/stderr"
print("usage: cut [-c list] [files...]") > "/dev/stderr"
exit 1
@}
@end group
@c endfile
@end example
@cindex @code{BEGIN} pattern @subentry running @command{awk} programs and
@cindex @code{FS} variable @subentry running @command{awk} programs and
Next comes a @code{BEGIN} rule that parses the command-line options.
It sets @code{FS} to a single TAB character, because that is @command{cut}'s
default field separator. The rule then sets the output field separator to be the
same as the input field separator. A loop using @code{getopt()} steps
through the command-line options. Exactly one of the variables
@code{by_fields} or @code{by_chars} is set to true, to indicate that
processing should be done by fields or by characters, respectively.
When cutting by characters, the output field separator is set to the null
string:
@example
@c file eg/prog/cut.awk
BEGIN @{
FS = "\t" # default
OFS = FS
while ((c = getopt(ARGC, ARGV, "sf:c:d:")) != -1) @{
if (c == "f") @{
by_fields = 1
fieldlist = Optarg
@} else if (c == "c") @{
by_chars = 1
fieldlist = Optarg
OFS = ""
@} else if (c == "d") @{
if (length(Optarg) > 1) @{
printf("cut: using first character of %s" \
" for delimiter\n", Optarg) > "/dev/stderr"
Optarg = substr(Optarg, 1, 1)
@}
fs = FS = Optarg
OFS = FS
if (FS == " ") # defeat awk semantics
FS = "[ ]"
@} else if (c == "s")
suppress = 1
else
usage()
@}
# Clear out options
for (i = 1; i < Optind; i++)
ARGV[i] = ""
@c endfile
@end example
@cindex field separator @subentry spaces as
The code must take
special care when the field delimiter is a space. Using
a single space (@code{@w{" "}}) for the value of @code{FS} is
incorrect---@command{awk} would separate fields with runs of spaces,
TABs, and/or newlines, and we want them to be separated with individual
spaces.
To this end, we save the original space character in the variable
@code{fs} for later use; after setting @code{FS} to @code{"[ ]"} we can't
use it directly to see if the field delimiter character is in the string.
Also remember that after @code{getopt()} is through
(as described in @ref{Getopt Function}),
we have to
clear out all the elements of @code{ARGV} from 1 to @code{Optind},
so that @command{awk} does not try to process the command-line options
as @value{FN}s.
After dealing with the command-line options, the program verifies that the
options make sense. Only one or the other of @option{-c} and @option{-f}
should be used, and both require a field list. Then the program calls
either @code{set_fieldlist()} or @code{set_charlist()} to pull apart the
list of fields or characters:
@example
@c file eg/prog/cut.awk
if (by_fields && by_chars)
usage()
if (by_fields == 0 && by_chars == 0)
by_fields = 1 # default
@group
if (fieldlist == "") @{
print "cut: needs list for -c or -f" > "/dev/stderr"
exit 1
@}
@end group
if (by_fields)
set_fieldlist()
else
set_charlist()
@}
@c endfile
@end example
@code{set_fieldlist()} splits the field list apart at the commas
into an array. Then, for each element of the array, it looks to
see if the element is actually a range, and if so, splits it apart.
The function checks the range
to make sure that the first number is smaller than the second.
Each number in the list is added to the @code{flist} array, which
simply lists the fields that will be printed. Normal field splitting
is used. The program lets @command{awk} handle the job of doing the
field splitting:
@example
@c file eg/prog/cut.awk
function set_fieldlist( n, m, i, j, k, f, g)
@{
n = split(fieldlist, f, ",")
j = 1 # index in flist
for (i = 1; i <= n; i++) @{
if (index(f[i], "-") != 0) @{ # a range
m = split(f[i], g, "-")
@group
if (m != 2 || g[1] >= g[2]) @{
printf("cut: bad field list: %s\n",
f[i]) > "/dev/stderr"
exit 1
@}
@end group
for (k = g[1]; k <= g[2]; k++)
flist[j++] = k
@} else
flist[j++] = f[i]
@}
nfields = j - 1
@}
@c endfile
@end example
The @code{set_charlist()} function is more complicated than
@code{set_fieldlist()}.
The idea here is to use @command{gawk}'s @code{FIELDWIDTHS} variable
(@pxref{Constant Size}),
which describes constant-width input. When using a character list, that is
exactly what we have.
Setting up @code{FIELDWIDTHS} is more complicated than simply listing the
fields that need to be printed. We have to keep track of the fields to
print and also the intervening characters that have to be skipped.
For example, suppose you wanted characters 1 through 8, 15, and
22 through 35. You would use @samp{-c 1-8,15,22-35}. The necessary value
for @code{FIELDWIDTHS} is @code{@w{"8 6 1 6 14"}}. This yields five
fields, and the fields to print
are @code{$1}, @code{$3}, and @code{$5}.
The intermediate fields are @dfn{filler},
which is stuff in between the desired data.
@code{flist} lists the fields to print, and @code{t} tracks the
complete field list, including filler fields:
@example
@c file eg/prog/cut.awk
function set_charlist( field, i, j, f, g, n, m, t,
filler, last, len)
@{
field = 1 # count total fields
n = split(fieldlist, f, ",")
j = 1 # index in flist
for (i = 1; i <= n; i++) @{
if (index(f[i], "-") != 0) @{ # range
m = split(f[i], g, "-")
if (m != 2 || g[1] >= g[2]) @{
printf("cut: bad character list: %s\n",
f[i]) > "/dev/stderr"
exit 1
@}
len = g[2] - g[1] + 1
if (g[1] > 1) # compute length of filler
filler = g[1] - last - 1
else
filler = 0
@group
if (filler)
t[field++] = filler
@end group
t[field++] = len # length of field
last = g[2]
flist[j++] = field - 1
@} else @{
if (f[i] > 1)
filler = f[i] - last - 1
else
filler = 0
if (filler)
t[field++] = filler
t[field++] = 1
last = f[i]
flist[j++] = field - 1
@}
@}
FIELDWIDTHS = join(t, 1, field - 1)
nfields = j - 1
@}
@c endfile
@end example
Next is the rule that processes the data. If the @option{-s} option
is given, then @code{suppress} is true. The first @code{if} statement
makes sure that the input record does have the field separator. If
@command{cut} is processing fields, @code{suppress} is true, and the field
separator character is not in the record, then the record is skipped.
If the record is valid, then @command{gawk} has split the data
into fields, either using the character in @code{FS} or using fixed-length
fields and @code{FIELDWIDTHS}. The loop goes through the list of fields
that should be printed. The corresponding field is printed if it contains data.
If the next field also has data, then the separator character is
written out between the fields:
@example
@c file eg/prog/cut.awk
@{
if (by_fields && suppress && index($0, fs) == 0)
next
for (i = 1; i <= nfields; i++) @{
if ($flist[i] != "") @{
printf "%s", $flist[i]
if (i < nfields && $flist[i+1] != "")
printf "%s", OFS
@}
@}
print ""
@}
@c endfile
@end example
This version of @command{cut} relies on @command{gawk}'s @code{FIELDWIDTHS}
variable to do the character-based cutting. It is possible in
other @command{awk} implementations to use @code{substr()}
(@pxref{String Functions}), but
it is also extremely painful.
The @code{FIELDWIDTHS} variable supplies an elegant solution to the problem
of picking the input line apart by characters.
@node Egrep Program
@subsection Searching for Regular Expressions in Files
@cindex regular expressions @subentry searching for
@cindex searching @subentry files for regular expressions
@cindex files @subentry searching for regular expressions
@cindex @command{egrep} utility
The @command{egrep} utility searches files for patterns. It uses regular
expressions that are almost identical to those available in @command{awk}
(@pxref{Regexp}).
You invoke it as follows:
@display
@command{egrep} [@var{options}] @code{'@var{pattern}'} @var{files} @dots{}
@end display
The @var{pattern} is a regular expression. In typical usage, the regular
expression is quoted to prevent the shell from expanding any of the
special characters as @value{FN} wildcards. Normally, @command{egrep}
prints the lines that matched. If multiple @value{FN}s are provided on
the command line, each output line is preceded by the name of the file
and a colon.
The options to @command{egrep} are as follows:
@table @code
@item -c
Print out a count of the lines that matched the pattern, instead of the
lines themselves.
@item -s
Be silent. No output is produced and the exit value indicates whether
the pattern was matched.
@item -v
Invert the sense of the test. @command{egrep} prints the lines that do
@emph{not} match the pattern and exits successfully if the pattern is not
matched.
@item -i
Ignore case distinctions in both the pattern and the input data.
@item -l
Only print (list) the names of the files that matched, not the lines that matched.
@item -e @var{pattern}
Use @var{pattern} as the regexp to match. The purpose of the @option{-e}
option is to allow patterns that start with a @samp{-}.
@end table
This version uses the @code{getopt()} library function
(@pxref{Getopt Function})
and the file transition library program
(@pxref{Filetrans Function}).
The program begins with a descriptive comment and then a @code{BEGIN} rule
that processes the command-line arguments with @code{getopt()}. The @option{-i}
(ignore case) option is particularly easy with @command{gawk}; we just use the
@code{IGNORECASE} predefined variable
(@pxref{Built-in Variables}):
@cindex @code{egrep.awk} program
@example
@c file eg/prog/egrep.awk
# egrep.awk --- simulate egrep in awk
#
@c endfile
@ignore
@c file eg/prog/egrep.awk
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# May 1993
@c endfile
@end ignore
@c file eg/prog/egrep.awk
# Options:
# -c count of lines
# -s silent - use exit value
# -v invert test, success if no match
# -i ignore case
# -l print filenames only
# -e argument is pattern
#
# Requires getopt and file transition library functions
BEGIN @{
while ((c = getopt(ARGC, ARGV, "ce:svil")) != -1) @{
if (c == "c")
count_only++
else if (c == "s")
no_print++
else if (c == "v")
invert++
else if (c == "i")
IGNORECASE = 1
else if (c == "l")
filenames_only++
else if (c == "e")
pattern = Optarg
else
usage()
@}
@c endfile
@end example
Next comes the code that handles the @command{egrep}-specific behavior. If no
pattern is supplied with @option{-e}, the first nonoption on the
command line is used. The @command{awk} command-line arguments up to @code{ARGV[Optind]}
are cleared, so that @command{awk} won't try to process them as files. If no
files are specified, the standard input is used, and if multiple files are
specified, we make sure to note this so that the @value{FN}s can precede the
matched lines in the output:
@example
@c file eg/prog/egrep.awk
if (pattern == "")
pattern = ARGV[Optind++]
for (i = 1; i < Optind; i++)
ARGV[i] = ""
if (Optind >= ARGC) @{
ARGV[1] = "-"
ARGC = 2
@} else if (ARGC - Optind > 1)
do_filenames++
# if (IGNORECASE)
# pattern = tolower(pattern)
@}
@c endfile
@end example
The last two lines are commented out, as they are not needed in
@command{gawk}. They should be uncommented if you have to use another version
of @command{awk}.
The next set of lines should be uncommented if you are not using
@command{gawk}. This rule translates all the characters in the input line
into lowercase if the @option{-i} option is specified.@footnote{It
also introduces a subtle bug;
if a match happens, we output the translated line, not the original.}
The rule is
commented out as it is not necessary with @command{gawk}:
@example
@c file eg/prog/egrep.awk
#@{
# if (IGNORECASE)
# $0 = tolower($0)
#@}
@c endfile
@end example
The @code{beginfile()} function is called by the rule in @file{ftrans.awk}
when each new file is processed. In this case, it is very simple; all it
does is initialize a variable @code{fcount} to zero. @code{fcount} tracks
how many lines in the current file matched the pattern.
Naming the parameter @code{junk} shows we know that @code{beginfile()}
is called with a parameter, but that we're not interested in its value:
@example
@c file eg/prog/egrep.awk
function beginfile(junk)
@{
fcount = 0
@}
@c endfile
@end example
The @code{endfile()} function is called after each file has been processed.
It affects the output only when the user wants a count of the number of lines that
matched. @code{no_print} is true only if the exit status is desired.
@code{count_only} is true if line counts are desired. @command{egrep}
therefore only prints line counts if printing and counting are enabled.
The output format must be adjusted depending upon the number of files to
process. Finally, @code{fcount} is added to @code{total}, so that we
know the total number of lines that matched the pattern:
@example
@c file eg/prog/egrep.awk
function endfile(file)
@{
if (! no_print && count_only) @{
if (do_filenames)
print file ":" fcount
else
print fcount
@}
@group
total += fcount
@}
@end group
@c endfile
@end example
The @code{BEGINFILE} and @code{ENDFILE} special patterns
(@pxref{BEGINFILE/ENDFILE}) could be used, but then the program would be
@command{gawk}-specific. Additionally, this example was written before
@command{gawk} acquired @code{BEGINFILE} and @code{ENDFILE}.
The following rule does most of the work of matching lines. The variable
@code{matches} is true if the line matched the pattern. If the user
wants lines that did not match, the sense of @code{matches} is inverted
using the @samp{!} operator. @code{fcount} is incremented with the value of
@code{matches}, which is either one or zero, depending upon a
successful or unsuccessful match. If the line does not match, the
@code{next} statement just moves on to the next record.
A number of additional tests are made, but they are only done if we
are not counting lines. First, if the user only wants the exit status
(@code{no_print} is true), then it is enough to know that @emph{one}
line in this file matched, and we can skip on to the next file with
@code{nextfile}. Similarly, if we are only printing @value{FN}s, we can
print the @value{FN}, and then skip to the next file with @code{nextfile}.
Finally, each line is printed, with a leading @value{FN} and colon
if necessary:
@cindex @code{!} (exclamation point) @subentry @code{!} operator
@cindex exclamation point (@code{!}) @subentry @code{!} operator
@example
@c file eg/prog/egrep.awk
@{
matches = ($0 ~ pattern)
if (invert)
matches = ! matches
fcount += matches # 1 or 0
if (! matches)
next
if (! count_only) @{
if (no_print)
nextfile
if (filenames_only) @{
print FILENAME
nextfile
@}
if (do_filenames)
print FILENAME ":" $0
else
print
@}
@}
@c endfile
@end example
The @code{END} rule takes care of producing the correct exit status. If
there are no matches, the exit status is one; otherwise, it is zero:
@example
@c file eg/prog/egrep.awk
END @{
exit (total == 0)
@}
@c endfile
@end example
The @code{usage()} function prints a usage message in case of invalid options,
and then exits:
@example
@c file eg/prog/egrep.awk
function usage()
@{
print("Usage: egrep [-csvil] [-e pat] [files ...]") > "/dev/stderr"
print("\n\tegrep [-csvil] pat [files ...]") > "/dev/stderr"
exit 1
@}
@c endfile
@end example
@node Id Program
@subsection Printing Out User Information
@cindex printing @subentry user information
@cindex users, information about @subentry printing
@cindex @command{id} utility
The @command{id} utility lists a user's real and effective user ID numbers,
real and effective group ID numbers, and the user's group set, if any.
@command{id} only prints the effective user ID and group ID if they are
different from the real ones. If possible, @command{id} also supplies the
corresponding user and group names. The output might look like this:
@example
$ @kbd{id}
@print{} uid=1000(arnold) gid=1000(arnold) groups=1000(arnold),4(adm),7(lp),27(sudo)
@end example
@cindex @code{PROCINFO} array @subentry user and group ID numbers and
This information is part of what is provided by @command{gawk}'s
@code{PROCINFO} array (@pxref{Built-in Variables}).
However, the @command{id} utility provides a more palatable output than just
individual numbers.
Here is a simple version of @command{id} written in @command{awk}.
It uses the user database library functions
(@pxref{Passwd Functions})
and the group database library functions
(@pxref{Group Functions})
from @ref{Library Functions}.
The program is fairly straightforward. All the work is done in the
@code{BEGIN} rule. The user and group ID numbers are obtained from
@code{PROCINFO}.
The code is repetitive. The entry in the user database for the real user ID
number is split into parts at the @samp{:}. The name is the first field.
Similar code is used for the effective user ID number and the group
numbers:
@cindex @code{id.awk} program
@example
@c file eg/prog/id.awk
# id.awk --- implement id in awk
#
# Requires user and group library functions
@c endfile
@ignore
@c file eg/prog/id.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# May 1993
# Revised February 1996
# Revised May 2014
# Revised September 2014
@c endfile
@end ignore
@c file eg/prog/id.awk
# output is:
# uid=12(foo) euid=34(bar) gid=3(baz) \
# egid=5(blat) groups=9(nine),2(two),1(one)
@group
BEGIN @{
uid = PROCINFO["uid"]
euid = PROCINFO["euid"]
gid = PROCINFO["gid"]
egid = PROCINFO["egid"]
@end group
printf("uid=%d", uid)
pw = getpwuid(uid)
pr_first_field(pw)
@group
if (euid != uid) @{
printf(" euid=%d", euid)
pw = getpwuid(euid)
@end group
@group
pr_first_field(pw)
@}
@end group
printf(" gid=%d", gid)
pw = getgrgid(gid)
pr_first_field(pw)
if (egid != gid) @{
printf(" egid=%d", egid)
pw = getgrgid(egid)
pr_first_field(pw)
@}
for (i = 1; ("group" i) in PROCINFO; i++) @{
if (i == 1)
printf(" groups=")
group = PROCINFO["group" i]
printf("%d", group)
pw = getgrgid(group)
pr_first_field(pw)
if (("group" (i+1)) in PROCINFO)
printf(",")
@}
print ""
@}
function pr_first_field(str, a)
@{
if (str != "") @{
split(str, a, ":")
printf("(%s)", a[1])
@}
@}
@c endfile
@end example
The test in the @code{for} loop is worth noting.
Any supplementary groups in the @code{PROCINFO} array have the
indices @code{"group1"} through @code{"group@var{N}"} for some
@var{N} (i.e., the total number of supplementary groups).
However, we don't know in advance how many of these groups
there are.
This loop works by starting at one, concatenating the value with
@code{"group"}, and then using @code{in} to see if that value is
in the array (@pxref{Reference to Elements}). Eventually, @code{i} is incremented past
the last group in the array and the loop exits.
The loop is also correct if there are @emph{no} supplementary
groups; then the condition is false the first time it's
tested, and the loop body never executes.
The @code{pr_first_field()} function simply isolates out some
code that is used repeatedly, making the whole program
shorter and cleaner. In particular, moving the check for
the empty string into this function saves several lines of code.
@node Split Program
@subsection Splitting a Large File into Pieces
@c FIXME: One day, update to current POSIX version of split
@cindex files @subentry splitting
@cindex @code{split} utility
The @command{split} program splits large text files into smaller pieces.
Usage is as follows:@footnote{This is the traditional usage. The
POSIX usage is different, but not relevant for what the program
aims to demonstrate.}
@display
@command{split} [@code{-@var{count}}] [@var{file}] [@var{prefix}]
@end display
By default,
the output files are named @file{xaa}, @file{xab}, and so on. Each file has
1,000 lines in it, with the likely exception of the last file. To change the
number of lines in each file, supply a number on the command line
preceded with a minus sign (e.g., @samp{-500} for files with 500 lines in them
instead of 1,000). To change the names of the output files to something like
@file{myfileaa}, @file{myfileab}, and so on, supply an additional
argument that specifies the @value{FN} prefix.
Here is a version of @command{split} in @command{awk}. It uses the
@code{ord()} and @code{chr()} functions presented in
@ref{Ordinal Functions}.
The program first sets its defaults, and then tests to make sure there are
not too many arguments. It then looks at each argument in turn. The
first argument could be a minus sign followed by a number. If it is, this happens
to look like a negative number, so it is made positive, and that is the
count of lines. The @value{DF} name is skipped over and the final argument
is used as the prefix for the output @value{FN}s:
@cindex @code{split.awk} program
@example
@c file eg/prog/split.awk
# split.awk --- do split in awk
#
# Requires ord() and chr() library functions
@c endfile
@ignore
@c file eg/prog/split.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# May 1993
# Revised slightly, May 2014
@c endfile
@end ignore
@c file eg/prog/split.awk
# usage: split [-count] [file] [outname]
BEGIN @{
outfile = "x" # default
count = 1000
if (ARGC > 4)
usage()
i = 1
if (i in ARGV && ARGV[i] ~ /^-[[:digit:]]+$/) @{
count = -ARGV[i]
ARGV[i] = ""
i++
@}
# test argv in case reading from stdin instead of file
if (i in ARGV)
i++ # skip datafile name
@group
if (i in ARGV) @{
outfile = ARGV[i]
ARGV[i] = ""
@}
@end group
@group
s1 = s2 = "a"
out = (outfile s1 s2)
@}
@end group
@c endfile
@end example
The next rule does most of the work. @code{tcount} (temporary count) tracks
how many lines have been printed to the output file so far. If it is greater
than @code{count}, it is time to close the current file and start a new one.
@code{s1} and @code{s2} track the current suffixes for the @value{FN}. If
they are both @samp{z}, the file is just too big. Otherwise, @code{s1}
moves to the next letter in the alphabet and @code{s2} starts over again at
@samp{a}:
@c else on separate line here for page breaking
@example
@c file eg/prog/split.awk
@{
if (++tcount > count) @{
close(out)
if (s2 == "z") @{
if (s1 == "z") @{
printf("split: %s is too large to split\n",
FILENAME) > "/dev/stderr"
exit 1
@}
s1 = chr(ord(s1) + 1)
s2 = "a"
@}
@group
else
s2 = chr(ord(s2) + 1)
@end group
out = (outfile s1 s2)
tcount = 1
@}
print > out
@}
@c endfile
@end example
@noindent
The @code{usage()} function simply prints an error message and exits:
@example
@c file eg/prog/split.awk
function usage()
@{
print("usage: split [-num] [file] [outname]") > "/dev/stderr"
exit 1
@}
@c endfile
@end example
This program is a bit sloppy; it relies on @command{awk} to automatically close the last file
instead of doing it in an @code{END} rule.
It also assumes that letters are contiguous in the character set,
which isn't true for EBCDIC systems.
@ifset FOR_PRINT
You might want to consider how to eliminate the use of
@code{ord()} and @code{chr()}; this can be done in such a
way as to solve the EBCDIC issue as well.
@end ifset
@node Tee Program
@subsection Duplicating Output into Multiple Files
@cindex files @subentry multiple, duplicating output into
@cindex output @subentry duplicating into files
@cindex @code{tee} utility
The @code{tee} program is known as a ``pipe fitting.'' @code{tee} copies
its standard input to its standard output and also duplicates it to the
files named on the command line. Its usage is as follows:
@display
@command{tee} [@option{-a}] @var{file} @dots{}
@end display
The @option{-a} option tells @code{tee} to append to the named files, instead of
truncating them and starting over.
The @code{BEGIN} rule first makes a copy of all the command-line arguments
into an array named @code{copy}.
@code{ARGV[0]} is not needed, so it is not copied.
@code{tee} cannot use @code{ARGV} directly, because @command{awk} attempts to
process each @value{FN} in @code{ARGV} as input data.
@cindex flag variables
If the first argument is @option{-a}, then the flag variable
@code{append} is set to true, and both @code{ARGV[1]} and
@code{copy[1]} are deleted. If @code{ARGC} is less than two, then no
@value{FN}s were supplied and @code{tee} prints a usage message and exits.
Finally, @command{awk} is forced to read the standard input by setting
@code{ARGV[1]} to @code{"-"} and @code{ARGC} to two:
@cindex @code{tee.awk} program
@example
@c file eg/prog/tee.awk
# tee.awk --- tee in awk
#
# Copy standard input to all named output files.
# Append content if -a option is supplied.
#
@c endfile
@ignore
@c file eg/prog/tee.awk
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# May 1993
# Revised December 1995
@c endfile
@end ignore
@c file eg/prog/tee.awk
BEGIN @{
for (i = 1; i < ARGC; i++)
copy[i] = ARGV[i]
if (ARGV[1] == "-a") @{
append = 1
delete ARGV[1]
delete copy[1]
ARGC--
@}
if (ARGC < 2) @{
print "usage: tee [-a] file ..." > "/dev/stderr"
exit 1
@}
ARGV[1] = "-"
ARGC = 2
@}
@c endfile
@end example
The following single rule does all the work. Because there is no pattern, it is
executed for each line of input. The body of the rule simply prints the
line into each file on the command line, and then to the standard output:
@example
@c file eg/prog/tee.awk
@{
# moving the if outside the loop makes it run faster
if (append)
for (i in copy)
print >> copy[i]
else
for (i in copy)
print > copy[i]
print
@}
@c endfile
@end example
@noindent
It is also possible to write the loop this way:
@example
@group
for (i in copy)
if (append)
print >> copy[i]
@end group
@group
else
print > copy[i]
@end group
@end example
@noindent
This is more concise, but it is also less efficient. The @samp{if} is
tested for each record and for each output file. By duplicating the loop
body, the @samp{if} is only tested once for each input record. If there are
@var{N} input records and @var{M} output files, the first method only
executes @var{N} @samp{if} statements, while the second executes
@var{N}@code{*}@var{M} @samp{if} statements.
Finally, the @code{END} rule cleans up by closing all the output files:
@example
@c file eg/prog/tee.awk
END @{
for (i in copy)
close(copy[i])
@}
@c endfile
@end example
@node Uniq Program
@subsection Printing Nonduplicated Lines of Text
@c FIXME: One day, update to current POSIX version of uniq
@cindex printing @subentry unduplicated lines of text
@cindex text, printing @subentry unduplicated lines of
@cindex @command{uniq} utility
The @command{uniq} utility reads sorted lines of data on its standard
input, and by default removes duplicate lines. In other words, it only
prints unique lines---hence the name. @command{uniq} has a number of
options. The usage is as follows:
@display
@command{uniq} [@option{-udc} [@code{-@var{n}}]] [@code{+@var{n}}] [@var{inputfile} [@var{outputfile}]]
@end display
The options for @command{uniq} are:
@table @code
@item -d
Print only repeated (duplicated) lines.
@item -u
Print only nonrepeated (unique) lines.
@item -c
Count lines. This option overrides @option{-d} and @option{-u}. Both repeated
and nonrepeated lines are counted.
@item -@var{n}
Skip @var{n} fields before comparing lines. The definition of fields
is similar to @command{awk}'s default: nonwhitespace characters separated
by runs of spaces and/or TABs.
@item +@var{n}
Skip @var{n} characters before comparing lines. Any fields specified with
@samp{-@var{n}} are skipped first.
@item @var{inputfile}
Data is read from the input file named on the command line, instead of from
the standard input.
@item @var{outputfile}
The generated output is sent to the named output file, instead of to the
standard output.
@end table
Normally @command{uniq} behaves as if both the @option{-d} and
@option{-u} options are provided.
@command{uniq} uses the
@code{getopt()} library function
(@pxref{Getopt Function})
and the @code{join()} library function
(@pxref{Join Function}).
The program begins with a @code{usage()} function and then a brief outline of
the options and their meanings in comments.
The @code{BEGIN} rule deals with the command-line arguments and options. It
uses a trick to get @code{getopt()} to handle options of the form @samp{-25},
treating such an option as the option letter @samp{2} with an argument of
@samp{5}. If indeed two or more digits are supplied (@code{Optarg} looks
like a number), @code{Optarg} is
concatenated with the option digit and then the result is added to zero to make
it into a number. If there is only one digit in the option, then
@code{Optarg} is not needed. In this case, @code{Optind} must be decremented so that
@code{getopt()} processes it next time. This code is admittedly a bit
tricky.
If no options are supplied, then the default is taken, to print both
repeated and nonrepeated lines. The output file, if provided, is assigned
to @code{outputfile}. Early on, @code{outputfile} is initialized to the
standard output, @file{/dev/stdout}:
@cindex @code{uniq.awk} program
@example
@c file eg/prog/uniq.awk
@group
# uniq.awk --- do uniq in awk
#
# Requires getopt() and join() library functions
@end group
@c endfile
@ignore
@c file eg/prog/uniq.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# May 1993
@c endfile
@end ignore
@c file eg/prog/uniq.awk
function usage()
@{
print("Usage: uniq [-udc [-n]] [+n] [ in [ out ]]") > "/dev/stderr"
exit 1
@}
# -c count lines. overrides -d and -u
# -d only repeated lines
# -u only nonrepeated lines
# -n skip n fields
# +n skip n characters, skip fields first
BEGIN @{
count = 1
outputfile = "/dev/stdout"
opts = "udc0:1:2:3:4:5:6:7:8:9:"
while ((c = getopt(ARGC, ARGV, opts)) != -1) @{
if (c == "u")
non_repeated_only++
else if (c == "d")
repeated_only++
else if (c == "c")
do_count++
else if (index("0123456789", c) != 0) @{
# getopt() requires args to options
# this messes us up for things like -5
if (Optarg ~ /^[[:digit:]]+$/)
fcount = (c Optarg) + 0
else @{
fcount = c + 0
Optind--
@}
@} else
usage()
@}
@group
if (ARGV[Optind] ~ /^\+[[:digit:]]+$/) @{
charcount = substr(ARGV[Optind], 2) + 0
Optind++
@}
@end group
for (i = 1; i < Optind; i++)
ARGV[i] = ""
if (repeated_only == 0 && non_repeated_only == 0)
repeated_only = non_repeated_only = 1
if (ARGC - Optind == 2) @{
outputfile = ARGV[ARGC - 1]
ARGV[ARGC - 1] = ""
@}
@}
@c endfile
@end example
The following function, @code{are_equal()}, compares the current line,
@code{$0}, to the previous line, @code{last}. It handles skipping fields
and characters. If no field count and no character count are specified,
@code{are_equal()} returns one or zero depending upon the result of a
simple string comparison of @code{last} and @code{$0}.
Otherwise, things get more complicated. If fields have to be skipped,
each line is broken into an array using @code{split()} (@pxref{String
Functions}); the desired fields are then joined back into a line
using @code{join()}. The joined lines are stored in @code{clast} and
@code{cline}. If no fields are skipped, @code{clast} and @code{cline}
are set to @code{last} and @code{$0}, respectively. Finally, if
characters are skipped, @code{substr()} is used to strip off the leading
@code{charcount} characters in @code{clast} and @code{cline}. The two
strings are then compared and @code{are_equal()} returns the result:
@example
@c file eg/prog/uniq.awk
@group
function are_equal( n, m, clast, cline, alast, aline)
@{
if (fcount == 0 && charcount == 0)
return (last == $0)
@end group
if (fcount > 0) @{
n = split(last, alast)
m = split($0, aline)
clast = join(alast, fcount+1, n)
cline = join(aline, fcount+1, m)
@} else @{
clast = last
cline = $0
@}
if (charcount) @{
clast = substr(clast, charcount + 1)
cline = substr(cline, charcount + 1)
@}
@group
return (clast == cline)
@}
@end group
@c endfile
@end example
The following two rules are the body of the program. The first one is
executed only for the very first line of data. It sets @code{last} equal to
@code{$0}, so that subsequent lines of text have something to be compared to.
The second rule does the work. The variable @code{equal} is one or zero,
depending upon the results of @code{are_equal()}'s comparison. If @command{uniq}
is counting repeated lines, and the lines are equal, then it increments the @code{count} variable.
Otherwise, it prints the line and resets @code{count},
because the two lines are not equal.
If @command{uniq} is not counting, and if the lines are equal, @code{count} is incremented.
Nothing is printed, as the point is to remove duplicates.
Otherwise, if @command{uniq} is counting repeated lines and more than
one line is seen, or if @command{uniq} is counting nonrepeated lines
and only one line is seen, then the line is printed, and @code{count}
is reset.
Finally, similar logic is used in the @code{END} rule to print the final
line of input data:
@example
@c file eg/prog/uniq.awk
NR == 1 @{
last = $0
next
@}
@{
equal = are_equal()
if (do_count) @{ # overrides -d and -u
if (equal)
count++
else @{
printf("%4d %s\n", count, last) > outputfile
last = $0
count = 1 # reset
@}
next
@}
if (equal)
count++
else @{
if ((repeated_only && count > 1) ||
(non_repeated_only && count == 1))
print last > outputfile
last = $0
count = 1
@}
@}
END @{
if (do_count)
printf("%4d %s\n", count, last) > outputfile
@group
else if ((repeated_only && count > 1) ||
(non_repeated_only && count == 1))
print last > outputfile
close(outputfile)
@}
@end group
@c endfile
@end example
As a side note, this program does not follow our recommended convention of naming
global variables with a leading capital letter. Doing that would
make the program a little easier to follow.
@ifset FOR_PRINT
The logic for choosing which lines to print represents a @dfn{state
machine}, which is ``a device that can be in one of a set number of stable
conditions depending on its previous condition and on the present values
of its inputs.''@footnote{This is the definition returned from entering
@code{define: state machine} into Google.}
Brian Kernighan suggests that
``an alternative approach to state machines is to just read
the input into an array, then use indexing. It's almost always
easier code, and for most inputs where you would use this, just
as fast.'' Consider how to rewrite the logic to follow this
suggestion.
@end ifset
@node Wc Program
@subsection Counting Things
@c FIXME: One day, update to current POSIX version of wc
@cindex counting words, lines, and characters
@cindex input files @subentry counting elements in
@cindex words @subentry counting
@cindex characters @subentry counting
@cindex lines @subentry counting
@cindex @command{wc} utility
The @command{wc} (word count) utility counts lines, words, and characters in
one or more input files. Its usage is as follows:
@display
@command{wc} [@option{-lwc}] [@var{files} @dots{}]
@end display
If no files are specified on the command line, @command{wc} reads its standard
input. If there are multiple files, it also prints total counts for all
the files. The options and their meanings are as follows:
@table @code
@item -l
Count only lines.
@item -w
Count only words.
A ``word'' is a contiguous sequence of nonwhitespace characters, separated
by spaces and/or TABs. Luckily, this is the normal way @command{awk} separates
fields in its input data.
@item -c
Count only characters.
@end table
Implementing @command{wc} in @command{awk} is particularly elegant,
because @command{awk} does a lot of the work for us; it splits lines into
words (i.e., fields) and counts them, it counts lines (i.e., records),
and it can easily tell us how long a line is.
This program uses the @code{getopt()} library function
(@pxref{Getopt Function})
and the file-transition functions
(@pxref{Filetrans Function}).
This version has one notable difference from traditional versions of
@command{wc}: it always prints the counts in the order lines, words,
and characters. Traditional versions note the order of the @option{-l},
@option{-w}, and @option{-c} options on the command line, and print the
counts in that order.
The @code{BEGIN} rule does the argument processing. The variable
@code{print_total} is true if more than one file is named on the
command line:
@cindex @code{wc.awk} program
@example
@c file eg/prog/wc.awk
# wc.awk --- count lines, words, characters
@c endfile
@ignore
@c file eg/prog/wc.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# May 1993
@c endfile
@end ignore
@c file eg/prog/wc.awk
# Options:
# -l only count lines
# -w only count words
# -c only count characters
#
# Default is to count lines, words, characters
#
# Requires getopt() and file transition library functions
BEGIN @{
# let getopt() print a message about
# invalid options. we ignore them
while ((c = getopt(ARGC, ARGV, "lwc")) != -1) @{
if (c == "l")
do_lines = 1
else if (c == "w")
do_words = 1
else if (c == "c")
do_chars = 1
@}
for (i = 1; i < Optind; i++)
ARGV[i] = ""
# if no options, do all
if (! do_lines && ! do_words && ! do_chars)
do_lines = do_words = do_chars = 1
print_total = (ARGC - i > 1)
@}
@c endfile
@end example
The @code{beginfile()} function is simple; it just resets the counts of lines,
words, and characters to zero, and saves the current @value{FN} in
@code{fname}:
@example
@c file eg/prog/wc.awk
function beginfile(file)
@{
lines = words = chars = 0
fname = FILENAME
@}
@c endfile
@end example
The @code{endfile()} function adds the current file's numbers to the
running totals of lines, words, and characters. It then prints out those
numbers for the file that was just read. It relies on @code{beginfile()}
to reset the numbers for the following @value{DF}:
@example
@c file eg/prog/wc.awk
function endfile(file)
@{
tlines += lines
twords += words
tchars += chars
if (do_lines)
printf "\t%d", lines
@group
if (do_words)
printf "\t%d", words
@end group
if (do_chars)
printf "\t%d", chars
printf "\t%s\n", fname
@}
@c endfile
@end example
There is one rule that is executed for each line. It adds the length of
the record, plus one, to @code{chars}.@footnote{Because @command{gawk}
understands multibyte locales, this code counts characters, not bytes.}
Adding one plus the record length
is needed because the newline character separating records (the value
of @code{RS}) is not part of the record itself, and thus not included
in its length. Next, @code{lines} is incremented for each line read,
and @code{words} is incremented by the value of @code{NF}, which is the
number of ``words'' on this line:
@example
@c file eg/prog/wc.awk
# do per line
@{
chars += length($0) + 1 # get newline
lines++
words += NF
@}
@c endfile
@end example
Finally, the @code{END} rule simply prints the totals for all the files:
@example
@c file eg/prog/wc.awk
END @{
if (print_total) @{
if (do_lines)
printf "\t%d", tlines
if (do_words)
printf "\t%d", twords
if (do_chars)
printf "\t%d", tchars
print "\ttotal"
@}
@}
@c endfile
@end example
@node Miscellaneous Programs
@section A Grab Bag of @command{awk} Programs
This @value{SECTION} is a large ``grab bag'' of miscellaneous programs.
We hope you find them both interesting and enjoyable.
@menu
* Dupword Program:: Finding duplicated words in a document.
* Alarm Program:: An alarm clock.
* Translate Program:: A program similar to the @command{tr} utility.
* Labels Program:: Printing mailing labels.
* Word Sorting:: A program to produce a word usage count.
* History Sorting:: Eliminating duplicate entries from a history
file.
* Extract Program:: Pulling out programs from Texinfo source
files.
* Simple Sed:: A Simple Stream Editor.
* Igawk Program:: A wrapper for @command{awk} that includes
files.
* Anagram Program:: Finding anagrams from a dictionary.
* Signature Program:: People do amazing things with too much time on
their hands.
@end menu
@node Dupword Program
@subsection Finding Duplicated Words in a Document
@cindex words @subentry duplicate, searching for
@cindex searching @subentry for words
@cindex documents, searching
A common error when writing large amounts of prose is to accidentally
duplicate words. Typically you will see this in text as something like ``the
the program does the following@dots{}'' When the text is online, often
the duplicated words occur at the end of one line and the
@iftex
the
@end iftex
beginning of
another, making them very difficult to spot.
@c as here!
This program, @file{dupword.awk}, scans through a file one line at a time
and looks for adjacent occurrences of the same word. It also saves the last
word on a line (in the variable @code{prev}) for comparison with the first
word on the next line.
@cindex Texinfo
The first two statements make sure that the line is all lowercase,
so that, for example, ``The'' and ``the'' compare equal to each other.
The next statement replaces nonalphanumeric and nonwhitespace characters
with spaces, so that punctuation does not affect the comparison either.
The characters are replaced with spaces so that formatting controls
don't create nonsense words (e.g., the Texinfo @samp{@@code@{NF@}}
becomes @samp{codeNF} if punctuation is simply deleted). The record is
then resplit into fields, yielding just the actual words on the line,
and ensuring that there are no empty fields.
If there are no fields left after removing all the punctuation, the
current record is skipped. Otherwise, the program loops through each
word, comparing it to the previous one:
@cindex @code{dupword.awk} program
@example
@c file eg/prog/dupword.awk
# dupword.awk --- find duplicate words in text
@c endfile
@ignore
@c file eg/prog/dupword.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# December 1991
# Revised October 2000
@c endfile
@end ignore
@c file eg/prog/dupword.awk
@{
$0 = tolower($0)
gsub(/[^[:alnum:][:blank:]]/, " ");
$0 = $0 # re-split
if (NF == 0)
next
if ($1 == prev)
printf("%s:%d: duplicate %s\n",
FILENAME, FNR, $1)
for (i = 2; i <= NF; i++)
if ($i == $(i-1))
printf("%s:%d: duplicate %s\n",
FILENAME, FNR, $i)
prev = $NF
@}
@c endfile
@end example
@node Alarm Program
@subsection An Alarm Clock Program
@cindex insomnia, cure for
@cindex Robbins @subentry Arnold
@quotation
@i{Nothing cures insomnia like a ringing alarm clock.}
@author Arnold Robbins
@end quotation
@cindex Quanstrom, Erik
@ignore
Date: Sat, 15 Feb 2014 16:47:09 -0500
Subject: Re: 9atom install question
Message-ID: <l2jcvx6j6mey60xnrkb0hhob.1392500829294@email.android.com>
From: Erik Quanstrom <quanstro@quanstro.net>
To: Aharon Robbins <arnold@skeeve.com>
yes.
- erik
Aharon Robbins <arnold@skeeve.com> wrote:
>> sleep is for web developers.
>
>Can I quote you, in the gawk manual?
>
>Thanks,
>
>Arnold
@end ignore
@quotation
@i{Sleep is for web developers.}
@author Erik Quanstrom
@end quotation
@cindex time @subentry alarm clock example program
@cindex alarm clock example program
The following program is a simple ``alarm clock'' program.
You give it a time of day and an optional message. At the specified time,
it prints the message on the standard output. In addition, you can give it
the number of times to repeat the message as well as a delay between
repetitions.
This program uses the @code{getlocaltime()} function from
@ref{Getlocaltime Function}.
@cindex ASCII
All the work is done in the @code{BEGIN} rule. The first part is argument
checking and setting of defaults: the delay, the count, and the message to
print. If the user supplied a message without the ASCII BEL
character (known as the ``alert'' character, @code{"\a"}), then it is added to
the message. (On many systems, printing the ASCII BEL generates an
audible alert. Thus, when the alarm goes off, the system calls attention
to itself in case the user is not looking at the computer.)
Just for a change, this program uses a @code{switch} statement
(@pxref{Switch Statement}), but the processing could be done with a series of
@code{if}-@code{else} statements instead.
Here is the program:
@cindex @code{alarm.awk} program
@example
@c file eg/prog/alarm.awk
# alarm.awk --- set an alarm
#
# Requires getlocaltime() library function
@c endfile
@ignore
@c file eg/prog/alarm.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# May 1993
# Revised December 2010
@c endfile
@end ignore
@c file eg/prog/alarm.awk
# usage: alarm time [ "message" [ count [ delay ] ] ]
BEGIN @{
# Initial argument sanity checking
usage1 = "usage: alarm time ['message' [count [delay]]]"
usage2 = sprintf("\t(%s) time ::= hh:mm", ARGV[1])
if (ARGC < 2) @{
print usage1 > "/dev/stderr"
print usage2 > "/dev/stderr"
exit 1
@}
switch (ARGC) @{
case 5:
delay = ARGV[4] + 0
# fall through
case 4:
count = ARGV[3] + 0
# fall through
case 3:
message = ARGV[2]
break
default:
if (ARGV[1] !~ /[[:digit:]]?[[:digit:]]:[[:digit:]]@{2@}/) @{
print usage1 > "/dev/stderr"
print usage2 > "/dev/stderr"
exit 1
@}
break
@}
# set defaults for once we reach the desired time
if (delay == 0)
delay = 180 # 3 minutes
@group
if (count == 0)
count = 5
@end group
if (message == "")
message = sprintf("\aIt is now %s!\a", ARGV[1])
else if (index(message, "\a") == 0)
message = "\a" message "\a"
@c endfile
@end example
The next @value{SECTION} of code turns the alarm time into hours and minutes,
converts it (if necessary) to a 24-hour clock, and then turns that
time into a count of the seconds since midnight. Next it turns the current
time into a count of seconds since midnight. The difference between the two
is how long to wait before setting off the alarm:
@example
@c file eg/prog/alarm.awk
# split up alarm time
split(ARGV[1], atime, ":")
hour = atime[1] + 0 # force numeric
minute = atime[2] + 0 # force numeric
# get current broken down time
getlocaltime(now)
# if time given is 12-hour hours and it's after that
# hour, e.g., `alarm 5:30' at 9 a.m. means 5:30 p.m.,
# then add 12 to real hour
if (hour < 12 && now["hour"] > hour)
hour += 12
# set target time in seconds since midnight
target = (hour * 60 * 60) + (minute * 60)
# get current time in seconds since midnight
current = (now["hour"] * 60 * 60) + \
(now["minute"] * 60) + now["second"]
# how long to sleep for
naptime = target - current
if (naptime <= 0) @{
print "alarm: time is in the past!" > "/dev/stderr"
exit 1
@}
@c endfile
@end example
@cindex @command{sleep} utility
Finally, the program uses the @code{system()} function
(@pxref{I/O Functions})
to call the @command{sleep} utility. The @command{sleep} utility simply pauses
for the given number of seconds. If the exit status is not zero,
the program assumes that @command{sleep} was interrupted and exits. If
@command{sleep} exited with an OK status (zero), then the program prints the
message in a loop, again using @command{sleep} to delay for however many
seconds are necessary:
@example
@c file eg/prog/alarm.awk
# zzzzzz..... go away if interrupted
if (system(sprintf("sleep %d", naptime)) != 0)
exit 1
# time to notify!
command = sprintf("sleep %d", delay)
for (i = 1; i <= count; i++) @{
print message
# if sleep command interrupted, go away
if (system(command) != 0)
break
@}
exit 0
@}
@c endfile
@end example
@node Translate Program
@subsection Transliterating Characters
@cindex characters @subentry transliterating
@cindex @command{tr} utility
The system @command{tr} utility transliterates characters. For example, it is
often used to map uppercase letters into lowercase for further processing:
@example
@var{generate data} | tr 'A-Z' 'a-z' | @var{process data} @dots{}
@end example
@command{tr} requires two lists of characters.@footnote{On some older
systems, including Solaris, the system version of @command{tr} may require
that the lists be written as range expressions enclosed in square brackets
(@samp{[a-z]}) and quoted, to prevent the shell from attempting a
@value{FN} expansion. This is not a feature.} When processing the input, the
first character in the first list is replaced with the first character
in the second list, the second character in the first list is replaced
with the second character in the second list, and so on. If there are
more characters in the ``from'' list than in the ``to'' list, the last
character of the ``to'' list is used for the remaining characters in the
``from'' list.
Once upon a time,
@c early or mid-1989!
a user proposed adding a transliteration function
to @command{gawk}.
@c Wishing to avoid gratuitous new features,
@c at least theoretically
The following program was written to
prove that character transliteration could be done with a user-level
function. This program is not as complete as the system @command{tr} utility,
but it does most of the job.
The @command{translate} program was written long before @command{gawk}
acquired the ability to split each character in a string into separate
array elements. Thus, it makes repeated use of the @code{substr()},
@code{index()}, and @code{gsub()} built-in functions (@pxref{String
Functions}). There are two functions. The first, @code{stranslate()},
takes three arguments:
@table @code
@item from
A list of characters from which to translate
@item to
A list of characters to which to translate
@item target
The string on which to do the translation
@end table
Associative arrays make the translation part fairly easy. @code{t_ar} holds
the ``to'' characters, indexed by the ``from'' characters. Then a simple
loop goes through @code{from}, one character at a time. For each character
in @code{from}, if the character appears in @code{target},
it is replaced with the corresponding @code{to} character.
The @code{translate()} function calls @code{stranslate()}, using @code{$0}
as the target. The main program sets two global variables, @code{FROM} and
@code{TO}, from the command line, and then changes @code{ARGV} so that
@command{awk} reads from the standard input.
Finally, the processing rule simply calls @code{translate()} for each record:
@cindex @code{translate.awk} program
@example
@c file eg/prog/translate.awk
# translate.awk --- do tr-like stuff
@c endfile
@ignore
@c file eg/prog/translate.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# August 1989
# February 2009 - bug fix
@c endfile
@end ignore
@c file eg/prog/translate.awk
# Bugs: does not handle things like tr A-Z a-z; it has
# to be spelled out. However, if `to' is shorter than `from',
# the last character in `to' is used for the rest of `from'.
function stranslate(from, to, target, lf, lt, ltarget, t_ar, i, c,
result)
@{
lf = length(from)
lt = length(to)
ltarget = length(target)
for (i = 1; i <= lt; i++)
t_ar[substr(from, i, 1)] = substr(to, i, 1)
if (lt < lf)
for (; i <= lf; i++)
t_ar[substr(from, i, 1)] = substr(to, lt, 1)
for (i = 1; i <= ltarget; i++) @{
c = substr(target, i, 1)
if (c in t_ar)
c = t_ar[c]
result = result c
@}
return result
@}
function translate(from, to)
@{
return $0 = stranslate(from, to, $0)
@}
# main program
BEGIN @{
@group
if (ARGC < 3) @{
print "usage: translate from to" > "/dev/stderr"
exit
@}
@end group
FROM = ARGV[1]
TO = ARGV[2]
ARGC = 2
ARGV[1] = "-"
@}
@{
translate(FROM, TO)
print
@}
@c endfile
@end example
It is possible to do character transliteration in a user-level
function, but it is not necessarily efficient, and we (the @command{gawk}
developers) started to consider adding a built-in function. However,
shortly after writing this program, we learned that Brian Kernighan
had added the @code{toupper()} and @code{tolower()} functions to his
@command{awk} (@pxref{String Functions}). These functions handle the
vast majority of the cases where character transliteration is necessary,
and so we chose to simply add those functions to @command{gawk} as well
and then leave well enough alone.
An obvious improvement to this program would be to set up the
@code{t_ar} array only once, in a @code{BEGIN} rule. However, this
assumes that the ``from'' and ``to'' lists
will never change throughout the lifetime of the program.
Another obvious improvement is to enable the use of ranges,
such as @samp{a-z}, as allowed by the @command{tr} utility.
Look at the code for @file{cut.awk} (@pxref{Cut Program})
for inspiration.
@node Labels Program
@subsection Printing Mailing Labels
@cindex printing @subentry mailing labels
@cindex mailing labels, printing
Here is a ``real-world''@footnote{``Real world'' is defined as
``a program actually used to get something done.''}
program. This
script reads lists of names and
addresses and generates mailing labels. Each page of labels has 20 labels
on it, two across and 10 down. The addresses are guaranteed to be no more
than five lines of data. Each address is separated from the next by a blank
line.
The basic idea is to read 20 labels' worth of data. Each line of each label
is stored in the @code{line} array. The single rule takes care of filling
the @code{line} array and printing the page when 20 labels have been read.
The @code{BEGIN} rule simply sets @code{RS} to the empty string, so that
@command{awk} splits records at blank lines
(@pxref{Records}).
It sets @code{MAXLINES} to 100, because 100 is the maximum number
of lines on the page
@iftex
(@math{20 @cdot 5 = 100}).
@end iftex
@ifnottex
@ifnotdocbook
(20 * 5 = 100).
@end ifnotdocbook
@end ifnottex
@docbook
(20 ⋅ 5 = 100).
@end docbook
Most of the work is done in the @code{printpage()} function.
The label lines are stored sequentially in the @code{line} array. But they
have to print horizontally: @code{line[1]} next to @code{line[6]},
@code{line[2]} next to @code{line[7]}, and so on. Two loops
accomplish this. The outer loop, controlled by @code{i}, steps through
every 10 lines of data; this is each row of labels. The inner loop,
controlled by @code{j}, goes through the lines within the row.
As @code{j} goes from 0 to 4, @samp{i+j} is the @code{j}th line in
the row, and @samp{i+j+5} is the entry next to it. The output ends up
looking something like this:
@example
line 1 line 6
line 2 line 7
line 3 line 8
line 4 line 9
line 5 line 10
@dots{}
@end example
@noindent
The @code{printf} format string @samp{%-41s} left-aligns
the data and prints it within a fixed-width field.
As a final note, an extra blank line is printed at lines 21 and 61, to keep
the output lined up on the labels. This is dependent on the particular
brand of labels in use when the program was written. You will also note
that there are two blank lines at the top and two blank lines at the bottom.
The @code{END} rule arranges to flush the final page of labels; there may
not have been an even multiple of 20 labels in the data:
@cindex @code{labels.awk} program
@example
@c file eg/prog/labels.awk
# labels.awk --- print mailing labels
@c endfile
@ignore
@c file eg/prog/labels.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# June 1992
# December 2010, minor edits
@c endfile
@end ignore
@c file eg/prog/labels.awk
# Each label is 5 lines of data that may have blank lines.
# The label sheets have 2 blank lines at the top and 2 at
# the bottom.
BEGIN @{ RS = "" ; MAXLINES = 100 @}
function printpage( i, j)
@{
if (Nlines <= 0)
return
printf "\n\n" # header
for (i = 1; i <= Nlines; i += 10) @{
if (i == 21 || i == 61)
print ""
for (j = 0; j < 5; j++) @{
if (i + j > MAXLINES)
break
printf " %-41s %s\n", line[i+j], line[i+j+5]
@}
print ""
@}
printf "\n\n" # footer
delete line
@}
# main rule
@{
if (Count >= 20) @{
printpage()
Count = 0
Nlines = 0
@}
n = split($0, a, "\n")
for (i = 1; i <= n; i++)
line[++Nlines] = a[i]
for (; i <= 5; i++)
line[++Nlines] = ""
Count++
@}
END @{
printpage()
@}
@c endfile
@end example
@node Word Sorting
@subsection Generating Word-Usage Counts
@cindex words @subentry usage counts, generating
When working with large amounts of text, it can be interesting to know
how often different words appear. For example, an author may overuse
certain words, in which case he or she might wish to find synonyms to substitute
for words that appear too often. This @value{SUBSECTION} develops a
program for counting words and presenting the frequency information
in a useful format.
At first glance, a program like this would seem to do the job:
@example
# wordfreq-first-try.awk --- print list of word frequencies
@{
for (i = 1; i <= NF; i++)
freq[$i]++
@}
@group
END @{
for (word in freq)
printf "%s\t%d\n", word, freq[word]
@}
@end group
@end example
The program relies on @command{awk}'s default field-splitting
mechanism to break each line up into ``words'' and uses an
associative array named @code{freq}, indexed by each word, to count
the number of times the word occurs. In the @code{END} rule,
it prints the counts.
This program has several problems that prevent it from being
useful on real text files:
@itemize @value{BULLET}
@item
The @command{awk} language considers upper- and lowercase characters to be
distinct. Therefore, ``bartender'' and ``Bartender'' are not treated
as the same word. This is undesirable, because words are capitalized
if they begin sentences in normal text, and a frequency analyzer should
not be sensitive to capitalization.
@item
Words are detected using the @command{awk} convention that fields are
separated just by whitespace. Other characters in the input (except
newlines) don't have any special meaning to @command{awk}. This means that
punctuation characters count as part of words.
@item
The output does not come out in any useful order. You're more likely to be
interested in which words occur most frequently or in having an alphabetized
table of how frequently each word occurs.
@end itemize
@cindex @command{sort} utility
The first problem can be solved by using @code{tolower()} to remove case
distinctions. The second problem can be solved by using @code{gsub()}
to remove punctuation characters. Finally, we solve the third problem
by using the system @command{sort} utility to process the output of the
@command{awk} script. Here is the new version of the program:
@cindex @code{wordfreq.awk} program
@example
@c file eg/prog/wordfreq.awk
# wordfreq.awk --- print list of word frequencies
@{
$0 = tolower($0) # remove case distinctions
# remove punctuation
gsub(/[^[:alnum:]_[:blank:]]/, "", $0)
for (i = 1; i <= NF; i++)
freq[$i]++
@}
@c endfile
END @{
for (word in freq)
printf "%s\t%d\n", word, freq[word]
@}
@end example
The regexp @code{/[^[:alnum:]_[:blank:]]/} might have been written
@code{/[[:punct:]]/}, but then underscores would also be removed,
and we want to keep them.
Assuming we have saved this program in a file named @file{wordfreq.awk},
and that the data is in @file{file1}, the following pipeline:
@example
awk -f wordfreq.awk file1 | sort -k 2nr
@end example
@noindent
produces a table of the words appearing in @file{file1} in order of
decreasing frequency.
The @command{awk} program suitably massages the
data and produces a word frequency table, which is not ordered.
The @command{awk} script's output is then sorted by the @command{sort}
utility and printed on the screen.
The options given to @command{sort}
specify a sort that uses the second field of each input line (skipping
one field), that the sort keys should be treated as numeric quantities
(otherwise @samp{15} would come before @samp{5}), and that the sorting
should be done in descending (reverse) order.
The @command{sort} could even be done from within the program, by changing
the @code{END} action to:
@example
@c file eg/prog/wordfreq.awk
END @{
sort = "sort -k 2nr"
for (word in freq)
printf "%s\t%d\n", word, freq[word] | sort
close(sort)
@}
@c endfile
@end example
This way of sorting must be used on systems that do not
have true pipes at the command-line (or batch-file) level.
See the general operating system documentation for more information on how
to use the @command{sort} program.
@node History Sorting
@subsection Removing Duplicates from Unsorted Text
@cindex lines @subentry duplicate, removing
The @command{uniq} program
(@pxref{Uniq Program})
removes duplicate lines from @emph{sorted} data.
Suppose, however, you need to remove duplicate lines from a @value{DF} but
that you want to preserve the order the lines are in. A good example of
this might be a shell history file. The history file keeps a copy of all
the commands you have entered, and it is not unusual to repeat a command
several times in a row. Occasionally you might want to compact the history
by removing duplicate entries. Yet it is desirable to maintain the order
of the original commands.
This simple program does the job. It uses two arrays. The @code{data}
array is indexed by the text of each line.
For each line, @code{data[$0]} is incremented.
If a particular line has not
been seen before, then @code{data[$0]} is zero.
In this case, the text of the line is stored in @code{lines[count]}.
Each element of @code{lines} is a unique command, and the indices of
@code{lines} indicate the order in which those lines are encountered.
The @code{END} rule simply prints out the lines, in order:
@cindex Rakitzis, Byron
@cindex @code{histsort.awk} program
@example
@c file eg/prog/histsort.awk
# histsort.awk --- compact a shell history file
# Thanks to Byron Rakitzis for the general idea
@c endfile
@ignore
@c file eg/prog/histsort.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# May 1993
@c endfile
@end ignore
@c file eg/prog/histsort.awk
@group
@{
if (data[$0]++ == 0)
lines[++count] = $0
@}
@end group
@group
END @{
for (i = 1; i <= count; i++)
print lines[i]
@}
@end group
@c endfile
@end example
This program also provides a foundation for generating other useful
information. For example, using the following @code{print} statement in the
@code{END} rule indicates how often a particular command is used:
@example
print data[lines[i]], lines[i]
@end example
@noindent
This works because @code{data[$0]} is incremented each time a line is
seen.
@c rick@openfortress.nl, Tue, 24 Dec 2019 13:43:06 +0100
Rick van Rein offers the following one-liner to do the same job of
removing duplicates from unsorted text:
@example
awk '@{ if (! seen[$0]++) print @}'
@end example
This can be simplified even further, at the risk of becoming
almost too obscure:
@example
awk '! seen[$0]++'
@end example
@noindent
This version uses the expression as a pattern, relying on
@command{awk}'s default action of printing the line when
the pattern is true.
@node Extract Program
@subsection Extracting Programs from Texinfo Source Files
@cindex Texinfo @subentry extracting programs from source files
@cindex files @subentry Texinfo, extracting programs from
@ifnotinfo
Both this chapter and the previous chapter
(@ref{Library Functions})
present a large number of @command{awk} programs.
@end ifnotinfo
@ifinfo
The nodes
@ref{Library Functions},
and @ref{Sample Programs},
are the top level nodes for a large number of @command{awk} programs.
@end ifinfo
If you want to experiment with these programs, it is tedious to type
them in by hand. Here we present a program that can extract parts of a
Texinfo input file into separate files.
@cindex Texinfo
This @value{DOCUMENT} is written in @uref{https://www.gnu.org/software/texinfo/, Texinfo},
the GNU Project's document formatting language.
A single Texinfo source file can be used to produce both
printed documentation, with @TeX{}, and online documentation.
@ifnotinfo
(Texinfo is fully documented in the book
@cite{Texinfo---The GNU Documentation Format},
available from the Free Software Foundation,
and also available @uref{https://www.gnu.org/software/texinfo/manual/texinfo/, online}.)
@end ifnotinfo
@ifinfo
(The Texinfo language is described fully, starting with
@inforef{Top, , Texinfo, texinfo,Texinfo---The GNU Documentation Format}.)
@end ifinfo
For our purposes, it is enough to know three things about Texinfo input
files:
@itemize @value{BULLET}
@item
The ``at'' symbol (@samp{@@}) is special in Texinfo, much as
the backslash (@samp{\}) is in C
or @command{awk}. Literal @samp{@@} symbols are represented in Texinfo source
files as @samp{@@@@}.
@item
Comments start with either @samp{@@c} or @samp{@@comment}.
The file-extraction program works by using special comments that start
at the beginning of a line.
@item
Lines containing @samp{@@group} and @samp{@@end group} commands bracket
example text that should not be split across a page boundary.
(Unfortunately, @TeX{} isn't always smart enough to do things exactly right,
so we have to give it some help.)
@end itemize
The following program, @file{extract.awk}, reads through a Texinfo source
file and does two things, based on the special comments.
Upon seeing @samp{@w{@@c system @dots{}}},
it runs a command, by extracting the command text from the
control line and passing it on to the @code{system()} function
(@pxref{I/O Functions}).
Upon seeing @samp{@@c file @var{filename}}, each subsequent line is sent to
the file @var{filename}, until @samp{@@c endfile} is encountered.
The rules in @file{extract.awk} match either @samp{@@c} or
@samp{@@comment} by letting the @samp{omment} part be optional.
Lines containing @samp{@@group} and @samp{@@end group} are simply removed.
@file{extract.awk} uses the @code{join()} library function
(@pxref{Join Function}).
The example programs in the online Texinfo source for @cite{@value{TITLE}}
(@file{gawktexi.in}) have all been bracketed inside @samp{file} and
@samp{endfile} lines. The @command{gawk} distribution uses a copy of
@file{extract.awk} to extract the sample programs and install many
of them in a standard directory where @command{gawk} can find them.
The Texinfo file looks something like this:
@example
@dots{}
This program has a @@code@{BEGIN@} rule
that prints a nice message:
@@example
@@c file examples/messages.awk
BEGIN @@@{ print "Don't panic!" @@@}
@@c endfile
@@end example
It also prints some final advice:
@@example
@@c file examples/messages.awk
END @@@{ print "Always avoid bored archaeologists!" @@@}
@@c endfile
@@end example
@dots{}
@end example
@file{extract.awk} begins by setting @code{IGNORECASE} to one, so that
mixed upper- and lowercase letters in the directives won't matter.
The first rule handles calling @code{system()}, checking that a command is
given (@code{NF} is at least three) and also checking that the command
exits with a zero exit status, signifying OK:
@cindex @code{extract.awk} program
@example
@c file eg/prog/extract.awk
# extract.awk --- extract files and run programs from Texinfo files
@c endfile
@ignore
@c file eg/prog/extract.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# May 1993
# Revised September 2000
@c endfile
@end ignore
@c file eg/prog/extract.awk
BEGIN @{ IGNORECASE = 1 @}
/^@@c(omment)?[ \t]+system/ @{
if (NF < 3) @{
e = ("extract: " FILENAME ":" FNR)
e = (e ": badly formed `system' line")
print e > "/dev/stderr"
next
@}
$1 = ""
$2 = ""
stat = system($0)
if (stat != 0) @{
e = ("extract: " FILENAME ":" FNR)
e = (e ": warning: system returned " stat)
print e > "/dev/stderr"
@}
@}
@c endfile
@end example
@noindent
The variable @code{e} is used so that the rule
fits nicely on the @value{PAGE}.
The second rule handles moving data into files. It verifies that a
@value{FN} is given in the directive. If the file named is not the
current file, then the current file is closed. Keeping the current file
open until a new file is encountered allows the use of the @samp{>}
redirection for printing the contents, keeping open-file management
simple.
The @code{for} loop does the work. It reads lines using @code{getline}
(@pxref{Getline}).
For an unexpected end-of-file, it calls the @code{@w{unexpected_eof()}}
function. If the line is an ``endfile'' line, then it breaks out of
the loop.
If the line is an @samp{@@group} or @samp{@@end group} line, then it
ignores it and goes on to the next line.
Similarly, comments within examples are also ignored.
Most of the work is in the following few lines. If the line has no @samp{@@}
symbols, the program can print it directly.
Otherwise, each leading @samp{@@} must be stripped off.
To remove the @samp{@@} symbols, the line is split into separate elements of
the array @code{a}, using the @code{split()} function
(@pxref{String Functions}).
The @samp{@@} symbol is used as the separator character.
Each element of @code{a} that is empty indicates two successive @samp{@@}
symbols in the original line. For each two empty elements (@samp{@@@@} in
the original file), we have to add a single @samp{@@} symbol back in.
When the processing of the array is finished, @code{join()} is called with the
value of @code{SUBSEP} (@pxref{Multidimensional}),
to rejoin the pieces back into a single
line. That line is then printed to the output file:
@example
@c file eg/prog/extract.awk
/^@@c(omment)?[ \t]+file/ @{
if (NF != 3) @{
e = ("extract: " FILENAME ":" FNR ": badly formed `file' line")
print e > "/dev/stderr"
next
@}
if ($3 != curfile) @{
if (curfile != "")
filelist[curfile] = 1 # save to close later
curfile = $3
@}
for (;;) @{
if ((getline line) <= 0)
unexpected_eof()
if (line ~ /^@@c(omment)?[ \t]+endfile/)
break
else if (line ~ /^@@(end[ \t]+)?group/)
continue
else if (line ~ /^@@c(omment+)?[ \t]+/)
continue
if (index(line, "@@") == 0) @{
print line > curfile
continue
@}
n = split(line, a, "@@")
# if a[1] == "", means leading @@,
# don't add one back in.
for (i = 2; i <= n; i++) @{
if (a[i] == "") @{ # was an @@@@
a[i] = "@@"
if (a[i+1] == "")
i++
@}
@}
@group
print join(a, 1, n, SUBSEP) > curfile
@}
@}
@end group
@c endfile
@end example
An important thing to note is the use of the @samp{>} redirection.
Output done with @samp{>} only opens the file once; it stays open and
subsequent output is appended to the file
(@pxref{Redirection}).
This makes it easy to mix program text and explanatory prose for the same
sample source file (as has been done here!) without any hassle. The file is
only closed when a new @value{DF} name is encountered or at the end of the
input file.
When a new @value{FN} is encountered, instead of closing the file,
the program saves the name of the current file in @code{filelist}.
This makes it possible to interleave the code for more than one file in
the Texinfo input file. (Previous versions of this program @emph{did}
close the file. But because of the @samp{>} redirection, a file whose
parts were not all one after the other ended up getting clobbered.)
An @code{END} rule then closes all the open files when processing
is finished:
@example
@c file eg/prog/extract.awk
@group
END @{
close(curfile) # close the last one
for (f in filelist) # close all the rest
close(f)
@}
@end group
@c endfile
@end example
Finally, the function @code{@w{unexpected_eof()}} prints an appropriate
error message and then exits:
@example
@c file eg/prog/extract.awk
@group
function unexpected_eof()
@{
printf("extract: %s:%d: unexpected EOF or error\n",
FILENAME, FNR) > "/dev/stderr"
exit 1
@}
@end group
@c endfile
@end example
@node Simple Sed
@subsection A Simple Stream Editor
@cindex @command{sed} utility
@cindex stream editors
The @command{sed} utility is a @dfn{stream editor}, a program that reads a
stream of data, makes changes to it, and passes it on.
It is often used to make global changes to a large file or to a stream
of data generated by a pipeline of commands.
Although @command{sed} is a complicated program in its own right, its most common
use is to perform global substitutions in the middle of a pipeline:
@example
@var{command1} < orig.data | sed 's/old/new/g' | @var{command2} > result
@end example
Here, @samp{s/old/new/g} tells @command{sed} to look for the regexp
@samp{old} on each input line and globally replace it with the text
@samp{new} (i.e., all the occurrences on a line). This is similar to
@command{awk}'s @code{gsub()} function
(@pxref{String Functions}).
The following program, @file{awksed.awk}, accepts at least two command-line
arguments: the pattern to look for and the text to replace it with. Any
additional arguments are treated as @value{DF} names to process. If none
are provided, the standard input is used:
@cindex Brennan, Michael
@cindex @command{awksed.awk} program
@c @cindex simple stream editor
@c @cindex stream editor, simple
@example
@c file eg/prog/awksed.awk
# awksed.awk --- do s/foo/bar/g using just print
# Thanks to Michael Brennan for the idea
@c endfile
@ignore
@c file eg/prog/awksed.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# August 1995
@c endfile
@end ignore
@c file eg/prog/awksed.awk
function usage()
@{
print "usage: awksed pat repl [files...]" > "/dev/stderr"
exit 1
@}
@group
BEGIN @{
# validate arguments
if (ARGC < 3)
usage()
@end group
RS = ARGV[1]
ORS = ARGV[2]
# don't use arguments as files
ARGV[1] = ARGV[2] = ""
@}
@group
# look ma, no hands!
@{
if (RT == "")
printf "%s", $0
else
print
@}
@end group
@c endfile
@end example
The program relies on @command{gawk}'s ability to have @code{RS} be a regexp,
as well as on the setting of @code{RT} to the actual text that terminates the
record (@pxref{Records}).
The idea is to have @code{RS} be the pattern to look for. @command{gawk}
automatically sets @code{$0} to the text between matches of the pattern.
This is text that we want to keep, unmodified. Then, by setting @code{ORS}
to the replacement text, a simple @code{print} statement outputs the
text we want to keep, followed by the replacement text.
There is one wrinkle to this scheme, which is what to do if the last record
doesn't end with text that matches @code{RS}. Using a @code{print}
statement unconditionally prints the replacement text, which is not correct.
However, if the file did not end in text that matches @code{RS}, @code{RT}
is set to the null string. In this case, we can print @code{$0} using
@code{printf}
(@pxref{Printf}).
The @code{BEGIN} rule handles the setup, checking for the right number
of arguments and calling @code{usage()} if there is a problem. Then it sets
@code{RS} and @code{ORS} from the command-line arguments and sets
@code{ARGV[1]} and @code{ARGV[2]} to the null string, so that they are
not treated as @value{FN}s
(@pxref{ARGC and ARGV}).
The @code{usage()} function prints an error message and exits.
Finally, the single rule handles the printing scheme outlined earlier,
using @code{print} or @code{printf} as appropriate, depending upon the
value of @code{RT}.
@node Igawk Program
@subsection An Easy Way to Use Library Functions
@cindex libraries of @command{awk} functions @subentry example program for using
@cindex functions @subentry library @subentry example program for using
In @ref{Include Files}, we saw how @command{gawk} provides a built-in
file-inclusion capability. However, this is a @command{gawk} extension.
This @value{SECTION} provides the motivation for making file inclusion
available for standard @command{awk}, and shows how to do it using a
combination of shell and @command{awk} programming.
Using library functions in @command{awk} can be very beneficial. It
encourages code reuse and the writing of general functions. Programs are
smaller and therefore clearer.
However, using library functions is only easy when writing @command{awk}
programs; it is painful when running them, requiring multiple @option{-f}
options. If @command{gawk} is unavailable, then so too is the @env{AWKPATH}
environment variable and the ability to put @command{awk} functions into a
library directory (@pxref{Options}).
It would be nice to be able to write programs in the following manner:
@example
# library functions
@@include getopt.awk
@@include join.awk
@dots{}
# main program
BEGIN @{
while ((c = getopt(ARGC, ARGV, "a:b:cde")) != -1)
@dots{}
@dots{}
@}
@end example
The following program, @file{igawk.sh}, provides this service.
It simulates @command{gawk}'s searching of the @env{AWKPATH} variable
and also allows @dfn{nested} includes (i.e., a file that is included
with @code{@@include} can contain further @code{@@include} statements).
@command{igawk} makes an effort to only include files once, so that nested
includes don't accidentally include a library function twice.
@command{igawk} should behave just like @command{gawk} externally. This
means it should accept all of @command{gawk}'s command-line arguments,
including the ability to have multiple source files specified via
@option{-f} and the ability to mix command-line and library source files.
The program is written using the POSIX Shell (@command{sh}) command
language.@footnote{Fully explaining the @command{sh} language is beyond
the scope of this book. We provide some minimal explanations, but see
a good shell programming book if you wish to understand things in more
depth.} It works as follows:
@enumerate
@item
Loop through the arguments, saving anything that doesn't represent
@command{awk} source code for later, when the expanded program is run.
@item
For any arguments that do represent @command{awk} text, put the arguments into
a shell variable that will be expanded. There are two cases:
@enumerate a
@item
Literal text, provided with @option{-e} or @option{--source}. This
text is just appended directly.
@item
Source @value{FN}s, provided with @option{-f}. We use a neat trick and
append @samp{@@include @var{filename}} to the shell variable's contents.
Because the file-inclusion program works the way @command{gawk} does, this
gets the text of the file included in the program at the correct point.
@end enumerate
@item
Run an @command{awk} program (naturally) over the shell variable's contents to expand
@code{@@include} statements. The expanded program is placed in a second
shell variable.
@item
Run the expanded program with @command{gawk} and any other original command-line
arguments that the user supplied (such as the @value{DF} names).
@end enumerate
This program uses shell variables extensively: for storing command-line arguments and
the text of the @command{awk} program that will expand the user's program, for the
user's original program, and for the expanded program. Doing so removes some
potential problems that might arise were we to use temporary files instead,
at the cost of making the script somewhat more complicated.
The initial part of the program turns on shell tracing if the first
argument is @samp{debug}.
The next part loops through all the command-line arguments.
There are several cases of interest:
@c @asis for docbook
@table @asis
@item @option{--}
This ends the arguments to @command{igawk}. Anything else should be passed on
to the user's @command{awk} program without being evaluated.
@item @option{-W}
This indicates that the next option is specific to @command{gawk}. To make
argument processing easier, the @option{-W} is appended to the front of the
remaining arguments and the loop continues. (This is an @command{sh}
programming trick. Don't worry about it if you are not familiar with
@command{sh}.)
@item @option{-v}, @option{-F}
These are saved and passed on to @command{gawk}.
@item @option{-f}, @option{--file}, @option{--file=}, @option{-Wfile=}
The @value{FN} is appended to the shell variable @code{program} with an
@code{@@include} statement.
The @command{expr} utility is used to remove the leading option part of the
argument (e.g., @samp{--file=}).
(Typical @command{sh} usage would be to use the @command{echo} and @command{sed}
utilities to do this work. Unfortunately, some versions of @command{echo} evaluate
escape sequences in their arguments, possibly mangling the program text.
Using @command{expr} avoids this problem.)
@item @option{--source}, @option{--source=}, @option{-Wsource=}
The source text is appended to @code{program}.
@item @option{--version}, @option{-Wversion}
@command{igawk} prints its version number, runs @samp{gawk --version}
to get the @command{gawk} version information, and then exits.
@end table
If none of the @option{-f}, @option{--file}, @option{-Wfile}, @option{--source},
or @option{-Wsource} arguments are supplied, then the first nonoption argument
should be the @command{awk} program. If there are no command-line
arguments left, @command{igawk} prints an error message and exits.
Otherwise, the first argument is appended to @code{program}.
In any case, after the arguments have been processed,
the shell variable
@code{program} contains the complete text of the original @command{awk}
program.
The program is as follows:
@cindex @code{igawk.sh} program
@example
@c file eg/prog/igawk.sh
#! /bin/sh
# igawk --- like gawk but do @@include processing
@c endfile
@ignore
@c file eg/prog/igawk.sh
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# July 1993
# December 2010, minor edits
@c endfile
@end ignore
@c file eg/prog/igawk.sh
if [ "$1" = debug ]
then
set -x
shift
fi
# A literal newline, so that program text is formatted correctly
n='
'
# Initialize variables to empty
program=
opts=
while [ $# -ne 0 ] # loop over arguments
do
case $1 in
--) shift
break ;;
-W) shift
# The $@{x?'message here'@} construct prints a
# diagnostic if $x is the null string
set -- -W"$@{@@?'missing operand'@}"
continue ;;
-[vF]) opts="$opts $1 '$@{2?'missing operand'@}'"
shift ;;
-[vF]*) opts="$opts '$1'" ;;
-f) program="$program$n@@include $@{2?'missing operand'@}"
shift ;;
-f*) f=$(expr "$1" : '-f\(.*\)')
program="$program$n@@include $f" ;;
-[W-]file=*)
f=$(expr "$1" : '-.file=\(.*\)')
program="$program$n@@include $f" ;;
-[W-]file)
program="$program$n@@include $@{2?'missing operand'@}"
shift ;;
-[W-]source=*)
t=$(expr "$1" : '-.source=\(.*\)')
program="$program$n$t" ;;
-[W-]source)
program="$program$n$@{2?'missing operand'@}"
shift ;;
-[W-]version)
echo igawk: version 3.0 1>&2
gawk --version
exit 0 ;;
-[W-]*) opts="$opts '$1'" ;;
*) break ;;
esac
shift
done
if [ -z "$program" ]
then
program=$@{1?'missing program'@}
shift
fi
# At this point, `program' has the program.
@c endfile
@end example
The @command{awk} program to process @code{@@include} directives
is stored in the shell variable @code{expand_prog}. Doing this keeps
the shell script readable. The @command{awk} program
reads through the user's program, one line at a time, using @code{getline}
(@pxref{Getline}). The input
@value{FN}s and @code{@@include} statements are managed using a stack.
As each @code{@@include} is encountered, the current @value{FN} is
``pushed'' onto the stack and the file named in the @code{@@include}
directive becomes the current @value{FN}. As each file is finished,
the stack is ``popped,'' and the previous input file becomes the current
input file again. The process is started by making the original file
the first one on the stack.
The @code{pathto()} function does the work of finding the full path to
a file. It simulates @command{gawk}'s behavior when searching the
@env{AWKPATH} environment variable
(@pxref{AWKPATH Variable}).
If a @value{FN} has a @samp{/} in it, no path search is done.
Similarly, if the @value{FN} is @code{"-"}, then that string is
used as-is. Otherwise,
the @value{FN} is concatenated with the name of each directory in
the path, and an attempt is made to open the generated @value{FN}.
The only way to test if a file can be read in @command{awk} is to go
ahead and try to read it with @code{getline}; this is what @code{pathto()}
does.@footnote{On some very old versions of @command{awk}, the test
@samp{getline junk < t} can loop forever if the file exists but is empty.}
If the file can be read, it is closed and the @value{FN}
is returned:
@ignore
An alternative way to test for the file's existence would be to call
@samp{system("test -r " t)}, which uses the @command{test} utility to
see if the file exists and is readable. The disadvantage to this method
is that it requires creating an extra process and can thus be slightly
slower.
@end ignore
@example
@c file eg/prog/igawk.sh
expand_prog='
function pathto(file, i, t, junk)
@{
if (index(file, "/") != 0)
return file
if (file == "-")
return file
for (i = 1; i <= ndirs; i++) @{
t = (pathlist[i] "/" file)
@group
if ((getline junk < t) > 0) @{
# found it
close(t)
return t
@}
@end group
@}
return ""
@}
@c endfile
@end example
The main program is contained inside one @code{BEGIN} rule. The first thing it
does is set up the @code{pathlist} array that @code{pathto()} uses. After
splitting the path on @samp{:}, null elements are replaced with @code{"."},
which represents the current directory:
@example
@c file eg/prog/igawk.sh
BEGIN @{
path = ENVIRON["AWKPATH"]
ndirs = split(path, pathlist, ":")
for (i = 1; i <= ndirs; i++) @{
if (pathlist[i] == "")
pathlist[i] = "."
@}
@c endfile
@end example
The stack is initialized with @code{ARGV[1]}, which will be @code{"/dev/stdin"}.
The main loop comes next. Input lines are read in succession. Lines that
do not start with @code{@@include} are printed verbatim.
If the line does start with @code{@@include}, the @value{FN} is in @code{$2}.
@code{pathto()} is called to generate the full path. If it cannot, then the program
prints an error message and continues.
The next thing to check is if the file is included already. The
@code{processed} array is indexed by the full @value{FN} of each included
file and it tracks this information for us. If the file is
seen again, a warning message is printed. Otherwise, the new @value{FN} is
pushed onto the stack and processing continues.
Finally, when @code{getline} encounters the end of the input file, the file
is closed and the stack is popped. When @code{stackptr} is less than zero,
the program is done:
@example
@c file eg/prog/igawk.sh
stackptr = 0
input[stackptr] = ARGV[1] # ARGV[1] is first file
for (; stackptr >= 0; stackptr--) @{
while ((getline < input[stackptr]) > 0) @{
if (tolower($1) != "@@include") @{
print
continue
@}
fpath = pathto($2)
if (fpath == "") @{
printf("igawk: %s:%d: cannot find %s\n",
input[stackptr], FNR, $2) > "/dev/stderr"
continue
@}
if (! (fpath in processed)) @{
processed[fpath] = input[stackptr]
input[++stackptr] = fpath # push onto stack
@} else
print $2, "included in", input[stackptr],
"already included in",
processed[fpath] > "/dev/stderr"
@}
close(input[stackptr])
@}
@}' # close quote ends `expand_prog' variable
processed_program=$(gawk -- "$expand_prog" /dev/stdin << EOF
$program
EOF
)
@c endfile
@end example
The shell construct @samp{@var{command} << @var{marker}} is called
a @dfn{here document}. Everything in the shell script up to the
@var{marker} is fed to @var{command} as input. The shell processes
the contents of the here document for variable and command substitution
(and possibly other things as well, depending upon the shell).
