coreutils/tail.c

   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  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  15  * General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  20  *
  21  */
  22
  23 /* BB_AUDIT SUSv3 compliant (need fancy for -c) */
  24 /* BB_AUDIT GNU compatible -c, -q, and -v options in 'fancy' configuration. */
  25 /* http://www.opengroup.org/onlinepubs/007904975/utilities/tail.html */
  26
  27 /* Mar 16, 2003      Manuel Novoa III   (mjn3@codepoet.org)
  28  *
  29  * Pretty much rewritten to fix numerous bugs and reduce realloc() calls.
  30  * Bugs fixed (although I may have forgotten one or two... it was pretty bad)
  31  * 1) mixing printf/write without fflush()ing stdout
  32  * 2) no check that any open files are present
  33  * 3) optstring had -q taking an arg
  34  * 4) no error checking on write in some cases, and a warning even then
  35  * 5) q and s interaction bug
  36  * 6) no check for lseek error
  37  * 7) lseek attempted when count==0 even if arg was +0 (from top)
  38  */
  39
  40 #include <stdio.h>
  41 #include <stdlib.h>
  42 #include <string.h>
  43 #include <ctype.h>
  44 #include <unistd.h>
  45 #include <fcntl.h>
  46 #include <sys/stat.h>
  47 #include "busybox.h"
  48
  49 static const struct suffix_mult tail_suffixes[] = {
  50         { "b", 512 },
  51         { "k", 1024 },
  52         { "m", 1048576 },
  53         { NULL, 0 }
  54 };
  55
  56 static int status
  57 #if EXIT_SUCCESS != 0
  58         = EXIT_SUCCESS  /* If it is 0 (paranoid check), let bss initialize it. */
  59 #endif
  60         ;
  61
  62 static void tail_xprint_header(const char *fmt, const char *filename)
  63 {
  64         /* If we get an output error, there is really no sense in continuing. */
  65         if (dprintf(STDOUT_FILENO, fmt, filename) < 0) {
  66                 bb_perror_nomsg_and_die();
  67         }
  68 }
  69
  70 /* len should probably be size_t */
  71 static void tail_xbb_full_write(const char *buf, size_t len)
  72 {
  73         /* If we get a write error, there is really no sense in continuing. */
  74         if (bb_full_write(STDOUT_FILENO, buf, len) < 0) {
  75                 bb_perror_nomsg_and_die();
  76         }
  77 }
  78
  79 static ssize_t tail_read(int fd, char *buf, size_t count)
  80 {
  81         ssize_t r;
  82         off_t current,end;
  83         struct stat sbuf;
  84
  85         end = current = lseek(fd, 0, SEEK_CUR);
  86         if (!fstat(fd, &sbuf))
  87                 end = sbuf.st_size;
  88         lseek(fd, end < current ? 0 : current, SEEK_SET);
  89         if ((r = safe_read(fd, buf, count)) < 0) {
  90                 bb_perror_msg("read");
  91                 status = EXIT_FAILURE;
  92         }
  93
  94         return r;
  95 }
  96
  97 static const char tail_opts[] =
  98         "fn:c:"
  99 #ifdef CONFIG_FEATURE_FANCY_TAIL
 100         "qs:v"
 101 #endif
 102         ;
 103
 104 static const char header_fmt[] = "\n==> %s <==\n";
 105
 106 int tail_main(int argc, char **argv)
 107 {
 108         long count = 10;
 109         unsigned int sleep_period = 1;
 110         int from_top = 0;
 111         int follow = 0;
 112         int header_threshhold = 1;
 113         int count_bytes = 0;
 114
 115         char *tailbuf;
 116         size_t tailbufsize;
 117         int taillen = 0;
 118         int newline = 0;
 119
 120         int *fds, nfiles, nread, nwrite, seen, i, opt;
 121         char *s, *buf;
 122         const char *fmt;
 123
 124 #ifdef CONFIG_FEATURE_SUSv2
 125         /* Allow legacy syntax of an initial numeric option without -n. */
 126         if (argc >=2 && ((argv[1][0] == '+') || ((argv[1][0] == '-')
 127                         /* && (isdigit)(argv[1][1]) */
 128                         && (((unsigned int)(argv[1][1] - '0')) <= 9))))
 129         {
 130                 optind = 2;
 131                 optarg = argv[1];
 132                 goto GET_COUNT;
 133         }
 134 #endif
 135
 136         while ((opt = getopt(argc, argv, tail_opts)) > 0) {
 137                 switch (opt) {
 138                         case 'f':
 139                                 follow = 1;
 140                                 break;
 141                         case 'c':
 142                                 count_bytes = 1;
 143                                 /* FALLS THROUGH */
 144                         case 'n':
 145                         GET_COUNT:
 146                                 count = bb_xgetlarg10_sfx(optarg, tail_suffixes);
 147                                 /* Note: Leading whitespace is an error trapped above. */
 148                                 if (*optarg == '+') {
 149                                         from_top = 1;
 150                                 } else {
 151                                         from_top = 0;
 152                                 }
 153                                 if (count < 0) {
 154                                         count = -count;
 155                                 }
 156                                 break;
 157 #ifdef CONFIG_FEATURE_FANCY_TAIL
 158                         case 'q':
 159                                 header_threshhold = INT_MAX;
 160                                 break;
 161                         case 's':
 162                                 sleep_period =bb_xgetularg10_bnd(optarg, 0, UINT_MAX);
 163                                 break;
 164                         case 'v':
 165                                 header_threshhold = 0;
 166                                 break;
 167 #endif
 168                         default:
 169                                 bb_show_usage();
 170                 }
 171         }
 172
 173         /* open all the files */
 174         fds = (int *)xmalloc(sizeof(int) * (argc - optind + 1));
 175
 176         argv += optind;
 177         nfiles = i = 0;
 178
 179         if ((argc -= optind) == 0) {
 180                 struct stat statbuf;
 181
 182                 if (!fstat(STDIN_FILENO, &statbuf) && S_ISFIFO(statbuf.st_mode)) {
 183                         follow = 0;
 184                 }
 185                 /* --argv; */
 186                 *argv = (char *) bb_msg_standard_input;
 187                 goto DO_STDIN;
 188         }
 189
 190         do {
 191                 if ((argv[i][0] == '-') && !argv[i][1]) {
 192                 DO_STDIN:
 193                         fds[nfiles] = STDIN_FILENO;
 194                 } else if ((fds[nfiles] = open(argv[i], O_RDONLY)) < 0) {
 195                         bb_perror_msg("%s", argv[i]);
 196                         status = EXIT_FAILURE;
 197                         continue;
 198                 }
