_M_A_W_K(1)                          User commands                         _M_A_W_K(1)

NNAAMMEE
       mawk - pattern scanning and text processing language

SSYYNNOOPPSSIISS
       mmaawwkk  [-WW  _o_p_t_i_o_n]  [-FF _v_a_l_u_e] [-vv _v_a_r_=_v_a_l_u_e] [--] 'program text' [file
       ...]
       mmaawwkk [-WW _o_p_t_i_o_n] [-FF _v_a_l_u_e] [-vv _v_a_r_=_v_a_l_u_e] [-ff _p_r_o_g_r_a_m_-_f_i_l_e] [--] [file
       ...]

DDEESSCCRRIIPPTTIIOONN
       mmaawwkk is an interpreter for  the  AWK  Programming  Language.   The  AWK
       language  is  useful for manipulation of data files, text retrieval and
       processing, and for  prototyping  and  experimenting  with  algorithms.
       mmaawwkk  is a _n_e_w _a_w_k meaning it implements the AWK language as defined in
       Aho, Kernighan and Weinberger, _T_h_e _A_W_K _P_r_o_g_r_a_m_m_i_n_g  _L_a_n_g_u_a_g_e_,  Addison-
       Wesley  Publishing, 1988 (hereafter referred to as the AWK book.)  mmaawwkk
       conforms to the  POSIX  1003.2  (draft  11.3)  definition  of  the  AWK
       language  which  contains a few features not described in the AWK book,
       and mmaawwkk provides a small number of extensions.

       An AWK program is a sequence of _p_a_t_t_e_r_n  _{_a_c_t_i_o_n_}  pairs  and  function
       definitions.   Short  programs  are entered on the command line usually
       enclosed in ' ' to avoid shell interpretation.  Longer programs can  be
       read  in  from a file with the -f option.  Data  input is read from the
       list of files on the command line or from standard input when the  list
       is empty.  The input is broken into records as determined by the record
       separator   variable,  RRSS.   Initially,  RRSS  =  "\n"  and  records  are
       synonymous with lines.  Each record is compared  against  each  _p_a_t_t_e_r_n
       and if it matches, the program text for _{_a_c_t_i_o_n_} is executed.

OOPPTTIIOONNSS
       -FF _v_a_l_u_e       sets the field separator, FFSS, to _v_a_l_u_e.

       -ff _f_i_l_e        Program  text  is  read  from  _f_i_l_e  instead of from the
                      command line.  Multiple --ff options are allowed.

       -vv _v_a_r_=_v_a_l_u_e   assigns _v_a_l_u_e to program variable _v_a_r.

       --             indicates the unambiguous end of options.

       The  above  options  will  be  available  with  any  POSIX   compatible
       implementation  of  AWK.   Implementation specific options are prefaced
       with --WW.  mmaawwkk provides these:

       -WW dump
              writes an assembler like listing of the internal  representation
              of   the   program   to   _s_t_d_o_u_t  and  exits  0  (on  successful
              compilation).

       -WW exec _f_i_l_e
              Program text is read from _f_i_l_e and this is the last option.

              This is a useful alternative to -ff on systems that  support  the
              ##!!   "magic  number"  convention  for executable scripts.  Those
              implicitly pass the pathname of the script itself as  the  final
              parameter,  and  expect  no  more  than one "-" option on the ##!!
              line.  Because mmaawwkk can combine multiple -WW options separated by
              commas, you can use this option when an additional -WW option  is
              needed.

       -WW help
              prints a usage message to _s_t_d_e_r_r and exits (same as "-WW usage").

       -WW interactive
              changes  the  buffering  of  _s_t_d_o_u_t  and  _s_t_d_i_n  to make it more
              responsive in interactive use.

              Normally mmaawwkk does not change the  standard  streams  buffering,
              which uses line-buffering _s_t_d_i_n and _s_t_d_o_u_t if they are connected
              to  a  terminal, and block-buffering otherwise (e.g., if mmaawwkk is
              run in a pipe).

              When opening a pipe, a special file (such as "-"), or one of the
              stdio devices, mmaawwkk first opens a file  descriptor.   MMaawwkk  then
              decides  whether  to  use  buffered  I/O by checking if the file
              descriptor is for a terminal, and if RRSS is currently set to  the
              single  character  "\n"  (newline).   As  a  special  case, file
              descriptor zero (0) is assigned to _s_t_d_i_n, while  ffddooppeenn  handles
              other file descriptors.

              The  iinntteerraaccttiivvee  option bypasses both checks in deciding to use
              buffered I/O (is a terminal, and RRSS is "\n").   The  iinntteerraaccttiivvee
              option also changes _s_t_d_o_u_t to unbuffered (like _s_t_d_e_r_r).

              MMaawwkk changes streams to unbuffered I/O in a few other cases:

              +o   if a file is created or appended to, i.e., using ">" or ">>"
                  mmaawwkk  treats  this  differently  from  opening  pipes, first
                  opening it as a stream (block buffered) and then changing it
                  to unbuffered if it happens to be a terminal.

              +o   if the standard output is connected to a  terminal  and  the
                  the  iinntteerraaccttiivvee  option  was  not given, mmaawwkk changes it to
                  unbuffered.

       -WW posix
              modifies mmaawwkk's behavior to be more POSIX-compliant:

              +o   forces mmaawwkk not to consider '\n' to be space.

                  The original "posix_space" is recognized, but deprecated.

              +o   Allow  hexadecimal,  "inf"  (infinity)  and  "nan"   (not-a-
                  number).

                  The  Open  Group Base Specifications Issue 8 allows but does
                  not require these features.

       -WW random=_n_u_m
              calls ssrraanndd with the given parameter (and  overrides  the  auto-
              seeding behavior).

       -WW sprintf=_n_u_m
              adjusts the size of mmaawwkk's internal sprintf buffer to _n_u_m bytes.
              More  than  rare  use  of  this  option indicates mmaawwkk should be
              recompiled.

       -WW traditional
              Omit features  such  as  interval  expressions  which  were  not
              supported by traditional _a_w_k.

       -WW usage
              prints a usage message to _s_t_d_e_r_r and exits (same as "-WW help").

       -WW version
              mmaawwkk  writes  its  version  and copyright to _s_t_d_o_u_t and compiled
              limits to _s_t_d_e_r_r and exits 0.

       mmaawwkk accepts abbreviations for any of these options, e.g.,  "-WW v"  and
       "-WWv" both tell mmaawwkk to show its version.

       mmaawwkk  allows  multiple  --WW  options  to  be  combined by separating the
       options with commas, e.g., -Wsprint=2000,posix.   This  is  useful  for
       executable ##!!  "magic number" invocations in which only one argument is
       supported, e.g., -WWiinntteerraaccttiivvee,,eexxeecc.

