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
  25 #include <fcntl.h>
  26 #include <getopt.h>
  27 #include <string.h>
  28 #include <ctype.h>
  29 #include <stdlib.h>
  30 #include <unistd.h>
  31 #include <sys/types.h>
  32 #include "busybox.h"
  33
  34 static const struct suffix_mult tail_suffixes[] = {
  35         { "b", 512 },
  36         { "k", 1024 },
  37         { "m", 1048576 },
  38         { NULL, 0 }
  39 };
  40
  41 static const int BYTES = 0;
  42 static const int LINES = 1;
  43
  44 static char *tailbuf;
  45 static int taillen;
  46 static int newline;
  47
  48 static void tailbuf_append(char *buf, int len)
  49 {
  50         tailbuf = xrealloc(tailbuf, taillen + len);
  51         memcpy(tailbuf + taillen, buf, len);
  52         taillen += len;
  53 }
  54
  55 static void tailbuf_trunc(void)
  56 {
  57         char *s;
  58         s = memchr(tailbuf, '\n', taillen);
  59         memmove(tailbuf, s + 1, taillen - ((s + 1) - tailbuf));
  60         taillen -= (s + 1) - tailbuf;
  61         newline = 0;
  62 }
  63
  64 int tail_main(int argc, char **argv)
  65 {
  66         int from_top = 0, units = LINES, count = 10, sleep_period = 1;
  67         int show_headers = 0, hide_headers = 0, follow = 0;
  68         int *fds, nfiles = 0, status = EXIT_SUCCESS, nread, nwrite, seen = 0;
  69         char *s, *start, *end, buf[BUFSIZ];
  70         int i, opt;
  71
  72         if (( argc >= 2 ) && ( argv [1][0] == '-' ) && isdigit ( argv [1][1] )) {
  73                 count = atoi ( &argv [1][1] );
  74                 optind = 2;
  75         }
  76
  77         while ((opt = getopt(argc, argv, "c:fhn:q:s:v")) > 0) {
  78                 switch (opt) {
  79                         case 'f':
  80                                 follow = 1;
  81                                 break;
  82 #ifdef CONFIG_FEATURE_FANCY_TAIL
  83                         case 'c':
  84                                 units = BYTES;
  85                                 /* FALLS THROUGH */
  86 #endif
  87                         case 'n':
  88                                 count = parse_number(optarg, tail_suffixes);
  89                                 if (count < 0)
  90                                         count = -count;
  91                                 if (optarg[0] == '+')
  92                                         from_top = 1;
  93                                 break;
  94 #ifdef CONFIG_FEATURE_FANCY_TAIL
  95                         case 'q':
  96                                 hide_headers = 1;
  97                                 break;
  98                         case 's':
  99                                 sleep_period = parse_number(optarg, 0);
 100                                 break;
 101                         case 'v':
 102                                 show_headers = 1;
 103                                 break;
 104 #endif
 105                         default:
 106                                 show_usage();
 107                 }
 108         }
 109
 110         /* open all the files */
 111         fds = (int *)xmalloc(sizeof(int) * (argc - optind + 1));
 112         if (argc == optind) {
 113                 fds[nfiles++] = STDIN_FILENO;
 114                 argv[optind] = "standard input";
 115         } else {
 116                 for (i = optind; i < argc; i++) {
 117                         if (strcmp(argv[i], "-") == 0) {
 118                                 fds[nfiles++] = STDIN_FILENO;
 119                                 argv[i] = "standard input";
 120                         } else if ((fds[nfiles++] = open(argv[i], O_RDONLY)) < 0) {
 121                                 perror_msg("%s", argv[i]);
 122                                 status = EXIT_FAILURE;
 123                         }
 124                 }
 125         }
 126
 127 #ifdef CONFIG_FEATURE_FANCY_TAIL
 128         /* tail the files */
 129         if (!from_top && units == BYTES)
 130                 tailbuf = xmalloc(count);
 131 #endif
 132
 133         for (i = 0; i < nfiles; i++) {
 134                 if (fds[i] == -1)
 135                         continue;
 136                 if (!count) {
 137                         lseek(fds[i], 0, SEEK_END);
 138                         continue;
 139                 }
 140                 seen = 0;
 141                 if (show_headers || (!hide_headers && nfiles > 1))
 142                         printf("%s==> %s <==\n", i == 0 ? "" : "\n", argv[optind + i]);
 143                 while ((nread = safe_read(fds[i], buf, sizeof(buf))) > 0) {
 144                         if (from_top) {
 145 #ifdef CONFIG_FEATURE_FANCY_TAIL
 146                                 if (units == BYTES) {
 147                                         if (count - 1 <= seen)
 148                                                 nwrite = nread;
 149                                         else if (count - 1 <= seen + nread)
 150                                                 nwrite = nread + seen - (count - 1);
 151                                         else
 152                                                 nwrite = 0;
 153                                         seen += nread;
 154                                 } else {
 155 #else
