1 | /* vi: set sw=4 ts=4: */
|
---|
2 | /*
|
---|
3 | * Mini tail implementation for busybox
|
---|
4 | *
|
---|
5 | * Copyright (C) 2001 by Matt Kraai <kraai@alumni.carnegiemellon.edu>
|
---|
6 | *
|
---|
7 | * Licensed under GPLv2 or later, see file LICENSE in this source tree.
|
---|
8 | */
|
---|
9 |
|
---|
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 */
|
---|
13 |
|
---|
14 | /* Mar 16, 2003 Manuel Novoa III (mjn3@codepoet.org)
|
---|
15 | *
|
---|
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)
|
---|
25 | */
|
---|
26 |
|
---|
27 | //kbuild:lib-$(CONFIG_TAIL) += tail.o
|
---|
28 |
|
---|
29 | //usage:#define tail_trivial_usage
|
---|
30 | //usage: "[OPTIONS] [FILE]..."
|
---|
31 | //usage:#define tail_full_usage "\n\n"
|
---|
32 | //usage: "Print last 10 lines of each FILE (or stdin) to stdout.\n"
|
---|
33 | //usage: "With more than one FILE, precede each with a filename header.\n"
|
---|
34 | //usage: "\n -f Print data as file grows"
|
---|
35 | //usage: "\n -c [+]N[kbm] Print last N bytes"
|
---|
36 | //usage: "\n -n N[kbm] Print last N lines"
|
---|
37 | //usage: "\n -n +N[kbm] Start on Nth line and print the rest"
|
---|
38 | //usage: IF_FEATURE_FANCY_TAIL(
|
---|
39 | //usage: "\n -q Never print headers"
|
---|
40 | //usage: "\n -s SECONDS Wait SECONDS between reads with -f"
|
---|
41 | //usage: "\n -v Always print headers"
|
---|
42 | //usage: "\n -F Same as -f, but keep retrying"
|
---|
43 | //usage: "\n"
|
---|
44 | //usage: "\nN may be suffixed by k (x1024), b (x512), or m (x1024^2)."
|
---|
45 | //usage: )
|
---|
46 | //usage:
|
---|
47 | //usage:#define tail_example_usage
|
---|
48 | //usage: "$ tail -n 1 /etc/resolv.conf\n"
|
---|
49 | //usage: "nameserver 10.0.0.1\n"
|
---|
50 |
|
---|
51 | #include "libbb.h"
|
---|
52 | #include "common_bufsiz.h"
|
---|
53 |
|
---|
54 | struct globals {
|
---|
55 | bool from_top;
|
---|
56 | bool exitcode;
|
---|
57 | } FIX_ALIASING;
|
---|
58 | #define G (*(struct globals*)bb_common_bufsiz1)
|
---|
59 | #define INIT_G() do { setup_common_bufsiz(); } while (0)
|
---|
60 |
|
---|
61 | static void tail_xprint_header(const char *fmt, const char *filename)
|
---|
62 | {
|
---|
63 | if (fdprintf(STDOUT_FILENO, fmt, filename) < 0)
|
---|
64 | bb_perror_nomsg_and_die();
|
---|
65 | }
|
---|
66 |
|
---|
67 | static ssize_t tail_read(int fd, char *buf, size_t count)
|
---|
68 | {
|
---|
69 | ssize_t r;
|
---|
70 |
|
---|
71 | r = full_read(fd, buf, count);
|
---|
72 | if (r < 0) {
|
---|
73 | bb_perror_msg(bb_msg_read_error);
|
---|
74 | G.exitcode = EXIT_FAILURE;
|
---|
75 | }
|
---|
76 |
|
---|
77 | return r;
|
---|
78 | }
|
---|
79 |
|
---|
80 | #define header_fmt_str "\n==> %s <==\n"
|
---|
81 |
|
---|
82 | static unsigned eat_num(const char *p)
|
---|
83 | {
|
---|
84 | if (*p == '-')
|
---|
85 | p++;
|
---|
86 | else if (*p == '+') {
|
---|
87 | p++;
|
---|
88 | G.from_top = 1;
|
---|
89 | }
|
---|
90 | return xatou_sfx(p, bkm_suffixes);
|
---|
91 | }
|
---|
92 |
|
---|
93 | int tail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
|
---|