TTHHEE AAWWKK LLAANNGGUUAAGGEE
   11.. PPrrooggrraamm ssttrruuccttuurree
       An  AWK  program  is  a  sequence  of  _p_a_t_t_e_r_n  _{_a_c_t_i_o_n_} pairs and user
       function definitions.

       A pattern can be:
            BBEEGGIINN
            EENNDD
            expression
            expression , expression

       One, but not both, of _p_a_t_t_e_r_n _{_a_c_t_i_o_n_} can be omitted.  If _{_a_c_t_i_o_n_}  is
       omitted  it is implicitly { print }.  If _p_a_t_t_e_r_n is omitted, then it is
       implicitly matched.  BBEEGGIINN and EENNDD patterns require an action.

       Statements are terminated by newlines, semi-colons or both.  Groups  of
       statements such as actions or loop bodies are blocked via { ... } as in
       C.   The  last  statement  in a block doesn't need a terminator.  Blank
       lines have no meaning; an empty statement is terminated  with  a  semi-
       colon.   Long  statements  can  be  continued  with  a backslash, \.  A
       statement can be broken without a backslash after a comma, left  brace,
       &&,  ||,  ddoo,  eellssee,  the  right  parenthesis  of  an  iiff, wwhhiillee or ffoorr
       statement, and the right  parenthesis  of  a  function  definition.   A
       comment  starts  with # and extends to, but does not include the end of
       line.

       The following statements control program flow inside blocks.

            iiff ( _e_x_p_r ) _s_t_a_t_e_m_e_n_t

            iiff ( _e_x_p_r ) _s_t_a_t_e_m_e_n_t eellssee _s_t_a_t_e_m_e_n_t

            wwhhiillee ( _e_x_p_r ) _s_t_a_t_e_m_e_n_t

            ddoo _s_t_a_t_e_m_e_n_t wwhhiillee ( _e_x_p_r )

            ffoorr ( _o_p_t___e_x_p_r ; _o_p_t___e_x_p_r ; _o_p_t___e_x_p_r ) _s_t_a_t_e_m_e_n_t

            ffoorr ( _v_a_r iinn _a_r_r_a_y ) _s_t_a_t_e_m_e_n_t

            ccoonnttiinnuuee

            bbrreeaakk

   22.. DDaattaa ttyyppeess,, ccoonnvveerrssiioonn aanndd ccoommppaarriissoonn
       There are two basic data types, numeric and string.  Numeric  constants
       can  be  integer  like -2, decimal like 1.08, or in scientific notation
       like -1.1e4 or .28E-3.  All numbers are represented internally and  all
       computations  are  done  in floating point arithmetic.  So for example,
       the expression 0.2e2 == 20 is true and true is represented as 1.0.

       String constants are enclosed in double quotes.

                   "This is a string with a newline at the end.\n"

       Strings can be continued across a line by  escaping  (\)  the  newline.
       The following escape sequences are recognized.

            \\        \
            \"        "
            \a        alert, ascii 7
            \b        backspace, ascii 8
            \t        tab, ascii 9
            \n        newline, ascii 10
            \v        vertical tab, ascii 11
            \f        formfeed, ascii 12
            \r        carriage return, ascii 13
            \ddd      1, 2 or 3 octal digits for ascii ddd
            \xhh      1 or 2 hex digits for ascii  hh

       If  you  escape  any other character \c, you get \c, i.e., mmaawwkk ignores
       the escape.

       There are really three basic data types; the third is _n_u_m_b_e_r _a_n_d _s_t_r_i_n_g
       which has both a numeric value and a string value  at  the  same  time.
       User  defined  variables  come into existence when first referenced and
       are initialized to _n_u_l_l, a number and string value  which  has  numeric
       value  0 and string value "".  Non-trivial number and string typed data
       come from input and are typically stored in fields.  (See section 4).

       The type of an expression is determined by its  context  and  automatic
       type  conversion  occurs  if  needed.   For  example,  to  evaluate the
       statements

            y = x + 2  ;  z = x  "hello"

       The value stored in variable y will be typed  numeric.   If  x  is  not
       numeric,  the  value  read  from x is converted to numeric before it is
       added to 2 and stored in y.  The value stored in  variable  z  will  be
       typed  string,  and  the  value  of  x  will  be converted to string if
       necessary and concatenated with "hello".  (Of  course,  the  value  and
       type  stored  in  x  is  not  changed  by  any  conversions.)  A string
       expression is converted to numeric using its longest numeric prefix  as
       with aattooff(3).  A numeric expression is converted to string by replacing
       _e_x_p_r with sspprriinnttff((CCOONNVVFFMMTT, _e_x_p_r), unless _e_x_p_r can be represented on the
       host  machine as an exact integer then it is converted to sspprriinnttff("%d",
       _e_x_p_r).  SSpprriinnttff(()) is an AWK built-in that duplicates the  functionality
       of  sspprriinnttff(3),  and  CCOONNVVFFMMTT  is a built-in variable used for internal
       conversion from number to string and initialized to  "%.6g".   Explicit
       type  conversions  can  be  forced,  _e_x_p_r  ""  is  string and _e_x_p_r+0 is
       numeric.

       To evaluate, _e_x_p_r1 rreell--oopp _e_x_p_r2, if both operands are numeric or number
       and string then the comparison is numeric; if both operands are  string
       the  comparison  is  string;  if  one operand is string, the non-string
       operand is converted and the  comparison  is  string.   The  result  is
       numeric, 1 or 0.

       In boolean contexts such as, iiff ( _e_x_p_r ) _s_t_a_t_e_m_e_n_t, a string expression
       evaluates  true  if  and only if it is not the empty string ""; numeric
       values if and only if not numerically zero.

   33.. RReegguullaarr eexxpprreessssiioonnss
       In the AWK language, records, fields and strings are often  tested  for
       matching  a  _r_e_g_u_l_a_r  _e_x_p_r_e_s_s_i_o_n.   Regular expressions are enclosed in
       slashes, and

            _e_x_p_r ~ /_r/

       is an AWK expression that evaluates to 1 if  _e_x_p_r  "matches"  _r,  which
       means  a substring of _e_x_p_r is in the set of strings defined by _r.  With
       no match the expression evaluates to  0;  replacing  ~  with  the  "not
       match" operator, !~ , reverses the meaning.  As  pattern-action pairs,

            /_r/ { _a_c_t_i_o_n }   and   $$00 ~ /_r/ { _a_c_t_i_o_n }

       are  the  same,  and  for  each  input record that matches _r, _a_c_t_i_o_n is
       executed.  In fact, /_r/ is an AWK expression that is equivalent to  ($$00
       ~  /_r/)  anywhere  except when on the right side of a match operator or
       passed as an argument to a built-in function  that  expects  a  regular
       expression argument.

