blob: 0e124436069815ab3c18dc503ecb746658a33d9e
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-$(CONFIG_TAIL) += tail.o |
28 | |
29 | //usage:#define tail_trivial_usage |
30 | //usage: "[OPTIONS] [FILE]..." |
31 | //usage:#define tail_full_usage "\n\n" |
32 | //usage: "Print last 10 lines of each FILE (or stdin) to stdout.\n" |
33 | //usage: "With more than one FILE, precede each with a filename header.\n" |
34 | //usage: "\n -f Print data as file grows" |
35 | //usage: IF_FEATURE_FANCY_TAIL( |
36 | //usage: "\n -s SECONDS Wait SECONDS between reads with -f" |
37 | //usage: ) |
38 | //usage: "\n -n N[kbm] Print last N lines" |
39 | //usage: "\n -n +N[kbm] Start on Nth line and print the rest" |
40 | //usage: IF_FEATURE_FANCY_TAIL( |
41 | //usage: "\n -c [+]N[kbm] Print last N bytes" |
42 | //usage: "\n -q Never print headers" |
43 | //usage: "\n -v Always print headers" |
44 | //usage: "\n" |
45 | //usage: "\nN may be suffixed by k (x1024), b (x512), or m (x1024^2)." |
46 | //usage: ) |
47 | //usage: |
48 | //usage:#define tail_example_usage |
49 | //usage: "$ tail -n 1 /etc/resolv.conf\n" |
50 | //usage: "nameserver 10.0.0.1\n" |
51 | |
52 | #include "libbb.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 { } 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 | int header_threshhold = 1; |
103 | int 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 | } |
386 |