coreutils/tail.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * Mini tail implementation for busybox
   4  *
   5  *
   6  * Copyright (C) 2001 by Matt Kraai <kraai@alumni.carnegiemellon.edu>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16  * General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  21  *
  22  */
  23
  24 #include "busybox.h"
  25
  26 #include <sys/types.h>
  27 #include <fcntl.h>
  28
  29 static struct suffix_mult tail_suffixes[] = {
  30         { "b", 512 },
  31         { "k", 1024 },
  32         { "m", 1048576 },
  33         { NULL, 0 }
  34 };
  35
  36 #ifndef BB_FEATURE_SIMPLE_TAIL
  37 static struct suffix_mult null_suffixes[] = {
  38         { NULL, 0 }
  39 };
  40 #endif
  41
  42 #define BYTES 0
  43 #define LINES 1
  44
  45 static char *tailbuf;
  46 static int taillen;
  47 static int newline;
  48
  49 void tailbuf_append(char *buf, int len)
  50 {
  51         tailbuf = xrealloc(tailbuf, taillen + len);
  52         memcpy(tailbuf + taillen, buf, len);
  53         taillen += len;
  54 }
  55
  56 void tailbuf_trunc()
  57 {
  58         char *s;
  59         s = memchr(tailbuf, '\n', taillen);
  60         memmove(tailbuf, s + 1, taillen - ((s + 1) - tailbuf));
  61         taillen -= (s + 1) - tailbuf;
  62         newline = 0;
  63 }
  64
  65 int tail_main(int argc, char **argv)
  66 {
  67         int from_top = 0, units = LINES, count = 10, sleep_period = 1;
  68         int show_headers = 0, hide_headers = 0, follow = 0;
  69         int *fds, nfiles = 0, status = EXIT_SUCCESS, nread, nwrite, seen = 0;
  70         char *s, *start, *end, buf[BUFSIZ];
  71         int i, opt;
  72
  73         while ((opt = getopt(argc, argv, "c:fhn:q:s:v")) > 0) {
  74                 switch (opt) {
  75                         case 'f':
  76                                 follow = 1;
  77                                 break;
  78 #ifndef BB_FEATURE_SIMPLE_TAIL
  79                         case 'c':
  80                                 units = BYTES;
  81                                 /* FALLS THROUGH */
  82 #endif
  83                         case 'n':
  84                                 count = parse_number(optarg, tail_suffixes);
  85                                 if (count < 0)
  86                                         count = -count;
  87                                 if (optarg[0] == '+')
  88                                         from_top = 1;
  89                                 break;
  90 #ifndef BB_FEATURE_SIMPLE_TAIL
  91                         case 'q':
  92                                 hide_headers = 1;
  93                                 break;
  94                         case 's':
  95                                 sleep_period = parse_number(optarg, null_suffixes);
  96                                 break;
  97                         case 'v':
  98                                 show_headers = 1;
  99                                 break;
 100 #endif
 101                         default:
 102                                 usage(tail_usage);
 103                 }
 104         }
 105
 106         /* open all the files */
 107         fds = (int *)xmalloc(sizeof(int) * (argc - optind + 1));
 108         if (argc == optind) {
 109                 fds[nfiles++] = STDIN_FILENO;
 110                 argv[optind] = "standard input";
 111         } else {
 112                 for (i = optind; i < argc; i++) {
 113                         if (strcmp(argv[i], "-") == 0) {
 114                                 fds[nfiles++] = STDIN_FILENO;
 115                                 argv[i] = "standard input";
 116                         } else if ((fds[nfiles++] = open(argv[i], O_RDONLY)) < 0) {
 117                                 perror_msg("%s", argv[i]);
 118                                 status = EXIT_FAILURE;
 119                         }
 120                 }
 121         }
 122
 123 #ifndef BB_FEATURE_SIMPLE_TAIL
 124         /* tail the files */
 125         if (!from_top && units == BYTES)
 126                 tailbuf = xmalloc(count);
 127 #endif
 128
 129         for (i = 0; i < nfiles; i++) {
 130                 if (fds[i] == -1)
 131                         continue;
 132                 seen = 0;
 133                 if (show_headers || (!hide_headers && nfiles > 1))
 134                         printf("%s==> %s <==\n", i == 0 ? "" : "\n", argv[optind + i]);
 135                 while ((nread = safe_read(fds[i], buf, sizeof(buf))) > 0) {
 136                         if (from_top) {
 137 #ifndef BB_FEATURE_SIMPLE_TAIL
 138                                 if (units == BYTES) {
 139                                         if (count - 1 <= seen)
 140                                                 nwrite = nread;
 141                                         else if (count - 1 <= seen + nread)
 142                                                 nwrite = nread + seen - (count - 1);
 143                                         else
 144                                                 nwrite = 0;
 145                                         seen += nread;
 146                                 } else {
 147 #else
 148                                 {