       AWK uses extended regular expressions as with the --EE option of ggrreepp(1).
       The regular expression metacharacters, i.e., those with special meaning
       in regular expressions are

            \ ^ $ . [ ] | ( ) * + ? { }

       If the command line option _-_W _t_r_a_d_i_t_i_o_n_a_l is used, these are omitted:

            { }

       are  also  regular expression metacharacters, and in this mode, require
       escaping to be a literal character.

       Regular expressions are built up from characters as follows:

            _c            matches any non-metacharacter _c.

            \_c           matches  a  character  defined  by  the  same  escape
                         sequences  used  in  string  constants or the literal
                         character _c if \_c is not an escape sequence.

            .            matches any character (including newline).

            ^            matches the front of a string.

            $            matches the back of a string.

            [c1c2c3...]  matches any character in the  class  c1c2c3... .   An
                         interval  of  characters  is  denoted  c1-c2 inside a
                         class [...].

            [^c1c2c3...] matches any character not in the class c1c2c3...

       Regular expressions are built up  from  other  regular  expressions  as
       follows:

            _r1_r2         matches     _r1    followed    immediately    by    _r2
                         (_c_o_n_c_a_t_e_n_a_t_i_o_n).


            _r1 | _r2      matches _r1 or _r2 (_a_l_t_e_r_n_a_t_i_o_n).


            _r*           matches _r repeated zero or more times.

            _r+           matches _r repeated one or more times.

            _r?           matches _r zero or once.  (_r_e_p_e_t_i_t_i_o_n).

            (_r)          matches _r (_g_r_o_u_p_i_n_g).


            _r{n}         matches _r exactly n times.

            _r{n,}        matches _r repeated n or more times.

            _r{n,m}       matches _r repeated n to m (inclusive) times.

            _r{,m}        matches _r repeated  0  to  m  times  (a  non-standard
                         option).

       The increasing pprreecceeddeennccee ooff ooppeerraattoorrss is:

       alternation concatenation repetition grouping


       For example,

            /^[_a-zA-Z][_a-zA-Z0-9]*$/  and
            /^[-+]?([0-9]+\.?|\.[0-9])[0-9]*([eE][-+]?[0-9]+)?$/

       are  matched by AWK identifiers and AWK numeric constants respectively.
       Note that "." has to be escaped to be recognized as  a  decimal  point,
       and that metacharacters are not special inside character classes.

       Any  expression  can  be  used  on  the  right hand side of the ~ or !~
       operators or passed to a built-in that expects  a  regular  expression.
       If needed, it is converted to string, and then interpreted as a regular
       expression.  For example,

            BEGIN { identifier = "[_a-zA-Z][_a-zA-Z0-9]*" }

            $0 ~ "^" identifier

       prints all lines that start with an AWK identifier.

       mmaawwkk  recognizes  the  empty  regular expression, //, which matches the
       empty string and hence is matched by any string at the front, back  and
       between every character.  For example,

            echo  abc | mawk '{ gsub(//, "X")' ; print }
            XaXbXcX


   44.. RReeccoorrddss aanndd ffiieellddss
       Records are read in one at a time, and stored in the _f_i_e_l_d variable $$00.
       The  record  is split into _f_i_e_l_d_s which are stored in $$11, $$22, ..., $$NNFF.
       The built-in variable NNFF is set to the number of fields, and NNRR and FFNNRR
       are incremented by 1.  Fields above $$NNFF are set to "".

       Assignment to $$00 causes the fields and NNFF to be recomputed.  Assignment
       to NNFF or to a field causes $$00 to be reconstructed by concatenating  the
       $$ii''ss  separated  by OOFFSS.  Assignment to a field with index greater than
       NNFF, increases NNFF and causes $$00 to be reconstructed.

       Data input stored in fields is string,  unless  the  entire  field  has
       numeric form and then the type is number and string.  For example,

            echo 24 24E |
            mawk '{ print($1>100, $1>"100", $2>100, $2>"100") }'
            0 1 1 1

       $$00 and $$22 are string and $$11 is number and string.  The first comparison
       is numeric, the second is string, the third is string (100 is converted
       to "100"), and the last is string.

   55.. EExxpprreessssiioonnss aanndd ooppeerraattoorrss
       The expression syntax is similar to C.  Primary expressions are numeric
       constants,  string  constants,  variables,  fields, arrays and function
       calls.  The identifier for a variable,  array  or  function  can  be  a
       sequence of letters, digits and underscores, that does not start with a
       digit.   Variables  are  not declared; they exist when first referenced
       and are initialized to _n_u_l_l.

       New expressions are composed with the following operators in  order  of
       increasing precedence.

            _a_s_s_i_g_n_m_e_n_t          =  +=  -=  *=  /=  %=  ^=
            _c_o_n_d_i_t_i_o_n_a_l         ?  :
            _l_o_g_i_c_a_l _o_r          ||
            _l_o_g_i_c_a_l _a_n_d         &&
            _a_r_r_a_y _m_e_m_b_e_r_s_h_i_p    iinn
            _m_a_t_c_h_i_n_g       ~   !~
            _r_e_l_a_t_i_o_n_a_l          <  >   <=  >=  ==  !=
            _c_o_n_c_a_t_e_n_a_t_i_o_n       (no explicit operator)
            _a_d_d _o_p_s             +  -
            _m_u_l _o_p_s             *  /  %
            _u_n_a_r_y               +  -
            _l_o_g_i_c_a_l _n_o_t         !
            _e_x_p_o_n_e_n_t_i_a_t_i_o_n      ^
            _i_n_c _a_n_d _d_e_c         ++ -- (both post and pre)
            _f_i_e_l_d               $

       Assignment, conditional and exponentiation associate right to left; the
       other  operators  associate  left  to  right.   Any  expression  can be
       parenthesized.

   66.. AArrrraayyss
       Awk provides one-dimensional arrays.  Array elements are  expressed  as
       _a_r_r_a_y[_e_x_p_r].   _E_x_p_r  is  internally  converted  to string type, so, for
       example, A[1] and A["1"] are the same element and the actual  index  is
       "1".    Arrays  indexed  by  strings  are  called  associative  arrays.
       Initially an array is empty; elements exist when  first  accessed.   An
       expression, _e_x_p_r iinn _a_r_r_a_y evaluates to 1 if _a_r_r_a_y[_e_x_p_r] exists, else to
       0.