The shell construct @samp{$(@dots{})} is called @dfn{command substitution}.
The output of the command inside the parentheses is substituted
into the command line.
Because the result is used in a variable assignment,
it is saved as a single string, even if the results contain whitespace.
The expanded program is saved in the variable @code{processed_program}.
It's done in these steps:
@enumerate
@item
Run @command{gawk} with the @code{@@include}-processing program (the
value of the @code{expand_prog} shell variable) reading standard input.
@item
Standard input is the contents of the user's program,
from the shell variable @code{program}.
Feed its contents to @command{gawk} via a here document.
@item
Save the results of this processing in the shell variable
@code{processed_program} by using command substitution.
@end enumerate
The last step is to call @command{gawk} with the expanded program,
along with the original
options and command-line arguments that the user supplied:
@example
@c file eg/prog/igawk.sh
eval gawk $opts -- '"$processed_program"' '"$@@"'
@c endfile
@end example
The @command{eval} command is a shell construct that reruns the shell's parsing
process. This keeps things properly quoted.
This version of @command{igawk} represents the fifth version of this program.
There are four key simplifications that make the program work better:
@itemize @value{BULLET}
@item
Using @code{@@include} even for the files named with @option{-f} makes building
the initial collected @command{awk} program much simpler; all the
@code{@@include} processing can be done once.
@item
Not trying to save the line read with @code{getline}
in the @code{pathto()} function when testing for the
file's accessibility for use with the main program simplifies things
considerably.
@item
Using a @code{getline} loop in the @code{BEGIN} rule does it all in one
place. It is not necessary to call out to a separate loop for processing
nested @code{@@include} statements.
@item
Instead of saving the expanded program in a temporary file, putting it in a shell variable
avoids some potential security problems.
This has the disadvantage that the script relies upon more features
of the @command{sh} language, making it harder to follow for those who
aren't familiar with @command{sh}.
@end itemize
Also, this program illustrates that it is often worthwhile to combine
@command{sh} and @command{awk} programming together. You can usually
accomplish quite a lot, without having to resort to low-level programming
in C or C++, and it is frequently easier to do certain kinds of string
and argument manipulation using the shell than it is in @command{awk}.
Finally, @command{igawk} shows that it is not always necessary to add new
features to a program; they can often be layered on top.@footnote{@command{gawk}
does @code{@@include} processing itself in order to support the use
of @command{awk} programs as Web CGI scripts.}
@node Anagram Program
@subsection Finding Anagrams from a Dictionary
@cindex anagrams, finding
An interesting programming challenge is to
search for @dfn{anagrams} in a
word list (such as
@file{/usr/share/dict/words} on many GNU/Linux systems).
One word is an anagram of another if both words contain
the same letters
(e.g., ``babbling'' and ``blabbing'').
Column 2, Problem C, of Jon Bentley's @cite{Programming Pearls}, Second
Edition, presents an elegant algorithm. The idea is to give words that
are anagrams a common signature, sort all the words together by their
signatures, and then print them. Dr.@: Bentley observes that taking the
letters in each word and sorting them produces those common signatures.
The following program uses arrays of arrays to bring together
words with the same signature and array sorting to print the words
in sorted order:
@cindex @code{anagram.awk} program
@example
@c file eg/prog/anagram.awk
# anagram.awk --- An implementation of the anagram-finding algorithm
# from Jon Bentley's "Programming Pearls," 2nd edition.
# Addison Wesley, 2000, ISBN 0-201-65788-0.
# Column 2, Problem C, section 2.8, pp 18-20.
@c endfile
@ignore
@c file eg/prog/anagram.awk
#
# This program requires gawk 4.0 or newer.
# Required gawk-specific features:
# - True multidimensional arrays
# - split() with "" as separator splits out individual characters
# - asort() and asorti() functions
#
# See https://savannah.gnu.org/projects/gawk.
#
# Arnold Robbins
# arnold@@skeeve.com
# Public Domain
# January, 2011
@c endfile
@end ignore
@c file eg/prog/anagram.awk
/'s$/ @{ next @} # Skip possessives
@c endfile
@end example
The program starts with a header, and then a rule to skip
possessives in the dictionary file. The next rule builds
up the data structure. The first dimension of the array
is indexed by the signature; the second dimension is the word
itself:
@example
@c file eg/prog/anagram.awk
@{
key = word2key($1) # Build signature
data[key][$1] = $1 # Store word with signature
@}
@c endfile
@end example
The @code{word2key()} function creates the signature.
It splits the word apart into individual letters,
sorts the letters, and then joins them back together:
@example
@c file eg/prog/anagram.awk
# word2key --- split word apart into letters, sort, and join back together
function word2key(word, a, i, n, result)
@{
n = split(word, a, "")
asort(a)
for (i = 1; i <= n; i++)
result = result a[i]
return result
@}
@c endfile
@end example
Finally, the @code{END} rule traverses the array
and prints out the anagram lists. It sends the output
to the system @command{sort} command because otherwise
the anagrams would appear in arbitrary order:
@example
@c file eg/prog/anagram.awk
END @{
sort = "sort"
for (key in data) @{
# Sort words with same key
nwords = asorti(data[key], words)
if (nwords == 1)
continue
# And print. Minor glitch: trailing space at end of each line
for (j = 1; j <= nwords; j++)
printf("%s ", words[j]) | sort
print "" | sort
@}
close(sort)
@}
@c endfile
@end example
Here is some partial output when the program is run:
@example
$ @kbd{gawk -f anagram.awk /usr/share/dict/words | grep '^b'}
@dots{}
babbled blabbed
babbler blabber brabble
babblers blabbers brabbles
babbling blabbing
babbly blabby
babel bable
babels beslab
babery yabber
@dots{}
@end example
@node Signature Program
@subsection And Now for Something Completely Different
@cindex signature program
@cindex Brini, Davide
The following program was written by Davide Brini
@c (@email{dave_br@@gmx.com})
and is published on @uref{http://backreference.org/2011/02/03/obfuscated-awk/,
his website}.
It serves as his signature in the Usenet group @code{comp.lang.awk}.
He supplies the following copyright terms:
@quotation
Copyright @copyright{} 2008 Davide Brini
Copying and distribution of the code published in this page, with or without
modification, are permitted in any medium without royalty provided the copyright
notice and this notice are preserved.
@end quotation
Here is the program:
@example
@group
awk 'BEGIN@{O="~"~"~";o="=="=="==";o+=+o;x=O""O;while(X++<=x+o+o)c=c"%c";
printf c,(x-O)*(x-O),x*(x-o)-o,x*(x-O)+x-O-o,+x*(x-O)-x+o,X*(o*o+O)+x-O,
X*(X-x)-o*o,(x+X)*o*o+o,x*(X-x)-O-O,x-O+(O+o+X+x)*(o+O),X*X-X*(x-O)-x+O,
O+X*(o*(o+O)+O),+x+O+X*o,x*(x-o),(o+X+x)*o*o-(x-O-O),O+(X-x)*(X+O),x-O@}'
@end group
@end example
@cindex Johansen, Chris
We leave it to you to determine what the program does. (If you are
truly desperate to understand it, see Chris Johansen's explanation,
which is embedded in the Texinfo source file for this @value{DOCUMENT}.)
@ignore
To: "Arnold Robbins" <arnold@skeeve.com>
Date: Sat, 20 Aug 2011 13:50:46 -0400
Subject: The GNU Awk User's Guide, Section 13.3.11
From: "Chris Johansen" <johansen@main.nc.us>
Message-ID: <op.v0iw6wlv7finx3@asusodin.thrudvang.lan>
Arnold, you don't know me, but we have a tenuous connection. My wife is
Barbara A. Field, FAIA, GIT '65 (B. Arch.).
I have had a couple of paper copies of "Effective Awk Programming" for
years, and now I'm going through a Kindle version of "The GNU Awk User's
Guide" again. When I got to section 13.3.11, I reformatted and lightly
commented Davide Brin's signature script to understand its workings.
It occurs to me that this might have pedagogical value as an example
(although imperfect) of the value of whitespace and comments, and a
starting point for that discussion. It certainly helped _me_ understand
what's going on. You are welcome to it, as-is or modified (subject to
Davide's constraints, of course, which I think I have met).
If I were to include it in a future edition, I would put it at some
distance from section 13.3.11, say, as a note or an appendix, so as not to
be a "spoiler" to the puzzle.
Best regards,
--
Chris Johansen {johansen at main dot nc dot us}
. . . collapsing the probability wave function, sending ripples of
certainty through the space-time continuum.
#! /usr/bin/gawk -f
# From "13.3.11 And Now For Something Completely Different"
# https://www.gnu.org/software/gawk/manual/html_node/Signature-Program.html#Signature-Program
# Copyright @copyright{} 2008 Davide Brini
# Copying and distribution of the code published in this page, with
# or without modification, are permitted in any medium without
# royalty provided the copyright notice and this notice are preserved.
BEGIN {
O = "~" ~ "~"; # 1
o = "==" == "=="; # 1
o += +o; # 2
x = O "" O; # 11
while ( X++ <= x + o + o ) c = c "%c";
# O is 1
# o is 2
# x is 11
# X is 17
# c is "%c%c%c%c%c%c%c%c%c%c%c%c%c%c%c%c"
printf c,
( x - O )*( x - O), # 100 d
x*( x - o ) - o, # 97 a
x*( x - O ) + x - O - o, # 118 v
+x*( x - O ) - x + o, # 101 e
X*( o*o + O ) + x - O, # 95 _
X*( X - x ) - o*o, # 98 b
( x + X )*o*o + o, # 114 r
x*( X - x ) - O - O, # 64 @
x - O + ( O + o + X + x )*( o + O ), # 103 g
X*X - X*( x - O ) - x + O, # 109 m
O + X*( o*( o + O ) + O ), # 120 x
+x + O + X*o, # 46 .
x*( x - o), # 99 c
( o + X + x )*o*o - ( x - O - O ), # 111 0
O + ( X - x )*( X + O ), # 109 m
x - O # 10 \n
}
@end ignore
@node Programs Summary
@section Summary
@itemize @value{BULLET}
@item
The programs provided in this @value{CHAPTER}
continue on the theme that reading programs is an excellent way to learn
Good Programming.
@item
Using @samp{#!} to make @command{awk} programs directly runnable makes
them easier to use. Otherwise, invoke the program using @samp{awk
-f @dots{}}.
@item
Reimplementing standard POSIX programs in @command{awk} is a pleasant
exercise; @command{awk}'s expressive power lets you write such programs
in relatively few lines of code, yet they are functionally complete
and usable.
@item
One of standard @command{awk}'s weaknesses is working with individual
characters. The ability to use @code{split()} with the empty string as
the separator can considerably simplify such tasks.
@item
The examples here demonstrate the usefulness of the library
functions from @ref{Library Functions}
for a number of real (if small) programs.
@item
Besides reinventing POSIX wheels, other programs solved a selection of
interesting problems, such as finding duplicate words in text, printing
mailing labels, and finding anagrams.
@end itemize
@c EXCLUDE START
@node Programs Exercises
@section Exercises
@enumerate
@item
Rewrite @file{cut.awk} (@pxref{Cut Program})
using @code{split()} with @code{""} as the separator.
@item
In @ref{Egrep Program}, we mentioned that @samp{egrep -i} could be
simulated in versions of @command{awk} without @code{IGNORECASE} by
using @code{tolower()} on the line and the pattern. In a footnote there,
we also mentioned that this solution has a bug: the translated line is
output, and not the original one. Fix this problem.
@c Exercise: Fix this, w/array and new line as key to original line
@item
The POSIX version of @command{id} takes options that control which
information is printed. Modify the @command{awk} version
(@pxref{Id Program}) to accept the same arguments and perform in the
same way.
@item
The @code{split.awk} program (@pxref{Split Program}) assumes
that letters are contiguous in the character set,
which isn't true for EBCDIC systems.
Fix this problem.
(Hint: Consider a different way to work through the alphabet,
without relying on @code{ord()} and @code{chr()}.)
@item
In @file{uniq.awk} (@pxref{Uniq Program}, the
logic for choosing which lines to print represents a @dfn{state
machine}, which is ``a device that can be in one of a set number of stable
conditions depending on its previous condition and on the present values
of its inputs.''@footnote{This is the definition returned from entering
@code{define: state machine} into Google.}
Brian Kernighan suggests that
``an alternative approach to state machines is to just read
the input into an array, then use indexing. It's almost always
easier code, and for most inputs where you would use this, just
as fast.'' Rewrite the logic to follow this
suggestion.
@item
Why can't the @file{wc.awk} program (@pxref{Wc Program}) just
use the value of @code{FNR} in @code{endfile()}?
Hint: Examine the code in @ref{Filetrans Function}.
@ignore
@command{wc} can't just use the value of @code{FNR} in
@code{endfile()}. If you examine the code in @ref{Filetrans Function},
you will see that @code{FNR} has already been reset by the time
@code{endfile()} is called.
@end ignore
@item
Manipulation of individual characters in the @command{translate} program
(@pxref{Translate Program}) is painful using standard @command{awk}
functions. Given that @command{gawk} can split strings into individual
characters using @code{""} as the separator, how might you use this
feature to simplify the program?
@item
The @file{extract.awk} program (@pxref{Extract Program}) was written
before @command{gawk} had the @code{gensub()} function. Use it
to simplify the code.
@item
Compare the performance of the @file{awksed.awk} program
(@pxref{Simple Sed}) with the more straightforward:
@example
BEGIN @{
pat = ARGV[1]
repl = ARGV[2]
ARGV[1] = ARGV[2] = ""
@}
@{ gsub(pat, repl); print @}
@end example
@item
What are the advantages and disadvantages of @file{awksed.awk} versus
the real @command{sed} utility?
@ignore
Advantage: egrep regexps
speed (?)
Disadvantage: no & in replacement text
Others?
@end ignore
@item
In @ref{Igawk Program}, we mentioned that not trying to save the line
read with @code{getline} in the @code{pathto()} function when testing
for the file's accessibility for use with the main program simplifies
things considerably. What problem does this engender though?
@c answer, reading from "-" or /dev/stdin
@cindex search paths
@cindex search paths @subentry for source files
@cindex source files, search path for
@cindex files @subentry source, search path for
@cindex directories @subentry searching @subentry for source files
@item
As an additional example of the idea that it is not always necessary to
add new features to a program, consider the idea of having two files in
a directory in the search path:
@table @file
@item default.awk
This file contains a set of default library functions, such
as @code{getopt()} and @code{assert()}.
@item site.awk
This file contains library functions that are specific to a site or
installation; i.e., locally developed functions.
Having a separate file allows @file{default.awk} to change with
new @command{gawk} releases, without requiring the system administrator to
update it each time by adding the local functions.
@end table
One user
@c Karl Berry, karl@ileaf.com, 10/95
suggested that @command{gawk} be modified to automatically read these files
upon startup. Instead, it would be very simple to modify @command{igawk}
to do this. Since @command{igawk} can process nested @code{@@include}
directives, @file{default.awk} could simply contain @code{@@include}
statements for the desired library functions.
Make this change.
@item
Modify @file{anagram.awk} (@pxref{Anagram Program}), to avoid
the use of the external @command{sort} utility.
@end enumerate
@c EXCLUDE END
@ifnotinfo
@part @value{PART3}Moving Beyond Standard @command{awk} with @command{gawk}
@end ifnotinfo
@ifdocbook
Part III focuses on features specific to @command{gawk}.
It contains the following chapters:
@itemize @value{BULLET}
@item
@ref{Namespaces}
@item
@ref{Advanced Features}
@item
@ref{Internationalization}
@item
@ref{Debugger}
@item
@ref{Arbitrary Precision Arithmetic}
@item
@ref{Dynamic Extensions}
@end itemize
@end ifdocbook
@node Advanced Features
@chapter Advanced Features of @command{gawk}
@cindex @command{gawk} @subentry features @subentry advanced
@cindex advanced features @subentry @command{gawk}
@ignore
Contributed by: Peter Langston <pud!psl@bellcore.bellcore.com>
Found in Steve English's "signature" line:
"Write documentation as if whoever reads it is a violent psychopath
who knows where you live."
@end ignore
@cindex Langston, Peter
@cindex English, Steve
@quotation
@i{Write documentation as if whoever reads it is
a violent psychopath who knows where you live.}
@author Steve English, as quoted by Peter Langston
@end quotation
This @value{CHAPTER} discusses advanced features in @command{gawk}.
It's a bit of a ``grab bag'' of items that are otherwise unrelated
to each other.
First, we look at a command-line option that allows @command{gawk} to recognize
nondecimal numbers in input data, not just in @command{awk}
programs.
Then, @command{gawk}'s special features for sorting arrays are presented.
Next, two-way I/O, discussed briefly in earlier parts of this
@value{DOCUMENT}, is described in full detail, along with the basics
of TCP/IP networking. Finally, we see how @command{gawk}
can @dfn{profile} an @command{awk} program, making it possible to tune
it for performance.
@c FULLXREF ON
Additional advanced features are discussed in separate @value{CHAPTER}s of their
own:
@itemize @value{BULLET}
@item
@ref{Internationalization}, discusses how to internationalize
your @command{awk} programs, so that they can speak multiple
national languages.
@item
@ref{Debugger}, describes @command{gawk}'s built-in command-line
debugger for debugging @command{awk} programs.
@item
@ref{Arbitrary Precision Arithmetic}, describes how you can use
@command{gawk} to perform arbitrary-precision arithmetic.
@item
@ref{Dynamic Extensions},
discusses the ability to dynamically add new built-in functions to
@command{gawk}.
@end itemize
@c FULLXREF OFF
@menu
* Nondecimal Data:: Allowing nondecimal input data.
* Array Sorting:: Facilities for controlling array traversal and
sorting arrays.
* Two-way I/O:: Two-way communications with another process.
* TCP/IP Networking:: Using @command{gawk} for network programming.
* Profiling:: Profiling your @command{awk} programs.
* Advanced Features Summary:: Summary of advanced features.
@end menu
@node Nondecimal Data
@section Allowing Nondecimal Input Data
@cindex @option{--non-decimal-data} option
@cindex advanced features @subentry nondecimal input data
@cindex input @subentry data, nondecimal
@cindex constants @subentry nondecimal
If you run @command{gawk} with the @option{--non-decimal-data} option,
you can have nondecimal values in your input data:
@example
$ @kbd{echo 0123 123 0x123 |}
> @kbd{gawk --non-decimal-data '@{ printf "%d, %d, %d\n", $1, $2, $3 @}'}
@print{} 83, 123, 291
@end example
For this feature to work, write your program so that
@command{gawk} treats your data as numeric:
@example
$ @kbd{echo 0123 123 0x123 | gawk '@{ print $1, $2, $3 @}'}
@print{} 0123 123 0x123
@end example
@noindent
The @code{print} statement treats its expressions as strings.
Although the fields can act as numbers when necessary,
they are still strings, so @code{print} does not try to treat them
numerically. You need to add zero to a field to force it to
be treated as a number. For example:
@example
$ @kbd{echo 0123 123 0x123 | gawk --non-decimal-data '}
> @kbd{@{ print $1, $2, $3}
> @kbd{print $1 + 0, $2 + 0, $3 + 0 @}'}
@print{} 0123 123 0x123
@print{} 83 123 291
@end example
Because it is common to have decimal data with leading zeros, and because
using this facility could lead to surprising results, the default is to leave it
disabled. If you want it, you must explicitly request it.
@cindex programming conventions @subentry @code{--non-decimal-data} option
@cindex @option{--non-decimal-data} option @subentry @code{strtonum()} function and
@cindex @code{strtonum()} function (@command{gawk}) @subentry @code{--non-decimal-data} option and
@quotation CAUTION
@emph{Use of this option is not recommended.}
It can break old programs very badly.
Instead, use the @code{strtonum()} function to convert your data
(@pxref{String Functions}).
This makes your programs easier to write and easier to read, and
leads to less surprising results.
This option may disappear in a future version of @command{gawk}.
@end quotation
@node Array Sorting
@section Controlling Array Traversal and Array Sorting
@command{gawk} lets you control the order in which a
@samp{for (@var{indx} in @var{array})}
loop traverses an array.
In addition, two built-in functions, @code{asort()} and @code{asorti()},
let you sort arrays based on the array values and indices, respectively.
These two functions also provide control over the sorting criteria used
to order the elements during sorting.
@menu
* Controlling Array Traversal:: How to use PROCINFO["sorted_in"].
* Array Sorting Functions:: How to use @code{asort()} and @code{asorti()}.
@end menu
@node Controlling Array Traversal
@subsection Controlling Array Traversal
By default, the order in which a @samp{for (@var{indx} in @var{array})} loop
scans an array is not defined; it is generally based upon
the internal implementation of arrays inside @command{awk}.
Often, though, it is desirable to be able to loop over the elements
in a particular order that you, the programmer, choose. @command{gawk}
lets you do this.
@ref{Controlling Scanning} describes how you can assign special,
predefined values to @code{PROCINFO["sorted_in"]} in order to
control the order in which @command{gawk} traverses an array
during a @code{for} loop.
In addition, the value of @code{PROCINFO["sorted_in"]} can be a
function name.@footnote{This is why the predefined sorting orders
start with an @samp{@@} character, which cannot be part of an identifier.}
This lets you traverse an array based on any custom criterion.
The array elements are ordered according to the return value of this
function. The comparison function should be defined with at least
four arguments:
@example
function comp_func(i1, v1, i2, v2)
@{
@var{compare elements 1 and 2 in some fashion}
@var{return < 0; 0; or > 0}
@}
@end example
Here, @code{i1} and @code{i2} are the indices, and @code{v1} and @code{v2}
are the corresponding values of the two elements being compared.
Either @code{v1} or @code{v2}, or both, can be arrays if the array being
traversed contains subarrays as values.
(@xref{Arrays of Arrays} for more information about subarrays.)
The three possible return values are interpreted as follows:
@table @code
@item comp_func(i1, v1, i2, v2) < 0
Index @code{i1} comes before index @code{i2} during loop traversal.
@item comp_func(i1, v1, i2, v2) == 0
Indices @code{i1} and @code{i2}
come together, but the relative order with respect to each other is undefined.
@item comp_func(i1, v1, i2, v2) > 0
Index @code{i1} comes after index @code{i2} during loop traversal.
@end table
Our first comparison function can be used to scan an array in
numerical order of the indices:
@example
@group
function cmp_num_idx(i1, v1, i2, v2)
@{
# numerical index comparison, ascending order
return (i1 - i2)
@}
@end group
@end example
Our second function traverses an array based on the string order of
the element values rather than by indices:
@example
function cmp_str_val(i1, v1, i2, v2)
@{
# string value comparison, ascending order
v1 = v1 ""
v2 = v2 ""
if (v1 < v2)
return -1
return (v1 != v2)
@}
@end example
The third
comparison function makes all numbers, and numeric strings without
any leading or trailing spaces, come out first during loop traversal:
@example
function cmp_num_str_val(i1, v1, i2, v2, n1, n2)
@{
# numbers before string value comparison, ascending order
n1 = v1 + 0
n2 = v2 + 0
if (n1 == v1)
return (n2 == v2) ? (n1 - n2) : -1
else if (n2 == v2)
return 1
return (v1 < v2) ? -1 : (v1 != v2)
@}
@end example
Here is a main program to demonstrate how @command{gawk}
behaves using each of the previous functions:
@example
BEGIN @{
data["one"] = 10
data["two"] = 20
data[10] = "one"
data[100] = 100
data[20] = "two"
f[1] = "cmp_num_idx"
f[2] = "cmp_str_val"
f[3] = "cmp_num_str_val"
for (i = 1; i <= 3; i++) @{
printf("Sort function: %s\n", f[i])
PROCINFO["sorted_in"] = f[i]
for (j in data)
printf("\tdata[%s] = %s\n", j, data[j])
print ""
@}
@}
@end example
Here are the results when the program is run:
@example
$ @kbd{gawk -f compdemo.awk}
@print{} Sort function: cmp_num_idx @ii{Sort by numeric index}
@print{} data[two] = 20
@print{} data[one] = 10 @ii{Both strings are numerically zero}
@print{} data[10] = one
@print{} data[20] = two
@print{} data[100] = 100
@print{}
@print{} Sort function: cmp_str_val @ii{Sort by element values as strings}
@print{} data[one] = 10
@print{} data[100] = 100 @ii{String 100 is less than string 20}
@print{} data[two] = 20
@print{} data[10] = one
@print{} data[20] = two
@print{}
@print{} Sort function: cmp_num_str_val @ii{Sort all numeric values before all strings}
@print{} data[one] = 10
@print{} data[two] = 20
@print{} data[100] = 100
@print{} data[10] = one
@print{} data[20] = two
@end example
Consider sorting the entries of a GNU/Linux system password file
according to login name. The following program sorts records
by a specific field position and can be used for this purpose:
@example
# passwd-sort.awk --- simple program to sort by field position
# field position is specified by the global variable POS
function cmp_field(i1, v1, i2, v2)
@{
# comparison by value, as string, and ascending order
return v1[POS] < v2[POS] ? -1 : (v1[POS] != v2[POS])
@}
@{
for (i = 1; i <= NF; i++)
a[NR][i] = $i
@}
@group
END @{
PROCINFO["sorted_in"] = "cmp_field"
@end group
if (POS < 1 || POS > NF)
POS = 1
for (i in a) @{
for (j = 1; j <= NF; j++)
printf("%s%c", a[i][j], j < NF ? ":" : "")
print ""
@}
@}
@end example
The first field in each entry of the password file is the user's login name,
and the fields are separated by colons.
Each record defines a subarray,
with each field as an element in the subarray.
Running the program produces the
following output:
@example
$ @kbd{gawk -v POS=1 -F: -f sort.awk /etc/passwd}
@print{} adm:x:3:4:adm:/var/adm:/sbin/nologin
@print{} apache:x:48:48:Apache:/var/www:/sbin/nologin
@print{} avahi:x:70:70:Avahi daemon:/:/sbin/nologin
@dots{}
@end example
The comparison should normally always return the same value when given a
specific pair of array elements as its arguments. If inconsistent
results are returned, then the order is undefined. This behavior can be
exploited to introduce random order into otherwise seemingly
ordered data:
@example
function cmp_randomize(i1, v1, i2, v2)
@{
# random order (caution: this may never terminate!)
return (2 - 4 * rand())
@}
@end example
As already mentioned, the order of the indices is arbitrary if two
elements compare equal. This is usually not a problem, but letting
the tied elements come out in arbitrary order can be an issue, especially
when comparing item values. The partial ordering of the equal elements
may change the next time the array is traversed, if other elements are added to or
removed from the array. One way to resolve ties when comparing elements
with otherwise equal values is to include the indices in the comparison
rules. Note that doing this may make the loop traversal less efficient,
so consider it only if necessary. The following comparison functions
force a deterministic order, and are based on the fact that the
(string) indices of two elements are never equal:
@example
function cmp_numeric(i1, v1, i2, v2)
@{
# numerical value (and index) comparison, descending order
return (v1 != v2) ? (v2 - v1) : (i2 - i1)
@}
@group
function cmp_string(i1, v1, i2, v2)
@{
# string value (and index) comparison, descending order
v1 = v1 i1
v2 = v2 i2
return (v1 > v2) ? -1 : (v1 != v2)
@}
@end group
@end example
@c Avoid using the term ``stable'' when describing the unpredictable behavior
@c if two items compare equal. Usually, the goal of a "stable algorithm"
@c is to maintain the original order of the items, which is a meaningless
@c concept for a list constructed from a hash.
A custom comparison function can often simplify ordered loop
traversal, and the sky is really the limit when it comes to
designing such a function.
When string comparisons are made during a sort, either for element
values where one or both aren't numbers, or for element indices
handled as strings, the value of @code{IGNORECASE}
(@pxref{Built-in Variables}) controls whether
the comparisons treat corresponding upper- and lowercase letters as
equivalent or distinct.
Another point to keep in mind is that in the case of subarrays,
the element values can themselves be arrays; a production comparison
function should use the @code{isarray()} function
(@pxref{Type Functions})
to check for this, and choose a defined sorting order for subarrays.
@cindex POSIX mode
All sorting based on @code{PROCINFO["sorted_in"]}
is disabled in POSIX mode,
because the @code{PROCINFO} array is not special in that case.
As a side note, sorting the array indices before traversing
the array has been reported to add a 15% to 20% overhead to the
execution time of @command{awk} programs. For this reason,
sorted array traversal is not the default.
@c The @command{gawk}
@c maintainers believe that only the people who wish to use a
@c feature should have to pay for it.
@node Array Sorting Functions
@subsection Sorting Array Values and Indices with @command{gawk}
@cindex arrays @subentry sorting @subentry @code{asort()} function (@command{gawk})
@cindex arrays @subentry sorting @subentry @code{asorti()} function (@command{gawk})
@cindexgawkfunc{asort}
@cindex @code{asort()} function (@command{gawk}) @subentry arrays, sorting
@cindex @code{asort()} function (@command{gawk}) @subentry side effects
@cindexgawkfunc{asorti}
@cindex @code{asorti()} function (@command{gawk}) @subentry arrays, sorting
@cindex @code{asorti()} function (@command{gawk}) @subentry side effects
@cindex sort function, arrays, sorting
In most @command{awk} implementations, sorting an array requires writing
a @code{sort()} function. This can be educational for exploring
different sorting algorithms, but usually that's not the point of the program.
@command{gawk} provides the built-in @code{asort()} and @code{asorti()}
functions (@pxref{String Functions}) for sorting arrays. For example:
@example
@var{populate the array} data
n = asort(data)
for (i = 1; i <= n; i++)
@var{do something with} data[i]
@end example
After the call to @code{asort()}, the array @code{data} is indexed from 1
to some number @var{n}, the total number of elements in @code{data}.
(This count is @code{asort()}'s return value.)
@code{data[1]} @value{LEQ} @code{data[2]} @value{LEQ} @code{data[3]}, and so on.
The default comparison is based on the type of the elements
(@pxref{Typing and Comparison}).
All numeric values come before all string values,
which in turn come before all subarrays.
@cindex side effects @subentry @code{asort()} function
@cindex side effects @subentry @code{asorti()} function
An important side effect of calling @code{asort()} is that
@emph{the array's original indices are irrevocably lost}.
As this isn't always desirable, @code{asort()} accepts a
second argument:
@example
@var{populate the array} source
n = asort(source, dest)
for (i = 1; i <= n; i++)
@var{do something with} dest[i]
@end example
In this case, @command{gawk} copies the @code{source} array into the
@code{dest} array and then sorts @code{dest}, destroying its indices.
However, the @code{source} array is not affected.
Often, what's needed is to sort on the values of the @emph{indices}
instead of the values of the elements. To do that, use the
@code{asorti()} function. The interface and behavior are identical to
that of @code{asort()}, except that the index values are used for sorting
and become the values of the result array:
@example
@{ source[$0] = some_func($0) @}
END @{
n = asorti(source, dest)
for (i = 1; i <= n; i++) @{
@ii{Work with sorted indices directly:}
@var{do something with} dest[i]
@dots{}
@ii{Access original array via sorted indices:}
@var{do something with} source[dest[i]]
@}
@}
@end example
So far, so good. Now it starts to get interesting. Both @code{asort()}
and @code{asorti()} accept a third string argument to control comparison
of array elements. When we introduced @code{asort()} and @code{asorti()}
in @ref{String Functions}, we ignored this third argument; however,
now is the time to describe how this argument affects these two functions.
Basically, the third argument specifies how the array is to be sorted.
There are two possibilities. As with @code{PROCINFO["sorted_in"]},
this argument may be one of the predefined names that @command{gawk}
provides (@pxref{Controlling Scanning}), or it may be the name of a
user-defined function (@pxref{Controlling Array Traversal}).
In the latter case, @emph{the function can compare elements in any way
it chooses}, taking into account just the indices, just the values,
or both. This is extremely powerful.
Once the array is sorted, @code{asort()} takes the @emph{values} in
their final order and uses them to fill in the result array, whereas
@code{asorti()} takes the @emph{indices} in their final order and uses
them to fill in the result array.
@cindex reference counting, sorting arrays
@quotation NOTE
Copying array indices and elements isn't expensive in terms of memory.
Internally, @command{gawk} maintains @dfn{reference counts} to data.
For example, when @code{asort()} copies the first array to the second one,
there is only one copy of the original array elements' data, even though
both arrays use the values.
@end quotation
@c Document It And Call It A Feature. Sigh.
@cindex @command{gawk} @subentry @code{IGNORECASE} variable in
@cindex arrays @subentry sorting @subentry @code{IGNORECASE} variable and
@cindex @code{IGNORECASE} variable @subentry array sorting functions and
Because @code{IGNORECASE} affects string comparisons, the value
of @code{IGNORECASE} also affects sorting for both @code{asort()} and @code{asorti()}.
Note also that the locale's sorting order does @emph{not}
come into play; comparisons are based on character values only.@footnote{This
is true because locale-based comparison occurs only when in
POSIX-compatibility mode, and because @code{asort()} and @code{asorti()} are
@command{gawk} extensions, they are not available in that case.}
The following example demonstrates the use of a comparison function with
@code{asort()}. The comparison function, @code{case_fold_compare()}, maps
both values to lowercase in order to compare them ignoring case.
@example
@group
# case_fold_compare --- compare as strings, ignoring case
function case_fold_compare(i1, v1, i2, v2, l, r)
@{
l = tolower(v1)
@end group
r = tolower(v2)
if (l < r)
return -1
else if (l == r)
return 0
else
return 1
@}
@end example
And here is the test program for it:
@example
# Test program
BEGIN @{
Letters = "abcdefghijklmnopqrstuvwxyz" \
"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
split(Letters, data, "")
asort(data, result, "case_fold_compare")
j = length(result)
for (i = 1; i <= j; i++) @{
printf("%s", result[i])
if (i % (j/2) == 0)
printf("\n")
else
printf(" ")
@}
@}
@end example
When run, we get the following:
@example
$ @kbd{gawk -f case_fold_compare.awk}
@print{} A a B b c C D d e E F f g G H h i I J j k K l L M m
@print{} n N O o p P Q q r R S s t T u U V v w W X x y Y z Z
@end example
@node Two-way I/O
@section Two-Way Communications with Another Process
@c 8/2014. Neither Mike nor BWK saw this as relevant. Commenting it out.
@ignore
@cindex Brennan, Michael
@cindex programmers, attractiveness of
@smallexample
@c Path: cssun.mathcs.emory.edu!gatech!newsxfer3.itd.umich.edu!news-peer.sprintlink.net!news-sea-19.sprintlink.net!news-in-west.sprintlink.net!news.sprintlink.net!Sprint!204.94.52.5!news.whidbey.com!brennan
From: brennan@@whidbey.com (Mike Brennan)
Newsgroups: comp.lang.awk
Subject: Re: Learn the SECRET to Attract Women Easily
Date: 4 Aug 1997 17:34:46 GMT
@c Organization: WhidbeyNet
@c Lines: 12
Message-ID: <5s53rm$eca@@news.whidbey.com>
@c References: <5s20dn$2e1@chronicle.concentric.net>
@c Reply-To: brennan@whidbey.com
@c NNTP-Posting-Host: asn202.whidbey.com
@c X-Newsreader: slrn (0.9.4.1 UNIX)
@c Xref: cssun.mathcs.emory.edu comp.lang.awk:5403
On 3 Aug 1997 13:17:43 GMT, Want More Dates???
<tracy78@@kilgrona.com> wrote:
>Learn the SECRET to Attract Women Easily
>
>The SCENT(tm) Pheromone Sex Attractant For Men to Attract Women
The scent of awk programmers is a lot more attractive to women than
the scent of perl programmers.
--
Mike Brennan
@c brennan@@whidbey.com
@end smallexample
@end ignore
@cindex advanced features @subentry processes, communicating with
@cindex processes, two-way communications with
It is often useful to be able to
send data to a separate program for
processing and then read the result. This can always be
done with temporary files:
@example
# Write the data for processing
tempfile = ("mydata." PROCINFO["pid"])
while (@var{not done with data})
print @var{data} | ("subprogram > " tempfile)
close("subprogram > " tempfile)
# Read the results, remove tempfile when done
while ((getline newdata < tempfile) > 0)
@var{process} newdata @var{appropriately}
close(tempfile)
system("rm " tempfile)
@end example
@noindent
This works, but not elegantly. Among other things, it requires that
the program be run in a directory that cannot be shared among users;
for example, @file{/tmp} will not do, as another user might happen
to be using a temporary file with the same name.@footnote{Michael
Brennan suggests the use of @command{rand()} to generate unique
@value{FN}s. This is a valid point; nevertheless, temporary files
remain more difficult to use than two-way pipes.} @c 8/2014
@cindex coprocesses
@cindex input/output @subentry two-way
@cindex @code{|} (vertical bar) @subentry @code{|&} operator (I/O)
@cindex vertical bar (@code{|}) @subentry @code{|&} operator (I/O)
@cindex @command{csh} utility @subentry @code{|&} operator, comparison with
However, with @command{gawk}, it is possible to
open a @emph{two-way} pipe to another process. The second process is
termed a @dfn{coprocess}, as it runs in parallel with @command{gawk}.
The two-way connection is created using the @samp{|&} operator
(borrowed from the Korn shell, @command{ksh}):@footnote{This is very
different from the same operator in the C shell and in Bash.}
@example
do @{
print @var{data} |& "subprogram"
"subprogram" |& getline results
@} while (@var{data left to process})
close("subprogram")
@end example
The first time an I/O operation is executed using the @samp{|&}
operator, @command{gawk} creates a two-way pipeline to a child process
that runs the other program. Output created with @code{print}
or @code{printf} is written to the program's standard input, and
output from the program's standard output can be read by the @command{gawk}
program using @code{getline}.
As is the case with processes started by @samp{|}, the subprogram
can be any program, or pipeline of programs, that can be started by
the shell.
There are some cautionary items to be aware of:
@itemize @value{BULLET}
@item
As the code inside @command{gawk} currently stands, the coprocess's
standard error goes to the same place that the parent @command{gawk}'s
standard error goes. It is not possible to read the child's
standard error separately.
@cindex deadlocks
@cindex buffering @subentry input/output
@cindex @code{getline} command @subentry deadlock and
@item
I/O buffering may be a problem. @command{gawk} automatically
flushes all output down the pipe to the coprocess.
However, if the coprocess does not flush its output,
@command{gawk} may hang when doing a @code{getline} in order to read
the coprocess's results. This could lead to a situation
known as @dfn{deadlock}, where each process is waiting for the
other one to do something.
@end itemize
@cindex @code{close()} function @subentry two-way pipes and
It is possible to close just one end of the two-way pipe to
a coprocess, by supplying a second argument to the @code{close()}
function of either @code{"to"} or @code{"from"}
(@pxref{Close Files And Pipes}).
These strings tell @command{gawk} to close the end of the pipe
that sends data to the coprocess or the end that reads from it,
respectively.
@cindex @command{sort} utility @subentry coprocesses and
This is particularly necessary in order to use
the system @command{sort} utility as part of a coprocess;
@command{sort} must read @emph{all} of its input
data before it can produce any output.
The @command{sort} program does not receive an end-of-file indication
until @command{gawk} closes the write end of the pipe.
When you have finished writing data to the @command{sort}
utility, you can close the @code{"to"} end of the pipe, and
then start reading sorted data via @code{getline}.
For example:
@example
BEGIN @{
command = "LC_ALL=C sort"
n = split("abcdefghijklmnopqrstuvwxyz", a, "")
for (i = n; i > 0; i--)
print a[i] |& command
close(command, "to")
while ((command |& getline line) > 0)
print "got", line
close(command)
@}
@end example
This program writes the letters of the alphabet in reverse order, one
per line, down the two-way pipe to @command{sort}. It then closes the
write end of the pipe, so that @command{sort} receives an end-of-file
indication. This causes @command{sort} to sort the data and write the
sorted data back to the @command{gawk} program. Once all of the data
has been read, @command{gawk} terminates the coprocess and exits.
@cindex ASCII
As a side note, the assignment @samp{LC_ALL=C} in the @command{sort}
command ensures traditional Unix (ASCII) sorting from @command{sort}.
This is not strictly necessary here, but it's good to know how to do this.
Be careful when closing the @code{"from"} end of a two-way pipe; in this
case @command{gawk} waits for the child process to exit, which may cause
your program to hang. (Thus, this particular feature is of much less
use in practice than being able to close the @code{"to"} end.)
@quotation CAUTION
Normally,
it is a fatal error to write to the @code{"to"} end of a two-way
pipe which has been closed, and it is also a fatal error to read
from the @code{"from"} end of a two-way pipe that has been closed.
You may set @code{PROCINFO["@var{command}", "NONFATAL"]} to
make such operations become nonfatal. If you do so, you then need
to check @code{ERRNO} after each @code{print}, @code{printf},
or @code{getline}.
@xref{Nonfatal}, for more information.
@end quotation
@cindex @command{gawk} @subentry @code{PROCINFO} array in
@cindex @code{PROCINFO} array @subentry communications via ptys and
You may also use pseudo-ttys (ptys) for
two-way communication instead of pipes, if your system supports them.
This is done on a per-command basis, by setting a special element
in the @code{PROCINFO} array
(@pxref{Auto-set}),
like so:
@example
command = "sort -nr" # command, save in convenience variable
PROCINFO[command, "pty"] = 1 # update PROCINFO
print @dots{} |& command # start two-way pipe
@dots{}
@end example
@noindent
If your system does not have ptys, or if all the system's ptys are in use,
@command{gawk} automatically falls back to using regular pipes.
Using ptys usually avoids the buffer deadlock issues described earlier,
at some loss in performance. This is because the tty driver buffers
and sends data line-by-line. On systems with the @command{stdbuf}
(part of the @uref{https://www.gnu.org/software/coreutils/coreutils.html,
GNU Coreutils package}), you can use that program instead of ptys.
Note also that ptys are not fully transparent. Certain binary control
codes, such @kbd{Ctrl-d} for end-of-file, are interpreted by the tty
driver and not passed through.
@quotation CAUTION
Finally, coprocesses open up the possibility of @dfn{deadlock} between
@command{gawk} and the program running in the coprocess. This can occur
if you send ``too much'' data to the coprocess before reading any back;
each process is blocked writing data with no one available to read what
they've already written. There is no workaround for deadlock; careful
programming and knowledge of the behavior of the coprocess are required.
@end quotation
@c From email send January 4, 2018.
The following example, due to Andrew Schorr, demonstrates how
using ptys can help deal with buffering deadlocks.
Suppose @command{gawk} were unable to add numbers.
You could use a coprocess to do it. Here's an exceedingly
simple program written for that purpose:
@example
$ @kbd{cat add.c}
#include <stdio.h>
int
main(void)
@{
int x, y;
while (scanf("%d %d", & x, & y) == 2)
printf("%d\n", x + y);
return 0;
@}
$ @kbd{cc -O add.c -o add} @ii{Compile the program}
@end example
You could then write an exceedingly simple @command{gawk} program
to add numbers by passing them to the coprocess:
@example
$ @kbd{echo 1 2 |}
> @kbd{gawk -v cmd=./add '@{ print |& cmd; cmd |& getline x; print x @}'}
@end example
And it would deadlock, because @file{add.c} fails to call
@samp{setlinebuf(stdout)}. The @command{add} program freezes.
Now try instead:
@example
$ @kbd{echo 1 2 |}
> @kbd{gawk -v cmd=add 'BEGIN @{ PROCINFO[cmd, "pty"] = 1 @}}
> @kbd{ @{ print |& cmd; cmd |& getline x; print x @}'}
@print{} 3
@end example
By using a pty, @command{gawk} fools the standard I/O library into
thinking it has an interactive session, so it defaults to line buffering.
And now, magically, it works!
@node TCP/IP Networking
@section Using @command{gawk} for Network Programming
@cindex advanced features @subentry network programming
@cindex networks @subentry programming
@cindex TCP/IP
@cindex @code{/inet/@dots{}} special files (@command{gawk})
@cindex files @subentry @code{/inet/@dots{}} (@command{gawk})
@cindex @code{/inet4/@dots{}} special files (@command{gawk})
@cindex files @subentry @code{/inet4/@dots{}} (@command{gawk})
@cindex @code{/inet6/@dots{}} special files (@command{gawk})
@cindex files @subentry @code{/inet6/@dots{}} (@command{gawk})
@cindex @code{EMRED}
@ifnotdocbook
@quotation
@code{EMRED}:@*
@ @ @ @ @i{A host is a host from coast to coast,@*
@ @ @ @ and nobody talks to a host that's close,@*
@ @ @ @ unless the host that isn't close@*
@ @ @ @ is busy, hung, or dead.}
@author Mike O'Brien (aka Mr.@: Protocol)
@end quotation
@end ifnotdocbook
@docbook
<blockquote>
<attribution>Mike O'Brien (aka Mr. Protocol)</attribution>
<literallayout class="normal"><literal>EMRED</literal>:
<emphasis>A host is a host from coast to coast,</emphasis>
<emphasis>and no-one can talk to host that's close,</emphasis>
<emphasis>unless the host that isn't close</emphasis>
<emphasis>is busy, hung, or dead.</emphasis></literallayout>
</blockquote>
@end docbook
In addition to being able to open a two-way pipeline to a coprocess
on the same system
(@pxref{Two-way I/O}),
it is possible to make a two-way connection to
another process on another system across an IP network connection.
You can think of this as just a @emph{very long} two-way pipeline to
a coprocess.
The way @command{gawk} decides that you want to use TCP/IP networking is
by recognizing special @value{FN}s that begin with one of @samp{/inet/},
@samp{/inet4/}, or @samp{/inet6/}.
The full syntax of the special @value{FN} is
@file{/@var{net-type}/@var{protocol}/@var{local-port}/@var{remote-host}/@var{remote-port}}.
The components are:
@table @var
@item net-type
Specifies the kind of Internet connection to make.
Use @samp{/inet4/} to force IPv4, and
@samp{/inet6/} to force IPv6.
Plain @samp{/inet/} (which used to be the only option) uses
the system default, most likely IPv4.
@item protocol
The protocol to use over IP. This must be either @samp{tcp}, or
@samp{udp}, for a TCP or UDP IP connection,
respectively. TCP should be used for most applications.
@item local-port
@cindex @code{getaddrinfo()} function (C library)
@cindex C library functions @subentry @code{getaddrinfo()}
The local TCP or UDP port number to use. Use a port number of @samp{0}
when you want the system to pick a port. This is what you should do
when writing a TCP or UDP client.
You may also use a well-known service name, such as @samp{smtp}
or @samp{http}, in which case @command{gawk} attempts to determine
the predefined port number using the C @code{getaddrinfo()} function.
@item remote-host
The IP address or fully qualified domain name of the Internet
host to which you want to connect.
@item remote-port
The TCP or UDP port number to use on the given @var{remote-host}.
Again, use @samp{0} if you don't care, or else a well-known
service name.
@end table
@cindex @command{gawk} @subentry @code{ERRNO} variable in
@cindex @code{ERRNO} variable
@quotation NOTE
Failure in opening a two-way socket will result in a nonfatal error
being returned to the calling code. The value of @code{ERRNO} indicates
the error (@pxref{Auto-set}).
@end quotation
Consider the following very simple example:
@example
BEGIN @{
Service = "/inet/tcp/0/localhost/daytime"
Service |& getline
print $0
close(Service)
@}
@end example
This program reads the current date and time from the local system's
TCP @code{daytime} server.
It then prints the results and closes the connection.
Because this topic is extensive, the use of @command{gawk} for
TCP/IP programming is documented separately.
@ifinfo
See
@inforef{Top, , General Introduction, gawkinet, @value{GAWKINETTITLE}},
@end ifinfo
@ifnotinfo
See
@uref{https://www.gnu.org/software/gawk/manual/gawkinet/,
@cite{@value{GAWKINETTITLE}}},
which comes as part of the @command{gawk} distribution,
@end ifnotinfo
for a much more complete introduction and discussion, as well as
extensive examples.
@quotation NOTE
@command{gawk} can only open direct sockets. There is currently
no way to access services available over Secure Socket Layer
(SSL); this includes any web service whose URL starts with @samp{https://}.
@end quotation
@node Profiling
@section Profiling Your @command{awk} Programs
@cindex @command{awk} programs @subentry profiling
@cindex profiling @command{awk} programs
@cindex @code{awkprof.out} file
@cindex files @subentry @code{awkprof.out}
You may produce execution traces of your @command{awk} programs.
This is done by passing the option @option{--profile} to @command{gawk}.
When @command{gawk} has finished running, it creates a profile of your program in a file
named @file{awkprof.out}. Because it is profiling, it also executes up to 45% slower than
@command{gawk} normally does.
@cindex @option{--profile} option
As shown in the following example,
the @option{--profile} option can be used to change the name of the file
where @command{gawk} will write the profile:
@example
gawk --profile=myprog.prof -f myprog.awk data1 data2
@end example
@noindent
In the preceding example, @command{gawk} places the profile in
@file{myprog.prof} instead of in @file{awkprof.out}.
Here is a sample session showing a simple @command{awk} program,
its input data, and the results from running @command{gawk} with the
@option{--profile} option. First, the @command{awk} program:
@example
BEGIN @{ print "First BEGIN rule" @}
END @{ print "First END rule" @}
/foo/ @{
print "matched /foo/, gosh"
for (i = 1; i <= 3; i++)
sing()
@}
@{
if (/foo/)
print "if is true"
else
print "else is true"
@}
BEGIN @{ print "Second BEGIN rule" @}
END @{ print "Second END rule" @}
function sing( dummy)
@{
print "I gotta be me!"
@}
@end example
Following is the input data:
@example
foo
bar
baz
foo
junk
@end example
Here is the @file{awkprof.out} that results from running the
@command{gawk} profiler on this program and data (this example also
illustrates that @command{awk} programmers sometimes get up very early
in the morning to work):
@cindex @code{BEGIN} pattern @subentry profiling and
@cindex @code{END} pattern @subentry profiling and
@example
# gawk profile, created Mon Sep 29 05:16:21 2014
# BEGIN rule(s)
BEGIN @{
1 print "First BEGIN rule"
@}
BEGIN @{
1 print "Second BEGIN rule"
@}
# Rule(s)
5 /foo/ @{ # 2
2 print "matched /foo/, gosh"
6 for (i = 1; i <= 3; i++) @{
6 sing()
@}
@}
5 @{
5 if (/foo/) @{ # 2
2 print "if is true"
3 @} else @{
3 print "else is true"
@}
@}
# END rule(s)
END @{
1 print "First END rule"
@}
END @{
1 print "Second END rule"
@}
# Functions, listed alphabetically
6 function sing(dummy)
@{
6 print "I gotta be me!"
@}
@end example
This example illustrates many of the basic features of profiling output.
They are as follows:
@itemize @value{BULLET}
@item
The program is printed in the order @code{BEGIN} rules,
@code{BEGINFILE} rules,
pattern--action rules,
@code{ENDFILE} rules, @code{END} rules, and functions, listed
alphabetically.
Multiple @code{BEGIN} and @code{END} rules retain their
separate identities, as do
multiple @code{BEGINFILE} and @code{ENDFILE} rules.
@cindex patterns @subentry counts, in a profile
@item
Pattern--action rules have two counts.
The first count, to the left of the rule, shows how many times
the rule's pattern was @emph{tested}.
The second count, to the right of the rule's opening left brace
in a comment,
shows how many times the rule's action was @emph{executed}.
The difference between the two indicates how many times the rule's
pattern evaluated to false.
@item
Similarly,
the count for an @code{if}-@code{else} statement shows how many times
the condition was tested.
To the right of the opening left brace for the @code{if}'s body
is a count showing how many times the condition was true.
The count for the @code{else}
indicates how many times the test failed.
@cindex loops @subentry count for header, in a profile
@item
The count for a loop header (such as @code{for}
or @code{while}) shows how many times the loop test was executed.
(Because of this, you can't just look at the count on the first
statement in a rule to determine how many times the rule was executed.
If the first statement is a loop, the count is misleading.)
@cindex functions @subentry user-defined @subentry counts, in a profile
@cindex user-defined @subentry functions @subentry counts, in a profile
@item
For user-defined functions, the count next to the @code{function}
keyword indicates how many times the function was called.
The counts next to the statements in the body show how many times
those statements were executed.
@cindex @code{@{@}} (braces)
@cindex braces (@code{@{@}})
@item
The layout uses ``K&R'' style with TABs.
Braces are used everywhere, even when
the body of an @code{if}, @code{else}, or loop is only a single statement.
@cindex @code{()} (parentheses) @subentry in a profile
@cindex parentheses @code{()} @subentry in a profile
@item
Parentheses are used only where needed, as indicated by the structure
of the program and the precedence rules.
For example, @samp{(3 + 5) * 4} means add three and five, then multiply
the total by four. However, @samp{3 + 5 * 4} has no parentheses, and
means @samp{3 + (5 * 4)}.
However, explicit parentheses in the source program are retained.
@ignore
@item
All string concatenations are parenthesized too.
(This could be made a bit smarter.)
@end ignore
@item
Parentheses are used around the arguments to @code{print}
and @code{printf} only when
the @code{print} or @code{printf} statement is followed by a redirection.
Similarly, if
the target of a redirection isn't a scalar, it gets parenthesized.
@item
@command{gawk} supplies leading comments in
front of the @code{BEGIN} and @code{END} rules,
the @code{BEGINFILE} and @code{ENDFILE} rules,
the pattern--action rules, and the functions.
@end itemize
The profiled version of your program may not look exactly like what you
typed when you wrote it. This is because @command{gawk} creates the
profiled version by ``pretty-printing'' its internal representation of
the program. The advantage to this is that @command{gawk} can produce
a standard representation.
Also, things such as:
@example
/foo/
@end example
@noindent
come out as:
@example
/foo/ @{
print
@}
@end example
@noindent
which is correct, but possibly unexpected.
(If a program uses both @samp{print $0} and plain
@samp{print}, that distinction is retained.)
@cindex profiling @command{awk} programs @subentry dynamically
@cindex @command{gawk} @subentry dynamic profiling
@cindex @command{gawk} @subentry profiling programs
@cindex dynamic profiling
Besides creating profiles when a program has completed,
@command{gawk} can produce a profile while it is running.
This is useful if your @command{awk} program goes into an
infinite loop and you want to see what has been executed.
To use this feature, run @command{gawk} with the @option{--profile}
option in the background:
@example
$ @kbd{gawk --profile -f myprog &}
[1] 13992
@end example
@cindex @command{kill} command, dynamic profiling
@cindex @code{USR1} signal, for dynamic profiling
@cindex @code{SIGUSR1} signal, for dynamic profiling
@cindex signals @subentry @code{USR1}/@code{SIGUSR1}, for profiling
@noindent
The shell prints a job number and process ID number; in this case, 13992.
Use the @command{kill} command to send the @code{USR1} signal
to @command{gawk}:
@example
$ @kbd{kill -USR1 13992}
@end example
@noindent
As usual, the profiled version of the program is written to
@file{awkprof.out}, or to a different file if one was specified with
the @option{--profile} option.
Along with the regular profile, as shown earlier, the profile file
includes a trace of any active functions:
@example
# Function Call Stack:
# 3. baz
# 2. bar
# 1. foo
# -- main --
@end example
You may send @command{gawk} the @code{USR1} signal as many times as you like.
Each time, the profile and function call trace are appended to the output
profile file.
@cindex @code{HUP} signal, for dynamic profiling
@cindex @code{SIGHUP} signal, for dynamic profiling
@cindex signals @subentry @code{HUP}/@code{SIGHUP}, for profiling
If you use the @code{HUP} signal instead of the @code{USR1} signal,
@command{gawk} produces the profile and the function call trace and then exits.
@cindex @code{INT} signal (MS-Windows)
@cindex @code{SIGINT} signal (MS-Windows)
@cindex signals @subentry @code{INT}/@code{SIGINT} (MS-Windows)
@cindex @code{QUIT} signal (MS-Windows)
@cindex @code{SIGQUIT} signal (MS-Windows)
@cindex signals @subentry @code{QUIT}/@code{SIGQUIT} (MS-Windows)
When @command{gawk} runs on MS-Windows systems, it uses the
@code{INT} and @code{QUIT} signals for producing the profile, and in
the case of the @code{INT} signal, @command{gawk} exits. This is
because these systems don't support the @command{kill} command, so the
only signals you can deliver to a program are those generated by the
keyboard. The @code{INT} signal is generated by the
@kbd{Ctrl-c} or @kbd{Ctrl-BREAK} key, while the
@code{QUIT} signal is generated by the @kbd{Ctrl-\} key.
@cindex pretty printing
Finally, @command{gawk} also accepts another option, @option{--pretty-print}.
When called this way, @command{gawk} ``pretty-prints'' the program into
@file{awkprof.out}, without any execution counts.
@quotation NOTE
Once upon a time, the @option{--pretty-print} option would also run
your program. This is no longer the case.
@end quotation
@cindex profiling, pretty printing, difference with
@cindex pretty printing @subentry profiling, difference with
There is a significant difference between the output created when
profiling, and that created when pretty-printing. Pretty-printed output
preserves the original comments that were in the program, although their
placement may not correspond exactly to their original locations in the
source code. However, no comments should be lost.
Also, @command{gawk} does the best it can to preserve
the distinction between comments at the end of a statement and comments
on lines by themselves. This isn't always perfect, though.
However, as a deliberate design decision, profiling output @emph{omits}
the original program's comments. This allows you to focus on the
execution count data and helps you avoid the temptation to use the
profiler for pretty-printing.
Additionally, pretty-printed output does not have the leading indentation
that the profiling output does. This makes it easy to pretty-print your
code once development is completed, and then use the result as the final
version of your program.
Because the internal representation of your program is formatted to
recreate an @command{awk} program, profiling and pretty-printing
automatically disable @command{gawk}'s default optimizations.
Profiling and pretty-printing also preserve the original format of numeric
constants; if you used an octal or hexadecimal value in your source
code, it will appear that way in the output.
@node Advanced Features Summary
@section Summary
@itemize @value{BULLET}
@item
The @option{--non-decimal-data} option causes @command{gawk} to treat
octal- and hexadecimal-looking input data as octal and hexadecimal.
This option should be used with caution or not at all; use of @code{strtonum()}
is preferable.
Note that this option may disappear in a future version of @command{gawk}.
@item
You can take over complete control of sorting in @samp{for (@var{indx} in @var{array})}
array traversal by setting @code{PROCINFO["sorted_in"]} to the name of a user-defined
function that does the comparison of array elements based on index and value.
@item
Similarly, you can supply the name of a user-defined comparison function as the
third argument to either @code{asort()} or @command{asorti()} to control how
those functions sort arrays. Or you may provide one of the predefined control
strings that work for @code{PROCINFO["sorted_in"]}.
@item
You can use the @samp{|&} operator to create a two-way pipe to a coprocess.
You read from the coprocess with @code{getline} and write to it with @code{print}
or @code{printf}. Use @code{close()} to close off the coprocess completely, or
optionally, close off one side of the two-way communications.
@item
By using special @value{FN}s with the @samp{|&} operator, you can open a
TCP/IP (or UDP/IP) connection to remote hosts on the Internet. @command{gawk}
supports both IPv4 and IPv6.
@item
You can generate statement count profiles of your program. This can help you
determine which parts of your program may be taking the most time and let
you tune them more easily. Sending the @code{USR1} signal while profiling causes
@command{gawk} to dump the profile and keep going, including a function call stack.
@item
You can also just ``pretty-print'' the program.
@end itemize
@node Internationalization
@chapter Internationalization with @command{gawk}
Once upon a time, computer makers
wrote software that worked only in English.
Eventually, hardware and software vendors noticed that if their
systems worked in the native languages of non-English-speaking
countries, they were able to sell more systems.
As a result, internationalization and localization
of programs and software systems became a common practice.
@cindex internationalization @subentry localization
@cindex @command{gawk} @subentry internationalization @seeentry{internationalization}
@cindex internationalization @subentry localization @subentry @command{gawk} and
For many years, the ability to provide internationalization
was largely restricted to programs written in C and C++.
This @value{CHAPTER} describes the underlying library @command{gawk}
uses for internationalization, as well as how
@command{gawk} makes internationalization
features available at the @command{awk} program level.
Having internationalization available at the @command{awk} level
gives software developers additional flexibility---they are no
longer forced to write in C or C++ when internationalization is
a requirement.
@menu
* I18N and L10N:: Internationalization and Localization.
* Explaining gettext:: How GNU @command{gettext} works.
* Programmer i18n:: Features for the programmer.
* Translator i18n:: Features for the translator.
* I18N Example:: A simple i18n example.
* Gawk I18N:: @command{gawk} is also internationalized.
* I18N Summary:: Summary of I18N stuff.
@end menu
@node I18N and L10N
@section Internationalization and Localization
@cindex internationalization
@cindex localization @seeentry{internationalization, localization}
@cindex internationalization @subentry localization
@dfn{Internationalization} means writing (or modifying) a program once,
in such a way that it can use multiple languages without requiring
further source code changes.
@dfn{Localization} means providing the data necessary for an
internationalized program to work in a particular language.
Most typically, these terms refer to features such as the language
used for printing error messages, the language used to read
responses, and information related to how numerical and
monetary values are printed and read.
@node Explaining gettext
@section GNU @command{gettext}
@cindex internationalizing a program
@cindex @command{gettext} library
@command{gawk} uses GNU @command{gettext} to provide its internationalization
features.
The facilities in GNU @command{gettext} focus on messages: strings printed
by a program, either directly or via formatting with @code{printf} or
@code{sprintf()}.@footnote{For some operating systems, the @command{gawk}
port doesn't support GNU @command{gettext}.
Therefore, these features are not available
if you are using one of those operating systems. Sorry.}
@cindex portability @subentry @command{gettext} library and
When using GNU @command{gettext}, each application has its own
@dfn{text domain}. This is a unique name, such as @samp{kpilot} or @samp{gawk},
that identifies the application.
A complete application may have multiple components---programs written
in C or C++, as well as scripts written in @command{sh} or @command{awk}.
All of the components use the same text domain.
To make the discussion concrete, assume we're writing an application
named @command{guide}. Internationalization consists of the
following steps, in this order:
@enumerate
@item
The programmer reviews the source for all of @command{guide}'s components
and marks each string that is a candidate for translation.
For example, @code{"`-F': option required"} is a good candidate for translation.
A table with strings of option names is not (e.g., @command{gawk}'s
@option{--profile} option should remain the same, no matter what the local
language).
@cindex @code{textdomain()} function (C library)
@cindex C library functions @subentry @code{textdomain()}
@item
The programmer indicates the application's text domain
(@command{"guide"}) to the @command{gettext} library,
by calling the @code{textdomain()} function.
@cindex @code{.pot} files
@cindex files @subentry @code{.pot}
@cindex portable object @subentry template files
@cindex files @subentry portable object @subentry template file (@file{.pot})
@item
Messages from the application are extracted from the source code and
collected into a portable object template file (@file{guide.pot}),
which lists the strings and their translations.
The translations are initially empty.
The original (usually English) messages serve as the key for
lookup of the translations.
@cindex @code{.po} files
@cindex files @subentry @code{.po}
@cindex portable object @subentry files
@cindex files @subentry portable object
@item
For each language with a translator, @file{guide.pot}
is copied to a portable object file (@code{.po})
and translations are created and shipped with the application.
For example, there might be a @file{fr.po} for a French translation.
@cindex @code{.gmo} files
@cindex files @subentry @code{.gmo}
@cindex message object files
@cindex files @subentry message object
@item
Each language's @file{.po} file is converted into a binary
message object (@file{.gmo}) file.
A message object file contains the original messages and their
translations in a binary format that allows fast lookup of translations
at runtime.
@item
When @command{guide} is built and installed, the binary translation files
are installed in a standard place.
@cindex @code{bindtextdomain()} function (C library)
@cindex C library functions @subentry @code{bindtextdomain()}
@item
For testing and development, it is possible to tell @command{gettext}
to use @file{.gmo} files in a different directory than the standard
one by using the @code{bindtextdomain()} function.
@cindex @code{.gmo} files @subentry specifying directory of
@cindex files @subentry @code{.gmo} @subentry specifying directory of
@cindex message object files @subentry specifying directory of
@cindex files @subentry message object @subentry specifying directory of
@item
At runtime, @command{guide} looks up each string via a call
to @code{gettext()}. The returned string is the translated string
if available, or the original string if not.
@item
If necessary, it is possible to access messages from a different
text domain than the one belonging to the application, without
having to switch the application's default text domain back
and forth.
@end enumerate
@cindex @code{gettext()} function (C library)
@cindex C library functions @subentry @code{gettext()}
In C (or C++), the string marking and dynamic translation lookup
are accomplished by wrapping each string in a call to @code{gettext()}:
@example
printf("%s", gettext("Don't Panic!\n"));
@end example
The tools that extract messages from source code pull out all
strings enclosed in calls to @code{gettext()}.
@cindex @code{_} (underscore) @subentry C macro
@cindex underscore (@code{_}) @subentry C macro
The GNU @command{gettext} developers, recognizing that typing
@samp{gettext(@dots{})} over and over again is both painful and ugly to look
at, use the macro @samp{_} (an underscore) to make things easier:
@example
/* In the standard header file: */
#define _(str) gettext(str)
/* In the program text: */
printf("%s", _("Don't Panic!\n"));
@end example
@cindex internationalization @subentry localization @subentry locale categories
@cindex @command{gettext} library @subentry locale categories
@cindex locale categories
@noindent
This reduces the typing overhead to just three extra characters per string
and is considerably easier to read as well.
There are locale @dfn{categories}
for different types of locale-related information.
The defined locale categories that @command{gettext} knows about are:
@table @code
@cindex @code{LC_MESSAGES} locale category
@item LC_MESSAGES
Text messages. This is the default category for @command{gettext}
operations, but it is possible to supply a different one explicitly,
if necessary. (It is almost never necessary to supply a different category.)
@cindex sorting characters in different languages
@cindex @code{LC_COLLATE} locale category
@item LC_COLLATE
Text-collation information (i.e., how different characters
and/or groups of characters sort in a given language).
@cindex @code{LC_CTYPE} locale category
@item LC_CTYPE
Character-type information (alphabetic, digit, upper- or lowercase, and
so on) as well as character encoding.
@ignore
In June 2001 Bruno Haible wrote:
- Description of LC_CTYPE: It determines both
1. character encoding,
2. character type information.
(For example, in both KOI8-R and ISO-8859-5 the character type information
is the same - cyrillic letters could as 'alpha' - but the encoding is
different.)
@end ignore
This information is accessed via the
POSIX character classes in regular expressions,
such as @code{/[[:alnum:]]/}
(@pxref{Bracket Expressions}).
@cindex monetary information, localization
@cindex currency symbols, localization
@cindex internationalization @subentry localization @subentry monetary information
@cindex internationalization @subentry localization @subentry currency symbols
@cindex @code{LC_MONETARY} locale category
@item LC_MONETARY
Monetary information, such as the currency symbol, and whether the
symbol goes before or after a number.
@cindex @code{LC_NUMERIC} locale category
@item LC_NUMERIC
Numeric information, such as which characters to use for the decimal
point and the thousands separator.@footnote{Americans
use a comma every three decimal places and a period for the decimal
point, while many Europeans do exactly the opposite:
1,234.56 versus 1.234,56.}
@cindex time @subentry localization and
@cindex dates @subentry information related to, localization
@cindex @code{LC_TIME} locale category
@item LC_TIME
Time- and date-related information, such as 12- or 24-hour clock, month printed
before or after the day in a date, local month abbreviations, and so on.
@cindex @code{LC_ALL} locale category
@item LC_ALL
All of the above. (Not too useful in the context of @command{gettext}.)
@end table
@quotation NOTE
@cindex @env{LANGUAGE} environment variable
@cindex environment variables @subentry @env{LANGUAGE}
As described in @ref{Locales}, environment variables with the same
name as the locale categories (@env{LC_CTYPE}, @env{LC_ALL}, etc.)
influence @command{gawk}'s behavior (and that of other utilities).
Normally, these variables also affect how the @code{gettext} library
finds translations. However, the @env{LANGUAGE} environment variable
overrides the @env{LC_@var{xxx}} variables. Many GNU/Linux systems
may define this variable without your knowledge, causing @command{gawk}
to not find the correct translations. If this happens to you,
look to see if @env{LANGUAGE} is defined, and if so, use the shell's
@command{unset} command to remove it.
@end quotation
@cindex @env{GAWK_LOCALE_DIR} environment variable
@cindex environment variables @subentry @env{GAWK_LOCALE_DIR}
For testing translations of @command{gawk} itself, you can set
the @env{GAWK_LOCALE_DIR} environment variable. See the documentation
for the C @code{bindtextdomain()} function and also see
@ref{Other Environment Variables}.
@node Programmer i18n
@section Internationalizing @command{awk} Programs
@cindex @command{awk} programs @subentry internationalizing
@command{gawk} provides the following variables for
internationalization:
@table @code
@cindex @code{TEXTDOMAIN} variable
@item TEXTDOMAIN
This variable indicates the application's text domain.
For compatibility with GNU @command{gettext}, the default
value is @code{"messages"}.
@cindex internationalization @subentry localization @subentry marked strings
@cindex strings @subentry for localization
@item _"your message here"
String constants marked with a leading underscore
are candidates for translation at runtime.
String constants without a leading underscore are not translated.
@end table
@command{gawk} provides the following functions for
internationalization:
@table @code
@cindexgawkfunc{dcgettext}
@item @code{dcgettext(@var{string}} [@code{,} @var{domain} [@code{,} @var{category}]]@code{)}
Return the translation of @var{string} in
text domain @var{domain} for locale category @var{category}.
The default value for @var{domain} is the current value of @code{TEXTDOMAIN}.
The default value for @var{category} is @code{"LC_MESSAGES"}.
If you supply a value for @var{category}, it must be a string equal to
one of the known locale categories described in
@ifnotinfo
the previous @value{SECTION}.
@end ifnotinfo
@ifinfo
@ref{Explaining gettext}.
@end ifinfo
You must also supply a text domain. Use @code{TEXTDOMAIN} if
you want to use the current domain.
@quotation CAUTION
The order of arguments to the @command{awk} version
of the @code{dcgettext()} function is purposely different from the order for
the C version. The @command{awk} version's order was
chosen to be simple and to allow for reasonable @command{awk}-style
default arguments.
@end quotation
@cindexgawkfunc{dcngettext}
@item @code{dcngettext(@var{string1}, @var{string2}, @var{number}} [@code{,} @var{domain} [@code{,} @var{category}]]@code{)}
Return the plural form used for @var{number} of the
translation of @var{string1} and @var{string2} in text domain
@var{domain} for locale category @var{category}. @var{string1} is the
English singular variant of a message, and @var{string2} is the English plural
variant of the same message.
The default value for @var{domain} is the current value of @code{TEXTDOMAIN}.
The default value for @var{category} is @code{"LC_MESSAGES"}.
The same remarks about argument order as for the @code{dcgettext()} function apply.
@cindex @code{.gmo} files @subentry specifying directory of
@cindex files @subentry @code{.gmo} @subentry specifying directory of
@cindex message object files @subentry specifying directory of
@cindex files @subentry message object @subentry specifying directory of
@cindexgawkfunc{bindtextdomain}
@item @code{bindtextdomain(@var{directory}} [@code{,} @var{domain} ]@code{)}
Change the directory in which
@command{gettext} looks for @file{.gmo} files, in case they
will not or cannot be placed in the standard locations
(e.g., during testing).
Return the directory in which @var{domain} is ``bound.''
The default @var{domain} is the value of @code{TEXTDOMAIN}.
If @var{directory} is the null string (@code{""}), then
@code{bindtextdomain()} returns the current binding for the
given @var{domain}.
@end table
To use these facilities in your @command{awk} program, follow these steps:
@enumerate
@cindex @code{BEGIN} pattern @subentry @code{TEXTDOMAIN} variable and
@cindex @code{TEXTDOMAIN} variable @subentry @code{BEGIN} pattern and
@item
Set the variable @code{TEXTDOMAIN} to the text domain of
your program. This is best done in a @code{BEGIN} rule
(@pxref{BEGIN/END}),
or it can also be done via the @option{-v} command-line
option (@pxref{Options}):
@example
BEGIN @{
TEXTDOMAIN = "guide"
@dots{}
@}
@end example
@cindex @code{_} (underscore) @subentry translatable strings
@cindex underscore (@code{_}) @subentry translatable strings
@item
Mark all translatable strings with a leading underscore (@samp{_})
character. It @emph{must} be adjacent to the opening
quote of the string. For example:
@example
print _"hello, world"
x = _"you goofed"
printf(_"Number of users is %d\n", nusers)
@end example
@item
If you are creating strings dynamically, you can
still translate them, using the @code{dcgettext()}
built-in function:@footnote{Thanks to Bruno Haible for this
example.}
@example
if (groggy)
message = dcgettext("%d customers disturbing me\n", "adminprog")
else
message = dcgettext("enjoying %d customers\n", "adminprog")
printf(message, ncustomers)
@end example
Here, the call to @code{dcgettext()} supplies a different
text domain (@code{"adminprog"}) in which to find the
message, but it uses the default @code{"LC_MESSAGES"} category.
The previous example only works if @code{ncustomers} is greater than one.
This example would be better done with @code{dcngettext()}:
@example
if (groggy)
message = dcngettext("%d customer disturbing me\n",
"%d customers disturbing me\n",
ncustomers, "adminprog")
else
message = dcngettext("enjoying %d customer\n",
"enjoying %d customers\n",
ncustomers, "adminprog")
printf(message, ncustomers)
@end example
@cindex @code{LC_MESSAGES} locale category @subentry @code{bindtextdomain()} function (@command{gawk})
@item
During development, you might want to put the @file{.gmo}
file in a private directory for testing. This is done
with the @code{bindtextdomain()} built-in function:
@example
BEGIN @{
TEXTDOMAIN = "guide" # our text domain
if (Testing) @{
# where to find our files
bindtextdomain("testdir")
# joe is in charge of adminprog
bindtextdomain("../joe/testdir", "adminprog")
@}
@dots{}
@}
@end example
@end enumerate
@xref{I18N Example}
for an example program showing the steps to create
and use translations from @command{awk}.
@node Translator i18n
@section Translating @command{awk} Programs
@cindex @code{.po} files
@cindex files @subentry @code{.po}
@cindex portable object @subentry files
@cindex files @subentry portable object
Once a program's translatable strings have been marked, they must
be extracted to create the initial @file{.pot} file.
As part of translation, it is often helpful to rearrange the order
in which arguments to @code{printf} are output.
@command{gawk}'s @option{--gen-pot} command-line option extracts
the messages and is discussed next.
After that, @code{printf}'s ability to
rearrange the order for @code{printf} arguments at runtime
is covered.
@menu
* String Extraction:: Extracting marked strings.
* Printf Ordering:: Rearranging @code{printf} arguments.
* I18N Portability:: @command{awk}-level portability issues.
@end menu
@node String Extraction
@subsection Extracting Marked Strings
@cindex strings @subentry extracting
@cindex @option{--gen-pot} option
@cindex command line @subentry options @subentry string extraction
@cindex string @subentry extraction (internationalization)
@cindex marked string extraction (internationalization)
@cindex extraction, of marked strings (internationalization)
@cindex @option{--gen-pot} option
Once your @command{awk} program is working, and all the strings have
been marked and you've set (and perhaps bound) the text domain,
it is time to produce translations.
First, use the @option{--gen-pot} command-line option to create
the initial @file{.pot} file:
@example
gawk --gen-pot -f guide.awk > guide.pot
@end example
@cindex @code{xgettext} utility
When run with @option{--gen-pot}, @command{gawk} does not execute your
program. Instead, it parses it as usual and prints all marked strings
to standard output in the format of a GNU @command{gettext} Portable Object
file. Also included in the output are any constant strings that
appear as the first argument to @code{dcgettext()} or as the first and
second argument to @code{dcngettext()}.@footnote{The
@command{xgettext} utility that comes with GNU
@command{gettext} can handle @file{.awk} files.}
You should distribute the generated @file{.pot} file with
your @command{awk} program; translators will eventually use it
to provide you translations that you can also then distribute.
@xref{I18N Example}
for the full list of steps to go through to create and test
translations for @command{guide}.
@node Printf Ordering
@subsection Rearranging @code{printf} Arguments
@cindex @code{printf} statement @subentry positional specifiers
@cindex positional specifiers, @code{printf} statement
Format strings for @code{printf} and @code{sprintf()}
(@pxref{Printf})
present a special problem for translation.
Consider the following:@footnote{This example is borrowed
from the GNU @command{gettext} manual.}
@example
printf(_"String `%s' has %d characters\n",
string, length(string)))
@end example
A possible German translation for this might be:
@example
"%d Zeichen lang ist die Zeichenkette `%s'\n"
@end example
The problem should be obvious: the order of the format
specifications is different from the original!
Even though @code{gettext()} can return the translated string
at runtime,
it cannot change the argument order in the call to @code{printf}.
To solve this problem, @code{printf} format specifiers may have
an additional optional element, which we call a @dfn{positional specifier}.
For example:
@example
"%2$d Zeichen lang ist die Zeichenkette `%1$s'\n"
@end example
Here, the positional specifier consists of an integer count, which indicates which
argument to use, and a @samp{$}. Counts are one-based, and the
format string itself is @emph{not} included. Thus, in the following
example, @samp{string} is the first argument and @samp{length(string)} is the second:
@example
$ @kbd{gawk 'BEGIN @{}
> @kbd{string = "Don\47t Panic"}
> @kbd{printf "%2$d characters live in \"%1$s\"\n",}
> @kbd{string, length(string)}
> @kbd{@}'}
@print{} 11 characters live in "Don't Panic"
@end example
If present, positional specifiers come first in the format specification,
before the flags, the field width, and/or the precision.
Positional specifiers can be used with the dynamic field width and
precision capability:
@example
$ @kbd{gawk 'BEGIN @{}
> @kbd{printf("%*.*s\n", 10, 20, "hello")}
> @kbd{printf("%3$*2$.*1$s\n", 20, 10, "hello")}
> @kbd{@}'}
@print{} hello
@print{} hello
@end example
@quotation NOTE
When using @samp{*} with a positional specifier, the @samp{*}
comes first, then the integer position, and then the @samp{$}.
This is somewhat counterintuitive.
@end quotation
@cindex @code{printf} statement @subentry positional specifiers @subentry mixing with regular formats
@cindex positional specifiers, @code{printf} statement @subentry mixing with regular formats
@cindex format specifiers @subentry mixing regular with positional specifiers
@command{gawk} does not allow you to mix regular format specifiers
and those with positional specifiers in the same string:
@example
@group
$ @kbd{gawk 'BEGIN @{ printf "%d %3$s\n", 1, 2, "hi" @}'}
@error{} gawk: cmd. line:1: fatal: must use `count$' on all formats or none
@end group
@end example
@quotation NOTE
There are some pathological cases that @command{gawk} may fail to
diagnose. In such cases, the output may not be what you expect.
It's still a bad idea to try mixing them, even if @command{gawk}
doesn't detect it.
@end quotation
Although positional specifiers can be used directly in @command{awk} programs,
their primary purpose is to help in producing correct translations of
format strings into languages different from the one in which the program
is first written.
@node I18N Portability
@subsection @command{awk} Portability Issues
@cindex portability @subentry internationalization and
@cindex internationalization @subentry localization @subentry portability and
@command{gawk}'s internationalization features were purposely chosen to
have as little impact as possible on the portability of @command{awk}
programs that use them to other versions of @command{awk}.
Consider this program:
@example
BEGIN @{
TEXTDOMAIN = "guide"
if (Test_Guide) # set with -v
bindtextdomain("/test/guide/messages")
print _"don't panic!"
@}
@end example
@noindent
As written, it won't work on other versions of @command{awk}.
However, it is actually almost portable, requiring very little
change:
@itemize @value{BULLET}
@cindex @code{TEXTDOMAIN} variable @subentry portability and
@item
Assignments to @code{TEXTDOMAIN} won't have any effect,
because @code{TEXTDOMAIN} is not special in other @command{awk} implementations.
@item
Non-GNU versions of @command{awk} treat marked strings
as the concatenation of a variable named @code{_} with the string
following it.@footnote{This is good fodder for an ``Obfuscated
@command{awk}'' contest.} Typically, the variable @code{_} has
the null string (@code{""}) as its value, leaving the original string constant as
the result.
@item
By defining ``dummy'' functions to replace @code{dcgettext()}, @code{dcngettext()},
and @code{bindtextdomain()}, the @command{awk} program can be made to run, but
all the messages are output in the original language.
For example:
@cindex @code{bindtextdomain()} function (@command{gawk}) @subentry portability and
@cindex @code{dcgettext()} function (@command{gawk}) @subentry portability and
@cindex @code{dcngettext()} function (@command{gawk}) @subentry portability and
@example
@c file eg/lib/libintl.awk
function bindtextdomain(dir, domain)
@{
return dir
@}
function dcgettext(string, domain, category)
@{
return string
@}
function dcngettext(string1, string2, number, domain, category)
@{
return (number == 1 ? string1 : string2)
@}
@c endfile
@end example
@item
The use of positional specifications in @code{printf} or
@code{sprintf()} is @emph{not} portable.
