usr.bin/tail/tail.c

   1 /*-
   2  * Copyright (c) 1991, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Edward Sze-Tyan Wang.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #include <sys/cdefs.h>
  34 #ifndef lint
  35 __COPYRIGHT("@(#) Copyright (c) 1991, 1993\
  36  The Regents of the University of California.  All rights reserved.");
  37 #endif /* not lint */
  38
  39 #ifndef lint
  40 #if 0
  41 static char sccsid[] = "@(#)tail.c      8.1 (Berkeley) 6/6/93";
  42 #endif
  43 __RCSID("$NetBSD: tail.c,v 1.13 2008/07/21 14:19:26 lukem Exp $");
  44 #endif /* not lint */
  45
  46 #include <sys/types.h>
  47 #include <sys/stat.h>
  48 #include <errno.h>
  49 #include <unistd.h>
  50 #include <stdio.h>
  51 #include <stdlib.h>
  52 #include <string.h>
  53 #include "extern.h"
  54
  55 int fflag, rflag, rval;
  56 const char *fname;
  57
  58 int     main(int, char **);
  59 static void obsolete(char **);
  60 static void usage(void);
  61
  62 int
  63 main(int argc, char *argv[])
  64 {
  65         struct stat sb;
  66         FILE *fp;
  67         off_t off;
  68         enum STYLE style;
  69         int ch, first;
  70         char *p;
  71
  72         off = 0;
  73         /*
  74          * Tail's options are weird.  First, -n10 is the same as -n-10, not
  75          * -n+10.  Second, the number options are 1 based and not offsets,
  76          * so -n+1 is the first line, and -c-1 is the last byte.  Third, the
  77          * number options for the -r option specify the number of things that
  78          * get displayed, not the starting point in the file.  The one major
  79          * incompatibility in this version as compared to historical versions
  80          * is that the 'r' option couldn't be modified by the -lbc options,
  81          * i.e. it was always done in lines.  This version treats -rc as a
  82          * number of characters in reverse order.  Finally, the default for
  83          * -r is the entire file, not 10 lines.
  84          */
  85 #define ARG(units, forward, backward) {                                 \
  86         if (style)                                                      \
  87                 usage();                                                \
  88         off = strtoll(optarg, &p, 10) * (units);                        \
  89         if (*p)                                                         \
  90                 err(1, "illegal offset -- %s", optarg);                 \
  91         switch(optarg[0]) {                                             \
  92         case '+':                                                       \
  93                 if (off)                                                \
  94                         off -= (units);                                 \
  95                         style = (forward);                              \
  96                 break;                                                  \
  97         case '-':                                                       \
  98                 off = -off;                                             \
  99                 /* FALLTHROUGH */                                       \
 100         default:                                                        \
 101                 style = (backward);                                     \
 102                 break;                                                  \
 103         }                                                               \
 104 }
 105
 106         obsolete(argv);
 107         style = NOTSET;
 108         while ((ch = getopt(argc, argv, "Fb:c:fn:r")) != -1)
 109                 switch(ch) {
 110                 case 'F':
 111                         fflag = 2;
 112                         break;
 113                 case 'b':
 114                         ARG(512, FBYTES, RBYTES);
 115                         break;
 116                 case 'c':
 117                         ARG(1, FBYTES, RBYTES);
 118                         break;
 119                 case 'f':
 120                         fflag = 1;
 121                         break;
 122                 case 'n':
 123                         ARG(1, FLINES, RLINES);
 124                         break;
 125                 case 'r':
 126                         rflag = 1;
 127                         break;
 128                 case '?':
 129                 default:
 130                         usage();
 131                 }
 132         argc -= optind;
 133         argv += optind;
 134
 135         if (fflag && argc > 1)
 136                 err(1, "-f and -F options only appropriate for a single file");
 137
 138         /*
 139          * If displaying in reverse, don't permit follow option, and convert
 140          * style values.
 141          */
 142         if (rflag) {
 143                 if (fflag)
 144                         usage();
 145                 if (style == FBYTES)
 146                         style = RBYTES;
 147                 else if (style == FLINES)
 148                         style = RLINES;
 149         }
 150
 151         /*
 152          * If style not specified, the default is the whole file for -r, and
 153          * the last 10 lines if not -r.