94 | int tail_main(int argc, char **argv)
|
---|
95 | {
|
---|
96 | unsigned count = 10;
|
---|
97 | unsigned sleep_period = 1;
|
---|
98 | const char *str_c, *str_n;
|
---|
99 |
|
---|
100 | char *tailbuf;
|
---|
101 | size_t tailbufsize;
|
---|
102 | unsigned header_threshhold = 1;
|
---|
103 | unsigned nfiles;
|
---|
104 | int i, opt;
|
---|
105 |
|
---|
106 | int *fds;
|
---|
107 | const char *fmt;
|
---|
108 | int prev_fd;
|
---|
109 |
|
---|
110 | INIT_G();
|
---|
111 |
|
---|
112 | #if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_TAIL
|
---|
113 | /* Allow legacy syntax of an initial numeric option without -n. */
|
---|
114 | if (argv[1] && (argv[1][0] == '+' || argv[1][0] == '-')
|
---|
115 | && isdigit(argv[1][1])
|
---|
116 | ) {
|
---|
117 | count = eat_num(argv[1]);
|
---|
118 | argv++;
|
---|
119 | argc--;
|
---|
120 | }
|
---|
121 | #endif
|
---|
122 |
|
---|
123 | /* -s NUM, -F imlies -f */
|
---|
124 | IF_FEATURE_FANCY_TAIL(opt_complementary = "s+:Ff";)
|
---|
125 | opt = getopt32(argv, "fc:n:" IF_FEATURE_FANCY_TAIL("qs:vF"),
|
---|
126 | &str_c, &str_n IF_FEATURE_FANCY_TAIL(,&sleep_period));
|
---|
127 | #define FOLLOW (opt & 0x1)
|
---|
128 | #define COUNT_BYTES (opt & 0x2)
|
---|
129 | //if (opt & 0x1) // -f
|
---|
130 | if (opt & 0x2) count = eat_num(str_c); // -c
|
---|
131 | if (opt & 0x4) count = eat_num(str_n); // -n
|
---|
132 | #if ENABLE_FEATURE_FANCY_TAIL
|
---|
133 | /* q: make it impossible for nfiles to be > header_threshhold */
|
---|
134 | if (opt & 0x8) header_threshhold = UINT_MAX; // -q
|
---|
135 | //if (opt & 0x10) // -s
|
---|
136 | if (opt & 0x20) header_threshhold = 0; // -v
|
---|
137 | # define FOLLOW_RETRY (opt & 0x40)
|
---|
138 | #else
|
---|
139 | # define FOLLOW_RETRY 0
|
---|
140 | #endif
|
---|
141 | argc -= optind;
|
---|
142 | argv += optind;
|
---|
143 |
|
---|
144 | /* open all the files */
|
---|
145 | fds = xmalloc(sizeof(fds[0]) * (argc + 1));
|
---|
146 | if (!argv[0]) {
|
---|
147 | struct stat statbuf;
|
---|
148 |
|
---|
149 | if (fstat(STDIN_FILENO, &statbuf) == 0
|
---|
150 | && S_ISFIFO(statbuf.st_mode)
|
---|
151 | ) {
|
---|
152 | opt &= ~1; /* clear FOLLOW */
|
---|
153 | }
|
---|
154 | argv[0] = (char *) bb_msg_standard_input;
|
---|
155 | }
|
---|
156 | nfiles = i = 0;
|
---|
157 | do {
|
---|
158 | int fd = open_or_warn_stdin(argv[i]);
|
---|
159 | if (fd < 0 && !FOLLOW_RETRY) {
|
---|
160 | G.exitcode = EXIT_FAILURE;
|
---|
161 | continue;
|
---|
162 | }
|
---|
163 | fds[nfiles] = fd;
|
---|
164 | argv[nfiles++] = argv[i];
|
---|
165 | } while (++i < argc);
|
---|
166 |
|
---|
167 | if (!nfiles)
|
---|
168 | bb_error_msg_and_die("no files");
|
---|
169 |
|
---|
170 | /* prepare the buffer */
|
---|
171 | tailbufsize = BUFSIZ;
|
---|
172 | if (!G.from_top && COUNT_BYTES) {
|
---|
173 | if (tailbufsize < count + BUFSIZ) {
|
---|
174 | tailbufsize = count + BUFSIZ;
|
---|
175 | }
|
---|
176 | }
|
---|
177 | /* tail -c1024m REGULAR_FILE doesn't really need 1G mem block.
|
---|
178 | * (In fact, it doesn't need ANY memory). So delay allocation.
