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/* tailf.c -- tail a log file and then follow it
* Created: Tue Jan 9 15:49:21 1996 by faith@acm.org
* Copyright 1996, 2003 Rickard E. Faith (faith@acm.org)
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*
* less -F and tail -f cause a disk access every five seconds. This
* program avoids this problem by waiting for the file size to change.
* Hence, the file is not accessed, and the access time does not need to be
* flushed back to disk. This is sort of a "stealth" tail.
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <malloc.h>
#include <errno.h>
#include <string.h>
#include <sys/stat.h>
#include <ctype.h>
#include "errs.h"
#include "nls.h"
#define DEFAULT_LINES 10
static size_t filesize(const char *filename)
{
struct stat sb;
if (!stat(filename, &sb)) return sb.st_size;
return 0;
}
static void tailf(const char *filename, int lines)
{
char **buffer;
int head = 0;
int tail = 0;
FILE *str;
int i;
if (!(str = fopen(filename, "r"))) {
fprintf(stderr, _("Cannot open \"%s\" for read: %s\n"),
filename, strerror(errno));
exit(1);
}
buffer = malloc(lines * sizeof(*buffer));
for (i = 0; i < lines; i++) buffer[i] = malloc(BUFSIZ + 1);
while (fgets(buffer[tail], BUFSIZ, str)) {
if (++tail >= lines) {
tail = 0;
head = 1;
}
}
if (head) {
for (i = tail; i < lines; i++) fputs(buffer[i], stdout);
for (i = 0; i < tail; i++) fputs(buffer[i], stdout);
} else {
for (i = head; i < tail; i++) fputs(buffer[i], stdout);
}
fflush(stdout);
for (i = 0; i < lines; i++) free(buffer[i]);
free(buffer);
}
int main(int argc, char **argv)
{
char buffer[BUFSIZ];
size_t osize, nsize;
FILE *str;
const char *filename;
int count, wcount;
int lines = DEFAULT_LINES;
setlocale(LC_ALL, "");
bindtextdomain(PACKAGE, LOCALEDIR);
textdomain(PACKAGE);
argc--;
argv++;
for (; argc > 0 && argv[0][0] == '-'; argc--, argv++) {
if (!strcmp(*argv, "-n") || !strcmp(*argv, "--lines")) {
argc--;
argv++;
if (argc > 0 && (lines = atoi(argv[0])) <= 0)
errx(EXIT_FAILURE, _("Invalid number of lines"));
}
else if (isdigit(argv[0][1])) {
if ((lines = atoi(*argv + 1)) <= 0)
errx(EXIT_FAILURE, _("Invalid number of lines"));
}
else
errx(EXIT_FAILURE, _("Invalid option"));
}
if (argc != 1) {
fprintf(stderr, _("Usage: tailf [-n N | -N] logfile\n"));
exit(EXIT_FAILURE);
}
filename = argv[0];
tailf(filename, lines);
for (osize = filesize(filename);;) {
nsize = filesize(filename);
if (nsize != osize) {
if (!(str = fopen(filename, "r"))) {
fprintf(stderr, _("Cannot open \"%s\" for read: %s\n"),
filename, strerror(errno));
exit(1);
}
if (!fseek(str, osize, SEEK_SET))
while ((count = fread(buffer, 1, sizeof(buffer), str)) > 0) {
wcount = fwrite(buffer, 1, count, stdout);
if (wcount != count)
fprintf (stderr, _("Incomplete write to \"%s\" (written %d, expected %d)\n"),
filename, wcount, count);
}
fflush(stdout);
fclose(str);
osize = nsize;
}
usleep(250000); /* 250mS */
}
return 0;
}
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