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 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
10 /* BB_AUDIT SUSv3 compliant (need fancy for -c) */
11 /* BB_AUDIT GNU compatible -c, -q, and -v options in 'fancy' configuration. */
12 /* http://www.opengroup.org/onlinepubs/007904975/utilities/tail.html */
14 /* Mar 16, 2003 Manuel Novoa III (mjn3@codepoet.org)
16 * Pretty much rewritten to fix numerous bugs and reduce realloc() calls.
17 * Bugs fixed (although I may have forgotten one or two... it was pretty bad)
18 * 1) mixing printf/write without fflush()ing stdout
19 * 2) no check that any open files are present
20 * 3) optstring had -q taking an arg
21 * 4) no error checking on write in some cases, and a warning even then
22 * 5) q and s interaction bug
23 * 6) no check for lseek error
24 * 7) lseek attempted when count==0 even if arg was +0 (from top)
29 static const struct suffix_mult tail_suffixes[] = {
38 static void tail_xprint_header(const char *fmt, const char *filename)
40 if (fdprintf(STDOUT_FILENO, fmt, filename) < 0)
41 bb_perror_nomsg_and_die();
44 static ssize_t tail_read(int fd, char *buf, size_t count)
50 end = current = lseek(fd, 0, SEEK_CUR);
51 if (!fstat(fd, &sbuf))
53 lseek(fd, end < current ? 0 : current, SEEK_SET);
54 r = safe_read(fd, buf, count);
56 bb_perror_msg(bb_msg_read_error);
57 status = EXIT_FAILURE;
63 static const char header_fmt[] = "\n==> %s <==\n";
65 int tail_main(int argc, char **argv)
68 unsigned sleep_period = 1;
70 int header_threshhold = 1;
71 const char *str_c, *str_n, *str_s;
77 int nfiles, nread, nwrite, seen, i, opt;
83 void eat_num(const char *p) {
85 else if (*p == '+') { p++; from_top = 1; }
86 count = xatou_sfx(p, tail_suffixes);
90 #if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_TAIL
91 /* Allow legacy syntax of an initial numeric option without -n. */
92 if (argc >= 2 && (argv[1][0] == '+' || argv[1][0] == '-')
93 && isdigit(argv[1][1])
101 opt = getopt32(argc, argv, "fc:n:" USE_FEATURE_FANCY_TAIL("qs:v"), &str_c, &str_n, &str_s);
102 #define FOLLOW (opt & 0x1)
103 #define COUNT_BYTES (opt & 0x2)
104 //if (opt & 0x1) // -f
105 if (opt & 0x2) eat_num(str_c); // -c
106 if (opt & 0x4) eat_num(str_n); // -n
107 #if ENABLE_FEATURE_FANCY_TAIL
108 if (opt & 0x8) header_threshhold = INT_MAX; // -q
109 if (opt & 0x10) sleep_period = xatou(str_s); // -s
110 if (opt & 0x20) header_threshhold = 0; // -v
115 /* open all the files */
116 fds = xmalloc(sizeof(int) * (argc + 1));
121 if (!fstat(STDIN_FILENO, &statbuf) && S_ISFIFO(statbuf.st_mode)) {
122 opt &= ~1; /* clear FOLLOW */
124 *argv = (char *) bb_msg_standard_input;
129 if (NOT_LONE_DASH(argv[i])) {
130 fds[nfiles] = open(argv[i], O_RDONLY);
131 if (fds[nfiles] < 0) {
132 bb_perror_msg("%s", argv[i]);
133 status = EXIT_FAILURE;
138 fds[nfiles] = STDIN_FILENO;
140 argv[nfiles] = argv[i];
142 } while (++i < argc);
145 bb_error_msg_and_die("no files");
147 tailbufsize = BUFSIZ;
150 if (!from_top && COUNT_BYTES) {
151 if (tailbufsize < count) {
152 tailbufsize = count + BUFSIZ;
156 buf = tailbuf = xmalloc(tailbufsize);
158 fmt = header_fmt + 1; /* Skip header leading newline on first output. */
161 /* Be careful. It would be possible to optimize the count-bytes
162 * case if the file is seekable. If you do though, remember that
163 * starting file position may not be the beginning of the file.
164 * Beware of backing up too far. See example in wc.c.
166 if (!(count | from_top) && lseek(fds[i], 0, SEEK_END) >= 0) {
170 if (nfiles > header_threshhold) {
171 tail_xprint_header(fmt, argv[i]);
180 while ((nread = tail_read(fds[i], buf, tailbufsize-taillen)) > 0) {
185 nwrite -= (count - seen);
191 if (*s++ == '\n' && ++seen == count) {
197 xwrite(STDOUT_FILENO, buf + nread - nwrite, nwrite);
201 if (taillen > count) {
202 memmove(tailbuf, tailbuf + taillen - count, count);
211 if (buf[k] == '\n') {
216 if (newline + nbuf < count) {
222 if (buf[nread-1] != '\n') {
226 k = newline + nbuf + extra - count;
235 taillen += nread - (s - tailbuf);
236 memmove(tailbuf, s, taillen);
237 newline = count - extra;
239 if (tailbufsize < taillen + BUFSIZ) {
240 tailbufsize = taillen + BUFSIZ;
241 tailbuf = xrealloc(tailbuf, tailbufsize);
244 buf = tailbuf + taillen;
249 xwrite(STDOUT_FILENO, tailbuf, taillen);
253 } while (++i < nfiles);
255 buf = xrealloc(tailbuf, BUFSIZ);
259 if (FOLLOW) while (1) {
263 if (nfiles > header_threshhold) {
266 while ((nread = tail_read(fds[i], buf, sizeof(buf))) > 0) {
268 tail_xprint_header(fmt, argv[i]);
271 xwrite(STDOUT_FILENO, buf, nread);
273 } while (++i < nfiles);