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/*
** TAIL.C
** ----------------------------------------------------------------------
** Display the last n lines of a file (20 lines by default).
**
** Revision history
** ================
** Modified 19930604 by Ruurd Pels:
** - Increased default line numbers from 5 to 20
** - Made ANSI C conformant (I hope)
** - Added '-' support for commandline
** - Outputs header to stderr instead of stdout to leave it out when
** redirecting files
** - Fixed \r\r\n bug for MSDOS machines
**
** Modified 19861005 by Joe Huffman:
** - Utilize prototyping, fixed a bug, added (a few) comments and help.
**
** Written 19860204 by Joe Huffman.
**
** Not copyrighted.
*/
#include <stdio.h>
#include <stdlib.h>
char head1[] = {"\n------- \""};
char head2[] = {" -------\n"};
FILE * fp;
int filenum;
int cc;
unsigned int linenum = 20;
unsigned int indx;
long int * tail;
/*
** Get the number of lines to display at the "tail" of each file from
** the command line.
*/
void getlinenum(int n, char * str[])
{
for (--n; n; --n)
{
++str;
if ((**str == '/') || (**str == '-'))
{
linenum = atoi(*(str) + 1);
if (linenum <= 0)
linenum = 20;
}
}
/* Because we save a pointer to the end of the PREVIOUS line */
linenum++;
}
/*
** Set the file pointer "fp" to "linenum - 1" lines before the end of
** the file.
*/
void gettail(void)
{
unsigned char outstr[15];
unsigned long int currline = 0L;
tail = (long int *)malloc(sizeof(*tail) * linenum);
if (!tail)
{
fputs("Insufficient memory.", stderr);
exit(1);
}
tail[0] = ftell(fp);
indx = 0;
for (cc = getc(fp); cc != EOF; cc = getc(fp))
{
if (cc == '\r')
{
++currline;
cc = getc(fp);
if (cc != '\n')
ungetc(cc, fp);
++indx;
indx %= linenum;
tail[indx] = ftell(fp);
}
else
{
if (cc == '\n')
{
++currline;
cc = getc(fp);
if (cc != '\r')
ungetc(cc, fp);
++indx;
indx %= linenum;
tail[indx] = ftell(fp);
}
}
}
fputs("\" ", stderr);
ltoa(currline, outstr, 10);
fputs(outstr, stderr);
fputs(" lines", stderr);
if (currline >= linenum - 1)
{
indx++;
indx %= linenum;
}
else indx = 0;
if (fseek(fp, tail[indx], 0) == -1)
{
fputs("\nFile seek error.", stderr);
exit(1);
}
free(tail);
}
/*
** Tell the user what the program is and how to use it.
*/
void help(void)
{
char *ptr;
static char help_str[] = "Usage:\n\nTAIL <filename> [filename] "
"[/n]\n\n<filename> - The name of a valid file, wildcards "
"accepted.\nn - Number of lines to print out, 20 "
"by default.";
for (ptr = &help_str[0]; *ptr; ptr++)
fputc(*ptr, stdout);
}
int main(int argc, char **argv)
{
if (argc <= 1)
{
help();
exit(1);
}
getlinenum(argc, argv);
for (filenum = 1; filenum < argc; ++filenum)
{
if (*argv[filenum] == '/')
continue;
fp = fopen(argv[filenum], "rb");
if (!fp)
{
fputs(head1, stderr);
fputs(argv[filenum], stderr);
fputs("\" not found.", stderr);
fputs(head2, stderr);
}
else
{
fputs(head1, stderr);
fputs(argv[filenum], stderr);
gettail();
fputs(head2, stderr);
for (cc = getc(fp); cc != EOF; cc = getc(fp))
{
#ifdef __MSDOS__
if (cc != '\r')
{
fputc(cc, stdout);
}
#else
fputc(cc, stdout);
#endif
}
fclose(fp);
}
}
return EXIT_SUCCESS;
}
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