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;
107 #ifdef CONFIG_FEATURE_FANCY_TAIL
116 int *fds, nfiles, nread, nwrite, seen, i, opt;
120 /* Allow legacy syntax of an initial numeric option without -n. */
121 if ((argv[1][0] == '+')
122 || ((argv[1][0] == '-')
123 /* && (isdigit)(argv[1][1]) */
124 && (((unsigned int)(argv[1][1] - '0')) <= 9))
131 while ((opt = getopt(argc, argv, tail_opts)) > 0) {
136 #ifdef CONFIG_FEATURE_FANCY_TAIL
143 count = bb_xgetlarg10_sfx(optarg, tail_suffixes);
144 /* Note: Leading whitespace is an error trapped above. */
145 if (*optarg == '+') {
154 #ifdef CONFIG_FEATURE_FANCY_TAIL
156 header_threshhold = INT_MAX;
159 sleep_period =bb_xgetularg10_bnd(optarg, 0, UINT_MAX);
162 header_threshhold = 0;
170 /* open all the files */
171 fds = (int *)xmalloc(sizeof(int) * (argc - optind + 1));
176 if ((argc -= optind) == 0) {
179 if (!fstat(STDIN_FILENO, &statbuf) && S_ISFIFO(statbuf.st_mode)) {
183 *argv = (char *) bb_msg_standard_input;
188 if ((argv[i][0] == '-') && !argv[i][1]) {
190 fds[nfiles] = STDIN_FILENO;
191 } else if ((fds[nfiles] = open(argv[i], O_RDONLY)) < 0) {
192 bb_perror_msg("%s", argv[i]);
193 status = EXIT_FAILURE;
196 argv[nfiles] = argv[i];
198 } while (++i < argc);
201 bb_error_msg_and_die("no files");
204 tailbufsize = BUFSIZ;
205 #ifdef CONFIG_FEATURE_FANCY_TAIL
207 if (from_top < count_bytes) { /* Each is 0 or 1, so true iff 0 < 1. */
208 /* Hence, !from_top && count_bytes */
209 if (tailbufsize < count) {
210 tailbufsize = count + BUFSIZ;
214 buf = tailbuf = xmalloc(tailbufsize);
216 fmt = header_fmt + 1; /* Skip header leading newline on first output. */
219 /* Be careful. It would be possible to optimize the count-bytes
220 * case if the file is seekable. If you do though, remember that
221 * starting file position may not be the beginning of the file.
222 * Beware of backing up too far. See example in wc.c.
224 if ((!(count|from_top)) && (lseek(fds[i], 0, SEEK_END) >= 0)) {
228 if (nfiles > header_threshhold) {
229 tail_xprint_header(fmt, argv[i]);
237 while ((nread = tail_read(fds[i], buf, tailbufsize-taillen)) > 0) {
241 #ifdef CONFIG_FEATURE_FANCY_TAIL
243 nwrite -= (count - seen);
251 if ((*s++ == '\n') && (++seen == count)) {
257 tail_xbb_full_write(buf + nread - nwrite, nwrite);
259 #ifdef CONFIG_FEATURE_FANCY_TAIL
262 if (taillen > count) {
263 memmove(tailbuf, tailbuf + taillen - count, count);
274 if (buf[k] == '\n') {
279 if (newline + nbuf < count) {
285 if (buf[nread-1] != '\n') {
289 k = newline + nbuf + extra - count;
298 taillen += nread - (s - tailbuf);
299 memmove(tailbuf, s, taillen);
300 newline = count - extra;
302 if (tailbufsize < taillen + BUFSIZ) {
303 tailbufsize = taillen + BUFSIZ;
304 tailbuf = xrealloc(tailbuf, tailbufsize);
307 buf = tailbuf + taillen;
312 tail_xbb_full_write(tailbuf, taillen);
316 } while (++i < nfiles);
318 buf = xrealloc(tailbuf, BUFSIZ);
326 if (nfiles > header_threshhold) {
329 while ((nread = tail_read(fds[i], buf, sizeof(buf))) > 0) {
331 tail_xprint_header(fmt, argv[i]);
334 tail_xbb_full_write(buf, nread);
336 } while (++i < nfiles);