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 (printf(fmt, filename) < 0 ||
  66                         fflush(stdout) < 0) {
  67                 bb_perror_nomsg_and_die();
  68         }
  69 }
  70
  71 /* len should probably be size_t */
  72 static void tail_xbb_full_write(const char *buf, size_t len)
  73 {
  74         /* If we get a write error, there is really no sense in continuing. */
  75         if (bb_full_write(STDOUT_FILENO, buf, len) < 0) {
  76                 bb_perror_nomsg_and_die();
  77         }
  78 }
  79
  80 static ssize_t tail_read(int fd, char *buf, size_t count)
  81 {
  82         ssize_t r;
  83
  84         if ((r = safe_read(fd, buf, count)) < 0) {
  85                 bb_perror_msg("read");
  86                 status = EXIT_FAILURE;
  87         }
  88
  89         return r;
  90 }
  91
  92 static const char tail_opts[] =
  93         "fn:c:"
  94 #ifdef CONFIG_FEATURE_FANCY_TAIL
  95         "qs:v"
  96 #endif
  97         ;
  98
  99 static const char header_fmt[] = "\n==> %s <==\n";
 100
 101 int tail_main(int argc, char **argv)
 102 {
 103         long count = 10;
 104         unsigned int sleep_period = 1;
 105         int from_top = 0;
 106         int follow = 0;
 107         int header_threshhold = 1;
 108         int count_bytes = 0;
 109
 110         char *tailbuf;
 111         size_t tailbufsize;
 112         int taillen = 0;
 113         int newline = 0;
 114
 115         int *fds, nfiles, nread, nwrite, seen, i, opt;
 116         char *s, *buf;
 117         const char *fmt;
 118
 119         /* Allow legacy syntax of an initial numeric option without -n. */
 120         if (argc >=2 && ((argv[1][0] == '+') || ((argv[1][0] == '-')
 121                         /* && (isdigit)(argv[1][1]) */
 122                         && (((unsigned int)(argv[1][1] - '0')) <= 9))))
 123         {
 124                 optind = 2;
 125                 optarg = argv[1];
 126                 goto GET_COUNT;
 127         }
 128
 129         while ((opt = getopt(argc, argv, tail_opts)) > 0) {
 130                 switch (opt) {
 131                         case 'f':
 132                                 follow = 1;
 133                                 break;
 134                         case 'c':
 135                                 count_bytes = 1;
 136                                 /* FALLS THROUGH */
 137                         case 'n':
 138                         GET_COUNT:
 139                                 count = bb_xgetlarg10_sfx(optarg, tail_suffixes);
 140                                 /* Note: Leading whitespace is an error trapped above. */
 141                                 if (*optarg == '+') {
 142                                         from_top = 1;
 143                                 } else {
 144                                         from_top = 0;
 145                                 }
 146                                 if (count < 0) {
 147                                         count = -count;
 148                                 }
 149                                 break;
 150 #ifdef CONFIG_FEATURE_FANCY_TAIL
 151                         case 'q':
 152                                 header_threshhold = INT_MAX;
 153                                 break;
 154                         case 's':
 155                                 sleep_period =bb_xgetularg10_bnd(optarg, 0, UINT_MAX);
 156                                 break;
 157                         case 'v':
 158                                 header_threshhold = 0;
 159                                 break;
 160 #endif
 161                         default:
 162                                 bb_show_usage();
 163                 }
 164         }
 165
 166         /* open all the files */
 167         fds = (int *)xmalloc(sizeof(int) * (argc - optind + 1));
 168
 169         argv += optind;
 170         nfiles = i = 0;
 171
 172         if ((argc -= optind) == 0) {
 173                 struct stat statbuf;
 174
 175                 if (!fstat(STDIN_FILENO, &statbuf) && S_ISFIFO(statbuf.st_mode)) {
 176                         follow = 0;
 177                 }
 178                 /* --argv; */
 179                 *argv = (char *) bb_msg_standard_input;
 180                 goto DO_STDIN;
 181         }
 182
 183         do {
 184                 if ((argv[i][0] == '-') && !argv[i][1]) {
 185                 DO_STDIN:
 186                         fds[nfiles] = STDIN_FILENO;
 187                 } else if ((fds[nfiles] = open(argv[i], O_RDONLY)) < 0) {
 188                         bb_perror_msg("%s", argv[i]);
 189                         status = EXIT_FAILURE;
 190                         continue;
 191                 }
 192                 argv[nfiles] = argv[i];
 193                 ++nfiles;
 194         } while (++i < argc);
 195
 196         if (!nfiles) {
 197                 bb_error_msg_and_die("no files");
 198         }
 199
 200         tailbufsize = BUFSIZ;
 201
 202         /* tail the files */
 203         if (from_top < count_bytes) {   /* Each is 0 or 1, so true iff 0 < 1. */
 204                 /* Hence, !from_top && count_bytes */
 205                 if (tailbufsize < count) {
 206                         tailbufsize = count + BUFSIZ;
 207                 }
 208         }
 209
 210         buf = tailbuf = xmalloc(tailbufsize);
 211
 212         fmt = header_fmt + 1;   /* Skip header leading newline on first output. */
 213         i = 0;
 214         do {
 215                 /* Be careful.  It would be possible to optimize the count-bytes
 216                  * case if the file is seekable.  If you do though, remember that
 217                  * starting file position may not be the beginning of the file.