       There  is  a form of the ffoorr statement that loops over each index of an
       array.

            ffoorr ( _v_a_r iinn _a_r_r_a_y ) _s_t_a_t_e_m_e_n_t

       sets _v_a_r to each index of _a_r_r_a_y and executes _s_t_a_t_e_m_e_n_t.  The order that
       _v_a_r transverses the indices of _a_r_r_a_y is not defined.

       The statement, ddeelleettee _a_r_r_a_y[_e_x_p_r], causes  _a_r_r_a_y[_e_x_p_r]  not  to  exist.
       mmaawwkk  supports  the ddeelleettee _a_r_r_a_y feature, which deletes all elements of
       _a_r_r_a_y.

       Multidimensional arrays are synthesized with  concatenation  using  the
       built-in   variable   SSUUBBSSEEPP.    _a_r_r_a_y[_e_x_p_r1,_e_x_p_r2]  is  equivalent  to
       _a_r_r_a_y[_e_x_p_r1 SSUUBBSSEEPP _e_x_p_r2].  Testing for a multidimensional element uses
       a parenthesized index, such as

            if ( (i, j) in A )  print A[i, j]


   77.. BBuuiillttiinn--vvaarriiaabblleess
       The following variables are built-in  and  initialized  before  program
       execution.

            AARRGGCC   number of command line arguments.

            AARRGGVV   array of command line arguments, 0..ARGC-1.

            CCOONNVVFFMMTT
                   format  for  internal  conversion  of  numbers  to  string,
                   initially = "%.6g".

            EENNVVIIRROONN
                   array indexed by  environment  variables.   An  environment
                   string, _v_a_r_=_v_a_l_u_e is stored as EENNVVIIRROONN[_v_a_r] = _v_a_l_u_e.

            FFIILLEENNAAMMEE
                   name of the current input file.

            FFNNRR    current record number in FFIILLEENNAAMMEE.

            FFSS     splits records into fields as a regular expression.

            NNFF     number of fields in the current record.

            NNRR     current record number in the total input stream.

            OOFFMMTT   format for printing numbers; initially = "%.6g".

            OOFFSS    inserted between fields on output, initially = " ".

            OORRSS    terminates each record on output, initially = "\n".

            RRLLEENNGGTTHH
                   length  set  by  the  last  call  to the built-in function,
                   mmaattcchh(()).

            RRSS     input record separator, initially = "\n".

            RRSSTTAARRTT index set by the last call to mmaattcchh(()).

            SSUUBBSSEEPP used  to  build  multiple  array  subscripts,  initially  =
                   "\034".

   88.. BBuuiilltt--iinn ffuunnccttiioonnss
       SSttrriinngg ffuunnccttiioonnss

            gsub(_r_,_s_,_t)  gsub(_r_,_s)
                   Global substitution, every match of regular expression _r in
                   variable  _t  is  replaced  by  string  _s.   The  number  of
                   replacements is returned.  If _t is omitted, $$00 is used.  An
                   _& in the replacement string _s is replaced  by  the  matched
                   substring   of  _t.   \&  and  \\  put   literal  &  and  \,
                   respectively, in the replacement string.

            index(_s_,_t)
                   If _t is a substring of _s, then the position where _t  starts
                   is  returned, else 0 is returned.  The first character of _s
                   is in position 1.

            length(_s)
                   Returns the length of string or array _s.

            match(_s_,_r)
                   Returns the index of the first  longest  match  of  regular
                   expression  _r  in  string  _s.  Returns 0 if no match.  As a
                   side effect, RRSSTTAARRTT is set to the return value.  RRLLEENNGGTTHH is
                   set to the length of the match or -1 if no match.   If  the
                   empty  string  is  matched,  RRLLEENNGGTTHH  is set to 0, and 1 is
                   returned if the match is at the front, and  length(_s)+1  is
                   returned if the match is at the back.

            split(_s_,_A_,_r)  split(_s_,_A)
                   String  _s  is split into fields by regular expression _r and
                   the fields are loaded into array _A.  The number  of  fields
                   is  returned.   See section 11 below for more detail.  If _r
                   is omitted, FFSS is used.

            sprintf(_f_o_r_m_a_t_,_e_x_p_r_-_l_i_s_t)
                   Returns a string constructed from  _e_x_p_r_-_l_i_s_t  according  to
                   _f_o_r_m_a_t.  See the description of printf() below.

            sub(_r_,_s_,_t)  sub(_r_,_s)
                   Single  substitution,  same  as  gsub()  except at most one
                   substitution.

            substr(_s_,_i_,_n)  substr(_s_,_i)
                   Returns the substring of string _s, starting at index _i,  of
                   length  _n.  If _n is omitted, the suffix of _s, starting at _i
                   is returned.

            tolower(_s)
                   Returns  a  copy  of  _s  with  all  upper  case  characters
                   converted to lower case.

            toupper(_s)
                   Returns  a  copy  of  _s  with  all  lower  case  characters
                   converted to upper case.

       TTiimmee ffuunnccttiioonnss

       These are available on systems which support the corresponding C mmkkttiimmee
       and ssttrrffttiimmee functions:

            mktime(_s_p_e_c_i_f_i_c_a_t_i_o_n)
                   converts a date specification to a timestamp with the  same
                   units  as  ssyyssttiimmee.   The  date  specification  is a string
                   containing the components of the date as decimal integers:

                   YYYYYYYY
                      the year, e.g., 2012

                   MMMM the month of the year starting at 1

                   DDDD the day of the month starting at 1

                   HHHH hour (0-23)

                   MMMM minute (0-59)

                   SSSS seconds (0-59)

                   DDSSTT
                      tells how to  treat  timezone  versus  daylight  savings
                      time:

                        positive
                           DST is in effect

                        zero (default)
                           DST is not in effect

                        negative
                           mktime()   should  (use  timezone  information  and
                           system databases to) attempt  to determine  whether
                           DST is in effect at the specified time.

            strftime([_f_o_r_m_a_t [, _t_i_m_e_s_t_a_m_p [, _u_t_c ]]])
                   formats the given timestamp using the format (passed to the
                   C ssttrrffttiimmee function):

                   +o   If the _f_o_r_m_a_t parameter is missing, "%c" is used.

                   +o   If  the  _t_i_m_e_s_t_a_m_p  parameter  is  missing, the current
                       value from ssyyssttiimmee is used.

                   +o   If the _u_t_c parameter is present and nonzero, the result
                       is in UTC.  Otherwise local time is used.

            systime()
                   returns the current time of day as the  number  of  seconds
                   since the Epoch (1970-01-01 00:00:00 UTC on POSIX systems).