|
---|
179 | */
|
---|
180 | tailbuf = NULL;
|
---|
181 |
|
---|
182 | /* tail the files */
|
---|
183 |
|
---|
184 | fmt = header_fmt_str + 1; /* skip leading newline in the header on the first output */
|
---|
185 | i = 0;
|
---|
186 | do {
|
---|
187 | char *buf;
|
---|
188 | int taillen;
|
---|
189 | int newlines_seen;
|
---|
190 | unsigned seen;
|
---|
191 | int nread;
|
---|
192 | int fd = fds[i];
|
---|
193 |
|
---|
194 | if (ENABLE_FEATURE_FANCY_TAIL && fd < 0)
|
---|
195 | continue; /* may happen with -F */
|
---|
196 |
|
---|
197 | if (nfiles > header_threshhold) {
|
---|
198 | tail_xprint_header(fmt, argv[i]);
|
---|
199 | fmt = header_fmt_str;
|
---|
200 | }
|
---|
201 |
|
---|
202 | if (!G.from_top) {
|
---|
203 | off_t current = lseek(fd, 0, SEEK_END);
|
---|
204 | if (current > 0) {
|
---|
205 | unsigned off;
|
---|
206 | if (COUNT_BYTES) {
|
---|
207 | /* Optimizing count-bytes case if the file is seekable.
|
---|
208 | * Beware of backing up too far.
|
---|
209 | * Also we exclude files with size 0 (because of /proc/xxx) */
|
---|
210 | if (count == 0)
|
---|
211 | continue; /* showing zero bytes is easy :) */
|
---|
212 | current -= count;
|
---|
213 | if (current < 0)
|
---|
214 | current = 0;
|
---|
215 | xlseek(fd, current, SEEK_SET);
|
---|
216 | bb_copyfd_size(fd, STDOUT_FILENO, count);
|
---|
217 | continue;
|
---|
218 | }
|
---|
219 | #if 1 /* This is technically incorrect for *LONG* strings, but very useful */
|
---|
220 | /* Optimizing count-lines case if the file is seekable.
|
---|
221 | * We assume the lines are <64k.
|
---|
222 | * (Users complain that tail takes too long
|
---|
223 | * on multi-gigabyte files) */
|
---|
224 | off = (count | 0xf); /* for small counts, be more paranoid */
|
---|
225 | if (off > (INT_MAX / (64*1024)))
|
---|
226 | off = (INT_MAX / (64*1024));
|
---|
227 | current -= off * (64*1024);
|
---|
228 | if (current < 0)
|
---|
229 | current = 0;
|
---|
230 | xlseek(fd, current, SEEK_SET);
|
---|
231 | #endif
|
---|
232 | }
|
---|
233 | }
|
---|
234 |
|
---|
235 | if (!tailbuf)
|
---|
236 | tailbuf = xmalloc(tailbufsize);
|
---|
237 |
|
---|
238 | buf = tailbuf;
|
---|
239 | taillen = 0;
|
---|
240 | /* "We saw 1st line/byte".
|
---|
241 | * Used only by +N code ("start from Nth", 1-based): */
|
---|
242 | seen = 1;
|
---|
243 | newlines_seen = 0;
|
---|
244 | while ((nread = tail_read(fd, buf, tailbufsize - taillen)) > 0) {
|
---|
245 | if (G.from_top) {
|
---|
246 | int nwrite = nread;
|
---|
247 | if (seen < count) {
|
---|
248 | /* We need to skip a few more bytes/lines */
|
---|
249 | if (COUNT_BYTES) {
|
---|
250 | nwrite -= (count - seen);
|
---|
251 | seen += nread;
|
---|
252 | } else {
|
---|
253 | char *s = buf;
|
---|
254 | do {
|
---|
255 | --nwrite;
|
---|
256 | if (*s++ == '\n' && ++seen == count) {
|
---|
257 | break;
|
---|
258 | }
|
---|
259 | } while (nwrite);
|
---|
260 | }
|
---|
261 | }
|
---|
262 | if (nwrite > 0)
|
---|
263 | xwrite(STDOUT_FILENO, buf + nread - nwrite, nwrite);
|
---|
264 | } else if (count) {
|
---|
265 | if (COUNT_BYTES) {
|
---|
266 | taillen += nread;
|
---|
267 | if (taillen > (int)count) {
|
---|
268 | memmove(tailbuf, tailbuf + taillen - count, count);
|
---|
269 | taillen = count;
|
---|
270 | }
|
---|
271 | } else {
|
---|
272 | int k = nread;
|
---|
273 | int newlines_in_buf = 0;
|
---|
274 |
|
---|
275 | do { /* count '\n' in last read */
|
---|
276 | k--;
|
---|
277 | if (buf[k] == '\n') {
|
