Contents of /tags/mkinitrd-6_4_0/busybox/coreutils/tail.c
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Fri May 27 18:20:23 2011 UTC (13 years, 4 months ago) by niro
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Fri May 27 18:20:23 2011 UTC (13 years, 4 months ago) by niro
File MIME type: text/plain
File size: 8617 byte(s)
tagged 'mkinitrd-6_4_0'
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 tarball for details. |
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 | #include "libbb.h" |
28 | |
29 | static const struct suffix_mult tail_suffixes[] = { |
30 | { "b", 512 }, |
31 | { "k", 1024 }, |
32 | { "m", 1024*1024 }, |
33 | { "", 0 } |
34 | }; |
35 | |
36 | struct globals { |
37 | bool status; |
38 | } FIX_ALIASING; |
39 | #define G (*(struct globals*)&bb_common_bufsiz1) |
40 | |
41 | static void tail_xprint_header(const char *fmt, const char *filename) |
42 | { |
43 | if (fdprintf(STDOUT_FILENO, fmt, filename) < 0) |
44 | bb_perror_nomsg_and_die(); |
45 | } |
46 | |
47 | static ssize_t tail_read(int fd, char *buf, size_t count) |
48 | { |
49 | ssize_t r; |
50 | off_t current; |
51 | struct stat sbuf; |
52 | |
53 | /* /proc files report zero st_size, don't lseek them. */ |
54 | if (fstat(fd, &sbuf) == 0 && sbuf.st_size > 0) { |
55 | current = lseek(fd, 0, SEEK_CUR); |
56 | if (sbuf.st_size < current) |
57 | xlseek(fd, 0, SEEK_SET); |
58 | } |
59 | |
60 | r = full_read(fd, buf, count); |
61 | if (r < 0) { |
62 | bb_perror_msg(bb_msg_read_error); |
63 | G.status = EXIT_FAILURE; |
64 | } |
65 | |
66 | return r; |
67 | } |
68 | |
69 | #define header_fmt_str "\n==> %s <==\n" |
70 | |
71 | static unsigned eat_num(const char *p) |
72 | { |
73 | if (*p == '-') |
74 | p++; |
75 | else if (*p == '+') { |
76 | p++; |
77 | G.status = 1; /* mark that we saw "+" */ |
78 | } |
79 | return xatou_sfx(p, tail_suffixes); |
80 | } |
81 | |
82 | int tail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; |
83 | int tail_main(int argc, char **argv) |
84 | { |
85 | unsigned count = 10; |
86 | unsigned sleep_period = 1; |
87 | bool from_top; |
88 | const char *str_c, *str_n; |
89 | |
90 | char *tailbuf; |
91 | size_t tailbufsize; |
92 | unsigned header_threshhold = 1; |
93 | unsigned nfiles; |
94 | int i, opt; |
95 | |
96 | int *fds; |
97 | const char *fmt; |
98 | |
99 | #if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_TAIL |
100 | /* Allow legacy syntax of an initial numeric option without -n. */ |
101 | if (argv[1] && (argv[1][0] == '+' || argv[1][0] == '-') |
102 | && isdigit(argv[1][1]) |
103 | ) { |
104 | count = eat_num(argv[1]); |
105 | argv++; |
106 | argc--; |
107 | } |
108 | #endif |
109 | |
110 | /* -s NUM, -F imlies -f */ |
111 | IF_FEATURE_FANCY_TAIL(opt_complementary = "s+:Ff";) |
112 | opt = getopt32(argv, "fc:n:" IF_FEATURE_FANCY_TAIL("qs:vF"), |
113 | &str_c, &str_n IF_FEATURE_FANCY_TAIL(,&sleep_period)); |
114 | #define FOLLOW (opt & 0x1) |
115 | #define COUNT_BYTES (opt & 0x2) |
116 | //if (opt & 0x1) // -f |
117 | if (opt & 0x2) count = eat_num(str_c); // -c |
118 | if (opt & 0x4) count = eat_num(str_n); // -n |
119 | #if ENABLE_FEATURE_FANCY_TAIL |
120 | /* q: make it impossible for nfiles to be > header_threshhold */ |
121 | if (opt & 0x8) header_threshhold = UINT_MAX; // -q |