 149 #endif
 150                                         if (count - 1 <= seen)
 151                                                 nwrite = nread;
 152                                         else {
 153                                                 nwrite = 0;
 154                                                 for (s = memchr(buf, '\n', nread); s != NULL;
 155                                                                 s = memchr(s+1, '\n', nread - (s + 1 - buf))) {
 156                                                         if (count - 1 <= ++seen) {
 157                                                                 nwrite = nread - (s + 1 - buf);
 158                                                                 break;
 159                                                         }
 160                                                 }
 161                                         }
 162                                 }
 163                                 if (full_write(STDOUT_FILENO, buf + nread - nwrite,
 164                                                         nwrite) < 0) {
 165                                         perror_msg("write");
 166                                         status = EXIT_FAILURE;
 167                                         break;
 168                                 }
 169                         } else {
 170 #ifndef BB_FEATURE_SIMPLE_TAIL
 171                                 if (units == BYTES) {
 172                                         if (nread < count) {
 173                                                 memmove(tailbuf, tailbuf + nread, count - nread);
 174                                                 memcpy(tailbuf + count - nread, buf, nread);
 175                                         } else {
 176                                                 memcpy(tailbuf, buf + nread - count, count);
 177                                         }
 178                                         seen += nread;
 179                                 } else {
 180 #else
 181                                 {
 182 #endif
 183                                         for (start = buf, end = memchr(buf, '\n', nread);
 184                                                         end != NULL; start = end+1,
 185                                                         end = memchr(start, '\n', nread - (start - buf))) {
 186                                                 if (newline && count <= seen)
 187                                                         tailbuf_trunc();
 188                                                 tailbuf_append(start, end - start + 1);
 189                                                 seen++;
 190                                                 newline = 1;
 191                                         }
 192                                         if (newline && count <= seen && nread - (start - buf) > 0)
 193                                                 tailbuf_trunc();
 194                                         tailbuf_append(start, nread - (start - buf));
 195                                 }
 196                         }
 197                 }
 198
 199                 if (nread < 0) {
 200                         perror_msg("read");
 201                         status = EXIT_FAILURE;
 202                 }
 203
 204 #ifndef BB_FEATURE_SIMPLE_TAIL
 205                 if (!from_top && units == BYTES) {
 206                         if (count < seen)
 207                                 seen = count;
 208                         if (full_write(STDOUT_FILENO, tailbuf + count - seen, seen) < 0) {
 209                                 perror_msg("write");
 210                                 status = EXIT_FAILURE;
 211                         }
 212                 }
 213 #endif
 214
 215                 if (!from_top && units == LINES) {
 216                         if (full_write(STDOUT_FILENO, tailbuf, taillen) < 0) {
 217                                 perror_msg("write");
 218                                 status = EXIT_FAILURE;
 219                         }
 220                 }
 221
 222                 taillen = 0;
 223         }
 224
 225         while (follow) {
 226                 sleep(sleep_period);
 227
 228                 for (i = 0; i < nfiles; i++) {
 229                         if (fds[i] == -1)
 230                                 continue;
 231
 232                         if ((nread = safe_read(fds[i], buf, sizeof(buf))) > 0) {
 233                                 if (show_headers || (!hide_headers && nfiles > 1))
 234                                         printf("\n==> %s <==\n", argv[optind + i]);
 235
 236                                 do {
 237                                         full_write(STDOUT_FILENO, buf, nread);
 238                                 } while ((nread = safe_read(fds[i], buf, sizeof(buf))) > 0);
 239                         }
 240
 241                         if (nread < 0) {
 242                                 perror_msg("read");
 243                                 status = EXIT_FAILURE;
 244                         }
 245                 }
 246         }
 247
 248         return status;
 249 }