 154          */
 155         if (style == NOTSET) {
 156                 if (rflag) {
 157                         off = 0;
 158                         style = REVERSE;
 159                 } else {
 160                         off = 10;
 161                         style = RLINES;
 162                 }
 163         }
 164         if (*argv)
 165                 for (first = 1; (fname = *argv++) != NULL;) {
 166                         if ((fp = fopen(fname, "r")) == NULL ||
 167                             fstat(fileno(fp), &sb)) {
 168                                 ierr();
 169                                 continue;
 170                         }
 171                         if (argc > 1) {
 172                                 (void)printf("%s==> %s <==\n",
 173                                     first ? "" : "\n", fname);
 174                                 first = 0;
 175                                 (void)fflush(stdout);
 176                         }
 177
 178                         if (rflag)
 179                                 reverse(fp, style, off, &sb);
 180                         else
 181                                 forward(fp, style, off, &sb);
 182                         (void)fclose(fp);
 183                 }
 184         else {
 185                 fname = "stdin";
 186
 187                 if (fstat(fileno(stdin), &sb)) {
 188                         ierr();
 189                         exit(1);
 190                 }
 191
 192                 /*
 193                  * Determine if input is a pipe.  4.4BSD will set the SOCKET
 194                  * bit in the st_mode field for pipes.  Fix this then.
 195                  */
 196                 if (lseek(fileno(stdin), (off_t)0, SEEK_CUR) == -1 &&
 197                     errno == ESPIPE) {
 198                         errno = 0;
 199                         fflag = 0;              /* POSIX.2 requires this. */
 200                 }
 201
 202                 if (rflag)
 203                         reverse(stdin, style, off, &sb);
 204                 else
 205                         forward(stdin, style, off, &sb);
 206         }
 207         exit(rval);
 208 }
 209
 210 /*
 211  * Convert the obsolete argument form into something that getopt can handle.
 212  * This means that anything of the form [+-][0-9][0-9]*[lbc][fr] that isn't
 213  * the option argument for a -b, -c or -n option gets converted.
 214  */
 215 static void
 216 obsolete(char *argv[])
 217 {
 218         char *ap, *p, *t;
 219         int len;
 220         char *start;
 221
 222         while ((ap = *++argv) != NULL) {
 223                 /* Return if "--" or not an option of any form. */
 224                 if (ap[0] != '-') {
 225                         if (ap[0] != '+')
 226                                 return;
 227                 } else if (ap[1] == '-')
 228                         return;
 229
 230                 switch (*++ap) {
 231                 /* Old-style option. */
 232                 case '0': case '1': case '2': case '3': case '4':
 233                 case '5': case '6': case '7': case '8': case '9':
 234
 235                         /* Malloc space for dash, new option and argument. */
 236                         len = strlen(*argv);
 237                         if ((start = p = malloc(len + 3)) == NULL)
 238                                 err(1, "%s", strerror(errno));
 239                         *p++ = '-';
 240
 241                         /*
 242                          * Go to the end of the option argument.  Save off any
 243                          * trailing options (-3lf) and translate any trailing
 244                          * output style characters.
 245                          */
 246                         t = *argv + len - 1;
 247                         if (*t == 'f' || *t == 'r') {
 248                                 *p++ = *t;
 249                                 *t-- = '\0';
 250                         }
 251                         switch(*t) {
 252                         case 'b':
 253                                 *p++ = 'b';
 254                                 *t = '\0';
 255                                 break;
 256                         case 'c':
 257                                 *p++ = 'c';
 258                                 *t = '\0';
 259                                 break;
 260                         case 'l':
 261                                 *t = '\0';
 262                                 /* FALLTHROUGH */
 263                         case '0': case '1': case '2': case '3': case '4':
 264                         case '5': case '6': case '7': case '8': case '9':
 265                                 *p++ = 'n';
 266                                 break;
 267                         default:
 268                                 err(1, "illegal option -- %s", *argv);
 269                         }
 270                         *p++ = *argv[0];
 271                         (void)strcpy(p, ap);
 272                         *argv = start;
 273                         continue;
 274
 275                 /*
 276                  * Options w/ arguments, skip the argument and continue
 277                  * with the next option.
 278                  */
 279                 case 'b':
 280                 case 'c':
 281                 case 'n':
 282                         if (!ap[1])
 283                                 ++argv;
 284                         /* FALLTHROUGH */
 285                 /* Options w/o arguments, continue with the next option. */
 286                 case 'f':
 287                 case 'r':
 288                         continue;
 289
 290                 /* Illegal option, return and let getopt handle it. */
 291                 default:
 292                         return;
 293                 }
 294         }
 295 }
 296
 297 static void
 298 usage(void)
 299 {
 300         (void)fprintf(stderr,
 301             "usage: tail [-f | -F | -r] [-b # | -c # | -n #] [file ...]\n");
 302         exit(1);
 303 }