busybox/coreutils/tail.c

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/* vi: set sw=4 ts=4: */
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/*
* Mini tail implementation for busybox
*
* Copyright (C) 2001 by Matt Kraai <kraai@alumni.carnegiemellon.edu>
*
* 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 2 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, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
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/* BB_AUDIT SUSv3 compliant (need fancy for -c) */
/* BB_AUDIT GNU compatible -c, -q, and -v options in 'fancy' configuration. */
/* http://www.opengroup.org/onlinepubs/007904975/utilities/tail.html */
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/* Mar 16, 2003 Manuel Novoa III (mjn3@codepoet.org)
*
* Pretty much rewritten to fix numerous bugs and reduce realloc() calls.
* Bugs fixed (although I may have forgotten one or two... it was pretty bad)
* 1) mixing printf/write without fflush()ing stdout
* 2) no check that any open files are present
* 3) optstring had -q taking an arg
* 4) no error checking on write in some cases, and a warning even then
* 5) q and s interaction bug
* 6) no check for lseek error
* 7) lseek attempted when count==0 even if arg was +0 (from top)
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <unistd.h>
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#include <fcntl.h>
#include <sys/stat.h>
#include "busybox.h"
static const struct suffix_mult tail_suffixes[] = {
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{ "b", 512 },
{ "k", 1024 },
{ "m", 1048576 },
{ NULL, 0 }
};
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static int status
#if EXIT_SUCCESS != 0
= EXIT_SUCCESS /* If it is 0 (paranoid check), let bss initialize it. */
#endif
;
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static void tail_xprint_header(const char *fmt, const char *filename)
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{
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/* If we get an output error, there is really no sense in continuing. */
if (dprintf(STDOUT_FILENO, fmt, filename) < 0) {
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bb_perror_nomsg_and_die();
}
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}
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/* len should probably be size_t */
static void tail_xbb_full_write(const char *buf, size_t len)
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{
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/* If we get a write error, there is really no sense in continuing. */
if (bb_full_write(STDOUT_FILENO, buf, len) < 0) {
bb_perror_nomsg_and_die();
}
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}
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static ssize_t tail_read(int fd, char *buf, size_t count)
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{
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ssize_t r;
off_t current,end;
struct stat sbuf;
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end = current = lseek(fd, 0, SEEK_CUR);
if (!fstat(fd, &sbuf))
end = sbuf.st_size;
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lseek(fd, end < current ? 0 : current, SEEK_SET);
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if ((r = safe_read(fd, buf, count)) < 0) {
bb_perror_msg("read");
status = EXIT_FAILURE;
}
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return r;
}
static const char tail_opts[] =
"fn:c:"
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#ifdef CONFIG_FEATURE_FANCY_TAIL
"qs:v"
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#endif
;
static const char header_fmt[] = "\n==> %s <==\n";
int tail_main(int argc, char **argv)
{
long count = 10;
unsigned int sleep_period = 1;
int from_top = 0;
int follow = 0;
int header_threshhold = 1;
int count_bytes = 0;
char *tailbuf;
size_t tailbufsize;
int taillen = 0;
int newline = 0;
int *fds, nfiles, nread, nwrite, seen, i, opt;
char *s, *buf;
const char *fmt;
/* Allow legacy syntax of an initial numeric option without -n. */
if (argc >=2 && ((argv[1][0] == '+') || ((argv[1][0] == '-')
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/* && (isdigit)(argv[1][1]) */
&& (((unsigned int)(argv[1][1] - '0')) <= 9))))
{
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optind = 2;
optarg = argv[1];
goto GET_COUNT;
}
while ((opt = getopt(argc, argv, tail_opts)) > 0) {
switch (opt) {
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case 'f':
follow = 1;
break;
case 'c':
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count_bytes = 1;
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/* FALLS THROUGH */
case 'n':
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GET_COUNT:
count = bb_xgetlarg10_sfx(optarg, tail_suffixes);
/* Note: Leading whitespace is an error trapped above. */
if (*optarg == '+') {
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from_top = 1;
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} else {
from_top = 0;
}
if (count < 0) {
count = -count;
}
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break;
#ifdef CONFIG_FEATURE_FANCY_TAIL