To support @code{gettext()} at the C level, many systems' C versions of
@code{sprintf()} do support positional specifiers. But it works only if
enough arguments are supplied in the function call. Many versions of
@command{awk} pass @code{printf} formats and arguments unchanged to the
underlying C library version of @code{sprintf()}, but only one format and
argument at a time. What happens if a positional specification is
used is anybody's guess.
However, because the positional specifications are primarily for use in
@emph{translated} format strings, and because non-GNU @command{awk}s never
retrieve the translated string, this should not be a problem in practice.
@end itemize
@node I18N Example
@section A Simple Internationalization Example
Now let's look at a step-by-step example of how to internationalize and
localize a simple @command{awk} program, using @file{guide.awk} as our
original source:
@example
@c file eg/prog/guide.awk
BEGIN @{
TEXTDOMAIN = "guide"
bindtextdomain(".") # for testing
print _"Don't Panic"
print _"The Answer Is", 42
print "Pardon me, Zaphod who?"
@}
@c endfile
@end example
@noindent
Run @samp{gawk --gen-pot} to create the @file{.pot} file:
@example
$ @kbd{gawk --gen-pot -f guide.awk > guide.pot}
@end example
@noindent
This produces:
@example
@c file eg/data/guide.po
#: guide.awk:4
msgid "Don't Panic"
msgstr ""
#: guide.awk:5
msgid "The Answer Is"
msgstr ""
@c endfile
@end example
This original portable object template file is saved and reused for each language
into which the application is translated. The @code{msgid}
is the original string and the @code{msgstr} is the translation.
@quotation NOTE
Strings not marked with a leading underscore do not
appear in the @file{guide.pot} file.
@end quotation
Next, the messages must be translated.
Here is a translation to a hypothetical dialect of English,
called ``Mellow'':@footnote{Perhaps it would be better if it were
called ``Hippy.'' Ah, well.}
@example
@group
$ @kbd{cp guide.pot guide-mellow.po}
@var{Add translations to} guide-mellow.po @dots{}
@end group
@end example
@noindent
Following are the translations:
@example
@c file eg/data/guide-mellow.po
#: guide.awk:4
msgid "Don't Panic"
msgstr "Hey man, relax!"
#: guide.awk:5
msgid "The Answer Is"
msgstr "Like, the scoop is"
@c endfile
@end example
@cindex GNU/Linux
@quotation NOTE
The following instructions apply to GNU/Linux with the GNU C Library. Be
aware that the actual steps may change over time, that the following
description may not be accurate for all GNU/Linux distributions, and
that things may work entirely differently on other operating systems.
@end quotation
The next step is to make the directory to hold the binary message object
file and then to create the @file{guide.mo} file.
The directory has the form @file{@var{locale}/LC_MESSAGES}, where
@var{locale} is a locale name known to the C @command{gettext} routines.
@cindex @env{LANGUAGE} environment variable
@cindex environment variables @subentry @env{LANGUAGE}
@cindex @env{LC_ALL} environment variable
@cindex environment variables @subentry @env{LC_ALL}
@cindex @env{LANG} environment variable
@cindex environment variables @subentry @env{LANG}
@cindex @env{LC_MESSAGES} environment variable
@cindex environment variables @subentry @env{LC_MESSAGES}
How do we know which locale to use? It turns out that there are
four different environment variables used by the C @command{gettext} routines.
In order, they are @env{$LANGUAGE}, @env{$LC_ALL}, @env{$LANG}, and
@env{$LC_MESSAGES}.@footnote{Well, sort of. It seems that if @env{$LC_ALL}
is set to @samp{C}, then no translations are done. Go figure.}
Thus, we check the value of @env{$LANGUAGE}:
@example
$ @kbd{echo $LANGUAGE}
@print{} en_US.UTF-8
@end example
@noindent
We next make the directories:
@example
$ @kbd{mkdir en_US.UTF-8 en_US.UTF-8/LC_MESSAGES}
@end example
@cindex @code{.po} files @subentry converting to @code{.mo}
@cindex files @subentry @code{.po} @subentry converting to @code{.mo}
@cindex @code{.mo} files, converting from @code{.po}
@cindex files @subentry @code{.mo}, converting from @code{.po}
@cindex portable object @subentry files @subentry converting to message object files
@cindex files @subentry portable object @subentry converting to message object files
@cindex message object files @subentry converting from portable object files
@cindex files @subentry message object @subentry converting from portable object files
@cindex @command{msgfmt} utility
The @command{msgfmt} utility converts the human-readable
@file{.po} file into a machine-readable @file{.mo} file.
By default, @command{msgfmt} creates a file named @file{messages}.
This file must be renamed and placed in the proper directory (using
the @option{-o} option) so that @command{gawk} can find it:
@example
$ @kbd{msgfmt guide-mellow.po -o en_US.UTF-8/LC_MESSAGES/guide.mo}
@end example
Finally, we run the program to test it:
@example
$ @kbd{gawk -f guide.awk}
@print{} Hey man, relax!
@print{} Like, the scoop is 42
@print{} Pardon me, Zaphod who?
@end example
If the three replacement functions for @code{dcgettext()}, @code{dcngettext()},
and @code{bindtextdomain()}
(@pxref{I18N Portability})
are in a file named @file{libintl.awk},
then we can run @file{guide.awk} unchanged as follows:
@example
$ @kbd{gawk --posix -f guide.awk -f libintl.awk}
@print{} Don't Panic
@print{} The Answer Is 42
@print{} Pardon me, Zaphod who?
@end example
@node Gawk I18N
@section @command{gawk} Can Speak Your Language
@command{gawk} itself has been internationalized
using the GNU @command{gettext} package.
(GNU @command{gettext} is described in
complete detail in
@ifinfo
@inforef{Top, , GNU @command{gettext} utilities, gettext, GNU @command{gettext} utilities}.)
@end ifinfo
@ifnotinfo
@uref{https://www.gnu.org/software/gettext/manual/,
@cite{GNU @command{gettext} utilities}}.)
@end ifnotinfo
As of this writing, the latest version of GNU @command{gettext} is
@uref{ftp://ftp.gnu.org/gnu/gettext/gettext-0.19.8.1.tar.gz,
@value{PVERSION} 0.19.8.1}.
If a translation of @command{gawk}'s messages exists,
then @command{gawk} produces usage messages, warnings,
and fatal errors in the local language.
@node I18N Summary
@section Summary
@itemize @value{BULLET}
@item
Internationalization means writing a program such that it can use multiple
languages without requiring source code changes. Localization means
providing the data necessary for an internationalized program to work
in a particular language.
@item
@command{gawk} uses GNU @command{gettext} to let you internationalize
and localize @command{awk} programs. A program's text domain identifies
the program for grouping all messages and other data together.
@item
You mark a program's strings for translation by preceding them with
an underscore. Once that is done, the strings are extracted into a
@file{.pot} file. This file is copied for each language into a @file{.po}
file, and the @file{.po} files are compiled into @file{.gmo} files for
use at runtime.
@item
You can use positional specifications with @code{sprintf()} and
@code{printf} to rearrange the placement of argument values in formatted
strings and output. This is useful for the translation of format
control strings.
@item
The internationalization features have been designed so that they
can be easily worked around in a standard @command{awk}.
@item
@command{gawk} itself has been internationalized and ships with
a number of translations for its messages.
@end itemize
@node Debugger
@chapter Debugging @command{awk} Programs
@cindex debugging @subentry @command{awk} programs
@c The original text for this chapter was contributed by Efraim Yawitz.
It would be nice if computer programs worked perfectly the first time they
were run, but in real life, this rarely happens for programs of
any complexity. Thus, most programming languages have facilities available
for ``debugging'' programs, and @command{awk} is no exception.
The @command{gawk} debugger is purposely modeled after
@uref{https://www.gnu.org/software/gdb/, the GNU Debugger (GDB)}
command-line debugger. If you are familiar with GDB, learning
how to use @command{gawk} for debugging your programs is easy.
@menu
* Debugging:: Introduction to @command{gawk} debugger.
* Sample Debugging Session:: Sample debugging session.
* List of Debugger Commands:: Main debugger commands.
* Readline Support:: Readline support.
* Limitations:: Limitations and future plans.
* Debugging Summary:: Debugging summary.
@end menu
@node Debugging
@section Introduction to the @command{gawk} Debugger
This @value{SECTION} introduces debugging in general and begins
the discussion of debugging in @command{gawk}.
@menu
* Debugging Concepts:: Debugging in General.
* Debugging Terms:: Additional Debugging Concepts.
* Awk Debugging:: Awk Debugging.
@end menu
@node Debugging Concepts
@subsection Debugging in General
(If you have used debuggers in other languages, you may want to skip
ahead to @ref{Awk Debugging}.)
Of course, a debugging program cannot remove bugs for you, because it has
no way of knowing what you or your users consider a ``bug'' versus a
``feature.'' (Sometimes, we humans have a hard time with this ourselves.)
In that case, what can you expect from such a tool? The answer to that
depends on the language being debugged, but in general, you can expect at
least the following:
@cindex debugger @subentry capabilities
@itemize @value{BULLET}
@item
The ability to watch a program execute its instructions one by one,
giving you, the programmer, the opportunity to think about what is happening
on a time scale of seconds, minutes, or hours, rather than the nanosecond
time scale at which the code usually runs.
@item
The opportunity to not only passively observe the operation of your
program, but to control it and try different paths of execution, without
having to change your source files.
@item
The chance to see the values of data in the program at any point in
execution, and also to change that data on the fly, to see how that
affects what happens afterward. (This often includes the ability
to look at internal data structures besides the variables you actually
defined in your code.)
@item
The ability to obtain additional information about your program's state
or even its internal structure.
@end itemize
All of these tools provide a great amount of help in using your own
skills and understanding of the goals of your program to find where it
is going wrong (or, for that matter, to better comprehend a perfectly
functional program that you or someone else wrote).
@node Debugging Terms
@subsection Debugging Concepts
@cindex debugger @subentry concepts
Before diving in to the details, we need to introduce several
important concepts that apply to just about all debuggers.
The following list defines terms used throughout the rest of
this @value{CHAPTER}:
@table @dfn
@cindex call stack @subentry explanation of
@cindex stack frame (debugger)
@item Stack frame
Programs generally call functions during the course of their execution.
One function can call another, or a function can call itself (recursion).
You can view the chain of called functions (main program calls A, which
calls B, which calls C), as a stack of executing functions: the currently
running function is the topmost one on the stack, and when it finishes
(returns), the next one down then becomes the active function.
Such a stack is termed a @dfn{call stack}.
For each function on the call stack, the system maintains a data area
that contains the function's parameters, local variables, and return value,
as well as any other ``bookkeeping'' information needed to manage the
call stack. This data area is termed a @dfn{stack frame}.
@command{gawk} also follows this model, and gives you
access to the call stack and to each stack frame. You can see the
call stack, as well as from where each function on the stack was
invoked. Commands that print the call stack print information about
each stack frame (as detailed later on).
@item Breakpoint
@cindex breakpoint
During debugging, you often wish to let the program run until it
reaches a certain point, and then continue execution from there one
statement (or instruction) at a time. The way to do this is to set
a @dfn{breakpoint} within the program. A breakpoint is where the
execution of the program should break off (stop), so that you can
take over control of the program's execution. You can add and remove
as many breakpoints as you like.
@item Watchpoint
@cindex watchpoint (debugger)
A watchpoint is similar to a breakpoint. The difference is that
breakpoints are oriented around the code: stop when a certain point in the
code is reached. A watchpoint, however, specifies that program execution
should stop when a @emph{data value} is changed. This is useful, as
sometimes it happens that a variable receives an erroneous value, and it's
hard to track down where this happens just by looking at the code.
By using a watchpoint, you can stop whenever a variable is assigned to,
and usually find the errant code quite quickly.
@end table
@node Awk Debugging
@subsection @command{awk} Debugging
Debugging an @command{awk} program has some specific aspects that are
not shared with programs written in other languages.
First of all, the fact that @command{awk} programs usually take input
line by line from a file or files and operate on those lines using specific
rules makes it especially useful to organize viewing the execution of
the program in terms of these rules. As we will see, each @command{awk}
rule is treated almost like a function call, with its own specific block
of instructions.
In addition, because @command{awk} is by design a very concise language,
it is easy to lose sight of everything that is going on ``inside''
each line of @command{awk} code. The debugger provides the opportunity
to look at the individual primitive instructions carried out
by the higher-level @command{awk} commands.@footnote{The ``primitive
instructions'' are defined by @command{gawk} itself; the debugger
does not work at the level of machine instructions.}
@node Sample Debugging Session
@section Sample @command{gawk} Debugging Session
@cindex sample debugging session
@cindex example debugging session
@cindex debugging @subentry example session
In order to illustrate the use of @command{gawk} as a debugger, let's look at a sample
debugging session. We will use the @command{awk} implementation of the
POSIX @command{uniq} command presented earlier (@pxref{Uniq Program})
as our example.
@menu
* Debugger Invocation:: How to Start the Debugger.
* Finding The Bug:: Finding the Bug.
@end menu
@node Debugger Invocation
@subsection How to Start the Debugger
@cindex starting the debugger
@cindex debugger @subentry how to start
Starting the debugger is almost exactly like running @command{gawk} normally,
except you have to pass an additional option, @option{--debug}, or the
corresponding short option, @option{-D}. The file(s) containing the
program and any supporting code are given on the command line as arguments
to one or more @option{-f} options. (@command{gawk} is not designed
to debug command-line programs, only programs contained in files.)
In our case, we invoke the debugger like this:
@example
$ @kbd{gawk -D -f getopt.awk -f join.awk -f uniq.awk -1 inputfile}
@end example
@noindent
where both @file{getopt.awk} and @file{uniq.awk} are in @env{$AWKPATH}.
(Experienced users of GDB or similar debuggers should note that
this syntax is slightly different from what you are used to.
With the @command{gawk} debugger, you give the arguments for running the program
in the command line to the debugger rather than as part of the @code{run}
command at the debugger prompt.)
The @option{-1} is an option to @file{uniq.awk}.
@cindex debugger @subentry prompt
Instead of immediately running the program on @file{inputfile}, as
@command{gawk} would ordinarily do, the debugger merely loads all
the program source files, compiles them internally, and then gives
us a prompt:
@example
gawk>
@end example
@noindent
from which we can issue commands to the debugger. At this point, no
code has been executed.
@node Finding The Bug
@subsection Finding the Bug
Let's say that we are having a problem using (a faulty version of)
@file{uniq.awk} in ``field-skipping'' mode, and it doesn't seem to be
catching lines which should be identical when skipping the first field,
such as:
@example
awk is a wonderful program!
gawk is a wonderful program!
@end example
This could happen if we were thinking (C-like) of the fields in a record
as being numbered in a zero-based fashion, so instead of the lines:
@example
clast = join(alast, fcount+1, n)
cline = join(aline, fcount+1, m)
@end example
@noindent
we wrote:
@example
clast = join(alast, fcount, n)
cline = join(aline, fcount, m)
@end example
The first thing we usually want to do when trying to investigate a
problem like this is to put a breakpoint in the program so that we can
watch it at work and catch what it is doing wrong. A reasonable spot for
a breakpoint in @file{uniq.awk} is at the beginning of the function
@code{are_equal()}, which compares the current line with the previous one. To set
the breakpoint, use the @code{b} (breakpoint) command:
@cindex debugger @subentry setting a breakpoint
@cindex debugger @subentry commands @subentry @code{breakpoint}
@cindex debugger @subentry commands @subentry @code{break}
@cindex debugger @subentry commands @subentry @code{b} (@code{break})
@example
gawk> @kbd{b are_equal}
@print{} Breakpoint 1 set at file `awklib/eg/prog/uniq.awk', line 63
@end example
The debugger tells us the file and line number where the breakpoint is.
Now type @samp{r} or @samp{run} and the program runs until it hits
the breakpoint for the first time:
@cindex debugger @subentry running the program
@cindex debugger @subentry commands @subentry @code{run}
@example
gawk> @kbd{r}
@print{} Starting program:
@print{} Stopping in Rule ...
@print{} Breakpoint 1, are_equal(n, m, clast, cline, alast, aline)
at `awklib/eg/prog/uniq.awk':63
@print{} 63 if (fcount == 0 && charcount == 0)
gawk>
@end example
Now we can look at what's going on inside our program. First of all,
let's see how we got to where we are. At the prompt, we type @samp{bt}
(short for ``backtrace''), and the debugger responds with a
listing of the current stack frames:
@cindex debugger @subentry stack frames, showing
@cindex debugger @subentry commands @subentry @code{bt} (@code{backtrace})
@cindex debugger @subentry commands @subentry @code{backtrace}
@example
gawk> @kbd{bt}
@print{} #0 are_equal(n, m, clast, cline, alast, aline)
at `awklib/eg/prog/uniq.awk':68
@print{} #1 in main() at `awklib/eg/prog/uniq.awk':88
@end example
This tells us that @code{are_equal()} was called by the main program at
line 88 of @file{uniq.awk}. (This is not a big surprise, because this
is the only call to @code{are_equal()} in the program, but in more complex
programs, knowing who called a function and with what parameters can be
the key to finding the source of the problem.)
Now that we're in @code{are_equal()}, we can start looking at the values
of some variables. Let's say we type @samp{p n}
(@code{p} is short for ``print''). We would expect to see the value of
@code{n}, a parameter to @code{are_equal()}. Actually, the debugger
gives us:
@cindex debugger @subentry commands @subentry @code{print}
@cindex debugger @subentry commands @subentry @code{p} (@code{print})
@example
gawk> @kbd{p n}
@print{} n = untyped variable
@end example
@noindent
In this case, @code{n} is an uninitialized local variable, because the
function was called without arguments (@pxref{Function Calls}).
A more useful variable to display might be the current record:
@example
gawk> @kbd{p $0}
@print{} $0 = "gawk is a wonderful program!"
@end example
@noindent
This might be a bit puzzling at first, as this is the second line of
our test input. Let's look at @code{NR}:
@example
gawk> @kbd{p NR}
@print{} NR = 2
@end example
@noindent
So we can see that @code{are_equal()} was only called for the second record
of the file. Of course, this is because our program contains a rule for
@samp{NR == 1}:
@example
NR == 1 @{
last = $0
next
@}
@end example
OK, let's just check that that rule worked correctly:
@example
gawk> @kbd{p last}
@print{} last = "awk is a wonderful program!"
@end example
Everything we have done so far has verified that the program has worked as
planned, up to and including the call to @code{are_equal()}, so the problem must
be inside this function. To investigate further, we must begin
``stepping through'' the lines of @code{are_equal()}. We start by typing
@samp{n} (for ``next''):
@cindex debugger @subentry commands @subentry @code{n} (@code{next})
@cindex debugger @subentry commands @subentry @code{next}
@example
@group
gawk> @kbd{n}
@print{} 66 if (fcount > 0) @{
@end group
@end example
This tells us that @command{gawk} is now ready to execute line 66, which
decides whether to give the lines the special ``field-skipping'' treatment
indicated by the @option{-1} command-line option. (Notice that we skipped
from where we were before, at line 63, to here, because the condition
in line 63, @samp{if (fcount == 0 && charcount == 0)}, was false.)
Continuing to step, we now get to the splitting of the current and
last records:
@example
gawk> @kbd{n}
@print{} 67 n = split(last, alast)
gawk> @kbd{n}
@print{} 68 m = split($0, aline)
@end example
At this point, we should be curious to see what our records were split
into, so we try to look:
@example
gawk> @kbd{p n m alast aline}
@print{} n = 5
@print{} m = untyped variable
@print{} alast = array, 5 elements
@print{} aline = untyped variable
@end example
@noindent
(The @code{p} command can take more than one argument, similar to
@command{awk}'s @code{print} statement.)
This is kind of disappointing, though. All we found out is that there
are five elements in @code{alast}; @code{m} and @code{aline} don't have
values because we are at line 68 but haven't executed it yet.
This information is useful enough (we now know that
none of the words were accidentally left out), but what if we want to see
inside the array?
@cindex debugger @subentry printing single array elements
The first choice would be to use subscripts:
@example
gawk> @kbd{p alast[0]}
@print{} "0" not in array `alast'
@end example
@noindent
Oops!
@example
gawk> @kbd{p alast[1]}
@print{} alast["1"] = "awk"
@end example
This would be kind of slow for a 100-member array, though, so
@command{gawk} provides a shortcut (reminiscent of another language
not to be mentioned):
@cindex debugger @subentry printing all array elements
@example
gawk> @kbd{p @@alast}
@print{} alast["1"] = "awk"
@print{} alast["2"] = "is"
@print{} alast["3"] = "a"
@print{} alast["4"] = "wonderful"
@print{} alast["5"] = "program!"
@end example
It looks like we got this far OK. Let's take another step
or two:
@example
gawk> @kbd{n}
@print{} 69 clast = join(alast, fcount, n)
gawk> @kbd{n}
@print{} 70 cline = join(aline, fcount, m)
@end example
Well, here we are at our error (sorry to spoil the suspense). What we
had in mind was to join the fields starting from the second one to make
the virtual record to compare, and if the first field were numbered zero,
this would work. Let's look at what we've got:
@example
gawk> @kbd{p cline clast}
@print{} cline = "gawk is a wonderful program!"
@print{} clast = "awk is a wonderful program!"
@end example
Hey, those look pretty familiar! They're just our original, unaltered
input records. A little thinking (the human brain is still the best
debugging tool), and we realize that we were off by one!
We get out of the debugger:
@example
gawk> @kbd{q}
@print{} The program is running. Exit anyway (y/n)? @kbd{y}
@end example
@noindent
Then we get into an editor:
@example
clast = join(alast, fcount+1, n)
cline = join(aline, fcount+1, m)
@end example
@noindent
and problem solved!
@node List of Debugger Commands
@section Main Debugger Commands
The @command{gawk} debugger command set can be divided into the
following categories:
@itemize @value{BULLET}
@item
Breakpoint control
@item
Execution control
@item
Viewing and changing data
@item
Working with the stack
@item
Getting information
@item
Miscellaneous
@end itemize
@cindex debugger @subentry repeating commands
Each of these are discussed in the following subsections.
In the following descriptions, commands that may be abbreviated
show the abbreviation on a second description line.
A debugger command name may also be truncated if that partial
name is unambiguous. The debugger has the built-in capability to
automatically repeat the previous command just by hitting @kbd{Enter}.
This works for the commands @code{list}, @code{next}, @code{nexti},
@code{step}, @code{stepi}, and @code{continue} executed without any
argument.
@menu
* Breakpoint Control:: Control of Breakpoints.
* Debugger Execution Control:: Control of Execution.
* Viewing And Changing Data:: Viewing and Changing Data.
* Execution Stack:: Dealing with the Stack.
* Debugger Info:: Obtaining Information about the Program and
the Debugger State.
* Miscellaneous Debugger Commands:: Miscellaneous Commands.
@end menu
@node Breakpoint Control
@subsection Control of Breakpoints
As we saw earlier, the first thing you probably want to do in a debugging
session is to get your breakpoints set up, because your program
will otherwise just run as if it was not under the debugger. The commands for
controlling breakpoints are:
@table @asis
@cindex debugger @subentry commands @subentry @code{b} (@code{break})
@cindex debugger @subentry commands @subentry @code{break}
@cindex @code{break} debugger command
@cindex @code{b} debugger command (alias for @code{break})
@cindex set breakpoint
@cindex breakpoint @subentry setting
@item @code{break} [[@var{filename}@code{:}]@var{n} | @var{function}] [@code{"@var{expression}"}]
@itemx @code{b} [[@var{filename}@code{:}]@var{n} | @var{function}] [@code{"@var{expression}"}]
Without any argument, set a breakpoint at the next instruction
to be executed in the selected stack frame.
Arguments can be one of the following:
@c @asis for docbook
@c nested table
@table @asis
@item @var{n}
Set a breakpoint at line number @var{n} in the current source file.
@item @var{filename}@code{:}@var{n}
Set a breakpoint at line number @var{n} in source file @var{filename}.
@item @var{function}
Set a breakpoint at entry to (the first instruction of)
function @var{function}.
@end table
Each breakpoint is assigned a number that can be used to delete it from
the breakpoint list using the @code{delete} command.
With a breakpoint, you may also supply a condition. This is an
@command{awk} expression (enclosed in double quotes) that the debugger
evaluates whenever the breakpoint is reached. If the condition is true,
then the debugger stops execution and prompts for a command. Otherwise,
it continues executing the program.
@cindex debugger @subentry commands @subentry @code{clear}
@cindex @code{clear} debugger command
@cindex delete breakpoint @subentry at location
@cindex breakpoint @subentry at location, how to delete
@item @code{clear} [[@var{filename}@code{:}]@var{n} | @var{function}]
Without any argument, delete any breakpoint at the next instruction
to be executed in the selected stack frame. If the program stops at
a breakpoint, this deletes that breakpoint so that the program
does not stop at that location again. Arguments can be one of the following:
@c nested table
@table @asis
@item @var{n}
Delete breakpoint(s) set at line number @var{n} in the current source file.
@item @var{filename}@code{:}@var{n}
Delete breakpoint(s) set at line number @var{n} in source file @var{filename}.
@item @var{function}
Delete breakpoint(s) set at entry to function @var{function}.
@end table
@cindex debugger @subentry commands @subentry @code{condition}
@cindex @code{condition} debugger command
@cindex breakpoint @subentry condition
@item @code{condition} @var{n} @code{"@var{expression}"}
Add a condition to existing breakpoint or watchpoint @var{n}. The
condition is an @command{awk} expression @emph{enclosed in double quotes}
that the debugger evaluates
whenever the breakpoint or watchpoint is reached. If the condition is true, then
the debugger stops execution and prompts for a command. Otherwise,
the debugger continues executing the program. If the condition expression is
not specified, any existing condition is removed (i.e., the breakpoint or
watchpoint is made unconditional).
@cindex debugger @subentry commands @subentry @code{d} (@code{delete})
@cindex debugger @subentry commands @subentry @code{delete}
@cindex @code{delete} debugger command
@cindex @code{d} debugger command (alias for @code{delete})
@cindex delete breakpoint @subentry by number
@cindex breakpoint @subentry delete by number
@item @code{delete} [@var{n1 n2} @dots{}] [@var{n}--@var{m}]
@itemx @code{d} [@var{n1 n2} @dots{}] [@var{n}--@var{m}]
Delete specified breakpoints or a range of breakpoints. Delete
all defined breakpoints if no argument is supplied.
@cindex debugger @subentry commands @subentry @code{disable}
@cindex @code{disable} debugger command
@cindex disable breakpoint
@cindex breakpoint @subentry how to disable or enable
@item @code{disable} [@var{n1 n2} @dots{} | @var{n}--@var{m}]
Disable specified breakpoints or a range of breakpoints. Without
any argument, disable all breakpoints.
@cindex debugger @subentry commands @subentry @code{e} (@code{enable})
@cindex debugger @subentry commands @subentry @code{enable}
@cindex @code{enable} debugger command
@cindex @code{e} debugger command (alias for @code{enable})
@cindex enable breakpoint
@item @code{enable} [@code{del} | @code{once}] [@var{n1 n2} @dots{}] [@var{n}--@var{m}]
@itemx @code{e} [@code{del} | @code{once}] [@var{n1 n2} @dots{}] [@var{n}--@var{m}]
Enable specified breakpoints or a range of breakpoints. Without
any argument, enable all breakpoints.
Optionally, you can specify how to enable the breakpoints:
@c nested table
@table @code
@item del
Enable the breakpoints temporarily, then delete each one when
the program stops at it.
@item once
Enable the breakpoints temporarily, then disable each one when
the program stops at it.
@end table
@cindex debugger @subentry commands @subentry @code{ignore}
@cindex @code{ignore} debugger command
@cindex ignore breakpoint
@item @code{ignore} @var{n} @var{count}
Ignore breakpoint number @var{n} the next @var{count} times it is
hit.
@cindex debugger @subentry commands @subentry @code{t} (@code{tbreak})
@cindex debugger @subentry commands @subentry @code{tbreak}
@cindex @code{tbreak} debugger command
@cindex @code{t} debugger command (alias for @code{tbreak})
@cindex temporary breakpoint
@item @code{tbreak} [[@var{filename}@code{:}]@var{n} | @var{function}]
@itemx @code{t} [[@var{filename}@code{:}]@var{n} | @var{function}]
Set a temporary breakpoint (enabled for only one stop).
The arguments are the same as for @code{break}.
@end table
@node Debugger Execution Control
@subsection Control of Execution
Now that your breakpoints are ready, you can start running the program
and observing its behavior. There are more commands for controlling
execution of the program than we saw in our earlier example:
@table @asis
@cindex debugger @subentry commands @subentry @code{commands}
@cindex @code{commands} debugger command
@cindex debugger @subentry commands @subentry @code{silent}
@cindex @code{silent} debugger command
@cindex debugger @subentry commands @subentry @code{end}
@cindex @code{end} debugger command
@cindex breakpoint @subentry commands to execute at
@cindex commands to execute at breakpoint
@item @code{commands} [@var{n}]
@itemx @code{silent}
@itemx @dots{}
@itemx @code{end}
Set a list of commands to be executed upon stopping at
a breakpoint or watchpoint. @var{n} is the breakpoint or watchpoint number.
Without a number, the last one set is used. The actual commands follow,
starting on the next line, and terminated by the @code{end} command.
If the command @code{silent} is in the list, the usual messages about
stopping at a breakpoint and the source line are not printed. Any command
in the list that resumes execution (e.g., @code{continue}) terminates the list
(an implicit @code{end}), and subsequent commands are ignored.
For example:
@example
gawk> @kbd{commands}
> @kbd{silent}
> @kbd{printf "A silent breakpoint; i = %d\n", i}
> @kbd{info locals}
> @kbd{set i = 10}
> @kbd{continue}
> @kbd{end}
gawk>
@end example
@cindex debugger @subentry commands @subentry @code{c} (@code{continue})
@cindex debugger @subentry commands @subentry @code{continue}
@cindex continue program, in debugger
@cindex @code{continue} debugger command
@item @code{continue} [@var{count}]
@itemx @code{c} [@var{count}]
Resume program execution. If continued from a breakpoint and @var{count} is
specified, ignore the breakpoint at that location the next @var{count} times
before stopping.
@cindex debugger @subentry commands @subentry @code{finish}
@cindex @code{finish} debugger command
@item @code{finish}
Execute until the selected stack frame returns.
Print the returned value.
@cindex debugger @subentry commands @subentry @code{n} (@code{next})
@cindex debugger @subentry commands @subentry @code{next}
@cindex @code{next} debugger command
@cindex @code{n} debugger command (alias for @code{next})
@cindex single-step execution, in the debugger
@item @code{next} [@var{count}]
@itemx @code{n} [@var{count}]
Continue execution to the next source line, stepping over function calls.
The argument @var{count} controls how many times to repeat the action, as
in @code{step}.
@cindex debugger @subentry commands @subentry @code{ni} (@code{nexti})
@cindex debugger @subentry commands @subentry @code{nexti}
@cindex @code{nexti} debugger command
@cindex @code{ni} debugger command (alias for @code{nexti})
@item @code{nexti} [@var{count}]
@itemx @code{ni} [@var{count}]
Execute one (or @var{count}) instruction(s), stepping over function calls.
@cindex debugger @subentry commands @subentry @code{return}
@cindex @code{return} debugger command
@item @code{return} [@var{value}]
Cancel execution of a function call. If @var{value} (either a string or a
number) is specified, it is used as the function's return value. If used in a
frame other than the innermost one (the currently executing function; i.e.,
frame number 0), discard all inner frames in addition to the selected one,
and the caller of that frame becomes the innermost frame.
@cindex debugger @subentry commands @subentry @code{r} (@code{run})
@cindex debugger @subentry commands @subentry @code{run}
@cindex @code{run} debugger command
@cindex @code{r} debugger command (alias for @code{run})
@item @code{run}
@itemx @code{r}
Start/restart execution of the program. When restarting, the debugger
retains the current breakpoints, watchpoints, command history,
automatic display variables, and debugger options.
@cindex debugger @subentry commands @subentry @code{s} (@code{step})
@cindex debugger @subentry commands @subentry @code{step}
@cindex @code{step} debugger command
@cindex @code{s} debugger command (alias for @code{step})
@item @code{step} [@var{count}]
@itemx @code{s} [@var{count}]
Continue execution until control reaches a different source line in the
current stack frame, stepping inside any function called within
the line. If the argument @var{count} is supplied, steps that many times before
stopping, unless it encounters a breakpoint or watchpoint.
@cindex debugger @subentry commands @subentry @code{si} (@code{stepi})
@cindex debugger @subentry commands @subentry @code{stepi}
@cindex @code{stepi} debugger command
@cindex @code{si} debugger command (alias for @code{stepi})
@item @code{stepi} [@var{count}]
@itemx @code{si} [@var{count}]
Execute one (or @var{count}) instruction(s), stepping inside function calls.
(For illustration of what is meant by an ``instruction'' in @command{gawk},
see the output shown under @code{dump} in @ref{Miscellaneous Debugger Commands}.)
@cindex debugger @subentry commands @subentry @code{u} (@code{until})
@cindex debugger @subentry commands @subentry @code{until}
@cindex @code{until} debugger command
@cindex @code{u} debugger command (alias for @code{until})
@item @code{until} [[@var{filename}@code{:}]@var{n} | @var{function}]
@itemx @code{u} [[@var{filename}@code{:}]@var{n} | @var{function}]
Without any argument, continue execution until a line past the current
line in the current stack frame is reached. With an argument,
continue execution until the specified location is reached, or the current
stack frame returns.
@end table
@node Viewing And Changing Data
@subsection Viewing and Changing Data
The commands for viewing and changing variables inside of @command{gawk} are:
@table @asis
@cindex debugger @subentry commands @subentry @code{display}
@cindex @code{display} debugger command
@item @code{display} [@var{var} | @code{$}@var{n}]
Add variable @var{var} (or field @code{$@var{n}}) to the display list.
The value of the variable or field is displayed each time the program stops.
Each variable added to the list is identified by a unique number:
@example
gawk> @kbd{display x}
@print{} 10: x = 1
@end example
@noindent
This displays the assigned item number, the variable name, and its current value.
If the display variable refers to a function parameter, it is silently
deleted from the list as soon as the execution reaches a context where
no such variable of the given name exists.
Without argument, @code{display} displays the current values of
items on the list.
@cindex debugger @subentry commands @subentry @code{eval}
@cindex @code{eval} debugger command
@cindex evaluate expressions, in debugger
@item @code{eval "@var{awk statements}"}
Evaluate @var{awk statements} in the context of the running program.
You can do anything that an @command{awk} program would do: assign
values to variables, call functions, and so on.
@quotation NOTE
You cannot use @code{eval} to execute a statement containing
any of the following:
@code{exit},
@code{getline},
@code{next},
@code{nextfile},
or
@code{return}.
@end quotation
@item @code{eval} @var{param}, @dots{}
@itemx @var{awk statements}
@itemx @code{end}
This form of @code{eval} is similar, but it allows you to define
``local variables'' that exist in the context of the
@var{awk statements}, instead of using variables or function
parameters defined by the program.
@cindex debugger @subentry commands @subentry @code{p} (@code{print})
@cindex debugger @subentry commands @subentry @code{print}
@cindex @code{print} debugger command
@cindex @code{p} debugger command (alias for @code{print})
@cindex print variables, in debugger
@item @code{print} @var{var1}[@code{,} @var{var2} @dots{}]
@itemx @code{p} @var{var1}[@code{,} @var{var2} @dots{}]
Print the value of a @command{gawk} variable or field.
Fields must be referenced by constants:
@example
gawk> @kbd{print $3}
@end example
@noindent
This prints the third field in the input record (if the specified field does not
exist, it prints @samp{Null field}). A variable can be an array element, with
the subscripts being constant string values. To print the contents of an array,
prefix the name of the array with the @samp{@@} symbol:
@example
gawk> @kbd{print @@a}
@end example
@noindent
This prints the indices and the corresponding values for all elements in
the array @code{a}.
@cindex debugger @subentry commands @subentry @code{printf}
@cindex @code{printf} debugger command
@item @code{printf} @var{format} [@code{,} @var{arg} @dots{}]
Print formatted text. The @var{format} may include escape sequences,
such as @samp{\n}
(@pxref{Escape Sequences}).
No newline is printed unless one is specified.
@cindex debugger @subentry commands @subentry @code{set}
@cindex @code{set} debugger command
@cindex assign values to variables, in debugger
@item @code{set} @var{var}@code{=}@var{value}
Assign a constant (number or string) value to an @command{awk} variable
or field.
String values must be enclosed between double quotes (@code{"}@dots{}@code{"}).
You can also set special @command{awk} variables, such as @code{FS},
@code{NF}, @code{NR}, and so on.
@cindex debugger @subentry commands @subentry @code{w} (@code{watch})
@cindex debugger @subentry commands @subentry @code{watch}
@cindex @code{watch} debugger command
@cindex @code{w} debugger command (alias for @code{watch})
@cindex set watchpoint
@item @code{watch} @var{var} | @code{$}@var{n} [@code{"@var{expression}"}]
@itemx @code{w} @var{var} | @code{$}@var{n} [@code{"@var{expression}"}]
Add variable @var{var} (or field @code{$@var{n}}) to the watch list.
The debugger then stops whenever
the value of the variable or field changes. Each watched item is assigned a
number that can be used to delete it from the watch list using the
@code{unwatch} command.
With a watchpoint, you may also supply a condition. This is an
@command{awk} expression (enclosed in double quotes) that the debugger
evaluates whenever the watchpoint is reached. If the condition is true,
then the debugger stops execution and prompts for a command. Otherwise,
@command{gawk} continues executing the program.
@cindex debugger @subentry commands @subentry @code{undisplay}
@cindex @code{undisplay} debugger command
@cindex stop automatic display, in debugger
@item @code{undisplay} [@var{n}]
Remove item number @var{n} (or all items, if no argument) from the
automatic display list.
@cindex debugger @subentry commands @subentry @code{unwatch}
@cindex @code{unwatch} debugger command
@cindex delete watchpoint
@item @code{unwatch} [@var{n}]
Remove item number @var{n} (or all items, if no argument) from the
watch list.
@end table
@node Execution Stack
@subsection Working with the Stack
Whenever you run a program that contains any function calls,
@command{gawk} maintains a stack of all of the function calls leading up
to where the program is right now. You can see how you got to where you are,
and also move around in the stack to see what the state of things was in the
functions that called the one you are in. The commands for doing this are:
@table @asis
@cindex debugger @subentry commands @subentry @code{bt} (@code{backtrace})
@cindex debugger @subentry commands @subentry @code{backtrace}
@cindex debugger @subentry commands @subentry @code{where} (@code{backtrace})
@cindex @code{backtrace} debugger command
@cindex @code{bt} debugger command (alias for @code{backtrace})
@cindex @code{where} debugger command (alias for @code{backtrace})
@cindex call stack @subentry display in debugger
@cindex traceback, display in debugger
@item @code{backtrace} [@var{count}]
@itemx @code{bt} [@var{count}]
@itemx @code{where} [@var{count}]
Print a backtrace of all function calls (stack frames), or innermost @var{count}
frames if @var{count} > 0. Print the outermost @var{count} frames if
@var{count} < 0. The backtrace displays the name and arguments to each
function, the source @value{FN}, and the line number.
The alias @code{where} for @code{backtrace} is provided for longtime
GDB users who may be used to that command.
@cindex debugger @subentry commands @subentry @code{down}
@cindex @code{down} debugger command
@item @code{down} [@var{count}]
Move @var{count} (default 1) frames down the stack toward the innermost frame.
Then select and print the frame.
@cindex debugger @subentry commands @subentry @code{f} (@code{frame})
@cindex debugger @subentry commands @subentry @code{frame}
@cindex @code{frame} debugger command
@cindex @code{f} debugger command (alias for @code{frame})
@item @code{frame} [@var{n}]
@itemx @code{f} [@var{n}]
Select and print stack frame @var{n}. Frame 0 is the currently executing,
or @dfn{innermost}, frame (function call); frame 1 is the frame that
called the innermost one. The highest-numbered frame is the one for the
main program. The printed information consists of the frame number,
function and argument names, source file, and the source line.
@cindex debugger @subentry commands @subentry @code{up}
@cindex @code{up} debugger command
@item @code{up} [@var{count}]
Move @var{count} (default 1) frames up the stack toward the outermost frame.
Then select and print the frame.
@end table
@node Debugger Info
@subsection Obtaining Information About the Program and the Debugger State
Besides looking at the values of variables, there is often a need to get
other sorts of information about the state of your program and of the
debugging environment itself. The @command{gawk} debugger has one command that
provides this information, appropriately called @code{info}. @code{info}
is used with one of a number of arguments that tell it exactly what
you want to know:
@table @asis
@cindex debugger @subentry commands @subentry @code{i} (@code{info})
@cindex debugger @subentry commands @subentry @code{info}
@cindex @code{info} debugger command
@cindex @code{i} debugger command (alias for @code{info})
@item @code{info} @var{what}
@itemx @code{i} @var{what}
The value for @var{what} should be one of the following:
@c nested table
@table @code
@item args
@cindex show in debugger @subentry function arguments
@cindex function arguments, show in debugger
List arguments of the selected frame.
@item break
@cindex show in debugger @subentry breakpoints
@cindex breakpoint @subentry show all in debugger
List all currently set breakpoints.
@item display
@cindex automatic displays, in debugger
List all items in the automatic display list.
@item frame
@cindex describe call stack frame, in debugger
Give a description of the selected stack frame.
@item functions
@cindex list function definitions, in debugger
@cindex function definitions, list in debugger
List all function definitions including source @value{FN}s and
line numbers.
@item locals
@cindex show in debugger @subentry local variables
@cindex local variables @subentry show in debugger
List local variables of the selected frame.
@item source
@cindex show in debugger @subentry name of current source file
@cindex current source file, show in debugger
@cindex source file, show in debugger
Print the name of the current source file. Each time the program stops, the
current source file is the file containing the current instruction.
When the debugger first starts, the current source file is the first file
included via the @option{-f} option. The
@samp{list @var{filename}:@var{lineno}} command can
be used at any time to change the current source.
@item sources
@cindex show in debugger @subentry all source files
@cindex all source files, show in debugger
List all program sources.
@item variables
@cindex list all global variables, in debugger
@cindex global variables, show in debugger
List all global variables.
@item watch
@cindex show in debugger @subentry watchpoints
@cindex watchpoints, show in debugger
List all items in the watch list.
@end table
@end table
Additional commands give you control over the debugger, the ability to
save the debugger's state, and the ability to run debugger commands
from a file. The commands are:
@table @asis
@cindex debugger @subentry commands @subentry @code{o} (@code{option})
@cindex debugger @subentry commands @subentry @code{option}
@cindex @code{option} debugger command
@cindex @code{o} debugger command (alias for @code{option})
@cindex display debugger options
@cindex debugger @subentry options
@item @code{option} [@var{name}[@code{=}@var{value}]]
@itemx @code{o} [@var{name}[@code{=}@var{value}]]
Without an argument, display the available debugger options
and their current values. @samp{option @var{name}} shows the current
value of the named option. @samp{option @var{name}=@var{value}} assigns
a new value to the named option.
The available options are:
@c nested table
@c asis for docbook
@table @asis
@item @code{history_size}
@cindex debugger @subentry history size
Set the maximum number of lines to keep in the history file
@file{./.gawk_history}. The default is 100.
@item @code{listsize}
@cindex debugger @subentry default list amount
Specify the number of lines that @code{list} prints. The default is 15.
@item @code{outfile}
@cindex redirect @command{gawk} output, in debugger
Send @command{gawk} output to a file; debugger output still goes
to standard output. An empty string (@code{""}) resets output to
standard output.
@item @code{prompt}
@cindex debugger @subentry prompt
Change the debugger prompt. The default is @samp{@w{gawk> }}.
@item @code{save_history} [@code{on} | @code{off}]
@cindex debugger @subentry history file
Save command history to file @file{./.gawk_history}.
The default is @code{on}.
@item @code{save_options} [@code{on} | @code{off}]
@cindex save debugger options
Save current options to file @file{./.gawkrc} upon exit.
The default is @code{on}.
Options are read back into the next session upon startup.
@item @code{trace} [@code{on} | @code{off}]
@cindex instruction tracing, in debugger
@cindex debugger @subentry instruction tracing
Turn instruction tracing on or off. The default is @code{off}.
@end table
@cindex debugger @subentry save commands to a file
@item @code{save} @var{filename}
Save the commands from the current session to the given @value{FN},
so that they can be replayed using the @command{source} command.
@item @code{source} @var{filename}
@cindex debugger @subentry read commands from a file
Run command(s) from a file; an error in any command does not
terminate execution of subsequent commands. Comments (lines starting
with @samp{#}) are allowed in a command file.
Empty lines are ignored; they do @emph{not}
repeat the last command.
You can't restart the program by having more than one @code{run}
command in the file. Also, the list of commands may include additional
@code{source} commands; however, the @command{gawk} debugger will not source the
same file more than once in order to avoid infinite recursion.
In addition to, or instead of, the @code{source} command, you can use
the @option{-D @var{file}} or @option{--debug=@var{file}} command-line
options to execute commands from a file non-interactively
(@pxref{Options}).
@end table
@node Miscellaneous Debugger Commands
@subsection Miscellaneous Commands
There are a few more commands that do not fit into the
previous categories, as follows:
@table @asis
@cindex debugger @subentry commands @subentry @code{dump}
@cindex @code{dump} debugger command
@item @code{dump} [@var{filename}]
Dump byte code of the program to standard output or to the file
named in @var{filename}. This prints a representation of the internal
instructions that @command{gawk} executes to implement the @command{awk}
commands in a program. This can be very enlightening, as the following
partial dump of Davide Brini's obfuscated code
(@pxref{Signature Program}) demonstrates:
@c FIXME: This will need updating if num-handler branch is ever merged in.
@smallexample
@group
gawk> @kbd{dump}
@print{} # BEGIN
@print{}
@print{} [ 1:0xfcd340] Op_rule : [in_rule = BEGIN] [source_file = brini.awk]
@end group
@print{} [ 1:0xfcc240] Op_push_i : "~" [MALLOC|STRING|STRCUR]
@print{} [ 1:0xfcc2a0] Op_push_i : "~" [MALLOC|STRING|STRCUR]
@print{} [ 1:0xfcc280] Op_match :
@print{} [ 1:0xfcc1e0] Op_store_var : O
@print{} [ 1:0xfcc2e0] Op_push_i : "==" [MALLOC|STRING|STRCUR]
@print{} [ 1:0xfcc340] Op_push_i : "==" [MALLOC|STRING|STRCUR]
@print{} [ 1:0xfcc320] Op_equal :
@print{} [ 1:0xfcc200] Op_store_var : o
@print{} [ 1:0xfcc380] Op_push : o
@print{} [ 1:0xfcc360] Op_plus_i : 0 [MALLOC|NUMCUR|NUMBER]
@print{} [ 1:0xfcc220] Op_push_lhs : o [do_reference = true]
@print{} [ 1:0xfcc300] Op_assign_plus :
@print{} [ :0xfcc2c0] Op_pop :
@print{} [ 1:0xfcc400] Op_push : O
@print{} [ 1:0xfcc420] Op_push_i : "" [MALLOC|STRING|STRCUR]
@print{} [ :0xfcc4a0] Op_no_op :
@print{} [ 1:0xfcc480] Op_push : O
@print{} [ :0xfcc4c0] Op_concat : [expr_count = 3] [concat_flag = 0]
@print{} [ 1:0xfcc3c0] Op_store_var : x
@print{} [ 1:0xfcc440] Op_push_lhs : X [do_reference = true]
@print{} [ 1:0xfcc3a0] Op_postincrement :
@print{} [ 1:0xfcc4e0] Op_push : x
@print{} [ 1:0xfcc540] Op_push : o
@print{} [ 1:0xfcc500] Op_plus :
@print{} [ 1:0xfcc580] Op_push : o
@print{} [ 1:0xfcc560] Op_plus :
@print{} [ 1:0xfcc460] Op_leq :
@print{} [ :0xfcc5c0] Op_jmp_false : [target_jmp = 0xfcc5e0]
@print{} [ 1:0xfcc600] Op_push_i : "%c" [MALLOC|STRING|STRCUR]
@print{} [ :0xfcc660] Op_no_op :
@print{} [ 1:0xfcc520] Op_assign_concat : c
@print{} [ :0xfcc620] Op_jmp : [target_jmp = 0xfcc440]
@dots{}
@print{} [ 2:0xfcc5a0] Op_K_printf : [expr_count = 17] [redir_type = ""]
@print{} [ :0xfcc140] Op_no_op :
@print{} [ :0xfcc1c0] Op_atexit :
@print{} [ :0xfcc640] Op_stop :
@print{} [ :0xfcc180] Op_no_op :
@print{} [ :0xfcd150] Op_after_beginfile :
@group
@print{} [ :0xfcc160] Op_no_op :
@print{} [ :0xfcc1a0] Op_after_endfile :
gawk>
@end group
@end smallexample
@cindex @code{exit} debugger command
@cindex exit the debugger
@item @code{exit}
Exit the debugger.
See the entry for @samp{quit}, later in this list.
@cindex debugger @subentry commands @subentry @code{h} (@code{help})
@cindex debugger @subentry commands @subentry @code{help}
@cindex @code{help} debugger command
@cindex @code{h} debugger command (alias for @code{help})
@item @code{help}
@itemx @code{h}
Print a list of all of the @command{gawk} debugger commands with a short
summary of their usage. @samp{help @var{command}} prints the information
about the command @var{command}.
@cindex debugger @subentry commands @subentry @code{l} (@code{list})
@cindex debugger @subentry commands @subentry @code{list}
@cindex @code{list} debugger command
@cindex @code{l} debugger command (alias for @code{list})
@item @code{list} [@code{-} | @code{+} | @var{n} | @var{filename}@code{:}@var{n} | @var{n}--@var{m} | @var{function}]
@itemx @code{l} [@code{-} | @code{+} | @var{n} | @var{filename}@code{:}@var{n} | @var{n}--@var{m} | @var{function}]
Print the specified lines (default 15) from the current source file
or the file named @var{filename}. The possible arguments to @code{list}
are as follows:
@c nested table
@table @asis
@item @code{-} (Minus)
Print lines before the lines last printed.
@item @code{+}
Print lines after the lines last printed.
@code{list} without any argument does the same thing.
@item @var{n}
Print lines centered around line number @var{n}.
@item @var{n}--@var{m}
Print lines from @var{n} to @var{m}.
@item @var{filename}@code{:}@var{n}
Print lines centered around line number @var{n} in
source file @var{filename}. This command may change the current source file.
@item @var{function}
Print lines centered around the beginning of the
function @var{function}. This command may change the current source file.
@end table
@cindex debugger @subentry commands @subentry @code{q} (@code{quit})
@cindex debugger @subentry commands @subentry @code{quit}
@cindex @code{quit} debugger command
@cindex @code{q} debugger command (alias for @code{quit})
@cindex exit the debugger
@item @code{quit}
@itemx @code{q}
Exit the debugger. Debugging is great fun, but sometimes we all have
to tend to other obligations in life, and sometimes we find the bug
and are free to go on to the next one! As we saw earlier, if you are
running a program, the debugger warns you when you type
@samp{q} or @samp{quit}, to make sure you really want to quit.
@cindex debugger @subentry commands @subentry @code{trace}
@cindex @code{trace} debugger command
@item @code{trace} [@code{on} | @code{off}]
Turn on or off continuous printing of the instructions that are about to
be executed, along with the @command{awk} lines they
implement. The default is @code{off}.
It is to be hoped that most of the ``opcodes'' in these instructions are
fairly self-explanatory, and using @code{stepi} and @code{nexti} while
@code{trace} is on will make them into familiar friends.
@end table
@node Readline Support
@section Readline Support
@cindex command completion, in debugger
@cindex debugger @subentry command completion
@cindex history expansion, in debugger
@cindex debugger @subentry history expansion
If @command{gawk} is compiled with
@uref{http://cnswww.cns.cwru.edu/php/chet/readline/readline.html,
the GNU Readline library}, you can take advantage of that library's
command completion and history expansion features. The following types
of completion are available:
@table @asis
@item Command completion
Command names.
@item Source @value{FN} completion
Source @value{FN}s. Relevant commands are
@code{break},
@code{clear},
@code{list},
@code{tbreak},
and
@code{until}.
@item Argument completion
Non-numeric arguments to a command.
Relevant commands are @code{enable} and @code{info}.
@item Variable name completion
Global variable names, and function arguments in the current context
if the program is running. Relevant commands are
@code{display},
@code{print},
@code{set},
and
@code{watch}.
@end table
@node Limitations
@section Limitations
@cindex debugger @subentry limitations
We hope you find the @command{gawk} debugger useful and enjoyable to work with,
but as with any program, especially in its early releases, it still has
some limitations. A few that it's worth being aware of are:
@itemize @value{BULLET}
@item
At this point, the debugger does not give a detailed explanation of
what you did wrong when you type in something it doesn't like. Rather, it just
responds @samp{syntax error}. When you do figure out what your mistake was,
though, you'll feel like a real guru.
@item
@c NOTE: no comma after the ref{} on purpose, due to following
@c parenthetical remark.
If you perused the dump of opcodes in @ref{Miscellaneous Debugger Commands}
(or if you are already familiar with @command{gawk} internals),
you will realize that much of the internal manipulation of data
in @command{gawk}, as in many interpreters, is done on a stack.
@code{Op_push}, @code{Op_pop}, and the like are the ``bread and butter'' of
most @command{gawk} code.
Unfortunately, as of now, the @command{gawk}
debugger does not allow you to examine the stack's contents.
That is, the intermediate results of expression evaluation are on the
stack, but cannot be printed. Rather, only variables that are defined
in the program can be printed. Of course, a workaround for
this is to use more explicit variables at the debugging stage and then
change back to obscure, perhaps more optimal code later.
@item
There is no way to look ``inside'' the process of compiling
regular expressions to see if you got it right. As an @command{awk}
programmer, you are expected to know the meaning of
@code{/[^[:alnum:][:blank:]]/}.
@item
The @command{gawk} debugger is designed to be used by running a program (with all its
parameters) on the command line, as described in @ref{Debugger Invocation}.
There is no way (as of now) to attach or ``break into'' a running program.
This seems reasonable for a language that is used mainly for quickly
executing, short programs.
@item
The @command{gawk} debugger only accepts source code supplied with the @option{-f} option.
If you have a shell script that provides an @command{awk} program as a command
line parameter, and you need to use the debugger, you can write the script
to a temporary file, and use that as the program, with the @option{-f} option. This
might look like this:
@example
cat << \EOF > /tmp/script.$$
@dots{} @ii{Your program here}
EOF
gawk -D -f /tmp/script.$$
rm /tmp/script.$$
@end example
@end itemize
@ignore
@c 11/2016: This no longer applies after all the type cleanup work that's been done.
One other point is worth discussing. Conventional debuggers run in a
separate process (and thus address space) from the programs that they
debug (the @dfn{debuggee}, if you will).
The @command{gawk} debugger is different; it is an integrated part
of @command{gawk} itself. This makes it possible, in rare cases,
for @command{gawk} to become an excellent demonstrator of Heisenberg
Uncertainty physics, where the mere act of observing something can change
it. Consider the following:@footnote{Thanks to Hermann Peifer for
this example.}
@example
$ @kbd{cat test.awk}
@print{} @{ print typeof($1), typeof($2) @}
$ @kbd{cat test.data}
@print{} abc 123
$ @kbd{gawk -f test.awk test.data}
@print{} strnum strnum
@end example
This is all as expected: field data has the STRNUM attribute
(@pxref{Variable Typing}). Now watch what happens when we run
this program under the debugger:
@example
$ @kbd{gawk -D -f test.awk test.data}
gawk> @kbd{w $1} @ii{Set watchpoint on} $1
@print{} Watchpoint 1: $1
gawk> @kbd{w $2} @ii{Set watchpoint on} $2
@print{} Watchpoint 2: $2
gawk> @kbd{r} @ii{Start the program}
@print{} Starting program:
@print{} Stopping in Rule ...
@print{} Watchpoint 1: $1 @ii{Watchpoint fires}
@print{} Old value: ""
@print{} New value: "abc"
@print{} main() at `test.awk':1
@print{} 1 @{ print typeof($1), typeof($2) @}
gawk> @kbd{n} @ii{Keep going @dots{}}
@print{} Watchpoint 2: $2 @ii{Watchpoint fires}
@print{} Old value: ""
@print{} New value: "123"
@print{} main() at `test.awk':1
@print{} 1 @{ print typeof($1), typeof($2) @}
gawk> @kbd{n} @ii{Get result from} typeof()
@print{} strnum number @ii{Result for} $2 @ii{isn't right}
@print{} Program exited normally with exit value: 0
gawk> @kbd{quit}
@end example
In this case, the act of comparing the new value of @code{$2}
with the old one caused @command{gawk} to evaluate it and determine that it
is indeed a number, and this is reflected in the result of
@code{typeof()}.
Cases like this where the debugger is not transparent to the program's
execution should be rare. If you encounter one, please report it
(@pxref{Bugs}).
@end ignore
@ignore
Look forward to a future release when these and other missing features may
be added, and of course feel free to try to add them yourself!
@end ignore
@node Debugging Summary
@section Summary
@itemize @value{BULLET}
@item
Programs rarely work correctly the first time. Finding bugs
is called debugging, and a program that helps you find bugs is a
debugger. @command{gawk} has a built-in debugger that works very
similarly to the GNU Debugger, GDB.
@item
Debuggers let you step through your program one statement at a time,
examine and change variable and array values, and do a number of other
things that let you understand what your program is actually doing (as
opposed to what it is supposed to do).
@item
Like most debuggers, the @command{gawk} debugger works in terms of stack
frames, and lets you set both breakpoints (stop at a point in the code)
and watchpoints (stop when a data value changes).
@item
The debugger command set is fairly complete, providing control over
breakpoints, execution, viewing and changing data, working with the stack,
getting information, and other tasks.
@item
If the GNU Readline library is available when @command{gawk} is
compiled, it is used by the debugger to provide command-line history
and editing.
@item
Usually, the debugger does not not affect the
program being debugged, but occasionally it can.
@end itemize
@hyphenation{name-space name-spaces Name-space Name-spaces}
@node Namespaces
@chapter Namespaces in @command{gawk}
This @value{CHAPTER} describes a feature that is specific to @command{gawk}.
@quotation CAUTION
This feature described in this chapter is new. It is entirely
possible, and even likely, that there are dark corners (if not bugs)
still lurking within the implementation. If you find any such,
please report them (@xref{Bugs}).
@end quotation
@menu
* Global Namespace:: The global namespace in standard
@command{awk}.
* Qualified Names:: How to qualify names with a namespace.
* Default Namespace:: The default namespace.
* Changing The Namespace:: How to change the namespace.
* Naming Rules:: Namespace and Component Naming Rules.
* Internal Name Management:: How names are stored internally.
* Namespace Example:: An example of code using a namespace.
* Namespace And Features:: Namespaces and other @command{gawk} features.
* Namespace Summary:: Summarizing namespaces.
@end menu
@node Global Namespace
@section Standard @command{awk}'s Single Namespace
@cindex namespace @subentry definition of
@cindex namespace @subentry standard @command{awk}, global
In standard @command{awk}, there is a single, global, @dfn{namespace}.
This means that @emph{all} function names and global variable names must
be unique. For example, two different @command{awk} source files cannot
both define a function named @code{min()}, or define the same identifier,
used as a scalar in one and as an array in the other.
This situation is okay when programs are small, say a few hundred
lines, or even a few thousand, but it prevents the development of
reusable libraries of @command{awk} functions, and can inadvertently
cause independently-developed library files to accidentally step on each
other's ``private'' global variables
(@pxref{Library Names}).
@cindex package, definition of
@cindex module, definition of
Most other programming languages solve this issue by providing some kind
of namespace control: a way to say ``this function is in namespace @var{xxx},
and that function is in namespace @var{yyy}.'' (Of course, there is then
still a single namespace for the namespaces, but the hope is that there
are much fewer namespaces in use by any given program, and thus much
less chance for collisions.) These facilities are sometimes referred
to as @dfn{packages} or @dfn{modules}.
Starting with @value{PVERSION} 5.0, @command{gawk} provides a
simple mechanism to put functions and global variables into separate namespaces.
@node Qualified Names
@section Qualified Names
@cindex qualified name @subentry definition of
@cindex namespaces @subentry qualified names
@cindex @code{:} (colon) @subentry @code{::} namespace separator
@cindex colon (@code{:}) @subentry @code{::} namespace separator
@cindex component name
A @dfn{qualified name} is an identifier that includes a namespace name,
the namespace separator @code{::}, and a @dfn{component} name. For example, one
might have a function named @code{posix::getpid()}. Here, the namespace
is @code{posix} and the function name within the namespace (the component)
is @code{getpid()}. The namespace and component names are separated by
a double-colon. Only one such separator is allowed in a qualified name.
@quotation NOTE
Unlike C++, the @code{::} is @emph{not} an operator. No spaces are
allowed between the namespace name, the @code{::}, and the component name.
@end quotation
@cindex qualified name @subentry use of
You must use qualified names from one namespace to access variables
and functions in another. This is especially important when using
variable names to index the special @code{SYMTAB} array (@pxref{Auto-set}),
and when making indirect function calls (@pxref{Indirect Calls}).
@node Default Namespace
@section The Default Namespace
@cindex namespace @subentry default
@cindex namespace @subentry @code{awk}
@cindex @code{awk} @subentry namespace
The default namespace, not surprisingly, is @code{awk}.
All of the predefined @command{awk} and @command{gawk} variables
are in this namespace, and thus have qualified names like
@code{awk::ARGC}, @code{awk::NF}, and so on.
@cindex uppercase names, namespace for
Furthermore, even when you have changed the namespace for your
current source file (@pxref{Changing The Namespace}), @command{gawk}
forces unqualified identifiers whose names are all uppercase letters
to be in the @code{awk} namespace. This makes it possible for you to easily
reference @command{gawk}'s global variables from different namespaces.
It also keeps your code looking natural.
@node Changing The Namespace
@section Changing The Namespace
@cindex namespaces @subentry changing
@cindex @code{@@} (at-sign) @subentry @code{@@namespace} directive
@cindex at-sign (@code{@@}) @subentry @code{@@namespace} directive
@cindex @code{@@namespace} directive @sortas{namespace directive}
In order to set the current namespace, use an @code{@@namespace} directive
at the top level of your program:
@example
@@namespace "passwd"
BEGIN @{ @dots{} @}
@dots{}
@end example
After this directive, all simple non-completely-uppercase identifiers are
placed into the @code{passwd} namespace.
You can change the namespace multiple times within a single
source file, although this is likely to become confusing if you
do it too much.
@quotation NOTE
Association of unqualified identifiers to a namespace is handled while
@command{gawk} parses your program, @emph{before} it starts to run. There is
no concept of a ``current'' namespace once your program starts executing.
Be sure you understand this.
@end quotation
@cindex namespace @subentry implicit
@cindex implicit namespace
Each source file for @option{-i} and @option{-f} starts out with
an implicit @samp{@@namespace "awk"}. Similarly, each chunk of
command-line code supplied with @option{-e} has such an implicit
initial statement (@pxref{Options}).
@cindex current namespace, pushing and popping
@cindex namespace @subentry pushing and popping
Files included with @code{@@include} (@pxref{Include Files}) ``push''
and ``pop'' the current namespace. That is, each @code{@@include} saves
the current namespace and starts over with an implicit @samp{@@namespace
"awk"} which remains in effect until an explicit @code{@@namespace}
directive is seen. When @command{gawk} finishes processing the included
file, the saved namespace is restored and processing continues where it
left off in the original file.
@cindex @code{@@} (at-sign) @subentry @code{@@namespace} directive @subentry @code{BEGIN}, @code{BEGINFILE}, @code{END}, @code{ENDFILE} and
@cindex at-sign (@code{@@}) @subentry @code{@@namespace} directive @subentry @code{BEGIN}, @code{BEGINFILE}, @code{END}, @code{ENDFILE} and
@cindex @code{BEGIN} pattern @subentry @code{@@namespace} directive and
@cindex @code{BEGINFILE} pattern @subentry @code{@@namespace} directive and
@cindex @code{END} pattern @subentry @code{@@namespace} directive and
@cindex @code{ENDFILE} pattern @subentry @code{@@namespace} directive and
@cindex @code{@@namespace} directive @sortas{namespace directive}
The use of @code{@@namespace} has no influence upon the order of execution
of @code{BEGIN}, @code{BEGINFILE}, @code{END}, and @code{ENDFILE} rules.
@node Naming Rules
@section Namespace and Component Naming Rules
@cindex naming rules, namespace and component names
@cindex namespaces @subentry naming rules
@c not "component names" to merge with other index entry
@cindex component name @subentry naming rules
A number of rules apply to the namespace and component names, as follows.
@itemize @bullet
@item
It is a syntax error to use qualified names for function parameter names.
@item
It is a syntax error to use any standard @command{awk} reserved word (such
as @code{if} or @code{for}), or the name of any standard built-in function
(such as @code{sin()} or @code{gsub()}) as either part of a qualified name.
Thus, the following produces a syntax error:
@example
@@namespace "example"
function gsub(str, pat, result) @{ @dots{} @}
@end example
@item
Outside the @code{awk} namespace, the names of the additional @command{gawk}
built-in functions (such as @code{gensub()} or @code{strftime()}) @emph{may}
be used as component names. The same set of names may be used as namespace
names, although this has the potential to be confusing.
@item
The additional @command{gawk} built-in functions may still be called
from outside the @code{awk} namespace by qualifying them. For example,
@code{awk::systime()}. Here is a somewhat silly example demonstrating
this rule and the previous one:
@example
BEGIN @{
print "in awk namespace, systime() =", systime()
@}
@@namespace "testing"
function systime()
@{
print "in testing namespace, systime() =", awk::systime()
@}
BEGIN @{
systime()
@}
@end example
@noindent
When run, it produces output like this:
@example
$ @kbd{gawk -f systime.awk}
@print{} in awk namespace, systime() = 1500488503
@print{} in testing namespace, systime() = 1500488503
@end example
@item
@command{gawk} pre-defined variable names may be used:
@code{NF::NR} is valid, if possibly not all that useful.
@end itemize
@node Internal Name Management
@section Internal Name Management
@cindex name management
@cindex @code{awk} @subentry namespace @subentry identifier name storage
@cindex @code{awk} @subentry namespace @subentry use for indirect function calls
For backwards compatibility, all identifiers in the @code{awk} namespace
are stored internally as unadorned identifiers (that is, without a
leading @samp{awk::}). This is mainly relevant
when using such identifiers as indices for @code{SYMTAB}, @code{FUNCTAB},
and @code{PROCINFO["identifiers"]} (@pxref{Auto-set}), and for use in
indirect function calls (@pxref{Indirect Calls}).
In program code, to refer to variables and functions in the @code{awk}
namespace from another namespace, you must still use the @samp{awk::}
prefix. For example:
@example
@@namespace "awk" @ii{This is the default namespace}
BEGIN @{
Title = "My Report" @ii{Qualified name is} awk::Title
@}
@@namespace "report" @ii{Now in} report @ii{namespace}
function compute() @ii{This is really} report::compute()
@{
print awk::Title @ii{But would be} SYMTAB["Title"]
@dots{}
@}
@end example
@node Namespace Example
@section Namespace Example
@cindex namespace @subentry example code
The following example is a revised version of the suite of routines
developed in @ref{Passwd Functions}. See there for an explanation
of how the code works.
The formulation here, due mainly to Andrew Schorr, is rather elegant.
All of the implementation functions and variables are in the
@code{passwd} namespace, whereas the main interface functions are
defined in the @code{awk} namespace.
@example
@c file eg/lib/ns_passwd.awk
# ns_passwd.awk --- access password file information
@c endfile
@ignore
@c file eg/lib/ns_passwd.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# May 1993
# Revised October 2000
# Revised December 2010
#
# Reworked for namespaces June 2017, with help from
# Andrew J.@: Schorr, aschorr@@telemetry-investments.com
@c endfile
@end ignore
@c file eg/lib/ns_passwd.awk
@@namespace "passwd"
BEGIN @{
# tailor this to suit your system
Awklib = "/usr/local/libexec/awk/"
@}
function Init( oldfs, oldrs, olddol0, pwcat, using_fw, using_fpat)
@{
if (Inited)
return
oldfs = FS
oldrs = RS
olddol0 = $0
using_fw = (PROCINFO["FS"] == "FIELDWIDTHS")
using_fpat = (PROCINFO["FS"] == "FPAT")
FS = ":"
RS = "\n"
pwcat = Awklib "pwcat"
while ((pwcat | getline) > 0) @{
Byname[$1] = $0
Byuid[$3] = $0
Bycount[++Total] = $0
@}
close(pwcat)
Count = 0
Inited = 1
FS = oldfs
if (using_fw)
FIELDWIDTHS = FIELDWIDTHS
else if (using_fpat)
FPAT = FPAT
RS = oldrs
$0 = olddol0
@}
function awk::getpwnam(name)
@{
Init()
return Byname[name]
@}
function awk::getpwuid(uid)
@{
Init()
return Byuid[uid]
@}
function awk::getpwent()
@{
Init()
if (Count < Total)
return Bycount[++Count]
return ""
@}
function awk::endpwent()
@{
Count = 0
@}
@c endfile
@end example
As you can see, this version also follows the convention mentioned in
@ref{Library Names}, whereby global variable and function names
start with a capital letter.
Here is a simple test program. Since it's in a separate file, unadorned
identifiers are sought for in the @code{awk} namespace:
@example
BEGIN @{
while ((p = getpwent()) != "")
print p
@}
@end example
@noindent
Here's what happens when it's run:
@example
$ @kbd{gawk -f ns_passwd.awk -f testpasswd.awk}
@print{} root:x:0:0:root:/root:/bin/bash
@print{} daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
@print{} bin:x:2:2:bin:/bin:/usr/sbin/nologin
@print{} sys:x:3:3:sys:/dev:/usr/sbin/nologin
@dots{}
@end example
@node Namespace And Features
@section Namespaces and Other @command{gawk} Features
This @value{SECTION} looks briefly at how the namespace facility interacts
with other important @command{gawk} features.
@cindex namespaces @subentry interaction with @subentry profiler
@cindex namespaces @subentry interaction with @subentry pretty printer
@cindex profiler, interaction with namespaces
@cindex pretty printer, interaction with namespaces
The profiler and pretty-printer (@pxref{Profiling}) have been enhanced
to understand namespaces and the namespace naming rules presented in
@ref{Naming Rules}. In particular, the output groups functions in the same
namespace together, and has @code{@@namespace} directives in front
of rules as necessary. This allows component names to be
simple identifiers, instead of using qualified identifiers everywhere.
@cindex namespaces @subentry interaction with @subentry debugger
@cindex debugger @subentry interaction with namespaces
Interaction with the debugger (@pxref{Debugging}) has not had to change
(at least as of this writing). Some of the internal byte codes changed
in order to accommodate namespaces, and the debugger's @code{dump} command
was adjusted to match.
@cindex namespaces @subentry interaction with @subentry extension API
@cindex extension API @subentry interaction with namespaces
The extension API (@pxref{Dynamic Extensions}) has always allowed for
placing functions into a different namespace, although this was not
previously implemented. However, the symbol lookup and symbol update
routines did not have provision for including a namespace. That has now
been corrected (@pxref{Symbol table by name}).
@xref{Extension Sample Inplace}, for a nice example of an extension that
leverages a namespace shared by cooperating @command{awk} and C code.
@node Namespace Summary
@section Summary
@itemize @value{BULLET}
@item
Standard @command{awk} provides a single namespace for all global
identifiers (scalars, arrays, and functions). This is limiting when
one wants to develop libraries of reusable functions or function suites.
@item
@command{gawk} provides multiple namespaces by using qualified names:
names consisting of a namespace name, a double colon, @code{::}, and a
component name. Namespace names might still possibly conflict, but this
is true of any language providing namespaces, modules, or packages.
@item
The default namespace is @command{awk}. The rules for namespace and
component names are provided in @ref{Naming Rules}. The rules are
designed in such a way as to make namespace-aware code continue to
look and work naturally while still providing the necessary power and
flexibility.
@item
Other parts of @command{gawk} have been extended as necessary to integrate
namespaces smoothly with their operation. This applies most notably to
the profiler / pretty-printer (@pxref{Profiling}) and to the extension
facility (@pxref{Dynamic Extensions}).
@cindex namespaces @subentry backwards compatibility
@item
Overall, the namespace facility was designed and implemented such that
backwards compatibility is paramount. Programs that don't use namespaces
should see absolutely no difference in behavior when run by a namespace-capable
version of @command{gawk}.
@end itemize
@node Arbitrary Precision Arithmetic
@chapter Arithmetic and Arbitrary-Precision Arithmetic with @command{gawk}
@cindex arbitrary precision
@cindex multiple precision
@cindex infinite precision
@cindex floating-point @subentry numbers @subentry arbitrary-precision
This @value{CHAPTER} introduces some basic concepts relating to
how computers do arithmetic and defines some important terms.
It then proceeds to describe floating-point arithmetic,
which is what @command{awk} uses for all its computations, including a
discussion of arbitrary-precision floating-point arithmetic, which is
a feature available only in @command{gawk}. It continues on to present
arbitrary-precision integers, and concludes with a description of some
points where @command{gawk} and the POSIX standard are not quite in
agreement.
@quotation NOTE
Most users of @command{gawk} can safely skip this chapter.
But if you want to do scientific calculations with @command{gawk},
this is the place to be.
@end quotation
@menu
* Computer Arithmetic:: A quick intro to computer math.
* Math Definitions:: Defining terms used.
* MPFR features:: The MPFR features in @command{gawk}.
* FP Math Caution:: Things to know.
* Arbitrary Precision Integers:: Arbitrary Precision Integer Arithmetic with
@command{gawk}.
* Checking for MPFR:: How to check if MPFR is available.
* POSIX Floating Point Problems:: Standards Versus Existing Practice.
* Floating point summary:: Summary of floating point discussion.
@end menu
@node Computer Arithmetic
@section A General Description of Computer Arithmetic
Until now, we have worked with data as either numbers or
strings. Ultimately, however, computers represent everything in terms
of @dfn{binary digits}, or @dfn{bits}. A decimal digit can take on any
of 10 values: zero through nine. A binary digit can take on any of two
values, zero or one. Using binary, computers (and computer software)
can represent and manipulate numerical and character data. In general,
the more bits you can use to represent a particular thing, the greater
the range of possible values it can take on.
Modern computers support at least two, and often more, ways to do
arithmetic. Each kind of arithmetic uses a different representation
(organization of the bits) for the numbers. The kinds of arithmetic
that interest us are:
@table @asis
@item Decimal arithmetic
This is the kind of arithmetic you learned in elementary school, using
paper and pencil (and/or a calculator). In theory, numbers can have an
arbitrary number of digits on either side (or both sides) of the decimal
point, and the results of a computation are always exact.
Some modern systems can do decimal arithmetic in hardware, but usually you
need a special software library to provide access to these instructions.
There are also libraries that do decimal arithmetic entirely in software.
Despite the fact that some users expect @command{gawk} to be performing
decimal arithmetic,@footnote{We don't know why they expect this, but
they do.} it does not do so.
@item Integer arithmetic
In school, integer values were referred to as ``whole'' numbers---that
is, numbers without any fractional part, such as 1, 42, or @minus{}17.
The advantage to integer numbers is that they represent values exactly.
The disadvantage is that their range is limited.
@cindex unsigned integers
@cindex integers @subentry unsigned
In computers, integer values come in two flavors: @dfn{signed} and
@dfn{unsigned}. Signed values may be negative or positive, whereas
unsigned values are always greater than or equal
to zero.
In computer systems, integer arithmetic is exact, but the possible
range of values is limited. Integer arithmetic is generally faster than
floating-point arithmetic.
@cindex floating-point @subentry numbers
@item Floating-point arithmetic
Floating-point numbers represent what were called in school ``real''
numbers (i.e., those that have a fractional part, such as 3.1415927).
The advantage to floating-point numbers is that they can represent a
much larger range of values than can integers. The disadvantage is that
there are numbers that they cannot represent exactly.
Modern systems support floating-point arithmetic in hardware, with a
limited range of values. There are software libraries that allow
the use of arbitrary-precision floating-point calculations.
@cindex floating-point @subentry numbers @subentry single-precision
@cindex floating-point @subentry numbers @subentry double-precision
@cindex floating-point @subentry numbers @subentry arbitrary-precision
@cindex single-precision
@cindex double-precision
@cindex arbitrary precision
POSIX @command{awk} uses @dfn{double-precision} floating-point numbers, which
can hold more digits than @dfn{single-precision} floating-point numbers.
@command{gawk} has facilities for performing arbitrary-precision
floating-point arithmetic, which we describe in more detail shortly.
@end table
Computers work with integer and floating-point values of different
ranges. Integer values are usually either 32 or 64 bits in size.
Single-precision floating-point values occupy 32 bits, whereas double-precision
floating-point values occupy 64 bits.
(Quadruple-precision floating point values also exist. They occupy 128 bits,
but such numbers are not available in @command{awk}.)
Floating-point values are always
signed. The possible ranges of values are shown in @ref{table-numeric-ranges}
and @ref{table-floating-point-ranges}.
@float Table,table-numeric-ranges
@caption{Value ranges for integer representations}
@multitable @columnfractions .34 .33 .33
@headitem Representation @tab Minimum value @tab Maximum value
@item 32-bit signed integer @tab @minus{}2,147,483,648 @tab 2,147,483,647
@item 32-bit unsigned integer @tab 0 @tab 4,294,967,295
@item 64-bit signed integer @tab @minus{}9,223,372,036,854,775,808 @tab 9,223,372,036,854,775,807
@item 64-bit unsigned integer @tab 0 @tab 18,446,744,073,709,551,615
@end multitable
@end float
@float Table,table-floating-point-ranges
@caption{Approximate value ranges for floating-point number representations}
@multitable @columnfractions .38 .22 .22 .23
@iftex
@headitem Representation @tab @w{Minimum positive} @w{nonzero value} @tab Minimum @w{finite value} @tab Maximum @w{finite value}
@end iftex
@ifnottex
@headitem Representation @tab Minimum positive nonzero value @tab Minimum finite value @tab Maximum finite value
@end ifnottex
@iftex
@item @w{Single-precision floating-point} @tab @math{1.175494 @cdot 10^{-38}} @tab @math{-3.402823 @cdot 10^{38}} @tab @math{3.402823 @cdot 10^{38}}
@item @w{Double-precision floating-point} @tab @math{2.225074 @cdot 10^{-308}} @tab @math{-1.797693 @cdot 10^{308}} @tab @math{1.797693 @cdot 10^{308}}
@item @w{Quadruple-precision floating-point} @tab @math{3.362103 @cdot 10^{-4932}} @tab @math{-1.189731 @cdot 10^{4932}} @tab @math{1.189731 @cdot 10^{4932}}
@end iftex
@ifinfo
@item Single-precision floating-point @tab 1.175494e-38 @tab -3.402823e+38 @tab 3.402823e+38
@item Double-precision floating-point @tab 2.225074e-308 @tab -1.797693e+308 @tab 1.797693e+308
@item Quadruple-precision floating-point @tab 3.362103e-4932 @tab -1.189731e+4932 @tab 1.189731e+4932
@end ifinfo
@ifnottex
@ifnotinfo
@item Single-precision floating-point @tab 1.175494*10@sup{-38} @tab -3.402823*10@sup{38} @tab 3.402823*10@sup{38}
@item Double-precision floating-point @tab 2.225074*10@sup{-308} @tab -1.797693*10@sup{308} @tab 1.797693*10@sup{308}
@item Quadruple-precision floating-point @tab 3.362103*10@sup{-4932} @tab -1.189731*10@sup{4932} @tab 1.189731*10@sup{4932}
@end ifnotinfo
@end ifnottex
@end multitable
@end float
@node Math Definitions
@section Other Stuff to Know
The rest of this @value{CHAPTER} uses a number of terms. Here are some
informal definitions that should help you work your way through the material
here:
@table @dfn
@item Accuracy
A floating-point calculation's accuracy is how close it comes
to the real (paper and pencil) value.
@item Error
The difference between what the result of a computation ``should be''
and what it actually is. It is best to minimize error as much
as possible.
@item Exponent
The order of magnitude of a value;
some number of bits in a floating-point value store the exponent.
@item Inf
A special value representing infinity. Operations involving another
number and infinity produce infinity.
@item NaN
``Not a number.''@footnote{Thanks to Michael Brennan for this description,
which we have paraphrased, and for the examples.} A special value that
results from attempting a calculation that has no answer as a real number.
In such a case, programs can either receive a floating-point exception,
or get @code{NaN} back as the result. The IEEE 754 standard recommends
that systems return @code{NaN}. Some examples:
@table @code
@item sqrt(-1)
This makes sense in the range of complex numbers, but not in the
range of real numbers, so the result is @code{NaN}.
