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