       AArriitthhmmeettiicc ffuunnccttiioonnss

            atan2(_y_,_x)
                   Arctan of _y/_x between -pi and pi.

            cos(_x) Cosine function, _x in radians.

            exp(_x) Exponential function.

            int(_x) Returns _x truncated towards zero.

            log(_x) Natural logarithm.

            rand() Returns a random number between zero and one.

            sin(_x) Sine function, _x in radians.

            sqrt(_x)
                   Returns square root of _x.

            srand(_e_x_p_r)

            srand()
                   Seeds  the random number generator, using the clock if _e_x_p_r
                   is omitted, and returns the value  of  the  previous  seed.
                   Srand(_e_x_p_r)   is   useful   for   repeating  pseudo  random
                   sequences.

                   Note: mmaawwkk is normally configured to seed the random number
                   generator from the clock at startup, making it  unnecessary
                   to  call  srand().   This  feature  can  be  suppressed via
                   conditional  compile,  or  overridden  using  the  --WWrraannddoomm
                   option.

   99.. IInnppuutt aanndd oouuttppuutt
       There are two output statements, pprriinntt and pprriinnttff.

            print  writes $$00  OORRSS to standard output.

            print _e_x_p_r1, _e_x_p_r2, ..., _e_x_p_rn
                   writes  _e_x_p_r1  OOFFSS  _e_x_p_r2  OOFFSS  ...  _e_x_p_rn  OORRSS to standard
                   output.  Numeric expressions are converted to  string  with
                   OOFFMMTT.

            printf _f_o_r_m_a_t_, _e_x_p_r_-_l_i_s_t
                   duplicates   the  printf  C  library  function  writing  to
                   standard output.  The complete ANSI C format specifications
                   are recognized with conversions %c, %d, %e, %E, %f, %g, %G,
                   %i, %o, %s, %u, %x, %X and %%, and conversion qualifiers  h
                   and l.

       The  argument  list  to  print  or printf can optionally be enclosed in
       parentheses.  Print formats  numbers  using  OOFFMMTT  or  "%d"  for  exact
       integers.   "%c" with a numeric argument prints the corresponding 8 bit
       character, with a string argument it prints the first character of  the
       string.   The output of print and printf can be redirected to a file or
       command by appending > _f_i_l_e, >> _f_i_l_e or | _c_o_m_m_a_n_d to  the  end  of  the
       print   statement.   Redirection  opens  _f_i_l_e  or  _c_o_m_m_a_n_d  only  once,
       subsequent  redirections  append  to  the  already  open  stream.    By
       convention, mmaawwkk associates the filename

          +o   "/dev/stderr" with _s_t_d_e_r_r,

          +o   "/dev/stdout" with _s_t_d_o_u_t,

          +o   "-" and "/dev/stdin" with _s_t_d_i_n.

       The  association  with  _s_t_d_e_r_r  is  especially useful because it allows
       print and printf to be redirected to _s_t_d_e_r_r.  These names can  also  be
       passed to functions.

       The input function ggeettlliinnee has the following variations.

            getline
                   reads into $$00, updates the fields, NNFF, NNRR and FFNNRR.

            getline < _f_i_l_e
                   reads into $$00 from _f_i_l_e, updates the fields and NNFF.

            getline _v_a_r
                   reads the next record into _v_a_r, updates NNRR and FFNNRR.

            getline _v_a_r < _f_i_l_e
                   reads the next record of _f_i_l_e into _v_a_r.

            _c_o_m_m_a_n_d | getline
                   pipes  a record from _c_o_m_m_a_n_d into $$00 and updates the fields
                   and NNFF.

            _c_o_m_m_a_n_d | getline _v_a_r
                   pipes a record from _c_o_m_m_a_n_d into _v_a_r.

       Getline returns 0 on end-of-file, -1 on error, otherwise 1.

       Commands on the end of pipes are executed by /bin/sh.

       The function cclloossee(_e_x_p_r) closes the file or pipe associated with  _e_x_p_r.
       Close  returns  0 if _e_x_p_r is an open file, the exit status if _e_x_p_r is a
       piped command, and -1 otherwise.  Close is used to  reread  a  file  or
       command,  make  sure  the  other  end  of an output pipe is finished or
       conserve file resources.

       The function fffflluusshh(_e_x_p_r) flushes the output file  or  pipe  associated
       with  _e_x_p_r.  Fflush returns 0 if _e_x_p_r is an open output stream else -1.
       Fflush without an  argument  flushes  _s_t_d_o_u_t.   Fflush  with  an  empty
       argument ("") flushes all open output.

       The  function  ssyysstteemm(_e_x_p_r)  uses  the C runtime ssyysstteemm call to execute
       _e_x_p_r and returns the  corresponding  wait  status  of  the  command  as
       follows:

       +o   if  the  ssyysstteemm call failed, setting the status to -1, mmaawwkk returns
           that value.

       +o   if the command exited normally, mmaawwkk returns its exit-status.

       +o   if the command exited due to a signal such as SSIIGGHHUUPP, mmaawwkk  returns
           the signal number plus 256.

       Changes  made  to the EENNVVIIRROONN array are not passed to commands executed
       with ssyysstteemm or pipes.

   1100.. UUsseerr ddeeffiinneedd ffuunnccttiioonnss
       The syntax for a user defined function is

            ffuunnccttiioonn name( _a_r_g_s ) { _s_t_a_t_e_m_e_n_t_s }

       The function body can contain a return statement

            rreettuurrnn _o_p_t___e_x_p_r

       A return statement is not required.  Function calls may  be  nested  or
       recursive.   Functions  are  passed  expressions by value and arrays by
       reference.   Extra  arguments  serve  as  local   variables   and   are
       initialized to _n_u_l_l.  For example, csplit(_s_,_A) puts each character of _s
       into array _A and returns the length of _s.

            function csplit(s, A,    n, i)
            {
              n = length(s)
              for( i = 1 ; i <= n ; i++ ) A[i] = substr(s, i, 1)
              return n
            }

       Putting  extra  space  between  passed arguments and local variables is
       conventional.  Functions can be referenced before they are defined, but
       the function name and the '(' of the  arguments  must  touch  to  avoid
       confusion with concatenation.

       A function parameter is normally a scalar value (number or string).  If
       there  is  a  forward  reference  to  a  function  using  an array as a
       parameter, the function's corresponding parameter will be treated as an
       array.

   1111.. SSpplliittttiinngg ssttrriinnggss,, rreeccoorrddss aanndd ffiilleess
       Awk programs use the same algorithm to split strings into  arrays  with
       split(), and records into fields on FFSS.  mmaawwkk uses essentially the same
       algorithm to split files into records on RRSS.

       Split(_e_x_p_r_,_A_,_s_e_p) works as follows:

          (1)  If  _s_e_p  is  omitted,  it  is  replaced  by  FFSS.  _S_e_p can be an
               expression or regular expression.  If it is  an  expression  of
               non-string type, it is converted to string.