@item log(-8)
@minus{}8 is out of the domain of @code{log()}, so the result is @code{NaN}.
@end table
@item Normalized
How the significand (see later in this list) is usually stored. The
value is adjusted so that the first bit is one, and then that leading
one is assumed instead of physically stored. This provides one
extra bit of precision.
@item Precision
The number of bits used to represent a floating-point number.
The more bits, the more digits you can represent.
Binary and decimal precisions are related approximately, according to the
formula:
@display
@iftex
@math{prec = 3.322 @cdot dps}
@end iftex
@ifnottex
@ifnotdocbook
@var{prec} = 3.322 * @var{dps}
@end ifnotdocbook
@end ifnottex
@docbook
<emphasis>prec</emphasis> = 3.322 ⋅ <emphasis>dps</emphasis>
@end docbook
@end display
@noindent
Here, @emph{prec} denotes the binary precision
(measured in bits) and @emph{dps} (short for decimal places)
is the decimal digits.
@item Rounding mode
How numbers are rounded up or down when necessary.
More details are provided later.
@item Significand
A floating-point value consists of the significand multiplied by 10
to the power of the exponent. For example, in @code{1.2345e67},
the significand is @code{1.2345}.
@item Stability
From @uref{https://en.wikipedia.org/wiki/Numerical_stability,
the Wikipedia article on numerical stability}:
``Calculations that can be proven not to magnify approximation errors
are called @dfn{numerically stable}.''
@end table
See @uref{https://en.wikipedia.org/wiki/Accuracy_and_precision,
the Wikipedia article on accuracy and precision} for more information
on some of those terms.
On modern systems, floating-point hardware uses the representation and
operations defined by the IEEE 754 standard.
Three of the standard IEEE 754 types are 32-bit single precision,
64-bit double precision, and 128-bit quadruple precision.
The standard also specifies extended precision formats
to allow greater precisions and larger exponent ranges.
(@command{awk} uses only the 64-bit double-precision format.)
@ref{table-ieee-formats} lists the precision and exponent
field values for the basic IEEE 754 binary formats.
@float Table,table-ieee-formats
@caption{Basic IEEE format values}
@multitable @columnfractions .20 .20 .20 .20 .20
@headitem Name @tab Total bits @tab Precision @tab Minimum exponent @tab Maximum exponent
@item Single @tab 32 @tab 24 @tab @minus{}126 @tab +127
@item Double @tab 64 @tab 53 @tab @minus{}1022 @tab +1023
@item Quadruple @tab 128 @tab 113 @tab @minus{}16382 @tab +16383
@end multitable
@end float
@quotation NOTE
The precision numbers include the implied leading one that gives them
one extra bit of significand.
@end quotation
@node MPFR features
@section Arbitrary-Precision Arithmetic Features in @command{gawk}
By default, @command{gawk} uses the double-precision floating-point values
supplied by the hardware of the system it runs on. However, if it was
compiled to do so, and the @option{-M} command-line option is supplied,
@command{gawk} uses the @uref{http://www.mpfr.org,
GNU MPFR} and @uref{https://gmplib.org, GNU MP} (GMP) libraries for
arbitrary-precision arithmetic on numbers. You can see if MPFR support
is available like so:
@example
$ @kbd{gawk --version}
@print{} GNU Awk 4.1.2, API: 1.1 (GNU MPFR 3.1.0-p3, GNU MP 5.0.2)
@print{} Copyright (C) 1989, 1991-2015 Free Software Foundation.
@dots{}
@end example
@noindent
(You may see different version numbers than what's shown here. That's OK;
what's important is to see that GNU MPFR and GNU MP are listed in
the output.)
Additionally, there are a few elements available in the @code{PROCINFO}
array to provide information about the MPFR and GMP libraries
(@pxref{Auto-set}).
The MPFR library provides precise control over precisions and rounding
modes, and gives correctly rounded, reproducible, platform-independent
results. With the @option{-M} command-line option,
all floating-point arithmetic operators and numeric functions
can yield results to any desired precision level supported by MPFR.
Two predefined variables, @code{PREC} and @code{ROUNDMODE},
provide control over the working precision and the rounding mode.
The precision and the rounding mode are set globally for every operation
to follow.
@xref{Setting precision} and @ref{Setting the rounding mode}
for more information.
@node FP Math Caution
@section Floating-Point Arithmetic: Caveat Emptor!
@quotation
@i{Math class is tough!}
@author Teen Talk Barbie, July 1992
@end quotation
This @value{SECTION} provides a high-level overview of the issues
involved when doing lots of floating-point arithmetic.@footnote{There
is a very nice @uref{http://www.validlab.com/goldberg/paper.pdf,
paper on floating-point arithmetic} by David Goldberg, ``What Every
Computer Scientist Should Know About Floating-Point Arithmetic,''
@cite{ACM Computing Surveys} @strong{23}, 1 (1991-03): 5-48. This is
worth reading if you are interested in the details, but it does require
a background in computer science.}
The discussion applies to both hardware and arbitrary-precision
floating-point arithmetic.
@quotation CAUTION
The material here is purposely general. If you need to do serious
computer arithmetic, you should do some research first, and not
rely just on what we tell you.
@end quotation
@menu
* Inexactness of computations:: Floating point math is not exact.
* Getting Accuracy:: Getting more accuracy takes some work.
* Try To Round:: Add digits and round.
* Setting precision:: How to set the precision.
* Setting the rounding mode:: How to set the rounding mode.
@end menu
@node Inexactness of computations
@subsection Floating-Point Arithmetic Is Not Exact
Binary floating-point representations and arithmetic are inexact.
Simple values like 0.1 cannot be precisely represented using
binary floating-point numbers, and the limited precision of
floating-point numbers means that slight changes in
the order of operations or the precision of intermediate storage
can change the result. To make matters worse, with arbitrary-precision
floating-point arithmetic, you can set the precision before starting a
computation, but then you cannot be sure of the number of significant
decimal places in the final result.
@menu
* Inexact representation:: Numbers are not exactly represented.
* Comparing FP Values:: How to compare floating point values.
* Errors accumulate:: Errors get bigger as they go.
@end menu
@node Inexact representation
@subsubsection Many Numbers Cannot Be Represented Exactly
So, before you start to write any code, you should think
about what you really want and what's really happening. Consider the
two numbers in the following example:
@example
x = 0.875 # 1/2 + 1/4 + 1/8
y = 0.425
@end example
Unlike the number in @code{y}, the number stored in @code{x}
is exactly representable
in binary because it can be written as a finite sum of one or
more fractions whose denominators are all powers of two.
When @command{gawk} reads a floating-point number from
program source, it automatically rounds that number to whatever
precision your machine supports. If you try to print the numeric
content of a variable using an output format string of @code{"%.17g"},
it may not produce the same number as you assigned to it:
@example
$ @kbd{gawk 'BEGIN @{ x = 0.875; y = 0.425}
> @kbd{ printf("%0.17g, %0.17g\n", x, y) @}'}
@print{} 0.875, 0.42499999999999999
@end example
Often the error is so small you do not even notice it, and if you do,
you can always specify how much precision you would like in your output.
Usually this is a format string like @code{"%.15g"}, which, when
used in the previous example, produces an output identical to the input.
@node Comparing FP Values
@subsubsection Be Careful Comparing Values
Because the underlying representation can be a little bit off from the exact value,
comparing floating-point values to see if they are exactly equal is generally a bad idea.
Here is an example where it does not work like you would expect:
@example
$ @kbd{gawk 'BEGIN @{ print (0.1 + 12.2 == 12.3) @}'}
@print{} 0
@end example
The general wisdom when comparing floating-point values is to see if
they are within some small range of each other (called a @dfn{delta},
or @dfn{tolerance}).
You have to decide how small a delta is important to you. Code to do
this looks something like the following:
@example
@group
delta = 0.00001 # for example
difference = abs(a - b) # subtract the two values
if (difference < delta)
# all ok
else
# not ok
@end group
@end example
@noindent
(We assume that you have a simple absolute value function named
@code{abs()} defined elsewhere in your program.) If you write a
function to compare values with a delta, you should be sure
to use @samp{difference < abs(delta)} in case someone passes
in a negative delta value.
@node Errors accumulate
@subsubsection Errors Accumulate
The loss of accuracy during a single computation with floating-point
numbers usually isn't enough to worry about. However, if you compute a
value that is the result of a sequence of floating-point operations,
the error can accumulate and greatly affect the computation itself.
Here is an attempt to compute the value of @value{PI} using one of its
many series representations:
@example
BEGIN @{
x = 1.0 / sqrt(3.0)
n = 6
for (i = 1; i < 30; i++) @{
n = n * 2.0
x = (sqrt(x * x + 1) - 1) / x
printf("%.15f\n", n * x)
@}
@}
@end example
When run, the early errors propagate through later computations,
causing the loop to terminate prematurely after attempting to divide by zero:
@example
$ @kbd{gawk -f pi.awk}
@print{} 3.215390309173475
@print{} 3.159659942097510
@print{} 3.146086215131467
@print{} 3.142714599645573
@dots{}
@print{} 3.224515243534819
@print{} 2.791117213058638
@print{} 0.000000000000000
@error{} gawk: pi.awk:6: fatal: division by zero attempted
@end example
Here is an additional example where the inaccuracies in internal representations
yield an unexpected result:
@example
$ @kbd{gawk 'BEGIN @{}
> @kbd{for (d = 1.1; d <= 1.5; d += 0.1) # loop five times (?)}
> @kbd{i++}
> @kbd{print i}
> @kbd{@}'}
@print{} 4
@end example
@node Getting Accuracy
@subsection Getting the Accuracy You Need
Can arbitrary-precision arithmetic give exact results? There are
no easy answers. The standard rules of algebra often do not apply
when using floating-point arithmetic.
Among other things, the distributive and associative laws
do not hold completely, and order of operation may be important
for your computation. Rounding error, cumulative precision loss,
and underflow are often troublesome.
When @command{gawk} tests the expressions @samp{0.1 + 12.2} and
@samp{12.3} for equality using the machine double-precision arithmetic,
it decides that they are not equal! (@xref{Comparing FP Values}.)
You can get the result you want by increasing the precision; 56 bits in
this case does the job:
@example
$ @kbd{gawk -M -v PREC=56 'BEGIN @{ print (0.1 + 12.2 == 12.3) @}'}
@print{} 1
@end example
If adding more bits is good, perhaps adding even more bits of
precision is better?
Here is what happens if we use an even larger value of @code{PREC}:
@example
$ @kbd{gawk -M -v PREC=201 'BEGIN @{ print (0.1 + 12.2 == 12.3) @}'}
@print{} 0
@end example
This is not a bug in @command{gawk} or in the MPFR library.
It is easy to forget that the finite number of bits used to store the value
is often just an approximation after proper rounding.
The test for equality succeeds if and only if @emph{all} bits in the two operands
are exactly the same. Because this is not necessarily true after floating-point
computations with a particular precision and effective rounding mode,
a straight test for equality may not work. Instead, compare the
two numbers to see if they are within the desirable delta of each other.
In applications where 15 or fewer decimal places suffice,
hardware double-precision arithmetic can be adequate, and is usually much faster.
But you need to keep in mind that every floating-point operation
can suffer a new rounding error with catastrophic consequences, as illustrated
by our earlier attempt to compute the value of @value{PI}.
Extra precision can greatly enhance the stability and the accuracy
of your computation in such cases.
Additionally, you should understand that
repeated addition is not necessarily equivalent to multiplication
in floating-point arithmetic. In the example in
@ref{Errors accumulate}:
@example
$ @kbd{gawk 'BEGIN @{}
> @kbd{for (d = 1.1; d <= 1.5; d += 0.1) # loop five times (?)}
> @kbd{i++}
> @kbd{print i}
> @kbd{@}'}
@print{} 4
@end example
@noindent
you may or may not succeed in getting the correct result by choosing
an arbitrarily large value for @code{PREC}. Reformulation of
the problem at hand is often the correct approach in such situations.
@node Try To Round
@subsection Try a Few Extra Bits of Precision and Rounding
Instead of arbitrary-precision floating-point arithmetic,
often all you need is an adjustment of your logic
or a different order for the operations in your calculation.
The stability and the accuracy of the computation of @value{PI}
in the earlier example can be enhanced by using the following
simple algebraic transformation:
@example
(sqrt(x * x + 1) - 1) / x @equiv{} x / (sqrt(x * x + 1) + 1)
@end example
@noindent
After making this change, the program converges to
@value{PI} in under 30 iterations:
@example
$ @kbd{gawk -f pi2.awk}
@print{} 3.215390309173473
@print{} 3.159659942097501
@print{} 3.146086215131436
@print{} 3.142714599645370
@print{} 3.141873049979825
@dots{}
@print{} 3.141592653589797
@print{} 3.141592653589797
@end example
@node Setting precision
@subsection Setting the Precision
@command{gawk} uses a global working precision; it does not keep track of
the precision or accuracy of individual numbers. Performing an arithmetic
operation or calling a built-in function rounds the result to the current
working precision. The default working precision is 53 bits, which you can
modify using the predefined variable @code{PREC}. You can also set the
value to one of the predefined case-insensitive strings
shown in @ref{table-predefined-precision-strings},
to emulate an IEEE 754 binary format.
@float Table,table-predefined-precision-strings
@caption{Predefined precision strings for @code{PREC}}
@multitable {@code{"double"}} {12345678901234567890123456789012345}
@headitem @code{PREC} @tab IEEE 754 binary format
@item @code{"half"} @tab 16-bit half-precision
@item @code{"single"} @tab Basic 32-bit single precision
@item @code{"double"} @tab Basic 64-bit double precision
@item @code{"quad"} @tab Basic 128-bit quadruple precision
@item @code{"oct"} @tab 256-bit octuple precision
@end multitable
@end float
The following example illustrates the effects of changing precision
on arithmetic operations:
@example
$ @kbd{gawk -M -v PREC=100 'BEGIN @{ x = 1.0e-400; print x + 0}
> @kbd{PREC = "double"; print x + 0 @}'}
@print{} 1e-400
@print{} 0
@end example
@quotation CAUTION
Be wary of floating-point constants! When reading a floating-point
constant from program source code, @command{gawk} uses the default
precision (that of a C @code{double}), unless overridden by an assignment
to the special variable @code{PREC} on the command line, to store it
internally as an MPFR number. Changing the precision using @code{PREC}
in the program text does @emph{not} change the precision of a constant.
If you need to represent a floating-point constant at a higher precision
than the default and cannot use a command-line assignment to @code{PREC},
you should either specify the constant as a string, or as a rational
number, whenever possible. The following example illustrates the
differences among various ways to print a floating-point constant:
@example
$ @kbd{gawk -M 'BEGIN @{ PREC = 113; printf("%0.25f\n", 0.1) @}'}
@print{} 0.1000000000000000055511151
$ @kbd{gawk -M -v PREC=113 'BEGIN @{ printf("%0.25f\n", 0.1) @}'}
@print{} 0.1000000000000000000000000
$ @kbd{gawk -M 'BEGIN @{ PREC = 113; printf("%0.25f\n", "0.1") @}'}
@print{} 0.1000000000000000000000000
$ @kbd{gawk -M 'BEGIN @{ PREC = 113; printf("%0.25f\n", 1/10) @}'}
@print{} 0.1000000000000000000000000
@end example
@end quotation
@node Setting the rounding mode
@subsection Setting the Rounding Mode
@cindex @code{ROUNDMODE} variable
The @code{ROUNDMODE} variable provides
program-level control over the rounding mode.
The correspondence between @code{ROUNDMODE} and the IEEE
rounding modes is shown in @ref{table-gawk-rounding-modes}.
@float Table,table-gawk-rounding-modes
@caption{@command{gawk} rounding modes}
@multitable @columnfractions .45 .30 .25
@headitem Rounding mode @tab IEEE name @tab @code{ROUNDMODE}
@item Round to nearest, ties to even @tab @code{roundTiesToEven} @tab @code{"N"} or @code{"n"}
@item Round toward positive infinity @tab @code{roundTowardPositive} @tab @code{"U"} or @code{"u"}
@item Round toward negative infinity @tab @code{roundTowardNegative} @tab @code{"D"} or @code{"d"}
@item Round toward zero @tab @code{roundTowardZero} @tab @code{"Z"} or @code{"z"}
@item Round away from zero @tab @tab @code{"A"} or @code{"a"}
@end multitable
@end float
@code{ROUNDMODE} has the default value @code{"N"}, which
selects the IEEE 754 rounding mode @code{roundTiesToEven}.
In @ref{table-gawk-rounding-modes}, the value @code{"A"} selects
rounding away from zero. This is only available if your version of the
MPFR library supports it; otherwise, setting @code{ROUNDMODE} to @code{"A"}
has no effect.
The default mode @code{roundTiesToEven} is the most preferred,
but the least intuitive. This method does the obvious thing for most values,
by rounding them up or down to the nearest digit.
For example, rounding 1.132 to two digits yields 1.13,
and rounding 1.157 yields 1.16.
However, when it comes to rounding a value that is exactly halfway between,
things do not work the way you probably learned in school.
In this case, the number is rounded to the nearest even digit.
So rounding 0.125 to two digits rounds down to 0.12,
but rounding 0.6875 to three digits rounds up to 0.688.
You probably have already encountered this rounding mode when
using @code{printf} to format floating-point numbers.
For example:
@example
BEGIN @{
x = -4.5
for (i = 1; i < 10; i++) @{
x += 1.0
printf("%4.1f => %2.0f\n", x, x)
@}
@}
@end example
@noindent
produces the following output when run on the author's system:@footnote{It
is possible for the output to be completely different if the
C library in your system does not use the IEEE 754 even-rounding
rule to round halfway cases for @code{printf}.}
@example
-3.5 => -4
-2.5 => -2
-1.5 => -2
-0.5 => 0
0.5 => 0
1.5 => 2
2.5 => 2
3.5 => 4
4.5 => 4
@end example
The theory behind @code{roundTiesToEven} is that it more or less evenly
distributes upward and downward rounds of exact halves, which might
cause any accumulating round-off error to cancel itself out. This is the
default rounding mode for IEEE 754 computing functions and operators.
@c January 2018. Thanks to nethox@gmail.com for the example.
@cindex sidebar @subentry Rounding Modes and Conversion
@ifdocbook
@docbook
<sidebar><title>Rounding Modes and Conversion</title>
@end docbook
It's important to understand that, along with @code{CONVFMT} and
@code{OFMT}, the rounding mode affects how numbers are converted to strings.
For example, consider the following program:
@example
BEGIN @{
pi = 3.1416
OFMT = "%.f" # Print value as integer
print pi # ROUNDMODE = "N" by default.
ROUNDMODE = "U" # Now change ROUNDMODE
print pi
@}
@end example
@noindent
Running this program produces this output:
@example
$ @kbd{gawk -M -f roundmode.awk}
@print{} 3
@print{} 4
@end example
@docbook
</sidebar>
@end docbook
@end ifdocbook
@ifnotdocbook
@cartouche
@center @b{Rounding Modes and Conversion}
It's important to understand that, along with @code{CONVFMT} and
@code{OFMT}, the rounding mode affects how numbers are converted to strings.
For example, consider the following program:
@example
BEGIN @{
pi = 3.1416
OFMT = "%.f" # Print value as integer
print pi # ROUNDMODE = "N" by default.
ROUNDMODE = "U" # Now change ROUNDMODE
print pi
@}
@end example
@noindent
Running this program produces this output:
@example
$ @kbd{gawk -M -f roundmode.awk}
@print{} 3
@print{} 4
@end example
@end cartouche
@end ifnotdocbook
The other rounding modes are rarely used. Rounding toward positive infinity
(@code{roundTowardPositive}) and toward negative infinity
(@code{roundTowardNegative}) are often used to implement interval
arithmetic, where you adjust the rounding mode to calculate upper and
lower bounds for the range of output. The @code{roundTowardZero} mode can
be used for converting floating-point numbers to integers. When rounding
away from zero, the nearest number with magnitude greater than or equal to
the value is selected.
Some numerical analysts will tell you that your choice of rounding
style has tremendous impact on the final outcome, and advise you to
wait until final output for any rounding. Instead, you can often avoid
round-off error problems by setting the precision initially to some
value sufficiently larger than the final desired precision, so that
the accumulation of round-off error does not influence the outcome.
If you suspect that results from your computation are sensitive to
accumulation of round-off error, look for a significant difference in
output when you change the rounding mode to be sure.
@node Arbitrary Precision Integers
@section Arbitrary-Precision Integer Arithmetic with @command{gawk}
@cindex integers @subentry arbitrary precision
@cindex arbitrary precision @subentry integers
When given the @option{-M} option,
@command{gawk} performs all integer arithmetic using GMP arbitrary-precision
integers. Any number that looks like an integer in a source
or @value{DF} is stored as an arbitrary-precision integer. The size
of the integer is limited only by the available memory. For example,
the following computes
@iftex
@math{5^{4^{3^{2}}}},
@end iftex
@ifinfo
5^4^3^2,
@end ifinfo
@ifnottex
@ifnotinfo
5@sup{4@sup{3@sup{2}}},
@end ifnotinfo
@end ifnottex
the result of which is beyond the
limits of ordinary hardware double-precision floating-point values:
@example
$ @kbd{gawk -M 'BEGIN @{}
> @kbd{x = 5^4^3^2}
> @kbd{print "number of digits =", length(x)}
> @kbd{print substr(x, 1, 20), "...", substr(x, length(x) - 19, 20)}
> @kbd{@}'}
@print{} number of digits = 183231
@print{} 62060698786608744707 ... 92256259918212890625
@end example
If instead you were to compute the same value using arbitrary-precision
floating-point values, the precision needed for correct output (using
the formula
@iftex
@math{prec = 3.322 @cdot dps})
would be @math{3.322 @cdot 183231},
@end iftex
@ifnottex
@ifnotdocbook
@samp{prec = 3.322 * dps})
would be 3.322 x 183231,
@end ifnotdocbook
@end ifnottex
@docbook
<emphasis>prec</emphasis> = 3.322 ⋅ <emphasis>dps</emphasis>)
would be
<emphasis>prec</emphasis> = 3.322 ⋅ 183231,
@end docbook
or 608693.
The result from an arithmetic operation with an integer and a floating-point value
is a floating-point value with a precision equal to the working precision.
The following program calculates the eighth term in
Sylvester's sequence@footnote{Weisstein, Eric W.
@cite{Sylvester's Sequence}. From MathWorld---A Wolfram Web Resource
@w{(@url{http://mathworld.wolfram.com/SylvestersSequence.html}).}}
using a recurrence:
@example
$ @kbd{gawk -M 'BEGIN @{}
> @kbd{s = 2.0}
> @kbd{for (i = 1; i <= 7; i++)}
> @kbd{s = s * (s - 1) + 1}
> @kbd{print s}
> @kbd{@}'}
@print{} 113423713055421845118910464
@end example
The output differs from the actual number, 113,423,713,055,421,844,361,000,443,
because the default precision of 53 bits is not enough to represent the
floating-point results exactly. You can either increase the precision
(100 bits is enough in this case), or replace the floating-point constant
@samp{2.0} with an integer, to perform all computations using integer
arithmetic to get the correct output.
Sometimes @command{gawk} must implicitly convert an arbitrary-precision
integer into an arbitrary-precision floating-point value. This is
primarily because the MPFR library does not always provide the relevant
interface to process arbitrary-precision integers or mixed-mode numbers
as needed by an operation or function. In such a case, the precision is
set to the minimum value necessary for exact conversion, and the working
precision is not used for this purpose. If this is not what you need or
want, you can employ a subterfuge and convert the integer to floating
point first, like this:
@example
gawk -M 'BEGIN @{ n = 13; print (n + 0.0) % 2.0 @}'
@end example
You can avoid this issue altogether by specifying the number as a floating-point value
to begin with:
@example
gawk -M 'BEGIN @{ n = 13.0; print n % 2.0 @}'
@end example
Note that for this particular example, it is likely best
to just use the following:
@example
gawk -M 'BEGIN @{ n = 13; print n % 2 @}'
@end example
When dividing two arbitrary precision integers with either
@samp{/} or @samp{%}, the result is typically an arbitrary
precision floating point value (unless the denominator evenly
divides into the numerator).
@ifset INTDIV
In order to do integer division
or remainder with arbitrary precision integers, use the built-in
@code{intdiv0()} function (@pxref{Numeric Functions}).
You can simulate the @code{intdiv0()} function in standard @command{awk}
using this user-defined function:
@example
@c file eg/lib/intdiv0.awk
# intdiv0 --- do integer division
@c endfile
@ignore
@c file eg/lib/intdiv0.awk
#
# Arnold Robbins, arnold@@skeeve.com, Public Domain
# July, 2014
#
# Name changed from div() to intdiv()
# April, 2015
#
# Changed to intdiv0()
# April, 2016
@c endfile
@end ignore
@c file eg/lib/intdiv0.awk
function intdiv0(numerator, denominator, result)
@{
split("", result)
numerator = int(numerator)
denominator = int(denominator)
result["quotient"] = int(numerator / denominator)
result["remainder"] = int(numerator % denominator)
return 0.0
@}
@c endfile
@end example
The following example program, contributed by Katie Wasserman,
uses @code{intdiv0()} to
compute the digits of @value{PI} to as many places as you
choose to set:
@example
@c file eg/prog/pi.awk
@group
# pi.awk --- compute the digits of pi
@c endfile
@c endfile
@ignore
@c file eg/prog/pi.awk
#
# Katie Wasserman, katie@@wass.net
# August 2014
@c endfile
@end ignore
@c file eg/prog/pi.awk
BEGIN @{
digits = 100000
two = 2 * 10 ^ digits
@end group
pi = two
for (m = digits * 4; m > 0; --m) @{
d = m * 2 + 1
x = pi * m
intdiv0(x, d, result)
pi = result["quotient"]
pi = pi + two
@}
print pi
@}
@c endfile
@end example
@ignore
Date: Wed, 20 Aug 2014 10:19:11 -0400
To: arnold@skeeve.com
From: Katherine Wasserman <katie@wass.net>
Subject: Re: computation of digits of pi?
Arnold,
>The program that you sent to compute the digits of pi using div(). Is
>that some standard algorithm that every math student knows? If so,
>what's it called?
It's not that well known but it's not that obscure either
It's Euler's modification to Newton's method for calculating pi.
Take a look at lines (23) - (25) here: http://mathworld.wolfram.com/PiFormulas.htm
The algorithm I wrote simply expands the multiply by 2 and works from the innermost expression outwards. I used this to program HP calculators because it's quite easy to modify for tiny memory devices with smallish word sizes.
http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/articles.cgi?read=899
-Katie
@end ignore
When asked about the algorithm used, Katie replied:
@quotation
It's not that well known but it's not that obscure either.
It's Euler's modification to Newton's method for calculating pi.
Take a look at lines (23) - (25) here: @uref{http://mathworld.wolfram.com/PiFormulas.html}.
The algorithm I wrote simply expands the multiply by 2 and works from
the innermost expression outwards. I used this to program HP calculators
because it's quite easy to modify for tiny memory devices with smallish
word sizes. See
@uref{http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/articles.cgi?read=899}.
@end quotation
@end ifset
@node Checking for MPFR
@section How To Check If MPFR Is Available
@cindex checking for MPFR
@cindex MPFR, checking for
Occasionally, you might like to be able to check if @command{gawk}
was invoked with the @option{-M} option, enabling arbitrary-precision
arithmetic. You can do so with the following function, contributed
by Andrew Schorr:
@example
@c file eg/lib/have_mpfr.awk
# adequate_math_precision --- return true if we have enough bits
@c endfile
@ignore
@c file eg/lib/have_mpfr.awk
#
# Andrew Schorr, aschorr@@telemetry-investments.com, Public Domain
# May 2017
@c endfile
@end ignore
@c file eg/lib/have_mpfr.awk
function adequate_math_precision(n)
@{
return (1 != (1+(1/(2^(n-1)))))
@}
@c endfile
@end example
Here is code that invokes the function in order to check
if arbitrary-precision arithmetic is available:
@example
BEGIN @{
# How many bits of mantissa precision are required
# for this program to function properly?
fpbits = 123
# We hope that we were invoked with MPFR enabled. If so, the
# following statement should configure calculations to our desired
# precision.
PREC = fpbits
if (! adequate_math_precision(fpbits)) @{
print("Error: insufficient computation precision available.\n" \
"Try again with the -M argument?") > "/dev/stderr"
# Note: you may need to set a flag here to bail out of END rules
exit 1
@}
@}
@end example
Please be aware that @code{exit} will jump to the @code{END} rules, if present (@pxref{Exit Statement}).
@node POSIX Floating Point Problems
@section Standards Versus Existing Practice
Historically, @command{awk} has converted any nonnumeric-looking string
to the numeric value zero, when required. Furthermore, the original
definition of the language and the original POSIX standards specified that
@command{awk} only understands decimal numbers (base 10), and not octal
(base 8) or hexadecimal numbers (base 16).
Changes in the language of the
2001 and 2004 POSIX standards can be interpreted to imply that @command{awk}
should support additional features. These features are:
@itemize @value{BULLET}
@item
Interpretation of floating-point data values specified in hexadecimal
notation (e.g., @code{0xDEADBEEF}). (Note: data values, @emph{not}
source code constants.)
@item
Support for the special IEEE 754 floating-point values ``not a number''
(NaN), positive infinity (``inf''), and negative infinity (``@minus{}inf'').
In particular, the format for these values is as specified by the ISO 1999
C standard, which ignores case and can allow implementation-dependent additional
characters after the @samp{nan} and allow either @samp{inf} or @samp{infinity}.
@end itemize
The first problem is that both of these are clear changes to historical
practice:
@itemize @value{BULLET}
@item
The @command{gawk} maintainer feels that supporting hexadecimal
floating-point values, in particular, is ugly, and was never intended by the
original designers to be part of the language.
@item
Allowing completely alphabetic strings to have valid numeric
values is also a very severe departure from historical practice.
@end itemize
The second problem is that the @command{gawk} maintainer feels that this
interpretation of the standard, which required a certain amount of
``language lawyering'' to arrive at in the first place, was not even
intended by the standard developers. In other words, ``We see how you
got where you are, but we don't think that that's where you want to be.''
Recognizing these issues, but attempting to provide compatibility
with the earlier versions of the standard,
the 2008 POSIX standard added explicit wording to allow, but not require,
that @command{awk} support hexadecimal floating-point values and
special values for ``not a number'' and infinity.
Although the @command{gawk} maintainer continues to feel that
providing those features is inadvisable,
nevertheless, on systems that support IEEE floating point, it seems
reasonable to provide @emph{some} way to support NaN and infinity values.
The solution implemented in @command{gawk} is as follows:
@itemize @value{BULLET}
@item
With the @option{--posix} command-line option, @command{gawk} becomes
``hands off.'' String values are passed directly to the system library's
@code{strtod()} function, and if it successfully returns a numeric value,
that is what's used.@footnote{You asked for it, you got it.}
By definition, the results are not portable across
different systems. They are also a little surprising:
@example
$ @kbd{echo nanny | gawk --posix '@{ print $1 + 0 @}'}
@print{} nan
$ @kbd{echo 0xDeadBeef | gawk --posix '@{ print $1 + 0 @}'}
@print{} 3735928559
@end example
@item
Without @option{--posix}, @command{gawk} interprets the four string values
@samp{+inf},
@samp{-inf},
@samp{+nan},
and
@samp{-nan}
specially, producing the corresponding special numeric values.
The leading sign acts a signal to @command{gawk} (and the user)
that the value is really numeric. Hexadecimal floating point is
not supported (unless you also use @option{--non-decimal-data},
which is @emph{not} recommended). For example:
@example
$ @kbd{echo nanny | gawk '@{ print $1 + 0 @}'}
@print{} 0
$ @kbd{echo +nan | gawk '@{ print $1 + 0 @}'}
@print{} +nan
$ @kbd{echo 0xDeadBeef | gawk '@{ print $1 + 0 @}'}
@print{} 0
@end example
@command{gawk} ignores case in the four special values.
Thus, @samp{+nan} and @samp{+NaN} are the same.
@end itemize
@cindex POSIX mode
Besides handling input, @command{gawk} also needs to print ``correct'' values on
output when a value is either NaN or infinity. Starting with @value{PVERSION}
4.2.2, for such values @command{gawk} prints one of the four strings
just described: @samp{+inf}, @samp{-inf}, @samp{+nan}, or @samp{-nan}.
Similarly, in POSIX mode, @command{gawk} prints the result of
the system's C @code{printf()} function using the @code{%g} format string
for the value, whatever that may be.
@node Floating point summary
@section Summary
@itemize @value{BULLET}
@item
Most computer arithmetic is done using either integers or floating-point
values. Standard @command{awk} uses double-precision
floating-point values.
@item
In the early 1990s Barbie mistakenly said, ``Math class is tough!''
Although math isn't tough, floating-point arithmetic isn't the same
as pencil-and-paper math, and care must be taken:
@c nested list
@itemize @value{MINUS}
@item
Not all numbers can be represented exactly.
@item
Comparing values should use a delta, instead of being done directly
with @samp{==} and @samp{!=}.
@item
Errors accumulate.
@item
Operations are not always truly associative or distributive.
@end itemize
@item
Increasing the accuracy can help, but it is not a panacea.
@item
Often, increasing the accuracy and then rounding to the desired
number of digits produces reasonable results.
@item
Use @option{-M} (or @option{--bignum}) to enable MPFR
arithmetic. Use @code{PREC} to set the precision in bits, and
@code{ROUNDMODE} to set the IEEE 754 rounding mode.
@item
With @option{-M}, @command{gawk} performs
arbitrary-precision integer arithmetic using the GMP library.
This is faster and more space-efficient than using MPFR for
the same calculations.
@item
There are several areas with respect to floating-point
numbers where @command{gawk} disagrees with the POSIX standard.
It pays to be aware of them.
@item
Overall, there is no need to be unduly suspicious about the results from
floating-point arithmetic. The lesson to remember is that floating-point
arithmetic is always more complex than arithmetic using pencil and
paper. In order to take advantage of the power of floating-point arithmetic,
you need to know its limitations and work within them. For most casual
use of floating-point arithmetic, you will often get the expected result
if you simply round the display of your final results to the correct number
of significant decimal digits.
@item
As general advice, avoid presenting numerical data in a manner that
implies better precision than is actually the case.
@end itemize
@node Dynamic Extensions
@chapter Writing Extensions for @command{gawk}
@cindex dynamically loaded extensions
It is possible to add new functions written in C or C++ to @command{gawk} using
dynamically loaded libraries. This facility is available on systems
that support the C @code{dlopen()} and @code{dlsym()}
functions. This @value{CHAPTER} describes how to create extensions
using code written in C or C++.
If you don't know anything about C programming, you can safely skip this
@value{CHAPTER}, although you may wish to review the documentation on the
extensions that come with @command{gawk} (@pxref{Extension Samples}),
and the information on the @code{gawkextlib} project (@pxref{gawkextlib}).
The sample extensions are automatically built and installed when
@command{gawk} is.
@quotation NOTE
When @option{--sandbox} is specified, extensions are disabled
(@pxref{Options}).
@end quotation
@menu
* Extension Intro:: What is an extension.
* Plugin License:: A note about licensing.
* Extension Mechanism Outline:: An outline of how it works.
* Extension API Description:: A full description of the API.
* Finding Extensions:: How @command{gawk} finds compiled extensions.
* Extension Example:: Example C code for an extension.
* Extension Samples:: The sample extensions that ship with
@command{gawk}.
* gawkextlib:: The @code{gawkextlib} project.
* Extension summary:: Extension summary.
* Extension Exercises:: Exercises.
@end menu
@node Extension Intro
@section Introduction
@cindex plug-in
An @dfn{extension} (sometimes called a @dfn{plug-in}) is a piece of
external compiled code that @command{gawk} can load at runtime to
provide additional functionality, over and above the built-in capabilities
described in the rest of this @value{DOCUMENT}.
Extensions are useful because they allow you (of course) to extend
@command{gawk}'s functionality. For example, they can provide access to
system calls (such as @code{chdir()} to change directory) and to other
C library routines that could be of use. As with most software,
``the sky is the limit''; if you can imagine something that you might
want to do and can write in C or C++, you can write an extension to do it!
Extensions are written in C or C++, using the @dfn{application programming
interface} (API) defined for this purpose by the @command{gawk}
developers. The rest of this @value{CHAPTER} explains
the facilities that the API provides and how to use
them, and presents a small example extension. In addition, it documents
the sample extensions included in the @command{gawk} distribution
and describes the @code{gawkextlib} project.
@ifclear FOR_PRINT
@xref{Extension Design}, for a discussion of the extension mechanism
goals and design.
@end ifclear
@ifset FOR_PRINT
See @uref{https://www.gnu.org/software/gawk/manual/html_node/Extension-Design.html}
for a discussion of the extension mechanism
goals and design.
@end ifset
@node Plugin License
@section Extension Licensing
Every dynamic extension must be distributed under a license that is
compatible with the GNU GPL (@pxref{Copying}).
In order for the extension to tell @command{gawk} that it is
properly licensed, the extension must define the global symbol
@code{plugin_is_GPL_compatible}. If this symbol does not exist,
@command{gawk} emits a fatal error and exits when it tries to load
your extension.
The declared type of the symbol should be @code{int}. It does not need
to be in any allocated section, though. The code merely asserts that
the symbol exists in the global scope. Something like this is enough:
@example
int plugin_is_GPL_compatible;
@end example
@node Extension Mechanism Outline
@section How It Works at a High Level
Communication between
@command{gawk} and an extension is two-way. First, when an extension
is loaded, @command{gawk} passes it a pointer to a @code{struct} whose fields are
function pointers.
@ifnotdocbook
This is shown in @ref{figure-load-extension}.
@end ifnotdocbook
@ifdocbook
This is shown in @inlineraw{docbook, <xref linkend="figure-load-extension"/>}.
@end ifdocbook
@ifnotdocbook
@float Figure,figure-load-extension
@caption{Loading the extension}
@center @image{gawk_api-figure1, , , Loading the extension}
@end float
@end ifnotdocbook
@docbook
<figure id="figure-load-extension" float="0">
<title>Loading the extension</title>
<mediaobject>
<imageobject role="web"><imagedata fileref="gawk_api-figure1.png" format="PNG"/></imageobject>
</mediaobject>
</figure>
@end docbook
The extension can call functions inside @command{gawk} through these
function pointers, at runtime, without needing (link-time) access
to @command{gawk}'s symbols. One of these function pointers is to a
function for ``registering'' new functions.
@ifnotdocbook
This is shown in @ref{figure-register-new-function}.
@end ifnotdocbook
@ifdocbook
This is shown in @inlineraw{docbook, <xref linkend="figure-register-new-function"/>}.
@end ifdocbook
@ifnotdocbook
@float Figure,figure-register-new-function
@caption{Registering a new function}
@center @image{gawk_api-figure2, , , Registering a new Function}
@end float
@end ifnotdocbook
@docbook
<figure id="figure-register-new-function" float="0">
<title>Registering a new function</title>
<mediaobject>
<imageobject role="web"><imagedata fileref="gawk_api-figure2.png" format="PNG"/></imageobject>
</mediaobject>
</figure>
@end docbook
In the other direction, the extension registers its new functions
with @command{gawk} by passing function pointers to the functions that
provide the new feature (@code{do_chdir()}, for example). @command{gawk}
associates the function pointer with a name and can then call it, using a
defined calling convention.
@ifnotdocbook
This is shown in @ref{figure-call-new-function}.
@end ifnotdocbook
@ifdocbook
This is shown in @inlineraw{docbook, <xref linkend="figure-call-new-function"/>}.
@end ifdocbook
@ifnotdocbook
@float Figure,figure-call-new-function
@caption{Calling the new function}
@center @image{gawk_api-figure3, , , Calling the new function}
@end float
@end ifnotdocbook
@docbook
<figure id="figure-call-new-function" float="0">
<title>Calling the new function</title>
<mediaobject>
<imageobject role="web"><imagedata fileref="gawk_api-figure3.png" format="PNG"/></imageobject>
</mediaobject>
</figure>
@end docbook
The @code{do_@var{xxx}()} function, in turn, then uses the function
pointers in the API @code{struct} to do its work, such as updating
variables or arrays, printing messages, setting @code{ERRNO}, and so on.
Convenience macros make calling through the function pointers look
like regular function calls so that extension code is quite readable
and understandable.
Although all of this sounds somewhat complicated, the result is that
extension code is quite straightforward to write and to read. You can
see this in the sample extension @file{filefuncs.c} (@pxref{Extension
Example}) and also in the @file{testext.c} code for testing the APIs.
Some other bits and pieces:
@itemize @value{BULLET}
@item
The API provides access to @command{gawk}'s @code{do_@var{xxx}} values,
reflecting command-line options, like @code{do_lint}, @code{do_profiling},
and so on (@pxref{Extension API Variables}).
These are informational: an extension cannot affect their values
inside @command{gawk}. In addition, attempting to assign to them
produces a compile-time error.
@item
The API also provides major and minor version numbers, so that an
extension can check if the @command{gawk} it is loaded with supports the
facilities it was compiled with. (Version mismatches ``shouldn't''
happen, but we all know how @emph{that} goes.)
@xref{Extension Versioning} for details.
@end itemize
@node Extension API Description
@section API Description
@cindex extension API
C or C++ code for an extension must include the header file
@file{gawkapi.h}, which declares the functions and defines the data
types used to communicate with @command{gawk}.
This (rather large) @value{SECTION} describes the API in detail.
@menu
* Extension API Functions Introduction:: Introduction to the API functions.
* General Data Types:: The data types.
* Memory Allocation Functions:: Functions for allocating memory.
* Constructor Functions:: Functions for creating values.
* Registration Functions:: Functions to register things with
@command{gawk}.
* Printing Messages:: Functions for printing messages.
* Updating @code{ERRNO}:: Functions for updating @code{ERRNO}.
* Requesting Values:: How to get a value.
* Accessing Parameters:: Functions for accessing parameters.
* Symbol Table Access:: Functions for accessing global
variables.
* Array Manipulation:: Functions for working with arrays.
* Redirection API:: How to access and manipulate
redirections.
* Extension API Variables:: Variables provided by the API.
* Extension API Boilerplate:: Boilerplate code for using the API.
* Changes from API V1:: Changes from V1 of the API.
@end menu
@node Extension API Functions Introduction
@subsection Introduction
Access to facilities within @command{gawk} is achieved
by calling through function pointers passed into your extension.
API function pointers are provided for the following kinds of operations:
@itemize @value{BULLET}
@item
Allocating, reallocating, and releasing memory.
@item
Registration functions. You may register:
@c nested list
@itemize @value{MINUS}
@item
Extension functions
@item
Exit callbacks
@item
A version string
@item
Input parsers
@item
Output wrappers
@item
Two-way processors
@end itemize
All of these are discussed in detail later in this @value{CHAPTER}.
@item
Printing fatal, warning, and ``lint'' warning messages.
@item
Updating @code{ERRNO}, or unsetting it.
@item
Accessing parameters, including converting an undefined parameter into
an array.
@item
Symbol table access: retrieving a global variable, creating one,
or changing one.
@item
Creating and releasing cached values; this provides an
efficient way to use values for multiple variables and
can be a big performance win.
@item
Manipulating arrays:
@itemize @value{MINUS}
@item
Retrieving, adding, deleting, and modifying elements
@item
Getting the count of elements in an array
@item
Creating a new array
@item
Clearing an array
@item
Flattening an array for easy C-style looping over all its indices and elements
@end itemize
@item
Accessing and manipulating redirections.
@end itemize
Some points about using the API:
@itemize @value{BULLET}
@item
The following types, macros, and/or functions are referenced
in @file{gawkapi.h}. For correct use, you must therefore include the
corresponding standard header file @emph{before} including @file{gawkapi.h}.
The list of macros and related header files is shown in @ref{table-api-std-headers}.
@float Table,table-api-std-headers
@caption{Standard header files needed by API}
@multitable {@code{memset()}, @code{memcpy()}} {@code{<sys/types.h>}}
@headitem C entity @tab Header file
@item @code{EOF} @tab @code{<stdio.h>}
@item Values for @code{errno} @tab @code{<errno.h>}
@item @code{FILE} @tab @code{<stdio.h>}
@item @code{NULL} @tab @code{<stddef.h>}
@item @code{memcpy()} @tab @code{<string.h>}
@item @code{memset()} @tab @code{<string.h>}
@item @code{size_t} @tab @code{<sys/types.h>}
@item @code{struct stat} @tab @code{<sys/stat.h>}
@end multitable
@end float
Due to portability concerns, especially to systems that are not
fully standards-compliant, it is your responsibility
to include the correct files in the correct way. This requirement
is necessary in order to keep @file{gawkapi.h} clean, instead of becoming
a portability hodge-podge as can be seen in some parts of
the @command{gawk} source code.
@item
If your extension uses MPFR facilities, and you wish to receive such
values from @command{gawk} and/or pass such values to it, you must include the
@code{<mpfr.h>} header before including @code{<gawkapi.h>}.
@item
The @file{gawkapi.h} file may be included more than once without ill effect.
Doing so, however, is poor coding practice.
@item
Although the API only uses ISO C 90 features, there is an exception; the
``constructor'' functions use the @code{inline} keyword. If your compiler
does not support this keyword, you should either place
@samp{-Dinline=''} on your command line or use the GNU Autotools and include a
@file{config.h} file in your extensions.
@item
All pointers filled in by @command{gawk} point to memory
managed by @command{gawk} and should be treated by the extension as
read-only. Memory for @emph{all} strings passed into @command{gawk}
from the extension @emph{must} come from calling one of
@code{gawk_malloc()}, @code{gawk_calloc()}, or @code{gawk_realloc()},
and is managed by @command{gawk} from then on.
@item
The API defines several simple @code{struct}s that map values as seen
from @command{awk}. A value can be a @code{double}, a string, or an
array (as in multidimensional arrays, or when creating a new array).
String values maintain both pointer and length, because embedded @sc{nul}
characters are allowed.
@quotation NOTE
By intent, @command{gawk} maintains strings using the current multibyte
encoding (as defined by @env{LC_@var{xxx}} environment variables)
and not using wide characters. This matches how @command{gawk} stores
strings internally and also how characters are likely to be input into
and output from files.
@end quotation
@quotation NOTE
String values passed to an extension by @command{gawk} are always
@sc{nul}-terminated. Thus it is safe to pass such string values to
standard library and system routines. However, because @command{gawk}
allows embedded @sc{nul} characters in string data, before using the data
as a regular C string, you should check that the length for that string
passed to the extension matches the return value of @code{strlen()}
for it.
@end quotation
@item
When retrieving a value (such as a parameter or that of a global variable
or array element), the extension requests a specific type (number, string,
scalar, value cookie, array, or ``undefined''). When the request is
``undefined,'' the returned value will have the real underlying type.
However, if the request and actual type don't match, the access function
returns ``false'' and fills in the type of the actual value that is there,
so that the extension can, e.g., print an error message
(such as ``scalar passed where array expected'').
@c This is documented in the header file and needs some expanding upon.
@c The table there should be presented here
@end itemize
You may call the API functions by using the function pointers
directly, but the interface is not so pretty. To make extension code look
more like regular code, the @file{gawkapi.h} header file defines several
macros that you should use in your code. This @value{SECTION} presents
the macros as if they were functions.
@node General Data Types
@subsection General-Purpose Data Types
@cindex Robbins @subentry Arnold
@cindex Ramey, Chet
@quotation
@i{I have a true love/hate relationship with unions.}
@author Arnold Robbins
@end quotation
@quotation
@i{That's the thing about unions: the compiler will arrange things so they
can accommodate both love and hate.}
@author Chet Ramey
@end quotation
The extension API defines a number of simple types and structures for
general-purpose use. Additional, more specialized, data structures are
introduced in subsequent @value{SECTION}s, together with the functions
that use them.
The general-purpose types and structures are as follows:
@table @code
@item typedef void *awk_ext_id_t;
A value of this type is received from @command{gawk} when an extension is loaded.
That value must then be passed back to @command{gawk} as the first parameter of
each API function.
@item #define awk_const @dots{}
This macro expands to @samp{const} when compiling an extension,
and to nothing when compiling @command{gawk} itself. This makes
certain fields in the API data structures unwritable from extension code,
while allowing @command{gawk} to use them as it needs to.
@item typedef enum awk_bool @{
@itemx @ @ @ @ awk_false = 0,
@itemx @ @ @ @ awk_true
@itemx @} awk_bool_t;
A simple Boolean type.
@item typedef struct awk_string @{
@itemx @ @ @ @ char *str;@ @ @ @ @ @ /* data */
@itemx @ @ @ @ size_t len;@ @ @ @ @ /* length thereof, in chars */
@itemx @} awk_string_t;
This represents a mutable string. @command{gawk}
owns the memory pointed to if it supplied
the value. Otherwise, it takes ownership of the memory pointed to.
@emph{Such memory must come from calling one of the
@code{gawk_malloc()}, @code{gawk_calloc()}, or
@code{gawk_realloc()} functions!}
As mentioned earlier, strings are maintained using the current
multibyte encoding.
@item typedef enum @{
@itemx @ @ @ @ AWK_UNDEFINED,
@itemx @ @ @ @ AWK_NUMBER,
@itemx @ @ @ @ AWK_STRING,
@itemx @ @ @ @ AWK_REGEX,
@itemx @ @ @ @ AWK_STRNUM,
@itemx @ @ @ @ AWK_ARRAY,
@itemx @ @ @ @ AWK_SCALAR,@ @ @ @ @ @ @ @ @ /* opaque access to a variable */
@itemx @ @ @ @ AWK_VALUE_COOKIE@ @ @ @ /* for updating a previously created value */
@itemx @} awk_valtype_t;
This @code{enum} indicates the type of a value.
It is used in the following @code{struct}.
@item typedef struct awk_value @{
@itemx @ @ @ @ awk_valtype_t val_type;
@itemx @ @ @ @ union @{
@itemx @ @ @ @ @ @ @ @ awk_string_t@ @ @ @ @ @ @ s;
@itemx @ @ @ @ @ @ @ @ awknum_t@ @ @ @ @ @ @ @ @ @ @ n;
@itemx @ @ @ @ @ @ @ @ awk_array_t@ @ @ @ @ @ @ @ a;
@itemx @ @ @ @ @ @ @ @ awk_scalar_t@ @ @ @ @ @ @ scl;
@itemx @ @ @ @ @ @ @ @ awk_value_cookie_t@ vc;
@itemx @ @ @ @ @} u;
@itemx @} awk_value_t;
An ``@command{awk} value.''
The @code{val_type} member indicates what kind of value the
@code{union} holds, and each member is of the appropriate type.
@item #define str_value@ @ @ @ @ @ u.s
@itemx #define strnum_value@ @ @ str_value
@itemx #define regex_value@ @ @ @ str_value
@itemx #define num_value@ @ @ @ @ @ u.n.d
@itemx #define num_type@ @ @ @ @ @ @ u.n.type
@itemx #define num_ptr@ @ @ @ @ @ @ @ u.n.ptr
@itemx #define array_cookie@ @ @ u.a
@itemx #define scalar_cookie@ @ u.scl
@itemx #define value_cookie@ @ @ u.vc
Using these macros makes accessing the fields of the @code{awk_value_t} more
readable.
@item enum AWK_NUMBER_TYPE @{
@itemx @ @ @ @ AWK_NUMBER_TYPE_DOUBLE,
@itemx @ @ @ @ AWK_NUMBER_TYPE_MPFR,
@itemx @ @ @ @ AWK_NUMBER_TYPE_MPZ
@itemx @};
This @code{enum} is used in the following structure for defining the
type of numeric value that is being worked with. It is declared at the
top level of the file so that it works correctly for C++ as well as for C.
@item typedef struct awk_number @{
@itemx @ @ @ @ double d;
@itemx @ @ @ @ enum AWK_NUMBER_TYPE type;
@itemx @ @ @ @ void *ptr;
@itemx @} awk_number_t;
This represents a numeric value. Internally, @command{gawk} stores
every number as either a C @code{double}, a GMP integer, or an MPFR
arbitrary-precision floating-point value. In order to allow extensions
to also support GMP and MPFR values, numeric values are passed in this
structure.
The double-precision @code{d} element is always populated
in data received from @command{gawk}. In addition, by examining the
@code{type} member, an extension can determine if the @code{ptr}
member is either a GMP integer (type @code{mpz_ptr}), or an MPFR
floating-point value (type @code{mpfr_ptr_t}), and cast it appropriately.
@item typedef void *awk_scalar_t;
Scalars can be represented as an opaque type. These values are obtained
from @command{gawk} and then passed back into it. This is discussed
in a general fashion in the text following this list, and in more detail in
@ref{Symbol table by cookie}.
@item typedef void *awk_value_cookie_t;
A ``value cookie'' is an opaque type representing a cached value.
This is also discussed in a general fashion in the text following this list,
and in more detail in @ref{Cached values}.
@end table
Scalar values in @command{awk} are numbers, strings, strnums, or typed regexps. The
@code{awk_value_t} struct represents values. The @code{val_type} member
indicates what is in the @code{union}.
Representing numbers is easy---the API uses a C @code{double}. Strings
require more work. Because @command{gawk} allows embedded @sc{nul} bytes
in string values, a string must be represented as a pair containing a
data pointer and length. This is the @code{awk_string_t} type.
A strnum (numeric string) value is represented as a string and consists
of user input data that appears to be numeric.
When an extension creates a strnum value, the result is a string flagged
as user input. Subsequent parsing by @command{gawk} then determines whether it
looks like a number and should be treated as a strnum, or as a regular string.
This is useful in cases where an extension function would like to do something
comparable to the @code{split()} function which sets the strnum attribute
on the array elements it creates. For example, an extension that implements
CSV splitting would want to use this feature. This is also useful for a
function that retrieves a data item from a database. The PostgreSQL
@code{PQgetvalue()} function, for example, returns a string that may be numeric
or textual depending on the contents.
Typed regexp values (@pxref{Strong Regexp Constants}) are not of
much use to extension functions. Extension functions can tell that
they've received them, and create them for scalar values. Otherwise,
they can examine the text of the regexp through @code{regex_value.str}
and @code{regex_value.len}.
Identifiers (i.e., the names of global variables) can be associated
with either scalar values or with arrays. In addition, @command{gawk}
provides true arrays of arrays, where any given array element can
itself be an array. Discussion of arrays is delayed until
@ref{Array Manipulation}.
The various macros listed earlier make it easier to use the elements
of the @code{union} as if they were fields in a @code{struct}; this
is a common coding practice in C. Such code is easier to write and to
read, but it remains @emph{your} responsibility to make sure that
the @code{val_type} member correctly reflects the type of the value in
the @code{awk_value_t} struct.
Conceptually, the first three members of the @code{union} (number, string,
and array) are all that is needed for working with @command{awk} values.
However, because the API provides routines for accessing and changing
the value of a global scalar variable only by using the variable's name,
there is a performance penalty: @command{gawk} must find the variable
each time it is accessed and changed. This turns out to be a real issue,
not just a theoretical one.
Thus, if you know that your extension will spend considerable time
reading and/or changing the value of one or more scalar variables, you
can obtain a @dfn{scalar cookie}@footnote{See
@uref{http://catb.org/jargon/html/C/cookie.html, the ``cookie'' entry in the Jargon file} for a
definition of @dfn{cookie}, and @uref{http://catb.org/jargon/html/M/magic-cookie.html,
the ``magic cookie'' entry in the Jargon file} for a nice example.
@ifclear FOR_PRINT
See also the entry for ``Cookie'' in the @ref{Glossary}.
@end ifclear
}
object for that variable, and then use
the cookie for getting the variable's value or for changing the variable's
value.
The @code{awk_scalar_t} type holds a scalar cookie, and the
@code{scalar_cookie} macro provides access to the value of that type
in the @code{awk_value_t} struct.
Given a scalar cookie, @command{gawk} can directly retrieve or
modify the value, as required, without having to find it first.
The @code{awk_value_cookie_t} type and @code{value_cookie} macro are similar.
If you know that you wish to
use the same numeric or string @emph{value} for one or more variables,
you can create the value once, retaining a @dfn{value cookie} for it,
and then pass in that value cookie whenever you wish to set the value of a
variable. This saves storage space within the running @command{gawk}
process and reduces the time needed to create the value.
@node Memory Allocation Functions
@subsection Memory Allocation Functions and Convenience Macros
@cindex allocating memory for extensions
@cindex extensions @subentry loadable @subentry allocating memory
@cindex memory, allocating for extensions
The API provides a number of @dfn{memory allocation} functions for
allocating memory that can be passed to @command{gawk}, as well as a number of
convenience macros.
This @value{SUBSECTION} presents them all as function prototypes, in
the way that extension code would use them:
@table @code
@item void *gawk_malloc(size_t size);
Call the correct version of @code{malloc()} to allocate storage that may
be passed to @command{gawk}.
@item void *gawk_calloc(size_t nmemb, size_t size);
Call the correct version of @code{calloc()} to allocate storage that may
be passed to @command{gawk}.
@item void *gawk_realloc(void *ptr, size_t size);
Call the correct version of @code{realloc()} to allocate storage that may
be passed to @command{gawk}.
@item void gawk_free(void *ptr);
Call the correct version of @code{free()} to release storage that was
allocated with @code{gawk_malloc()}, @code{gawk_calloc()}, or @code{gawk_realloc()}.
@end table
The API has to provide these functions because it is possible
for an extension to be compiled and linked against a different
version of the C library than was used for the @command{gawk}
executable.@footnote{This is more common on MS-Windows systems, but it
can happen on Unix-like systems as well.} If @command{gawk} were
to use its version of @code{free()} when the memory came from an
unrelated version of @code{malloc()}, unexpected behavior would
likely result.
Three convenience macros may be used for allocating storage
from @code{gawk_malloc()}, @code{gawk_calloc}, and
@code{gawk_realloc()}. If the allocation fails, they cause @command{gawk}
to exit with a fatal error message. They should be used as if they were
procedure calls that do not return a value:
@table @code
@item #define emalloc(pointer, type, size, message) @dots{}
The arguments to this macro are as follows:
@c nested table
@table @code
@item pointer
The pointer variable to point at the allocated storage.
@item type
The type of the pointer variable. This is used to create a cast for
the call to @code{gawk_malloc()}.
@item size
The total number of bytes to be allocated.
@item message
A message to be prefixed to the fatal error message. Typically this is the name
of the function using the macro.
@end table
@noindent
For example, you might allocate a string value like so:
@example
@group
awk_value_t result;
char *message;
const char greet[] = "Don't Panic!";
emalloc(message, char *, sizeof(greet), "myfunc");
strcpy(message, greet);
make_malloced_string(message, strlen(message), & result);
@end group
@end example
@sp 2
@item #define ezalloc(pointer, type, size, message) @dots{}
This is like @code{emalloc()}, but it calls @code{gawk_calloc()}
instead of @code{gawk_malloc()}.
The arguments are the same as for the @code{emalloc()} macro, but this
macro guarantees that the memory returned is initialized to zero.
@item #define erealloc(pointer, type, size, message) @dots{}
This is like @code{emalloc()}, but it calls @code{gawk_realloc()}
instead of @code{gawk_malloc()}.
The arguments are the same as for the @code{emalloc()} macro.
@end table
Two additional functions allocate MPFR and GMP objects for use
by extension functions that need to create and then return such
values:
@table @code
@item void *get_mpfr_ptr();
Allocate and initialize an MPFR object and return a pointer to it.
If the allocation fails, @command{gawk} exits with a fatal
``out of memory'' error. If @command{gawk} was compiled without
MPFR support, calling this function causes a fatal error.
@item void *get_mpz_ptr();
Allocate and initialize a GMP object and return a pointer to it.
If the allocation fails, @command{gawk} exits with a fatal
``out of memory'' error. If @command{gawk} was compiled without
MPFR support, calling this function causes a fatal error.
@end table
Both of these functions return @samp{void *}, since the @file{gawkapi.h}
header file should not have dependency upon @code{<mpfr.h>} (and @code{<gmp.h>},
which is included from @code{<mpfr.h>}). The actual return values are of
types @code{mpfr_ptr} and @code{mpz_ptr} respectively, and you should cast
the return values appropriately before assigning the results to variables
of the correct types.
@node Constructor Functions
@subsection Constructor Functions
The API provides a number of @dfn{constructor} functions for creating
string and numeric values, as well as a number of convenience macros.
This @value{SUBSECTION} presents them all as function prototypes, in
the way that extension code would use them:
@table @code
@item static inline awk_value_t *
@itemx make_const_string(const char *string, size_t length, awk_value_t *result);
This function creates a string value in the @code{awk_value_t} variable
pointed to by @code{result}. It expects @code{string} to be a C string constant
(or other string data), and automatically creates a @emph{copy} of the data
for storage in @code{result}. It returns @code{result}.
@item static inline awk_value_t *
@itemx make_malloced_string(const char *string, size_t length, awk_value_t *result);
This function creates a string value in the @code{awk_value_t} variable
pointed to by @code{result}. It expects @code{string} to be a @samp{char *}
value pointing to data previously obtained from @code{gawk_malloc()}, @code{gawk_calloc()}, or @code{gawk_realloc()}. The idea here
is that the data is passed directly to @command{gawk}, which assumes
responsibility for it. It returns @code{result}.
@item static inline awk_value_t *
@itemx make_null_string(awk_value_t *result);
This specialized function creates a null string (the ``undefined'' value)
in the @code{awk_value_t} variable pointed to by @code{result}.
It returns @code{result}.
@item static inline awk_value_t *
@itemx make_number(double num, awk_value_t *result);
This function simply creates a numeric value in the @code{awk_value_t} variable
pointed to by @code{result}.
@item static inline awk_value_t *
@itemx make_number_mpz(void *mpz, awk_value_t *result);
This function creates a GMP number value in @code{result}.
The @code{mpz} must be from a call to @code{get_mpz_ptr()}
(and thus be of real underlying type @code{mpz_ptr}).
@command{gawk} takes ownership of this memory.
@item static inline awk_value_t *
@itemx make_number_mpfr(void *mpfr, awk_value_t *result);
This function creates an MPFR number value in @code{result}.
The @code{mpfr} must be from a call to @code{get_mpfr_ptr()}.
(and thus be of real underlying type @code{mpfr_ptr})
@command{gawk} takes ownership of this memory.
@item static inline awk_value_t *
@itemx make_const_user_input(const char *string, size_t length, awk_value_t *result);
This function is identical to @code{make_const_string()}, but the string is
flagged as user input that should be treated as a strnum value if the contents
of the string are numeric.
@item static inline awk_value_t *
@itemx make_malloced_user_input(const char *string, size_t length, awk_value_t *result);
This function is identical to @code{make_malloced_string()}, but the string is
flagged as user input that should be treated as a strnum value if the contents
of the string are numeric.
@item static inline awk_value_t *
@itemx make_const_regex(const char *string, size_t length, awk_value_t *result);
This function creates a strongly typed regexp value by allocating a copy of the string.
@code{string} is the regular expression of length @code{len}.
@item static inline awk_value_t *
@itemx make_malloced_regex(const char *string, size_t length, awk_value_t *result);
This function creates a strongly typed regexp value. @code{string} is
the regular expression of length @code{len}. It expects @code{string}
to be a @samp{char *} value pointing to data previously obtained from
@code{gawk_malloc()}, @code{gawk_calloc()}, or @code{gawk_realloc()}.
@end table
@node Registration Functions
@subsection Registration Functions
@cindex register loadable extension
@cindex extensions @subentry loadable @subentry registration
This @value{SECTION} describes the API functions for
registering parts of your extension with @command{gawk}.
@menu
* Extension Functions:: Registering extension functions.
* Exit Callback Functions:: Registering an exit callback.
* Extension Version String:: Registering a version string.
* Input Parsers:: Registering an input parser.
* Output Wrappers:: Registering an output wrapper.
* Two-way processors:: Registering a two-way processor.
@end menu
@node Extension Functions
@subsubsection Registering An Extension Function
Extension functions are described by the following record:
@example
@group
typedef struct awk_ext_func @{
@ @ @ @ const char *name;
@ @ @ @ awk_value_t *(*const function)(int num_actual_args,
@ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_value_t *result,
@ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ struct awk_ext_func *finfo);
@ @ @ @ const size_t max_expected_args;
@ @ @ @ const size_t min_required_args;
@ @ @ @ awk_bool_t suppress_lint;
@ @ @ @ void *data; /* opaque pointer to any extra state */
@} awk_ext_func_t;
@end group
@end example
The fields are:
@table @code
@item const char *name;
The name of the new function.
@command{awk}-level code calls the function by this name.
This is a regular C string.
Function names must obey the rules for @command{awk}
identifiers. That is, they must begin with either an English letter
or an underscore, which may be followed by any number of
letters, digits, and underscores.
Letter case in function names is significant.
@item awk_value_t *(*const function)(int num_actual_args,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_value_t *result,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ struct awk_ext_func *finfo);
This is a pointer to the C function that provides the extension's
functionality.
The function must fill in @code{*result} with either a number,
a string, or a regexp.
@command{gawk} takes ownership of any string memory.
As mentioned earlier, string memory @emph{must} come from one of
@code{gawk_malloc()}, @code{gawk_calloc()}, or @code{gawk_realloc()}.
The @code{num_actual_args} argument tells the C function how many
actual parameters were passed from the calling @command{awk} code.
The @code{finfo} parameter is a pointer to the @code{awk_ext_func_t} for
this function. The called function may access data within it as desired, or not.
The function must return the value of @code{result}.
This is for the convenience of the calling code inside @command{gawk}.
@item const size_t max_expected_args;
This is the maximum number of arguments the function expects to receive.
If called with more arguments than this, and if lint checking has
been enabled, then @command{gawk} prints a warning message. For more
information, see the entry for @code{suppress_lint}, later in this list.
@item const size_t min_required_args;
This is the minimum number of arguments the function expects to receive.
If called with fewer arguments, @command{gawk} prints a fatal error
message and exits.
@item awk_bool_t suppress_lint;
This flag tells @command{gawk} not to print a lint message if lint
checking has been enabled and if more arguments were supplied in the call
than expected. An extension function can tell if @command{gawk} already
printed at least one such message by checking if @samp{num_actual_args >
finfo->max_expected_args}. If so, and the function does not want more
lint messages to be printed, it should set @code{finfo->suppress_lint}
to @code{awk_true}.
@item void *data;
This is an opaque pointer to any data that an extension function may
wish to have available when called. Passing the @code{awk_ext_func_t}
structure to the extension function, and having this pointer available
in it enable writing a single C or C++ function that implements multiple
@command{awk}-level extension functions.
@end table
Once you have a record representing your extension function, you register
it with @command{gawk} using this API function:
@table @code
@item awk_bool_t add_ext_func(const char *name_space, awk_ext_func_t *func);
This function returns true upon success, false otherwise.
The @code{name_space} parameter is the namespace in which to place
the function (@pxref{Namespaces}).
Use an empty string (@code{""}) or @code{"awk"} to place
the function in the default @code{awk} namespace.
The @code{func} pointer is the address of a
@code{struct} representing your function, as just described.
@command{gawk} does not modify what @code{func} points to, but the
extension function itself receives this pointer and can modify what it
points to, thus it is purposely not declared to be @code{const}.
@end table
The combination of @code{min_required_args}, @code{max_expected_args},
and @code{suppress_lint} may be confusing. Here is how you should
set things up.
@table @asis
@item Any number of arguments is valid
Set @code{min_required_args} and @code{max_expected_args} to zero and
set @code{suppress_lint} to @code{awk_true}.
@item A minimum number of arguments is required, no limit on maximum number of arguments
Set @code{min_required_args} to the minimum required. Set
@code{max_expected_args} to zero and
set @code{suppress_lint} to @code{awk_true}.
@item A minimum number of arguments is required, a maximum number is expected
Set @code{min_required_args} to the minimum required. Set
@code{max_expected_args} to the maximum expected.
Set @code{suppress_lint} to @code{awk_false}.
@item A minimum number of arguments is required, and no more than a maximum is allowed
Set @code{min_required_args} to the minimum required. Set
@code{max_expected_args} to the maximum expected.
Set @code{suppress_lint} to @code{awk_false}.
In your extension function, check that @code{num_actual_args} does not
exceed @code{f->max_expected_args}. If it does, issue a fatal error message.
@end table
@node Exit Callback Functions
@subsubsection Registering An Exit Callback Function
An @dfn{exit callback} function is a function that
@command{gawk} calls before it exits.
Such functions are useful if you have general ``cleanup'' tasks
that should be performed in your extension (such as closing database
connections or other resource deallocations).
You can register such
a function with @command{gawk} using the following function:
@table @code
@item void awk_atexit(void (*funcp)(void *data, int exit_status),
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ void *arg0);
The parameters are:
@c nested table
@table @code
@item funcp
A pointer to the function to be called before @command{gawk} exits. The @code{data}
parameter will be the original value of @code{arg0}.
The @code{exit_status} parameter is the exit status value that
@command{gawk} intends to pass to the @code{exit()} system call.
@item arg0
A pointer to private data that @command{gawk} saves in order to pass to
the function pointed to by @code{funcp}.
@end table
@end table
Exit callback functions are called in last-in, first-out (LIFO)
order---that is, in the reverse order in which they are registered with
@command{gawk}.
@node Extension Version String
@subsubsection Registering An Extension Version String
You can register a version string that indicates the name and
version of your extension with @command{gawk}, as follows:
@table @code
@item void register_ext_version(const char *version);
Register the string pointed to by @code{version} with @command{gawk}.
Note that @command{gawk} does @emph{not} copy the @code{version} string, so
it should not be changed.
@end table
@command{gawk} prints all registered extension version strings when it
is invoked with the @option{--version} option.
@node Input Parsers
@subsubsection Customized Input Parsers
@cindex customized input parser
By default, @command{gawk} reads text files as its input. It uses the value
of @code{RS} to find the end of the record, and then uses @code{FS}
(or @code{FIELDWIDTHS} or @code{FPAT}) to split it into fields (@pxref{Reading Files}).
Additionally, it sets the value of @code{RT} (@pxref{Built-in Variables}).
If you want, you can provide your own custom input parser. An input
parser's job is to return a record to the @command{gawk} record-processing
code, along with indicators for the value and length of the data to be
used for @code{RT}, if any.
To provide an input parser, you must first provide two functions
(where @var{XXX} is a prefix name for your extension):
@table @code
@item awk_bool_t @var{XXX}_can_take_file(const awk_input_buf_t *iobuf);
This function examines the information available in @code{iobuf}
(which we discuss shortly). Based on the information there, it
decides if the input parser should be used for this file.
If so, it should return true. Otherwise, it should return false.
It should not change any state (variable values, etc.) within @command{gawk}.
@item awk_bool_t @var{XXX}_take_control_of(awk_input_buf_t *iobuf);
When @command{gawk} decides to hand control of the file over to the
input parser, it calls this function. This function in turn must fill
in certain fields in the @code{awk_input_buf_t} structure and ensure
that certain conditions are true. It should then return true. If an
error of some kind occurs, it should not fill in any fields and should
return false; then @command{gawk} will not use the input parser.
The details are presented shortly.
@end table
Your extension should package these functions inside an
@code{awk_input_parser_t}, which looks like this:
@example
@group
typedef struct awk_input_parser @{
const char *name; /* name of parser */
awk_bool_t (*can_take_file)(const awk_input_buf_t *iobuf);
awk_bool_t (*take_control_of)(awk_input_buf_t *iobuf);
awk_const struct awk_input_parser *awk_const next; /* for gawk */
@} awk_input_parser_t;
@end group
@end example
The fields are:
@table @code
@item const char *name;
The name of the input parser. This is a regular C string.
@item awk_bool_t (*can_take_file)(const awk_input_buf_t *iobuf);
A pointer to your @code{@var{XXX}_can_take_file()} function.
@item awk_bool_t (*take_control_of)(awk_input_buf_t *iobuf);
A pointer to your @code{@var{XXX}_take_control_of()} function.
@item awk_const struct input_parser *awk_const next;
This is for use by @command{gawk};
therefore it is marked @code{awk_const} so that the extension cannot
modify it.
@end table
The steps are as follows:
@enumerate
@item
Create a @code{static awk_input_parser_t} variable and initialize it
appropriately.
@item
When your extension is loaded, register your input parser with
@command{gawk} using the @code{register_input_parser()} API function
(described next).
@end enumerate
An @code{awk_input_buf_t} looks like this:
@example
typedef struct awk_input @{
const char *name; /* filename */
int fd; /* file descriptor */
#define INVALID_HANDLE (-1)
void *opaque; /* private data for input parsers */
int (*get_record)(char **out, struct awk_input *iobuf,
int *errcode, char **rt_start, size_t *rt_len,
const awk_fieldwidth_info_t **field_width);
ssize_t (*read_func)();
void (*close_func)(struct awk_input *iobuf);
struct stat sbuf; /* stat buf */
@} awk_input_buf_t;
@end example
The fields can be divided into two categories: those for use (initially,
at least) by @code{@var{XXX}_can_take_file()}, and those for use by
@code{@var{XXX}_take_control_of()}. The first group of fields and their uses
are as follows:
@table @code
@item const char *name;
The name of the file.
@item int fd;
A file descriptor for the file. If @command{gawk} was able to
open the file, then @code{fd} will @emph{not} be equal to
@code{INVALID_HANDLE}. Otherwise, it will.
@item struct stat sbuf;
If the file descriptor is valid, then @command{gawk} will have filled
in this structure via a call to the @code{fstat()} system call.
@end table
The @code{@var{XXX}_can_take_file()} function should examine these
fields and decide if the input parser should be used for the file.
The decision can be made based upon @command{gawk} state (the value
of a variable defined previously by the extension and set by
@command{awk} code), the name of the
file, whether or not the file descriptor is valid, the information
in the @code{struct stat}, or any combination of these factors.
Once @code{@var{XXX}_can_take_file()} has returned true, and
@command{gawk} has decided to use your input parser, it calls
@code{@var{XXX}_take_control_of()}. That function then fills
either the @code{get_record} field or the @code{read_func} field in
the @code{awk_input_buf_t}. It must also ensure that @code{fd} is @emph{not}
set to @code{INVALID_HANDLE}. The following list describes the fields that
may be filled by @code{@var{XXX}_take_control_of()}:
@table @code
@item void *opaque;
This is used to hold any state information needed by the input parser
for this file. It is ``opaque'' to @command{gawk}. The input parser
is not required to use this pointer.
@item int@ (*get_record)(char@ **out,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ struct@ awk_input *iobuf,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ int *errcode,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ char **rt_start,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ size_t *rt_len,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ const awk_fieldwidth_info_t **field_width);
This function pointer should point to a function that creates the input
records. Said function is the core of the input parser. Its behavior
is described in the text following this list.
@item ssize_t (*read_func)();
This function pointer should point to a function that has the
same behavior as the standard POSIX @code{read()} system call.
It is an alternative to the @code{get_record} pointer. Its behavior
is also described in the text following this list.
@item void (*close_func)(struct awk_input *iobuf);
This function pointer should point to a function that does
the ``teardown.'' It should release any resources allocated by
@code{@var{XXX}_take_control_of()}. It may also close the file. If it
does so, it should set the @code{fd} field to @code{INVALID_HANDLE}.
If @code{fd} is still not @code{INVALID_HANDLE} after the call to this
function, @command{gawk} calls the regular @code{close()} system call.
Having a ``teardown'' function is optional. If your input parser does
not need it, do not set this field. Then, @command{gawk} calls the
regular @code{close()} system call on the file descriptor, so it should
be valid.
@end table
The @code{@var{XXX}_get_record()} function does the work of creating
input records. The parameters are as follows:
@table @code
@item char **out
This is a pointer to a @code{char *} variable that is set to point
to the record. @command{gawk} makes its own copy of the data, so
the extension must manage this storage.
@item struct awk_input *iobuf
This is the @code{awk_input_buf_t} for the file. The fields should be
used for reading data (@code{fd}) and for managing private state
(@code{opaque}), if any.
@item int *errcode
If an error occurs, @code{*errcode} should be set to an appropriate
code from @code{<errno.h>}.
@item char **rt_start
@itemx size_t *rt_len
If the concept of a ``record terminator'' makes sense, then
@code{*rt_start} should be set to point to the data to be used for
@code{RT}, and @code{*rt_len} should be set to the length of the
data. Otherwise, @code{*rt_len} should be set to zero.
@command{gawk} makes its own copy of this data, so the
extension must manage this storage.
@item const awk_fieldwidth_info_t **field_width
If @code{field_width} is not @code{NULL}, then @code{*field_width} will be initialized
to @code{NULL}, and the function may set it to point to a structure
supplying field width information to override the default
field parsing mechanism. Note that this structure will not
be copied by @command{gawk}; it must persist at least until the next call
to @code{get_record} or @code{close_func}. Note also that @code{field_width} is
@code{NULL} when @code{getline} is assigning the results to a variable, thus
field parsing is not needed. If the parser does set @code{*field_width},
then @command{gawk} uses this layout to parse the input record,
and the @code{PROCINFO["FS"]} value will be @code{"API"} while this record
is active in @code{$0}.
The @code{awk_fieldwidth_info_t} data structure
is described below.
@end table
The return value is the length of the buffer pointed to by
@code{*out}, or @code{EOF} if end-of-file was reached or an
error occurred.
It is guaranteed that @code{errcode} is a valid pointer, so there is no
need to test for a @code{NULL} value. @command{gawk} sets @code{*errcode}
to zero, so there is no need to set it unless an error occurs.
If an error does occur, the function should return @code{EOF} and set
@code{*errcode} to a value greater than zero. In that case, if @code{*errcode}
does not equal zero, @command{gawk} automatically updates
the @code{ERRNO} variable based on the value of @code{*errcode}.
(In general, setting @samp{*errcode = errno} should do the right thing.)
As an alternative to supplying a function that returns an input record,
you may instead supply a function that simply reads bytes, and let
@command{gawk} parse the data into records. If you do so, the data
should be returned in the multibyte encoding of the current locale.
Such a function should follow the same behavior as the @code{read()}
system call, and you fill in the @code{read_func} pointer with its
address in the @code{awk_input_buf_t} structure.
By default, @command{gawk} sets the @code{read_func} pointer to
point to the @code{read()} system call. So your extension need not
set this field explicitly.
@quotation NOTE
You must choose one method or the other: either a function that
returns a record, or one that returns raw data. In particular,
if you supply a function to get a record, @command{gawk} will
call it, and will never call the raw read function.
@end quotation
@command{gawk} ships with a sample extension that reads directories,
returning records for each entry in a directory (@pxref{Extension
Sample Readdir}). You may wish to use that code as a guide for writing
your own input parser.
When writing an input parser, you should think about (and document)
how it is expected to interact with @command{awk} code. You may want
it to always be called, and to take effect as appropriate (as the
@code{readdir} extension does). Or you may want it to take effect
based upon the value of an @command{awk} variable, as the XML extension
from the @code{gawkextlib} project does (@pxref{gawkextlib}).
In the latter case, code in a @code{BEGINFILE} rule
can look at @code{FILENAME} and @code{ERRNO} to decide whether or
not to activate an input parser (@pxref{BEGINFILE/ENDFILE}).
You register your input parser with the following function:
@table @code
@item void register_input_parser(awk_input_parser_t *input_parser);
Register the input parser pointed to by @code{input_parser} with
@command{gawk}.
@end table
If you would like to override the default field parsing mechanism for a given
record, then you must populate an @code{awk_fieldwidth_info_t} structure,
which looks like this:
@example
typedef struct @{
awk_bool_t use_chars; /* false ==> use bytes */
size_t nf; /* number of fields in record (NF) */
struct awk_field_info @{
size_t skip; /* amount to skip before field starts */
size_t len; /* length of field */
@} fields[1]; /* actual dimension should be nf */
@} awk_fieldwidth_info_t;
@end example
The fields are:
@table @code
@item awk_bool_t use_chars;
Set this to @code{awk_true} if the field lengths are specified in terms
of potentially multi-byte characters, and set it to @code{awk_false} if
the lengths are in terms of bytes.
Performance will be better if the values are supplied in
terms of bytes.
@item size_t nf;
Set this to the number of fields in the input record, i.e. @code{NF}.
@item struct awk_field_info fields[nf];
This is a variable-length array whose actual dimension should be @code{nf}.
For each field, the @code{skip} element should be set to the number
of characters or bytes, as controlled by the @code{use_chars} flag,
to skip before the start of this field. The @code{len} element provides
the length of the field. The values in @code{fields[0]} provide the information
for @code{$1}, and so on through the @code{fields[nf-1]} element containing the information for @code{$NF}.
@end table
A convenience macro @code{awk_fieldwidth_info_size(numfields)} is provided to
calculate the appropriate size of a variable-length
@code{awk_fieldwidth_info_t} structure containing @code{numfields} fields. This can
be used as an argument to @code{malloc()} or in a union to allocate space
statically. Please refer to the @code{readdir_test} sample extension for an
example.
@node Output Wrappers
@subsubsection Customized Output Wrappers
@cindex customized output wrapper
@cindex output wrapper
An @dfn{output wrapper} is the mirror image of an input parser.
