source: MondoRescue/branches/3.2/mindi-busybox/coreutils/tail.c@ 3232

Last change on this file since 3232 was 3232, checked in by Bruno Cornec, 10 years ago
  • Update mindi-busybox to 1.21.1
File size: 9.6 KB
Line 
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//usage:#define tail_trivial_usage
28//usage: "[OPTIONS] [FILE]..."
29//usage:#define tail_full_usage "\n\n"
30//usage: "Print last 10 lines of each FILE (or stdin) to stdout.\n"
31//usage: "With more than one FILE, precede each with a filename header.\n"
32//usage: "\n -f Print data as file grows"
33//usage: IF_FEATURE_FANCY_TAIL(
34//usage: "\n -s SECONDS Wait SECONDS between reads with -f"
35//usage: )
36//usage: "\n -n N[kbm] Print last N lines"
37//usage: IF_FEATURE_FANCY_TAIL(
38//usage: "\n -c N[kbm] Print last N bytes"
39//usage: "\n -q Never print headers"
40//usage: "\n -v Always print headers"
41//usage: "\n"
42//usage: "\nN may be suffixed by k (x1024), b (x512), or m (x1024^2)."
43//usage: "\nIf N starts with a '+', output begins with the Nth item from the start"
44//usage: "\nof each file, not from the end."
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
53static const struct suffix_mult tail_suffixes[] = {
54 { "b", 512 },
55 { "k", 1024 },
56 { "m", 1024*1024 },
57 { "", 0 }
58};
59
60struct globals {
61 bool from_top;
62 bool exitcode;
63} FIX_ALIASING;
64#define G (*(struct globals*)&bb_common_bufsiz1)
65#define INIT_G() do { } while (0)
66
67static void tail_xprint_header(const char *fmt, const char *filename)
68{
69 if (fdprintf(STDOUT_FILENO, fmt, filename) < 0)
70 bb_perror_nomsg_and_die();
71}
72
73static ssize_t tail_read(int fd, char *buf, size_t count)
74{
75 ssize_t r;
76 off_t current;
77 struct stat sbuf;
78
79 /* /proc files report zero st_size, don't lseek them. */
80 if (fstat(fd, &sbuf) == 0 && sbuf.st_size > 0) {
81 current = lseek(fd, 0, SEEK_CUR);
82 if (sbuf.st_size < current)
83 xlseek(fd, 0, SEEK_SET);
84 }
85
86 r = full_read(fd, buf, count);
87 if (r < 0) {
88 bb_perror_msg(bb_msg_read_error);
89 G.exitcode = EXIT_FAILURE;
90 }
91
92 return r;
93}
94
95#define header_fmt_str "\n==> %s <==\n"
96
97static unsigned eat_num(const char *p)
98{
99 if (*p == '-')
100 p++;
101 else if (*p == '+') {
102 p++;
103 G.from_top = 1;
104 }
105 return xatou_sfx(p, tail_suffixes);
106}
107
108int tail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
109int tail_main(int argc, char **argv)
110{
111 unsigned count = 10;
112 unsigned sleep_period = 1;
113 const char *str_c, *str_n;
114
115 char *tailbuf;
116 size_t tailbufsize;
117 unsigned header_threshhold = 1;
118 unsigned nfiles;
119 int i, opt;
120
121 int *fds;
122 const char *fmt;
123
124 INIT_G();
125
126#if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_TAIL
127 /* Allow legacy syntax of an initial numeric option without -n. */
128 if (argv[1] && (argv[1][0] == '+' || argv[1][0] == '-')
129 && isdigit(argv[1][1])
130 ) {
131 count = eat_num(argv[1]);
132 argv++;
133 argc--;
134 }
135#endif
136
137 /* -s NUM, -F imlies -f */
138 IF_FEATURE_FANCY_TAIL(opt_complementary = "s+:Ff";)
139 opt = getopt32(argv, "fc:n:" IF_FEATURE_FANCY_TAIL("qs:vF"),