 199                 argv[nfiles] = argv[i];
 200                 ++nfiles;
 201         } while (++i < argc);
 202
 203         if (!nfiles) {
 204                 bb_error_msg_and_die("no files");
 205         }
 206
 207         tailbufsize = BUFSIZ;
 208
 209         /* tail the files */
 210         if (from_top < count_bytes) {   /* Each is 0 or 1, so true iff 0 < 1. */
 211                 /* Hence, !from_top && count_bytes */
 212                 if (tailbufsize < count) {
 213                         tailbufsize = count + BUFSIZ;
 214                 }
 215         }
 216
 217         buf = tailbuf = xmalloc(tailbufsize);
 218
 219         fmt = header_fmt + 1;   /* Skip header leading newline on first output. */
 220         i = 0;
 221         do {
 222                 /* Be careful.  It would be possible to optimize the count-bytes
 223                  * case if the file is seekable.  If you do though, remember that
 224                  * starting file position may not be the beginning of the file.
 225                  * Beware of backing up too far.  See example in wc.c.
 226                  */
 227                 if ((!(count|from_top)) && (lseek(fds[i], 0, SEEK_END) >= 0)) {
 228                         continue;
 229                 }
 230
 231                 if (nfiles > header_threshhold) {
 232                         tail_xprint_header(fmt, argv[i]);
 233                         fmt = header_fmt;
 234                 }
 235
 236                 buf = tailbuf;
 237                 taillen = 0;
 238                 seen = 1;
 239                 newline = 0;
 240
 241                 while ((nread = tail_read(fds[i], buf, tailbufsize-taillen)) > 0) {
 242                         if (from_top) {
 243                                 nwrite = nread;
 244                                 if (seen < count) {
 245                                         if (count_bytes) {
 246                                                 nwrite -= (count - seen);
 247                                                 seen = count;
 248                                         } else {
 249                                                 s = buf;
 250                                                 do {
 251                                                         --nwrite;
 252                                                         if ((*s++ == '\n') && (++seen == count)) {
 253                                                                 break;
 254                                                         }
 255                                                 } while (nwrite);
 256                                         }
 257                                 }
 258                                 tail_xbb_full_write(buf + nread - nwrite, nwrite);
 259                         } else if (count) {
 260                                 if (count_bytes) {
 261                                         taillen += nread;
 262                                         if (taillen > count) {
 263                                                 memmove(tailbuf, tailbuf + taillen - count, count);
 264                                                 taillen = count;
 265                                         }
 266                                 } else {
 267                                         int k = nread;
 268                                         int nbuf = 0;
 269
 270                                         while (k) {
 271                                                 --k;
 272                                                 if (buf[k] == '\n') {
 273                                                         ++nbuf;
 274                                                 }
 275                                         }
 276
 277                                         if (newline + nbuf < count) {
 278                                                 newline += nbuf;
 279                                                 taillen += nread;
 280
 281                                         } else {
 282                                                 int extra = 0;
 283                                                 if (buf[nread-1] != '\n') {
 284                                                         extra = 1;
 285                                                 }
 286
 287                                                 k = newline + nbuf + extra - count;
 288                                                 s = tailbuf;
 289                                                 while (k) {
 290                                                         if (*s == '\n') {
 291                                                                 --k;
 292                                                         }
 293                                                         ++s;
 294                                                 }
 295
 296                                                 taillen += nread - (s - tailbuf);
 297                                                 memmove(tailbuf, s, taillen);
 298                                                 newline = count - extra;
 299                                         }
 300                                         if (tailbufsize < taillen + BUFSIZ) {
 301                                                 tailbufsize = taillen + BUFSIZ;
 302                                                 tailbuf = xrealloc(tailbuf, tailbufsize);
 303                                         }
 304                                 }
 305                                 buf = tailbuf + taillen;
 306                         }
 307                 }
 308
 309                 if (!from_top) {
 310                         tail_xbb_full_write(tailbuf, taillen);
 311                 }
 312
 313                 taillen = 0;
 314         } while (++i < nfiles);
 315
 316         buf = xrealloc(tailbuf, BUFSIZ);
 317
 318         fmt = NULL;
 319
 320         while (follow) {
 321                 sleep(sleep_period);
 322                 i = 0;
 323                 do {
 324                         if (nfiles > header_threshhold) {
 325                                 fmt = header_fmt;
 326                         }
 327                         while ((nread = tail_read(fds[i], buf, sizeof(buf))) > 0) {
 328                                 if (fmt) {
 329                                         tail_xprint_header(fmt, argv[i]);
 330                                         fmt = NULL;
 331                                 }
 332                                 tail_xbb_full_write(buf, nread);
 333                         }
 334                 } while (++i < nfiles);
 335         }
 336
 337         return status;
 338 }