It allows an extension to take over the output to a file opened
with the @samp{>} or @samp{>>} I/O redirection operators (@pxref{Redirection}).
The output wrapper is very similar to the input parser structure:
@example
typedef struct awk_output_wrapper @{
const char *name; /* name of the wrapper */
awk_bool_t (*can_take_file)(const awk_output_buf_t *outbuf);
awk_bool_t (*take_control_of)(awk_output_buf_t *outbuf);
awk_const struct awk_output_wrapper *awk_const next; /* for gawk */
@} awk_output_wrapper_t;
@end example
The members are as follows:
@table @code
@item const char *name;
This is the name of the output wrapper.
@item awk_bool_t (*can_take_file)(const awk_output_buf_t *outbuf);
This points to a function that examines the information in
the @code{awk_output_buf_t} structure pointed to by @code{outbuf}.
It should return true if the output wrapper wants to take over the
file, and false otherwise. It should not change any state (variable
values, etc.) within @command{gawk}.
@item awk_bool_t (*take_control_of)(awk_output_buf_t *outbuf);
The function pointed to by this field is called when @command{gawk}
decides to let the output wrapper take control of the file. It should
fill in appropriate members of the @code{awk_output_buf_t} structure,
as described next, and return true if successful, false otherwise.
@item awk_const struct output_wrapper *awk_const next;
This is for use by @command{gawk};
therefore it is marked @code{awk_const} so that the extension cannot
modify it.
@end table
The @code{awk_output_buf_t} structure looks like this:
@example
typedef struct awk_output_buf @{
const char *name; /* name of output file */
const char *mode; /* mode argument to fopen */
FILE *fp; /* stdio file pointer */
awk_bool_t redirected; /* true if a wrapper is active */
void *opaque; /* for use by output wrapper */
size_t (*gawk_fwrite)(const void *buf, size_t size, size_t count,
FILE *fp, void *opaque);
int (*gawk_fflush)(FILE *fp, void *opaque);
int (*gawk_ferror)(FILE *fp, void *opaque);
int (*gawk_fclose)(FILE *fp, void *opaque);
@} awk_output_buf_t;
@end example
Here too, your extension will define @code{@var{XXX}_can_take_file()}
and @code{@var{XXX}_take_control_of()} functions that examine and update
data members in the @code{awk_output_buf_t}.
The data members are as follows:
@table @code
@item const char *name;
The name of the output file.
@item const char *mode;
The mode string (as would be used in the second argument to @code{fopen()})
with which the file was opened.
@item FILE *fp;
The @code{FILE} pointer from @code{<stdio.h>}. @command{gawk} opens the file
before attempting to find an output wrapper.
@item awk_bool_t redirected;
This field must be set to true by the @code{@var{XXX}_take_control_of()} function.
@item void *opaque;
This pointer is opaque to @command{gawk}. The extension should use it to store
a pointer to any private data associated with the file.
@item size_t (*gawk_fwrite)(const void *buf, size_t size, size_t count,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ FILE *fp, void *opaque);
@itemx int (*gawk_fflush)(FILE *fp, void *opaque);
@itemx int (*gawk_ferror)(FILE *fp, void *opaque);
@itemx int (*gawk_fclose)(FILE *fp, void *opaque);
These pointers should be set to point to functions that perform
the equivalent function as the @code{<stdio.h>} functions do, if appropriate.
@command{gawk} uses these function pointers for all output.
@command{gawk} initializes the pointers to point to internal ``pass-through''
functions that just call the regular @code{<stdio.h>} functions, so an
extension only needs to redefine those functions that are appropriate for
what it does.
@end table
The @code{@var{XXX}_can_take_file()} function should make a decision based
upon the @code{name} and @code{mode} fields, and any additional state
(such as @command{awk} variable values) that is appropriate.
When @command{gawk} calls @code{@var{XXX}_take_control_of()}, that function should fill
in the other fields as appropriate, except for @code{fp}, which it should just
use normally.
You register your output wrapper with the following function:
@table @code
@item void register_output_wrapper(awk_output_wrapper_t *output_wrapper);
Register the output wrapper pointed to by @code{output_wrapper} with
@command{gawk}.
@end table
@node Two-way processors
@subsubsection Customized Two-way Processors
@cindex customized two-way processor
A @dfn{two-way processor} combines an input parser and an output wrapper for
two-way I/O with the @samp{|&} operator (@pxref{Redirection}). It makes identical
use of the @code{awk_input_parser_t} and @code{awk_output_buf_t} structures
as described earlier.
A two-way processor is represented by the following structure:
@example
typedef struct awk_two_way_processor @{
const char *name; /* name of the two-way processor */
awk_bool_t (*can_take_two_way)(const char *name);
awk_bool_t (*take_control_of)(const char *name,
awk_input_buf_t *inbuf,
awk_output_buf_t *outbuf);
awk_const struct awk_two_way_processor *awk_const next; /* for gawk */
@} awk_two_way_processor_t;
@end example
The fields are as follows:
@table @code
@item const char *name;
The name of the two-way processor.
@item awk_bool_t (*can_take_two_way)(const char *name);
The function pointed to by this field should return true if it wants to take over two-way I/O for this @value{FN}.
It should not change any state (variable
values, etc.) within @command{gawk}.
@item awk_bool_t (*take_control_of)(const char *name,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_input_buf_t *inbuf,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_output_buf_t *outbuf);
The function pointed to by this field should fill in the @code{awk_input_buf_t} and
@code{awk_output_buf_t} structures pointed to by @code{inbuf} and
@code{outbuf}, respectively. These structures were described earlier.
@item awk_const struct two_way_processor *awk_const next;
This is for use by @command{gawk};
therefore it is marked @code{awk_const} so that the extension cannot
modify it.
@end table
As with the input parser and output processor, you provide
``yes I can take this'' and ``take over for this'' functions,
@code{@var{XXX}_can_take_two_way()} and @code{@var{XXX}_take_control_of()}.
You register your two-way processor with the following function:
@table @code
@item void register_two_way_processor(awk_two_way_processor_t *two_way_processor);
Register the two-way processor pointed to by @code{two_way_processor} with
@command{gawk}.
@end table
@node Printing Messages
@subsection Printing Messages
@cindex printing @subentry messages from extensions
@cindex messages from extensions
You can print different kinds of warning messages from your
extension, as described here. Note that for these functions,
you must pass in the extension ID received from @command{gawk}
when the extension was loaded:@footnote{Because the API uses only ISO C 90
features, it cannot make use of the ISO C 99 variadic macro feature to hide
that parameter. More's the pity.}
@table @code
@item void fatal(awk_ext_id_t id, const char *format, ...);
Print a message and then cause @command{gawk} to exit immediately.
@item void nonfatal(awk_ext_id_t id, const char *format, ...);
Print a nonfatal error message.
@item void warning(awk_ext_id_t id, const char *format, ...);
Print a warning message.
@item void lintwarn(awk_ext_id_t id, const char *format, ...);
Print a ``lint warning.'' Normally this is the same as printing a
warning message, but if @command{gawk} was invoked with @samp{--lint=fatal},
then lint warnings become fatal error messages.
@end table
All of these functions are otherwise like the C @code{printf()}
family of functions, where the @code{format} parameter is a string
with literal characters and formatting codes intermixed.
@node Updating @code{ERRNO}
@subsection Updating @code{ERRNO}
The following functions allow you to update the @code{ERRNO}
variable:
@table @code
@item void update_ERRNO_int(int errno_val);
Set @code{ERRNO} to the string equivalent of the error code
in @code{errno_val}. The value should be one of the defined
error codes in @code{<errno.h>}, and @command{gawk} turns it
into a (possibly translated) string using the C @code{strerror()} function.
@item void update_ERRNO_string(const char *string);
Set @code{ERRNO} directly to the string value of @code{ERRNO}.
@command{gawk} makes a copy of the value of @code{string}.
@item void unset_ERRNO(void);
Unset @code{ERRNO}.
@end table
@node Requesting Values
@subsection Requesting Values
All of the functions that return values from @command{gawk}
work in the same way. You pass in an @code{awk_valtype_t} value
to indicate what kind of value you expect. If the actual value
matches what you requested, the function returns true and fills
in the @code{awk_value_t} result.
Otherwise, the function returns false, and the @code{val_type}
member indicates the type of the actual value. You may then
print an error message or reissue the request for the actual
value type, as appropriate. This behavior is summarized in
@ref{table-value-types-returned}.
@float Table,table-value-types-returned
@caption{API value types returned}
@docbook
<informaltable>
<tgroup cols="8">
<colspec colname="c1"/>
<colspec colname="c2"/>
<colspec colname="c3"/>
<colspec colname="c4"/>
<colspec colname="c5"/>
<colspec colname="c6"/>
<colspec colname="c7"/>
<colspec colname="c8"/>
<spanspec spanname="hspan" namest="c3" nameend="c8" align="center"/>
<thead>
<row><entry></entry><entry spanname="hspan"><para>Type of Actual Value</para></entry></row>
<row>
<entry></entry>
<entry></entry>
<entry><para>String</para></entry>
<entry><para>Strnum</para></entry>
<entry><para>Number</para></entry>
<entry><para>Regex</para></entry>
<entry><para>Array</para></entry>
<entry><para>Undefined</para></entry>
</row>
</thead>
<tbody>
<row>
<entry></entry>
<entry><para><emphasis role="bold">String</emphasis></para></entry>
<entry><para>String</para></entry>
<entry><para>String</para></entry>
<entry><para>String</para></entry>
<entry><para>String</para></entry>
<entry><para>false</para></entry>
<entry><para>false</para></entry>
</row>
<row>
<entry></entry>
<entry><para><emphasis role="bold">Strnum</emphasis></para></entry>
<entry><para>false</para></entry>
<entry><para>Strnum</para></entry>
<entry><para>Strnum</para></entry>
<entry><para>false</para></entry>
<entry><para>false</para></entry>
<entry><para>false</para></entry>
</row>
<row>
<entry></entry>
<entry><para><emphasis role="bold">Number</emphasis></para></entry>
<entry><para>Number</para></entry>
<entry><para>Number</para></entry>
<entry><para>Number</para></entry>
<entry><para>false</para></entry>
<entry><para>false</para></entry>
<entry><para>false</para></entry>
</row>
<row>
<entry><para><emphasis role="bold">Type</emphasis></para></entry>
<entry><para><emphasis role="bold">Regex</emphasis></para></entry>
<entry><para>false</para></entry>
<entry><para>false</para></entry>
<entry><para>Regex</para></entry>
<entry><para>false</para></entry>
<entry><para>false</para></entry>
<entry><para>false</para></entry>
</row>
<row>
<entry><para><emphasis role="bold">Requested</emphasis></para></entry>
<entry><para><emphasis role="bold">Array</emphasis></para></entry>
<entry><para>false</para></entry>
<entry><para>false</para></entry>
<entry><para>false</para></entry>
<entry><para>false</para></entry>
<entry><para>Array</para></entry>
<entry><para>false</para></entry>
</row>
<row>
<entry></entry>
<entry><para><emphasis role="bold">Scalar</emphasis></para></entry>
<entry><para>Scalar</para></entry>
<entry><para>Scalar</para></entry>
<entry><para>Scalar</para></entry>
<entry><para>Scalar</para></entry>
<entry><para>false</para></entry>
<entry><para>false</para></entry>
</row>
<row>
<entry></entry>
<entry><para><emphasis role="bold">Undefined</emphasis></para></entry>
<entry><para>String</para></entry>
<entry><para>Strnum</para></entry>
<entry><para>Number</para></entry>
<entry><para>Regex</para></entry>
<entry><para>Array</para></entry>
<entry><para>Undefined</para></entry>
</row>
<row>
<entry></entry>
<entry><para><emphasis role="bold">Value cookie</emphasis></para></entry>
<entry><para>false</para></entry>
<entry><para>false</para></entry>
<entry><para>false</para></entry>
<entry><para>false</para></entry>
<entry><para>false</para></entry>
<entry><para>false</para></entry>
</row>
</tbody>
</tgroup>
</informaltable>
@end docbook
@ifnotplaintext
@ifnotdocbook
@multitable @columnfractions .50 .50
@headitem @tab Type of Actual Value
@end multitable
@c 10/2014: Thanks to Karl Berry for this bit to reduce the space:
@tex
\vglue-1.1\baselineskip
@end tex
@c @multitable @columnfractions .166 .166 .198 .15 .15 .166
@multitable {Requested} {Undefined} {Number} {Number} {Scalar} {Regex} {Array} {Undefined}
@headitem @tab @tab String @tab Strnum @tab Number @tab Regex @tab Array @tab Undefined
@item @tab @b{String} @tab String @tab String @tab String @tab String @tab false @tab false
@item @tab @b{Strnum} @tab false @tab Strnum @tab Strnum @tab false @tab false @tab false
@item @tab @b{Number} @tab Number @tab Number @tab Number @tab false @tab false @tab false
@item @b{Type} @tab @b{Regex} @tab false @tab false @tab false @tab Regex @tab false @tab false
@item @b{Requested} @tab @b{Array} @tab false @tab false @tab false @tab false @tab Array @tab false
@item @tab @b{Scalar} @tab Scalar @tab Scalar @tab Scalar @tab Scalar @tab false @tab false
@item @tab @b{Undefined} @tab String @tab Strnum @tab Number @tab Regex @tab Array @tab Undefined
@item @tab @b{Value cookie} @tab false @tab false @tab false @tab false @tab false @tab false
@end multitable
@end ifnotdocbook
@end ifnotplaintext
@ifplaintext
@verbatim
+-------------------------------------------------------+
| Type of Actual Value: |
+--------+--------+--------+--------+-------+-----------+
| String | Strnum | Number | Regex | Array | Undefined |
+-----------+-----------+--------+--------+--------+--------+-------+-----------+
| | String | String | String | String | String | false | false |
| +-----------+--------+--------+--------+--------+-------+-----------+
| | Strnum | false | Strnum | Strnum | false | false | false |
| +-----------+--------+--------+--------+--------+-------+-----------+
| | Number | Number | Number | Number | false | false | false |
| +-----------+--------+--------+--------+--------+-------+-----------+
| | Regex | false | false | false | Regex | false | false |
| Type +-----------+--------+--------+--------+--------+-------+-----------+
| Requested | Array | false | false | false | false | Array | false |
| +-----------+--------+--------+--------+--------+-------+-----------+
| | Scalar | Scalar | Scalar | Scalar | Scalar | false | false |
| +-----------+--------+--------+--------+--------+-------+-----------+
| | Undefined | String | Strnum | Number | Regex | Array | Undefined |
| +-----------+--------+--------+--------+--------+-------+-----------+
| | Value | false | false | false | false | false | false |
| | Cookie | | | | | | |
+-----------+-----------+--------+--------+--------+--------+-------+-----------+
@end verbatim
@end ifplaintext
@end float
@node Accessing Parameters
@subsection Accessing and Updating Parameters
Two functions give you access to the arguments (parameters)
passed to your extension function. They are:
@table @code
@item awk_bool_t get_argument(size_t count,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_valtype_t wanted,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_value_t *result);
Fill in the @code{awk_value_t} structure pointed to by @code{result}
with the @code{count}th argument. Return true if the actual
type matches @code{wanted}, and false otherwise. In the latter
case, @code{result@w{->}val_type} indicates the actual type
(@pxref{table-value-types-returned}). Counts are zero-based---the first
argument is numbered zero, the second one, and so on. @code{wanted}
indicates the type of value expected.
@item awk_bool_t set_argument(size_t count, awk_array_t array);
Convert a parameter that was undefined into an array; this provides
call by reference for arrays. Return false if @code{count} is too big,
or if the argument's type is not undefined. @xref{Array Manipulation}
for more information on creating arrays.
@end table
@node Symbol Table Access
@subsection Symbol Table Access
@cindex accessing global variables from extensions
Two sets of routines provide access to global variables, and one set
allows you to create and release cached values.
@menu
* Symbol table by name:: Accessing variables by name.
* Symbol table by cookie:: Accessing variables by ``cookie''.
* Cached values:: Creating and using cached values.
@end menu
@node Symbol table by name
@subsubsection Variable Access and Update by Name
The following routines provide the ability to access and update
global @command{awk}-level variables by name. In compiler terminology,
identifiers of different kinds are termed @dfn{symbols}, thus the ``sym''
in the routines' names. The data structure that stores information
about symbols is termed a @dfn{symbol table}.
The functions are as follows:
@table @code
@item awk_bool_t sym_lookup(const char *name,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_valtype_t wanted,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_value_t *result);
Fill in the @code{awk_value_t} structure pointed to by @code{result}
with the value of the variable named by the string @code{name}, which is
a regular C string. @code{wanted} indicates the type of value expected.
Return true if the actual type matches @code{wanted}, and false otherwise.
In the latter case, @code{result->val_type} indicates the actual type
(@pxref{table-value-types-returned}).
@item awk_bool_t sym_lookup_ns(const char *name,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ const char *name_space,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_valtype_t wanted,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_value_t *result);
This is like @code{sym_lookup()}, but the @code{name_space} parameter allows you
to specify which namespace @code{name} is part of. @code{name_space} cannot be
@code{NULL}. If it is @code{""} or @code{"awk"}, then @code{name} is searched
for in the default @code{awk} namespace.
Note that @code{namespace} is a C++ keyword. For interoperability with C++,
you should avoid using that identifier in C code.
@item awk_bool_t sym_update(const char *name, awk_value_t *value);
Update the variable named by the string @code{name}, which is a regular
C string. The variable is added to @command{gawk}'s symbol table
if it is not there. Return true if everything worked, and false otherwise.
Changing types (scalar to array or vice versa) of an existing variable
is @emph{not} allowed, nor may this routine be used to update an array.
This routine cannot be used to update any of the predefined
variables (such as @code{ARGC} or @code{NF}).
@item awk_bool_t sym_update_ns(const char *name_space, const char *name, awk_value_t *value);
This is like @code{sym_update()}, but the @code{name_space} parameter allows you
to specify which namespace @code{name} is part of. @code{name_space} cannot be
@code{NULL}. If it is @code{""} or @code{"awk}, then @code{name} is searched
for in the default @code{awk} namespace.
@end table
An extension can look up the value of @command{gawk}'s special variables.
However, with the exception of the @code{PROCINFO} array, an extension
cannot change any of those variables.
When searching for or updating variables outside the @code{awk} namespace
(@pxref{Namespaces}), function and variable names must be simple
identifiers.@footnote{Allowing both namespace plus identifier and
@code{foo::bar} would have been too confusing to document, and to code
and test.} In addition, namespace names and variable and function names
must follow the rules given in @ref{Naming Rules}.
@node Symbol table by cookie
@subsubsection Variable Access and Update by Cookie
A @dfn{scalar cookie} is an opaque handle that provides access
to a global variable or array. It is an optimization that
avoids looking up variables in @command{gawk}'s symbol table every time
access is needed. This was discussed earlier, in @ref{General Data Types}.
@need 1500
The following functions let you work with scalar cookies:
@table @code
@item awk_bool_t sym_lookup_scalar(awk_scalar_t cookie,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_valtype_t wanted,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_value_t *result);
Retrieve the current value of a scalar cookie.
Once you have obtained a scalar cookie using @code{sym_lookup()}, you can
use this function to get its value more efficiently.
Return false if the value cannot be retrieved.
@item awk_bool_t sym_update_scalar(awk_scalar_t cookie, awk_value_t *value);
Update the value associated with a scalar cookie. Return false if
the new value is not of type @code{AWK_STRING}, @code{AWK_STRNUM}, @code{AWK_REGEX}, or @code{AWK_NUMBER}.
Here too, the predefined variables may not be updated.
@end table
It is not obvious at first glance how to work with scalar cookies or
what their @i{raison d'@^etre} really is. In theory, the @code{sym_lookup()}
and @code{sym_update()} routines are all you really need to work with
variables. For example, you might have code that looks up the value of
a variable, evaluates a condition, and then possibly changes the value
of the variable based on the result of that evaluation, like so:
@example
/* do_magic --- do something really great */
static awk_value_t *
do_magic(int nargs, awk_value_t *result)
@{
awk_value_t value;
if ( sym_lookup("MAGIC_VAR", AWK_NUMBER, & value)
&& some_condition(value.num_value)) @{
value.num_value += 42;
sym_update("MAGIC_VAR", & value);
@}
return make_number(0.0, result);
@}
@end example
@noindent
This code looks (and is) simple and straightforward. So what's the problem?
Well, consider what happens if @command{awk}-level code associated
with your extension calls the @code{magic()} function (implemented in
C by @code{do_magic()}), once per record, while processing hundreds
of thousands or millions of records. The @code{MAGIC_VAR} variable is
looked up in the symbol table once or twice per function call!
The symbol table lookup is really pure overhead; it is considerably
more efficient to get a cookie that represents the variable, and use
that to get the variable's value and update it as needed.@footnote{The
difference is measurable and quite real. Trust us.}
Thus, the way to use cookies is as follows. First, install
your extension's variable in @command{gawk}'s symbol table using
@code{sym_update()}, as usual. Then get a scalar cookie for the variable
using @code{sym_lookup()}:
@example
@group
static awk_scalar_t magic_var_cookie; /* cookie for MAGIC_VAR */
static void
my_extension_init()
@{
awk_value_t value;
@end group
/* install initial value */
sym_update("MAGIC_VAR", make_number(42.0, & value));
/* get the cookie */
sym_lookup("MAGIC_VAR", AWK_SCALAR, & value);
/* save the cookie */
magic_var_cookie = value.scalar_cookie;
@dots{}
@}
@end example
Next, use the routines in this @value{SECTION} for retrieving and updating
the value through the cookie. Thus, @code{do_magic()} now becomes
something like this:
@example
/* do_magic --- do something really great */
static awk_value_t *
do_magic(int nargs, awk_value_t *result)
@{
awk_value_t value;
if ( sym_lookup_scalar(magic_var_cookie, AWK_NUMBER, & value)
&& some_condition(value.num_value)) @{
value.num_value += 42;
sym_update_scalar(magic_var_cookie, & value);
@}
@dots{}
return make_number(0.0, result);
@}
@end example
@quotation NOTE
The previous code omitted error checking for
presentation purposes. Your extension code should be more robust
and carefully check the return values from the API functions.
@end quotation
@node Cached values
@subsubsection Creating and Using Cached Values
The routines in this @value{SECTION} allow you to create and release
cached values. Like scalar cookies, in theory, cached values
are not necessary. You can create numbers and strings using
the functions in @ref{Constructor Functions}. You can then
assign those values to variables using @code{sym_update()}
or @code{sym_update_scalar()}, as you like.
However, you can understand the point of cached values if you remember that
@emph{every} string value's storage @emph{must} come from @code{gawk_malloc()},
@code{gawk_calloc()}, or @code{gawk_realloc()}.
If you have 20 variables, all of which have the same string value, you
must create 20 identical copies of the string.@footnote{Numeric values
are clearly less problematic, requiring only a C @code{double} to store.
But of course, GMP and MPFR values @emph{do} take up more memory.}
It is clearly more efficient, if possible, to create a value once, and
then tell @command{gawk} to reuse the value for multiple variables. That
is what the routines in this @value{SECTION} let you do. The functions are as follows:
@table @code
@item awk_bool_t create_value(awk_value_t *value, awk_value_cookie_t *result);
Create a cached string or numeric value from @code{value} for
efficient later assignment. Only values of type @code{AWK_NUMBER}, @code{AWK_REGEX}, @code{AWK_STRNUM},
and @code{AWK_STRING} are allowed. Any other type is rejected.
@code{AWK_UNDEFINED} could be allowed, but doing so would result in
inferior performance.
@item awk_bool_t release_value(awk_value_cookie_t vc);
Release the memory associated with a value cookie obtained
from @code{create_value()}.
@end table
You use value cookies in a fashion similar to the way you use scalar cookies.
In the extension initialization routine, you create the value cookie:
@example
static awk_value_cookie_t answer_cookie; /* static value cookie */
static void
my_extension_init()
@{
awk_value_t value;
char *long_string;
size_t long_string_len;
/* code from earlier */
@dots{}
/* @dots{} fill in long_string and long_string_len @dots{} */
make_malloced_string(long_string, long_string_len, & value);
create_value(& value, & answer_cookie); /* create cookie */
@dots{}
@}
@end example
Once the value is created, you can use it as the value of any number
of variables:
@example
static awk_value_t *
do_magic(int nargs, awk_value_t *result)
@{
awk_value_t new_value;
@dots{} /* as earlier */
value.val_type = AWK_VALUE_COOKIE;
value.value_cookie = answer_cookie;
sym_update("VAR1", & value);
sym_update("VAR2", & value);
@dots{}
sym_update("VAR100", & value);
@dots{}
@}
@end example
@noindent
Using value cookies in this way saves considerable storage, as all of
@code{VAR1} through @code{VAR100} share the same value.
You might be wondering, ``Is this sharing problematic?
What happens if @command{awk} code assigns a new value to @code{VAR1};
are all the others changed too?''
That's a great question. The answer is that no, it's not a problem.
Internally, @command{gawk} uses @dfn{reference-counted strings}. This means
that many variables can share the same string value, and @command{gawk}
keeps track of the usage. When a variable's value changes, @command{gawk}
simply decrements the reference count on the old value and updates
the variable to use the new value.
Finally, as part of your cleanup action (@pxref{Exit Callback Functions})
you should release any cached values that you created, using
@code{release_value()}.
@node Array Manipulation
@subsection Array Manipulation
@cindex array manipulation in extensions
@cindex extensions @subentry loadable @subentry array manipulation in
The primary data structure@footnote{OK, the only data structure.} in @command{awk}
is the associative array (@pxref{Arrays}).
Extensions need to be able to manipulate @command{awk} arrays.
The API provides a number of data structures for working with arrays,
functions for working with individual elements, and functions for
working with arrays as a whole. This includes the ability to
``flatten'' an array so that it is easy for C code to traverse
every element in an array. The array data structures integrate
nicely with the data structures for values to make it easy to
both work with and create true arrays of arrays (@pxref{General Data Types}).
@menu
* Array Data Types:: Data types for working with arrays.
* Array Functions:: Functions for working with arrays.
* Flattening Arrays:: How to flatten arrays.
* Creating Arrays:: How to create and populate arrays.
@end menu
@node Array Data Types
@subsubsection Array Data Types
The data types associated with arrays are as follows:
@table @code
@item typedef void *awk_array_t;
If you request the value of an array variable, you get back an
@code{awk_array_t} value. This value is opaque@footnote{It is also
a ``cookie,'' but the @command{gawk} developers did not wish to overuse this
term.} to the extension; it uniquely identifies the array but can
only be used by passing it into API functions or receiving it from API
functions. This is very similar to way @samp{FILE *} values are used
with the @code{<stdio.h>} library routines.
@item typedef struct awk_element @{
@itemx @ @ @ @ /* convenience linked list pointer, not used by gawk */
@itemx @ @ @ @ struct awk_element *next;
@itemx @ @ @ @ enum @{
@itemx @ @ @ @ @ @ @ @ AWK_ELEMENT_DEFAULT = 0,@ @ /* set by gawk */
@itemx @ @ @ @ @ @ @ @ AWK_ELEMENT_DELETE = 1@ @ @ @ /* set by extension */
@itemx @ @ @ @ @} flags;
@itemx @ @ @ @ awk_value_t index;
@itemx @ @ @ @ awk_value_t value;
@itemx @} awk_element_t;
The @code{awk_element_t} is a ``flattened''
array element. @command{awk} produces an array of these
inside the @code{awk_flat_array_t} (see the next item).
Individual elements may be marked for deletion. New elements must be added
individually, one at a time, using the separate API for that purpose.
The fields are as follows:
@c nested table
@table @code
@item struct awk_element *next;
This pointer is for the convenience of extension writers. It allows
an extension to create a linked list of new elements that can then be
added to an array in a loop that traverses the list.
@item enum @{ @dots{} @} flags;
A set of flag values that convey information between the extension
and @command{gawk}. Currently there is only one: @code{AWK_ELEMENT_DELETE}.
Setting it causes @command{gawk} to delete the
element from the original array upon release of the flattened array.
@item index
@itemx value
The index and value of the element, respectively.
@emph{All} memory pointed to by @code{index} and @code{value} belongs to @command{gawk}.
@end table
@item typedef struct awk_flat_array @{
@itemx @ @ @ @ awk_const void *awk_const opaque1;@ @ @ @ /* for use by gawk */
@itemx @ @ @ @ awk_const void *awk_const opaque2;@ @ @ @ /* for use by gawk */
@itemx @ @ @ @ awk_const size_t count;@ @ @ @ @ /* how many elements */
@itemx @ @ @ @ awk_element_t elements[1];@ @ /* will be extended */
@itemx @} awk_flat_array_t;
This is a flattened array. When an extension gets one of these
from @command{gawk}, the @code{elements} array is of actual
size @code{count}.
The @code{opaque1} and @code{opaque2} pointers are for use by @command{gawk};
therefore they are marked @code{awk_const} so that the extension cannot
modify them.
@end table
@node Array Functions
@subsubsection Array Functions
The following functions relate to individual array elements:
@table @code
@item awk_bool_t get_element_count(awk_array_t a_cookie, size_t *count);
For the array represented by @code{a_cookie}, place in @code{*count}
the number of elements it contains. A subarray counts as a single element.
Return false if there is an error.
@item awk_bool_t get_array_element(awk_array_t a_cookie,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ const awk_value_t *const index,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_valtype_t wanted,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_value_t *result);
For the array represented by @code{a_cookie}, return in @code{*result}
the value of the element whose index is @code{index}.
@code{wanted} specifies the type of value you wish to retrieve.
Return false if @code{wanted} does not match the actual type or if
@code{index} is not in the array (@pxref{table-value-types-returned}).
The value for @code{index} can be numeric, in which case @command{gawk}
converts it to a string. Using nonintegral values is possible, but
requires that you understand how such values are converted to strings
(@pxref{Conversion}); thus, using integral values is safest.
As with @emph{all} strings passed into @command{gawk} from an extension,
the string value of @code{index} must come from @code{gawk_malloc()},
@code{gawk_calloc()}, or @code{gawk_realloc()}, and
@command{gawk} releases the storage.
@item awk_bool_t set_array_element(awk_array_t a_cookie,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ const@ awk_value_t *const index,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ const@ awk_value_t *const value);
In the array represented by @code{a_cookie}, create or modify
the element whose index is given by @code{index}.
The @code{ARGV} and @code{ENVIRON} arrays may not be changed,
although the @code{PROCINFO} array can be.
@item awk_bool_t set_array_element_by_elem(awk_array_t a_cookie,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_element_t element);
Like @code{set_array_element()}, but take the @code{index} and @code{value}
from @code{element}. This is a convenience macro.
@item awk_bool_t del_array_element(awk_array_t a_cookie,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ const awk_value_t* const index);
Remove the element with the given index from the array
represented by @code{a_cookie}.
Return true if the element was removed, or false if the element did
not exist in the array.
@end table
The following functions relate to arrays as a whole:
@table @code
@item awk_array_t create_array(void);
Create a new array to which elements may be added.
@xref{Creating Arrays} for a discussion of how to
create a new array and add elements to it.
@item awk_bool_t clear_array(awk_array_t a_cookie);
Clear the array represented by @code{a_cookie}.
Return false if there was some kind of problem, true otherwise.
The array remains an array, but after calling this function, it
has no elements. This is equivalent to using the @code{delete}
statement (@pxref{Delete}).
@item awk_bool_t flatten_array_typed(awk_array_t a_cookie,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_flat_array_t **data,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_valtype_t index_type,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_valtype_t value_type);
For the array represented by @code{a_cookie}, create an @code{awk_flat_array_t}
structure and fill it in with indices and values of the requested types.
Set the pointer whose address is passed as @code{data}
to point to this structure.
Return true upon success, or false otherwise.
@ifset FOR_PRINT
See the next @value{SECTION}
@end ifset
@ifclear FOR_PRINT
@xref{Flattening Arrays},
@end ifclear
for a discussion of how to
flatten an array and work with it.
@item awk_bool_t flatten_array(awk_array_t a_cookie, awk_flat_array_t **data);
For the array represented by @code{a_cookie}, create an @code{awk_flat_array_t}
structure and fill it in with @code{AWK_STRING} indices and
@code{AWK_UNDEFINED} values.
This is superseded by @code{flatten_array_typed()}.
It is provided as a macro, and remains for convenience and for source code
compatibility with the previous version of the API.
@item awk_bool_t release_flattened_array(awk_array_t a_cookie,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ awk_flat_array_t *data);
When done with a flattened array, release the storage using this function.
You must pass in both the original array cookie and the address of
the created @code{awk_flat_array_t} structure.
The function returns true upon success, false otherwise.
@end table
@node Flattening Arrays
@subsubsection Working With All The Elements of an Array
To @dfn{flatten} an array is to create a structure that
represents the full array in a fashion that makes it easy
for C code to traverse the entire array. Some of the code
in @file{extension/testext.c} does this, and also serves
as a nice example showing how to use the APIs.
We walk through that part of the code one step at a time.
First, the @command{gawk} script that drives the test extension:
@example
@@load "testext"
BEGIN @{
n = split("blacky rusty sophie raincloud lucky", pets)
printf("pets has %d elements\n", length(pets))
ret = dump_array_and_delete("pets", "3")
printf("dump_array_and_delete(pets) returned %d\n", ret)
if ("3" in pets)
printf("dump_array_and_delete() did NOT remove index \"3\"!\n")
else
printf("dump_array_and_delete() did remove index \"3\"!\n")
print ""
@}
@end example
@noindent
This code creates an array with @code{split()} (@pxref{String Functions})
and then calls @code{dump_array_and_delete()}. That function looks up
the array whose name is passed as the first argument, and
deletes the element at the index passed in the second argument.
The @command{awk} code then prints the return value and checks if the element
was indeed deleted. Here is the C code that implements
@code{dump_array_and_delete()}. It has been edited slightly for
presentation.
The first part declares variables, sets up the default
return value in @code{result}, and checks that the function
was called with the correct number of arguments:
@example
static awk_value_t *
dump_array_and_delete(int nargs, awk_value_t *result)
@{
awk_value_t value, value2, value3;
awk_flat_array_t *flat_array;
size_t count;
char *name;
int i;
assert(result != NULL);
make_number(0.0, result);
if (nargs != 2) @{
printf("dump_array_and_delete: nargs not right "
"(%d should be 2)\n", nargs);
goto out;
@}
@end example
The function then proceeds in steps, as follows. First, retrieve
the name of the array, passed as the first argument, followed by
the array itself. If either operation fails, print an
error message and return:
@example
/* get argument named array as flat array and print it */
if (get_argument(0, AWK_STRING, & value)) @{
name = value.str_value.str;
if (sym_lookup(name, AWK_ARRAY, & value2))
printf("dump_array_and_delete: sym_lookup of %s passed\n",
name);
else @{
printf("dump_array_and_delete: sym_lookup of %s failed\n",
name);
goto out;
@}
@} else @{
printf("dump_array_and_delete: get_argument(0) failed\n");
goto out;
@}
@end example
For testing purposes and to make sure that the C code sees
the same number of elements as the @command{awk} code,
the second step is to get the count of elements in the array
and print it:
@example
if (! get_element_count(value2.array_cookie, & count)) @{
printf("dump_array_and_delete: get_element_count failed\n");
goto out;
@}
printf("dump_array_and_delete: incoming size is %lu\n",
(unsigned long) count);
@end example
The third step is to actually flatten the array, and then
to double-check that the count in the @code{awk_flat_array_t}
is the same as the count just retrieved:
@example
if (! flatten_array_typed(value2.array_cookie, & flat_array,
AWK_STRING, AWK_UNDEFINED)) @{
printf("dump_array_and_delete: could not flatten array\n");
goto out;
@}
if (flat_array->count != count) @{
printf("dump_array_and_delete: flat_array->count (%lu)"
" != count (%lu)\n",
(unsigned long) flat_array->count,
(unsigned long) count);
goto out;
@}
@end example
The fourth step is to retrieve the index of the element
to be deleted, which was passed as the second argument.
Remember that argument counts passed to @code{get_argument()}
are zero-based, and thus the second argument is numbered one:
@example
if (! get_argument(1, AWK_STRING, & value3)) @{
printf("dump_array_and_delete: get_argument(1) failed\n");
goto out;
@}
@end example
The fifth step is where the ``real work'' is done. The function
loops over every element in the array, printing the index and
element values. In addition, upon finding the element with the
index that is supposed to be deleted, the function sets the
@code{AWK_ELEMENT_DELETE} bit in the @code{flags} field
of the element. When the array is released, @command{gawk}
traverses the flattened array, and deletes any elements that
have this flag bit set:
@example
for (i = 0; i < flat_array->count; i++) @{
printf("\t%s[\"%.*s\"] = %s\n",
name,
(int) flat_array->elements[i].index.str_value.len,
flat_array->elements[i].index.str_value.str,
valrep2str(& flat_array->elements[i].value));
if (strcmp(value3.str_value.str,
flat_array->elements[i].index.str_value.str) == 0) @{
flat_array->elements[i].flags |= AWK_ELEMENT_DELETE;
printf("dump_array_and_delete: marking element \"%s\" "
"for deletion\n",
flat_array->elements[i].index.str_value.str);
@}
@}
@end example
The sixth step is to release the flattened array. This tells
@command{gawk} that the extension is no longer using the array,
and that it should delete any elements marked for deletion.
@command{gawk} also frees any storage that was allocated,
so you should not use the pointer (@code{flat_array} in this
code) once you have called @code{release_flattened_array()}:
@example
if (! release_flattened_array(value2.array_cookie, flat_array)) @{
printf("dump_array_and_delete: could not release flattened array\n");
goto out;
@}
@end example
Finally, because everything was successful, the function sets the
return value to success, and returns:
@example
@group
make_number(1.0, result);
out:
return result;
@}
@end group
@end example
Here is the output from running this part of the test:
@example
pets has 5 elements
dump_array_and_delete: sym_lookup of pets passed
dump_array_and_delete: incoming size is 5
pets["1"] = "blacky"
pets["2"] = "rusty"
pets["3"] = "sophie"
dump_array_and_delete: marking element "3" for deletion
pets["4"] = "raincloud"
pets["5"] = "lucky"
dump_array_and_delete(pets) returned 1
dump_array_and_delete() did remove index "3"!
@end example
@node Creating Arrays
@subsubsection How To Create and Populate Arrays
Besides working with arrays created by @command{awk} code, you can
create arrays and populate them as you see fit, and then @command{awk}
code can access them and manipulate them.
There are two important points about creating arrays from extension code:
@itemize @value{BULLET}
@item
You must install a new array into @command{gawk}'s symbol
table immediately upon creating it. Once you have done so,
you can then populate the array.
@ignore
Strictly speaking, this is required only
for arrays that will have subarrays as elements; however it is
a good idea to always do this. This restriction may be relaxed
in a subsequent revision of the API.
@end ignore
Similarly, if installing a new array as a subarray of an existing array,
you must add the new array to its parent before adding any elements to it.
Thus, the correct way to build an array is to work ``top down.'' Create
the array, and immediately install it in @command{gawk}'s symbol table
using @code{sym_update()}, or install it as an element in a previously
existing array using @code{set_array_element()}. We show example code shortly.
@item
Due to @command{gawk} internals, after using @code{sym_update()} to install an array
into @command{gawk}, you have to retrieve the array cookie from the value
passed in to @command{sym_update()} before doing anything else with it, like so:
@example
awk_value_t val;
awk_array_t new_array;
new_array = create_array();
val.val_type = AWK_ARRAY;
val.array_cookie = new_array;
/* install array in the symbol table */
sym_update("array", & val);
new_array = val.array_cookie; /* YOU MUST DO THIS */
@end example
If installing an array as a subarray, you must also retrieve the value
of the array cookie after the call to @code{set_element()}.
@end itemize
The following C code is a simple test extension to create an array
with two regular elements and with a subarray. The leading @code{#include}
directives and boilerplate variable declarations
(@pxref{Extension API Boilerplate})
are omitted for brevity.
The first step is to create a new array and then install it
in the symbol table:
@example
@ignore
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <stdio.h>
#include <assert.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include "gawkapi.h"
static const gawk_api_t *api; /* for convenience macros to work */
static awk_ext_id_t ext_id;
static const char *ext_version = "testarray extension: version 1.0";
int plugin_is_GPL_compatible;
@end ignore
/* create_new_array --- create a named array */
static void
create_new_array()
@{
awk_array_t a_cookie;
awk_array_t subarray;
awk_value_t index, value;
a_cookie = create_array();
value.val_type = AWK_ARRAY;
value.array_cookie = a_cookie;
if (! sym_update("new_array", & value))
printf("create_new_array: sym_update(\"new_array\") failed!\n");
a_cookie = value.array_cookie;
@end example
@noindent
Note how @code{a_cookie} is reset from the @code{array_cookie} field in
the @code{value} structure.
The second step is to install two regular values into @code{new_array}:
@example
(void) make_const_string("hello", 5, & index);
(void) make_const_string("world", 5, & value);
if (! set_array_element(a_cookie, & index, & value)) @{
printf("fill_in_array: set_array_element failed\n");
return;
@}
(void) make_const_string("answer", 6, & index);
(void) make_number(42.0, & value);
if (! set_array_element(a_cookie, & index, & value)) @{
printf("fill_in_array: set_array_element failed\n");
return;
@}
@end example
The third step is to create the subarray and install it:
@example
(void) make_const_string("subarray", 8, & index);
subarray = create_array();
value.val_type = AWK_ARRAY;
value.array_cookie = subarray;
if (! set_array_element(a_cookie, & index, & value)) @{
printf("fill_in_array: set_array_element failed\n");
return;
@}
subarray = value.array_cookie;
@end example
The final step is to populate the subarray with its own element:
@example
(void) make_const_string("foo", 3, & index);
(void) make_const_string("bar", 3, & value);
if (! set_array_element(subarray, & index, & value)) @{
printf("fill_in_array: set_array_element failed\n");
return;
@}
@}
@ignore
static awk_ext_func_t func_table[] = @{
@{ NULL, NULL, 0 @}
@};
/* init_testarray --- additional initialization function */
static awk_bool_t init_testarray(void)
@{
create_new_array();
return awk_true;
@}
static awk_bool_t (*init_func)(void) = init_testarray;
dl_load_func(func_table, testarray, "")
@end ignore
@end example
Here is a sample script that loads the extension
and then dumps the array:
@example
@@load "subarray"
function dumparray(name, array, i)
@{
for (i in array)
if (isarray(array[i]))
dumparray(name "[\"" i "\"]", array[i])
else
printf("%s[\"%s\"] = %s\n", name, i, array[i])
@}
BEGIN @{
dumparray("new_array", new_array);
@}
@end example
Here is the result of running the script:
@example
$ @kbd{AWKLIBPATH=$PWD gawk -f subarray.awk}
@print{} new_array["subarray"]["foo"] = bar
@print{} new_array["hello"] = world
@print{} new_array["answer"] = 42
@end example
@noindent
(@xref{Finding Extensions} for more information on the
@env{AWKLIBPATH} environment variable.)
@node Redirection API
@subsection Accessing and Manipulating Redirections
The following function allows extensions to access and manipulate redirections.
@table @code
@item awk_bool_t get_file(const char *name,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ size_t name_len,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ const char *filetype,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ int fd,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ const awk_input_buf_t **ibufp,
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ const awk_output_buf_t **obufp);
Look up file @code{name} in @command{gawk}'s internal redirection table.
If @code{name} is @code{NULL} or @code{name_len} is zero, return
data for the currently open input file corresponding to @code{FILENAME}.
(This does not access the @code{filetype} argument, so that may be undefined).
If the file is not already open, attempt to open it.
The @code{filetype} argument must be zero-terminated and should be one of:
@table @code
@item ">"
A file opened for output.
@item ">>"
A file opened for append.
@item "<"
A file opened for input.
@item "|>"
A pipe opened for output.
@item "|<"
A pipe opened for input.
@item "|&"
A two-way coprocess.
@end table
On error, return @code{awk_false}. Otherwise, return
@code{awk_true}, and return additional information about the redirection
in the @code{ibufp} and @code{obufp} pointers.
For input redirections, the @code{*ibufp} value should be non-@code{NULL},
and @code{*obufp} should be @code{NULL}. For output redirections,
the @code{*obufp} value should be non-@code{NULL}, and @code{*ibufp}
should be @code{NULL}. For two-way coprocesses, both values should
be non-@code{NULL}.
In the usual case, the extension is interested in @code{(*ibufp)->fd}
and/or @code{fileno((*obufp)->fp)}. If the file is not already
open, and the @code{fd} argument is nonnegative, @command{gawk}
will use that file descriptor instead of opening the file in the
usual way. If @code{fd} is nonnegative, but the file exists already,
@command{gawk} ignores @code{fd} and returns the existing file. It is
the caller's responsibility to notice that neither the @code{fd} in
the returned @code{awk_input_buf_t} nor the @code{fd} in the returned
@code{awk_output_buf_t} matches the requested value.
Note that supplying a file descriptor is currently @emph{not} supported
for pipes. However, supplying a file descriptor should work for input,
output, append, and two-way (coprocess) sockets. If @code{filetype}
is two-way, @command{gawk} assumes that it is a socket! Note that in
the two-way case, the input and output file descriptors may differ.
To check for success, you must check whether either matches.
@end table
It is anticipated that this API function will be used to implement I/O
multiplexing and a socket library.
@node Extension API Variables
@subsection API Variables
The API provides two sets of variables. The first provides information
about the version of the API (both with which the extension was compiled,
and with which @command{gawk} was compiled). The second provides
information about how @command{gawk} was invoked.
@menu
* Extension Versioning:: API Version information.
* Extension GMP/MPFR Versioning:: Version information about GMP and MPFR.
* Extension API Informational Variables:: Variables providing information about
@command{gawk}'s invocation.
@end menu
@node Extension Versioning
@subsubsection API Version Constants and Variables
@cindex API @subentry version
@cindex extension API @subentry version number
The API provides both a ``major'' and a ``minor'' version number.
The API versions are available at compile time as C preprocessor defines
to support conditional compilation, and as enum constants to facilitate
debugging:
@float Table,gawk-api-version
@caption{gawk API version constants}
@multitable {@b{API Version}} {@code{gawk_api_major_version}} {@code{GAWK_API_MAJOR_VERSION}}
@headitem API Version @tab C Preprocessor Define @tab enum constant
@item Major @tab @code{gawk_api_major_version} @tab @code{GAWK_API_MAJOR_VERSION}
@item Minor @tab @code{gawk_api_minor_version} @tab @code{GAWK_API_MINOR_VERSION}
@end multitable
@end float
The minor version increases when new functions are added to the API. Such
new functions are always added to the end of the API @code{struct}.
The major version increases (and the minor version is reset to zero) if any
of the data types change size or member order, or if any of the existing
functions change signature.
It could happen that an extension may be compiled against one version
of the API but loaded by a version of @command{gawk} using a different
version. For this reason, the major and minor API versions of the
running @command{gawk} are included in the API @code{struct} as read-only
constant integers:
@table @code
@item api->major_version
The major version of the running @command{gawk}.
@item api->minor_version
The minor version of the running @command{gawk}.
@end table
It is up to the extension to decide if there are API incompatibilities.
Typically, a check like this is enough:
@example
if ( api->major_version != GAWK_API_MAJOR_VERSION
|| api->minor_version < GAWK_API_MINOR_VERSION) @{
fprintf(stderr, "foo_extension: version mismatch with gawk!\n");
fprintf(stderr, "\tmy version (%d, %d), gawk version (%d, %d)\n",
GAWK_API_MAJOR_VERSION, GAWK_API_MINOR_VERSION,
api->major_version, api->minor_version);
exit(1);
@}
@end example
Such code is included in the boilerplate @code{dl_load_func()} macro
provided in @file{gawkapi.h} (discussed in
@ref{Extension API Boilerplate}).
@node Extension GMP/MPFR Versioning
@subsubsection GMP and MPFR Version Information
The API also includes information about the versions of GMP and MPFR
with which the running @command{gawk} was compiled (if any).
They are included in the API @code{struct} as read-only
constant integers:
@table @code
@item api->gmp_major_version
The major version of the GMP library used to compile @command{gawk}.
@item api->gmp_minor_version
The minor version of the GMP library used to compile @command{gawk}.
@item api->mpfr_major_version
The major version of the MPFR library used to compile @command{gawk}.
@item api->mpfr_minor_version
The minor version of the MPFR library used to compile @command{gawk}.
@end table
These fields are set to zero if @command{gawk} was compiled without
MPFR support.
You can check if the versions of MPFR and GMP that you are using match those
of @command{gawk} with the following macro:
@table @code
@item check_mpfr_version(extension)
The @code{extension} is the extension id passed to all the other macros
and functions defined in @file{gawkapi.h}. If you have not included
the @code{<mpfr.h>} header file, then this macro will be defined to do nothing.
If you have included that file, then this macro compares the MPFR
and GMP major and minor versions against those of the library you are
compiling against. If your libraries are newer than @command{gawk}'s, it
produces a fatal error message.
The @code{dl_load_func()} macro (@pxref{Extension API Boilerplate})
calls @code{check_mpfr_version()}.
@end table
@node Extension API Informational Variables
@subsubsection Informational Variables
@cindex API @subentry informational variables
@cindex extension API @subentry informational variables
The API provides access to several variables that describe
whether the corresponding command-line options were enabled when
@command{gawk} was invoked. The variables are:
@table @code
@item do_debug
This variable is true if @command{gawk} was invoked with @option{--debug} option.
@item do_lint
This variable is true if @command{gawk} was invoked with @option{--lint} option.
@item do_mpfr
This variable is true if @command{gawk} was invoked with @option{--bignum} option.
@item do_profile
This variable is true if @command{gawk} was invoked with @option{--profile} option.
@item do_sandbox
This variable is true if @command{gawk} was invoked with @option{--sandbox} option.
@item do_traditional
This variable is true if @command{gawk} was invoked with @option{--traditional} option.
@end table
The value of @code{do_lint} can change if @command{awk} code
modifies the @code{LINT} predefined variable (@pxref{Built-in Variables}).
The others should not change during execution.
@node Extension API Boilerplate
@subsection Boilerplate Code
As mentioned earlier (@pxref{Extension Mechanism Outline}), the function
definitions as presented are really macros. To use these macros, your
extension must provide a small amount of boilerplate code (variables and
functions) toward the top of your source file, using predefined names
as described here. The boilerplate needed is also provided in comments
in the @file{gawkapi.h} header file:
@example
@group
/* Boilerplate code: */
int plugin_is_GPL_compatible;
static gawk_api_t *const api;
@end group
static awk_ext_id_t ext_id;
static const char *ext_version = NULL; /* or @dots{} = "some string" */
static awk_ext_func_t func_table[] = @{
@{ "name", do_name, 1, 0, awk_false, NULL @},
/* @dots{} */
@};
/* EITHER: */
static awk_bool_t (*init_func)(void) = NULL;
/* OR: */
static awk_bool_t
init_my_extension(void)
@{
@dots{}
@}
static awk_bool_t (*init_func)(void) = init_my_extension;
dl_load_func(func_table, some_name, "name_space_in_quotes")
@end example
These variables and functions are as follows:
@table @code
@item int plugin_is_GPL_compatible;
This asserts that the extension is compatible with
@ifclear FOR_PRINT
the GNU GPL (@pxref{Copying}).
@end ifclear
@ifset FOR_PRINT
the GNU GPL.
@end ifset
If your extension does not have this, @command{gawk}
will not load it (@pxref{Plugin License}).
@item static gawk_api_t *const api;
This global @code{static} variable should be set to point to
the @code{gawk_api_t} pointer that @command{gawk} passes to your
@code{dl_load()} function. This variable is used by all of the macros.
@item static awk_ext_id_t ext_id;
This global static variable should be set to the @code{awk_ext_id_t}
value that @command{gawk} passes to your @code{dl_load()} function.
This variable is used by all of the macros.
@item static const char *ext_version = NULL; /* or @dots{} = "some string" */
This global @code{static} variable should be set either
to @code{NULL}, or to point to a string giving the name and version of
your extension.
@item static awk_ext_func_t func_table[] = @{ @dots{} @};
This is an array of one or more @code{awk_ext_func_t} structures,
as described earlier (@pxref{Extension Functions}).
It can then be looped over for multiple calls to
@code{add_ext_func()}.
@c Use @var{OR} for docbook
@item static awk_bool_t (*init_func)(void) = NULL;
@itemx @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @var{OR}
@itemx static awk_bool_t init_my_extension(void) @{ @dots{} @}
@itemx static awk_bool_t (*init_func)(void) = init_my_extension;
If you need to do some initialization work, you should define a
function that does it (creates variables, opens files, etc.)
and then define the @code{init_func} pointer to point to your
function.
The function should return @code{awk_false} upon failure, or @code{awk_true}
if everything goes well.
If you don't need to do any initialization, define the pointer and
initialize it to @code{NULL}.
@item dl_load_func(func_table, some_name, "name_space_in_quotes")
This macro expands to a @code{dl_load()} function that performs
all the necessary initializations.
@end table
The point of all the variables and arrays is to let the
@code{dl_load()} function (from the @code{dl_load_func()}
macro) do all the standard work. It does the following:
@enumerate 1
@item
Check the API versions. If the extension major version does not match
@command{gawk}'s, or if the extension minor version is greater than
@command{gawk}'s, it prints a fatal error message and exits.
@item
Check the MPFR and GMP versions. If there is a mismatch, it prints
a fatal error message and exits.
@item
Load the functions defined in @code{func_table}.
If any of them fails to load, it prints a warning message but
continues on.
@item
If the @code{init_func} pointer is not @code{NULL}, call the
function it points to. If it returns @code{awk_false}, print a
warning message.
@item
If @code{ext_version} is not @code{NULL}, register
the version string with @command{gawk}.
@end enumerate
@node Changes from API V1
@subsection Changes From Version 1 of the API
The current API is @emph{not} binary compatible with version 1 of the API.
You will have to recompile your extensions in order to use them with
the current version of @command{gawk}.
Fortunately, at the possible expense of some compile-time warnings, the API remains
source-code--compatible with the previous API. The major differences are
the additional members in the @code{awk_ext_func_t} structure, and the
addition of the third argument to the C implementation function
(@pxref{Extension Functions}).
Here is a list of individual features that changed from version 1 to
version 2 of the API:
@itemize @bullet
@item
Numeric values can now have MPFR/MPZ variants
(@pxref{General Data Types}).
@item
There are new string types: @code{AWK_REGEX} and @code{AWK_STRNUM}
(@pxref{General Data Types}).
@item
The @code{ezalloc()} macro is new
(@pxref{Memory Allocation Functions}).
@item
The @code{awk_ext_func_t} structure changed. Instead of
@code{num_expected_args}, it now has @code{max_expected} and
@code{min_required}
(@pxref{Extension Functions}).
@item
For @code{get_record()}, an input parser can now specify field widths
(@pxref{Input Parsers}).
@item
Extensions can now produce nonfatal error messages
(@pxref{Printing Messages}).
@item
When flattening an array, you can now specify the index and value types
(@pxref{Array Functions}).
@item
The @code{get_file()} API is new
(@pxref{Redirection API}).
@end itemize
@node Finding Extensions
@section How @command{gawk} Finds Extensions
@cindex extensions @subentry loadable @subentry search path
@cindex finding extensions
Compiled extensions have to be installed in a directory where
@command{gawk} can find them. If @command{gawk} is configured and
built in the default fashion, the directory in which to find
extensions is @file{/usr/local/lib/gawk}. You can also specify a search
path with a list of directories to search for compiled extensions.
@xref{AWKLIBPATH Variable} for more information.
@node Extension Example
@section Example: Some File Functions
@cindex extensions @subentry loadable @subentry example
@quotation
@i{No matter where you go, there you are.}
@author Buckaroo Banzai
@end quotation
@c It's enough to show chdir and stat, no need for fts
Two useful functions that are not in @command{awk} are @code{chdir()} (so
that an @command{awk} program can change its directory) and @code{stat()}
(so that an @command{awk} program can gather information about a file).
In order to illustrate the API in action, this @value{SECTION} implements
these functions for @command{gawk} in an extension.
@menu
* Internal File Description:: What the new functions will do.
* Internal File Ops:: The code for internal file operations.
* Using Internal File Ops:: How to use an external extension.
@end menu
@node Internal File Description
@subsection Using @code{chdir()} and @code{stat()}
This @value{SECTION} shows how to use the new functions at
the @command{awk} level once they've been integrated into the
running @command{gawk} interpreter. Using @code{chdir()} is very
straightforward. It takes one argument, the new directory to change to:
@example
@@load "filefuncs"
@dots{}
newdir = "/home/arnold/funstuff"
ret = chdir(newdir)
if (ret < 0) @{
printf("could not change to %s: %s\n", newdir, ERRNO) > "/dev/stderr"
exit 1
@}
@dots{}
@end example
The return value is negative if the @code{chdir()} failed, and
@code{ERRNO} (@pxref{Built-in Variables}) is set to a string indicating
the error.
Using @code{stat()} is a bit more complicated. The C @code{stat()}
function fills in a structure that has a fair amount of information.
The right way to model this in @command{awk} is to fill in an associative
array with the appropriate information:
@c broke printf for page breaking
@example
file = "/home/arnold/.profile"
ret = stat(file, fdata)
if (ret < 0) @{
printf("could not stat %s: %s\n",
file, ERRNO) > "/dev/stderr"
exit 1
@}
printf("size of %s is %d bytes\n", file, fdata["size"])
@end example
The @code{stat()} function always clears the data array, even if
the @code{stat()} fails. It fills in the following elements:
@table @code
@item "name"
The name of the file that was @code{stat()}ed.
@item "dev"
@itemx "ino"
The file's device and inode numbers, respectively.
@item "mode"
The file's mode, as a numeric value. This includes both the file's
type and its permissions.
@item "nlink"
The number of hard links (directory entries) the file has.
@item "uid"
@itemx "gid"
The numeric user and group ID numbers of the file's owner.
@item "size"
The size in bytes of the file.
@item "blocks"
The number of disk blocks the file actually occupies. This may not
be a function of the file's size if the file has holes.
@item "atime"
@itemx "mtime"
@itemx "ctime"
The file's last access, modification, and inode update times,
respectively. These are numeric timestamps, suitable for formatting
with @code{strftime()}
(@pxref{Time Functions}).
@item "pmode"
The file's ``printable mode.'' This is a string representation of
the file's type and permissions, such as is produced by
@samp{ls -l}---for example, @code{"drwxr-xr-x"}.
@item "type"
A printable string representation of the file's type. The value
is one of the following:
@table @code
@item "blockdev"
@itemx "chardev"
The file is a block or character device (``special file'').
@ignore
@item "door"
The file is a Solaris ``door'' (special file used for
interprocess communications).
@end ignore
@item "directory"
The file is a directory.
@item "fifo"
The file is a named pipe (also known as a FIFO).
@item "file"
The file is just a regular file.
@item "socket"
The file is an @code{AF_UNIX} (``Unix domain'') socket in the
filesystem.
@item "symlink"
The file is a symbolic link.
@end table
@c 5/2013: Thanks to Corinna Vinschen for this information.
@item "devbsize"
The size of a block for the element indexed by @code{"blocks"}.
This information is derived from either the @code{DEV_BSIZE}
constant defined in @code{<sys/param.h>} on most systems,
or the @code{S_BLKSIZE} constant in @code{<sys/stat.h>} on BSD systems.
For some other systems, @dfn{a priori} knowledge is used to provide
a value. Where no value can be determined, it defaults to 512.
@end table
Several additional elements may be present, depending upon the operating
system and the type of the file. You can test for them in your @command{awk}
program by using the @code{in} operator
(@pxref{Reference to Elements}):
@table @code
@item "blksize"
The preferred block size for I/O to the file. This field is not
present on all POSIX-like systems in the C @code{stat} structure.
@item "linkval"
If the file is a symbolic link, this element is the name of the
file the link points to (i.e., the value of the link).
@item "rdev"
@itemx "major"
@itemx "minor"
If the file is a block or character device file, then these values
represent the numeric device number and the major and minor components
of that number, respectively.
@end table
@node Internal File Ops
@subsection C Code for @code{chdir()} and @code{stat()}
Here is the C code for these extensions.@footnote{This version is
edited slightly for presentation. See @file{extension/filefuncs.c}
in the @command{gawk} distribution for the complete version.}
The file includes a number of standard header files, and then includes
the @file{gawkapi.h} header file, which provides the API definitions.
Those are followed by the necessary variable declarations
to make use of the API macros and boilerplate code
(@pxref{Extension API Boilerplate}):
@example
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <stdio.h>
#include <assert.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include "gawkapi.h"
#include "gettext.h"
#define _(msgid) gettext(msgid)
#define N_(msgid) msgid
#include "gawkfts.h"
#include "stack.h"
static const gawk_api_t *api; /* for convenience macros to work */
static awk_ext_id_t ext_id;
static awk_bool_t init_filefuncs(void);
static awk_bool_t (*init_func)(void) = init_filefuncs;
static const char *ext_version = "filefuncs extension: version 1.0";
int plugin_is_GPL_compatible;
@end example
@cindex programming conventions @subentry @command{gawk} extensions
By convention, for an @command{awk} function @code{foo()}, the C function
that implements it is called @code{do_foo()}. The function should have
two arguments. The first is an @code{int}, usually called @code{nargs},
that represents the number of actual arguments for the function.
The second is a pointer to an @code{awk_value_t} structure, usually named
@code{result}:
@example
@group
/* do_chdir --- provide dynamically loaded chdir() function for gawk */
static awk_value_t *
do_chdir(int nargs, awk_value_t *result, struct awk_ext_func *unused)
@end group
@{
awk_value_t newdir;
int ret = -1;
assert(result != NULL);
@end example
The @code{newdir}
variable represents the new directory to change to, which is retrieved
with @code{get_argument()}. Note that the first argument is
numbered zero.
If the argument is retrieved successfully, the function calls the
@code{chdir()} system call. Otherwise, if the @code{chdir()} fails,
it updates @code{ERRNO}:
@example
if (get_argument(0, AWK_STRING, & newdir)) @{
ret = chdir(newdir.str_value.str);
if (ret < 0)
update_ERRNO_int(errno);
@}
@end example
Finally, the function returns the return value to the @command{awk} level:
@example
return make_number(ret, result);
@}
@end example
The @code{stat()} extension is more involved. First comes a function
that turns a numeric mode into a printable representation
(e.g., octal @code{0644} becomes @samp{-rw-r--r--}). This is omitted here for brevity:
@example
/* format_mode --- turn a stat mode field into something readable */
static char *
format_mode(unsigned long fmode)
@{
@dots{}
@}
@end example
Next comes a function for reading symbolic links, which is also
omitted here for brevity:
@example
/* read_symlink --- read a symbolic link into an allocated buffer.
@dots{} */
static char *
read_symlink(const char *fname, size_t bufsize, ssize_t *linksize)
@{
@dots{}
@}
@end example
Two helper functions simplify entering values in the
array that will contain the result of the @code{stat()}:
@example
/* array_set --- set an array element */
static void
array_set(awk_array_t array, const char *sub, awk_value_t *value)
@{
awk_value_t index;
set_array_element(array,
make_const_string(sub, strlen(sub), & index),
value);
@}
/* array_set_numeric --- set an array element with a number */
static void
array_set_numeric(awk_array_t array, const char *sub, double num)
@{
awk_value_t tmp;
array_set(array, sub, make_number(num, & tmp));
@}
@end example
The following function does most of the work to fill in
the @code{awk_array_t} result array with values obtained
from a valid @code{struct stat}. This work is done in a separate function
to support the @code{stat()} function for @command{gawk} and also
to support the @code{fts()} extension, which is included in
the same file but whose code is not shown here
(@pxref{Extension Sample File Functions}).
The first part of the function is variable declarations,
including a table to map file types to strings:
@example
/* fill_stat_array --- do the work to fill an array with stat info */
static int
fill_stat_array(const char *name, awk_array_t array, struct stat *sbuf)
@{
char *pmode; /* printable mode */
const char *type = "unknown";
awk_value_t tmp;
static struct ftype_map @{
unsigned int mask;
const char *type;
@} ftype_map[] = @{
@{ S_IFREG, "file" @},
@{ S_IFBLK, "blockdev" @},
@{ S_IFCHR, "chardev" @},
@{ S_IFDIR, "directory" @},
#ifdef S_IFSOCK
@{ S_IFSOCK, "socket" @},
#endif
#ifdef S_IFIFO
@{ S_IFIFO, "fifo" @},
#endif
#ifdef S_IFLNK
@{ S_IFLNK, "symlink" @},
#endif
#ifdef S_IFDOOR /* Solaris weirdness */
@{ S_IFDOOR, "door" @},
#endif
@};
int j, k;
@end example
The destination array is cleared, and then code fills in
various elements based on values in the @code{struct stat}:
@example
/* empty out the array */
clear_array(array);
/* fill in the array */
array_set(array, "name", make_const_string(name, strlen(name),
& tmp));
array_set_numeric(array, "dev", sbuf->st_dev);
array_set_numeric(array, "ino", sbuf->st_ino);
array_set_numeric(array, "mode", sbuf->st_mode);
array_set_numeric(array, "nlink", sbuf->st_nlink);
array_set_numeric(array, "uid", sbuf->st_uid);
array_set_numeric(array, "gid", sbuf->st_gid);
array_set_numeric(array, "size", sbuf->st_size);
array_set_numeric(array, "blocks", sbuf->st_blocks);
array_set_numeric(array, "atime", sbuf->st_atime);
array_set_numeric(array, "mtime", sbuf->st_mtime);
array_set_numeric(array, "ctime", sbuf->st_ctime);
/* for block and character devices, add rdev,
major and minor numbers */
if (S_ISBLK(sbuf->st_mode) || S_ISCHR(sbuf->st_mode)) @{
array_set_numeric(array, "rdev", sbuf->st_rdev);
array_set_numeric(array, "major", major(sbuf->st_rdev));
array_set_numeric(array, "minor", minor(sbuf->st_rdev));
@}
@end example
@noindent
The latter part of the function makes selective additions
to the destination array, depending upon the availability of
certain members and/or the type of the file. It then returns zero,
for success:
@example
@group
#ifdef HAVE_STRUCT_STAT_ST_BLKSIZE
array_set_numeric(array, "blksize", sbuf->st_blksize);
#endif
@end group
pmode = format_mode(sbuf->st_mode);
array_set(array, "pmode", make_const_string(pmode, strlen(pmode),
& tmp));
/* for symbolic links, add a linkval field */
if (S_ISLNK(sbuf->st_mode)) @{
char *buf;
ssize_t linksize;
if ((buf = read_symlink(name, sbuf->st_size,
& linksize)) != NULL)
array_set(array, "linkval",
make_malloced_string(buf, linksize, & tmp));
else
warning(ext_id, _("stat: unable to read symbolic link `%s'"),
name);
@}
/* add a type field */
type = "unknown"; /* shouldn't happen */
for (j = 0, k = sizeof(ftype_map)/sizeof(ftype_map[0]); j < k; j++) @{
if ((sbuf->st_mode & S_IFMT) == ftype_map[j].mask) @{
type = ftype_map[j].type;
break;
@}
@}
array_set(array, "type", make_const_string(type, strlen(type), & tmp));
return 0;
@}
@end example
The third argument to @code{stat()} was not discussed previously. This
argument is optional. If present, it causes @code{do_stat()} to use
the @code{stat()} system call instead of the @code{lstat()} system
call. This is done by using a function pointer: @code{statfunc}.
@code{statfunc} is initialized to point to @code{lstat()} (instead
of @code{stat()}) to get the file information, in case the file is a
symbolic link. However, if the third argument is included, @code{statfunc}
is set to point to @code{stat()}, instead.
Here is the @code{do_stat()} function, which starts with
variable declarations and argument checking:
@example
/* do_stat --- provide a stat() function for gawk */
static awk_value_t *
do_stat(int nargs, awk_value_t *result, struct awk_ext_func *unused)
@{
awk_value_t file_param, array_param;
char *name;
awk_array_t array;
int ret;
struct stat sbuf;
/* default is lstat() */
int (*statfunc)(const char *path, struct stat *sbuf) = lstat;
assert(result != NULL);
@end example
Then comes the actual work. First, the function gets the arguments.
Next, it gets the information for the file. If the called function
(@code{lstat()} or @code{stat()}) returns an error, the code sets
@code{ERRNO} and returns:
@example
/* file is first arg, array to hold results is second */
if ( ! get_argument(0, AWK_STRING, & file_param)
|| ! get_argument(1, AWK_ARRAY, & array_param)) @{
warning(ext_id, _("stat: bad parameters"));
return make_number(-1, result);
@}
if (nargs == 3) @{
statfunc = stat;
@}
name = file_param.str_value.str;
array = array_param.array_cookie;
/* always empty out the array */
clear_array(array);
/* stat the file; if error, set ERRNO and return */
ret = statfunc(name, & sbuf);
@group
if (ret < 0) @{
update_ERRNO_int(errno);
return make_number(ret, result);
@}
@end group
@end example
The tedious work is done by @code{fill_stat_array()}, shown
earlier. When done, the function returns the result from @code{fill_stat_array()}:
@example
@group
ret = fill_stat_array(name, array, & sbuf);
return make_number(ret, result);
@}
@end group
@end example
Finally, it's necessary to provide the ``glue'' that loads the
new function(s) into @command{gawk}.
The @code{filefuncs} extension also provides an @code{fts()}
function, which we omit here
(@pxref{Extension Sample File Functions}).
For its sake, there is an initialization
function:
@example
/* init_filefuncs --- initialization routine */
static awk_bool_t
init_filefuncs(void)
@{
@dots{}
@}
@end example
We are almost done. We need an array of @code{awk_ext_func_t}
structures for loading each function into @command{gawk}:
@example
static awk_ext_func_t func_table[] = @{
@{ "chdir", do_chdir, 1, 1, awk_false, NULL @},
@{ "stat", do_stat, 3, 2, awk_false, NULL @},
@dots{}
@};
@end example
Each extension must have a routine named @code{dl_load()} to load
everything that needs to be loaded. It is simplest to use the
@code{dl_load_func()} macro in @code{gawkapi.h}:
@example
/* define the dl_load() function using the boilerplate macro */
dl_load_func(func_table, filefuncs, "")
@end example
And that's it!
@node Using Internal File Ops
@subsection Integrating the Extensions
@cindex @command{gawk} @subentry interpreter, adding code to
Now that the code is written, it must be possible to add it at
runtime to the running @command{gawk} interpreter. First, the
code must be compiled. Assuming that the functions are in
a file named @file{filefuncs.c}, and @var{idir} is the location
of the @file{gawkapi.h} header file,
the following steps@footnote{In practice, you would probably want to
use the GNU Autotools (Automake, Autoconf, Libtool, and @command{gettext}) to
configure and build your libraries. Instructions for doing so are beyond
the scope of this @value{DOCUMENT}. @xref{gawkextlib} for Internet links to
the tools.} create a GNU/Linux shared library:
@example
$ @kbd{gcc -fPIC -shared -DHAVE_CONFIG_H -c -O -g -I@var{idir} filefuncs.c}
$ @kbd{gcc -o filefuncs.so -shared filefuncs.o}
@end example
Once the library exists, it is loaded by using the @code{@@load} keyword:
@example
# file testff.awk
@@load "filefuncs"
BEGIN @{
"pwd" | getline curdir # save current directory
close("pwd")
chdir("/tmp")
system("pwd") # test it
chdir(curdir) # go back
print "Info for testff.awk"
ret = stat("testff.awk", data)
print "ret =", ret
for (i in data)
printf "data[\"%s\"] = %s\n", i, data[i]
print "testff.awk modified:",
strftime("%m %d %Y %H:%M:%S", data["mtime"])
print "\nInfo for JUNK"
ret = stat("JUNK", data)
print "ret =", ret
for (i in data)
printf "data[\"%s\"] = %s\n", i, data[i]
print "JUNK modified:", strftime("%m %d %Y %H:%M:%S", data["mtime"])
@}
@end example
The @env{AWKLIBPATH} environment variable tells
@command{gawk} where to find extensions (@pxref{Finding Extensions}).
We set it to the current directory and run the program:
@example
$ @kbd{AWKLIBPATH=$PWD gawk -f testff.awk}
@print{} /tmp
@print{} Info for testff.awk
@print{} ret = 0
@print{} data["blksize"] = 4096
@print{} data["devbsize"] = 512
@print{} data["mtime"] = 1412004710
@print{} data["mode"] = 33204
@print{} data["type"] = file
@print{} data["dev"] = 2053
@print{} data["gid"] = 1000
@print{} data["ino"] = 10358899
@print{} data["ctime"] = 1412004710
@print{} data["blocks"] = 8
@print{} data["nlink"] = 1
@print{} data["name"] = testff.awk
@print{} data["atime"] = 1412004716
@print{} data["pmode"] = -rw-rw-r--
@print{} data["size"] = 666
@print{} data["uid"] = 1000
@print{} testff.awk modified: 09 29 2014 18:31:50
@print{}
@print{} Info for JUNK
@print{} ret = -1
@print{} JUNK modified: 01 01 1970 02:00:00
@end example
@node Extension Samples
@section The Sample Extensions in the @command{gawk} Distribution
@cindex extensions @subentry loadable @subentry distributed with @command{gawk}
This @value{SECTION} provides a brief overview of the sample extensions
that come in the @command{gawk} distribution. Some of them are intended
for production use (e.g., the @code{filefuncs}, @code{readdir}, and
@code{inplace} extensions). Others mainly provide example code that
shows how to use the extension API.
@menu
* Extension Sample File Functions:: The file functions sample.
* Extension Sample Fnmatch:: An interface to @code{fnmatch()}.
* Extension Sample Fork:: An interface to @code{fork()} and other
process functions.
* Extension Sample Inplace:: Enabling in-place file editing.
* Extension Sample Ord:: Character to value to character
conversions.
* Extension Sample Readdir:: An interface to @code{readdir()}.
* Extension Sample Revout:: Reversing output sample output wrapper.
* Extension Sample Rev2way:: Reversing data sample two-way processor.
* Extension Sample Read write array:: Serializing an array to a file.
* Extension Sample Readfile:: Reading an entire file into a string.
* Extension Sample Time:: An interface to @code{gettimeofday()}
and @code{sleep()}.
* Extension Sample API Tests:: Tests for the API.
@end menu
@node Extension Sample File Functions
@subsection File-Related Functions
The @code{filefuncs} extension provides three different functions, as follows.
The usage is:
@table @asis
@item @code{@@load "filefuncs"}
This is how you load the extension.
@cindex @code{chdir()} extension function
@item @code{result = chdir("/some/directory")}
The @code{chdir()} function is a direct hook to the @code{chdir()}
system call to change the current directory. It returns zero
upon success or a value less than zero upon error.
In the latter case, it updates @code{ERRNO}.
@cindex @code{stat()} extension function
@item @code{result = stat("/some/path", statdata} [@code{, follow}]@code{)}
The @code{stat()} function provides a hook into the
@code{stat()} system call.
It returns zero upon success or a value less than zero upon error.
In the latter case, it updates @code{ERRNO}.
By default, it uses the @code{lstat()} system call. However, if passed
a third argument, it uses @code{stat()} instead.
In all cases, it clears the @code{statdata} array.
When the call is successful, @code{stat()} fills the @code{statdata}
array with information retrieved from the filesystem, as follows:
@multitable @columnfractions .15 .50 .20
@headitem Subscript @tab Field in @code{struct stat} @tab File type
@item @code{"name"} @tab The @value{FN} @tab All
@item @code{"dev"} @tab @code{st_dev} @tab All
@item @code{"ino"} @tab @code{st_ino} @tab All
@item @code{"mode"} @tab @code{st_mode} @tab All
@item @code{"nlink"} @tab @code{st_nlink} @tab All
@item @code{"uid"} @tab @code{st_uid} @tab All
@item @code{"gid"} @tab @code{st_gid} @tab All
@item @code{"size"} @tab @code{st_size} @tab All
@item @code{"atime"} @tab @code{st_atime} @tab All
@item @code{"mtime"} @tab @code{st_mtime} @tab All
@item @code{"ctime"} @tab @code{st_ctime} @tab All
@item @code{"rdev"} @tab @code{st_rdev} @tab Device files
@item @code{"major"} @tab @code{st_major} @tab Device files
@item @code{"minor"} @tab @code{st_minor} @tab Device files
@item @code{"blksize"} @tab @code{st_blksize} @tab All
@item @code{"pmode"} @tab A human-readable version of the mode value, like that printed by
@command{ls} (for example, @code{"-rwxr-xr-x"}) @tab All
@item @code{"linkval"} @tab The value of the symbolic link @tab Symbolic links
@item @code{"type"} @tab The type of the file as a string---one of
@code{"file"},
@code{"blockdev"},
@code{"chardev"},
@code{"directory"},
@code{"socket"},
@code{"fifo"},
@code{"symlink"},
@code{"door"},
or
@code{"unknown"}
(not all systems support all file types) @tab All
@end multitable
@cindex @code{fts()} extension function
@item @code{flags = or(FTS_PHYSICAL, ...)}
@itemx @code{result = fts(pathlist, flags, filedata)}
Walk the file trees provided in @code{pathlist} and fill in the
@code{filedata} array, as described next. @code{flags} is the bitwise
OR of several predefined values, also described in a moment.
Return zero if there were no errors, otherwise return @minus{}1.
@end table
The @code{fts()} function provides a hook to the C library @code{fts()}
routines for traversing file hierarchies. Instead of returning data
about one file at a time in a stream, it fills in a multidimensional
array with data about each file and directory encountered in the requested
hierarchies.
The arguments are as follows:
@table @code
@item pathlist
An array of @value{FN}s. The element values are used; the index values are ignored.
@item flags
This should be the bitwise OR of one or more of the following
predefined constant flag values. At least one of
@code{FTS_LOGICAL} or @code{FTS_PHYSICAL} must be provided; otherwise
@code{fts()} returns an error value and sets @code{ERRNO}.
The flags are:
@c nested table
@table @code
@item FTS_LOGICAL
Do a ``logical'' file traversal, where the information returned for
a symbolic link refers to the linked-to file, and not to the symbolic
link itself. This flag is mutually exclusive with @code{FTS_PHYSICAL}.
@item FTS_PHYSICAL
Do a ``physical'' file traversal, where the information returned for a
symbolic link refers to the symbolic link itself. This flag is mutually
exclusive with @code{FTS_LOGICAL}.
@item FTS_NOCHDIR
As a performance optimization, the C library @code{fts()} routines
change directory as they traverse a file hierarchy. This flag disables
that optimization.
@item FTS_COMFOLLOW
Immediately follow a symbolic link named in @code{pathlist},
whether or not @code{FTS_LOGICAL} is set.
@item FTS_SEEDOT
By default, the C library @code{fts()} routines do not return entries for
@file{.} (dot) and @file{..} (dot-dot). This option causes entries for
dot-dot to also be included. (The extension always includes an entry
for dot; more on this in a moment.)
@item FTS_XDEV
During a traversal, do not cross onto a different mounted filesystem.
@end table
@item filedata
The @code{filedata} array holds the results.
@code{fts()} first clears it. Then it creates
an element in @code{filedata} for every element in @code{pathlist}.
The index is the name of the directory or file given in @code{pathlist}.
The element for this index is itself an array. There are two cases:
@c nested table
@table @emph
@item The path is a file
In this case, the array contains two or three elements:
@c doubly nested table
@table @code
@item "path"
The full path to this file, starting from the ``root'' that was given
in the @code{pathlist} array.
@item "stat"
This element is itself an array, containing the same information as provided
by the @code{stat()} function described earlier for its
@code{statdata} argument. The element may not be present if
the @code{stat()} system call for the file failed.
@item "error"
If some kind of error was encountered, the array will also
contain an element named @code{"error"}, which is a string describing the error.
@end table
@item The path is a directory
In this case, the array contains one element for each entry in the
directory. If an entry is a file, that element is the same as for files, just
described. If the entry is a directory, that element is (recursively)
an array describing the subdirectory. If @code{FTS_SEEDOT} was provided
in the flags, then there will also be an element named @code{".."}. This
element will be an array containing the data as provided by @code{stat()}.
In addition, there will be an element whose index is @code{"."}.
This element is an array containing the same two or three elements as
for a file: @code{"path"}, @code{"stat"}, and @code{"error"}.
@end table
@end table
The @code{fts()} function returns zero if there were no errors.
Otherwise, it returns @minus{}1.
@quotation NOTE
The @code{fts()} extension does not exactly mimic the
interface of the C library @code{fts()} routines, choosing instead to
provide an interface that is based on associative arrays, which is
more comfortable to use from an @command{awk} program. This includes the
lack of a comparison function, because @command{gawk} already provides
powerful array sorting facilities. Although an @code{fts_read()}-like
interface could have been provided, this felt less natural than simply
creating a multidimensional array to represent the file hierarchy and
its information.
@end quotation
See @file{test/fts.awk} in the @command{gawk} distribution for an example
use of the @code{fts()} extension function.
