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         /* Allow legacy syntax of an initial numeric option without -n. */
 125         if (argc >=2 && ((argv[1][0] == '+') || ((argv[1][0] == '-')
 126                         /* && (isdigit)(argv[1][1]) */
 127                         && (((unsigned int)(argv[1][1] - '0')) <= 9))))
 128         {
 129                 optind = 2;
 130                 optarg = argv[1];
 131                 goto GET_COUNT;
 132         }
 133
 134         while ((opt = getopt(argc, argv, tail_opts)) > 0) {
 135                 switch (opt) {
 136                         case 'f':
 137                                 follow = 1;
 138                                 break;
 139                         case 'c':
 140                                 count_bytes = 1;
 141                                 /* FALLS THROUGH */
 142                         case 'n':
 143                         GET_COUNT:
 144                                 count = bb_xgetlarg10_sfx(optarg, tail_suffixes);
 145                                 /* Note: Leading whitespace is an error trapped above. */
 146                                 if (*optarg == '+') {
 147                                         from_top = 1;
 148                                 } else {
 149                                         from_top = 0;
 150                                 }
 151                                 if (count < 0) {
 152                                         count = -count;
 153                                 }
 154                                 break;
 155 #ifdef CONFIG_FEATURE_FANCY_TAIL
 156                         case 'q':
 157                                 header_threshhold = INT_MAX;
 158                                 break;
 159                         case 's':
 160                                 sleep_period =bb_xgetularg10_bnd(optarg, 0, UINT_MAX);
 161                                 break;
 162                         case 'v':
 163                                 header_threshhold = 0;
 164                                 break;
 165 #endif
 166                         default:
 167                                 bb_show_usage();
 168                 }
 169         }
 170
 171         /* open all the files */
 172         fds = (int *)xmalloc(sizeof(int) * (argc - optind + 1));
 173
 174         argv += optind;
 175         nfiles = i = 0;
 176
 177         if ((argc -= optind) == 0) {
 178                 struct stat statbuf;
 179
 180                 if (!fstat(STDIN_FILENO, &statbuf) && S_ISFIFO(statbuf.st_mode)) {
 181                         follow = 0;
 182                 }
 183                 /* --argv; */
 184                 *argv = (char *) bb_msg_standard_input;
 185                 goto DO_STDIN;
 186         }
 187
 188         do {
 189                 if ((argv[i][0] == '-') && !argv[i][1]) {
 190                 DO_STDIN:
 191                         fds[nfiles] = STDIN_FILENO;
 192                 } else if ((fds[nfiles] = open(argv[i], O_RDONLY)) < 0) {
 193                         bb_perror_msg("%s", argv[i]);
 194                         status = EXIT_FAILURE;
 195                         continue;
 196                 }
 197                 argv[nfiles] = argv[i];
 198                 ++nfiles;
 199         } while (++i < argc);
 200
 201         if (!nfiles) {
 202                 bb_error_msg_and_die("no files");
 203         }
 204
 205         tailbufsize = BUFSIZ;
 206
 207         /* tail the files */
 208         if (from_top < count_bytes) {   /* Each is 0 or 1, so true iff 0 < 1. */
 209                 /* Hence, !from_top && count_bytes */
 210                 if (tailbufsize < count) {
 211                         tailbufsize = count + BUFSIZ;
 212                 }
 213         }
 214
 215         buf = tailbuf = xmalloc(tailbufsize);
 216
 217         fmt = header_fmt + 1;   /* Skip header leading newline on first output. */
 218         i = 0;
 219         do {
 220                 /* Be careful.  It would be possible to optimize the count-bytes
 221                  * case if the file is seekable.  If you do though, remember that
 222                  * starting file position may not be the beginning of the file.
 223                  * Beware of backing up too far.  See example in wc.c.
 224                  */
 225                 if ((!(count|from_top)) && (lseek(fds[i], 0, SEEK_END) >= 0)) {
 226                         continue;
 227                 }
 228
 229                 if (nfiles > header_threshhold) {
 230                         tail_xprint_header(fmt, argv[i]);
 231                         fmt = header_fmt;
 232                 }
 233
 234                 buf = tailbuf;
 235                 taillen = 0;
 236                 seen = 1;
 237                 newline = 0;
 238
 239                 while ((nread = tail_read(fds[i], buf, tailbufsize-taillen)) > 0) {
 240                         if (from_top) {
 241                                 nwrite = nread;
 242                                 if (seen < count) {
 243                                         if (count_bytes) {
 244                                                 nwrite -= (count - seen);
 245                                                 seen = count;
 246                                         } else {
 247                                                 s = buf;
 248                                                 do {
 249                                                         --nwrite;
 250                                                         if ((*s++ == '\n') && (++seen == count)) {
 251                                                                 break;
 252                                                         }
 253                                                 } while (nwrite);
 254                                         }
 255                                 }
 256                                 tail_xbb_full_write(buf + nread - nwrite, nwrite);
 257                         } else if (count) {
 258                                 if (count_bytes) {
 259                                         taillen += nread;
 260                                         if (taillen > count) {
 261                                                 memmove(tailbuf, tailbuf + taillen - count, count);
 262                                                 taillen = count;
 263                                         }
 264                                 } else {
 265                                         int k = nread;
 266                                         int nbuf = 0;
 267
 268                                         while (k) {
 269                                                 --k;
 270                                                 if (buf[k] == '\n') {
 271                                                         ++nbuf;
 272                                                 }
 273                                         }
 274
 275                                         if (newline + nbuf < count) {
 276                                                 newline += nbuf;
 277                                                 taillen += nread;
 278
 279                                         } else {
 280                                                 int extra = 0;
 281                                                 if (buf[nread-1] != '\n') {
 282                                                         extra = 1;
 283                                                 }
 284
 285                                                 k = newline + nbuf + extra - count;
 286                                                 s = tailbuf;
 287                                                 while (k) {
 288                                                         if (*s == '\n') {
 289                                                                 --k;
 290                                                         }
 291                                                         ++s;
 292                                                 }
 293
 294                                                 taillen += nread - (s - tailbuf);
 295                                                 memmove(tailbuf, s, taillen);
 296                                                 newline = count - extra;
 297                                         }
 298                                         if (tailbufsize < taillen + BUFSIZ) {
 299                                                 tailbufsize = taillen + BUFSIZ;
 300                                                 tailbuf = xrealloc(tailbuf, tailbufsize);
 301                                         }
 302                                 }
 303                                 buf = tailbuf + taillen;
 304                         }
 305                 }
 306
 307                 if (!from_top) {
 308                         tail_xbb_full_write(tailbuf, taillen);
 309                 }
 310
 311                 taillen = 0;
 312         } while (++i < nfiles);
 313
 314         buf = xrealloc(tailbuf, BUFSIZ);
 315
 316         fmt = NULL;
 317
 318         while (follow) {
 319                 sleep(sleep_period);
 320                 i = 0;
 321                 do {
 322                         if (nfiles > header_threshhold) {
 323                                 fmt = header_fmt;
 324                         }
 325                         while ((nread = tail_read(fds[i], buf, sizeof(buf))) > 0) {
 326                                 if (fmt) {
 327                                         tail_xprint_header(fmt, argv[i]);
 328                                         fmt = NULL;
 329                                 }
 330                                 tail_xbb_full_write(buf, nread);
 331                         }
 332                 } while (++i < nfiles);
 333         }
 334
 335         return status;
 336 }