          (2)  If _s_e_p = " " (a single space), then <SPACE> is trimmed from the
               front  and back of _e_x_p_r, and _s_e_p becomes <SPACE>.  mmaawwkk defines
               <SPACE> as the regular expression /[ \t\n]+/.  Otherwise _s_e_p is
               treated as a regular expression,  except  that  meta-characters
               are  ignored  for  a string of length 1, e.g., split(x, A, "*")
               and split(x, A, /\*/) are the same.

          (3)  If _e_x_p_r is not string, it is converted to string.  If  _e_x_p_r  is
               then the empty string "", split() returns 0 and _A is set empty.
               Otherwise, all non-overlapping, non-null and longest matches of
               _s_e_p in _e_x_p_r, separate _e_x_p_r into fields which are loaded into _A.
               The  fields  are  placed  in  A[1], A[2], ..., A[n] and split()
               returns n, the number of fields which is the number of  matches
               plus  one.  Data placed in _A that looks numeric is typed number
               and string.

       Splitting records into fields works the  same  except  the  pieces  are
       loaded into $$11, $$22,..., $$NNFF.  If $$00 is empty, NNFF is set to 0 and all $$ii
       to "".

       mmaawwkk  splits  files  into  records  by the same algorithm, but with the
       slight  difference  that  RRSS  is  really  a  terminator  instead  of  a
       separator.  (OORRSS is really a terminator too).

            E.g., if FFSS = ":+" and $$00 = "a::b:" , then NNFF = 3 and $$11 = "a", $$22
            = "b" and $$33 = "", but if "a::b:" is the contents of an input file
            and RRSS = ":+", then there are two records "a" and "b".

       RRSS = " " is not special.

       If  FFSS  =  "",  then mmaawwkk breaks the record into individual characters,
       and, similarly, split(_s_,_A_,"") places the  individual  characters  of  _s
       into _A.

   1122.. MMuullttii--lliinnee rreeccoorrddss
       Since  mmaawwkk  interprets  RRSS as a regular expression, multi-line records
       are easy.  Setting RRSS = "\n\n+", makes one or more blank lines separate
       records.  If FFSS = " " (the default), then single newlines, by the rules
       for  <SPACE>  above,  become  space  and  single  newlines  are   field
       separators.

            For example, if

            +o   a file is "a b\nc\n\n",

            +o   RRSS = "\n\n+" and

            +o   FFSS = " ",

            then  there  is one record "a b\nc" with three fields "a", "b" and
            "c":

            +o   using FFSS = "\n", gives two fields "a b" and "c";

            +o   using FFSS = "", gives one field identical to the record.

       If you want lines with spaces or tabs to be considered blank, set RRSS  =
       "\n([ \t]*\n)+".   For  compatibility  with other awks, setting RRSS = ""
       has the same effect as if blank lines are stripped from the  front  and
       back  of  files  and  then  records  are determined as if RRSS = "\n\n+".
       POSIX requires  that  "\n"  always  separates  records  when  RRSS  =  ""
       regardless  of the value of FFSS.  mmaawwkk does not support this convention,
       because defining "\n" as <SPACE> makes it unnecessary.

       Most of the time when you change RRSS for multi-line  records,  you  will
       also want to change OORRSS to "\n\n" so the record spacing is preserved on
       output.

   1133.. PPrrooggrraamm eexxeeccuuttiioonn
       This  section  describes the order of program execution.  First AARRGGCC is
       set to the total  number  of  command  line  arguments  passed  to  the
       execution phase of the program.

       +o   AARRGGVV[[00]] is set to the name of the AWK interpreter and

       +o   AARRGGVV[[11]]   ...    AARRGGVV[[AARRGGCC--11]]  holds  the  remaining  command  line
           arguments exclusive of options and program source.

       For example, with

            mawk  -f  prog  v=1  A  t=hello  B

       AARRGGCC = 5 with
              AARRGGVV[[00]] = "mawk",
              AARRGGVV[[11]] = "v=1",
              AARRGGVV[[22]] = "A",
              AARRGGVV[[33]] = "t=hello" and
              AARRGGVV[[44]] = "B".

       Next, each BBEEGGIINN block is executed in order.  If the  program  consists
       entirely  of  BBEEGGIINN  blocks,  then  execution terminates, else an input
       stream is opened and execution continues.  If AARRGGCC equals 1, the  input
       stream  is  set  to _s_t_d_i_n, else  the command line arguments AARRGGVV[[11]] ...
       AARRGGVV[[AARRGGCC--11]] are examined for a file argument.

       The command line arguments divide  into  three  sets:  file  arguments,
       assignment  arguments and empty strings "".  An assignment has the form
       _v_a_r=_s_t_r_i_n_g.  When an AARRGGVV[[ii]] is examined as a possible  file  argument,
       if  it  is  empty  it  is skipped; if it is an assignment argument, the
       assignment to _v_a_r takes place and ii skips to the  next  argument;  else
       AARRGGVV[[ii]] is opened for input.  If it fails to open, execution terminates
       with exit code 2.  If no command line argument is a file argument, then
       input comes from _s_t_d_i_n.  Getline in a BBEEGGIINN action opens input.  "-" as
       a file argument denotes _s_t_d_i_n.

       Once  an input stream is open, each input record is tested against each
       _p_a_t_t_e_r_n, and if it matches, the  associated  _a_c_t_i_o_n  is  executed.   An
       expression  pattern  matches  if  it  is  boolean  true (see the end of
       section 2).  A BBEEGGIINN pattern matches before any input  has  been  read,
       and  an  EENNDD  pattern  matches  after all input has been read.  A range
       pattern, _e_x_p_r1,_e_x_p_r2 , matches every record between the match of  _e_x_p_r1
       and the match _e_x_p_r2 inclusively.

       When end of file occurs on the input stream, the remaining command line
       arguments  are  examined for a file argument, and if there is one it is
       opened, else the EENNDD _p_a_t_t_e_r_n is considered matched and all EENNDD  _a_c_t_i_o_n_s
       are executed.

       In  the example, the assignment v=1 takes place after the BBEEGGIINN _a_c_t_i_o_n_s
       are executed, and the data placed in v  is  typed  number  and  string.
       Input  is  then  read  from  file A.  On end of file A, t is set to the
       string "hello", and B is opened for input.  On end of file B,  the  EENNDD
       _a_c_t_i_o_n_s are executed.

       Program flow at the _p_a_t_t_e_r_n _{_a_c_t_i_o_n_} level can be changed with the

            nneexxtt
            nneexxttffiillee
            eexxiitt  _o_p_t___e_x_p_r

       statements:

       +o   A  nneexxtt  statement  causes  the  next  input  record to be read and
           pattern testing to restart with the first _p_a_t_t_e_r_n _{_a_c_t_i_o_n_} pair  in
           the program.