@node Extension Sample Fnmatch
@subsection Interface to @code{fnmatch()}
This extension provides an interface to the C library
@code{fnmatch()} function. The usage is:
@table @code
@item @@load "fnmatch"
This is how you load the extension.
@cindex @code{fnmatch()} extension function
@item result = fnmatch(pattern, string, flags)
The return value is zero on success, @code{FNM_NOMATCH}
if the string did not match the pattern, or
a different nonzero value if an error occurred.
@end table
In addition to the @code{fnmatch()} function, the @code{fnmatch} extension
adds one constant (@code{FNM_NOMATCH}), and an array of flag values
named @code{FNM}.
The arguments to @code{fnmatch()} are:
@table @code
@item pattern
The @value{FN} wildcard to match
@item string
The @value{FN} string
@item flag
Either zero, or the bitwise OR of one or more of the
flags in the @code{FNM} array
@end table
The flags are as follows:
@multitable @columnfractions .25 .75
@headitem Array element @tab Corresponding flag defined by @code{fnmatch()}
@item @code{FNM["CASEFOLD"]} @tab @code{FNM_CASEFOLD}
@item @code{FNM["FILE_NAME"]} @tab @code{FNM_FILE_NAME}
@item @code{FNM["LEADING_DIR"]} @tab @code{FNM_LEADING_DIR}
@item @code{FNM["NOESCAPE"]} @tab @code{FNM_NOESCAPE}
@item @code{FNM["PATHNAME"]} @tab @code{FNM_PATHNAME}
@item @code{FNM["PERIOD"]} @tab @code{FNM_PERIOD}
@end multitable
Here is an example:
@example
@@load "fnmatch"
@dots{}
flags = or(FNM["PERIOD"], FNM["NOESCAPE"])
if (fnmatch("*.a", "foo.c", flags) == FNM_NOMATCH)
print "no match"
@end example
@node Extension Sample Fork
@subsection Interface to @code{fork()}, @code{wait()}, and @code{waitpid()}
The @code{fork} extension adds three functions, as follows:
@table @code
@item @@load "fork"
This is how you load the extension.
@cindex @code{fork()} extension function
@item pid = fork()
This function creates a new process. The return value is zero in the
child and the process ID number of the child in the parent, or @minus{}1
upon error. In the latter case, @code{ERRNO} indicates the problem.
In the child, @code{PROCINFO["pid"]} and @code{PROCINFO["ppid"]} are
updated to reflect the correct values.
@cindex @code{waitpid()} extension function
@item ret = waitpid(pid)
This function takes a numeric argument, which is the process ID to
wait for. The return value is that of the
@code{waitpid()} system call.
@cindex @code{wait()} extension function
@item ret = wait()
This function waits for the first child to die.
The return value is that of the
@code{wait()} system call.
@end table
There is no corresponding @code{exec()} function.
Here is an example:
@example
@@load "fork"
@dots{}
if ((pid = fork()) == 0)
print "hello from the child"
else
print "hello from the parent"
@end example
@node Extension Sample Inplace
@subsection Enabling In-Place File Editing
@cindex @code{inplace} extension
The @code{inplace} extension emulates GNU @command{sed}'s @option{-i} option,
which performs ``in-place'' editing of each input file.
It uses the bundled @file{inplace.awk} include file to invoke the extension
properly. This extension makes use of the namespace facility to place
all the variables and functions in the @code{inplace} namespace
(@pxref{Namespaces}):
@example
@c file eg/lib/inplace.awk
@group
# inplace --- load and invoke the inplace extension.
@c endfile
@ignore
@c file eg/lib/inplace.awk
#
# Copyright (C) 2013, 2017, 2019 the Free Software Foundation, Inc.
#
# This file is part of GAWK, the GNU implementation of the
# AWK Programming Language.
#
# GAWK is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# GAWK is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
#
# Andrew J. Schorr, aschorr@@telemetry-investments.com
# January 2013
#
# Revised for namespaces
# Arnold Robbins, arnold@@skeeve.com
# July 2017
# June 2019, add backwards compatibility
@c endfile
@end ignore
@c file eg/lib/inplace.awk
@@load "inplace"
# Please set inplace::suffix to make a backup copy. For example, you may
# want to set inplace::suffix to .bak on the command line or in a BEGIN rule.
# Before there were namespaces in gawk, this extension used
# INPLACE_SUFFIX as the variable for making backup copies. We allow this
# too, so that any code that used the previous version continues to work.
# By default, each filename on the command line will be edited inplace.
# But you can selectively disable this by adding an inplace::enable=0 argument
# prior to files that you do not want to process this way. You can then
# reenable it later on the commandline by putting inplace::enable=1 before files
# that you wish to be subject to inplace editing.
# N.B. We call inplace::end() in the BEGINFILE and END rules so that any
# actions in an ENDFILE rule will be redirected as expected.
@@namespace "inplace"
@end group
@group
BEGIN @{
enable = 1 # enabled by default
@}
@end group
@group
BEGINFILE @{
sfx = (suffix ? suffix : awk::INPLACE_SUFFIX)
if (filename != "")
end(filename, sfx)
if (enable)
begin(filename = FILENAME, sfx)
else
filename = ""
@}
@end group
@group
END @{
if (filename != "")
end(filename, (suffix ? suffix : awk::INPLACE_SUFFIX))
@}
@end group
@c endfile
@end example
For each regular file that is processed, the extension redirects
standard output to a temporary file configured to have the same owner
and permissions as the original. After the file has been processed,
the extension restores standard output to its original destination.
If @code{inplace::suffix} is not an empty string, the original file is
linked to a backup @value{FN} created by appending that suffix. Finally,
the temporary file is renamed to the original @value{FN}.
Note that the use of this feature can be controlled by placing
@samp{inplace::enable=0} on the command-line prior to listing files that
should not be processed this way. You can reenable inplace editing by adding
an @samp{inplace::enable=1} argument prior to files that should be subject
to inplace editing.
The @code{inplace::filename} variable serves to keep track of the
current filename so as to not invoke @code{inplace::end()} before
processing the first file.
If any error occurs, the extension issues a fatal error to terminate
processing immediately without damaging the original file.
Here are some simple examples:
@example
$ @kbd{gawk -i inplace '@{ gsub(/foo/, "bar") @}; @{ print @}' file1 file2 file3}
@end example
To keep a backup copy of the original files, try this:
@example
$ @kbd{gawk -i inplace -v inplace::suffix=.bak '@{ gsub(/foo/, "bar") @}}
> @kbd{@{ print @}' file1 file2 file3}
@end example
Please note that, while the extension does attempt to preserve ownership and permissions, it makes no attempt to copy the ACLs from the original file.
If the program dies prematurely, as might happen if an unhandled signal is received, a temporary file may be left behind.
@node Extension Sample Ord
@subsection Character and Numeric values: @code{ord()} and @code{chr()}
The @code{ordchr} extension adds two functions, named
@code{ord()} and @code{chr()}, as follows:
@table @code
@item @@load "ordchr"
This is how you load the extension.
@cindex @code{ord()} extension function
@item number = ord(string)
Return the numeric value of the first character in @code{string}.
@cindex @code{chr()} extension function
@item char = chr(number)
Return a string whose first character is that represented by @code{number}.
@end table
These functions are inspired by the Pascal language functions
of the same name. Here is an example:
@example
@@load "ordchr"
@dots{}
printf("The numeric value of 'A' is %d\n", ord("A"))
printf("The string value of 65 is %s\n", chr(65))
@end example
@node Extension Sample Readdir
@subsection Reading Directories
The @code{readdir} extension adds an input parser for directories.
The usage is as follows:
@cindex @code{readdir} extension
@example
@@load "readdir"
@end example
When this extension is in use, instead of skipping directories named
on the command line (or with @code{getline}),
they are read, with each entry returned as a record.
The record consists of three fields. The first two are the inode number and the
@value{FN}, separated by a forward slash character.
On systems where the directory entry contains the file type, the record
has a third field (also separated by a slash), which is a single letter
indicating the type of the file. The letters and their corresponding file
types are shown in @ref{table-readdir-file-types}.
@float Table,table-readdir-file-types
@caption{File types returned by the @code{readdir} extension}
@multitable @columnfractions .1 .9
@headitem Letter @tab File type
@item @code{b} @tab Block device
@item @code{c} @tab Character device
@item @code{d} @tab Directory
@item @code{f} @tab Regular file
@item @code{l} @tab Symbolic link
@item @code{p} @tab Named pipe (FIFO)
@item @code{s} @tab Socket
@item @code{u} @tab Anything else (unknown)
@end multitable
@end float
On systems without the file type information, the third field is always
@samp{u}.
@quotation NOTE
On GNU/Linux systems, there are filesystems that don't support the
@code{d_type} entry (see the @i{readdir}(3) manual page), and so the file
type is always @samp{u}. You can use the @code{filefuncs} extension to call
@code{stat()} in order to get correct type information.
@end quotation
By default, if a directory cannot be opened (due to permission problems,
for example), @command{gawk} will exit. As with regular files, this
situation can be handled using a @code{BEGINFILE} rule that checks
@code{ERRNO} and prints an error or otherwise handles the problem.
Here is an example:
@example
@@load "readdir"
@dots{}
BEGIN @{ FS = "/" @}
@{ print "@value{FN} is", $2 @}
@end example
@node Extension Sample Revout
@subsection Reversing Output
The @code{revoutput} extension adds a simple output wrapper that reverses
the characters in each output line. Its main purpose is to show how to
write an output wrapper, although it may be mildly amusing for the unwary.
Here is an example:
@cindex @code{revoutput} extension
@example
@@load "revoutput"
BEGIN @{
REVOUT = 1
print "don't panic" > "/dev/stdout"
@}
@end example
The output from this program is @samp{cinap t'nod}.
@node Extension Sample Rev2way
@subsection Two-Way I/O Example
The @code{revtwoway} extension adds a simple two-way processor that
reverses the characters in each line sent to it for reading back by
the @command{awk} program. Its main purpose is to show how to write
a two-way processor, although it may also be mildly amusing.
The following example shows how to use it:
@cindex @code{revtwoway} extension
@example
@@load "revtwoway"
BEGIN @{
cmd = "/magic/mirror"
print "don't panic" |& cmd
cmd |& getline result
print result
close(cmd)
@}
@end example
The output from this program
@ifnotinfo
also is:
@end ifnotinfo
@ifinfo
is:
@end ifinfo
@samp{cinap t'nod}.
@node Extension Sample Read write array
@subsection Dumping and Restoring an Array
The @code{rwarray} extension adds two functions,
named @code{writea()} and @code{reada()}, as follows:
@table @code
@item @@load "rwarray"
This is how you load the extension.
@cindex @code{writea()} extension function
@item ret = writea(file, array)
This function takes a string argument, which is the name of the file
to which to dump the array, and the array itself as the second argument.
@code{writea()} understands arrays of arrays. It returns one on
success, or zero upon failure.
@cindex @code{reada()} extension function
@item ret = reada(file, array)
@code{reada()} is the inverse of @code{writea()};
it reads the file named as its first argument, filling in
the array named as the second argument. It clears the array first.
Here too, the return value is one on success, or zero upon failure.
@end table
The array created by @code{reada()} is identical to that written by
@code{writea()} in the sense that the contents are the same. However,
due to implementation issues, the array traversal order of the re-created
array is likely to be different from that of the original array. As array
traversal order in @command{awk} is by default undefined, this is (technically)
not a problem. If you need to guarantee a particular traversal
order, use the array sorting features in @command{gawk} to do so
(@pxref{Array Sorting}).
The file contains binary data. All integral values are written in network
byte order. However, double-precision floating-point values are written
as native binary data. Thus, arrays containing only string data can
theoretically be dumped on systems with one byte order and restored on
systems with a different one, but this has not been tried.
Here is an example:
@example
@@load "rwarray"
@dots{}
ret = writea("arraydump.bin", array)
@dots{}
ret = reada("arraydump.bin", array)
@end example
@node Extension Sample Readfile
@subsection Reading an Entire File
The @code{readfile} extension adds a single function
named @code{readfile()}, and an input parser:
@table @code
@item @@load "readfile"
This is how you load the extension.
@cindex @code{readfile()} extension function
@item result = readfile("/some/path")
The argument is the name of the file to read. The return value is a
string containing the entire contents of the requested file. Upon error,
the function returns the empty string and sets @code{ERRNO}.
@item BEGIN @{ PROCINFO["readfile"] = 1 @}
In addition, the extension adds an input parser that is activated if
@code{PROCINFO["readfile"]} exists.
When activated, each input file is returned in its entirety as @code{$0}.
@code{RT} is set to the null string.
@end table
Here is an example:
@example
@@load "readfile"
@dots{}
contents = readfile("/path/to/file");
if (contents == "" && ERRNO != "") @{
print("problem reading file", ERRNO) > "/dev/stderr"
...
@}
@end example
@node Extension Sample Time
@subsection Extension Time Functions
@quotation CAUTION
As @command{gawk} @value{PVERSION} 5.1.0, this extension is considered to be obsolete.
It is replaced by the @code{timex} extension in @code{gawkextlib}
(@pxref{gawkextlib}).
For @value{PVERSION} 5.1, no warning will be issued if this extension is used.
For the next major release, a warning will be issued. In the release after that
this extension will be removed from the distribution.
@end quotation
The @code{time} extension adds two functions, named @code{gettimeofday()}
and @code{sleep()}, as follows:
@table @code
@item @@load "time"
This is how you load the extension.
@cindex @code{gettimeofday()} extension function
@item the_time = gettimeofday()
Return the time in seconds that has elapsed since 1970-01-01 UTC as a
floating-point value. If the time is unavailable on this platform, return
@minus{}1 and set @code{ERRNO}. The returned time should have sub-second
precision, but the actual precision may vary based on the platform.
If the standard C @code{gettimeofday()} system call is available on this
platform, then it simply returns the value. Otherwise, if on MS-Windows,
it tries to use @code{GetSystemTimeAsFileTime()}.
@cindex @code{sleep()} extension function
@item result = sleep(@var{seconds})
Attempt to sleep for @var{seconds} seconds. If @var{seconds} is negative,
or the attempt to sleep fails, return @minus{}1 and set @code{ERRNO}.
Otherwise, return zero after sleeping for the indicated amount of time.
Note that @var{seconds} may be a floating-point (nonintegral) value.
Implementation details: depending on platform availability, this function
tries to use @code{nanosleep()} or @code{select()} to implement the delay.
@end table
@node Extension Sample API Tests
@subsection API Tests
@cindex @code{testext} extension
The @code{testext} extension exercises parts of the extension API that
are not tested by the other samples. The @file{extension/testext.c}
file contains both the C code for the extension and @command{awk}
test code inside C comments that run the tests. The testing framework
extracts the @command{awk} code and runs the tests. See the source file
for more information.
@node gawkextlib
@section The @code{gawkextlib} Project
@cindex extensions @subentry loadable @subentry @code{gawkextlib} project
@cindex @code{gawkextlib} project
The @uref{https://sourceforge.net/projects/gawkextlib/, @code{gawkextlib}}
project provides a number of @command{gawk} extensions, including one for
processing XML files. This is the evolution of the original @command{xgawk}
(XML @command{gawk}) project.
There are a number of extensions. Some of the more interesting ones are:
@itemize @value{BULLET}
@item
@code{abort} extension. It allows you to exit immediately from your
@command{awk} program without running the @code{END} rules.
@item
@code{json} extension.
This serializes a multidimensional array into a JSON string, and
can deserialize a JSON string into a @command{gawk} array.
This extension is interesting since it is written in C++ instead of C.
@item
MPFR library extension.
This provides access to a number of MPFR functions that @command{gawk}'s
native MPFR support does not.
@item
Select extension. It provides functionality based on the
@code{select()} system call.
@item
XML parser extension, using the @uref{https://expat.sourceforge.net, Expat}
XML parsing library
@end itemize
@cindex @command{git} utility
You can check out the code for the @code{gawkextlib} project
using the @uref{https://git-scm.com, Git} distributed source
code control system. The command is as follows:
@example
git clone git://git.code.sf.net/p/gawkextlib/code gawkextlib-code
@end example
@cindex RapidJson JSON parser library
You will need to have the @uref{http://www.rapidjson.org, RapidJson}
JSON parser library installed in order to build and use the @code{json} extension.
@cindex Expat XML parser library
You will need to have the @uref{https://expat.sourceforge.net, Expat}
XML parser library installed in order to build and use the XML extension.
In addition, you must have the GNU Autotools installed
(@uref{https://www.gnu.org/software/autoconf, Autoconf},
@uref{https://www.gnu.org/software/automake, Automake},
@uref{https://www.gnu.org/software/libtool, Libtool},
and
@uref{https://www.gnu.org/software/gettext, GNU @command{gettext}}).
The simple recipe for building and testing @code{gawkextlib} is as follows.
First, build and install @command{gawk}:
@example
cd .../path/to/gawk/code
./configure --prefix=/tmp/newgawk @ii{Install in /tmp/newgawk for now}
make && make check @ii{Build and check that all is OK}
make install @ii{Install gawk}
@end example
Next, go to @url{https://sourceforge.net/projects/gawkextlib/files} to
download @code{gawkextlib} and any extensions that you would like to build.
The @file{README} file at that site explains how to build the code. If you
installed @command{gawk} in a non-standard location, you will need to
specify @code{./configure --with-gawk=@var{/path/to/gawk}} to find it.
You may need to use the @command{sudo} utility
to install both @command{gawk} and @code{gawkextlib}, depending upon
how your system works.
If you write an extension that you wish to share with other
@command{gawk} users, consider doing so through the
@code{gawkextlib} project.
See the project's website for more information.
@node Extension summary
@section Summary
@itemize @value{BULLET}
@item
You can write extensions (sometimes called plug-ins) for @command{gawk}
in C or C++ using the application programming interface (API) defined
by the @command{gawk} developers.
@item
Extensions must have a license compatible with the GNU General Public
License (GPL), and they must assert that fact by declaring a variable
named @code{plugin_is_GPL_compatible}.
@item
Communication between @command{gawk} and an extension is two-way.
@command{gawk} passes a @code{struct} to the extension that contains
various data fields and function pointers. The extension can then call
into @command{gawk} via the supplied function pointers to accomplish
certain tasks.
@item
One of these tasks is to ``register'' the name and implementation of
new @command{awk}-level functions with @command{gawk}. The implementation
takes the form of a C function pointer with a defined signature.
By convention, implementation functions are named @code{do_@var{XXXX}()}
for some @command{awk}-level function @code{@var{XXXX}()}.
@item
The API is defined in a header file named @file{gawkapi.h}. You must include
a number of standard header files @emph{before} including it in your source file.
@item
API function pointers are provided for the following kinds of operations:
@itemize @value{BULLET}
@item
Allocating, reallocating, and releasing memory
@item
Registration functions (you may register
extension functions,
exit callbacks,
a version string,
input parsers,
output wrappers,
and two-way processors)
@item
Printing fatal, nonfatal, warning, and ``lint'' warning messages
@item
Updating @code{ERRNO}, or unsetting it
@item
Accessing parameters, including converting an undefined parameter into
an array
@item
Symbol table access (retrieving a global variable, creating one,
or changing one)
@item
Creating and releasing cached values; this provides an
efficient way to use values for multiple variables and
can be a big performance win
@item
Manipulating arrays
(retrieving, adding, deleting, and modifying elements;
getting the count of elements in an array;
creating a new array;
clearing an array;
and
flattening an array for easy C-style looping over all its indices and elements)
@end itemize
@item
The API defines a number of standard data types for representing
@command{awk} values, array elements, and arrays.
@item
The API provides convenience functions for constructing values.
It also provides memory management functions to ensure compatibility
between memory allocated by @command{gawk} and memory allocated by an
extension.
@item
@emph{All} memory passed from @command{gawk} to an extension must be
treated as read-only by the extension.
@item
@emph{All} memory passed from an extension to @command{gawk} must come from
the API's memory allocation functions. @command{gawk} takes responsibility for
the memory and releases it when appropriate.
@item
The API provides information about the running version of @command{gawk} so
that an extension can make sure it is compatible with the @command{gawk}
that loaded it.
@item
It is easiest to start a new extension by copying the boilerplate code
described in this @value{CHAPTER}. Macros in the @file{gawkapi.h} header
file make this easier to do.
@item
The @command{gawk} distribution includes a number of small but useful
sample extensions. The @code{gawkextlib} project includes several more
(larger) extensions. If you wish to write an extension and contribute it
to the community of @command{gawk} users, the @code{gawkextlib} project
is the place to do so.
@end itemize
@c EXCLUDE START
@node Extension Exercises
@section Exercises
@enumerate
@item
Add functions to implement system calls such as @code{chown()},
@code{chmod()}, and @code{umask()} to the file operations extension
presented in @ref{Internal File Ops}.
@c Idea from comp.lang.awk, February 2015
@item
Write an input parser that prints a prompt if the input is
a from a ``terminal'' device. You can use the @code{isatty()}
function to tell if the input file is a terminal. (Hint: this function
is usually expensive to call; try to call it just once.)
The content of the prompt should come from a variable settable
by @command{awk}-level code.
You can write the prompt to standard error. However,
for best results, open a new file descriptor (or file pointer)
on @file{/dev/tty} and print the prompt there, in case standard
error has been redirected.
Why is standard error a better
choice than standard output for writing the prompt?
Which reading mechanism should you replace, the one to get
a record, or the one to read raw bytes?
@item
Write a wrapper script that provides an interface similar to
@samp{sed -i} for the ``inplace'' extension presented in
@ref{Extension Sample Inplace}.
@end enumerate
@c EXCLUDE END
@ifnotinfo
@part @value{PART4}Appendices
@end ifnotinfo
@ifdocbook
@ifclear FOR_PRINT
Part IV contains the appendices (including the two licenses that cover
the @command{gawk} source code and this @value{DOCUMENT}, respectively)
and the Glossary:
@end ifclear
@ifset FOR_PRINT
Part IV contains three appendices, the last of which is the license that
covers the @command{gawk} source code:
@end ifset
@itemize @value{BULLET}
@item
@ref{Language History}
@item
@ref{Installation}
@ifclear FOR_PRINT
@item
@ref{Notes}
@item
@ref{Basic Concepts}
@item
@ref{Glossary}
@end ifclear
@item
@ref{Copying}
@ifclear FOR_PRINT
@item
@ref{GNU Free Documentation License}
@end ifclear
@end itemize
@end ifdocbook
@node Language History
@appendix The Evolution of the @command{awk} Language
This @value{DOCUMENT} describes the GNU implementation of @command{awk},
which follows the POSIX specification. Many longtime @command{awk}
users learned @command{awk} programming with the original @command{awk}
implementation in Version 7 Unix. (This implementation was the basis for
@command{awk} in Berkeley Unix, through 4.3-Reno. Subsequent versions
of Berkeley Unix, and, for a while, some systems derived from 4.4BSD-Lite, used various
versions of @command{gawk} for their @command{awk}.) This @value{CHAPTER}
briefly describes the evolution of the @command{awk} language, with
cross-references to other parts of the @value{DOCUMENT} where you can
find more information.
@ifset FOR_PRINT
To save space, we have omitted
information on the history of features in @command{gawk} from this
edition. You can find it in the
@uref{https://www.gnu.org/software/gawk/manual/html_node/Feature-History.html,
online documentation}.
@end ifset
@menu
* V7/SVR3.1:: The major changes between V7 and System V
Release 3.1.
* SVR4:: Minor changes between System V Releases 3.1
and 4.
* POSIX:: New features from the POSIX standard.
* BTL:: New features from Brian Kernighan's version of
@command{awk}.
* POSIX/GNU:: The extensions in @command{gawk} not in POSIX
@command{awk}.
* Feature History:: The history of the features in @command{gawk}.
* Common Extensions:: Common Extensions Summary.
* Ranges and Locales:: How locales used to affect regexp ranges.
* Contributors:: The major contributors to @command{gawk}.
* History summary:: History summary.
@end menu
@node V7/SVR3.1
@appendixsec Major Changes Between V7 and SVR3.1
@cindex @command{awk} @subentry versions of
@cindex @command{awk} @subentry versions of @subentry changes between V7 and SVR3.1
The @command{awk} language evolved considerably between the release of
Version 7 Unix (1978) and the new version that was first made generally available in
System V Release 3.1 (1987). This @value{SECTION} summarizes the changes, with
cross-references to further details:
@itemize @value{BULLET}
@item
The requirement for @samp{;} to separate rules on a line
(@pxref{Statements/Lines})
@item
User-defined functions and the @code{return} statement
(@pxref{User-defined})
@item
The @code{delete} statement (@pxref{Delete})
@item
The @code{do}-@code{while} statement
(@pxref{Do Statement})
@item
The built-in functions @code{atan2()}, @code{cos()}, @code{sin()}, @code{rand()}, and
@code{srand()} (@pxref{Numeric Functions})
@item
The built-in functions @code{gsub()}, @code{sub()}, and @code{match()}
(@pxref{String Functions})
@item
The built-in functions @code{close()} and @code{system()}
(@pxref{I/O Functions})
@item
The @code{ARGC}, @code{ARGV}, @code{FNR}, @code{RLENGTH}, @code{RSTART},
and @code{SUBSEP} predefined variables (@pxref{Built-in Variables})
@item
Assignable @code{$0} (@pxref{Changing Fields})
@item
The conditional expression using the ternary operator @samp{?:}
(@pxref{Conditional Exp})
@item
The expression @samp{@var{indx} in @var{array}} outside of @code{for}
statements (@pxref{Reference to Elements})
@item
The exponentiation operator @samp{^}
(@pxref{Arithmetic Ops}) and its assignment operator
form @samp{^=} (@pxref{Assignment Ops})
@item
C-compatible operator precedence, which breaks some old @command{awk}
programs (@pxref{Precedence})
@item
Regexps as the value of @code{FS}
(@pxref{Field Separators}) and as the
third argument to the @code{split()} function
(@pxref{String Functions}), rather than using only the first character
of @code{FS}
@item
Dynamic regexps as operands of the @samp{~} and @samp{!~} operators
(@pxref{Computed Regexps})
@item
The escape sequences @samp{\b}, @samp{\f}, and @samp{\r}
(@pxref{Escape Sequences})
@item
Redirection of input for the @code{getline} function
(@pxref{Getline})
@item
Multiple @code{BEGIN} and @code{END} rules
(@pxref{BEGIN/END})
@item
Multidimensional arrays
(@pxref{Multidimensional})
@end itemize
@node SVR4
@appendixsec Changes Between SVR3.1 and SVR4
@cindex @command{awk} @subentry versions of @subentry changes between SVR3.1 and SVR4
The System V Release 4 (1989) version of Unix @command{awk} added these features
(some of which originated in @command{gawk}):
@itemize @value{BULLET}
@item
The @code{ENVIRON} array (@pxref{Built-in Variables})
@c gawk and MKS awk
@item
Multiple @option{-f} options on the command line
(@pxref{Options})
@c MKS awk
@item
The @option{-v} option for assigning variables before program execution begins
(@pxref{Options})
@c GNU, Bell Laboratories & MKS together
@item
The @option{--} signal for terminating command-line options
@item
The @samp{\a}, @samp{\v}, and @samp{\x} escape sequences
(@pxref{Escape Sequences})
@c GNU, for ANSI C compat
@item
A defined return value for the @code{srand()} built-in function
(@pxref{Numeric Functions})
@item
The @code{toupper()} and @code{tolower()} built-in string functions
for case translation
(@pxref{String Functions})
@item
A cleaner specification for the @samp{%c} format-control letter in the
@code{printf} function
(@pxref{Control Letters})
@item
The ability to dynamically pass the field width and precision (@code{"%*.*d"})
in the argument list of @code{printf} and @code{sprintf()}
(@pxref{Control Letters})
@item
The use of regexp constants, such as @code{/foo/}, as expressions, where
they are equivalent to using the matching operator, as in @samp{$0 ~ /foo/}
(@pxref{Using Constant Regexps})
@item
Processing of escape sequences inside command-line variable assignments
(@pxref{Assignment Options})
@end itemize
@node POSIX
@appendixsec Changes Between SVR4 and POSIX @command{awk}
@cindex @command{awk} @subentry versions of @subentry changes between SVR4 and POSIX @command{awk}
@cindex POSIX @command{awk} @subentry changes in @command{awk} versions
The POSIX Command Language and Utilities standard for @command{awk} (1992)
introduced the following changes into the language:
@itemize @value{BULLET}
@item
The use of @option{-W} for implementation-specific options
(@pxref{Options})
@item
The use of @code{CONVFMT} for controlling the conversion of numbers
to strings (@pxref{Conversion})
@item
The concept of a numeric string and tighter comparison rules to go
with it (@pxref{Typing and Comparison})
@item
The use of predefined variables as function parameter names is forbidden
(@pxref{Definition Syntax})
@item
More complete documentation of many of the previously undocumented
features of the language
@end itemize
In 2012, a number of extensions that had been commonly available for
many years were finally added to POSIX. They are:
@itemize @value{BULLET}
@item
The @code{fflush()} built-in function for flushing buffered output
(@pxref{I/O Functions})
@item
The @code{nextfile} statement
(@pxref{Nextfile Statement})
@item
The ability to delete all of an array at once with @samp{delete @var{array}}
(@pxref{Delete})
@end itemize
@xref{Common Extensions} for a list of common extensions
not permitted by the POSIX standard.
The 2018 POSIX standard can be found online at
@url{https://pubs.opengroup.org/onlinepubs/9699919799/}.
@node BTL
@appendixsec Extensions in Brian Kernighan's @command{awk}
@cindex @command{awk} @subentry versions of @seealso{Brian Kernighan's @command{awk}}
@cindex extensions @subentry Brian Kernighan's @command{awk}
@cindex Brian Kernighan's @command{awk} @subentry extensions
@cindex Kernighan, Brian
Brian Kernighan
has made his version available via his home page
(@pxref{Other Versions}).
This @value{SECTION} describes common extensions that
originally appeared in his version of @command{awk}:
@itemize @value{BULLET}
@item
The @samp{**} and @samp{**=} operators
(@pxref{Arithmetic Ops}
and
@ref{Assignment Ops})
@item
The use of @code{func} as an abbreviation for @code{function}
(@pxref{Definition Syntax})
@item
The @code{fflush()} built-in function for flushing buffered output
(@pxref{I/O Functions})
@ignore
@item
The @code{SYMTAB} array, that allows access to @command{awk}'s internal symbol
table. This feature was never documented for his @command{awk}, largely because
it is somewhat shakily implemented. For instance, you cannot access arrays
or array elements through it
@end ignore
@end itemize
@xref{Common Extensions} for a full list of the extensions
available in his @command{awk}.
@node POSIX/GNU
@appendixsec Extensions in @command{gawk} Not in POSIX @command{awk}
@cindex compatibility mode (@command{gawk}) @subentry extensions
@cindex extensions @subentry in @command{gawk}, not in POSIX @command{awk}
@cindex POSIX @subentry @command{gawk} extensions not included in
The GNU implementation, @command{gawk}, adds a large number of features.
They can all be disabled with either the @option{--traditional} or
@option{--posix} options
(@pxref{Options}).
A number of features have come and gone over the years. This @value{SECTION}
summarizes the additional features over POSIX @command{awk} that are
in the current version of @command{gawk}.
@itemize @value{BULLET}
@item
Additional predefined variables:
@itemize @value{MINUS}
@item
The
@code{ARGIND},
@code{BINMODE},
@code{ERRNO},
@code{FIELDWIDTHS},
@code{FPAT},
@code{IGNORECASE},
@code{LINT},
@code{PROCINFO},
@code{RT},
and
@code{TEXTDOMAIN}
variables
(@pxref{Built-in Variables})
@end itemize
@item
Special files in I/O redirections:
@itemize @value{MINUS}
@item
The @file{/dev/stdin}, @file{/dev/stdout}, @file{/dev/stderr}, and
@file{/dev/fd/@var{N}} special @value{FN}s
(@pxref{Special Files})
@item
The @file{/inet}, @file{/inet4}, and @file{/inet6} special files for
TCP/IP networking using @samp{|&} to specify which version of the
IP protocol to use
(@pxref{TCP/IP Networking})
@end itemize
@item
Changes and/or additions to the language:
@itemize @value{MINUS}
@item
The @samp{\x} escape sequence
(@pxref{Escape Sequences})
@item
Full support for both POSIX and GNU regexps
(@pxref{Regexp})
@item
The ability for @code{FS} and for the third
argument to @code{split()} to be null strings
(@pxref{Single Character Fields})
@item
The ability for @code{RS} to be a regexp
(@pxref{Records})
@item
The ability to use octal and hexadecimal constants in @command{awk}
program source code
(@pxref{Nondecimal-numbers})
@item
The @samp{|&} operator for two-way I/O to a coprocess
(@pxref{Two-way I/O})
@item
Indirect function calls
(@pxref{Indirect Calls})
@item
Directories on the command line produce a warning and are skipped
(@pxref{Command-line directories})
@item
Output with @code{print} and @code{printf} need not be fatal
(@pxref{Nonfatal})
@end itemize
@item
New keywords:
@itemize @value{MINUS}
@item
The @code{BEGINFILE} and @code{ENDFILE} special patterns
(@pxref{BEGINFILE/ENDFILE})
@item
The @code{switch} statement
(@pxref{Switch Statement})
@end itemize
@item
Changes to standard @command{awk} functions:
@itemize @value{MINUS}
@item
The optional second argument to @code{close()} that allows closing one end
of a two-way pipe to a coprocess
(@pxref{Two-way I/O})
@item
POSIX compliance for @code{gsub()} and @code{sub()} with @option{--posix}
@item
The @code{length()} function accepts an array argument
and returns the number of elements in the array
(@pxref{String Functions})
@item
The optional third argument to the @code{match()} function
for capturing text-matching subexpressions within a regexp
(@pxref{String Functions})
@item
Positional specifiers in @code{printf} formats for
making translations easier
(@pxref{Printf Ordering})
@item
The @code{split()} function's additional optional fourth
argument, which is an array to hold the text of the field separators
(@pxref{String Functions})
@end itemize
@item
Additional functions only in @command{gawk}:
@itemize @value{MINUS}
@item
The @code{gensub()}, @code{patsplit()}, and @code{strtonum()} functions
for more powerful text manipulation
(@pxref{String Functions})
@item
The @code{asort()} and @code{asorti()} functions for sorting arrays
(@pxref{Array Sorting})
@item
The @code{mktime()}, @code{systime()}, and @code{strftime()}
functions for working with timestamps
(@pxref{Time Functions})
@item
The
@code{and()},
@code{compl()},
@code{lshift()},
@code{or()},
@code{rshift()},
and
@code{xor()}
functions for bit manipulation
(@pxref{Bitwise Functions})
@c In 4.1, and(), or() and xor() grew the ability to take > 2 arguments
@item
The @code{isarray()} function to check if a variable is an array or not
(@pxref{Type Functions})
@item
The @code{bindtextdomain()}, @code{dcgettext()}, and @code{dcngettext()}
functions for internationalization
(@pxref{Programmer i18n})
@ifset INTDIV
@item
The @code{intdiv0()} function for doing integer
division and remainder
(@pxref{Numeric Functions})
@end ifset
@end itemize
@item
Changes and/or additions in the command-line options:
@itemize @value{MINUS}
@item
The @env{AWKPATH} environment variable for specifying a path search for
the @option{-f} command-line option
(@pxref{Options})
@item
The @env{AWKLIBPATH} environment variable for specifying a path search for
the @option{-l} command-line option
(@pxref{Options})
@item
The
@option{-b},
@option{-c},
@option{-C},
@option{-d},
@option{-D},
@option{-e},
@option{-E},
@option{-g},
@option{-h},
@option{-i},
@option{-l},
@option{-L},
@option{-M},
@option{-n},
@option{-N},
@option{-o},
@option{-O},
@option{-p},
@option{-P},
@option{-r},
@option{-s},
@option{-S},
@option{-t},
and
@option{-V}
short options. Also, the
ability to use GNU-style long-named options that start with @option{--},
and the
@option{--assign},
@option{--bignum},
@option{--characters-as-bytes},
@option{--copyright},
@option{--debug},
@option{--dump-variables},
@option{--exec},
@option{--field-separator},
@option{--file},
@option{--gen-pot},
@option{--help},
@option{--include},
@option{--lint},
@option{--lint-old},
@option{--load},
@option{--non-decimal-data},
@option{--optimize},
@option{--no-optimize},
@option{--posix},
@option{--pretty-print},
@option{--profile},
@option{--re-interval},
@option{--sandbox},
@option{--source},
@option{--traditional},
@option{--use-lc-numeric},
and
@option{--version}
long options
(@pxref{Options}).
@end itemize
@c new ports
@item
Support for the following obsolete systems was removed from the code
and the documentation for @command{gawk} @value{PVERSION} 4.0:
@c nested table
@itemize @value{MINUS}
@item
Amiga
@item
Atari
@item
BeOS
@item
Cray
@item
MIPS RiscOS
@item
MS-DOS with the Microsoft Compiler
@item
MS-Windows with the Microsoft Compiler
@item
NeXT
@item
SunOS 3.x, Sun 386 (Road Runner)
@item
Tandem (non-POSIX)
@item
Prestandard VAX C compiler for VAX/VMS
@item
GCC for VAX and Alpha has not been tested for a while.
@end itemize
@item
Support for the following obsolete system was removed from the code
for @command{gawk} @value{PVERSION} 4.1:
@c nested table
@itemize @value{MINUS}
@item
Ultrix
@end itemize
@item
Support for the following systems was removed from the code
for @command{gawk} @value{PVERSION} 4.2:
@c nested table
@itemize @value{MINUS}
@item
MirBSD
@item
GNU/Linux on Alpha
@end itemize
@end itemize
@c XXX ADD MORE STUFF HERE
@c This does not need to be in the formal book.
@ifclear FOR_PRINT
@node Feature History
@appendixsec History of @command{gawk} Features
@ignore
See the thread:
https://groups.google.com/forum/#!topic/comp.lang.awk/SAUiRuff30c
This motivated me to add this section.
@end ignore
@ignore
I've tried to follow this general order, esp.@: for the 3.0 and 3.1 sections:
variables
special files
language changes (e.g., hex constants)
differences in standard awk functions
new gawk functions
new keywords
new command-line options
behavioral changes
extension API changes
new / deprecated / removed ports
installation time stuff
Within each category, be alphabetical.
@end ignore
This @value{SECTION} describes the features in @command{gawk}
over and above those in POSIX @command{awk},
in the order they were added to @command{gawk}.
Version 2.10 of @command{gawk} introduced the following features:
@itemize @value{BULLET}
@item
The @env{AWKPATH} environment variable for specifying a path search for
the @option{-f} command-line option
(@pxref{Options}).
@item
The @code{IGNORECASE} variable and its effects
(@pxref{Case-sensitivity}).
@item
The @file{/dev/stdin}, @file{/dev/stdout}, @file{/dev/stderr} and
@file{/dev/fd/@var{N}} special @value{FN}s
(@pxref{Special Files}).
@end itemize
Version 2.13 of @command{gawk} introduced the following features:
@itemize @value{BULLET}
@item
The @code{FIELDWIDTHS} variable and its effects
(@pxref{Constant Size}).
@item
The @code{systime()} and @code{strftime()} built-in functions for obtaining
and printing timestamps
(@pxref{Time Functions}).
@item
Additional command-line options
(@pxref{Options}):
@itemize @value{MINUS}
@item
The @option{-W lint} option to provide error and portability checking
for both the source code and at runtime.
@item
The @option{-W compat} option to turn off the GNU extensions.
@item
The @option{-W posix} option for full POSIX compliance.
@end itemize
@end itemize
Version 2.14 of @command{gawk} introduced the following feature:
@itemize @value{BULLET}
@item
The @code{next file} statement for skipping to the next @value{DF}
(@pxref{Nextfile Statement}).
@end itemize
Version 2.15 of @command{gawk} introduced the following features:
@itemize @value{BULLET}
@item
New variables (@pxref{Built-in Variables}):
@itemize @value{MINUS}
@item
@code{ARGIND}, which tracks the movement of @code{FILENAME}
through @code{ARGV}.
@item
@code{ERRNO}, which contains the system error message when
@code{getline} returns @minus{}1 or @code{close()} fails.
@end itemize
@item
The @file{/dev/pid}, @file{/dev/ppid}, @file{/dev/pgrpid}, and
@file{/dev/user} special @value{FN}s. These have since been removed.
@item
The ability to delete all of an array at once with @samp{delete @var{array}}
(@pxref{Delete}).
@item
Command-line option changes
(@pxref{Options}):
@itemize @value{MINUS}
@item
The ability to use GNU-style long-named options that start with @option{--}.
@item
The @option{--source} option for mixing command-line and library-file
source code.
@end itemize
@end itemize
Version 3.0 of @command{gawk} introduced the following features:
@itemize @value{BULLET}
@item
New or changed variables:
@itemize @value{MINUS}
@item
@code{IGNORECASE} changed, now applying to string comparison as well
as regexp operations
(@pxref{Case-sensitivity}).
@item
@code{RT}, which contains the input text that matched @code{RS}
(@pxref{Records}).
@end itemize
@item
Full support for both POSIX and GNU regexps
(@pxref{Regexp}).
@item
The @code{gensub()} function for more powerful text manipulation
(@pxref{String Functions}).
@item
The @code{strftime()} function acquired a default time format,
allowing it to be called with no arguments
(@pxref{Time Functions}).
@item
The ability for @code{FS} and for the third
argument to @code{split()} to be null strings
(@pxref{Single Character Fields}).
@item
The ability for @code{RS} to be a regexp
(@pxref{Records}).
@item
The @code{next file} statement became @code{nextfile}
(@pxref{Nextfile Statement}).
@item
The @code{fflush()} function from
BWK @command{awk}
(then at Bell Laboratories;
@pxref{I/O Functions}).
@item
New command-line options:
@itemize @value{MINUS}
@item
The @option{--lint-old} option to
warn about constructs that are not available in
the original Version 7 Unix version of @command{awk}
(@pxref{V7/SVR3.1}).
@item
The @option{-m} option from BWK @command{awk}. (Brian was
still at Bell Laboratories at the time.) This was later removed from
both his @command{awk} and from @command{gawk}.
@item
The @option{--re-interval} option to provide interval expressions in regexps
(@pxref{Regexp Operators}).
@item
The @option{--traditional} option was added as a better name for
@option{--compat} (@pxref{Options}).
@end itemize
@item
The use of GNU Autoconf to control the configuration process
(@pxref{Quick Installation}).
@item
Amiga support.
This has since been removed.
@end itemize
Version 3.1 of @command{gawk} introduced the following features:
@itemize @value{BULLET}
@item
New variables
(@pxref{Built-in Variables}):
@itemize @value{MINUS}
@item
@code{BINMODE}, for non-POSIX systems,
which allows binary I/O for input and/or output files
(@pxref{PC Using}).
@item
@code{LINT}, which dynamically controls lint warnings.
@item
@code{PROCINFO}, an array for providing process-related information.
@item
@code{TEXTDOMAIN}, for setting an application's internationalization text domain
(@pxref{Internationalization}).
@end itemize
@item
The ability to use octal and hexadecimal constants in @command{awk}
program source code
(@pxref{Nondecimal-numbers}).
@item
The @samp{|&} operator for two-way I/O to a coprocess
(@pxref{Two-way I/O}).
@item
The @file{/inet} special files for TCP/IP networking using @samp{|&}
(@pxref{TCP/IP Networking}).
@item
The optional second argument to @code{close()} that allows closing one end
of a two-way pipe to a coprocess
(@pxref{Two-way I/O}).
@item
The optional third argument to the @code{match()} function
for capturing text-matching subexpressions within a regexp
(@pxref{String Functions}).
@item
Positional specifiers in @code{printf} formats for
making translations easier
(@pxref{Printf Ordering}).
@item
A number of new built-in functions:
@itemize @value{MINUS}
@item
The @code{asort()} and @code{asorti()} functions for sorting arrays
(@pxref{Array Sorting}).
@item
The @code{bindtextdomain()}, @code{dcgettext()} and @code{dcngettext()} functions
for internationalization
(@pxref{Programmer i18n}).
@item
The @code{extension()} function and the ability to add
new built-in functions dynamically
(@pxref{Dynamic Extensions}).
@item
The @code{mktime()} function for creating timestamps
(@pxref{Time Functions}).
@item
The @code{and()}, @code{or()}, @code{xor()}, @code{compl()},
@code{lshift()}, @code{rshift()}, and @code{strtonum()} functions
(@pxref{Bitwise Functions}).
@end itemize
@item
@cindex @code{next file} statement
The support for @samp{next file} as two words was removed completely
(@pxref{Nextfile Statement}).
@item
Additional command-line options
(@pxref{Options}):
@itemize @value{MINUS}
@item
The @option{--dump-variables} option to print a list of all global variables.
@item
The @option{--exec} option, for use in CGI scripts.
@item
The @option{--gen-po} command-line option and the use of a leading
underscore to mark strings that should be translated
(@pxref{String Extraction}).
@item
The @option{--non-decimal-data} option to allow non-decimal
input data
(@pxref{Nondecimal Data}).
@item
The @option{--profile} option and @command{pgawk}, the
profiling version of @command{gawk}, for producing execution
profiles of @command{awk} programs
(@pxref{Profiling}).
@item
The @option{--use-lc-numeric} option to force @command{gawk}
to use the locale's decimal point for parsing input data
(@pxref{Conversion}).
@end itemize
@item
The use of GNU Automake to help in standardizing the configuration process
(@pxref{Quick Installation}).
@item
The use of GNU @command{gettext} for @command{gawk}'s own message output
(@pxref{Gawk I18N}).
@item
BeOS support. This was later removed.
@item
Tandem support. This was later removed.
@item
The Atari port became officially unsupported and was
later removed entirely.
@item
The source code changed to use ISO C standard-style function definitions.
@item
POSIX compliance for @code{sub()} and @code{gsub()}
(@pxref{Gory Details}).
@item
The @code{length()} function was extended to accept an array argument
and return the number of elements in the array
(@pxref{String Functions}).
@item
The @code{strftime()} function acquired a third argument to
enable printing times as UTC
(@pxref{Time Functions}).
@end itemize
Version 4.0 of @command{gawk} introduced the following features:
@itemize @value{BULLET}
@item
Variable additions:
@itemize @value{MINUS}
@item
@code{FPAT}, which allows you to specify a regexp that matches
the fields, instead of matching the field separator
(@pxref{Splitting By Content}).
@item
If @code{PROCINFO["sorted_in"]} exists, @samp{for(iggy in foo)} loops sort the
indices before looping over them. The value of this element
provides control over how the indices are sorted before the loop
traversal starts
(@pxref{Controlling Scanning}).
@item
@code{PROCINFO["strftime"]}, which holds
the default format for @code{strftime()}
(@pxref{Time Functions}).
@end itemize
@item
The special files @file{/dev/pid}, @file{/dev/ppid}, @file{/dev/pgrpid}
and @file{/dev/user} were removed.
@item
Support for IPv6 was added via the @file{/inet6} special file.
@file{/inet4} forces IPv4 and @file{/inet} chooses the system
default, which is probably IPv4
(@pxref{TCP/IP Networking}).
@item
The use of @samp{\s} and @samp{\S} escape sequences in regular expressions
(@pxref{GNU Regexp Operators}).
@item
Interval expressions became part of default regular expressions
(@pxref{Regexp Operators}).
@item
POSIX character classes work even with @option{--traditional}
(@pxref{Regexp Operators}).
@item
@code{break} and @code{continue} became invalid outside a loop,
even with @option{--traditional}
(@pxref{Break Statement}, and also see
@ref{Continue Statement}).
@item
@code{fflush()}, @code{nextfile}, and @samp{delete @var{array}}
are allowed if @option{--posix} or @option{--traditional}, since they
are all now part of POSIX.
@item
An optional third argument to
@code{asort()} and @code{asorti()}, specifying how to sort
(@pxref{String Functions}).
@item
The behavior of @code{fflush()} changed to match BWK @command{awk}
and for POSIX; now both @samp{fflush()} and @samp{fflush("")}
flush all open output redirections
(@pxref{I/O Functions}).
@item
The @code{isarray()}
function which distinguishes if an item is an array
or not, to make it possible to traverse arrays of arrays
(@pxref{Type Functions}).
@item
The @code{patsplit()}
function which gives the same capability as @code{FPAT}, for splitting
(@pxref{String Functions}).
@item
An optional fourth argument to the @code{split()} function,
which is an array to hold the values of the separators
(@pxref{String Functions}).
@item
Arrays of arrays
(@pxref{Arrays of Arrays}).
@item
The @code{BEGINFILE} and @code{ENDFILE} special patterns
(@pxref{BEGINFILE/ENDFILE}).
@item
Indirect function calls
(@pxref{Indirect Calls}).
@item
@code{switch} / @code{case} are enabled by default
(@pxref{Switch Statement}).
@item
Command-line option changes
(@pxref{Options}):
@itemize @value{MINUS}
@item
The @option{-b} and @option{--characters-as-bytes} options
which prevent @command{gawk} from treating input as a multibyte string.
@item
The redundant @option{--compat}, @option{--copyleft}, and @option{--usage}
long options were removed.
@item
The @option{--gen-po} option was finally renamed to the correct @option{--gen-pot}.
@item
The @option{--sandbox} option which disables certain features.
@item
All long options acquired corresponding short options, for use in @samp{#!} scripts.
@end itemize
@item
Directories named on the command line now produce a warning, not a fatal
error, unless @option{--posix} or @option{--traditional} are used
(@pxref{Command-line directories}).
@item
The @command{gawk} internals were rewritten, bringing the @command{dgawk}
debugger and possibly improved performance
(@pxref{Debugger}).
@item
Per the GNU Coding Standards, dynamic extensions must now define
a global symbol indicating that they are GPL-compatible
(@pxref{Plugin License}).
@item
@cindex POSIX mode
In POSIX mode, string comparisons use @code{strcoll()} / @code{wcscoll()}
(@pxref{POSIX String Comparison}).
@item
The option for raw sockets was removed, since it was never implemented
(@pxref{TCP/IP Networking}).
@item
Ranges of the form @samp{[d-h]} are treated as if they were in the
C locale, no matter what kind of regexp is being used, and even if
@option{--posix}
(@pxref{Ranges and Locales}).
@item
Support was removed for the following systems:
@itemize @value{MINUS}
@item
Atari
@item
Amiga
@item
BeOS
@item
Cray
@item
MIPS RiscOS
@item
MS-DOS with the Microsoft Compiler
@item
MS-Windows with the Microsoft Compiler
@item
NeXT
@item
SunOS 3.x, Sun 386 (Road Runner)
@item
Tandem (non-POSIX)
@item
Prestandard VAX C compiler for VAX/VMS
@end itemize
@end itemize
Version 4.1 of @command{gawk} introduced the following features:
@itemize @value{BULLET}
@item
Three new arrays:
@code{SYMTAB}, @code{FUNCTAB}, and @code{PROCINFO["identifiers"]}
(@pxref{Auto-set}).
@item
The three executables @command{gawk}, @command{pgawk}, and @command{dgawk}, were merged into
one, named just @command{gawk}. As a result the command-line options changed.
@item
Command-line option changes
(@pxref{Options}):
@itemize @value{MINUS}
@item
The @option{-D} option invokes the debugger.
@item
The @option{-i} and @option{--include} options
load @command{awk} library files.
@item
The @option{-l} and @option{--load} options load compiled dynamic extensions.
@item
The @option{-M} and @option{--bignum} options enable MPFR.
@item
The @option{-o} option only does pretty-printing.
@item
The @option{-p} option is used for profiling.
@item
The @option{-R} option was removed.
@end itemize
@item
Support for high precision arithmetic with MPFR
(@pxref{Arbitrary Precision Arithmetic}).
@item
The @code{and()}, @code{or()} and @code{xor()} functions
changed to allow any number of arguments,
with a minimum of two
(@pxref{Bitwise Functions}).
@item
The dynamic extension interface was completely redone
(@pxref{Dynamic Extensions}).
@item
Redirected @code{getline} became allowed inside
@code{BEGINFILE} and @code{ENDFILE}
(@pxref{BEGINFILE/ENDFILE}).
@item
The @code{where} command was added to the debugger
(@pxref{Execution Stack}).
@item
Support for Ultrix was removed.
@end itemize
Version 4.2 of @command{gawk} introduced the following changes:
@itemize @bullet
@item
Changes to @code{ENVIRON} are reflected into @command{gawk}'s
environment and that of programs that it runs.
@xref{Auto-set}.
@item
@code{FIELDWIDTHS} was enhanced to allow skipping characters
before assigning a value to a field
(@pxref{Splitting By Content}).
@item
The @code{PROCINFO["argv"]} array.
@xref{Auto-set}.
@item
The maximum number of hexadecimal digits in @samp{\x} escapes
is now two.
@xref{Escape Sequences}.
@item
Strongly typed regexp constants of the form @samp{@@/@dots{}/}
(@pxref{Strong Regexp Constants}).
@item
The bitwise functions changed, making negative arguments into
a fatal error (@pxref{Bitwise Functions}).
@ifset INTDIV
@item
The @code{intdiv0()} function.
@xref{Numeric Functions}.
@end ifset
@item
The @code{mktime()} function now accepts an optional
second argument
(@pxref{Time Functions}).
@item
The @code{typeof()} function (@pxref{Type Functions}).
@item
Optimizations are enabled by default. Use @option{-s} /
@option{--no-optimize} to disable optimizations.
@item
For many years, POSIX specified that default field splitting
only allowed spaces and tabs to separate fields, and this was
how @command{gawk} behaved with @option{--posix}. As of 2013,
the standard restored historical behavior, and now default
field splitting with @option{--posix} also allows newlines to
separate fields.
@item
Nonfatal output with @code{print} and @code{printf}.
@xref{Nonfatal}.
@item
Retryable I/O via @code{PROCINFO[@var{input-file}, "RETRY"]};
(@pxref{Retrying Input}).
@item
Changes to the pretty-printer (@pxref{Profiling}):
@c nested table
@itemize @value{MINUS}
@item
The @option{--pretty-print} option no longer runs the @command{awk}
program too.
@item
Comments in the source program are preserved and placed into the
output file.
@item
Explicit parentheses for expressions
in the input are preserved in the generated output.
@end itemize
@item
Improvements to the extension API
(@pxref{Dynamic Extensions}):
@c nested
@itemize @value{MINUS}
@item
The @code{get_file()} function to access open redirections.
@item
The @code{nonfatal()} function for generating nonfatal error messages.
@item
Support for GMP and MPFR values.
@item
Input parsers can now override the default field parsing mechanism
by specifying explicit locations.
@end itemize
@item
Shell startup files are supplied with the distribution and
installed by @samp{make install} (@pxref{Shell Startup Files}).
@item
The @command{igawk} program and its manual page are no longer
installed when @command{gawk} is built.
@xref{Igawk Program}.
@item
Support for MirBSD was removed.
@item
Support for GNU/Linux on Alpha was removed.
@end itemize
Version 5.0 added the following features:
@itemize
@item
The @code{PROCINFO["platform"]} array element, which allows you
to write code that takes the operating system / platform into account.
@end itemize
Version 5.1 was created to release @command{gawk} with a correct
major version number for the API. This was overlooked for version 5.0,
unfortunately. It added the following features:
@itemize
@item
The index for this manual was completely reworked.
@item
Support was added for MSYS2.
@end itemize
@c XXX ADD MORE STUFF HERE
@end ifclear
@node Common Extensions
@appendixsec Common Extensions Summary
@cindex extensions @subentry Brian Kernighan's @command{awk}
@cindex extensions @subentry @command{mawk}
The following table summarizes the common extensions supported
by @command{gawk}, Brian Kernighan's @command{awk}, and @command{mawk},
the three most widely used freely available versions of @command{awk}
(@pxref{Other Versions}).
@multitable {@file{/dev/stderr} special file} {BWK @command{awk}} {@command{mawk}} {@command{gawk}} {Now standard}
@headitem Feature @tab BWK @command{awk} @tab @command{mawk} @tab @command{gawk} @tab Now standard
@item @samp{\x} escape sequence @tab X @tab X @tab X @tab
@item @code{FS} as null string @tab X @tab X @tab X @tab
@item @file{/dev/stdin} special file @tab X @tab X @tab X @tab
@item @file{/dev/stdout} special file @tab X @tab X @tab X @tab
@item @file{/dev/stderr} special file @tab X @tab X @tab X @tab
@item @code{delete} without subscript @tab X @tab X @tab X @tab X
@item @code{fflush()} function @tab X @tab X @tab X @tab X
@item @code{length()} of an array @tab X @tab X @tab X @tab
@item @code{nextfile} statement @tab X @tab X @tab X @tab X
@item @code{**} and @code{**=} operators @tab X @tab @tab X @tab
@item @code{func} keyword @tab X @tab @tab X @tab
@item @code{BINMODE} variable @tab @tab X @tab X @tab
@item @code{RS} as regexp @tab X @tab X @tab X @tab
@item Time-related functions @tab @tab X @tab X @tab
@end multitable
@node Ranges and Locales
@appendixsec Regexp Ranges and Locales: A Long Sad Story
This @value{SECTION} describes the confusing history of ranges within
regular expressions and their interactions with locales, and how this
affected different versions of @command{gawk}.
@cindex ASCII
@cindex EBCDIC
The original Unix tools that worked with regular expressions defined
character ranges (such as @samp{[a-z]}) to match any character between
the first character in the range and the last character in the range,
inclusive. Ordering was based on the numeric value of each character
in the machine's native character set. Thus, on ASCII-based systems,
@samp{[a-z]} matched all the lowercase letters, and only the lowercase
letters, as the numeric values for the letters from @samp{a} through
@samp{z} were contiguous. (On an EBCDIC system, the range @samp{[a-z]}
includes additional nonalphabetic characters as well.)
Almost all introductory Unix literature explained range expressions
as working in this fashion, and in particular, would teach that the
``correct'' way to match lowercase letters was with @samp{[a-z]}, and
that @samp{[A-Z]} was the ``correct'' way to match uppercase letters.
And indeed, this was true.@footnote{And Life was good.}
The 1992 POSIX standard introduced the idea of locales (@pxref{Locales}).
Because many locales include other letters besides the plain 26
letters of the English alphabet, the POSIX standard added
character classes (@pxref{Bracket Expressions}) as a way to match
different kinds of characters besides the traditional ones in the ASCII
character set.
However, the standard @emph{changed} the interpretation of range expressions.
In the @code{"C"} and @code{"POSIX"} locales, a range expression like
@samp{[a-dx-z]} is still equivalent to @samp{[abcdxyz]}, as in ASCII.
But outside those locales, the ordering was defined to be based on
@dfn{collation order}.
What does that mean?
In many locales, @samp{A} and @samp{a} are both less than @samp{B}.
In other words, these locales sort characters in dictionary order,
and @samp{[a-dx-z]} is typically not equivalent to @samp{[abcdxyz]};
instead, it might be equivalent to @samp{[ABCXYabcdxyz]}, for example.
This point needs to be emphasized: much literature teaches that you should
use @samp{[a-z]} to match a lowercase character. But on systems with
non-ASCII locales, this also matches all of the uppercase characters
except @samp{A} or @samp{Z}! This was a continuous cause of confusion, even well
into the twenty-first century.
To demonstrate these issues, the following example uses the @code{sub()}
function, which does text replacement (@pxref{String Functions}). Here,
the intent is to remove trailing uppercase characters:
@example
$ @kbd{echo something1234abc | gawk-3.1.8 '@{ sub("[A-Z]*$", ""); print @}'}
@print{} something1234a
@end example
@noindent
This output is unexpected, as the @samp{bc} at the end of
@samp{something1234abc} should not normally match @samp{[A-Z]*}.
This result is due to the locale setting (and thus you may not see
it on your system).
@cindex Unicode
@cindex ASCII
Similar considerations apply to other ranges. For example, @samp{["-/]}
is perfectly valid in ASCII, but is not valid in many Unicode locales,
such as @code{en_US.UTF-8}.
Early versions of @command{gawk} used regexp matching code that was not
locale-aware, so ranges had their traditional interpretation.
When @command{gawk} switched to using locale-aware regexp matchers,
the problems began; especially as both GNU/Linux and commercial Unix
vendors started implementing non-ASCII locales, @emph{and making them
the default}. Perhaps the most frequently asked question became something
like, ``Why does @samp{[A-Z]} match lowercase letters?!?''
@cindex Berry, Karl
This situation existed for close to 10 years, if not more, and
the @command{gawk} maintainer grew weary of trying to explain that
@command{gawk} was being nicely standards-compliant, and that the issue
was in the user's locale. During the development of @value{PVERSION} 4.0,
he modified @command{gawk} to always treat ranges in the original,
pre-POSIX fashion, unless @option{--posix} was used (@pxref{Options}).@footnote{And
thus was born the Campaign for Rational Range Interpretation (or
RRI). A number of GNU tools have already implemented this change,
or will soon. Thanks to Karl Berry for coining the phrase ``Rational
Range Interpretation.''}
Fortunately, shortly before the final release of @command{gawk} 4.0,
the maintainer learned that the 2008 standard had changed the
definition of ranges, such that outside the @code{"C"} and @code{"POSIX"}
locales, the meaning of range expressions was @emph{undefined}.@footnote{See
@uref{https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_03_05, the standard}
and
@uref{https://pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_xbd_chap09.html#tag_21_09_03_05, its rationale}.}
By using this lovely technical term, the standard gives license
to implementers to implement ranges in whatever way they choose.
The @command{gawk} maintainer chose to apply the pre-POSIX meaning
both with the default regexp matching and when @option{--traditional} or
@option{--posix} are used.
In all cases @command{gawk} remains POSIX-compliant.
@node Contributors
@appendixsec Major Contributors to @command{gawk}
@cindex @command{gawk} @subentry list of contributors to
@quotation
@i{Always give credit where credit is due.}
@author Anonymous
@end quotation
This @value{SECTION} names the major contributors to @command{gawk}
and/or this @value{DOCUMENT}, in approximate chronological order:
@itemize @value{BULLET}
@item
@cindex Aho, Alfred
@cindex Weinberger, Peter
@cindex Kernighan, Brian
Dr.@: Alfred V.@: Aho,
Dr.@: Peter J.@: Weinberger, and
Dr.@: Brian W.@: Kernighan, all of Bell Laboratories,
designed and implemented Unix @command{awk},
from which @command{gawk} gets the majority of its feature set.
@item
@cindex Rubin, Paul
Paul Rubin
did the initial design and implementation in 1986, and wrote
the first draft (around 40 pages) of this @value{DOCUMENT}.
@item
@cindex Fenlason, Jay
Jay Fenlason
finished the initial implementation.
@item
@cindex Close, Diane
Diane Close
revised the first draft of this @value{DOCUMENT}, bringing it
to around 90 pages.
@item
@cindex Stallman, Richard
Richard Stallman
helped finish the implementation and the initial draft of this
@value{DOCUMENT}.
He is also the founder of the FSF and the GNU Project.
@item
@cindex Woods, John
John Woods
contributed parts of the code (mostly fixes) in
the initial version of @command{gawk}.
@item
@cindex Trueman, David
In 1988,
David Trueman
took over primary maintenance of @command{gawk},
making it compatible with ``new'' @command{awk}, and
greatly improving its performance.
@item
@cindex Kwok, Conrad
@cindex Garfinkle, Scott
@cindex Williams, Kent
Conrad Kwok,
Scott Garfinkle,
and
Kent Williams
did the initial ports to MS-DOS with various versions of MSC.
@item
@cindex Rankin, Pat
Pat Rankin
provided the VMS port and its documentation.
@item
@cindex Peterson, Hal
Hal Peterson
provided help in porting @command{gawk} to Cray systems.
(This is no longer supported.)
@item
@cindex Rommel, Kai Uwe
Kai Uwe Rommel
provided the initial port to OS/2 and its documentation.
@item
@cindex Jaegermann, Michal
Michal Jaegermann
provided the port to Atari systems and its documentation.
(This port is no longer supported.)
He continues to provide portability checking,
and has done a lot of work to make sure @command{gawk}
works on non-32-bit systems.
@item
@cindex Fish, Fred
Fred Fish
provided the port to Amiga systems and its documentation.
(With Fred's sad passing, this is no longer supported.)
@item
@cindex Deifik, Scott
Scott Deifik
formerly maintained the MS-DOS port using DJGPP.
@item
@cindex Zaretskii, Eli
Eli Zaretskii
currently maintains the MS-Windows port using MinGW.
@item
@cindex Grigera, Juan
Juan Grigera
provided a port to Windows32 systems.
(This is no longer supported.)
@item
@cindex Hankerson, Darrel
For many years,
Dr.@: Darrel Hankerson
acted as coordinator for the various ports to different PC platforms
and created binary distributions for various PC operating systems.
He was also instrumental in keeping the documentation up to date for
the various PC platforms.
@item
@cindex Zoulas, Christos
Christos Zoulas
provided the @code{extension()}
built-in function for dynamically adding new functions.
(This was obsoleted at @command{gawk} 4.1.)
@item
@cindex Kahrs, J@"urgen
J@"urgen Kahrs
contributed the initial version of the TCP/IP networking
code and documentation, and motivated the inclusion of the @samp{|&} operator.
@item
@cindex Davies, Stephen
Stephen Davies
provided the initial port to Tandem systems and its documentation.
(However, this is no longer supported.)
He was also instrumental in the initial work to integrate the
byte-code internals into the @command{gawk} code base.
Additionally, he did most of the work enabling the pretty-printer
to preserve and output comments.
@item
@cindex Woehlke, Matthew
Matthew Woehlke
provided improvements for Tandem's POSIX-compliant systems.
@item
@cindex Brown, Martin
Martin Brown
provided the port to BeOS and its documentation.
(This is no longer supported.)
@item
@cindex Peters, Arno
Arno Peters
did the initial work to convert @command{gawk} to use
GNU Automake and GNU @command{gettext}.
@item
@cindex Broder, Alan J.@:
Alan J.@: Broder
provided the initial version of the @code{asort()} function
as well as the code for the optional third argument to the
@code{match()} function.
@item
@cindex Buening, Andreas
Andreas Buening
updated the @command{gawk} port for OS/2.
@item
@cindex Hasegawa, Isamu
Isamu Hasegawa,
of IBM in Japan, contributed support for multibyte characters.
@item
@cindex Benzinger, Michael
Michael Benzinger contributed the initial code for @code{switch} statements.
@item
@cindex McPhee, Patrick T.J.@:
Patrick T.J.@: McPhee contributed the code for dynamic loading in Windows32
environments.
(This is no longer supported.)
@item
@cindex Wallin, Anders
Anders Wallin helped keep the VMS port going for several years.
@item
@cindex Gordon, Assaf
Assaf Gordon contributed the initial code to implement the
@option{--sandbox} option.
@item
@cindex Haque, John
John Haque made the following contributions:
@itemize @value{MINUS}
@item
The modifications to convert @command{gawk}
into a byte-code interpreter, including the debugger
@item
The addition of true arrays of arrays
@item
The additional modifications for support of arbitrary-precision arithmetic
@item
The initial text of
@ref{Arbitrary Precision Arithmetic}
@item
The work to merge the three versions of @command{gawk}
into one, for the 4.1 release
@item
Improved array internals for arrays indexed by integers
@item
The improved array sorting features were also driven by John, together
with Pat Rankin
@end itemize
@cindex Papadopoulos, Panos
@item
Panos Papadopoulos contributed the original text for @ref{Include Files}.
@item
@cindex Yawitz, Efraim
Efraim Yawitz contributed the original text for @ref{Debugger}.
@item
@cindex Schorr, Andrew
The development of the extension API first released with
@command{gawk} 4.1 was driven primarily by
Arnold Robbins and Andrew Schorr, with notable contributions from
the rest of the development team.
@cindex Malmberg, John
@item
John Malmberg contributed significant improvements to the
OpenVMS port and the related documentation.
@item
@cindex Colombo, Antonio
Antonio Giovanni Colombo rewrote a number of examples in the early
chapters that were severely dated, for which I am incredibly grateful.
He also provided and maintains the Italian translation.
@item
@cindex Curreli, Marco
Marco Curreli, together with Antonio Colombo, translated this
@value{DOCUMENT} into Italian. It is included in the @command{gawk}
distribution.
@item
@cindex Guerrero, Juan Manuel
Juan Manuel Guerrero took over maintenance of the DJGPP port.
@item
@cindex Jannick
``Jannick'' provided support for MSYS2.
@item
@cindex Robbins @subentry Arnold
Arnold Robbins
has been working on @command{gawk} since 1988, at first
helping David Trueman, and as the primary maintainer since around 1994.
@end itemize
@node History summary
@appendixsec Summary
@itemize @value{BULLET}
@item
The @command{awk} language has evolved over time. The first release
was with V7 Unix, circa 1978. In 1987, for System V Release 3.1,
major additions, including user-defined functions, were made to the language.
Additional changes were made for System V Release 4, in 1989.
Since then, further minor changes have happened under the auspices of the
POSIX standard.
@item
Brian Kernighan's @command{awk} provides a small number of extensions
that are implemented in common with other versions of @command{awk}.
@item
@command{gawk} provides a large number of extensions over POSIX @command{awk}.
They can be disabled with either the @option{--traditional} or @option{--posix}
options.
@item
@cindex ASCII
@cindex EBCDIC
The interaction of POSIX locales and regexp matching in @command{gawk} has been confusing over
the years. Today, @command{gawk} implements Rational Range Interpretation, where
ranges of the form @samp{[a-z]} match @emph{only} the characters numerically between
@samp{a} through @samp{z} in the machine's native character set. Usually this is ASCII,
but it can be EBCDIC on IBM S/390 systems.
@item
Many people have contributed to @command{gawk} development over the years.
We hope that the list provided in this @value{CHAPTER} is complete and gives
the appropriate credit where credit is due.
@end itemize
@node Installation
@appendix Installing @command{gawk}
@c last two commas are part of see also
@cindex operating systems
@cindex operating systems @seealso{GNU/Linux}
@cindex operating systems @seealso{PC operating systems}
@cindex operating systems @seealso{Unix}
@cindex @command{gawk} @subentry installing
@cindex installing @command{gawk}
This appendix provides instructions for installing @command{gawk} on the
various platforms that are supported by the developers. The primary
developer supports GNU/Linux (and Unix), whereas the other ports are
contributed.
@xref{Bugs}
for the email addresses of the people who maintain
the respective ports.
@menu
* Gawk Distribution:: What is in the @command{gawk} distribution.
* Unix Installation:: Installing @command{gawk} under various
versions of Unix.
* Non-Unix Installation:: Installation on Other Operating Systems.
* Bugs:: Reporting Problems and Bugs.
* Other Versions:: Other freely available @command{awk}
implementations.
* Installation summary:: Summary of installation.
@end menu
@node Gawk Distribution
@appendixsec The @command{gawk} Distribution
@cindex source code @subentry @command{gawk}
This @value{SECTION} describes how to get the @command{gawk}
distribution, how to extract it, and then what is in the various files and
subdirectories.
@menu
* Getting:: How to get the distribution.
* Extracting:: How to extract the distribution.
* Distribution contents:: What is in the distribution.
@end menu
@node Getting
@appendixsubsec Getting the @command{gawk} Distribution
@cindex @command{gawk} @subentry source code, obtaining
There are two ways to get GNU software:
@itemize @value{BULLET}
@item
Copy it from someone else who already has it.
@cindex FSF (Free Software Foundation)
@cindex Free Software Foundation (FSF)
@item
Retrieve @command{gawk}
from the Internet host
@code{ftp.gnu.org}, in the directory @file{/gnu/gawk}.
Both anonymous @command{ftp} and @code{http} access are supported.
If you have the @command{wget} program, you can use a command like
the following:
@example
wget https://ftp.gnu.org/gnu/gawk/gawk-@value{VERSION}.@value{PATCHLEVEL}.tar.gz
@end example
@end itemize
The GNU software archive is mirrored around the world.
The up-to-date list of mirror sites is available from
@uref{https://www.gnu.org/order/ftp.html, the main FSF website}.
Try to use one of the mirrors; they
will be less busy, and you can usually find one closer to your site.
You may also retrieve the @command{gawk} source code from the official
Git repository; for more information see @ref{Accessing The Source}.
@node Extracting
@appendixsubsec Extracting the Distribution
@command{gawk} is distributed as several @code{tar} files compressed with
different compression programs: @command{gzip}, @command{bzip2},
and @command{xz}. For simplicity, the rest of these instructions assume
you are using the one compressed with the GNU Gzip program (@command{gzip}).
Once you have the distribution (e.g.,
@file{gawk-@value{VERSION}.@value{PATCHLEVEL}.tar.gz}),
use @code{gzip} to expand the
file and then use @code{tar} to extract it. You can use the following
pipeline to produce the @command{gawk} distribution:
@example
gzip -d -c gawk-@value{VERSION}.@value{PATCHLEVEL}.tar.gz | tar -xvpf -
@end example
On a system with GNU @command{tar}, you can let @command{tar}
do the decompression for you:
@example
tar -xvpzf gawk-@value{VERSION}.@value{PATCHLEVEL}.tar.gz
@end example
@noindent
Extracting the archive
creates a directory named @file{gawk-@value{VERSION}.@value{PATCHLEVEL}}
in the current directory.
The distribution @value{FN} is of the form
@file{gawk-@var{V}.@var{R}.@var{P}.tar.gz}.
The @var{V} represents the major version of @command{gawk},
the @var{R} represents the current release of version @var{V}, and
the @var{P} represents a @dfn{patch level}, meaning that minor bugs have
been fixed in the release. The current patch level is @value{PATCHLEVEL},
but when retrieving distributions, you should get the version with the highest
version, release, and patch level. (Note, however, that patch levels greater than
or equal to 60 denote ``beta'' or nonproduction software; you might not want
to retrieve such a version unless you don't mind experimenting.)
If you are not on a Unix or GNU/Linux system, you need to make other arrangements
for getting and extracting the @command{gawk} distribution. You should consult
a local expert.
@node Distribution contents
@appendixsubsec Contents of the @command{gawk} Distribution
@cindex @command{gawk} @subentry distribution
The @command{gawk} distribution has a number of C source files,
documentation files,
subdirectories, and files related to the configuration process
(@pxref{Unix Installation}),
as well as several subdirectories related to different non-Unix
operating systems:
@table @asis
@item Various @samp{.c}, @samp{.y}, and @samp{.h} files
These files contain the actual @command{gawk} source code.
@end table
@table @file
@item support/*
C header and source files for routines that @command{gawk}
uses, but that are not part of its core functionality.
For example, argument parsing, regular expression matching,
and random number generating routines are all kept here.
@item ABOUT-NLS
A file containing information about GNU @command{gettext} and translations.
@item AUTHORS
A file with some information about the authorship of @command{gawk}.
It exists only to satisfy the pedants at the Free Software Foundation.
@item README
@itemx README_d/README.*
Descriptive files: @file{README} for @command{gawk} under Unix and the
rest for the various hardware and software combinations.
@item INSTALL
A file providing an overview of the configuration and installation process.
@item ChangeLog
A detailed list of source code changes as bugs are fixed or improvements made.
@item ChangeLog.0
An older list of source code changes.
@item NEWS
A list of changes to @command{gawk} since the last release or patch.
@item NEWS.0
An older list of changes to @command{gawk}.
@item COPYING
The GNU General Public License.
@item POSIX.STD
A description of behaviors in the POSIX standard for @command{awk} that
are left undefined, or where @command{gawk} may not comply fully, as well
as a list of things that the POSIX standard should describe but does not.
@cindex artificial intelligence, @command{gawk} and
@item doc/awkforai.txt
Pointers to the original draft of
a short article describing why @command{gawk} is a good language for
artificial intelligence (AI) programming.
@item doc/bc_notes
A brief description of @command{gawk}'s ``byte code'' internals.
@item doc/README.card
@itemx doc/ad.block
@itemx doc/awkcard.in
@itemx doc/cardfonts
@itemx doc/colors
@itemx doc/macros
@itemx doc/no.colors
@itemx doc/setter.outline
The @command{troff} source for a five-color @command{awk} reference card.
A modern version of @command{troff} such as GNU @command{troff} (@command{groff}) is
needed to produce the color version. See the file @file{README.card}
for instructions if you have an older @command{troff}.
@item doc/gawk.1
The @command{troff} source for a manual page describing @command{gawk}.
This is distributed for the convenience of Unix users.
@cindex Texinfo
@item doc/gawktexi.in
@itemx doc/sidebar.awk
The Texinfo source file for this @value{DOCUMENT}.
It should be processed by @file{doc/sidebar.awk}
before processing with @command{texi2dvi} or @command{texi2pdf}
to produce a printed document, and
with @command{makeinfo} to produce an Info or HTML file.
The @file{Makefile} takes care of this processing and produces
printable output via @command{texi2dvi} or @command{texi2pdf}.
@item doc/gawk.texi
The file produced after processing @file{gawktexi.in}
with @file{sidebar.awk}.
@item doc/gawk.info
The generated Info file for this @value{DOCUMENT}.
@item doc/gawkinet.texi
The Texinfo source file for
@ifinfo
@inforef{Top, , General Introduction, gawkinet, @value{GAWKINETTITLE}}.
@end ifinfo
@ifnotinfo
@cite{@value{GAWKINETTITLE}}.
@end ifnotinfo
It should be processed with @TeX{}
(via @command{texi2dvi} or @command{texi2pdf})
to produce a printed document and
with @command{makeinfo} to produce an Info or HTML file.
@item doc/gawkinet.info
The generated Info file for
@cite{@value{GAWKINETTITLE}}.
@item doc/igawk.1
The @command{troff} source for a manual page describing the @command{igawk}
program presented in
@ref{Igawk Program}.
(Since @command{gawk} can do its own @code{@@include} processing,
neither @command{igawk} nor @file{igawk.1} are installed.)
@item doc/it/*
Files for the Italian translation of this @value{DOCUMENT}, produced and
contributed by Antonio Colombo and Marco Curreli.
@item doc/Makefile.in
The input file used during the configuration process to generate the
actual @file{Makefile} for creating the documentation.
@item Makefile.am
@itemx */Makefile.am
Files used by the GNU Automake software for generating
the @file{Makefile.in} files used by Autoconf and
@command{configure}.
@item Makefile.in
@itemx aclocal.m4
@itemx bisonfix.awk
@itemx config.guess
@itemx configh.in
@itemx configure.ac
@itemx configure
@itemx custom.h
@itemx depcomp
@itemx install-sh
@itemx missing_d/*
@itemx mkinstalldirs
@itemx m4/*
These files and subdirectories are used when configuring and compiling
@command{gawk} for various Unix systems. Most of them are explained
in @ref{Unix Installation}. The rest are there to support the main
infrastructure.
@item po/*
The @file{po} library contains message translations.
@item awklib/extract.awk
@itemx awklib/Makefile.am
@itemx awklib/Makefile.in
@itemx awklib/eg/*
The @file{awklib} directory contains a copy of @file{extract.awk}
(@pxref{Extract Program}),
which can be used to extract the sample programs from the Texinfo
source file for this @value{DOCUMENT}. It also contains a @file{Makefile.in} file, which
@command{configure} uses to generate a @file{Makefile}.
@file{Makefile.am} is used by GNU Automake to create @file{Makefile.in}.
The library functions from
@ref{Library Functions},
are included as ready-to-use files in the @command{gawk} distribution.
They are installed as part of the installation process.
The rest of the programs in this @value{DOCUMENT} are available in appropriate
subdirectories of @file{awklib/eg}.
@item extension/*
The source code, manual pages, and infrastructure files for
the sample extensions included with @command{gawk}.
@xref{Dynamic Extensions}, for more information.
@item extras/*
Additional non-essential files. Currently, this directory contains some shell
startup files to be installed in @file{/etc/profile.d} to aid in manipulating
the @env{AWKPATH} and @env{AWKLIBPATH} environment variables.
@xref{Shell Startup Files}, for more information.
@item posix/*
Files needed for building @command{gawk} on POSIX-compliant systems.
@item pc/*
Files needed for building @command{gawk} under MS-Windows
(@pxref{PC Installation} for details).
@item vms/*
Files needed for building @command{gawk} under Vax/VMS and OpenVMS
(@pxref{VMS Installation} for details).
@item test/*
A test suite for
@command{gawk}. You can use @samp{make check} from the top-level @command{gawk}
directory to run your version of @command{gawk} against the test suite.
If @command{gawk} successfully passes @samp{make check}, then you can
be confident of a successful port.
@end table
@node Unix Installation
@appendixsec Compiling and Installing @command{gawk} on Unix-Like Systems
Usually, you can compile and install @command{gawk} by typing only two
commands. However, if you use an unusual system, you may need
to configure @command{gawk} for your system yourself.
@menu
* Quick Installation:: Compiling @command{gawk} under Unix.
* Shell Startup Files:: Shell convenience functions.
* Additional Configuration Options:: Other compile-time options.
* Configuration Philosophy:: How it's all supposed to work.
@end menu
@node Quick Installation
@appendixsubsec Compiling @command{gawk} for Unix-Like Systems
The normal installation steps should work on all modern commercial
Unix-derived systems, GNU/Linux, BSD-based systems, and the Cygwin
environment for MS-Windows.