 218                  * Beware of backing up too far.  See example in wc.c.
 219                  */
 220                 if ((!(count|from_top)) && (lseek(fds[i], 0, SEEK_END) >= 0)) {
 221                         continue;
 222                 }
 223
 224                 if (nfiles > header_threshhold) {
 225                         tail_xprint_header(fmt, argv[i]);
 226                         fmt = header_fmt;
 227                 }
 228
 229                 buf = tailbuf;
 230                 taillen = 0;
 231                 seen = 1;
 232                 newline = 0;
 233
 234                 while ((nread = tail_read(fds[i], buf, tailbufsize-taillen)) > 0) {
 235                         if (from_top) {
 236                                 nwrite = nread;
 237                                 if (seen < count) {
 238                                         if (count_bytes) {
 239                                                 nwrite -= (count - seen);
 240                                                 seen = count;
 241                                         } else {
 242                                                 s = buf;
 243                                                 do {
 244                                                         --nwrite;
 245                                                         if ((*s++ == '\n') && (++seen == count)) {
 246                                                                 break;
 247                                                         }
 248                                                 } while (nwrite);
 249                                         }
 250                                 }
 251                                 tail_xbb_full_write(buf + nread - nwrite, nwrite);
 252                         } else if (count) {
 253                                 if (count_bytes) {
 254                                         taillen += nread;
 255                                         if (taillen > count) {
 256                                                 memmove(tailbuf, tailbuf + taillen - count, count);
 257                                                 taillen = count;
 258                                         }
 259                                 } else {
 260                                         int k = nread;
 261                                         int nbuf = 0;
 262
 263                                         while (k) {
 264                                                 --k;
 265                                                 if (buf[k] == '\n') {
 266                                                         ++nbuf;
 267                                                 }
 268                                         }
 269
 270                                         if (newline + nbuf < count) {
 271                                                 newline += nbuf;
 272                                                 taillen += nread;
 273
 274                                         } else {
 275                                                 int extra = 0;
 276                                                 if (buf[nread-1] != '\n') {
 277                                                         extra = 1;
 278                                                 }
 279
 280                                                 k = newline + nbuf + extra - count;
 281                                                 s = tailbuf;
 282                                                 while (k) {
 283                                                         if (*s == '\n') {
 284                                                                 --k;
 285                                                         }
 286                                                         ++s;
 287                                                 }
 288
 289                                                 taillen += nread - (s - tailbuf);
 290                                                 memmove(tailbuf, s, taillen);
 291                                                 newline = count - extra;
 292                                         }
 293                                         if (tailbufsize < taillen + BUFSIZ) {
 294                                                 tailbufsize = taillen + BUFSIZ;
 295                                                 tailbuf = xrealloc(tailbuf, tailbufsize);
 296                                         }
 297                                 }
 298                                 buf = tailbuf + taillen;
 299                         }
 300                 }
 301
 302                 if (!from_top) {
 303                         tail_xbb_full_write(tailbuf, taillen);
 304                 }
 305
 306                 taillen = 0;
 307         } while (++i < nfiles);
 308
 309         buf = xrealloc(tailbuf, BUFSIZ);
 310
 311         fmt = NULL;
 312
 313         while (follow) {
 314                 sleep(sleep_period);
 315                 i = 0;
 316                 do {
 317                         if (nfiles > header_threshhold) {
 318                                 fmt = header_fmt;
 319                         }
 320                         while ((nread = tail_read(fds[i], buf, sizeof(buf))) > 0) {
 321                                 if (fmt) {
 322                                         tail_xprint_header(fmt, argv[i]);
 323                                         fmt = NULL;
 324                                 }
 325                                 tail_xbb_full_write(buf, nread);
 326                         }
 327                 } while (++i < nfiles);
 328         }
 329
 330         return status;
 331 }