140 &str_c, &str_n IF_FEATURE_FANCY_TAIL(,&sleep_period));
141#define FOLLOW (opt & 0x1)
142#define COUNT_BYTES (opt & 0x2)
143 //if (opt & 0x1) // -f
144 if (opt & 0x2) count = eat_num(str_c); // -c
145 if (opt & 0x4) count = eat_num(str_n); // -n
146#if ENABLE_FEATURE_FANCY_TAIL
147 /* q: make it impossible for nfiles to be > header_threshhold */
148 if (opt & 0x8) header_threshhold = UINT_MAX; // -q
149 //if (opt & 0x10) // -s
150 if (opt & 0x20) header_threshhold = 0; // -v
151# define FOLLOW_RETRY (opt & 0x40)
152#else
153# define FOLLOW_RETRY 0
154#endif
155 argc -= optind;
156 argv += optind;
157
158 /* open all the files */
159 fds = xmalloc(sizeof(fds[0]) * (argc + 1));
160 if (!argv[0]) {
161 struct stat statbuf;
162
163 if (fstat(STDIN_FILENO, &statbuf) == 0
164 && S_ISFIFO(statbuf.st_mode)
165 ) {
166 opt &= ~1; /* clear FOLLOW */
167 }
168 argv[0] = (char *) bb_msg_standard_input;
169 }
170 nfiles = i = 0;
171 do {
172 int fd = open_or_warn_stdin(argv[i]);
173 if (fd < 0 && !FOLLOW_RETRY) {
174 G.exitcode = EXIT_FAILURE;
175 continue;
176 }
177 fds[nfiles] = fd;
178 argv[nfiles++] = argv[i];
179 } while (++i < argc);
180
181 if (!nfiles)
182 bb_error_msg_and_die("no files");
183
184 /* prepare the buffer */
185 tailbufsize = BUFSIZ;
186 if (!G.from_top && COUNT_BYTES) {
187 if (tailbufsize < count + BUFSIZ) {
188 tailbufsize = count + BUFSIZ;
189 }
190 }
191 /* tail -c1024m REGULAR_FILE doesn't really need 1G mem block.
192 * (In fact, it doesn't need ANY memory). So delay allocation.
193 */
194 tailbuf = NULL;
195
196 /* tail the files */
197
198 fmt = header_fmt_str + 1; /* skip leading newline in the header on the first output */
199 i = 0;
200 do {
201 char *buf;
202 int taillen;
203 int newlines_seen;
204 unsigned seen;
205 int nread;
206 int fd = fds[i];
207
208 if (ENABLE_FEATURE_FANCY_TAIL && fd < 0)
209 continue; /* may happen with -F */
210
211 if (nfiles > header_threshhold) {
212 tail_xprint_header(fmt, argv[i]);
213 fmt = header_fmt_str;
214 }
215
216 if (!G.from_top) {
217 off_t current = lseek(fd, 0, SEEK_END);
218 if (current > 0) {
219 unsigned off;
220 if (COUNT_BYTES) {
221 /* Optimizing count-bytes case if the file is seekable.
222 * Beware of backing up too far.
223 * Also we exclude files with size 0 (because of /proc/xxx) */
224 if (count == 0)
225 continue; /* showing zero bytes is easy :) */
226 current -= count;
227 if (current < 0)
228 current = 0;
229 xlseek(fd, current, SEEK_SET);
230 bb_copyfd_size(fd, STDOUT_FILENO, count);
231 continue;
232 }
233#if 1 /* This is technically incorrect for *LONG* strings, but very useful */
234 /* Optimizing count-lines case if the file is seekable.
235 * We assume the lines are <64k.
236 * (Users complain that tail takes too long
237 * on multi-gigabyte files) */
238 off = (count | 0xf); /* for small counts, be more paranoid */
239 if (off > (INT_MAX / (64*1024)))
240 off = (INT_MAX / (64*1024));
241 current -= off * (64*1024);
242 if (current < 0)
243 current = 0;
244 xlseek(fd, current, SEEK_SET);
245#endif
246 }
247 }
248
249 if (!tailbuf)
250 tailbuf = xmalloc(tailbufsize);
251
252 buf = tailbuf;
253 taillen = 0;
254 /* "We saw 1st line/byte".