122 | //if (opt & 0x10) // -s |
123 | if (opt & 0x20) header_threshhold = 0; // -v |
124 | # define FOLLOW_RETRY (opt & 0x40) |
125 | #else |
126 | # define FOLLOW_RETRY 0 |
127 | #endif |
128 | argc -= optind; |
129 | argv += optind; |
130 | from_top = G.status; /* 1 if there was "-c +N" or "-n +N" */ |
131 | G.status = EXIT_SUCCESS; |
132 | |
133 | /* open all the files */ |
134 | fds = xmalloc(sizeof(fds[0]) * (argc + 1)); |
135 | if (!argv[0]) { |
136 | struct stat statbuf; |
137 | |
138 | if (fstat(STDIN_FILENO, &statbuf) == 0 |
139 | && S_ISFIFO(statbuf.st_mode) |
140 | ) { |
141 | opt &= ~1; /* clear FOLLOW */ |
142 | } |
143 | argv[0] = (char *) bb_msg_standard_input; |
144 | } |
145 | nfiles = i = 0; |
146 | do { |
147 | int fd = open_or_warn_stdin(argv[i]); |
148 | if (fd < 0 && !FOLLOW_RETRY) { |
149 | G.status = EXIT_FAILURE; |
150 | continue; |
151 | } |
152 | fds[nfiles] = fd; |
153 | argv[nfiles++] = argv[i]; |
154 | } while (++i < argc); |
155 | |
156 | if (!nfiles) |
157 | bb_error_msg_and_die("no files"); |
158 | |
159 | /* prepare the buffer */ |
160 | tailbufsize = BUFSIZ; |
161 | if (!from_top && COUNT_BYTES) { |
162 | if (tailbufsize < count + BUFSIZ) { |
163 | tailbufsize = count + BUFSIZ; |
164 | } |
165 | } |
166 | tailbuf = xmalloc(tailbufsize); |
167 | |
168 | /* tail the files */ |
169 | fmt = header_fmt_str + 1; /* skip header leading newline on first output */ |
170 | i = 0; |
171 | do { |
172 | char *buf; |
173 | int taillen; |
174 | int newlines_seen; |
175 | unsigned seen; |
176 | int nread; |
177 | int fd = fds[i]; |
178 | |
179 | if (ENABLE_FEATURE_FANCY_TAIL && fd < 0) |
180 | continue; /* may happen with -E */ |
181 | |
182 | if (nfiles > header_threshhold) { |
183 | tail_xprint_header(fmt, argv[i]); |
184 | fmt = header_fmt_str; |
185 | } |
186 | |
187 | if (!from_top) { |
188 | off_t current = lseek(fd, 0, SEEK_END); |
189 | if (current > 0) { |
190 | unsigned off; |
191 | if (COUNT_BYTES) { |
192 | /* Optimizing count-bytes case if the file is seekable. |
193 | * Beware of backing up too far. |
194 | * Also we exclude files with size 0 (because of /proc/xxx) */ |
195 | if (count == 0) |
196 | continue; /* showing zero bytes is easy :) */ |
197 | current -= count; |
198 | if (current < 0) |
199 | current = 0; |
200 | xlseek(fd, current, SEEK_SET); |
201 | bb_copyfd_size(fd, STDOUT_FILENO, count); |
202 | continue; |
203 | } |
204 | #if 1 /* This is technically incorrect for *LONG* strings, but very useful */ |
205 | /* Optimizing count-lines case if the file is seekable. |
206 | * We assume the lines are <64k. |
207 | * (Users complain that tail takes too long |
208 | * on multi-gigabyte files) */ |
209 | off = (count | 0xf); /* for small counts, be more paranoid */ |
210 | if (off > (INT_MAX / (64*1024))) |
211 | off = (INT_MAX / (64*1024)); |
212 | current -= off * (64*1024); |
213 | if (current < 0) |
214 | current = 0; |
215 | xlseek(fd, current, SEEK_SET); |
216 | #endif |
217 | } |
218 | } |
219 | |
220 | buf = tailbuf; |
221 | taillen = 0; |
222 | /* "We saw 1st line/byte". |
223 | * Used only by +N code ("start from Nth", 1-based): */ |
224 | seen = 1; |
225 | newlines_seen = 0; |
226 | while ((nread = tail_read(fd, buf, tailbufsize-taillen)) > 0) { |