       +o   A  nneexxttffiillee  statement  tells  mmaawwkk  to stop processing the current
           input file.  It then updates FILENAME to the next  file  listed  on
           the command line, and resets FNR to 1.

       +o   An  eexxiitt statement causes immediate execution of the EENNDD actions or
           program termination if there are none or if the eexxiitt occurs  in  an
           EENNDD action.  The _o_p_t___e_x_p_r sets the exit value of the program unless
           overridden by a later eexxiitt or subsequent error.

EENNVVIIRROONNMMEENNTT
       MMaawwkk recognizes these variables:

          MAWKBINMODE
             (see CCOOMMPPAATTIIBBIILLIITTYY)

          MAWK_LONG_OPTIONS
             If  this  is  set,  mmaawwkk uses its value to decide what to do with
             GNU-style long options:

               allow  MMaawwkk allows the option to be checked against the (small)
                      set of long options it recognizes.

                      The long names from the --WW option are recognized,  e.g.,
                      ----vveerrssiioonn is derived from --WWvveerrssiioonn.

               error  MMaawwkk  prints  an  error  message and exits.  This is the
                      default.

               ignore MMaawwkk ignores the option, unless it happens to be one  of
                      the one it recognizes.

               warn   Print  an  warning  message  and  otherwise  ignore  the
                      option.

             If the variable is unset, mmaawwkk prints an error message and exits.

          WHINY_USERS
             This is a ggaawwkk 3.1.0 feature, removed in the 4.0.0  release.   It
             tells mmaawwkk to sort array indices before it starts to iterate over
             the elements of an array.

CCOOMMPPAATTIIBBIILLIITTYY
   MMAAWWKK 11..33..33 vveerrssuuss PPOOSSIIXX 11000033..22 DDrraafftt 1111..33
       The  POSIX  1003.2(draft 11.3) definition of the AWK language is AWK as
       described in the AWK book  with  a  few  extensions  that  appeared  in
       SystemVR4 nawk.  The extensions are:

          +o   New functions: toupper() and tolower().

          +o   New variables: ENVIRON[] and CONVFMT.

          +o   ANSI C conversion specifications for printf() and sprintf().

          +o   New  command  options:   -v  var=value,  multiple -f options and
              implementation options as arguments to -W.

          +o   For  systems  (MS-DOS  or  Windows)  which  provide  a   _s_e_t_m_o_d_e
              function,  an  environment  variable  MAWKBINMODE and a built-in
              variable BINMODE.  The bits of the BINMODE value tell mmaawwkk   how
              to modify the RRSS and OORRSS variables:

              0  set standard input to binary mode, and if BIT-2 is unset, set
                 RRSS to "\r\n" (CR/LF) rather than "\n" (LF).

              1  set  standard  output  to binary mode, and if BIT-2 is unset,
                 set OORRSS to "\r\n" (CR/LF) rather than "\n" (LF).

              2  suppress the assignment to RRSS and OORRSS  of  CR/LF,  making  it
                 possible  to  run scripts and generate output compatible with
                 Unix line-endings.

       POSIX AWK is oriented to operate on files a line at a time.  RRSS can  be
       changed  from  "\n" to another single character, but it is hard to find
       any use for this --  there  are  no  examples  in  the  AWK  book.   By
       convention,  RRSS  =  "", makes one or more blank lines separate records,
       allowing multi-line records.  When RRSS = "",  "\n"  is  always  a  field
       separator regardless of the value in FFSS.

       mmaawwkk,  on  the  other hand, allows RRSS to be a regular expression.  When
       "\n" appears in  records,  it  is  treated  as  space,  and  FFSS  always
       determines fields.

       Removing the line at a time paradigm can make some programs simpler and
       can  often  improve  performance.   For example, redoing example 3 from
       above,

            BEGIN { RS = "[^A-Za-z]+" }

            { word[ $0 ] = "" }

            END { delete  word[ "" ]
              for( i in word )  cnt++
              print cnt
            }

       counts the number of unique words by making each  word  a  record.   On
       moderate  size  files,  mmaawwkk  executes  twice  as  fast, because of the
       simplified inner loop.

       The following program replaces each comment by a single space  in  a  C
       program file,

            BEGIN {
              RS = "/\*([^*]|\*+[^/*])*\*+/"
                 # comment is record separator
              ORS = " "
              getline  hold
              }

              { print hold ; hold = $0 }

              END { printf "%s" , hold }

       Buffering  one  record  is  needed to avoid terminating the last record
       with a space.

       With mmaawwkk, the following are all equivalent,

            x ~ /a\+b/    x ~ "a\+b"     x ~ "a\\+b"

       The strings get scanned twice, once  as  string  and  once  as  regular
       expression.   On the string scan, mmaawwkk ignores the escape on non-escape
       characters while the AWK book advocates _\_c be  recognized  as  _c  which
       necessitates  the double escaping of meta-characters in strings.  POSIX
       explicitly declines to  define  the  behavior  which  passively  forces
       programs that must run under a variety of awks to use the more portable
       but less readable, double escape.

       POSIX  AWK  does  not  recognize  "/dev/std{in,out,err}".  Some systems
       provide an actual device for this, allowing AWKs which do not implement
       the feature directly to support it.

       POSIX AWK does not  recognize  \x  hex  escape  sequences  in  strings.
       Unlike  ANSI C, mmaawwkk limits the number of digits that follows \x to two
       as the current implementation only supports 8 bit characters.

       POSIX explicitly leaves the behavior of FFSS = "" undefined, and mentions
       splitting the record into characters as a possible interpretation,  but
       currently this use is not portable across implementations.

       Some  features  were  not  part  of the POSIX standard until long after
       their introduction in  mmaawwkk  and  other  implementations.   These  were
       published in IEEE 1003.1-2024 (The Open Group Base Specifications Issue
       8):

       +o   The  built-in  fffflluusshh first appeared in a 1993 AT&T awk released to
           netlib.  It was approved for the POSIX standard in 2012.

       +o   The built-in nneexxttffiillee first appeared in gawk in 1988,  was  adopted
           by BWK in 1996, and by mawk in 2012.  It was approved for the POSIX
           standard in 2012.

       +o   Aggregate deletion with ddeelleettee _a_r_r_a_y was approved in 2018.

   RRaannddoomm nnuummbbeerrss
       POSIX  does  not  prescribe a method for initializing random numbers at
       startup.

       In practice, most implementations do nothing special, which makes ssrraanndd
       and rraanndd follow the C runtime library, making the initial seed value 1.
       Some implementations (Solaris XPG4 and Tru64) return 0 from  the  first
       call  to ssrraanndd, although the results from rraanndd behave as if the initial
       seed is 1.  Other implementations return 1.