 156                                 {
 157 #endif
 158                                         if (count - 1 <= seen)
 159                                                 nwrite = nread;
 160                                         else {
 161                                                 nwrite = 0;
 162                                                 for (s = memchr(buf, '\n', nread); s != NULL;
 163                                                                 s = memchr(s+1, '\n', nread - (s + 1 - buf))) {
 164                                                         if (count - 1 <= ++seen) {
 165                                                                 nwrite = nread - (s + 1 - buf);
 166                                                                 break;
 167                                                         }
 168                                                 }
 169                                         }
 170                                 }
 171                                 if (full_write(STDOUT_FILENO, buf + nread - nwrite,
 172                                                         nwrite) < 0) {
 173                                         perror_msg("write");
 174                                         status = EXIT_FAILURE;
 175                                         break;
 176                                 }
 177                         } else {
 178 #ifdef CONFIG_FEATURE_FANCY_TAIL
 179                                 if (units == BYTES) {
 180                                         if (nread < count) {
 181                                                 memmove(tailbuf, tailbuf + nread, count - nread);
 182                                                 memcpy(tailbuf + count - nread, buf, nread);
 183                                         } else {
 184                                                 memcpy(tailbuf, buf + nread - count, count);
 185                                         }
 186                                         seen += nread;
 187                                 } else {
 188 #else
 189                                 {
 190 #endif
 191                                         for (start = buf, end = memchr(buf, '\n', nread);
 192                                                         end != NULL; start = end+1,
 193                                                         end = memchr(start, '\n', nread - (start - buf))) {
 194                                                 if (newline && count <= seen)
 195                                                         tailbuf_trunc();
 196                                                 tailbuf_append(start, end - start + 1);
 197                                                 seen++;
 198                                                 newline = 1;
 199                                         }
 200                                         if (newline && count <= seen && nread - (start - buf) > 0)
 201                                                 tailbuf_trunc();
 202                                         tailbuf_append(start, nread - (start - buf));
 203                                 }
 204                         }
 205                 }
 206
 207                 if (nread < 0) {
 208                         perror_msg("read");
 209                         status = EXIT_FAILURE;
 210                 }
 211
 212 #ifdef CONFIG_FEATURE_FANCY_TAIL
 213                 if (!from_top && units == BYTES) {
 214                         if (count < seen)
 215                                 seen = count;
 216                         if (full_write(STDOUT_FILENO, tailbuf + count - seen, seen) < 0) {
 217                                 perror_msg("write");
 218                                 status = EXIT_FAILURE;
 219                         }
 220                 }
 221 #endif
 222
 223                 if (!from_top && units == LINES) {
 224                         if (full_write(STDOUT_FILENO, tailbuf, taillen) < 0) {
 225                                 perror_msg("write");
 226                                 status = EXIT_FAILURE;
 227                         }
 228                 }
 229
 230                 taillen = 0;
 231         }
 232
 233         while (follow) {
 234                 sleep(sleep_period);
 235
 236                 for (i = 0; i < nfiles; i++) {
 237                         if (fds[i] == -1)
 238                                 continue;
 239
 240                         if ((nread = safe_read(fds[i], buf, sizeof(buf))) > 0) {
 241                                 if (show_headers || (!hide_headers && nfiles > 1))
 242                                         printf("\n==> %s <==\n", argv[optind + i]);
 243
 244                                 do {
 245                                         full_write(STDOUT_FILENO, buf, nread);
 246                                 } while ((nread = safe_read(fds[i], buf, sizeof(buf))) > 0);
 247                         }
 248
 249                         if (nread < 0) {
 250                                 perror_msg("read");
 251                                 status = EXIT_FAILURE;
 252                         }
 253                 }
 254         }
 255
 256         return status;
 257 }