227 | if (from_top) { |
228 | int nwrite = nread; |
229 | if (seen < count) { |
230 | /* We need to skip a few more bytes/lines */ |
231 | if (COUNT_BYTES) { |
232 | nwrite -= (count - seen); |
233 | seen = count; |
234 | } else { |
235 | char *s = buf; |
236 | do { |
237 | --nwrite; |
238 | if (*s++ == '\n' && ++seen == count) { |
239 | break; |
240 | } |
241 | } while (nwrite); |
242 | } |
243 | } |
244 | if (nwrite > 0) |
245 | xwrite(STDOUT_FILENO, buf + nread - nwrite, nwrite); |
246 | } else if (count) { |
247 | if (COUNT_BYTES) { |
248 | taillen += nread; |
249 | if (taillen > (int)count) { |
250 | memmove(tailbuf, tailbuf + taillen - count, count); |
251 | taillen = count; |
252 | } |
253 | } else { |
254 | int k = nread; |
255 | int newlines_in_buf = 0; |
256 | |
257 | do { /* count '\n' in last read */ |
258 | k--; |
259 | if (buf[k] == '\n') { |
260 | newlines_in_buf++; |
261 | } |
262 | } while (k); |
263 | |
264 | if (newlines_seen + newlines_in_buf < (int)count) { |
265 | newlines_seen += newlines_in_buf; |
266 | taillen += nread; |
267 | } else { |
268 | int extra = (buf[nread-1] != '\n'); |
269 | char *s; |
270 | |
271 | k = newlines_seen + newlines_in_buf + extra - count; |
272 | s = tailbuf; |
273 | while (k) { |
274 | if (*s == '\n') { |
275 | k--; |
276 | } |
277 | s++; |
278 | } |
279 | taillen += nread - (s - tailbuf); |
280 | memmove(tailbuf, s, taillen); |
281 | newlines_seen = count - extra; |
282 | } |
283 | if (tailbufsize < (size_t)taillen + BUFSIZ) { |
284 | tailbufsize = taillen + BUFSIZ; |
285 | tailbuf = xrealloc(tailbuf, tailbufsize); |
286 | } |
287 | } |
288 | buf = tailbuf + taillen; |
289 | } |
290 | } /* while (tail_read() > 0) */ |
291 | if (!from_top) { |
292 | xwrite(STDOUT_FILENO, tailbuf, taillen); |
293 | } |
294 | } while (++i < nfiles); |
295 | |
296 | tailbuf = xrealloc(tailbuf, BUFSIZ); |
297 | |
298 | fmt = NULL; |
299 | |
300 | if (FOLLOW) while (1) { |
301 | sleep(sleep_period); |
302 | |
303 | i = 0; |
304 | do { |
305 | int nread; |
306 | const char *filename = argv[i]; |
307 | int fd = fds[i]; |
308 | |
309 | if (FOLLOW_RETRY) { |
310 | struct stat sbuf, fsbuf; |
311 | |
312 | if (fd < 0 |
313 | || fstat(fd, &fsbuf) < 0 |
314 | || stat(filename, &sbuf) < 0 |
315 | || fsbuf.st_dev != sbuf.st_dev |
316 | || fsbuf.st_ino != sbuf.st_ino |
317 | ) { |
318 | int new_fd; |
319 | |
320 | if (fd >= 0) |
321 | close(fd); |
322 | new_fd = open(filename, O_RDONLY); |
323 | if (new_fd >= 0) { |
324 | bb_error_msg("%s has %s; following end of new file", |
325 | filename, (fd < 0) ? "appeared" : "been replaced" |
326 | ); |
327 | } else if (fd >= 0) { |
328 | bb_perror_msg("%s has become inaccessible", filename); |
329 | } |
330 | fds[i] = fd = new_fd; |
331 | } |
332 | } |
333 | if (ENABLE_FEATURE_FANCY_TAIL && fd < 0) |
334 | continue; |
335 | if (nfiles > header_threshhold) { |
336 | fmt = header_fmt_str; |
337 | } |
338 | while ((nread = tail_read(fd, tailbuf, BUFSIZ)) > 0) { |
339 | if (fmt) { |
340 | tail_xprint_header(fmt, filename); |
341 | fmt = NULL; |
342 | } |
343 | xwrite(STDOUT_FILENO, tailbuf, nread); |
344 | } |
345 | } while (++i < nfiles); |
346 | } |
347 | if (ENABLE_FEATURE_CLEAN_UP) { |
348 | free(fds); |
349 | } |
350 | return G.status; |
351 | } |