1 /* vi: set sw=4 ts=4: */
3 * Mini tail implementation for busybox
5 * Copyright (C) 2001 by Matt Kraai <kraai@alumni.carnegiemellon.edu>
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * General Public License for more details.
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
23 /* BB_AUDIT SUSv3 compliant (need fancy for -c) */
24 /* BB_AUDIT GNU compatible -c, -q, and -v options in 'fancy' configuration. */
25 /* http://www.opengroup.org/onlinepubs/007904975/utilities/tail.html */
27 /* Mar 16, 2003 Manuel Novoa III (mjn3@codepoet.org)
29 * Pretty much rewritten to fix numerous bugs and reduce realloc() calls.
30 * Bugs fixed (although I may have forgotten one or two... it was pretty bad)
31 * 1) mixing printf/write without fflush()ing stdout
32 * 2) no check that any open files are present
33 * 3) optstring had -q taking an arg
34 * 4) no error checking on write in some cases, and a warning even then
35 * 5) q and s interaction bug
36 * 6) no check for lseek error
37 * 7) lseek attempted when count==0 even if arg was +0 (from top)
49 static const struct suffix_mult tail_suffixes[] = {
58 = EXIT_SUCCESS /* If it is 0 (paranoid check), let bss initialize it. */
62 static void tail_xprint_header(const char *fmt, const char *filename)
64 /* If we get an output error, there is really no sense in continuing. */
65 if (dprintf(STDOUT_FILENO, fmt, filename) < 0) {
66 bb_perror_nomsg_and_die();
70 /* len should probably be size_t */
71 static void tail_xbb_full_write(const char *buf, size_t len)
73 /* If we get a write error, there is really no sense in continuing. */
74 if (bb_full_write(STDOUT_FILENO, buf, len) < 0) {
75 bb_perror_nomsg_and_die();
79 static ssize_t tail_read(int fd, char *buf, size_t count)
83 if ((r = safe_read(fd, buf, count)) < 0) {
84 bb_perror_msg("read");
85 status = EXIT_FAILURE;
91 static const char tail_opts[] =
93 #ifdef CONFIG_FEATURE_FANCY_TAIL
98 static const char header_fmt[] = "\n==> %s <==\n";
100 int tail_main(int argc, char **argv)
103 unsigned int sleep_period = 1;
106 int header_threshhold = 1;
114 int *fds, nfiles, nread, nwrite, seen, i, opt;
118 /* Allow legacy syntax of an initial numeric option without -n. */
119 if (argc >=2 && ((argv[1][0] == '+') || ((argv[1][0] == '-')
120 /* && (isdigit)(argv[1][1]) */
121 && (((unsigned int)(argv[1][1] - '0')) <= 9))))
128 while ((opt = getopt(argc, argv, tail_opts)) > 0) {
138 count = bb_xgetlarg10_sfx(optarg, tail_suffixes);
139 /* Note: Leading whitespace is an error trapped above. */
140 if (*optarg == '+') {
149 #ifdef CONFIG_FEATURE_FANCY_TAIL
151 header_threshhold = INT_MAX;
154 sleep_period =bb_xgetularg10_bnd(optarg, 0, UINT_MAX);
157 header_threshhold = 0;
165 /* open all the files */
166 fds = (int *)xmalloc(sizeof(int) * (argc - optind + 1));
171 if ((argc -= optind) == 0) {
174 if (!fstat(STDIN_FILENO, &statbuf) && S_ISFIFO(statbuf.st_mode)) {
178 *argv = (char *) bb_msg_standard_input;
183 if ((argv[i][0] == '-') && !argv[i][1]) {
185 fds[nfiles] = STDIN_FILENO;
186 } else if ((fds[nfiles] = open(argv[i], O_RDONLY)) < 0) {
187 bb_perror_msg("%s", argv[i]);
188 status = EXIT_FAILURE;
191 argv[nfiles] = argv[i];
193 } while (++i < argc);
196 bb_error_msg_and_die("no files");
199 tailbufsize = BUFSIZ;
202 if (from_top < count_bytes) { /* Each is 0 or 1, so true iff 0 < 1. */
203 /* Hence, !from_top && count_bytes */
204 if (tailbufsize < count) {
205 tailbufsize = count + BUFSIZ;
209 buf = tailbuf = xmalloc(tailbufsize);
211 fmt = header_fmt + 1; /* Skip header leading newline on first output. */
214 /* Be careful. It would be possible to optimize the count-bytes
215 * case if the file is seekable. If you do though, remember that
216 * starting file position may not be the beginning of the file.
217 * Beware of backing up too far. See example in wc.c.
219 if ((!(count|from_top)) && (lseek(fds[i], 0, SEEK_END) >= 0)) {
223 if (nfiles > header_threshhold) {
224 tail_xprint_header(fmt, argv[i]);
233 while ((nread = tail_read(fds[i], buf, tailbufsize-taillen)) > 0) {
238 nwrite -= (count - seen);
244 if ((*s++ == '\n') && (++seen == count)) {
250 tail_xbb_full_write(buf + nread - nwrite, nwrite);
254 if (taillen > count) {
255 memmove(tailbuf, tailbuf + taillen - count, count);
264 if (buf[k] == '\n') {
269 if (newline + nbuf < count) {
275 if (buf[nread-1] != '\n') {
279 k = newline + nbuf + extra - count;
288 taillen += nread - (s - tailbuf);
289 memmove(tailbuf, s, taillen);
290 newline = count - extra;
292 if (tailbufsize < taillen + BUFSIZ) {
293 tailbufsize = taillen + BUFSIZ;
294 tailbuf = xrealloc(tailbuf, tailbufsize);
297 buf = tailbuf + taillen;
302 tail_xbb_full_write(tailbuf, taillen);
306 } while (++i < nfiles);
308 buf = xrealloc(tailbuf, BUFSIZ);
316 if (nfiles > header_threshhold) {
319 while ((nread = tail_read(fds[i], buf, sizeof(buf))) > 0) {
321 tail_xprint_header(fmt, argv[i]);
324 tail_xbb_full_write(buf, nread);
326 } while (++i < nfiles);