After you have extracted the @command{gawk} distribution, @command{cd}
to @file{gawk-@value{VERSION}.@value{PATCHLEVEL}}. As with most GNU
software, you configure @command{gawk} for your system by running the
@command{configure} program. This program is a Bourne shell script that
is generated automatically using GNU Autoconf.
@ifnotinfo
(The Autoconf software is
described fully in
@cite{Autoconf---Generating Automatic Configuration Scripts},
which can be found online at
@uref{https://www.gnu.org/software/autoconf/manual/index.html,
the Free Software Foundation's website}.)
@end ifnotinfo
@ifinfo
(The Autoconf software is described fully starting with
@inforef{Top, , Autoconf, autoconf,Autoconf---Generating Automatic Configuration Scripts}.)
@end ifinfo
To configure @command{gawk}, simply run @command{configure}:
@example
sh ./configure
@end example
This produces a @file{Makefile} and @file{config.h} tailored to your system.
The @file{config.h} file describes various facts about your system.
You might want to edit the @file{Makefile} to
change the @code{CFLAGS} variable, which controls
the command-line options that are passed to the C compiler (such as
optimization levels or compiling for debugging).
Alternatively, you can add your own values for most @command{make}
variables on the command line, such as @code{CC} and @code{CFLAGS}, when
running @command{configure}:
@example
CC=cc CFLAGS=-g sh ./configure
@end example
@noindent
See the file @file{INSTALL} in the @command{gawk} distribution for
all the details.
After you have run @command{configure} and possibly edited the @file{Makefile},
type:
@example
make
@end example
@noindent
Shortly thereafter, you should have an executable version of @command{gawk}.
That's all there is to it!
To verify that @command{gawk} is working properly,
run @samp{make check}. All of the tests should succeed.
If these steps do not work, or if any of the tests fail,
check the files in the @file{README_d} directory to see if you've
found a known problem. If the failure is not described there,
send in a bug report (@pxref{Bugs}).
Of course, once you've built @command{gawk}, it is likely that you will
wish to install it. To do so, you need to run the command @samp{make
install}, as a user with the appropriate permissions. How to do this
varies by system, but on many systems you can use the @command{sudo}
command to do so. The command then becomes @samp{sudo make install}. It
is likely that you will be asked for your password, and you will have
to have been set up previously as a user who is allowed to run the
@command{sudo} command.
@node Shell Startup Files
@appendixsubsec Shell Startup Files
The distribution contains shell startup files @file{gawk.sh} and
@file{gawk.csh}, containing functions to aid in manipulating
the @env{AWKPATH} and @env{AWKLIBPATH} environment variables.
On a Fedora GNU/Linux system, these files should be installed in @file{/etc/profile.d};
on other platforms, the appropriate location may be different.
@table @command
@cindex @command{gawkpath_default} shell function
@cindex shell function @subentry @command{gawkpath_default}
@item gawkpath_default
Reset the @env{AWKPATH} environment variable to its default value.
@cindex @command{gawkpath_prepend} shell function
@cindex shell function @subentry @command{gawkpath_prepend}
@item gawkpath_prepend
Add the argument to the front of the @env{AWKPATH} environment variable.
@cindex @command{gawkpath_append} shell function
@cindex shell function @subentry @command{gawkpath_append}
@item gawkpath_append
Add the argument to the end of the @env{AWKPATH} environment variable.
@cindex @command{gawklibpath_default} shell function
@cindex shell function @subentry @command{gawklibpath_default}
@item gawklibpath_default
Reset the @env{AWKLIBPATH} environment variable to its default value.
@cindex @command{gawklibpath_prepend} shell function
@cindex shell function @subentry @command{gawklibpath_prepend}
@item gawklibpath_prepend
Add the argument to the front of the @env{AWKLIBPATH} environment variable.
@cindex @command{gawklibpath_append} shell function
@cindex shell function @subentry @command{gawklibpath_append}
@item gawklibpath_append
Add the argument to the end of the @env{AWKLIBPATH} environment variable.
@end table
@node Additional Configuration Options
@appendixsubsec Additional Configuration Options
@cindex @command{gawk} @subentry configuring @subentry options
@cindex configuration options, @command{gawk}
There are several additional options you may use on the @command{configure}
command line when compiling @command{gawk} from scratch, including:
@table @code
@cindex @option{--disable-extensions} configuration option
@cindex configuration option @subentry @code{--disable-extensions}
@item --disable-extensions
Disable the extension mechanism within @command{gawk}. With this
option, it is not possible to use dynamic extensions. This also
disables configuring and building the sample extensions in the
@file{extension} directory.
This option may be useful for cross-compiling.
The default action is to dynamically check if the extensions
can be configured and compiled.
@cindex @option{--disable-lint} configuration option
@cindex configuration option @subentry @code{--disable-lint}
@item --disable-lint
Disable all lint checking within @command{gawk}. The
@option{--lint} and @option{--lint-old} options
(@pxref{Options})
are accepted, but silently do nothing.
Similarly, setting the @code{LINT} variable
(@pxref{User-modified})
has no effect on the running @command{awk} program.
When used with the GNU Compiler Collection's (GCC's)
automatic dead-code-elimination, this option
cuts almost 23K bytes off the size of the @command{gawk}
executable on GNU/Linux x86_64 systems. Results on other systems and
with other compilers are likely to vary.
Using this option may bring you some slight performance improvement.
@quotation CAUTION
Using this option will cause some of the tests in the test suite
to fail. This option may be removed at a later date.
@end quotation
@cindex @option{--disable-mpfr} configuration option
@cindex configuration option @subentry @code{--disable-mpfr}
@item --disable-mpfr
Skip checking for the MPFR and GMP libraries. This is useful
mainly for the developers, to make sure nothing breaks if
MPFR support is not available.
@cindex @option{--disable-nls} configuration option
@cindex configuration option @subentry @code{--disable-nls}
@item --disable-nls
Disable all message-translation facilities.
This is usually not desirable, but it may bring you some slight performance
improvement.
@cindex @option{--enable-versioned-extension-dir} configuration option
@cindex configuration option @subentry @code{--enable-versioned-extension-dir}
@item --enable-versioned-extension-dir
Use a versioned directory for extensions. The directory name will
include the major and minor API versions in it. This makes it possible
to keep extensions for different API versions on the same system
without their conflicting with one another.
@end table
Use the command @samp{./configure --help} to see the full list of
options supplied by @command{configure}.
@node Configuration Philosophy
@appendixsubsec The Configuration Process
@cindex @command{gawk} @subentry configuring
This @value{SECTION} is of interest only if you know something about using the
C language and Unix-like operating systems.
The source code for @command{gawk} generally attempts to adhere to formal
standards wherever possible. This means that @command{gawk} uses library
routines that are specified by the ISO C standard and by the POSIX
operating system interface standard.
The @command{gawk} source code requires using an ISO C compiler (the 1990
standard).
Many Unix systems do not support all of either the ISO or the
POSIX standards. The @file{missing_d} subdirectory in the @command{gawk}
distribution contains replacement versions of those functions that are
most likely to be missing.
The @file{config.h} file that @command{configure} creates contains
definitions that describe features of the particular operating system
where you are attempting to compile @command{gawk}. The three things
described by this file are: what header files are available, so that
they can be correctly included, what (supposedly) standard functions
are actually available in your C libraries, and various miscellaneous
facts about your operating system. For example, there may not be an
@code{st_blksize} element in the @code{stat} structure. In this case,
@samp{HAVE_STRUCT_STAT_ST_BLKSIZE} is undefined.
@cindex @code{custom.h} file
It is possible for your C compiler to lie to @command{configure}. It may
do so by not exiting with an error when a library function is not
available. To get around this, edit the @file{custom.h} file.
Use an @samp{#ifdef} that is appropriate for your system, and either
@code{#define} any constants that @command{configure} should have defined but
didn't, or @code{#undef} any constants that @command{configure} defined and
should not have. The @file{custom.h} file is automatically included by
the @file{config.h} file.
It is also possible that the @command{configure} program generated by
Autoconf will not work on your system in some other fashion.
If you do have a problem, the @file{configure.ac} file is the input for
Autoconf. You may be able to change this file and generate a
new version of @command{configure} that works on your system
(@pxref{Bugs}
for information on how to report problems in configuring @command{gawk}).
The same mechanism may be used to send in updates to @file{configure.ac}
and/or @file{custom.h}.
@node Non-Unix Installation
@appendixsec Installation on Other Operating Systems
This @value{SECTION} describes how to install @command{gawk} on
various non-Unix systems.
@menu
* PC Installation:: Installing and Compiling @command{gawk} on
Microsoft Windows.
* VMS Installation:: Installing @command{gawk} on VMS.
@end menu
@node PC Installation
@appendixsubsec Installation on MS-Windows
@cindex PC operating systems, @command{gawk} on @subentry installing
@cindex operating systems @subentry PC, @command{gawk} on @subentry installing
This @value{SECTION} covers installation and usage of @command{gawk}
on Intel architecture machines running any version of MS-Windows.
In this @value{SECTION}, the term ``Windows32''
refers to any of Microsoft Windows 95/98/ME/NT/2000/XP/Vista/7/8/10.
See also the @file{README_d/README.pc} file in the distribution.
@menu
* PC Binary Installation:: Installing a prepared distribution.
* PC Compiling:: Compiling @command{gawk} for Windows32.
* PC Using:: Running @command{gawk} on Windows32.
* Cygwin:: Building and running @command{gawk} for
Cygwin.
* MSYS:: Using @command{gawk} In The MSYS Environment.
@end menu
@node PC Binary Installation
@appendixsubsubsec Installing a Prepared Distribution for MS-Windows Systems
@cindex installing @command{gawk} @subentry MS-Windows
The only supported binary distribution for MS-Windows systems
is that provided by Eli Zaretskii's @uref{https://sourceforge.net/projects/ezwinports/,
``ezwinports''} project. Install the compiled @command{gawk} from there.
@node PC Compiling
@appendixsubsubsec Compiling @command{gawk} for PC Operating Systems
@command{gawk} can be compiled for Windows32 using MinGW (Windows32).
The file @file{README_d/README.pc} in the @command{gawk} distribution
contains additional notes, and @file{pc/Makefile} contains important
information on compilation options.
@cindex compiling @command{gawk} @subentry for MS-Windows
To build @command{gawk} for Windows32, copy the files in
the @file{pc} directory (@emph{except} for @file{ChangeLog}) to the
directory with the rest of the @command{gawk} sources, then invoke
@command{make} with the appropriate target name as an argument to
build @command{gawk}. The @file{Makefile} copied from the @file{pc}
directory contains a configuration section with comments and may need
to be edited in order to work with your @command{make} utility.
The @file{Makefile} supports a number of targets for building various
MS-DOS and Windows32 versions. A list of targets is printed if the
@command{make} command is given without a target. As an example,
to build a native MS-Windows binary of @command{gawk} using the MinGW tools,
type @samp{make mingw32}.
@node PC Using
@appendixsubsubsec Using @command{gawk} on PC Operating Systems
@cindex operating systems @subentry PC, @command{gawk} on
@cindex PC operating systems, @command{gawk} on
Information in this section applies to the MinGW and
DJGPP ports of @command{gawk}. @xref{Cygwin} for information
about the Cygwin port.
Under MS-Windows, the MinGW environment supports
both the @samp{|&} operator and TCP/IP networking
(@pxref{TCP/IP Networking}).
The DJGPP environment does not support @samp{|&}.
@cindex search paths
@cindex search paths @subentry for source files
@cindex @command{gawk} @subentry MS-Windows version of
@cindex @code{;} (semicolon) @subentry @env{AWKPATH} variable and
@cindex semicolon (@code{;}) @subentry @env{AWKPATH} variable and
@cindex @env{AWKPATH} environment variable
@cindex environment variables @subentry @env{AWKPATH}
The MS-Windows version of @command{gawk} searches for
program files as described in @ref{AWKPATH Variable}. However,
semicolons (rather than colons) separate elements in the @env{AWKPATH}
variable. If @env{AWKPATH} is not set or is empty, then the default
search path is @samp{@w{.;c:/lib/awk;c:/gnu/lib/awk}}.
@cindex common extensions @subentry @code{BINMODE} variable
@cindex extensions @subentry common @subentry @code{BINMODE} variable
@cindex differences in @command{awk} and @command{gawk} @subentry @code{BINMODE} variable
@cindex @code{BINMODE} variable
Under MS-Windows,
@command{gawk} (and many other text programs) silently
translates end-of-line @samp{\r\n} to @samp{\n} on input and @samp{\n}
to @samp{\r\n} on output. A special @code{BINMODE} variable @value{COMMONEXT}
allows control over these translations and is interpreted as follows:
@itemize @value{BULLET}
@item
If @code{BINMODE} is @code{"r"} or one,
then
binary mode is set on read (i.e., no translations on reads).
@item
If @code{BINMODE} is @code{"w"} or two,
then
binary mode is set on write (i.e., no translations on writes).
@item
If @code{BINMODE} is @code{"rw"} or @code{"wr"} or three,
binary mode is set for both read and write.
@item
@code{BINMODE=@var{non-null-string}} is
the same as @samp{BINMODE=3} (i.e., no translations on
reads or writes). However, @command{gawk} issues a warning
message if the string is not one of @code{"rw"} or @code{"wr"}.
@end itemize
@noindent
The modes for standard input and standard output are set one time
only (after the
command line is read, but before processing any of the @command{awk} program).
Setting @code{BINMODE} for standard input or
standard output is accomplished by using an
appropriate @samp{-v BINMODE=@var{N}} option on the command line.
@code{BINMODE} is set at the time a file or pipe is opened and cannot be
changed midstream.
On POSIX-compatible systems, this variable's value has no effect.
Thus, if you think your program will run on multiple different systems
and that you may need to use @code{BINMODE}, you should simply set it
(in the program or on the command line) unconditionally, and not worry
about the operating system on which your program is running.
The name @code{BINMODE} was chosen to match @command{mawk}
(@pxref{Other Versions}).
@command{mawk} and @command{gawk} handle @code{BINMODE} similarly; however,
@command{mawk} adds a @samp{-W BINMODE=@var{N}} option and an environment
variable that can set @code{BINMODE}, @code{RS}, and @code{ORS}. The
files @file{binmode[1-3].awk} (under @file{gnu/lib/awk} in some of the
prepared binary distributions) have been chosen to match @command{mawk}'s @samp{-W
BINMODE=@var{N}} option. These can be changed or discarded; in particular,
the setting of @code{RS} giving the fewest ``surprises'' is open to debate.
@command{mawk} uses @samp{RS = "\r\n"} if binary mode is set on read, which is
appropriate for files with the MS-DOS-style end-of-line.
To illustrate, the following examples set binary mode on writes for standard
output and other files, and set @code{ORS} as the ``usual'' MS-DOS-style
end-of-line:
@example
gawk -v BINMODE=2 -v ORS="\r\n" @dots{}
@end example
@noindent
or:
@example
gawk -v BINMODE=w -f binmode2.awk @dots{}
@end example
@noindent
These give the same result as the @samp{-W BINMODE=2} option in
@command{mawk}.
The following changes the record separator to @code{"\r\n"} and sets binary
mode on reads, but does not affect the mode on standard input:
@example
gawk -v RS="\r\n" -e "BEGIN @{ BINMODE = 1 @}" @dots{}
@end example
@noindent
or:
@example
gawk -f binmode1.awk @dots{}
@end example
@noindent
With proper quoting, in the first example the setting of @code{RS} can be
moved into the @code{BEGIN} rule.
@node Cygwin
@appendixsubsubsec Using @command{gawk} In The Cygwin Environment
@cindex compiling @command{gawk} @subentry for Cygwin
@command{gawk} can be built and used ``out of the box'' under MS-Windows
if you are using the @uref{http://www.cygwin.com, Cygwin environment}.
This environment provides an excellent simulation of GNU/Linux, using
Bash, GCC, GNU Make,
and other GNU programs. Compilation and installation for Cygwin is the
same as for a Unix system:
@example
tar -xvpzf gawk-@value{VERSION}.@value{PATCHLEVEL}.tar.gz
cd gawk-@value{VERSION}.@value{PATCHLEVEL}
./configure
make && make check
@end example
When compared to GNU/Linux on the same system, the @samp{configure}
step on Cygwin takes considerably longer. However, it does finish,
and then the @samp{make} proceeds as usual.
@cindex installing @command{gawk} @subentry Cygwin
You may also install @command{gawk} using the regular Cygwin installer.
In general Cygwin supplies the latest released version.
Recent versions of Cygwin open all files in binary mode. This means
that you should use @samp{RS = "\r?\n"} in order to be able to
handle standard MS-Windows text files with carriage-return plus
line-feed line endings.
The Cygwin environment supports
both the @samp{|&} operator and TCP/IP networking
(@pxref{TCP/IP Networking}).
@node MSYS
@appendixsubsubsec Using @command{gawk} In The MSYS Environment
In the MSYS environment under MS-Windows, @command{gawk} automatically
uses binary mode for reading and writing files. Thus, there is no
need to use the @code{BINMODE} variable.
This can cause problems with other Unix-like components that have
been ported to MS-Windows that expect @command{gawk} to do automatic
translation of @code{"\r\n"}, because it won't.
Under MSYS2, compilation using the standard @samp{./configure && make}
recipe works ``out of the box.''
@node VMS Installation
@appendixsubsec Compiling and Installing @command{gawk} on Vax/VMS and OpenVMS
@c based on material from Pat Rankin <rankin@eql.caltech.edu>
@c now rankin@pactechdata.com
@c now r.pat.rankin@gmail.com
@cindex @command{gawk} @subentry VMS version of
@cindex installing @command{gawk} @subentry VMS
This @value{SUBSECTION} describes how to compile and install @command{gawk} under VMS.
The older designation ``VMS'' is used throughout to refer to OpenVMS.
@menu
* VMS Compilation:: How to compile @command{gawk} under VMS.
* VMS Dynamic Extensions:: Compiling @command{gawk} dynamic extensions on
VMS.
* VMS Installation Details:: How to install @command{gawk} under VMS.
* VMS Running:: How to run @command{gawk} under VMS.
* VMS GNV:: The VMS GNV Project.
* VMS Old Gawk:: An old version comes with some VMS systems.
@end menu
@node VMS Compilation
@appendixsubsubsec Compiling @command{gawk} on VMS
@cindex compiling @command{gawk} @subentry for VMS
To compile @command{gawk} under VMS, there is a @code{DCL} command procedure
that issues all the necessary @code{CC} and @code{LINK} commands. There is
also a @file{Makefile} for use with the @code{MMS} and @code{MMK} utilities.
From the source directory, use either:
@example
$ @kbd{@@[.vms]vmsbuild.com}
@end example
@noindent
or:
@example
$ @kbd{MMS/DESCRIPTION=[.vms]descrip.mms gawk}
@end example
@noindent
or:
@example
$ @kbd{MMK/DESCRIPTION=[.vms]descrip.mms gawk}
@end example
@command{MMK} is an open source, free, near-clone of @command{MMS} and
can better handle ODS-5 volumes with upper- and lowercase @value{FN}s.
@command{MMK} is available from @uref{https://github.com/endlesssoftware/mmk}.
With ODS-5 volumes and extended parsing enabled, the case of the target
parameter may need to be exact.
@command{gawk} has been tested under VAX/VMS 7.3 and Alpha/VMS 7.3-1
using Compaq C V6.4, and under Alpha/VMS 7.3, Alpha/VMS 7.3-2, and IA64/VMS 8.3.
The most recent builds used HP C V7.3 on Alpha VMS 8.3 and both
Alpha and IA64 VMS 8.4 used HP C 7.3.@footnote{The IA64 architecture
is also known as ``Itanium.''}
@xref{VMS GNV} for information on building
@command{gawk} as a PCSI kit that is compatible with the GNV product.
@node VMS Dynamic Extensions
@appendixsubsubsec Compiling @command{gawk} Dynamic Extensions on VMS
The extensions that have been ported to VMS can be built using one of
the following commands:
@example
$ @kbd{MMS/DESCRIPTION=[.vms]descrip.mms extensions}
@end example
@noindent
or:
@example
$ @kbd{MMK/DESCRIPTION=[.vms]descrip.mms extensions}
@end example
@command{gawk} uses @code{AWKLIBPATH} as either an environment variable
or a logical name to find the dynamic extensions.
Dynamic extensions need to be compiled with the same compiler options for
floating-point, pointer size, and symbol name handling as were used
to compile @command{gawk} itself.
Alpha and Itanium should use IEEE floating point. The pointer size is 32 bits,
and the symbol name handling should be exact case with CRC shortening for
symbols longer than 32 bits.
For Alpha and Itanium:
@example
/name=(as_is,short)
/float=ieee/ieee_mode=denorm_results
@end example
For VAX:
@example
/name=(as_is,short)
@end example
Compile-time macros need to be defined before the first VMS-supplied
header file is included, as follows:
@example
#if (__CRTL_VER >= 70200000) && !defined (__VAX)
#define _LARGEFILE 1
#endif
#ifndef __VAX
#ifdef __CRTL_VER
#if __CRTL_VER >= 80200000
#define _USE_STD_STAT 1
#endif
#endif
#endif
@end example
If you are writing your own extensions to run on VMS, you must supply these
definitions yourself. The @file{config.h} file created when building @command{gawk}
on VMS does this for you; if instead you use that file or a similar one, then you
must remember to include it before any VMS-supplied header files.
@node VMS Installation Details
@appendixsubsubsec Installing @command{gawk} on VMS
To use @command{gawk}, all you need is a ``foreign'' command, which is a
@code{DCL} symbol whose value begins with a dollar sign. For example:
@example
$ @kbd{GAWK :== $disk1:[gnubin]gawk}
@end example
@noindent
Substitute the actual location of @command{gawk.exe} for
@samp{$disk1:[gnubin]}. The symbol should be placed in the
@file{login.com} of any user who wants to run @command{gawk},
so that it is defined every time the user logs on.
Alternatively, the symbol may be placed in the system-wide
@file{sylogin.com} procedure, which allows all users
to run @command{gawk}.
If your @command{gawk} was installed by a PCSI kit into the
@file{GNV$GNU:} directory tree, the program will be known as
@file{GNV$GNU:[bin]gnv$gawk.exe} and the help file will be
@file{GNV$GNU:[vms_help]gawk.hlp}.
The PCSI kit also installs a @file{GNV$GNU:[vms_bin]gawk_verb.cld} file
that can be used to add @command{gawk} and @command{awk} as DCL commands.
For just the current process you can use:
@example
$ @kbd{set command gnv$gnu:[vms_bin]gawk_verb.cld}
@end example
Or the system manager can use @file{GNV$GNU:[vms_bin]gawk_verb.cld} to
add the @command{gawk} and @command{awk} to the system-wide @samp{DCLTABLES}.
The DCL syntax is documented in the @file{gawk.hlp} file.
Optionally, the @file{gawk.hlp} entry can be loaded into a VMS help library:
@example
$ @kbd{LIBRARY/HELP sys$help:helplib [.vms]gawk.hlp}
@end example
@noindent
(You may want to substitute a site-specific help library rather than
the standard VMS library @samp{HELPLIB}.) After loading the help text,
the command:
@example
$ @kbd{HELP GAWK}
@end example
@noindent
provides information about both the @command{gawk} implementation and the
@command{awk} programming language.
The logical name @samp{AWK_LIBRARY} can designate a default location
for @command{awk} program files. For the @option{-f} option, if the specified
@value{FN} has no device or directory path information in it, @command{gawk}
looks in the current directory first, then in the directory specified
by the translation of @samp{AWK_LIBRARY} if the file is not found.
If, after searching in both directories, the file still is not found,
@command{gawk} appends the suffix @samp{.awk} to the @value{FN} and retries
the file search. If @samp{AWK_LIBRARY} has no definition, a default value
of @samp{SYS$LIBRARY:} is used for it.
@node VMS Running
@appendixsubsubsec Running @command{gawk} on VMS
Command-line parsing and quoting conventions are significantly different
on VMS, so examples in this @value{DOCUMENT} or from other sources often need minor
changes. They @emph{are} minor though, and all @command{awk} programs
should run correctly.
Here are a couple of trivial tests:
@example
$ @kbd{gawk -- "BEGIN @{print ""Hello, World!""@}"}
$ @kbd{gawk -"W" version}
! could also be -"W version" or "-W version"
@end example
@noindent
Note that uppercase and mixed-case text must be quoted.
The VMS port of @command{gawk} includes a @code{DCL}-style interface in addition
to the original shell-style interface (see the help entry for details).
One side effect of dual command-line parsing is that if there is only a
single parameter (as in the quoted string program), the command
becomes ambiguous. To work around this, the normally optional @option{--}
flag is required to force Unix-style parsing rather than @code{DCL} parsing.
If any other dash-type options (or multiple parameters such as @value{DF}s to
process) are present, there is no ambiguity and @option{--} can be omitted.
@cindex exit status, of @command{gawk} @subentry on VMS
The @code{exit} value is a Unix-style value and is encoded into a VMS exit
status value when the program exits.
The VMS severity bits will be set based on the @code{exit} value.
A failure is indicated by 1, and VMS sets the @code{ERROR} status.
A fatal error is indicated by 2, and VMS sets the @code{FATAL} status.
All other values will have the @code{SUCCESS} status. The exit value is
encoded to comply with VMS coding standards and will have the
@code{C_FACILITY_NO} of @code{0x350000} with the constant @code{0xA000}
added to the number shifted over by 3 bits to make room for the severity codes.
To extract the actual @command{gawk} exit code from the VMS status, use:
@example
unix_status = (vms_status .and. %x7f8) / 8
@end example
@noindent
A C program that uses @code{exec()} to call @command{gawk} will get the original
Unix-style exit value.
Older versions of @command{gawk} for VMS treated a Unix exit code 0 as 1,
a failure as 2, a fatal error as 4, and passed all the other numbers through.
This violated the VMS exit status coding requirements.
@cindex floating-point @subentry numbers @subentry VAX/VMS
VAX/VMS floating point uses unbiased rounding. @xref{Round Function}.
VMS reports time values in GMT unless one of the @code{SYS$TIMEZONE_RULE}
or @code{TZ} logical names is set. Older versions of VMS, such as VAX/VMS
7.3, do not set these logical names.
@c @cindex directory search
@c @cindex path, search
@cindex search paths
@cindex search paths @subentry for source files
The default search path, when looking for @command{awk} program files specified
by the @option{-f} option, is @code{"SYS$DISK:[],AWK_LIBRARY:"}. The logical
name @env{AWKPATH} can be used to override this default. The format
of @env{AWKPATH} is a comma-separated list of directory specifications.
When defining it, the value should be quoted so that it retains a single
translation and not a multitranslation @code{RMS} searchlist.
@cindex redirection @subentry on VMS
This restriction also applies to running @command{gawk} under GNV,
as redirection is always to a DCL command.
If you are redirecting data to a VMS command or utility, the current
implementation requires that setting up a VMS foreign command that runs
a command file before invoking @command{gawk}.
(This restriction may be removed in a future release of @command{gawk} on VMS.)
Without this command file, the input data will also appear prepended
to the output data.
This also allows simulating POSIX commands that are not found on VMS or the
use of GNV utilities.
The example below is for @command{gawk} redirecting data to the VMS
@command{sort} command.
@example
$ sort = "@@device:[dir]vms_gawk_sort.com"
@end example
The command file needs to be of the format in the example below.
The first line inhibits the passed input data from also showing up in the
output. It must be in the format in the example.
The next line creates a foreign command that overrides the outer foreign
command which prevents an infinite recursion of command files.
The next to the last command redirects @code{sys$input} to be
@code{sys$command}, in order to pick up the data that is being redirected
to the command.
The last line runs the actual command. It must be the last command as the data
redirected from @command{gawk} will be read when the command file ends.
@example
$!'f$verify(0,0)'
$ sort := sort
$ define/user sys$input sys$command:
$ sort sys$input: sys$output:
@end example
@node VMS GNV
@appendixsubsubsec The VMS GNV Project
The VMS GNV package provides a build environment similar to POSIX with ports
of a collection of open source tools. The @command{gawk} found in the GNV
base kit is an older port. Currently, the GNV project is being reorganized
to supply individual PCSI packages for each component.
See @w{@uref{https://sourceforge.net/p/gnv/wiki/InstallingGNVPackages/}.}
The normal build procedure for @command{gawk} produces a program that
is suitable for use with GNV.
The file @file{vms/gawk_build_steps.txt} in the distribution documents
the procedure for building a VMS PCSI kit that is compatible with GNV.
@ignore
@c The VMS POSIX product, also known as POSIX for OpenVMS, is long defunct
@c and building gawk for it has not been tested in many years, but these
@c old instructions might still work if anyone is still using it.
@node VMS POSIX
@appendixsubsubsec Building and Using @command{gawk} on VMS POSIX
Ignore the instructions above, although @file{vms/gawk.hlp} should still
be made available in a help library. The source tree should be unpacked
into a container file subsystem rather than into the ordinary VMS filesystem.
Make sure that the two scripts, @file{configure} and
@file{vms/posix-cc.sh}, are executable; use @samp{chmod +x} on them if
necessary. Then execute the following two commands:
@example
psx> @kbd{CC=vms/posix-cc.sh configure}
psx> @kbd{make CC=c89 gawk}
@end example
@noindent
The first command constructs files @file{config.h} and @file{Makefile} out
of templates, using a script to make the C compiler fit @command{configure}'s
expectations. The second command compiles and links @command{gawk} using
the C compiler directly; ignore any warnings from @command{make} about being
unable to redefine @code{CC}. @command{configure} takes a very long
time to execute, but at least it provides incremental feedback as it runs.
This has been tested with VAX/VMS V6.2, VMS POSIX V2.0, and DEC C V5.2.
Once built, @command{gawk} works like any other shell utility. Unlike
the normal VMS port of @command{gawk}, no special command-line manipulation is
needed in the VMS POSIX environment.
@end ignore
@node VMS Old Gawk
@appendixsubsubsec Some VMS Systems Have An Old Version of @command{gawk}
@c Thanks to "gerard labadie" <gerard.labadie@gmail.com>
Some versions of VMS have an old version of @command{gawk}. To access it,
define a symbol, as follows:
@example
$ @kbd{gawk :== $sys$common:[syshlp.examples.tcpip.snmp]gawk.exe}
@end example
This is apparently @value{PVERSION} 2.15.6, which is extremely old. We
recommend compiling and using the current version.
@node Bugs
@appendixsec Reporting Problems and Bugs
@cindex archaeologists
@quotation
@i{There is nothing more dangerous than a bored archaeologist.}
@author Douglas Adams, @cite{The Hitchhiker's Guide to the Galaxy}
@end quotation
@c the radio show, not the book. :-)
@cindex debugging @command{gawk}, bug reports
@cindex troubleshooting @subentry @command{gawk} @subentry bug reports
If you have problems with @command{gawk} or think that you have found a bug,
report it to the developers; we cannot promise to do anything,
but we might well want to fix it.
@menu
* Bug address:: Where to send reports to.
* Usenet:: Where not to send reports to.
* Maintainers:: Maintainers of non-*nix ports.
@end menu
@node Bug address
@appendixsubsec Submitting Bug Reports
Before reporting a bug, make sure you have really found a genuine bug.
First, verify that you have the latest version of @command{gawk}.
Many bugs (usually subtle ones) are fixed at each release, and if yours
is out of date, the problem may already have been solved.
Second, please see if setting the environment variable @env{LC_ALL}
to @code{LC_ALL=C} causes things to behave as you expect. If so, it's
a locale issue, and may or may not really be a bug.
Third, carefully reread the documentation and see if it says you can do
what you're trying to do. If it's not clear whether you should be able
to do something or not, report that too; it's a bug in the documentation!
Finally, before reporting a bug or trying to fix it yourself, try to isolate it
to the smallest possible @command{awk} program and input @value{DF} that
reproduce the problem. Then send us the program and @value{DF},
some idea of what kind of Unix system you're using,
the compiler you used to compile @command{gawk}, and the exact results
@command{gawk} gave you. Also say what you expected to occur; this helps
us decide whether the problem is really in the documentation.
Make sure to include the version number of @command{gawk} you are using.
You can get this information with the command @samp{gawk --version}.
@cindex @code{bug-gawk@@gnu.org} bug reporting address
@cindex email address for bug reports, @code{bug-gawk@@gnu.org}
@cindex bug reports, email address, @code{bug-gawk@@gnu.org}
Once you have a precise problem description, send email to
@EMAIL{bug-gawk@@gnu.org,bug-gawk at gnu dot org}.
The @command{gawk} maintainers subscribe to this address, and
thus they will receive your bug report.
Although you can send mail to the maintainers directly,
the bug reporting address is preferred because the
email list is archived at the GNU Project.
@emph{All email must be in English. This is the only language
understood in common by all the maintainers.}
In addition, please be sure to send all mail in @emph{plain text},
not (or not exclusively) in HTML.
@quotation NOTE
Many distributions of GNU/Linux and the various BSD-based operating systems
have their own bug reporting systems. If you report a bug using your distribution's
bug reporting system, you should also send a copy to
@EMAIL{bug-gawk@@gnu.org,bug-gawk at gnu dot org}.
This is for two reasons. First, although some distributions forward
bug reports ``upstream'' to the GNU mailing list, many don't, so there is a good
chance that the @command{gawk} maintainers won't even see the bug report! Second,
mail to the GNU list is archived, and having everything at the GNU Project
keeps things self-contained and not dependent on other organizations.
@end quotation
Non-bug suggestions are always welcome as well. If you have questions
about things that are unclear in the documentation or are just obscure
features, ask on the bug list; we will try to help you out if we can.
Please note: We ask that you follow the
@uref{https://gnu.org/philosophy/kind-communication.html,
GNU Kind Communication Guidelines} in your correspondence on the
list (as well as off of it).
@node Usenet
@appendixsubsec Please Don't Post Bug Reports to USENET
@quotation
@c Date: Sun, 17 May 2015 19:50:14 -0400
@c From: Chet Ramey <chet.ramey@case.edu>
@c Reply-To: chet.ramey@case.edu
@c Organization: ITS, Case Western Reserve University
@c To: Aharon Robbins <arnold@skeeve.com>
@c CC: chet.ramey@case.edu
I gave up on Usenet a couple of years ago and haven't really looked back.
It's like sports talk radio---you feel smarter for not having read it.
@author Chet Ramey
@end quotation
@cindex @code{comp.lang.awk} newsgroup
Please do @emph{not} try to report bugs in @command{gawk} by posting to the
Usenet/Internet newsgroup @code{comp.lang.awk}. Although some of the
@command{gawk} developers occasionally read this news group, the primary
@command{gawk} maintainer no longer does. Thus it's virtually guaranteed
that he will @emph{not} see your posting.
Similarly, posting bug reports or questions in web forums (such
as @uref{https://stackoverflow.com/, Stack Overflow}) may get you
an answer, but it won't be from the @command{gawk} maintainers,
who do not spend their time in web forums. The steps described here are
the only officially recognized way for reporting bugs. Really.
@ignore
And another one:
Date: Thu, 11 Jun 2015 09:00:56 -0400
From: Chet Ramey <chet.ramey@case.edu>
My memory was imperfect. Back in June 2009, I wrote:
"That's the nice thing about open source, right? You can take your ball
and run to another section of the playground. Then, if you like mixing
metaphors, you can throw rocks from there."
@end ignore
@node Maintainers
@appendixsubsec Reporting Problems with Non-Unix Ports
If you find bugs in one of the non-Unix ports of @command{gawk},
send an email to the bug list, with a copy to the
person who maintains that port. The maintainers are named in the following list,
as well as in the @file{README} file in the @command{gawk} distribution.
Information in the @file{README} file should be considered authoritative
if it conflicts with this @value{DOCUMENT}.
The people maintaining the various @command{gawk} ports are:
@c put the index entries outside the table, for docbook
@cindex Buening, Andreas
@cindex Malmberg, John
@cindex G., Daniel Richard
@cindex Robbins @subentry Arnold
@cindex Zaretskii, Eli
@cindex Guerrero, Juan Manuel
@multitable {MS-Windows with MinGW} {123456789012345678901234567890123456789001234567890}
@item Unix and POSIX systems @tab Arnold Robbins, @EMAIL{arnold@@skeeve.com,arnold at skeeve dot com}
@item MS-DOS with DJGPP @tab Juan Manuel Guerrero, @EMAIL{juan.guerrero@@gmx.de, juan dot guerrero at gmx dot de}
@item MS-Windows with MinGW @tab Eli Zaretskii, @EMAIL{eliz@@gnu.org,eliz at gnu dot org}
@c Leave this in the document on purpose.
@c OS/2 is not mentioned anywhere else though.
@item OS/2 @tab Andreas Buening, @EMAIL{andreas.buening@@nexgo.de,andreas dot buening at nexgo dot de}
@item VMS @tab John Malmberg, @EMAIL{wb8tyw@@qsl.net,wb8tyw at qsl.net}
@item z/OS (OS/390) @tab Daniel Richard G.@: @EMAIL{skunk@@iSKUNK.ORG,skunk at iSKUNK.ORG}
@end multitable
If your bug is also reproducible under Unix, send a copy of your
report to the @EMAIL{bug-gawk@@gnu.org,bug-gawk at gnu dot org} email list as well.
@node Other Versions
@appendixsec Other Freely Available @command{awk} Implementations
@cindex @command{awk} @subentry implementations
@ignore
From: emory!amc.com!brennan (Michael Brennan)
Subject: C++ comments in awk programs
To: arnold@gnu.ai.mit.edu (Arnold Robbins)
Date: Wed, 4 Sep 1996 08:11:48 -0700 (PDT)
@end ignore
@cindex Brennan, Michael
@ifnotdocbook
@quotation
@i{It's kind of fun to put comments like this in your awk code:}@*
@ @ @ @ @ @ @code{// Do C++ comments work? answer: yes! of course}
@author Michael Brennan
@end quotation
@end ifnotdocbook
@docbook
<blockquote><attribution>Michael Brennan</attribution>
<literallayout><emphasis>It's kind of fun to put comments like this in your awk code.</emphasis>
<literal>// Do C++ comments work? answer: yes! of course</literal></literallayout>
</blockquote>
@end docbook
There are a number of other freely available @command{awk} implementations.
This @value{SECTION} briefly describes where to get them:
@table @asis
@cindex Kernighan, Brian
@cindex source code @subentry Brian Kernighan's @command{awk}
@cindex @command{awk} @subentry versions of @seealso{Brian Kernighan's @command{awk}}
@cindex Brian Kernighan's @command{awk} @subentry source code
@item Unix @command{awk}
Brian Kernighan, one of the original designers of Unix @command{awk},
has made his implementation of
@command{awk} freely available.
You can retrieve it from GitHub:
@cindex @command{git} utility
@example
git clone git://github.com/onetrueawk/awk bwkawk
@end example
@noindent
This command creates a copy of the @uref{https://git-scm.com, Git}
repository in a directory named @file{bwkawk}. If you omit the last argument
from the @command{git} command line, the repository copy is created in a
directory named @file{awk}.
This version requires an ISO C (1990 standard) compiler; the C compiler
from GCC (the GNU Compiler Collection) works quite nicely.
To build it, review the settings in the @file{makefile}, and then just run
@command{make}. Note that the result of compilation is named
@command{a.out}; you will have to rename it to something reasonable.
@xref{Common Extensions}
for a list of extensions in this @command{awk} that are not in POSIX @command{awk}.
As a side note, Dan Bornstein has created a Git repository tracking
all the versions of BWK @command{awk} that he could find. It's
available at @uref{git://github.com/danfuzz/one-true-awk}.
@cindex Brennan, Michael
@cindex @command{mawk} utility
@cindex source code @subentry @command{mawk}
@item @command{mawk}
Michael Brennan wrote an independent implementation of @command{awk},
called @command{mawk}. It is available under the
@ifclear FOR_PRINT
GPL (@pxref{Copying}),
@end ifclear
@ifset FOR_PRINT
GPL,
@end ifset
just as @command{gawk} is.
The original distribution site for the @command{mawk} source code
no longer has it. A copy is available at
@uref{http://www.skeeve.com/gawk/mawk1.3.3.tar.gz}.
In 2009, Thomas Dickey took on @command{mawk} maintenance.
Basic information is available on
@uref{http://www.invisible-island.net/mawk, the project's web page}.
The download URL is
@url{http://invisible-island.net/datafiles/release/mawk.tar.gz}.
Once you have it,
@command{gunzip} may be used to decompress this file. Installation
is similar to @command{gawk}'s
(@pxref{Unix Installation}).
@xref{Common Extensions}
for a list of extensions in @command{mawk} that are not in POSIX @command{awk}.
@item @command{mawk} 2.0
In 2016, Michael Brennan resumed @command{mawk} development.
His development snapshots are available via Git from the project's
@uref{https://github.com/mikebrennan000/mawk-2, GitHub page}.
@cindex Sumner, Andrew
@cindex @command{awka} compiler for @command{awk}
@cindex source code @subentry @command{awka}
@item @command{awka}
Written by Andrew Sumner,
@command{awka} translates @command{awk} programs into C, compiles them,
and links them with a library of functions that provide the core
@command{awk} functionality.
It also has a number of extensions.
The @command{awk} translator is released under the GPL, and the library
is under the LGPL.
To get @command{awka}, go to @url{https://sourceforge.net/projects/awka}.
@c You can reach Andrew Sumner at @email{andrew@@zbcom.net}.
@c andrewsumner@@yahoo.net
The project seems to be frozen; no new code changes have been made
since approximately 2001.
@cindex Beebe, Nelson H.F.@:
@cindex @command{pawk} (profiling version of Brian Kernighan's @command{awk})
@cindex source code @subentry @command{pawk} (profiling version of Brian Kernighan's @command{awk})
@item @command{pawk}
Nelson H.F.@: Beebe at the University of Utah has modified
BWK @command{awk} to provide timing and profiling information.
It is different from @command{gawk} with the @option{--profile} option
(@pxref{Profiling})
in that it uses CPU-based profiling, not line-count
profiling. You may find it at either
@uref{ftp://ftp.math.utah.edu/pub/pawk/pawk-20030606.tar.gz}
or
@uref{http://www.math.utah.edu/pub/pawk/pawk-20030606.tar.gz}.
@item BusyBox @command{awk}
@cindex BusyBox Awk
@cindex source code @subentry BusyBox Awk
BusyBox is a GPL-licensed program providing small versions of many
applications within a single executable. It is aimed at embedded systems.
It includes a full implementation of POSIX @command{awk}. When building
it, be careful not to do @samp{make install} as it will overwrite
copies of other applications in your @file{/usr/local/bin}. For more
information, see the @uref{https://busybox.net, project's home page}.
@cindex OpenSolaris
@cindex Solaris, POSIX-compliant @command{awk}
@cindex source code @subentry Solaris @command{awk}
@item The OpenSolaris POSIX @command{awk}
The versions of @command{awk} in @file{/usr/xpg4/bin} and
@file{/usr/xpg6/bin} on Solaris are more or less POSIX-compliant.
They are based on the @command{awk} from Mortice Kern Systems for PCs.
We were able to make this code compile and work under GNU/Linux
with 1--2 hours of work. Making it more generally portable (using
GNU Autoconf and/or Automake) would take more work, and this
has not been done, at least to our knowledge.
@cindex Illumos, POSIX-compliant @command{awk}
@cindex source code @subentry Illumos @command{awk}
The source code used to be available from the OpenSolaris website.
However, that project was ended and the website shut down. Fortunately, the
@uref{https://wiki.illumos.org/display/illumos/illumos+Home, Illumos project}
makes this implementation available. You can view the files one at a time from
@uref{https://github.com/joyent/illumos-joyent/blob/master/usr/src/cmd/awk_xpg4}.
@cindex @command{goawk}
@cindex Go implementation of @command{awk}
@cindex source code @subentry @command{goawk}
@cindex programming languages @subentry Go
@item @command{goawk}
This is an @command{awk} interpreter written in the
@uref{https://golang.org/, Go programming language}.
It implements POSIX @command{awk}, with a few minor extensions.
Source code is available from @uref{https://github.com/benhoyt/goawk}.
The author wrote a nice
@uref{https://benhoyt.com/writings/goawk/, article}
describing the implementation.
@cindex @command{jawk}
@cindex Java implementation of @command{awk}
@cindex source code @subentry @command{jawk}
@item @command{jawk}
This is an interpreter for @command{awk} written in Java. It claims
to be a full interpreter, although because it uses Java facilities
for I/O and for regexp matching, the language it supports is different
from POSIX @command{awk}. More information is available on the
@uref{https://jawk.sourceforge.net, project's home page}.
@item Libmawk
@cindex libmawk
@cindex source code @subentry libmawk
This is an embeddable @command{awk} interpreter derived from
@command{mawk}. For more information, see
@uref{http://repo.hu/projects/libmawk/}.
@cindex source code @subentry embeddable @command{awk} interpreter
@cindex Neacsu, Mircea
@item Mircea Neacsu's Embeddable @command{awk}
Mircea Neacsu has created an embeddable @command{awk}
interpreter, based on BWK awk. It's available
at @uref{https://github.com/neacsum/awk}.
@item @code{pawk}
@cindex source code @subentry @command{pawk} (Python version)
@cindex @code{pawk}, @command{awk}-like facilities for Python
This is a Python module that claims to bring @command{awk}-like
features to Python. See @uref{https://github.com/alecthomas/pawk}
for more information. (This is not related to Nelson Beebe's
modified version of BWK @command{awk}, described earlier.)
@item @w{QSE @command{awk}}
@cindex QSE @command{awk}
@cindex source code @subentry QSE @command{awk}
This is an embeddable @command{awk} interpreter. For more information,
see @uref{https://code.google.com/p/qse/}. @c and @uref{http://awk.info/?tools/qse}.
@item @command{QTawk}
@cindex QuikTrim Awk
@cindex source code @subentry QuikTrim Awk
This is an independent implementation of @command{awk} distributed
under the GPL. It has a large number of extensions over standard
@command{awk} and may not be 100% syntactically compatible with it.
See @uref{http://www.quiktrim.org/QTawk.html} for more information,
including the manual. The download link there is out of date; see
@uref{http://www.quiktrim.org/#AdditionalResources} for the latest
download link.
The project may also be frozen; no new code changes have been made
since approximately 2014.
@item Other versions
See also the ``Versions and implementations'' section of the
@uref{https://en.wikipedia.org/wiki/Awk_language#Versions_and_implementations,
Wikipedia article} on @command{awk} for information on additional versions.
@end table
@node Installation summary
@appendixsec Summary
@itemize @value{BULLET}
@item
The @command{gawk} distribution is available from the GNU Project's main
distribution site, @code{ftp.gnu.org}. The canonical build recipe is:
@example
wget https://ftp.gnu.org/gnu/gawk/gawk-@value{VERSION}.@value{PATCHLEVEL}.tar.gz
tar -xvpzf gawk-@value{VERSION}.@value{PATCHLEVEL}.tar.gz
cd gawk-@value{VERSION}.@value{PATCHLEVEL}
./configure && make && make check
@end example
@quotation NOTE
Because of the @samp{https://} URL, you may have to supply the
@option{--no-check-certificate} option to @command{wget} to download
the file.
@end quotation
@item
@command{gawk} may be built on non-POSIX systems as well. The currently
supported systems are MS-Windows using
MSYS, MSYS2, DJGPP, MinGW, and Cygwin,
@c OS/2,
and both Vax/VMS and OpenVMS.
Instructions for each system are included in this @value{APPENDIX}.
@item
Bug reports should be sent via email to @email{bug-gawk@@gnu.org}.
Bug reports should be in English and should include the version of @command{gawk},
how it was compiled, and a short program and @value{DF} that demonstrate
the problem.
@item
There are a number of other freely available @command{awk}
implementations. Many are POSIX-compliant; others are less so.
@end itemize
@ifclear FOR_PRINT
@node Notes
@appendix Implementation Notes
@cindex @command{gawk} @subentry implementation issues
@cindex implementation issues, @command{gawk}
This appendix contains information mainly of interest to implementers and
maintainers of @command{gawk}. Everything in it applies specifically to
@command{gawk} and not to other implementations.
@menu
* Compatibility Mode:: How to disable certain @command{gawk}
extensions.
* Additions:: Making Additions To @command{gawk}.
* Future Extensions:: New features that may be implemented one day.
* Implementation Limitations:: Some limitations of the implementation.
* Extension Design:: Design notes about the extension API.
* Notes summary:: Summary of implementation notes.
@end menu
@node Compatibility Mode
@appendixsec Downward Compatibility and Debugging
@cindex @command{gawk} @subentry implementation issues @subentry downward compatibility
@cindex @command{gawk} @subentry implementation issues @subentry debugging
@cindex troubleshooting @subentry @command{gawk}
@cindex implementation issues, @command{gawk} @subentry debugging
@xref{POSIX/GNU},
for a summary of the GNU extensions to the @command{awk} language and program.
All of these features can be turned off by invoking @command{gawk} with the
@option{--traditional} option or with the @option{--posix} option.
If @command{gawk} is compiled for debugging with @samp{-DDEBUG}, then there
is one more option available on the command line:
@table @code
@item -Y
@itemx --parsedebug
Print out the parse stack information as the program is being parsed.
@end table
This option is intended only for serious @command{gawk} developers
and not for the casual user. It probably has not even been compiled into
your version of @command{gawk}, since it slows down execution.
@node Additions
@appendixsec Making Additions to @command{gawk}
If you find that you want to enhance @command{gawk} in a significant
fashion, you are perfectly free to do so. That is the point of having
free software; the source code is available and you are free to change
it as you want (@pxref{Copying}).
This @value{SECTION} discusses the ways you might want to change @command{gawk}
as well as any considerations you should bear in mind.
@menu
* Accessing The Source:: Accessing the Git repository.
* Adding Code:: Adding code to the main body of
@command{gawk}.
* New Ports:: Porting @command{gawk} to a new operating
system.
* Derived Files:: Why derived files are kept in the Git
repository.
@end menu
@node Accessing The Source
@appendixsubsec Accessing The @command{gawk} Git Repository
As @command{gawk} is Free Software, the source code is always available.
@ref{Gawk Distribution} describes how to get and build the formal,
released versions of @command{gawk}.
@cindex @command{git} utility
However, if you want to modify @command{gawk} and contribute back your
changes, you will probably wish to work with the development version.
To do so, you will need to access the @command{gawk} source code
repository. The code is maintained using the
@uref{https://git-scm.com, Git distributed version control system}.
You will need to install it if your system doesn't have it.
Once you have done so, use the command:
@example
git clone git://git.savannah.gnu.org/gawk.git
@end example
@noindent
This clones the @command{gawk} repository. If you are behind a
firewall that does not allow you to use the Git native protocol, you
can still access the repository using:
@example
git clone https://git.savannah.gnu.org/r/gawk.git
@end example
Once you have made changes, you can use @samp{git diff} to produce a
patch, and send that to the @command{gawk} maintainer; see @ref{Bugs},
for how to do that.
Once upon a time there was Git--CVS gateway for use by people who could
not install Git. However, this gateway no longer works, so you may have
better luck using a more modern version control system like Bazaar,
that has a Git plug-in for working with Git repositories.
@node Adding Code
@appendixsubsec Adding New Features
@cindex adding @subentry features to @command{gawk}
@cindex features @subentry adding to @command{gawk}
@cindex @command{gawk} @subentry features @subentry adding
You are free to add any new features you like to @command{gawk}.
However, if you want your changes to be incorporated into the @command{gawk}
distribution, there are several steps that you need to take in order to
make it possible to include them:
@enumerate 1
@item
Before building the new feature into @command{gawk} itself,
consider writing it as an extension
(@pxref{Dynamic Extensions}).
If that's not possible, continue with the rest of the steps in this list.
@item
Be prepared to sign the appropriate paperwork.
In order for the FSF to distribute your changes, you must either place
those changes in the public domain and submit a signed statement to that
effect, or assign the copyright in your changes to the FSF.
Both of these actions are easy to do and @emph{many} people have done so
already. If you have questions, please contact me
(@pxref{Bugs}),
or @EMAIL{assign@@gnu.org,assign at gnu dot org}.
@item
Get the latest version.
It is much easier for me to integrate changes if they are relative to
the most recent distributed version of @command{gawk}, or better yet,
relative to the latest code in the Git repository. If your version of
@command{gawk} is very old, I may not be able to integrate your changes at all.
(@xref{Getting},
for information on getting the latest version of @command{gawk}.)
@item
@ifnotinfo
Follow the @cite{GNU Coding Standards}.
@end ifnotinfo
@ifinfo
See @inforef{Top, , Version, standards, GNU Coding Standards}.
@end ifinfo
This document describes how GNU software should be written. If you haven't
read it, please do so, preferably @emph{before} starting to modify @command{gawk}.
(The @cite{GNU Coding Standards} are available from
the GNU Project's
@uref{https://www.gnu.org/prep/standards/, website}.
Texinfo, Info, and DVI versions are also available.)
@cindex @command{gawk} @subentry coding style in
@item
Use the @command{gawk} coding style.
The C code for @command{gawk} follows the instructions in the
@cite{GNU Coding Standards}, with minor exceptions. The code is formatted
using the traditional ``K&R'' style, particularly as regards to the placement
of braces and the use of TABs. In brief, the coding rules for @command{gawk}
are as follows:
@itemize @value{BULLET}
@item
Use ANSI/ISO style (prototype) function headers when defining functions.
@item
Put the name of the function at the beginning of its own line.
@item
Use @samp{#elif} instead of nesting @samp{#if} inside @samp{#else}.
@item
Put the return type of the function, even if it is @code{int}, on the
line above the line with the name and arguments of the function.
@item
Put spaces around parentheses used in control structures
(@code{if}, @code{while}, @code{for}, @code{do}, @code{switch},
and @code{return}).
@item
Do not put spaces in front of parentheses used in function calls.
@item
Put spaces around all C operators and after commas in function calls.
@item
Do not use the comma operator to produce multiple side effects, except
in @code{for} loop initialization and increment parts, and in macro bodies.
@item
Use real TABs for indenting, not spaces.
@item
Use the ``K&R'' brace layout style.
@item
Use comparisons against @code{NULL} and @code{'\0'} in the conditions of
@code{if}, @code{while}, and @code{for} statements, as well as in the @code{case}s
of @code{switch} statements, instead of just the
plain pointer or character value.
@item
Use @code{true} and @code{false} for @code{bool} values,
the @code{NULL} symbolic constant for pointer values,
and the character constant @code{'\0'} where appropriate, instead of @code{1}
and @code{0}.
@item
Provide one-line descriptive comments for each function.
@item
Do not use the @code{alloca()} function for allocating memory off the
stack. Its use causes more portability trouble than is worth the minor
benefit of not having to free the storage. Instead, use @code{malloc()}
and @code{free()}.
@item
Do not use comparisons of the form @samp{! strcmp(a, b)} or similar.
As Henry Spencer once said, ``@code{strcmp()} is not a boolean!''
Instead, use @samp{strcmp(a, b) == 0}.
@item
If adding new bit flag values, use explicit hexadecimal constants
(@code{0x001}, @code{0x002}, @code{0x004}, and so on) instead of
shifting one left by successive amounts (@samp{(1<<0)}, @samp{(1<<1)},
and so on).
@end itemize
@quotation NOTE
If I have to reformat your code to follow the coding style used in
@command{gawk}, I may not bother to integrate your changes at all.
@end quotation
@cindex Texinfo
@item
Update the documentation.
Along with your new code, please supply new sections and/or chapters
for this @value{DOCUMENT}. If at all possible, please use real
Texinfo, instead of just supplying unformatted ASCII text (although
even that is better than no documentation at all).
Conventions to be followed in @cite{@value{TITLE}} are provided
after the @samp{@@bye} at the end of the Texinfo source file.
If possible, please update the @command{man} page as well.
You will also have to sign paperwork for your documentation changes.
@cindex @command{git} utility
@item
Submit changes as unified diffs.
Use @samp{diff -u -r -N} to compare
the original @command{gawk} source tree with your version.
I recommend using the GNU version of @command{diff}, or best of all,
@samp{git diff} or @samp{git format-patch}.
Send the output produced by @command{diff} to me when you
submit your changes.
(@xref{Bugs}, for the electronic mail
information.)
Using this format makes it easy for me to apply your changes to the
master version of the @command{gawk} source code (using @code{patch}).
If I have to apply the changes manually, using a text editor, I may
not do so, particularly if there are lots of changes.
@item
Include an entry for the @file{ChangeLog} file with your submission.
This helps further minimize the amount of work I have to do,
making it easier for me to accept patches.
It is simplest if you just make this part of your diff.
@end enumerate
Although this sounds like a lot of work, please remember that while you
may write the new code, I have to maintain it and support it. If it
isn't possible for me to do that with a minimum of extra work, then I
probably will not.
@node New Ports
@appendixsubsec Porting @command{gawk} to a New Operating System
@cindex portability @subentry @command{gawk}
@cindex operating systems @subentry porting @command{gawk} to
@cindex porting @command{gawk}
If you want to port @command{gawk} to a new operating system, there are
several steps:
@enumerate 1
@item
Follow the guidelines in
@ifinfo
@ref{Adding Code},
@end ifinfo
@ifnotinfo
the previous @value{SECTION}
@end ifnotinfo
concerning coding style, submission of diffs, and so on.
@item
Be prepared to sign the appropriate paperwork.
In order for the FSF to distribute your code, you must either place
your code in the public domain and submit a signed statement to that
effect, or assign the copyright in your code to the FSF.
Both of these actions are easy to do and @emph{many} people have done so
already. If you have questions, please contact me, or
@email{gnu@@gnu.org}.
@item
When doing a port, bear in mind that your code must coexist peacefully
with the rest of @command{gawk} and the other ports. Avoid gratuitous
changes to the system-independent parts of the code. If at all possible,
avoid sprinkling @samp{#ifdef}s just for your port throughout the
code.
If the changes needed for a particular system affect too much of the
code, I probably will not accept them. In such a case, you can, of course,
distribute your changes on your own, as long as you comply
with the GPL
(@pxref{Copying}).
@item
A number of the files that come with @command{gawk} are maintained by other
people. Thus, you should not change them
unless it is for a very good reason; i.e., changes are not out of the
question, but changes to these files are scrutinized extra carefully.
These are all the files in the @file{support} directory
within the @command{gawk} distribution. See there.
@item
A number of other files are provided by the GNU
Autotools (Autoconf, Automake, and GNU @command{gettext}).
You should not change them either, unless it is for a very
good reason. The files are
@file{ABOUT-NLS},
@file{config.guess},
@file{config.rpath},
@file{config.sub},
@file{depcomp},
@file{INSTALL},
@file{install-sh},
@file{missing},
@file{mkinstalldirs},
and
@file{ylwrap}.
@item
Be willing to continue to maintain the port.
Non-Unix operating systems are supported by volunteers who maintain
the code needed to compile and run @command{gawk} on their systems. If no-one
volunteers to maintain a port, it becomes unsupported and it may
be necessary to remove it from the distribution.
@item
Supply an appropriate @file{gawkmisc.???} file.
Each port has its own @file{gawkmisc.???} that implements certain
operating system specific functions. This is cleaner than a plethora of
@samp{#ifdef}s scattered throughout the code. The @file{gawkmisc.c} in
the main source directory includes the appropriate
@file{gawkmisc.???} file from each subdirectory.
Be sure to update it as well.
Each port's @file{gawkmisc.???} file has a suffix reminiscent of the machine
or operating system for the port---for example, @file{pc/gawkmisc.pc} and
@file{vms/gawkmisc.vms}. The use of separate suffixes, instead of plain
@file{gawkmisc.c}, makes it possible to move files from a port's subdirectory
into the main subdirectory, without accidentally destroying the real
@file{gawkmisc.c} file. (Currently, this is only an issue for the
PC operating system ports.)
@item
Supply a @file{Makefile} as well as any other C source and header files that are
necessary for your operating system. All your code should be in a
separate subdirectory, with a name that is the same as, or reminiscent
of, either your operating system or the computer system. If possible,
try to structure things so that it is not necessary to move files out
of the subdirectory into the main source directory. If that is not
possible, then be sure to avoid using names for your files that
duplicate the names of files in the main source directory.
@item
Update the documentation.
Please write a section (or sections) for this @value{DOCUMENT} describing the
installation and compilation steps needed to compile and/or install
@command{gawk} for your system.
@end enumerate
Following these steps makes it much easier to integrate your changes
into @command{gawk} and have them coexist happily with other
operating systems' code that is already there.
In the code that you supply and maintain, feel free to use a
coding style and brace layout that suits your taste.
@node Derived Files
@appendixsubsec Why Generated Files Are Kept In Git
@cindex Git, use of for @command{gawk} source code
@c From emails written March 22, 2012, to the gawk developers list.
If you look at the @command{gawk} source in the Git
repository, you will notice that it includes files that are automatically
generated by GNU infrastructure tools, such as @file{Makefile.in} from
Automake and even @file{configure} from Autoconf.
This is different from many Free Software projects that do not store
the derived files, because that keeps the repository less cluttered,
and it is easier to see the substantive changes when comparing versions
and trying to understand what changed between commits.
However, there are several reasons why the @command{gawk} maintainer
likes to have everything in the repository.
First, because it is then easy to reproduce any given version completely,
without relying upon the availability of (older, likely obsolete, and
maybe even impossible to find) other tools.
As an extreme example, if you ever even think about trying to compile,
oh, say, the V7 @command{awk}, you will discover that not only do you
have to bootstrap the V7 @command{yacc} to do so, but you also need the
V7 @command{lex}. And the latter is pretty much impossible to bring up
on a modern GNU/Linux system.@footnote{We tried. It was painful.}
(Or, let's say @command{gawk} 1.2 required @command{bison} whatever-it-was
in 1989 and that there was no @file{awkgram.c} file in the repository. Is
there a guarantee that we could find that @command{bison} version? Or that
@emph{it} would build?)
If the repository has all the generated files, then it's easy to just check
them out and build. (Or @emph{easier}, depending upon how far back we go.)
And that brings us to the second (and stronger) reason why all the files
really need to be in Git. It boils down to who do you cater
to---the @command{gawk} developer(s), or the user who just wants to check
out a version and try it out?
The @command{gawk} maintainer
wants it to be possible for any interested @command{awk} user in the
world to just clone the repository, check out the branch of interest and
build it. Without their having to have the correct version(s) of the
autotools.@footnote{There is one GNU program that is (in our opinion)
severely difficult to bootstrap from the Git repository. For
example, on the author's old (but still working) PowerPC Macintosh with
Mac OS X 10.5, it was necessary to bootstrap a ton of software, starting
with Git itself, in order to try to work with the latest code.
It's not pleasant, and especially on older systems, it's a big waste
of time.
Starting with the latest tarball was no picnic either. The maintainers
had dropped @file{.gz} and @file{.bz2} files and only distribute
@file{.tar.xz} files. It was necessary to bootstrap @command{xz} first!}
That is the point of the @file{bootstrap.sh} file. It touches the
various other files in the right order such that
@example
# The canonical incantation for building GNU software:
./bootstrap.sh && ./configure && make
@end example
@noindent
will @emph{just work}.
This is extremely important for the @code{master} and
@code{gawk-@var{X}.@var{Y}-stable} branches.
Further, the @command{gawk} maintainer would argue that it's also
important for the @command{gawk} developers. When he tried to check out
the @code{xgawk} branch@footnote{A branch (since removed) created by one of the other
developers that did not include the generated files.} to build it, he
couldn't. (No @file{ltmain.sh} file, and he had no idea how to create it,
and that was not the only problem.)
He felt @emph{extremely} frustrated. With respect to that branch,
the maintainer is no different than Jane User who wants to try to build
@code{gawk-4.1-stable} or @code{master} from the repository.
Thus, the maintainer thinks that it's not just important, but critical,
that for any given branch, the above incantation @emph{just works}.
@c Added 9/2014:
A third reason to have all the files is that without them, using @samp{git
bisect} to try to find the commit that introduced a bug is exceedingly
difficult. The maintainer tried to do that on another project that
requires running bootstrapping scripts just to create @command{configure}
and so on; it was really painful. When the repository is self-contained,
using @command{git bisect} in it is very easy.
@c So - that's my reasoning and philosophy.
What are some of the consequences and/or actions to take?
@enumerate 1
@item
We don't mind that there are differing files in the different branches
as a result of different versions of the autotools.
@enumerate A
@item
It's the maintainer's job to merge them and he will deal with it.
@item
He is really good at @samp{git diff x y > /tmp/diff1 ; gvim /tmp/diff1} to
remove the diffs that aren't of interest in order to review code.
@end enumerate
@item
It would certainly help if everyone used the same versions of the GNU tools
as he does, which in general are the latest released versions of
Automake,
Autoconf,
@command{bison},
GNU @command{gettext},
and
Libtool.
@ignore
If it would help if I sent out an ``I just upgraded to version x.y
of tool Z'' kind of message to this list, I can do that. Up until
now it hasn't been a real issue since I'm the only one who's been
dorking with the configuration machinery.
@end ignore
@c @enumerate A
@c @item
Installing from source is quite easy. It's how the maintainer worked for years
(and still works).
He had @file{/usr/local/bin} at the front of his @env{PATH} and just did:
@example
wget https://ftp.gnu.org/gnu/@var{package}/@var{package}-@var{x}.@var{y}.@var{z}.tar.gz
tar -xpzvf @var{package}-@var{x}.@var{y}.@var{z}.tar.gz
cd @var{package}-@var{x}.@var{y}.@var{z}
./configure && make && make check
make install # as root
@end example
@quotation NOTE
Because of the @samp{https://} URL, you may have to supply the
@option{--no-check-certificate} option to @command{wget} to download
the file.
@end quotation
@c @item
@ignore
These days the maintainer uses Ubuntu 12.04 which is medium current, but
he is already doing the above for Automake, Autoconf, and @command{bison}.
@end ignore
@ignore
(C. Rant: Recent Linux versions with GNOME 3 really suck. What
are all those people thinking? Fedora 15 was such a bust it drove
me to Ubuntu, but Ubuntu 11.04 and 11.10 are totally unusable from
a UI perspective. Bleah.)
@end ignore
@c @end enumerate
@ignore
@item
If someone still feels really strongly about all this, then perhaps they
can have two branches, one for their development with just the clean
changes, and one that is buildable (xgawk and xgawk-buildable, maybe).
Or, as I suggested in another mail, make commits in pairs, the first with
the "real" changes and the second with "everything else needed for
building".
@end ignore
@end enumerate
Most of the above was originally written by the maintainer to other
@command{gawk} developers. It raised the objection from one of
the developers ``@dots{} that anybody pulling down the source from
Git is not an end user.''
However, this is not true. There are ``power @command{awk} users''
who can build @command{gawk} (using the magic incantation shown previously)
but who can't program in C. Thus, the major branches should be
kept buildable all the time.
It was then suggested that there be a @command{cron} job to create
nightly tarballs of ``the source.'' Here, the problem is that there
are source trees, corresponding to the various branches! So,
nightly tarballs aren't the answer, especially as the repository can go
for weeks without significant change being introduced.
Fortunately, the Git server can meet this need. For any given
branch named @var{branchname}, use:
@example
wget https://git.savannah.gnu.org/cgit/gawk.git/snapshot/gawk-@var{branchname}.tar.gz
@end example
@noindent
to retrieve a snapshot of the given branch.
@node Future Extensions
@appendixsec Probable Future Extensions
@ignore
From emory!scalpel.netlabs.com!lwall Tue Oct 31 12:43:17 1995
Return-Path: <emory!scalpel.netlabs.com!lwall>
Message-Id: <9510311732.AA28472@scalpel.netlabs.com>
To: arnold@skeeve.atl.ga.us (Arnold D. Robbins)
Subject: Re: May I quote you?
In-Reply-To: Your message of "Tue, 31 Oct 95 09:11:00 EST."
<m0tAHPQ-00014MC@skeeve.atl.ga.us>
Date: Tue, 31 Oct 95 09:32:46 -0800
From: Larry Wall <emory!scalpel.netlabs.com!lwall>
: Greetings. I am working on the release of gawk 3.0. Part of it will be a
: thoroughly updated manual. One of the sections deals with planned future
: extensions and enhancements. I have the following at the beginning
: of it:
:
: @cindex PERL
: @cindex Wall, Larry
: @display
: @i{AWK is a language similar to PERL, only considerably more elegant.} @*
: Arnold Robbins
: @sp 1
: @i{Hey!} @*
: Larry Wall
: @end display
:
: Before I actually release this for publication, I wanted to get your
: permission to quote you. (Hopefully, in the spirit of much of GNU, the
: implied humor is visible... :-)
I think that would be fine.
Larry
@end ignore
@cindex Perl
@cindex Wall, Larry
@cindex Robbins @subentry Arnold
@quotation
@i{AWK is a language similar to PERL, only considerably more elegant.}
@author Arnold Robbins
@end quotation
@quotation
@i{Hey!}
@author Larry Wall
@end quotation
The @file{TODO} file in the @code{master} branch of the @command{gawk}
Git repository lists possible future enhancements. Some of these relate
to the source code, and others to possible new features. Please see
that file for the list.
@xref{Additions},
if you are interested in tackling any of the projects listed there.
@node Implementation Limitations
@appendixsec Some Limitations of the Implementation
This following table describes limits of @command{gawk} on a Unix-like
system (although it is variable even then). Other systems may have
different limits.
@multitable @columnfractions .40 .60
@headitem Item @tab Limit
@item Characters in a character class @tab 2^(number of bits per byte)
@item Length of input record @tab @code{MAX_INT}
@item Length of output record @tab Unlimited
@item Length of source line @tab Unlimited
@item Number of fields in a record @tab @code{MAX_LONG}
@item Number of file redirections @tab Unlimited
@item Number of input records in one file @tab @code{MAX_LONG}
@item Number of input records total @tab @code{MAX_LONG}
@item Number of pipe redirections @tab min(number of processes per user, number of open files)
@item Numeric values @tab Double-precision floating point (if not using MPFR)
@item Size of a field @tab @code{MAX_INT}
@item Size of a literal string @tab @code{MAX_INT}
@item Size of a printf string @tab @code{MAX_INT}
@end multitable
@node Extension Design
@appendixsec Extension API Design
This @value{SECTION} documents the design of the extension API,
including a discussion of some of the history and problems that needed
to be solved.
The first version of extensions for @command{gawk} was developed in
the mid-1990s and released with @command{gawk} 3.1 in the late 1990s.
The basic mechanisms and design remained unchanged for close to 15 years,
until 2012.
The old extension mechanism used data types and functions from
@command{gawk} itself, with a ``clever hack'' to install extension
functions.
@command{gawk} included some sample extensions, of which a few were
really useful. However, it was clear from the outset that the extension
mechanism was bolted onto the side and was not really well thought out.
@menu
* Old Extension Problems:: Problems with the old mechanism.
* Extension New Mechanism Goals:: Goals for the new mechanism.
* Extension Other Design Decisions:: Some other design decisions.
* Extension Future Growth:: Some room for future growth.
@end menu
@node Old Extension Problems
@appendixsubsec Problems With The Old Mechanism
The old extension mechanism had several problems:
@itemize @value{BULLET}
@item
It depended heavily upon @command{gawk} internals. Any time the
@code{NODE} structure@footnote{A critical central data structure
inside @command{gawk}.} changed, an extension would have to be
recompiled. Furthermore, to really write extensions required understanding
something about @command{gawk}'s internal functions. There was some
documentation in this @value{DOCUMENT}, but it was quite minimal.
@item
Being able to call into @command{gawk} from an extension required linker
facilities that are common on Unix-derived systems but that did
not work on MS-Windows systems; users wanting extensions on MS-Windows
had to statically link them into @command{gawk}, even though MS-Windows supports
dynamic loading of shared objects.
@item
The API would change occasionally as @command{gawk} changed; no compatibility
between versions was ever offered or planned for.
@end itemize
Despite the drawbacks, the @command{xgawk} project developers forked
@command{gawk} and developed several significant extensions. They also
enhanced @command{gawk}'s facilities relating to file inclusion and
shared object access.
A new API was desired for a long time, but only in 2012 did the
@command{gawk} maintainer and the @command{xgawk} developers finally
start working on it together. More information about the @command{xgawk}
project is provided in @ref{gawkextlib}.
@node Extension New Mechanism Goals
@appendixsubsec Goals For A New Mechanism
Some goals for the new API were:
@itemize @value{BULLET}
@item
The API should be independent of @command{gawk} internals. Changes in
@command{gawk} internals should not be visible to the writer of an
extension function.
@item
The API should provide @emph{binary} compatibility across @command{gawk}
releases as long as the API itself does not change.
@item
The API should enable extensions written in C or C++ to have roughly the
same ``appearance'' to @command{awk}-level code as @command{awk}
functions do. This means that extensions should have:
@itemize @value{MINUS}
@item
The ability to access function parameters.
@item
The ability to turn an undefined parameter into an array (call by reference).
@item
The ability to create, access and update global variables.
@item
Easy access to all the elements of an array at once (``array flattening'')
in order to loop over all the element in an easy fashion for C code.
@item
The ability to create arrays (including @command{gawk}'s true
arrays of arrays).
@end itemize
@end itemize
Some additional important goals were:
@itemize @value{BULLET}
@item
The API should use only features in ISO C 90, so that extensions
can be written using the widest range of C and C++ compilers. The header
should include the appropriate @samp{#ifdef __cplusplus} and @samp{extern "C"}
magic so that a C++ compiler could be used. (If using C++, the runtime
system has to be smart enough to call any constructors and destructors,
as @command{gawk} is a C program. As of this writing, this has not been
tested.)
@item
The API mechanism should not require access to @command{gawk}'s
symbols@footnote{The @dfn{symbols} are the variables and functions
defined inside @command{gawk}. Access to these symbols by code
external to @command{gawk} loaded dynamically at runtime is
problematic on MS-Windows.} by the compile-time or dynamic linker,
in order to enable creation of extensions that also work on MS-Windows.
@end itemize
During development, it became clear that there were other features
that should be available to extensions, which were also subsequently
provided:
@itemize @value{BULLET}
@item
Extensions should have the ability to hook into @command{gawk}'s
I/O redirection mechanism. In particular, the @command{xgawk}
developers provided a so-called ``open hook'' to take over reading
records. During development, this was generalized to allow
extensions to hook into input processing, output processing, and
two-way I/O.
@item
An extension should be able to provide a ``call back'' function
to perform cleanup actions when @command{gawk} exits.
@item
An extension should be able to provide a version string so that
@command{gawk}'s @option{--version} option can provide information
about extensions as well.
@end itemize
The requirement to avoid access to @command{gawk}'s symbols is, at first
glance, a difficult one to meet.
One design, apparently used by Perl and Ruby and maybe others, would
be to make the mainline @command{gawk} code into a library, with the
@command{gawk} utility a small C @code{main()} function linked against
the library.
This seemed like the tail wagging the dog, complicating build and
installation and making a simple copy of the @command{gawk} executable
from one system to another (or one place to another on the same
system!) into a chancy operation.
Pat Rankin suggested the solution that was adopted.
@xref{Extension Mechanism Outline}, for the details.
@node Extension Other Design Decisions
@appendixsubsec Other Design Decisions
As an arbitrary design decision, extensions can read the values of
predefined variables and arrays (such as @code{ARGV} and @code{FS}), but cannot
change them, with the exception of @code{PROCINFO}.
The reason for this is to prevent an extension function from affecting
the flow of an @command{awk} program outside its control. While a real
@command{awk} function can do what it likes, that is at the discretion
of the programmer. An extension function should provide a service or
make a C API available for use within @command{awk}, and not mess with
@code{FS} or @code{ARGC} and @code{ARGV}.
In addition, it becomes easy to start down a slippery slope. How
much access to @command{gawk} facilities do extensions need?
Do they need @code{getline}? What about calling @code{gsub()} or
compiling regular expressions? What about calling into @command{awk}
functions? (@emph{That} would be messy.)
In order to avoid these issues, the @command{gawk} developers chose
to start with the simplest, most basic features that are still truly useful.
Another decision is that although @command{gawk} provides nice things like
MPFR, and arrays indexed internally by integers, these features are not
being brought out to the API in order to keep things simple and close to
traditional @command{awk} semantics. (In fact, arrays indexed internally
by integers are so transparent that they aren't even documented!)
Additionally, all functions in the API check that their pointer
input parameters are not @code{NULL}. If they are, they return an error.
(It is a good idea for extension code to verify that
pointers received from @command{gawk} are not @code{NULL}.
Such a thing should not happen, but the @command{gawk} developers
are only human, and they have been known to occasionally make
mistakes.)
With time, the API will undoubtedly evolve; the @command{gawk} developers
expect this to be driven by user needs. For now, the current API seems
to provide a minimal yet powerful set of features for creating extensions.
@node Extension Future Growth
@appendixsubsec Room For Future Growth
The API can later be expanded, in at least the following way:
@itemize @value{BULLET}
@item
@command{gawk} passes an ``extension id'' into the extension when it
first loads the extension. The extension then passes this id back
to @command{gawk} with each function call. This mechanism allows
@command{gawk} to identify the extension calling into it, should it need
to know.
@end itemize
Of course, as of this writing, no decisions have been made with respect
to the above.
@node Notes summary
@appendixsec Summary
@itemize @value{BULLET}
@item
@command{gawk}'s extensions can be disabled with either the
@option{--traditional} option or with the @option{--posix} option.
The @option{--parsedebug} option is available if @command{gawk} is
compiled with @samp{-DDEBUG}.
@item
The source code for @command{gawk} is maintained in a publicly
accessible Git repository. Anyone may check it out and view the source.
@item
Contributions to @command{gawk} are welcome. Following the steps
outlined in this @value{CHAPTER} will make it easier to integrate
your contributions into the code base.
This applies both to new feature contributions and to ports to
additional operating systems.
@item
@command{gawk} has some limits---generally those that are imposed by
the machine architecture.
@item
The extension API design was intended to solve a number of problems
with the previous extension mechanism, enable features needed by
the @code{xgawk} project, and provide binary compatibility going forward.
@item
The previous extension mechanism is no longer supported and was
removed from the code base with the 4.2 release.
@end itemize
@node Basic Concepts
@appendix Basic Programming Concepts
@cindex programming @subentry concepts
@cindex programming @subentry concepts
This @value{APPENDIX} attempts to define some of the basic concepts
and terms that are used throughout the rest of this @value{DOCUMENT}.
As this @value{DOCUMENT} is specifically about @command{awk},
and not about computer programming in general, the coverage here
is by necessity fairly cursory and simplistic.
(If you need more background, there are many
other introductory texts that you should refer to instead.)
@menu
* Basic High Level:: The high level view.
* Basic Data Typing:: A very quick intro to data types.
@end menu
@node Basic High Level
@appendixsec What a Program Does
@cindex processing data
At the most basic level, the job of a program is to process
some input data and produce results.
@ifnotdocbook
See @ref{figure-general-flow}.
@end ifnotdocbook
@ifdocbook
See @inlineraw{docbook, <xref linkend="figure-general-flow"/>}.
@end ifdocbook
@ifnotdocbook
@float Figure,figure-general-flow
@caption{General Program Flow}
@center @image{gawk_general-program, , , General program flow}
@end float
@end ifnotdocbook
@docbook
<figure id="figure-general-flow" float="0">
<title>General Program Flow</title>
<mediaobject>
<imageobject role="web"><imagedata fileref="gawk_general-program.png" format="PNG"/></imageobject>
</mediaobject>
</figure>
@end docbook
@cindex compiled programs
@cindex interpreted programs
The ``program'' in the figure can be either a compiled
program@footnote{Compiled programs are typically written
in lower-level languages such as C, C++, or Ada,
and then translated, or @dfn{compiled}, into a form that
the computer can execute directly.}
(such as @command{ls}),
or it may be @dfn{interpreted}. In the latter case, a machine-executable
program such as @command{awk} reads your program, and then uses the
instructions in your program to process the data.
@cindex programming @subentry basic steps
When you write a program, it usually consists
of the following, very basic set of steps,
@ifnotdocbook
as shown in @ref{figure-process-flow}:
@end ifnotdocbook
@ifdocbook
as shown in @inlineraw{docbook, <xref linkend="figure-process-flow"/>}:
@end ifdocbook
@ifnotdocbook
@float Figure,figure-process-flow
@caption{Basic Program Steps}
@center @image{gawk_process-flow, , , Basic Program Stages}
@end float
@end ifnotdocbook
@docbook
<figure id="figure-process-flow" float="0">
<title>Basic Program Stages</title>
<mediaobject>
<imageobject role="web"><imagedata fileref="gawk_process-flow.png" format="PNG"/></imageobject>
</mediaobject>
</figure>
@end docbook
@table @asis
@item Initialization
These are the things you do before actually starting to process
data, such as checking arguments, initializing any data you need
to work with, and so on.
This step corresponds to @command{awk}'s @code{BEGIN} rule
(@pxref{BEGIN/END}).
If you were baking a cake, this might consist of laying out all the
mixing bowls and the baking pan, and making sure you have all the
ingredients that you need.
@item Processing
This is where the actual work is done. Your program reads data,
one logical chunk at a time, and processes it as appropriate.
In most programming languages, you have to manually manage the reading
of data, checking to see if there is more each time you read a chunk.
@command{awk}'s pattern-action paradigm
(@pxref{Getting Started})
handles the mechanics of this for you.