255 * Used only by +N code ("start from Nth", 1-based): */
256 seen = 1;
257 newlines_seen = 0;
258 while ((nread = tail_read(fd, buf, tailbufsize - taillen)) > 0) {
259 if (G.from_top) {
260 int nwrite = nread;
261 if (seen < count) {
262 /* We need to skip a few more bytes/lines */
263 if (COUNT_BYTES) {
264 nwrite -= (count - seen);
265 seen += nread;
266 } else {
267 char *s = buf;
268 do {
269 --nwrite;
270 if (*s++ == '\n' && ++seen == count) {
271 break;
272 }
273 } while (nwrite);
274 }
275 }
276 if (nwrite > 0)
277 xwrite(STDOUT_FILENO, buf + nread - nwrite, nwrite);
278 } else if (count) {
279 if (COUNT_BYTES) {
280 taillen += nread;
281 if (taillen > (int)count) {
282 memmove(tailbuf, tailbuf + taillen - count, count);
283 taillen = count;
284 }
285 } else {
286 int k = nread;
287 int newlines_in_buf = 0;
288
289 do { /* count '\n' in last read */
290 k--;
291 if (buf[k] == '\n') {
292 newlines_in_buf++;
293 }
294 } while (k);
295
296 if (newlines_seen + newlines_in_buf < (int)count) {
297 newlines_seen += newlines_in_buf;
298 taillen += nread;
299 } else {
300 int extra = (buf[nread-1] != '\n');
301 char *s;
302
303 k = newlines_seen + newlines_in_buf + extra - count;
304 s = tailbuf;
305 while (k) {
306 if (*s == '\n') {
307 k--;
308 }
309 s++;
310 }
311 taillen += nread - (s - tailbuf);
312 memmove(tailbuf, s, taillen);
313 newlines_seen = count - extra;
314 }
315 if (tailbufsize < (size_t)taillen + BUFSIZ) {
316 tailbufsize = taillen + BUFSIZ;
317 tailbuf = xrealloc(tailbuf, tailbufsize);
318 }
319 }
320 buf = tailbuf + taillen;
321 }
322 } /* while (tail_read() > 0) */
323 if (!G.from_top) {
324 xwrite(STDOUT_FILENO, tailbuf, taillen);
325 }
326 } while (++i < nfiles);
327
328 tailbuf = xrealloc(tailbuf, BUFSIZ);
329
330 fmt = NULL;
331
332 if (FOLLOW) while (1) {
333 sleep(sleep_period);
334
335 i = 0;
336 do {
337 int nread;
338 const char *filename = argv[i];
339 int fd = fds[i];
340
341 if (FOLLOW_RETRY) {
342 struct stat sbuf, fsbuf;
343
344 if (fd < 0
345 || fstat(fd, &fsbuf) < 0
346 || stat(filename, &sbuf) < 0
347 || fsbuf.st_dev != sbuf.st_dev
348 || fsbuf.st_ino != sbuf.st_ino
349 ) {
350 int new_fd;
351
352 if (fd >= 0)
353 close(fd);
354 new_fd = open(filename, O_RDONLY);
355 if (new_fd >= 0) {
356 bb_error_msg("%s has %s; following end of new file",
357 filename, (fd < 0) ? "appeared" : "been replaced"
358 );
359 } else if (fd >= 0) {
360 bb_perror_msg("%s has become inaccessible", filename);
361 }
362 fds[i] = fd = new_fd;
363 }
364 }
365 if (ENABLE_FEATURE_FANCY_TAIL && fd < 0)
366 continue;
367 if (nfiles > header_threshhold) {
368 fmt = header_fmt_str;
369 }
370 while ((nread = tail_read(fd, tailbuf, BUFSIZ)) > 0) {
371 if (fmt) {
372 tail_xprint_header(fmt, filename);
373 fmt = NULL;
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}
Note: See TracBrowser for help on using the repository browser.