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case 'q':
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header_threshhold = INT_MAX;
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break;
case 's':
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sleep_period =bb_xgetularg10_bnd(optarg, 0, UINT_MAX);
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break;
case 'v':
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header_threshhold = 0;
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break;
#endif
default:
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bb_show_usage();
}
}
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/* open all the files */
fds = (int *)xmalloc(sizeof(int) * (argc - optind + 1));
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argv += optind;
nfiles = i = 0;
if ((argc -= optind) == 0) {
struct stat statbuf;
if (!fstat(STDIN_FILENO, &statbuf) && S_ISFIFO(statbuf.st_mode)) {
follow = 0;
}
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/* --argv; */
*argv = (char *) bb_msg_standard_input;
goto DO_STDIN;
}
do {
if ((argv[i][0] == '-') && !argv[i][1]) {
DO_STDIN:
fds[nfiles] = STDIN_FILENO;
} else if ((fds[nfiles] = open(argv[i], O_RDONLY)) < 0) {
bb_perror_msg("%s", argv[i]);
status = EXIT_FAILURE;
continue;
}
argv[nfiles] = argv[i];
++nfiles;
} while (++i < argc);
if (!nfiles) {
bb_error_msg_and_die("no files");
}
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tailbufsize = BUFSIZ;
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/* tail the files */
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if (from_top < count_bytes) { /* Each is 0 or 1, so true iff 0 < 1. */
/* Hence, !from_top && count_bytes */
if (tailbufsize < count) {
tailbufsize = count + BUFSIZ;
}
}
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buf = tailbuf = xmalloc(tailbufsize);
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fmt = header_fmt + 1; /* Skip header leading newline on first output. */
i = 0;
do {
/* Be careful. It would be possible to optimize the count-bytes
* case if the file is seekable. If you do though, remember that
* starting file position may not be the beginning of the file.
* Beware of backing up too far. See example in wc.c.
*/
if ((!(count|from_top)) && (lseek(fds[i], 0, SEEK_END) >= 0)) {
continue;
}
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if (nfiles > header_threshhold) {
tail_xprint_header(fmt, argv[i]);
fmt = header_fmt;
}
buf = tailbuf;
taillen = 0;
seen = 1;
newline = 0;
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while ((nread = tail_read(fds[i], buf, tailbufsize-taillen)) > 0) {
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if (from_top) {
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nwrite = nread;
if (seen < count) {
if (count_bytes) {
nwrite -= (count - seen);
seen = count;
} else {
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s = buf;
do {
--nwrite;
if ((*s++ == '\n') && (++seen == count)) {
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break;
}
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} while (nwrite);
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}
}
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tail_xbb_full_write(buf + nread - nwrite, nwrite);
} else if (count) {
if (count_bytes) {
taillen += nread;
if (taillen > count) {
memmove(tailbuf, tailbuf + taillen - count, count);
taillen = count;
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}
} else {
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int k = nread;
int nbuf = 0;
while (k) {
--k;
if (buf[k] == '\n') {
++nbuf;
}
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}
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if (newline + nbuf < count) {
newline += nbuf;
taillen += nread;
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} else {
int extra = 0;
if (buf[nread-1] != '\n') {
extra = 1;
}
k = newline + nbuf + extra - count;
s = tailbuf;
while (k) {
if (*s == '\n') {
--k;
}
++s;
}
taillen += nread - (s - tailbuf);
memmove(tailbuf, s, taillen);
newline = count - extra;
}
if (tailbufsize < taillen + BUFSIZ) {
tailbufsize = taillen + BUFSIZ;
tailbuf = xrealloc(tailbuf, tailbufsize);
}
}
buf = tailbuf + taillen;
}
}
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if (!from_top) {
tail_xbb_full_write(tailbuf, taillen);
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}
taillen = 0;
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} while (++i < nfiles);
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buf = xrealloc(tailbuf, BUFSIZ);
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fmt = NULL;
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while (follow) {
sleep(sleep_period);
i = 0;
do {
if (nfiles > header_threshhold) {
fmt = header_fmt;
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}
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while ((nread = tail_read(fds[i], buf, sizeof(buf))) > 0) {
if (fmt) {
tail_xprint_header(fmt, argv[i]);
fmt = NULL;
}
tail_xbb_full_write(buf, nread);
}
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} while (++i < nfiles);
}
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return status;
}