source: MondoRescue/branches/3.3/mindi-busybox/coreutils/tail.c@ 3621

Last change on this file since 3621 was 3621, checked in by Bruno Cornec, 7 years ago

New 3?3 banch for incorporation of latest busybox 1.25. Changing minor version to handle potential incompatibilities.
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//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
54struct 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
61static 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
67static 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
82static 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
93int tail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
94int 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}
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