       While mmaawwkk can call ssrraanndd at startup with  no  parameter  (initializing
       random  numbers  from  the clock), this feature may be suppressed using
       conditional compilation.

   EExxtteennssiioonnss aaddddeedd ffoorr ccoommppaattiibbiilliittyy ffoorr GGAAWWKK aanndd BBWWKK
       MMkkttiimmee, ssttrrffttiimmee and ssyyssttiimmee are ggaawwkk extensions.

       The  "/dev/stdin"  feature  was  added  to  mmaawwkk   after   1.3.4,   for
       compatibility  with ggaawwkk and BWK awk.  The corresponding "-" (alias for
       /dev/stdin) was present in mmaawwkk 1.3.3.

       Interval  expressions,  e.g.,  a  range  _{_m_,_n_}  in   Extended   Regular
       Expressions  (EREs),  were  not  supported in awk (or even the original
       "nawk"):

       +o   Gawk provided this feature in 1991 (and later, in 1998, options for
           turning it off, for compatibility with "traditional awk").

       +o   Interval expressions, were introduced into _a_w_k regular  expressions
           in  IEEE  1003.1-2001  (also  known  as  Unix  03), along with some
           internationalization features.

       +o   Apple modified its copy of the original awk in April  2006,  making
           this version of awk support interval expressions.

           The  updated  source provides for compatibility with older "legacy"
           versions using an environment variable,  making  this  "Unix  2003"
           feature (perhaps meant as Unix 03) the default.

       +o   NetBSD  developers copied this change in January 2018, omitting the
           compatibility option, and then applied it to BWK awk.

       +o   The interval expression implementation in mmaawwkk is based on  changes
           proposed by James Parkinson in April 2016.

       MMaawwkk  also  recognizes  a  few  gawk-specific  command line options for
       script compatibility:

            ----hheellpp, ----ppoossiixx, --rr, ----rree--iinntteerrvvaall, ----ttrraaddiittiioonnaall, ----vveerrssiioonn

   SSuubbttllee DDiiffffeerreenncceess nnoott iinn PPOOSSIIXX oorr tthhee AAWWKK BBooookk
       Finally, here is how mmaawwkk handles exceptional cases  not  discussed  in
       the  AWK  book  or the POSIX draft.  It is unsafe to assume consistency
       across awks and safe to skip to the next section.

          +o   substr(s, i, n) returns the characters of s in the  intersection
              of the closed interval [1, length(s)] and the half-open interval
              [i,  i+n).  When this intersection is empty, the empty string is
              returned; so substr("ABC", 1, 0) = "" and substr("ABC", -4, 6) =
              "A".

          +o   Every string, including the  empty  string,  matches  the  empty
              string  at  the  front so, s ~ // and s ~ "", are always 1 as is
              match(s, //) and match(s, "").  The last two set RRLLEENNGGTTHH to 0.

          +o   index(s, t) is always the same as match(s, t1) where t1  is  the
              same  as  t with metacharacters escaped.  Hence consistency with
              match requires that index(s, "") always  returns  1.   Also  the
              condition,  index(s,t)  !=  0 if and only t is a substring of s,
              requires index("","") = 1.

          +o   If getline encounters end  of  file,  getline  var,  leaves  var
              unchanged.   Similarly,  on  entry  to  the EENNDD actions, $$00, the
              fields and NNFF have their value unaltered from the last record.

BBUUGGSS
       mmaawwkk implements pprriinnttff(()) and sspprriinnttff(()) using the C  library  functions,
       printf  and  sprintf,  so  full  ANSI  compatibility requires an ANSI C
       library.  In practice this means the h conversion qualifier may not  be
       available.

       Also mmaawwkk inherits any bugs or limitations of the library functions.

       Implementors  of  the  AWK  language  have  shown  a consistent lack of
       imagination when naming their programs.

EEXXAAMMPPLLEESS
       1. emulate cat.

            { print }

       2. emulate wc.

            { chars += length($0) + 1  # add one for the \n
              words += NF
            }

            END{ print NR, words, chars }

       3. count the number of unique "real words".

            BEGIN { FS = "[^A-Za-z]+" }

            { for(i = 1 ; i <= NF ; i++)  word[$i] = "" }

            END { delete word[""]
                  for ( i in word )  cnt++
                  print cnt
            }

       4. sum the second field of every record based on the first field.

            $1 ~ /credit|gain/ { sum += $2 }
            $1 ~ /debit|loss/  { sum -= $2 }

            END { print sum }

       5. sort a file, comparing as string

            { line[NR] = $0 "" }  # make sure of comparison type
                            # in case some lines look numeric

            END {  isort(line, NR)
              for(i = 1 ; i <= NR ; i++) print line[i]
            }

            #insertion sort of A[1..n]
            function isort( A, n,    i, j, hold)
            {
              for( i = 2 ; i <= n ; i++)
              {
                hold = A[j = i]
                while ( A[j-1] > hold )
                { j-- ; A[j+1] = A[j] }
                A[j] = hold
              }
              # sentinel A[0] = "" will be created if needed
            }


AAUUTTHHOORRSS
       Mike Brennan (brennan@whidbey.com).
       Thomas E. Dickey <dickey@invisible-island.net>.

SSEEEE AALLSSOO
       ggrreepp(1)

       Aho, Kernighan and Weinberger, _T_h_e _A_W_K _P_r_o_g_r_a_m_m_i_n_g  _L_a_n_g_u_a_g_e,  Addison-
       Wesley  Publishing, 1988, (the AWK book), defines the language, opening
       with a tutorial and advancing to many interesting programs  that  delve
       into  issues of software design and analysis relevant to programming in
       any language.

       _T_h_e _G_A_W_K _M_a_n_u_a_l, The Free Software Foundation, 1991, is a tutorial  and
       language  reference that does not attempt the depth of the AWK book and
       assumes the reader may be a novice  programmer.   The  section  on  AWK
       arrays is excellent.  It also discusses POSIX requirements for AWK.

       mmaawwkk--aarrrraayyss(7) discusses mmaawwkk's implementation of arrays.

       mmaawwkk--ccooddee(7) gives more information on the --WW dduummpp option.

       _a_w_k _- _p_a_t_t_e_r_n _s_c_a_n_n_i_n_g _a_n_d _p_r_o_c_e_s_s_i_n_g _l_a_n_g_u_a_g_e
       The Open Group Base Specifications Issue 8
       IEEE Std 1003.1-2024
       https://pubs.opengroup.org/onlinepubs/9799919799/utilities/awk.html

Version 1.3.4                     2026-03-02                           _M_A_W_K(1)