In baking a cake, the processing corresponds to the actual labor:
breaking eggs, mixing the flour, water, and other ingredients, and then putting the cake
into the oven.
@item Clean Up
Once you've processed all the data, you may have things you need to
do before exiting.
This step corresponds to @command{awk}'s @code{END} rule
(@pxref{BEGIN/END}).
After the cake comes out of the oven, you still have to wrap it in
plastic wrap to keep anyone from tasting it, as well as wash
the mixing bowls and utensils.
@end table
@cindex algorithms
An @dfn{algorithm} is a detailed set of instructions necessary to accomplish
a task, or process data. It is much the same as a recipe for baking
a cake. Programs implement algorithms. Often, it is up to you to design
the algorithm and implement it, simultaneously.
@cindex records
@cindex fields
The ``logical chunks'' we talked about previously are called @dfn{records},
similar to the records a company keeps on employees, a school keeps for
students, or a doctor keeps for patients.
Each record has many component parts, such as first and last names,
date of birth, address, and so on. The component parts are referred
to as the @dfn{fields} of the record.
The act of reading data is termed @dfn{input}, and that of
generating results, not too surprisingly, is termed @dfn{output}.
They are often referred to together as ``input/output,''
and even more often, as ``I/O'' for short.
(You will also see ``input'' and ``output'' used as verbs.)
@cindex data-driven languages
@cindex languages, data-driven
@command{awk} manages the reading of data for you, as well as the
breaking it up into records and fields. Your program's job is to
tell @command{awk} what to do with the data. You do this by describing
@dfn{patterns} in the data to look for, and @dfn{actions} to execute
when those patterns are seen. This @dfn{data-driven} nature of
@command{awk} programs usually makes them both easier to write
and easier to read.
@node Basic Data Typing
@appendixsec Data Values in a Computer
@cindex variables
In a program,
you keep track of information and values in things called @dfn{variables}.
A variable is just a name for a given value, such as @code{first_name},
@code{last_name}, @code{address}, and so on.
@command{awk} has several predefined variables, and it has
special names to refer to the current input record
and the fields of the record.
You may also group multiple
associated values under one name, as an array.
@cindex values @subentry numeric
@cindex values @subentry string
@cindex scalar values
Data, particularly in @command{awk}, consists of either numeric
values, such as 42 or 3.1415927, or string values.
String values are essentially anything that's not a number, such as a name.
Strings are sometimes referred to as @dfn{character data}, since they
store the individual characters that comprise them.
Individual variables, as well as numeric and string variables, are
referred to as @dfn{scalar} values.
Groups of values, such as arrays, are not scalars.
@ref{Computer Arithmetic}, provided a basic introduction to numeric
types (integer and floating-point) and how they are used in a computer.
Please review that information, including a number of caveats that
were presented.
@cindex null strings
While you are probably used to the idea of a number without a value (i.e., zero),
it takes a bit more getting used to the idea of zero-length character data.
Nevertheless, such a thing exists.
It is called the @dfn{null string}.
The null string is character data that has no value.
In other words, it is empty. It is written in @command{awk} programs
like this: @code{""}.
Humans are used to working in decimal; i.e., base 10. In base 10,
numbers go from 0 to 9, and then ``roll over'' into the next
@iftex
column. (Remember grade school? @math{42 = 4\times 10 + 2}.)
@end iftex
@ifnottex
column. (Remember grade school? 42 = 4 x 10 + 2.)
@end ifnottex
There are other number bases though. Computers commonly use base 2
or @dfn{binary}, base 8 or @dfn{octal}, and base 16 or @dfn{hexadecimal}.
In binary, each column represents two times the value in the column to
its right. Each column may contain either a 0 or a 1.
@iftex
Thus, binary 1010 represents @math{(1\times 8) + (0\times 4) + (1\times 2) + (0\times 1)}, or decimal 10.
@end iftex
@ifnottex
Thus, binary 1010 represents (1 x 8) + (0 x 4) + (1 x 2)
+ (0 x 1), or decimal 10.
@end ifnottex
Octal and hexadecimal are discussed more in
@ref{Nondecimal-numbers}.
At the very lowest level, computers store values as groups of binary digits,
or @dfn{bits}. Modern computers group bits into groups of eight, called @dfn{bytes}.
Advanced applications sometimes have to manipulate bits directly,
and @command{gawk} provides functions for doing so.
Programs are written in programming languages.
Hundreds, if not thousands, of programming languages exist.
One of the most popular is the C programming language.
The C language had a very strong influence on the design of
the @command{awk} language.
@cindex Kernighan, Brian
@cindex Ritchie, Dennis
There have been several versions of C. The first is often referred to
as ``K&R'' C, after the initials of Brian Kernighan and Dennis Ritchie,
the authors of the first book on C. (Dennis Ritchie created the language,
and Brian Kernighan was one of the creators of @command{awk}.)
In the mid-1980s, an effort began to produce an international standard
for C. This work culminated in 1989, with the production of the ANSI
standard for C. This standard became an ISO standard in 1990.
In 1999, a revised ISO C standard was approved and released.
Where it makes sense, POSIX @command{awk} is compatible with 1999 ISO C.
@node Glossary
@unnumbered Glossary
@table @asis
@item Action
A series of @command{awk} statements attached to a rule. If the rule's
pattern matches an input record, @command{awk} executes the
rule's action. Actions are always enclosed in braces.
(@xref{Action Overview}.)
@cindex Ada programming language
@cindex programming languages @subentry Ada
@item Ada
A programming language originally defined by the U.S.@: Department of
Defense for embedded programming. It was designed to enforce good
Software Engineering practices.
@cindex Spencer, Henry
@cindex @command{sed} utility
@cindex amazing @command{awk} assembler (@command{aaa})
@cindex @command{aaa} (amazing @command{awk} assembler) program
@item Amazing @command{awk} Assembler
Henry Spencer at the University of Toronto wrote a retargetable assembler
completely as @command{sed} and @command{awk} scripts. It is thousands
of lines long, including machine descriptions for several eight-bit
microcomputers. It is a good example of a program that would have been
better written in another language.
@c You can get it from @uref{http://awk.info/?awk100/aaa}.
@cindex amazingly workable formatter (@command{awf})
@cindex @command{awf} (amazingly workable formatter) program
@item Amazingly Workable Formatter (@command{awf})
Henry Spencer at the University of Toronto wrote a formatter that accepts
a large subset of the @samp{nroff -ms} and @samp{nroff -man} formatting
commands, using @command{awk} and @command{sh}.
@c It is available
@c from @uref{http://awk.info/?tools/awf}.
@item Anchor
The regexp metacharacters @samp{^} and @samp{$}, which force the match
to the beginning or end of the string, respectively.
@cindex ANSI
@item ANSI
The American National Standards Institute. This organization produces
many standards, among them the standards for the C and C++ programming
languages.
These standards often become international standards as well. See also
``ISO.''
@item Argument
An argument can be two different things. It can be an option or a
@value{FN} passed to a command while invoking it from the command line, or
it can be something passed to a @dfn{function} inside a program, e.g.
inside @command{awk}.
In the latter case, an argument can be passed to a function in two ways.
Either it is given to the called function by value, i.e., a copy of the
value of the variable is made available to the called function, but the
original variable cannot be modified by the function itself; or it is
given by reference, i.e., a pointer to the interested variable is passed to
the function, which can then directly modify it. In @command{awk}
scalars are passed by value, and arrays are passed by reference.
See ``Pass By Value/Reference.''
@item Array
A grouping of multiple values under the same name.
Most languages just provide sequential arrays.
@command{awk} provides associative arrays.
@item Assertion
A statement in a program that a condition is true at this point in the program.
Useful for reasoning about how a program is supposed to behave.
@item Assignment
An @command{awk} expression that changes the value of some @command{awk}
variable or data object. An object that you can assign to is called an
@dfn{lvalue}. The assigned values are called @dfn{rvalues}.
@xref{Assignment Ops}.
@item Associative Array
Arrays in which the indices may be numbers or strings, not just
sequential integers in a fixed range.
@item @command{awk} Language
The language in which @command{awk} programs are written.
@item @command{awk} Program
An @command{awk} program consists of a series of @dfn{patterns} and
@dfn{actions}, collectively known as @dfn{rules}. For each input record
given to the program, the program's rules are all processed in turn.
@command{awk} programs may also contain function definitions.
@item @command{awk} Script
Another name for an @command{awk} program.
@item Bash
The GNU version of the standard shell
@ifnotinfo
(the @b{B}ourne-@b{A}gain @b{SH}ell).
@end ifnotinfo
@ifinfo
(the Bourne-Again SHell).
@end ifinfo
See also ``Bourne Shell.''
@item Binary
Base-two notation, where the digits are @code{0}--@code{1}. Since
electronic circuitry works ``naturally'' in base 2 (just think of Off/On),
everything inside a computer is calculated using base 2. Each digit
represents the presence (or absence) of a power of 2 and is called a
@dfn{bit}. So, for example, the base-two number @code{10101} is
@iftex
the same as decimal 21, (@math{(1\times 16) + (1\times 4) + (1\times 1)}).
@end iftex
@ifnottex
the same as decimal 21, ((1 x 16) + (1 x 4) + (1 x 1)).
@end ifnottex
Since base-two numbers quickly become
very long to read and write, they are usually grouped by 3 (i.e., they are
read as octal numbers), or by 4 (i.e., they are read as hexadecimal
numbers). There is no direct way to insert base 2 numbers in a C program.
If need arises, such numbers are usually inserted as octal or hexadecimal
numbers. The number of base-two digits that fit into registers used for
representing integer numbers in computers is a rough indication of the
computing power of the computer itself. Most computers nowadays use 64
bits for representing integer numbers in their registers, but 32-bit,
16-bit and 8-bit registers have been widely used in the past.
@xref{Nondecimal-numbers}.
@item Bit
Short for ``Binary Digit.''
All values in computer memory ultimately reduce to binary digits: values
that are either zero or one.
Groups of bits may be interpreted differently---as integers,
floating-point numbers, character data, addresses of other
memory objects, or other data.
@command{awk} lets you work with floating-point numbers and strings.
@command{gawk} lets you manipulate bit values with the built-in
functions described in
@ref{Bitwise Functions}.
Computers are often defined by how many bits they use to represent integer
values. Typical systems are 32-bit systems, but 64-bit systems are
becoming increasingly popular, and 16-bit systems have essentially
disappeared.
@item Boolean Expression
Named after the English mathematician Boole. See also ``Logical Expression.''
@item Bourne Shell
The standard shell (@file{/bin/sh}) on Unix and Unix-like systems,
originally written by Steven R.@: Bourne at Bell Laboratories.
Many shells (Bash, @command{ksh}, @command{pdksh}, @command{zsh}) are
generally upwardly compatible with the Bourne shell.
@item Braces
The characters @samp{@{} and @samp{@}}. Braces are used in
@command{awk} for delimiting actions, compound statements, and function
bodies.
@item Bracket Expression
Inside a @dfn{regular expression}, an expression included in square
brackets, meant to designate a single character as belonging to a
specified character class. A bracket expression can contain a list of one
or more characters, like @samp{[abc]}, a range of characters, like
@samp{[A-Z]}, or a name, delimited by @samp{:}, that designates a known set
of characters, like @samp{[:digit:]}. The form of bracket expression
enclosed between @samp{:} is independent of the underlying representation
of the character themselves, which could utilize the ASCII, EBCDIC, or
Unicode codesets, depending on the architecture of the computer system, and on
localization.
See also ``Regular Expression.''
@item Built-in Function
The @command{awk} language provides built-in functions that perform various
numerical, I/O-related, and string computations. Examples are
@code{sqrt()} (for the square root of a number) and @code{substr()} (for a
substring of a string).
@command{gawk} provides functions for timestamp management, bit manipulation,
array sorting, type checking,
and runtime string translation.
(@xref{Built-in}.)
@item Built-in Variable
@code{ARGC},
@code{ARGV},
@code{CONVFMT},
@code{ENVIRON},
@code{FILENAME},
@code{FNR},
@code{FS},
@code{NF},
@code{NR},
@code{OFMT},
@code{OFS},
@code{ORS},
@code{RLENGTH},
@code{RSTART},
@code{RS},
and
@code{SUBSEP}
are the variables that have special meaning to @command{awk}.
In addition,
@code{ARGIND},
@code{BINMODE},
@code{ERRNO},
@code{FIELDWIDTHS},
@code{FPAT},
@code{IGNORECASE},
@code{LINT},
@code{PROCINFO},
@code{RT},
and
@code{TEXTDOMAIN}
are the variables that have special meaning to @command{gawk}.
Changing some of them affects @command{awk}'s running environment.
(@xref{Built-in Variables}.)
@item C
The system programming language that most GNU software is written in. The
@command{awk} programming language has C-like syntax, and this @value{DOCUMENT}
points out similarities between @command{awk} and C when appropriate.
In general, @command{gawk} attempts to be as similar to the 1990 version
of ISO C as makes sense.
@item C Shell
The C Shell (@command{csh} or its improved version, @command{tcsh}) is a Unix shell that was
created by Bill Joy in the late 1970s. The C shell was differentiated from
other shells by its interactive features and overall style, which
looks more like C. The C Shell is not backward compatible with the Bourne
Shell, so special attention is required when converting scripts
written for other Unix shells to the C shell, especially with regard to the management of
shell variables.
See also ``Bourne Shell.''
@item C++
A popular object-oriented programming language derived from C.
@item Character Class
See ``Bracket Expression.''
@item Character List
See ``Bracket Expression.''
@cindex ASCII
@cindex ISO @subentry ISO 8859-1 character set
@cindex ISO @subentry ISO Latin-1 character set
@cindex character sets (machine character encodings)
@cindex Unicode
@item Character Set
The set of numeric codes used by a computer system to represent the
characters (letters, numbers, punctuation, etc.) of a particular country
or place. The most common character set in use today is ASCII (American
Standard Code for Information Interchange). Many European
countries use an extension of ASCII known as ISO-8859-1 (ISO Latin-1).
The @uref{http://www.unicode.org, Unicode character set} is
increasingly popular and standard, and is particularly
widely used on GNU/Linux systems.
@cindex Kernighan, Brian
@cindex Bentley, Jon
@cindex @command{chem} utility
@item CHEM
A preprocessor for @command{pic} that reads descriptions of molecules
and produces @command{pic} input for drawing them.
It was written in @command{awk}
by Brian Kernighan and Jon Bentley, and is available from
@uref{http://netlib.org/typesetting/chem}.
@item Comparison Expression
A relation that is either true or false, such as @samp{a < b}.
Comparison expressions are used in @code{if}, @code{while}, @code{do},
and @code{for}
statements, and in patterns to select which input records to process.
(@xref{Typing and Comparison}.)
@cindex compiled programs
@item Compiler
A program that translates human-readable source code into
machine-executable object code. The object code is then executed
directly by the computer.
See also ``Interpreter.''
@item Complemented Bracket Expression
The negation of a @dfn{bracket expression}. All that is @emph{not}
described by a given bracket expression. The symbol @samp{^} precedes
the negated bracket expression. E.g.: @samp{[^[:digit:]]}
designates whatever character is not a digit. @samp{[^bad]}
designates whatever character is not one of the letters @samp{b}, @samp{a},
or @samp{d}.
See ``Bracket Expression.''
@item Compound Statement
A series of @command{awk} statements, enclosed in curly braces. Compound
statements may be nested.
(@xref{Statements}.)
@item Computed Regexps
See ``Dynamic Regular Expressions.''
@item Concatenation
Concatenating two strings means sticking them together, one after another,
producing a new string. For example, the string @samp{foo} concatenated with
the string @samp{bar} gives the string @samp{foobar}.
(@xref{Concatenation}.)
@item Conditional Expression
An expression using the @samp{?:} ternary operator, such as
@samp{@var{expr1} ? @var{expr2} : @var{expr3}}. The expression
@var{expr1} is evaluated; if the result is true, the value of the whole
expression is the value of @var{expr2}; otherwise the value is
@var{expr3}. In either case, only one of @var{expr2} and @var{expr3}
is evaluated. (@xref{Conditional Exp}.)
@item Control Statement
A control statement is an instruction to perform a given operation or a set
of operations inside an @command{awk} program, if a given condition is
true. Control statements are: @code{if}, @code{for}, @code{while}, and
@code{do}
(@pxref{Statements}).
@cindex McIlroy, Doug
@cindex cookie
@item Cookie
A peculiar goodie, token, saying or remembrance
produced by or presented to a program. (With thanks to Professor Doug McIlroy.)
@ignore
From: Doug McIlroy <doug@cs.dartmouth.edu>
Date: Sat, 13 Oct 2012 19:55:25 -0400
To: arnold@skeeve.com
Subject: Re: origin of the term "cookie"?
I believe the term "cookie", for a more or less inscrutable
saying or crumb of information, was injected into Unix
jargon by Bob Morris, who used the word quite frequently.
It had no fixed meaning as it now does in browsers.
The word had been around long before it was recognized in
the 8th edition glossary (earlier editions had no glossary):
cookie a peculiar goodie, token, saying or remembrance
returned by or presented to a program. [I would say that
"returned by" would better read "produced by", and assume
responsibility for the inexactitude.]
Doug McIlroy
From: Doug McIlroy <doug@cs.dartmouth.edu>
Date: Sun, 14 Oct 2012 10:08:43 -0400
To: arnold@skeeve.com
Subject: Re: origin of the term "cookie"?
> Can I forward your email to Eric Raymond, for possible addition to the
> Jargon File?
Sure. I might add that I don't know how "cookie" entered Morris's
vocabulary. Certainly "values of beta give rise to dom!" (see google)
was an early, if not the earliest Unix cookie. The fact that it was
found lying around on a model 37 teletype (which had Greek beta in
its type box) suggests that maybe it was seen to be like milk and
cookies laid out for Santa Claus. Morris was wont to make such
connections.
Doug
@end ignore
@item Coprocess
A subordinate program with which two-way communications is possible.
@item Curly Braces
See ``Braces.''
@cindex dark corner
@item Dark Corner
An area in the language where specifications often were (or still
are) not clear, leading to unexpected or undesirable behavior.
Such areas are marked in this @value{DOCUMENT} with
@iftex
the picture of a flashlight in the margin
@end iftex
@ifnottex
``(d.c.)'' in the text
@end ifnottex
and are indexed under the heading ``dark corner.''
@item Data Driven
A description of @command{awk} programs, where you specify the data you
are interested in processing, and what to do when that data is seen.
@item Data Objects
These are numbers and strings of characters. Numbers are converted into
strings and vice versa, as needed.
(@xref{Conversion}.)
@item Deadlock
The situation in which two communicating processes are each waiting
for the other to perform an action.
@item Debugger
A program used to help developers remove ``bugs'' from (de-bug)
their programs.
@item Double Precision
An internal representation of numbers that can have fractional parts.
Double precision numbers keep track of more digits than do single precision
numbers, but operations on them are sometimes more expensive. This is the way
@command{awk} stores numeric values. It is the C type @code{double}.
@item Dynamic Regular Expression
A dynamic regular expression is a regular expression written as an
ordinary expression. It could be a string constant, such as
@code{"foo"}, but it may also be an expression whose value can vary.
(@xref{Computed Regexps}.)
@item Empty String
See ``Null String.''
@item Environment
A collection of strings, of the form @samp{@var{name}=@var{val}}, that each
program has available to it. Users generally place values into the
environment in order to provide information to various programs. Typical
examples are the environment variables @env{HOME} and @env{PATH}.
@cindex epoch, definition of
@item Epoch
The date used as the ``beginning of time'' for timestamps.
Time values in most systems are represented as seconds since the epoch,
with library functions available for converting these values into
standard date and time formats.
The epoch on Unix and POSIX systems is 1970-01-01 00:00:00 UTC.
See also ``GMT'' and ``UTC.''
@item Escape Sequences
@cindex ASCII
A special sequence of characters used for describing nonprinting
characters, such as @samp{\n} for newline or @samp{\033} for the ASCII
ESC (Escape) character. (@xref{Escape Sequences}.)
@item Extension
An additional feature or change to a programming language or
utility not defined by that language's or utility's standard.
@command{gawk} has (too) many extensions over POSIX @command{awk}.
@item FDL
See ``Free Documentation License.''
@item Field
When @command{awk} reads an input record, it splits the record into pieces
separated by whitespace (or by a separator regexp that you can
change by setting the predefined variable @code{FS}). Such pieces are
called fields. If the pieces are of fixed length, you can use the built-in
variable @code{FIELDWIDTHS} to describe their lengths.
If you wish to specify the contents of fields instead of the field
separator, you can use the predefined variable @code{FPAT} to do so.
(@xref{Field Separators},
@ref{Constant Size},
and
@ref{Splitting By Content}.)
@item Flag
A variable whose truth value indicates the existence or nonexistence
of some condition.
@item Floating-Point Number
Often referred to in mathematical terms as a ``rational'' or real number,
this is just a number that can have a fractional part.
See also ``Double Precision'' and ``Single Precision.''
@item Format
Format strings control the appearance of output in the
@code{strftime()} and @code{sprintf()} functions, and in the
@code{printf} statement as well. Also, data conversions from numbers to strings
are controlled by the format strings contained in the predefined variables
@code{CONVFMT} and @code{OFMT}. (@xref{Control Letters}.)
@item Fortran
Shorthand for FORmula TRANslator, one of the first programming languages
available for scientific calculations. It was created by John Backus,
and has been available since 1957. It is still in use today.
@item Free Documentation License
This document describes the terms under which this @value{DOCUMENT}
is published and may be copied. (@xref{GNU Free Documentation License}.)
@cindex FSF (Free Software Foundation)
@cindex Free Software Foundation (FSF)
@cindex Stallman, Richard
@item Free Software Foundation
A nonprofit organization dedicated
to the production and distribution of freely distributable software.
It was founded by Richard M.@: Stallman, the author of the original
Emacs editor. GNU Emacs is the most widely used version of Emacs today.
@item FSF
See ``Free Software Foundation.''
@item Function
A part of an @command{awk} program that can be invoked from every point of
the program, to perform a task. @command{awk} has several built-in
functions.
Users can define their own functions in every part of the program.
Function can be recursive, i.e., they may invoke themselves.
@xref{Functions}.
In @command{gawk} it is also possible to have functions shared
among different programs, and included where required using the
@code{@@include} directive
(@pxref{Include Files}).
In @command{gawk} the name of the function that should be invoked
can be generated at run time, i.e., dynamically.
The @command{gawk} extension API provides constructor functions
(@pxref{Constructor Functions}).
@item @command{gawk}
The GNU implementation of @command{awk}.
@cindex GPL (General Public License)
@item General Public License
This document describes the terms under which @command{gawk} and its source
code may be distributed. (@xref{Copying}.)
@item GMT
``Greenwich Mean Time.''
This is the old term for UTC.
It is the time of day used internally for Unix and POSIX systems.
See also ``Epoch'' and ``UTC.''
@cindex FSF (Free Software Foundation)
@cindex Free Software Foundation (FSF)
@cindex GNU Project
@item GNU
``GNU's not Unix''. An on-going project of the Free Software Foundation
to create a complete, freely distributable, POSIX-compliant computing
environment.
@item GNU/Linux
A variant of the GNU system using the Linux kernel, instead of the
Free Software Foundation's Hurd kernel.
The Linux kernel is a stable, efficient, full-featured clone of Unix that has
been ported to a variety of architectures.
It is most popular on PC-class systems, but runs well on a variety of
other systems too.
The Linux kernel source code is available under the terms of the GNU General
Public License, which is perhaps its most important aspect.
@item GPL
See ``General Public License.''
@item Hexadecimal
Base 16 notation, where the digits are @code{0}--@code{9} and
@code{A}--@code{F}, with @samp{A}
representing 10, @samp{B} representing 11, and so on, up to @samp{F} for 15.
Hexadecimal numbers are written in C using a leading @samp{0x},
@iftex
to indicate their base. Thus, @code{0x12} is 18 (@math{(1\times 16) + 2}).
@end iftex
@ifnottex
to indicate their base. Thus, @code{0x12} is 18 ((1 x 16) + 2).
@end ifnottex
@xref{Nondecimal-numbers}.
@item I/O
Abbreviation for ``Input/Output,'' the act of moving data into and/or
out of a running program.
@item Input Record
A single chunk of data that is read in by @command{awk}. Usually, an @command{awk} input
record consists of one line of text.
(@xref{Records}.)
@item Integer
A whole number, i.e., a number that does not have a fractional part.
@item Internationalization
The process of writing or modifying a program so
that it can use multiple languages without requiring
further source code changes.
@cindex interpreted programs
@item Interpreter
A program that reads human-readable source code directly, and uses
the instructions in it to process data and produce results.
@command{awk} is typically (but not always) implemented as an interpreter.
See also ``Compiler.''
@item Interval Expression
A component of a regular expression that lets you specify repeated matches of
some part of the regexp. Interval expressions were not originally available
in @command{awk} programs.
@cindex ISO
@item ISO
The International Organization for Standardization.
This organization produces international standards for many things, including
programming languages, such as C and C++.
In the computer arena, important standards like those for C, C++, and POSIX
become both American national and ISO international standards simultaneously.
This @value{DOCUMENT} refers to Standard C as ``ISO C'' throughout.
See @uref{https://www.iso.org/iso/home/about.htm, the ISO website} for more
information about the name of the organization and its language-independent
three-letter acronym.
@cindex Java programming language
@cindex programming languages @subentry Java
@item Java
A modern programming language originally developed by Sun Microsystems
(now Oracle) supporting Object-Oriented programming. Although usually
implemented by compiling to the instructions for a standard virtual
machine (the JVM), the language can be compiled to native code.
@item Keyword
In the @command{awk} language, a keyword is a word that has special
meaning. Keywords are reserved and may not be used as variable names.
@command{gawk}'s keywords are:
@code{BEGIN},
@code{BEGINFILE},
@code{END},
@code{ENDFILE},
@code{break},
@code{case},
@code{continue},
@code{default},
@code{delete},
@code{do@dots{}while},
@code{else},
@code{exit},
@code{for@dots{}in},
@code{for},
@code{function},
@code{func},
@code{if},
@code{next},
@code{nextfile},
@code{switch},
and
@code{while}.
@item Korn Shell
The Korn Shell (@command{ksh}) is a Unix shell which was developed by David Korn at Bell
Laboratories in the early 1980s. The Korn Shell is backward-compatible with the Bourne
shell and includes many features of the C shell.
See also ``Bourne Shell.''
@cindex LGPL (Lesser General Public License)
@cindex Lesser General Public License (LGPL)
@cindex GNU Lesser General Public License
@item Lesser General Public License
This document describes the terms under which binary library archives
or shared objects,
and their source code may be distributed.
@item LGPL
See ``Lesser General Public License.''
@item Linux
See ``GNU/Linux.''
@item Localization
The process of providing the data necessary for an
internationalized program to work in a particular language.
@item Logical Expression
An expression using the operators for logic, AND, OR, and NOT, written
@samp{&&}, @samp{||}, and @samp{!} in @command{awk}. Often called Boolean
expressions, after the mathematician who pioneered this kind of
mathematical logic.
@item Lvalue
An expression that can appear on the left side of an assignment
operator. In most languages, lvalues can be variables or array
elements. In @command{awk}, a field designator can also be used as an
lvalue.
@item Matching
The act of testing a string against a regular expression. If the
regexp describes the contents of the string, it is said to @dfn{match} it.
@item Metacharacters
Characters used within a regexp that do not stand for themselves.
Instead, they denote regular expression operations, such as repetition,
grouping, or alternation.
@item Nesting
Nesting is where information is organized in layers, or where objects
contain other similar objects.
In @command{gawk} the @code{@@include}
directive can be nested. The ``natural'' nesting of arithmetic and
logical operations can be changed using parentheses
(@pxref{Precedence}).
@item No-op
An operation that does nothing.
@item Null String
A string with no characters in it. It is represented explicitly in
@command{awk} programs by placing two double quote characters next to
each other (@code{""}). It can appear in input data by having two successive
occurrences of the field separator appear next to each other.
@item Number
A numeric-valued data object. Modern @command{awk} implementations use
double precision floating-point to represent numbers.
Ancient @command{awk} implementations used single precision floating-point.
@item Octal
Base-eight notation, where the digits are @code{0}--@code{7}.
Octal numbers are written in C using a leading @samp{0},
@iftex
to indicate their base. Thus, @code{013} is 11 (@math{(1\times 8) + 3}).
@end iftex
@ifnottex
to indicate their base. Thus, @code{013} is 11 ((1 x 8) + 3).
@end ifnottex
@xref{Nondecimal-numbers}.
@item Output Record
A single chunk of data that is written out by @command{awk}. Usually, an
@command{awk} output record consists of one or more lines of text.
@xref{Records}.
@item Pattern
Patterns tell @command{awk} which input records are interesting to which
rules.
A pattern is an arbitrary conditional expression against which input is
tested. If the condition is satisfied, the pattern is said to @dfn{match}
the input record. A typical pattern might compare the input record against
a regular expression. (@xref{Pattern Overview}.)
@item PEBKAC
An acronym describing what is possibly the most frequent
source of computer usage problems. (Problem Exists Between
Keyboard And Chair.)
@item Plug-in
See ``Extensions.''
@item POSIX
The name for a series of standards
that specify a Portable Operating System interface. The ``IX'' denotes
the Unix heritage of these standards. The main standard of interest for
@command{awk} users is
@cite{IEEE Standard for Information Technology, Standard 1003.1@sup{TM}-2017
(Revision of IEEE Std 1003.1-2008)}.
The 2018 POSIX standard can be found online at
@url{https://pubs.opengroup.org/onlinepubs/9699919799/}.
@item Precedence
The order in which operations are performed when operators are used
without explicit parentheses.
@item Private
Variables and/or functions that are meant for use exclusively by library
functions and not for the main @command{awk} program. Special care must be
taken when naming such variables and functions.
(@xref{Library Names}.)
@item Range (of input lines)
A sequence of consecutive lines from the input file(s). A pattern
can specify ranges of input lines for @command{awk} to process or it can
specify single lines. (@xref{Pattern Overview}.)
@item Record
See ``Input record'' and ``Output record.''
@item Recursion
When a function calls itself, either directly or indirectly.
If this is clear, stop, and proceed to the next entry.
Otherwise, refer to the entry for ``recursion.''
@item Redirection
Redirection means performing input from something other than the standard input
stream, or performing output to something other than the standard output stream.
You can redirect input to the @code{getline} statement using
the @samp{<}, @samp{|}, and @samp{|&} operators.
You can redirect the output of the @code{print} and @code{printf} statements
to a file or a system command, using the @samp{>}, @samp{>>}, @samp{|}, and @samp{|&}
operators.
(@xref{Getline},
and @ref{Redirection}.)
@item Reference Counts
An internal mechanism in @command{gawk} to minimize the amount of memory
needed to store the value of string variables. If the value assumed by
a variable is used in more than one place, only one copy of the value
itself is kept, and the associated reference count is increased when the
same value is used by an additional variable, and decreased when the related
variable is no longer in use. When the reference count goes to zero,
the memory space used to store the value of the variable is freed.
@item Regexp
See ``Regular Expression.''
@item Regular Expression
A regular expression (``regexp'' for short) is a pattern that denotes a
set of strings, possibly an infinite set. For example, the regular expression
@samp{R.*xp} matches any string starting with the letter @samp{R}
and ending with the letters @samp{xp}. In @command{awk}, regular expressions are
used in patterns and in conditional expressions. Regular expressions may contain
escape sequences. (@xref{Regexp}.)
@item Regular Expression Constant
A regular expression constant is a regular expression written within
slashes, such as @code{/foo/}. This regular expression is chosen
when you write the @command{awk} program and cannot be changed during
its execution. (@xref{Regexp Usage}.)
@item Regular Expression Operators
See ``Metacharacters.''
@item Rounding
Rounding the result of an arithmetic operation can be tricky.
More than one way of rounding exists, and in @command{gawk}
it is possible to choose which method should be used in a program.
@xref{Setting the rounding mode}.
@item Rule
A segment of an @command{awk} program that specifies how to process single
input records. A rule consists of a @dfn{pattern} and an @dfn{action}.
@command{awk} reads an input record; then, for each rule, if the input record
satisfies the rule's pattern, @command{awk} executes the rule's action.
Otherwise, the rule does nothing for that input record.
@item Rvalue
A value that can appear on the right side of an assignment operator.
In @command{awk}, essentially every expression has a value. These values
are rvalues.
@item Scalar
A single value, be it a number or a string.
Regular variables are scalars; arrays and functions are not.
@item Search Path
In @command{gawk}, a list of directories to search for @command{awk} program source files.
In the shell, a list of directories to search for executable programs.
@item @command{sed}
See ``Stream Editor.''
@item Seed
The initial value, or starting point, for a sequence of random numbers.
@item Shell
The command interpreter for Unix and POSIX-compliant systems.
The shell works both interactively, and as a programming language
for batch files, or shell scripts.
@item Short-Circuit
The nature of the @command{awk} logical operators @samp{&&} and @samp{||}.
If the value of the entire expression is determinable from evaluating just
the lefthand side of these operators, the righthand side is not
evaluated.
(@xref{Boolean Ops}.)
@item Side Effect
A side effect occurs when an expression has an effect aside from merely
producing a value. Assignment expressions, increment and decrement
expressions, and function calls have side effects.
(@xref{Assignment Ops}.)
@item Single Precision
An internal representation of numbers that can have fractional parts.
Single precision numbers keep track of fewer digits than do double precision
numbers, but operations on them are sometimes less expensive in terms of CPU time.
This is the type used by some ancient versions of @command{awk} to store
numeric values. It is the C type @code{float}.
@item Space
The character generated by hitting the space bar on the keyboard.
@item Special File
A @value{FN} interpreted internally by @command{gawk}, instead of being handed
directly to the underlying operating system---for example, @file{/dev/stderr}.
(@xref{Special Files}.)
@item Statement
An expression inside an @command{awk} program in the action part
of a pattern--action rule, or inside an
@command{awk} function. A statement can be a variable assignment,
an array operation, a loop, etc.
@item Stream Editor
A program that reads records from an input stream and processes them one
or more at a time. This is in contrast with batch programs, which may
expect to read their input files in entirety before starting to do
anything, as well as with interactive programs which require input from the
user.
@item String
A datum consisting of a sequence of characters, such as @samp{I am a
string}. Constant strings are written with double quotes in the
@command{awk} language and may contain escape sequences.
(@xref{Escape Sequences}.)
@item Tab
The character generated by hitting the @kbd{TAB} key on the keyboard.
It usually expands to up to eight spaces upon output.
@item Text Domain
A unique name that identifies an application.
Used for grouping messages that are translated at runtime
into the local language.
@item Timestamp
A value in the ``seconds since the epoch'' format used by Unix
and POSIX systems. Used for the @command{gawk} functions
@code{mktime()}, @code{strftime()}, and @code{systime()}.
See also ``Epoch,'' ``GMT,'' and ``UTC.''
@cindex GNU/Linux
@cindex Unix
@cindex BSD-based operating systems
@cindex NetBSD
@cindex FreeBSD
@cindex OpenBSD
@item Unix
A computer operating system originally developed in the early 1970's at
AT&T Bell Laboratories. It initially became popular in universities around
the world and later moved into commercial environments as a software
development system and network server system. There are many commercial
versions of Unix, as well as several work-alike systems whose source code
is freely available (such as GNU/Linux, @uref{http://www.netbsd.org, NetBSD},
@uref{https://www.freebsd.org, FreeBSD}, and @uref{http://www.openbsd.org, OpenBSD}).
@item UTC
The accepted abbreviation for ``Universal Coordinated Time.''
This is standard time in Greenwich, England, which is used as a
reference time for day and date calculations.
See also ``Epoch'' and ``GMT.''
@item Variable
A name for a value. In @command{awk}, variables may be either scalars
or arrays.
@item Whitespace
A sequence of space, TAB, or newline characters occurring inside an input
record or a string.
@end table
@end ifclear
@c The GNU General Public License.
@node Copying
@unnumbered GNU General Public License
@ifnotdocbook
@center Version 3, 29 June 2007
@end ifnotdocbook
@docbook
<subtitle>Version 3, 29 June 2007</subtitle>
@end docbook
@c This file is intended to be included within another document,
@c hence no sectioning command or @node.
@display
Copyright @copyright{} 2007 Free Software Foundation, Inc. @url{https://fsf.org/}
Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.
@end display
@c fakenode --- for prepinfo
@heading Preamble
The GNU General Public License is a free, copyleft license for
software and other kinds of works.
The licenses for most software and other practical works are designed
to take away your freedom to share and change the works. By contrast,
the GNU General Public License is intended to guarantee your freedom
to share and change all versions of a program---to make sure it remains
free software for all its users. We, the Free Software Foundation,
use the GNU General Public License for most of our software; it
applies also to any other work released this way by its authors. You
can apply it to your programs, too.
When we speak of free software, we are referring to freedom, not
price. Our General Public Licenses are designed to make sure that you
have the freedom to distribute copies of free software (and charge for
them if you wish), that you receive source code or can get it if you
want it, that you can change the software or use pieces of it in new
free programs, and that you know you can do these things.
To protect your rights, we need to prevent others from denying you
these rights or asking you to surrender the rights. Therefore, you
have certain responsibilities if you distribute copies of the
software, or if you modify it: responsibilities to respect the freedom
of others.
For example, if you distribute copies of such a program, whether
gratis or for a fee, you must pass on to the recipients the same
freedoms that you received. You must make sure that they, too,
receive or can get the source code. And you must show them these
terms so they know their rights.
Developers that use the GNU GPL protect your rights with two steps:
(1) assert copyright on the software, and (2) offer you this License
giving you legal permission to copy, distribute and/or modify it.
For the developers' and authors' protection, the GPL clearly explains
that there is no warranty for this free software. For both users' and
authors' sake, the GPL requires that modified versions be marked as
changed, so that their problems will not be attributed erroneously to
authors of previous versions.
Some devices are designed to deny users access to install or run
modified versions of the software inside them, although the
manufacturer can do so. This is fundamentally incompatible with the
aim of protecting users' freedom to change the software. The
systematic pattern of such abuse occurs in the area of products for
individuals to use, which is precisely where it is most unacceptable.
Therefore, we have designed this version of the GPL to prohibit the
practice for those products. If such problems arise substantially in
other domains, we stand ready to extend this provision to those
domains in future versions of the GPL, as needed to protect the
freedom of users.
Finally, every program is threatened constantly by software patents.
States should not allow patents to restrict development and use of
software on general-purpose computers, but in those that do, we wish
to avoid the special danger that patents applied to a free program
could make it effectively proprietary. To prevent this, the GPL
assures that patents cannot be used to render the program non-free.
The precise terms and conditions for copying, distribution and
modification follow.
@c fakenode --- for prepinfo
@heading TERMS AND CONDITIONS
@enumerate 0
@item Definitions.
``This License'' refers to version 3 of the GNU General Public License.
``Copyright'' also means copyright-like laws that apply to other kinds
of works, such as semiconductor masks.
``The Program'' refers to any copyrightable work licensed under this
License. Each licensee is addressed as ``you''. ``Licensees'' and
``recipients'' may be individuals or organizations.
To ``modify'' a work means to copy from or adapt all or part of the work
in a fashion requiring copyright permission, other than the making of
an exact copy. The resulting work is called a ``modified version'' of
the earlier work or a work ``based on'' the earlier work.
A ``covered work'' means either the unmodified Program or a work based
on the Program.
To ``propagate'' a work means to do anything with it that, without
permission, would make you directly or secondarily liable for
infringement under applicable copyright law, except executing it on a
computer or modifying a private copy. Propagation includes copying,
distribution (with or without modification), making available to the
public, and in some countries other activities as well.
To ``convey'' a work means any kind of propagation that enables other
parties to make or receive copies. Mere interaction with a user
through a computer network, with no transfer of a copy, is not
conveying.
An interactive user interface displays ``Appropriate Legal Notices'' to
the extent that it includes a convenient and prominently visible
feature that (1) displays an appropriate copyright notice, and (2)
tells the user that there is no warranty for the work (except to the
extent that warranties are provided), that licensees may convey the
work under this License, and how to view a copy of this License. If
the interface presents a list of user commands or options, such as a
menu, a prominent item in the list meets this criterion.
@item Source Code.
The ``source code'' for a work means the preferred form of the work for
making modifications to it. ``Object code'' means any non-source form
of a work.
A ``Standard Interface'' means an interface that either is an official
standard defined by a recognized standards body, or, in the case of
interfaces specified for a particular programming language, one that
is widely used among developers working in that language.
The ``System Libraries'' of an executable work include anything, other
than the work as a whole, that (a) is included in the normal form of
packaging a Major Component, but which is not part of that Major
Component, and (b) serves only to enable use of the work with that
Major Component, or to implement a Standard Interface for which an
implementation is available to the public in source code form. A
``Major Component'', in this context, means a major essential component
(kernel, window system, and so on) of the specific operating system
(if any) on which the executable work runs, or a compiler used to
produce the work, or an object code interpreter used to run it.
The ``Corresponding Source'' for a work in object code form means all
the source code needed to generate, install, and (for an executable
work) run the object code and to modify the work, including scripts to
control those activities. However, it does not include the work's
System Libraries, or general-purpose tools or generally available free
programs which are used unmodified in performing those activities but
which are not part of the work. For example, Corresponding Source
includes interface definition files associated with source files for
the work, and the source code for shared libraries and dynamically
linked subprograms that the work is specifically designed to require,
such as by intimate data communication or control flow between those
subprograms and other parts of the work.
The Corresponding Source need not include anything that users can
regenerate automatically from other parts of the Corresponding Source.
The Corresponding Source for a work in source code form is that same
work.
@item Basic Permissions.
All rights granted under this License are granted for the term of
copyright on the Program, and are irrevocable provided the stated
conditions are met. This License explicitly affirms your unlimited
permission to run the unmodified Program. The output from running a
covered work is covered by this License only if the output, given its
content, constitutes a covered work. This License acknowledges your
rights of fair use or other equivalent, as provided by copyright law.
You may make, run and propagate covered works that you do not convey,
without conditions so long as your license otherwise remains in force.
You may convey covered works to others for the sole purpose of having
them make modifications exclusively for you, or provide you with
facilities for running those works, provided that you comply with the
terms of this License in conveying all material for which you do not
control copyright. Those thus making or running the covered works for
you must do so exclusively on your behalf, under your direction and
control, on terms that prohibit them from making any copies of your
copyrighted material outside their relationship with you.
Conveying under any other circumstances is permitted solely under the
conditions stated below. Sublicensing is not allowed; section 10
makes it unnecessary.
@item Protecting Users' Legal Rights From Anti-Circumvention Law.
No covered work shall be deemed part of an effective technological
measure under any applicable law fulfilling obligations under article
11 of the WIPO copyright treaty adopted on 20 December 1996, or
similar laws prohibiting or restricting circumvention of such
measures.
When you convey a covered work, you waive any legal power to forbid
circumvention of technological measures to the extent such
circumvention is effected by exercising rights under this License with
respect to the covered work, and you disclaim any intention to limit
operation or modification of the work as a means of enforcing, against
the work's users, your or third parties' legal rights to forbid
circumvention of technological measures.
@item Conveying Verbatim Copies.
You may convey verbatim copies of the Program's source code as you
receive it, in any medium, provided that you conspicuously and
appropriately publish on each copy an appropriate copyright notice;
keep intact all notices stating that this License and any
non-permissive terms added in accord with section 7 apply to the code;
keep intact all notices of the absence of any warranty; and give all
recipients a copy of this License along with the Program.
You may charge any price or no price for each copy that you convey,
and you may offer support or warranty protection for a fee.
@item Conveying Modified Source Versions.
You may convey a work based on the Program, or the modifications to
produce it from the Program, in the form of source code under the
terms of section 4, provided that you also meet all of these
conditions:
@enumerate a
@item
The work must carry prominent notices stating that you modified it,
and giving a relevant date.
@item
The work must carry prominent notices stating that it is released
under this License and any conditions added under section 7. This
requirement modifies the requirement in section 4 to ``keep intact all
notices''.
@item
You must license the entire work, as a whole, under this License to
anyone who comes into possession of a copy. This License will
therefore apply, along with any applicable section 7 additional terms,
to the whole of the work, and all its parts, regardless of how they
are packaged. This License gives no permission to license the work in
any other way, but it does not invalidate such permission if you have
separately received it.
@item
If the work has interactive user interfaces, each must display
Appropriate Legal Notices; however, if the Program has interactive
interfaces that do not display Appropriate Legal Notices, your work
need not make them do so.
@end enumerate
A compilation of a covered work with other separate and independent
works, which are not by their nature extensions of the covered work,
and which are not combined with it such as to form a larger program,
in or on a volume of a storage or distribution medium, is called an
``aggregate'' if the compilation and its resulting copyright are not
used to limit the access or legal rights of the compilation's users
beyond what the individual works permit. Inclusion of a covered work
in an aggregate does not cause this License to apply to the other
parts of the aggregate.
@item Conveying Non-Source Forms.
You may convey a covered work in object code form under the terms of
sections 4 and 5, provided that you also convey the machine-readable
Corresponding Source under the terms of this License, in one of these
ways:
@enumerate a
@item
Convey the object code in, or embodied in, a physical product
(including a physical distribution medium), accompanied by the
Corresponding Source fixed on a durable physical medium customarily
used for software interchange.
@item
Convey the object code in, or embodied in, a physical product
(including a physical distribution medium), accompanied by a written
offer, valid for at least three years and valid for as long as you
offer spare parts or customer support for that product model, to give
anyone who possesses the object code either (1) a copy of the
Corresponding Source for all the software in the product that is
covered by this License, on a durable physical medium customarily used
for software interchange, for a price no more than your reasonable
cost of physically performing this conveying of source, or (2) access
to copy the Corresponding Source from a network server at no charge.
@item
Convey individual copies of the object code with a copy of the written
offer to provide the Corresponding Source. This alternative is
allowed only occasionally and noncommercially, and only if you
received the object code with such an offer, in accord with subsection
6b.
@item
Convey the object code by offering access from a designated place
(gratis or for a charge), and offer equivalent access to the
Corresponding Source in the same way through the same place at no
further charge. You need not require recipients to copy the
Corresponding Source along with the object code. If the place to copy
the object code is a network server, the Corresponding Source may be
on a different server (operated by you or a third party) that supports
equivalent copying facilities, provided you maintain clear directions
next to the object code saying where to find the Corresponding Source.
Regardless of what server hosts the Corresponding Source, you remain
obligated to ensure that it is available for as long as needed to
satisfy these requirements.
@item
Convey the object code using peer-to-peer transmission, provided you
inform other peers where the object code and Corresponding Source of
the work are being offered to the general public at no charge under
subsection 6d.
@end enumerate
A separable portion of the object code, whose source code is excluded
from the Corresponding Source as a System Library, need not be
included in conveying the object code work.
A ``User Product'' is either (1) a ``consumer product'', which means any
tangible personal property which is normally used for personal,
family, or household purposes, or (2) anything designed or sold for
incorporation into a dwelling. In determining whether a product is a
consumer product, doubtful cases shall be resolved in favor of
coverage. For a particular product received by a particular user,
``normally used'' refers to a typical or common use of that class of
product, regardless of the status of the particular user or of the way
in which the particular user actually uses, or expects or is expected
to use, the product. A product is a consumer product regardless of
whether the product has substantial commercial, industrial or
non-consumer uses, unless such uses represent the only significant
mode of use of the product.
``Installation Information'' for a User Product means any methods,
procedures, authorization keys, or other information required to
install and execute modified versions of a covered work in that User
Product from a modified version of its Corresponding Source. The
information must suffice to ensure that the continued functioning of
the modified object code is in no case prevented or interfered with
solely because modification has been made.
If you convey an object code work under this section in, or with, or
specifically for use in, a User Product, and the conveying occurs as
part of a transaction in which the right of possession and use of the
User Product is transferred to the recipient in perpetuity or for a
fixed term (regardless of how the transaction is characterized), the
Corresponding Source conveyed under this section must be accompanied
by the Installation Information. But this requirement does not apply
if neither you nor any third party retains the ability to install
modified object code on the User Product (for example, the work has
been installed in ROM).
The requirement to provide Installation Information does not include a
requirement to continue to provide support service, warranty, or
updates for a work that has been modified or installed by the
recipient, or for the User Product in which it has been modified or
installed. Access to a network may be denied when the modification
itself materially and adversely affects the operation of the network
or violates the rules and protocols for communication across the
network.
Corresponding Source conveyed, and Installation Information provided,
in accord with this section must be in a format that is publicly
documented (and with an implementation available to the public in
source code form), and must require no special password or key for
unpacking, reading or copying.
@item Additional Terms.
``Additional permissions'' are terms that supplement the terms of this
License by making exceptions from one or more of its conditions.
Additional permissions that are applicable to the entire Program shall
be treated as though they were included in this License, to the extent
that they are valid under applicable law. If additional permissions
apply only to part of the Program, that part may be used separately
under those permissions, but the entire Program remains governed by
this License without regard to the additional permissions.
When you convey a copy of a covered work, you may at your option
remove any additional permissions from that copy, or from any part of
it. (Additional permissions may be written to require their own
removal in certain cases when you modify the work.) You may place
additional permissions on material, added by you to a covered work,
for which you have or can give appropriate copyright permission.
Notwithstanding any other provision of this License, for material you
add to a covered work, you may (if authorized by the copyright holders
of that material) supplement the terms of this License with terms:
@enumerate a
@item
Disclaiming warranty or limiting liability differently from the terms
of sections 15 and 16 of this License; or
@item
Requiring preservation of specified reasonable legal notices or author
attributions in that material or in the Appropriate Legal Notices
displayed by works containing it; or
@item
Prohibiting misrepresentation of the origin of that material, or
requiring that modified versions of such material be marked in
reasonable ways as different from the original version; or
@item
Limiting the use for publicity purposes of names of licensors or
authors of the material; or
@item
Declining to grant rights under trademark law for use of some trade
names, trademarks, or service marks; or
@item
Requiring indemnification of licensors and authors of that material by
anyone who conveys the material (or modified versions of it) with
contractual assumptions of liability to the recipient, for any
liability that these contractual assumptions directly impose on those
licensors and authors.
@end enumerate
All other non-permissive additional terms are considered ``further
restrictions'' within the meaning of section 10. If the Program as you
received it, or any part of it, contains a notice stating that it is
governed by this License along with a term that is a further
restriction, you may remove that term. If a license document contains
a further restriction but permits relicensing or conveying under this
License, you may add to a covered work material governed by the terms
of that license document, provided that the further restriction does
not survive such relicensing or conveying.
If you add terms to a covered work in accord with this section, you
must place, in the relevant source files, a statement of the
additional terms that apply to those files, or a notice indicating
where to find the applicable terms.
Additional terms, permissive or non-permissive, may be stated in the
form of a separately written license, or stated as exceptions; the
above requirements apply either way.
@item Termination.
You may not propagate or modify a covered work except as expressly
provided under this License. Any attempt otherwise to propagate or
modify it is void, and will automatically terminate your rights under
this License (including any patent licenses granted under the third
paragraph of section 11).
However, if you cease all violation of this License, then your license
from a particular copyright holder is reinstated (a) provisionally,
unless and until the copyright holder explicitly and finally
terminates your license, and (b) permanently, if the copyright holder
fails to notify you of the violation by some reasonable means prior to
60 days after the cessation.
Moreover, your license from a particular copyright holder is
reinstated permanently if the copyright holder notifies you of the
violation by some reasonable means, this is the first time you have
received notice of violation of this License (for any work) from that
copyright holder, and you cure the violation prior to 30 days after
your receipt of the notice.
Termination of your rights under this section does not terminate the
licenses of parties who have received copies or rights from you under
this License. If your rights have been terminated and not permanently
reinstated, you do not qualify to receive new licenses for the same
material under section 10.
@item Acceptance Not Required for Having Copies.
You are not required to accept this License in order to receive or run
a copy of the Program. Ancillary propagation of a covered work
occurring solely as a consequence of using peer-to-peer transmission
to receive a copy likewise does not require acceptance. However,
nothing other than this License grants you permission to propagate or
modify any covered work. These actions infringe copyright if you do
not accept this License. Therefore, by modifying or propagating a
covered work, you indicate your acceptance of this License to do so.
@item Automatic Licensing of Downstream Recipients.
Each time you convey a covered work, the recipient automatically
receives a license from the original licensors, to run, modify and
propagate that work, subject to this License. You are not responsible
for enforcing compliance by third parties with this License.
An ``entity transaction'' is a transaction transferring control of an
organization, or substantially all assets of one, or subdividing an
organization, or merging organizations. If propagation of a covered
work results from an entity transaction, each party to that
transaction who receives a copy of the work also receives whatever
licenses to the work the party's predecessor in interest had or could
give under the previous paragraph, plus a right to possession of the
Corresponding Source of the work from the predecessor in interest, if
the predecessor has it or can get it with reasonable efforts.
You may not impose any further restrictions on the exercise of the
rights granted or affirmed under this License. For example, you may
not impose a license fee, royalty, or other charge for exercise of
rights granted under this License, and you may not initiate litigation
(including a cross-claim or counterclaim in a lawsuit) alleging that
any patent claim is infringed by making, using, selling, offering for
sale, or importing the Program or any portion of it.
@item Patents.
A ``contributor'' is a copyright holder who authorizes use under this
License of the Program or a work on which the Program is based. The
work thus licensed is called the contributor's ``contributor version''.
A contributor's ``essential patent claims'' are all patent claims owned
or controlled by the contributor, whether already acquired or
hereafter acquired, that would be infringed by some manner, permitted
by this License, of making, using, or selling its contributor version,
but do not include claims that would be infringed only as a
consequence of further modification of the contributor version. For
purposes of this definition, ``control'' includes the right to grant
patent sublicenses in a manner consistent with the requirements of
this License.
Each contributor grants you a non-exclusive, worldwide, royalty-free
patent license under the contributor's essential patent claims, to
make, use, sell, offer for sale, import and otherwise run, modify and
propagate the contents of its contributor version.
In the following three paragraphs, a ``patent license'' is any express
agreement or commitment, however denominated, not to enforce a patent
(such as an express permission to practice a patent or covenant not to
sue for patent infringement). To ``grant'' such a patent license to a
party means to make such an agreement or commitment not to enforce a
patent against the party.
If you convey a covered work, knowingly relying on a patent license,
and the Corresponding Source of the work is not available for anyone
to copy, free of charge and under the terms of this License, through a
publicly available network server or other readily accessible means,
then you must either (1) cause the Corresponding Source to be so
available, or (2) arrange to deprive yourself of the benefit of the
patent license for this particular work, or (3) arrange, in a manner
consistent with the requirements of this License, to extend the patent
license to downstream recipients. ``Knowingly relying'' means you have
actual knowledge that, but for the patent license, your conveying the
covered work in a country, or your recipient's use of the covered work
in a country, would infringe one or more identifiable patents in that
country that you have reason to believe are valid.
If, pursuant to or in connection with a single transaction or
arrangement, you convey, or propagate by procuring conveyance of, a
covered work, and grant a patent license to some of the parties
receiving the covered work authorizing them to use, propagate, modify
or convey a specific copy of the covered work, then the patent license
you grant is automatically extended to all recipients of the covered
work and works based on it.
A patent license is ``discriminatory'' if it does not include within the
scope of its coverage, prohibits the exercise of, or is conditioned on
the non-exercise of one or more of the rights that are specifically
granted under this License. You may not convey a covered work if you
are a party to an arrangement with a third party that is in the
business of distributing software, under which you make payment to the
third party based on the extent of your activity of conveying the
work, and under which the third party grants, to any of the parties
who would receive the covered work from you, a discriminatory patent
license (a) in connection with copies of the covered work conveyed by
you (or copies made from those copies), or (b) primarily for and in
connection with specific products or compilations that contain the
covered work, unless you entered into that arrangement, or that patent
license was granted, prior to 28 March 2007.
Nothing in this License shall be construed as excluding or limiting
any implied license or other defenses to infringement that may
otherwise be available to you under applicable patent law.
@item No Surrender of Others' Freedom.
If conditions are imposed on you (whether by court order, agreement or
otherwise) that contradict the conditions of this License, they do not
excuse you from the conditions of this License. If you cannot convey
a covered work so as to satisfy simultaneously your obligations under
this License and any other pertinent obligations, then as a
consequence you may not convey it at all. For example, if you agree
to terms that obligate you to collect a royalty for further conveying
from those to whom you convey the Program, the only way you could
satisfy both those terms and this License would be to refrain entirely
from conveying the Program.
@item Use with the GNU Affero General Public License.
Notwithstanding any other provision of this License, you have
permission to link or combine any covered work with a work licensed
under version 3 of the GNU Affero General Public License into a single
combined work, and to convey the resulting work. The terms of this
License will continue to apply to the part which is the covered work,
but the special requirements of the GNU Affero General Public License,
section 13, concerning interaction through a network will apply to the
combination as such.
@item Revised Versions of this License.
The Free Software Foundation may publish revised and/or new versions
of the GNU General Public License from time to time. Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns.
Each version is given a distinguishing version number. If the Program
specifies that a certain numbered version of the GNU General Public
License ``or any later version'' applies to it, you have the option of
following the terms and conditions either of that numbered version or
of any later version published by the Free Software Foundation. If
the Program does not specify a version number of the GNU General
Public License, you may choose any version ever published by the Free
Software Foundation.
If the Program specifies that a proxy can decide which future versions
of the GNU General Public License can be used, that proxy's public
statement of acceptance of a version permanently authorizes you to
choose that version for the Program.
Later license versions may give you additional or different
permissions. However, no additional obligations are imposed on any
author or copyright holder as a result of your choosing to follow a
later version.
@item Disclaimer of Warranty.
THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM ``AS IS'' WITHOUT
WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND
PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE
DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR
CORRECTION.
@item Limitation of Liability.
IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR
CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES
ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT
NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR
LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM
TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER
PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
@item Interpretation of Sections 15 and 16.
If the disclaimer of warranty and limitation of liability provided
above cannot be given local legal effect according to their terms,
reviewing courts shall apply local law that most closely approximates
an absolute waiver of all civil liability in connection with the
Program, unless a warranty or assumption of liability accompanies a
copy of the Program in return for a fee.
@end enumerate
@c fakenode --- for prepinfo
@heading END OF TERMS AND CONDITIONS
@c fakenode --- for prepinfo
@heading How to Apply These Terms to Your New Programs
If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these
terms.
To do so, attach the following notices to the program. It is safest
to attach them to the start of each source file to most effectively
state the exclusion of warranty; and each file should have at least
the ``copyright'' line and a pointer to where the full notice is found.
@smallexample
@var{one line to give the program's name and a brief idea of what it does.}
Copyright (C) @var{year} @var{name of author}
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at
your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see @url{https://www.gnu.org/licenses/}.
@end smallexample
Also add information on how to contact you by electronic and paper mail.
If the program does terminal interaction, make it output a short
notice like this when it starts in an interactive mode:
@smallexample
@var{program} Copyright (C) @var{year} @var{name of author}
This program comes with ABSOLUTELY NO WARRANTY; for details type @samp{show w}.
This is free software, and you are welcome to redistribute it
under certain conditions; type @samp{show c} for details.
@end smallexample
The hypothetical commands @samp{show w} and @samp{show c} should show
the appropriate parts of the General Public License. Of course, your
program's commands might be different; for a GUI interface, you would
use an ``about box''.
You should also get your employer (if you work as a programmer) or school,
if any, to sign a ``copyright disclaimer'' for the program, if necessary.
For more information on this, and how to apply and follow the GNU GPL, see
@url{https://www.gnu.org/licenses/}.
The GNU General Public License does not permit incorporating your
program into proprietary programs. If your program is a subroutine
library, you may consider it more useful to permit linking proprietary
applications with the library. If this is what you want to do, use
the GNU Lesser General Public License instead of this License. But
first, please read @url{https://www.gnu.org/philosophy/why-not-lgpl.html}.
@ifclear FOR_PRINT
@c The GNU Free Documentation License.
@node GNU Free Documentation License
@unnumbered GNU Free Documentation License
@ifnotdocbook
@center Version 1.3, 3 November 2008
@end ifnotdocbook
@docbook
<subtitle>Version 1.3, 3 November 2008</subtitle>
@end docbook
@cindex FDL (Free Documentation License)
@cindex Free Documentation License (FDL)
@cindex GNU Free Documentation License
@c This file is intended to be included within another document,
@c hence no sectioning command or @node.
@display
Copyright @copyright{} 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
@uref{https://fsf.org/}
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
@end display
@enumerate 0
@item
PREAMBLE
The purpose of this License is to make a manual, textbook, or other
functional and useful document @dfn{free} in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it,
with or without modifying it, either commercially or noncommercially.
Secondarily, this License preserves for the author and publisher a way
to get credit for their work, while not being considered responsible
for modifications made by others.
This License is a kind of ``copyleft'', which means that derivative
works of the document must themselves be free in the same sense. It
complements the GNU General Public License, which is a copyleft
license designed for free software.
We have designed this License in order to use it for manuals for free
software, because free software needs free documentation: a free
program should come with manuals providing the same freedoms that the
software does. But this License is not limited to software manuals;
it can be used for any textual work, regardless of subject matter or
whether it is published as a printed book. We recommend this License
principally for works whose purpose is instruction or reference.
@item
APPLICABILITY AND DEFINITIONS
This License applies to any manual or other work, in any medium, that
contains a notice placed by the copyright holder saying it can be
distributed under the terms of this License. Such a notice grants a
world-wide, royalty-free license, unlimited in duration, to use that
work under the conditions stated herein. The ``Document'', below,
refers to any such manual or work. Any member of the public is a
licensee, and is addressed as ``you''. You accept the license if you
copy, modify or distribute the work in a way requiring permission
under copyright law.
A ``Modified Version'' of the Document means any work containing the
Document or a portion of it, either copied verbatim, or with
modifications and/or translated into another language.
A ``Secondary Section'' is a named appendix or a front-matter section
of the Document that deals exclusively with the relationship of the
publishers or authors of the Document to the Document's overall
subject (or to related matters) and contains nothing that could fall
directly within that overall subject. (Thus, if the Document is in
part a textbook of mathematics, a Secondary Section may not explain
any mathematics.) The relationship could be a matter of historical
connection with the subject or with related matters, or of legal,
commercial, philosophical, ethical or political position regarding
them.
The ``Invariant Sections'' are certain Secondary Sections whose titles
are designated, as being those of Invariant Sections, in the notice
that says that the Document is released under this License. If a
section does not fit the above definition of Secondary then it is not
allowed to be designated as Invariant. The Document may contain zero
Invariant Sections. If the Document does not identify any Invariant
Sections then there are none.
The ``Cover Texts'' are certain short passages of text that are listed,
as Front-Cover Texts or Back-Cover Texts, in the notice that says that
the Document is released under this License. A Front-Cover Text may
be at most 5 words, and a Back-Cover Text may be at most 25 words.
A ``Transparent'' copy of the Document means a machine-readable copy,
represented in a format whose specification is available to the
general public, that is suitable for revising the document
straightforwardly with generic text editors or (for images composed of
pixels) generic paint programs or (for drawings) some widely available
drawing editor, and that is suitable for input to text formatters or
for automatic translation to a variety of formats suitable for input
to text formatters. A copy made in an otherwise Transparent file
format whose markup, or absence of markup, has been arranged to thwart
or discourage subsequent modification by readers is not Transparent.
An image format is not Transparent if used for any substantial amount
of text. A copy that is not ``Transparent'' is called ``Opaque''.
Examples of suitable formats for Transparent copies include plain
@sc{ascii} without markup, Texinfo input format, La@TeX{} input
format, @acronym{SGML} or @acronym{XML} using a publicly available
@acronym{DTD}, and standard-conforming simple @acronym{HTML},
PostScript or @acronym{PDF} designed for human modification. Examples
of transparent image formats include @acronym{PNG}, @acronym{XCF} and
@acronym{JPG}. Opaque formats include proprietary formats that can be
read and edited only by proprietary word processors, @acronym{SGML} or
@acronym{XML} for which the @acronym{DTD} and/or processing tools are
not generally available, and the machine-generated @acronym{HTML},
PostScript or @acronym{PDF} produced by some word processors for
output purposes only.
The ``Title Page'' means, for a printed book, the title page itself,
plus such following pages as are needed to hold, legibly, the material
this License requires to appear in the title page. For works in
formats which do not have any title page as such, ``Title Page'' means
the text near the most prominent appearance of the work's title,
preceding the beginning of the body of the text.
The ``publisher'' means any person or entity that distributes copies
of the Document to the public.
A section ``Entitled XYZ'' means a named subunit of the Document whose
title either is precisely XYZ or contains XYZ in parentheses following
text that translates XYZ in another language. (Here XYZ stands for a
specific section name mentioned below, such as ``Acknowledgements'',
``Dedications'', ``Endorsements'', or ``History''.) To ``Preserve the Title''
of such a section when you modify the Document means that it remains a
section ``Entitled XYZ'' according to this definition.
The Document may include Warranty Disclaimers next to the notice which
states that this License applies to the Document. These Warranty
Disclaimers are considered to be included by reference in this
License, but only as regards disclaiming warranties: any other
implication that these Warranty Disclaimers may have is void and has
no effect on the meaning of this License.
@item
VERBATIM COPYING
You may copy and distribute the Document in any medium, either
commercially or noncommercially, provided that this License, the
copyright notices, and the license notice saying this License applies
to the Document are reproduced in all copies, and that you add no other
conditions whatsoever to those of this License. You may not use
technical measures to obstruct or control the reading or further
copying of the copies you make or distribute. However, you may accept
compensation in exchange for copies. If you distribute a large enough
number of copies you must also follow the conditions in section 3.
You may also lend copies, under the same conditions stated above, and
you may publicly display copies.
@item
COPYING IN QUANTITY
If you publish printed copies (or copies in media that commonly have
printed covers) of the Document, numbering more than 100, and the
Document's license notice requires Cover Texts, you must enclose the
copies in covers that carry, clearly and legibly, all these Cover
Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
the back cover. Both covers must also clearly and legibly identify
you as the publisher of these copies. The front cover must present
the full title with all words of the title equally prominent and
visible. You may add other material on the covers in addition.
Copying with changes limited to the covers, as long as they preserve
the title of the Document and satisfy these conditions, can be treated
as verbatim copying in other respects.
If the required texts for either cover are too voluminous to fit
legibly, you should put the first ones listed (as many as fit
reasonably) on the actual cover, and continue the rest onto adjacent
pages.
If you publish or distribute Opaque copies of the Document numbering
more than 100, you must either include a machine-readable Transparent
copy along with each Opaque copy, or state in or with each Opaque copy
a computer-network location from which the general network-using
public has access to download using public-standard network protocols
a complete Transparent copy of the Document, free of added material.
If you use the latter option, you must take reasonably prudent steps,
when you begin distribution of Opaque copies in quantity, to ensure
that this Transparent copy will remain thus accessible at the stated
location until at least one year after the last time you distribute an
Opaque copy (directly or through your agents or retailers) of that
edition to the public.
It is requested, but not required, that you contact the authors of the
Document well before redistributing any large number of copies, to give
them a chance to provide you with an updated version of the Document.
@item
MODIFICATIONS
You may copy and distribute a Modified Version of the Document under
the conditions of sections 2 and 3 above, provided that you release
the Modified Version under precisely this License, with the Modified
Version filling the role of the Document, thus licensing distribution
and modification of the Modified Version to whoever possesses a copy
of it. In addition, you must do these things in the Modified Version:
@enumerate A
@item
Use in the Title Page (and on the covers, if any) a title distinct
from that of the Document, and from those of previous versions
(which should, if there were any, be listed in the History section
of the Document). You may use the same title as a previous version
if the original publisher of that version gives permission.
@item
List on the Title Page, as authors, one or more persons or entities
responsible for authorship of the modifications in the Modified
Version, together with at least five of the principal authors of the
Document (all of its principal authors, if it has fewer than five),
unless they release you from this requirement.
@item
State on the Title page the name of the publisher of the
Modified Version, as the publisher.
@item
Preserve all the copyright notices of the Document.
@item
Add an appropriate copyright notice for your modifications
adjacent to the other copyright notices.
@item
Include, immediately after the copyright notices, a license notice
giving the public permission to use the Modified Version under the
terms of this License, in the form shown in the Addendum below.
@item
Preserve in that license notice the full lists of Invariant Sections
and required Cover Texts given in the Document's license notice.
@item
Include an unaltered copy of this License.
@item
Preserve the section Entitled ``History'', Preserve its Title, and add
to it an item stating at least the title, year, new authors, and
publisher of the Modified Version as given on the Title Page. If
there is no section Entitled ``History'' in the Document, create one
stating the title, year, authors, and publisher of the Document as
given on its Title Page, then add an item describing the Modified
Version as stated in the previous sentence.
@item
Preserve the network location, if any, given in the Document for
public access to a Transparent copy of the Document, and likewise
the network locations given in the Document for previous versions
it was based on. These may be placed in the ``History'' section.
You may omit a network location for a work that was published at
least four years before the Document itself, or if the original
publisher of the version it refers to gives permission.
@item
For any section Entitled ``Acknowledgements'' or ``Dedications'', Preserve
the Title of the section, and preserve in the section all the
substance and tone of each of the contributor acknowledgements and/or
dedications given therein.
@item
Preserve all the Invariant Sections of the Document,
unaltered in their text and in their titles. Section numbers
or the equivalent are not considered part of the section titles.
@item
Delete any section Entitled ``Endorsements''. Such a section
may not be included in the Modified Version.
@item
Do not retitle any existing section to be Entitled ``Endorsements'' or
to conflict in title with any Invariant Section.
@item
Preserve any Warranty Disclaimers.
@end enumerate
If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no material
copied from the Document, you may at your option designate some or all
of these sections as invariant. To do this, add their titles to the
list of Invariant Sections in the Modified Version's license notice.
These titles must be distinct from any other section titles.
You may add a section Entitled ``Endorsements'', provided it contains
nothing but endorsements of your Modified Version by various
parties---for example, statements of peer review or that the text has
been approved by an organization as the authoritative definition of a
standard.
You may add a passage of up to five words as a Front-Cover Text, and a
passage of up to 25 words as a Back-Cover Text, to the end of the list
of Cover Texts in the Modified Version. Only one passage of
Front-Cover Text and one of Back-Cover Text may be added by (or
through arrangements made by) any one entity. If the Document already
includes a cover text for the same cover, previously added by you or
by arrangement made by the same entity you are acting on behalf of,
you may not add another; but you may replace the old one, on explicit
permission from the previous publisher that added the old one.
The author(s) and publisher(s) of the Document do not by this License
give permission to use their names for publicity for or to assert or
imply endorsement of any Modified Version.
@item
COMBINING DOCUMENTS
You may combine the Document with other documents released under this
License, under the terms defined in section 4 above for modified
versions, provided that you include in the combination all of the
Invariant Sections of all of the original documents, unmodified, and
list them all as Invariant Sections of your combined work in its
license notice, and that you preserve all their Warranty Disclaimers.
The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy. If there are multiple Invariant Sections with the same name but
different contents, make the title of each such section unique by
adding at the end of it, in parentheses, the name of the original
author or publisher of that section if known, or else a unique number.
Make the same adjustment to the section titles in the list of
Invariant Sections in the license notice of the combined work.
In the combination, you must combine any sections Entitled ``History''
in the various original documents, forming one section Entitled
``History''; likewise combine any sections Entitled ``Acknowledgements'',
and any sections Entitled ``Dedications''. You must delete all
sections Entitled ``Endorsements.''
@item
COLLECTIONS OF DOCUMENTS
You may make a collection consisting of the Document and other documents
released under this License, and replace the individual copies of this
License in the various documents with a single copy that is included in
the collection, provided that you follow the rules of this License for
verbatim copying of each of the documents in all other respects.
You may extract a single document from such a collection, and distribute
it individually under this License, provided you insert a copy of this
License into the extracted document, and follow this License in all
other respects regarding verbatim copying of that document.
@item
AGGREGATION WITH INDEPENDENT WORKS
A compilation of the Document or its derivatives with other separate
and independent documents or works, in or on a volume of a storage or
distribution medium, is called an ``aggregate'' if the copyright
resulting from the compilation is not used to limit the legal rights
of the compilation's users beyond what the individual works permit.
When the Document is included in an aggregate, this License does not
apply to the other works in the aggregate which are not themselves
derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half of
the entire aggregate, the Document's Cover Texts may be placed on
covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic form.
Otherwise they must appear on printed covers that bracket the whole
aggregate.
@item
TRANSLATION
Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section 4.
Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
translations of some or all Invariant Sections in addition to the
original versions of these Invariant Sections. You may include a
translation of this License, and all the license notices in the
Document, and any Warranty Disclaimers, provided that you also include
the original English version of this License and the original versions
of those notices and disclaimers. In case of a disagreement between
the translation and the original version of this License or a notice
or disclaimer, the original version will prevail.
If a section in the Document is Entitled ``Acknowledgements'',
``Dedications'', or ``History'', the requirement (section 4) to Preserve
its Title (section 1) will typically require changing the actual
title.
@item
TERMINATION
You may not copy, modify, sublicense, or distribute the Document
except as expressly provided under this License. Any attempt
otherwise to copy, modify, sublicense, or distribute it is void, and
will automatically terminate your rights under this License.
However, if you cease all violation of this License, then your license
from a particular copyright holder is reinstated (a) provisionally,
unless and until the copyright holder explicitly and finally
terminates your license, and (b) permanently, if the copyright holder
fails to notify you of the violation by some reasonable means prior to
60 days after the cessation.
Moreover, your license from a particular copyright holder is
reinstated permanently if the copyright holder notifies you of the
violation by some reasonable means, this is the first time you have
received notice of violation of this License (for any work) from that
copyright holder, and you cure the violation prior to 30 days after
your receipt of the notice.
Termination of your rights under this section does not terminate the
licenses of parties who have received copies or rights from you under
this License. If your rights have been terminated and not permanently
reinstated, receipt of a copy of some or all of the same material does
not give you any rights to use it.
@item
FUTURE REVISIONS OF THIS LICENSE
The Free Software Foundation may publish new, revised versions
of the GNU Free Documentation License from time to time. Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns. See
@uref{https://www.gnu.org/copyleft/}.
Each version of the License is given a distinguishing version number.
If the Document specifies that a particular numbered version of this
License ``or any later version'' applies to it, you have the option of
following the terms and conditions either of that specified version or
of any later version that has been published (not as a draft) by the
Free Software Foundation. If the Document does not specify a version
number of this License, you may choose any version ever published (not
as a draft) by the Free Software Foundation. If the Document
specifies that a proxy can decide which future versions of this
License can be used, that proxy's public statement of acceptance of a
version permanently authorizes you to choose that version for the
Document.
@item
RELICENSING
``Massive Multiauthor Collaboration Site'' (or ``MMC Site'') means any
World Wide Web server that publishes copyrightable works and also
provides prominent facilities for anybody to edit those works. A
public wiki that anybody can edit is an example of such a server. A
``Massive Multiauthor Collaboration'' (or ``MMC'') contained in the
site means any set of copyrightable works thus published on the MMC
site.
``CC-BY-SA'' means the Creative Commons Attribution-Share Alike 3.0
license published by Creative Commons Corporation, a not-for-profit
corporation with a principal place of business in San Francisco,
California, as well as future copyleft versions of that license
published by that same organization.
``Incorporate'' means to publish or republish a Document, in whole or
in part, as part of another Document.
An MMC is ``eligible for relicensing'' if it is licensed under this
License, and if all works that were first published under this License
somewhere other than this MMC, and subsequently incorporated in whole
or in part into the MMC, (1) had no cover texts or invariant sections,
and (2) were thus incorporated prior to November 1, 2008.
The operator of an MMC Site may republish an MMC contained in the site
under CC-BY-SA on the same site at any time before August 1, 2009,
provided the MMC is eligible for relicensing.
@end enumerate
@c fakenode --- for prepinfo
@unnumberedsec ADDENDUM: How to use this License for your documents
To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and
license notices just after the title page:
@smallexample
@group
Copyright (C) @var{year} @var{your name}.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
Texts. A copy of the license is included in the section entitled ``GNU
Free Documentation License''.
@end group
@end smallexample
If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
replace the ``with@dots{}Texts.'' line with this:
@smallexample
@group
with the Invariant Sections being @var{list their titles}, with
the Front-Cover Texts being @var{list}, and with the Back-Cover Texts
being @var{list}.
@end group
@end smallexample
If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.
If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License,
to permit their use in free software.
@end ifclear
@ifnotdocbook
@node Index
@unnumbered Index
@end ifnotdocbook
@printindex cp
@bye
Unresolved Issues:
------------------
1. From ADR.
Robert J. Chassell points out that awk programs should have some indication
of how to use them. It would be useful to perhaps have a "programming
style" section of the manual that would include this and other tips.
Consistency issues:
/.../ regexps are in @code, not @samp
".." strings are in @code, not @samp
no @print before @dots
values of expressions in the text (@code{x} has the value 15),
should be in roman, not @code
Use TAB and not tab
Use ESC and not ESCAPE
Use space and not blank to describe the space bar's character
The term "blank" is thus basically reserved for "blank lines" etc.
To make dark corners work, the @value{DARKCORNER} has to be outside
closing `.' of a sentence and after (pxref{...}).
Make sure that each @value{DARKCORNER} has an index entry, and
also that each `@cindex dark corner' has an @value{DARKCORNER}.
" " should have an @w{} around it
Use "non-" only with language names or acronyms, or the words bug and option and null
Use @command{ftp} when talking about anonymous ftp
Use uppercase and lowercase, not "upper-case" and "lower-case"
or "upper case" and "lower case"
Use "single precision" and "double precision", not "single-precision" or "double-precision"
Use alphanumeric, not alpha-numeric
Use POSIX-compliant, not POSIX compliant
Use --foo, not -Wfoo when describing long options
Use "Bell Laboratories", but not "Bell Labs".
Use "behavior" instead of "behaviour".
Use "coprocess" instead of "co-process".
Use "zeros" instead of "zeroes".
Use "nonzero" not "non-zero".
Use "runtime" not "run time" or "run-time".
Use "command-line" as an adjective and "command line" as a noun.
Use "online" not "on-line".
Use "whitespace" not "white space".
Use "Input/Output", not "input/output". Also "I/O", not "i/o".
Use "lefthand"/"righthand", not "left-hand"/"right-hand".
Use "workaround", not "work-around".
Use "startup"/"cleanup", not "start-up"/"clean-up"
Use "filesystem", not "file system"
Use @code{do}, and not @code{do}-@code{while}, except where
actually discussing the do-while.
Use "versus" in text and "vs." in index entries
Use @code{"C"} for the C locale, not ``C'' or @samp{C}.
The words "a", "and", "as", "between", "for", "from", "in", "of",
"on", "that", "the", "to", "with", and "without",
should not be capitalized in @chapter, @section etc.
"Into" and "How" should.
Search for @dfn; make sure important items are also indexed.
"e.g." should always be followed by a comma.
"i.e." should always be followed by a comma.
The numbers zero through ten should be spelled out, except when
talking about file descriptor numbers. > 10 and < 0, it's
ok to use numbers.
For most cases, do NOT put a comma before "and", "or" or "but".
But exercise taste with this rule.
Don't show the awk command with a program in quotes when it's
just the program. I.e.
{
....
}
not
awk '{
...
}'
Do show it when showing command-line arguments, data files, etc, even
if there is no output shown.
Use numbered lists only to show a sequential series of steps.
Use @code{xxx} for the xxx operator in indexing statements, not @samp.
Use MS-Windows not MS Windows
Use MS-DOS not MS DOS
Use an empty set of parentheses after built-in and awk function names.
Use "multiFOO" without a hyphen.
Use "time zone" as two words, not "timezone".
Date: Wed, 13 Apr 94 15:20:52 -0400
From: rms@gnu.org (Richard Stallman)
To: gnu-prog@gnu.org
Subject: A reminder: no pathnames in GNU
It's a GNU convention to use the term "file name" for the name of a
file, never "pathname". We use the term "path" for search paths,
which are lists of file names. Using it for a single file name as
well is potentially confusing to users.
So please check any documentation you maintain, if you think you might
have used "pathname".
Note that "file name" should be two words when it appears as ordinary
text. It's ok as one word when it's a metasyntactic variable, though.
------------------------
ORA uses filename, thus the macro.
Suggestions:
------------
Better sidebars can almost sort of be done with:
@ifdocbook
@macro @sidebar{title, content}
@inlinefmt{docbook, <sidebar><title>}
\title\
@inlinefmt{docbook, </title>}
\content\
@inlinefmt{docbook, </sidebar>}
@end macro
@end ifdocbook
@ifnotdocbook
@macro @sidebar{title, content}
@cartouche
@center @b{\title\}
\content\
@end cartouche
@end macro
@end ifnotdocbook
But to use it you have to say
@sidebar{Title Here,
@include file-with-content
}
which sorta sucks.
TODO:
Add a section explaining recursion from ground zero. Probably
easiest to do it with factorial as the example. Explain that
recursion needs a stopping condition. Thanks to
Bill Duncan <bduncan@beachnet.org> for the suggestion.
|