---|
278 | newlines_in_buf++;
|
---|
279 | }
|
---|
280 | } while (k);
|
---|
281 |
|
---|
282 | if (newlines_seen + newlines_in_buf < (int)count) {
|
---|
283 | newlines_seen += newlines_in_buf;
|
---|
284 | taillen += nread;
|
---|
285 | } else {
|
---|
286 | int extra = (buf[nread-1] != '\n');
|
---|
287 | char *s;
|
---|
288 |
|
---|
289 | k = newlines_seen + newlines_in_buf + extra - count;
|
---|
290 | s = tailbuf;
|
---|
291 | while (k) {
|
---|
292 | if (*s == '\n') {
|
---|
293 | k--;
|
---|
294 | }
|
---|
295 | s++;
|
---|
296 | }
|
---|
297 | taillen += nread - (s - tailbuf);
|
---|
298 | memmove(tailbuf, s, taillen);
|
---|
299 | newlines_seen = count - extra;
|
---|
300 | }
|
---|
301 | if (tailbufsize < (size_t)taillen + BUFSIZ) {
|
---|
302 | tailbufsize = taillen + BUFSIZ;
|
---|
303 | tailbuf = xrealloc(tailbuf, tailbufsize);
|
---|
304 | }
|
---|
305 | }
|
---|
306 | buf = tailbuf + taillen;
|
---|
307 | }
|
---|
308 | } /* while (tail_read() > 0) */
|
---|
309 | if (!G.from_top) {
|
---|
310 | xwrite(STDOUT_FILENO, tailbuf, taillen);
|
---|
311 | }
|
---|
312 | } while (++i < nfiles);
|
---|
313 | prev_fd = fds[i-1];
|
---|
314 |
|
---|
315 | tailbuf = xrealloc(tailbuf, BUFSIZ);
|
---|
316 |
|
---|
317 | fmt = NULL;
|
---|
318 |
|
---|
319 | if (FOLLOW) while (1) {
|
---|
320 | sleep(sleep_period);
|
---|
321 |
|
---|
322 | i = 0;
|
---|
323 | do {
|
---|
324 | int nread;
|
---|
325 | const char *filename = argv[i];
|
---|
326 | int fd = fds[i];
|
---|
327 |
|
---|
328 | if (FOLLOW_RETRY) {
|
---|
329 | struct stat sbuf, fsbuf;
|
---|
330 |
|
---|
331 | if (fd < 0
|
---|
332 | || fstat(fd, &fsbuf) < 0
|
---|
333 | || stat(filename, &sbuf) < 0
|
---|
334 | || fsbuf.st_dev != sbuf.st_dev
|
---|
335 | || fsbuf.st_ino != sbuf.st_ino
|
---|
336 | ) {
|
---|
337 | int new_fd;
|
---|
338 |
|
---|
339 | if (fd >= 0)
|
---|
340 | close(fd);
|
---|
341 | new_fd = open(filename, O_RDONLY);
|
---|
342 | if (new_fd >= 0) {
|
---|
343 | bb_error_msg("%s has %s; following end of new file",
|
---|
344 | filename, (fd < 0) ? "appeared" : "been replaced"
|
---|
345 | );
|
---|
346 | } else if (fd >= 0) {
|
---|
347 | bb_perror_msg("%s has become inaccessible", filename);
|
---|
348 | }
|
---|
349 | fds[i] = fd = new_fd;
|
---|
350 | }
|
---|
351 | }
|
---|
352 | if (ENABLE_FEATURE_FANCY_TAIL && fd < 0)
|
---|
353 | continue;
|
---|
354 | if (nfiles > header_threshhold) {
|
---|
355 | fmt = header_fmt_str;
|
---|
356 | }
|
---|
357 | for (;;) {
|
---|
358 | /* tail -f keeps following files even if they are truncated */
|
---|
359 | struct stat sbuf;
|
---|
360 | /* /proc files report zero st_size, don't lseek them */
|
---|
361 | if (fstat(fd, &sbuf) == 0 && sbuf.st_size > 0) {
|
---|
362 | off_t current = lseek(fd, 0, SEEK_CUR);
|
---|
363 | if (sbuf.st_size < current)
|
---|
364 | xlseek(fd, 0, SEEK_SET);
|
---|
365 | }
|
---|
366 |
|
---|
367 | nread = tail_read(fd, tailbuf, BUFSIZ);
|
---|
368 | if (nread <= 0)
|
---|
369 | break;
|
---|
370 | if (fmt && (fd != prev_fd)) {
|
---|
371 | tail_xprint_header(fmt, filename);
|
---|
372 | fmt = NULL;
|
---|
373 | prev_fd = fd;
|
---|
374 | }
|
---|
375 | xwrite(STDOUT_FILENO, tailbuf, nread);
|
---|
376 | }
|
---|
377 | } while (++i < nfiles);
|
---|
378 | } /* while (1) */
|
---|
379 |
|
---|
380 | if (ENABLE_FEATURE_CLEAN_UP) {
|
---|
381 | free(fds);
|
---|
382 | free(tailbuf);
|
---|
383 | }
|
---|
384 | return G.exitcode;
|
---|
385 | }
|
---|