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) {
  73                 int line_num;
  74                 switch (argv[1][0]) {
  75                         case '+':
  76                                 from_top = 1;
  77                                 /* FALLS THROUGH */
  78                         case '-':
  79                                 line_num = atoi(&argv[1][1]);
  80                                 if (line_num != 0) {
  81                                         optind = 2;
  82                                         count = line_num;
  83                                 }
  84                                 break;
  85                 }
  86         }
  87
  88 #ifdef CONFIG_FEATURE_FANCY_TAIL
  89         while ((opt = getopt(argc, argv, "c:fn:q:s:v")) > 0) {
  90 #else
  91         while ((opt = getopt(argc, argv, "fn:")) > 0) {
  92 #endif
  93                 switch (opt) {
  94                         case 'f':
  95                                 follow = 1;
  96                                 break;
  97 #ifdef CONFIG_FEATURE_FANCY_TAIL
  98                         case 'c':
  99                                 units = BYTES;
 100                                 /* FALLS THROUGH */
 101 #endif
 102                         case 'n':
 103                                 count = parse_number(optarg, tail_suffixes);
 104                                 if (count < 0)
 105                                         count = -count;
 106                                 if (optarg[0] == '+')
 107                                         from_top = 1;
 108                                 break;
 109 #ifdef CONFIG_FEATURE_FANCY_TAIL
 110                         case 'q':
 111                                 hide_headers = 1;
 112                                 break;
 113                         case 's':
 114                                 sleep_period = parse_number(optarg, 0);
 115                                 break;
 116                         case 'v':
 117                                 show_headers = 1;
 118                                 break;
 119 #endif
 120                         default:
 121                                 show_usage();
 122                 }
 123         }
 124
 125         /* open all the files */
 126         fds = (int *)xmalloc(sizeof(int) * (argc - optind + 1));
 127         if (argc == optind) {
 128                 fds[nfiles++] = STDIN_FILENO;
 129                 argv[optind] = "standard input";
 130         } else {
 131                 for (i = optind; i < argc; i++) {
 132                         if (strcmp(argv[i], "-") == 0) {
 133                                 fds[nfiles++] = STDIN_FILENO;
 134                                 argv[i] = "standard input";
 135                         } else if ((fds[nfiles++] = open(argv[i], O_RDONLY)) < 0) {
 136                                 perror_msg("%s", argv[i]);
 137                                 status = EXIT_FAILURE;
 138                         }
 139                 }
 140         }
 141
 142 #ifdef CONFIG_FEATURE_FANCY_TAIL
 143         /* tail the files */
 144         if (!from_top && units == BYTES)
 145                 tailbuf = xmalloc(count);
 146 #endif
 147
 148         for (i = 0; i < nfiles; i++) {
 149                 if (fds[i] == -1)
 150                         continue;
 151                 if (!count) {
 152                         lseek(fds[i], 0, SEEK_END);
 153                         continue;
 154                 }
 155                 seen = 0;
 156                 if (show_headers || (!hide_headers && nfiles > 1))
 157                         printf("%s==> %s <==\n", i == 0 ? "" : "\n", argv[optind + i]);
 158                 while ((nread = safe_read(fds[i], buf, sizeof(buf))) > 0) {
 159                         if (from_top) {
 160 #ifdef CONFIG_FEATURE_FANCY_TAIL
 161                                 if (units == BYTES) {
 162                                         if (count - 1 <= seen)
 163                                                 nwrite = nread;
 164                                         else if (count - 1 <= seen + nread)
 165                                                 nwrite = nread + seen - (count - 1);
 166                                         else
 167                                                 nwrite = 0;
 168                                         seen += nread;
 169                                 } else {
 170 #else
 171                                 {
 172 #endif
 173                                         if (count - 1 <= seen)
 174                                                 nwrite = nread;
 175                                         else {
 176                                                 nwrite = 0;
 177                                                 for (s = memchr(buf, '\n', nread); s != NULL;
 178                                                                 s = memchr(s+1, '\n', nread - (s + 1 - buf))) {
 179                                                         if (count - 1 <= ++seen) {
 180                                                                 nwrite = nread - (s + 1 - buf);
 181                                                                 break;
 182                                                         }
 183                                                 }
 184                                         }
 185                                 }
 186                                 if (full_write(STDOUT_FILENO, buf + nread - nwrite,
 187                                                         nwrite) < 0) {
 188                                         perror_msg("write");
 189                                         status = EXIT_FAILURE;
 190                                         break;
 191                                 }
 192                         } else {
 193 #ifdef CONFIG_FEATURE_FANCY_TAIL
 194                                 if (units == BYTES) {
 195                                         if (nread < count) {
 196                                                 memmove(tailbuf, tailbuf + nread, count - nread);
 197                                                 memcpy(tailbuf + count - nread, buf, nread);
 198                                         } else {
 199                                                 memcpy(tailbuf, buf + nread - count, count);
 200                                         }
 201                                         seen += nread;
 202                                 } else {
 203 #else
 204                                 {
 205 #endif
 206                                         for (start = buf, end = memchr(buf, '\n', nread);
 207                                                         end != NULL; start = end+1,
 208                                                         end = memchr(start, '\n', nread - (start - buf))) {
 209                                                 if (newline && count <= seen)
 210                                                         tailbuf_trunc();
 211                                                 tailbuf_append(start, end - start + 1);
 212                                                 seen++;
 213                                                 newline = 1;
 214                                         }
 215                                         if (newline && count <= seen && nread - (start - buf) > 0)
 216                                                 tailbuf_trunc();
 217                                         tailbuf_append(start, nread - (start - buf));
 218                                 }
 219                         }
 220                 }
 221
 222                 if (nread < 0) {
 223                         perror_msg("read");
 224                         status = EXIT_FAILURE;
 225                 }
 226
 227 #ifdef CONFIG_FEATURE_FANCY_TAIL
 228                 if (!from_top && units == BYTES) {
 229                         if (count < seen)
 230                                 seen = count;
 231                         if (full_write(STDOUT_FILENO, tailbuf + count - seen, seen) < 0) {
 232                                 perror_msg("write");
 233                                 status = EXIT_FAILURE;
 234                         }
 235                 }
 236 #endif
 237
 238                 if (!from_top && units == LINES) {
 239                         if (full_write(STDOUT_FILENO, tailbuf, taillen) < 0) {
 240                                 perror_msg("write");
 241                                 status = EXIT_FAILURE;
 242                         }
 243                 }
 244
 245                 taillen = 0;
 246         }
 247
 248         while (follow) {
 249                 sleep(sleep_period);
 250
 251                 for (i = 0; i < nfiles; i++) {
 252                         if (fds[i] == -1)
 253                                 continue;
 254
 255                         if ((nread = safe_read(fds[i], buf, sizeof(buf))) > 0) {
 256                                 if (show_headers || (!hide_headers && nfiles > 1))
 257                                         printf("\n==> %s <==\n", argv[optind + i]);
 258
 259                                 do {
 260                                         full_write(STDOUT_FILENO, buf, nread);
 261                                 } while ((nread = safe_read(fds[i], buf, sizeof(buf))) > 0);
 262                         }
 263
 264                         if (nread < 0) {
 265                                 perror_msg("read");
 266                                 status = EXIT_FAILURE;
 267                         }
 268                 }
 269         }
 270
 271         return status;
 272 }