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 1.17 2013/01/31 23:09:06 wiz 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 static void obsolete(char **);
  59 static void usage(void) __dead;
  60
  61 int
  62 main(int argc, char *argv[])
  63 {
  64         struct stat sb;
  65         FILE *fp;
  66         off_t off;
  67         enum STYLE style;
  68         int ch, first;
  69         char *p;
  70
  71         setprogname(argv[0]);
  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                 xerrx(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                 xerrx(1,
 137                     "-f and -F options only appropriate for a single file");
 138
 139         /*
 140          * If displaying in reverse, don't permit follow option, and convert
 141          * style values.
 142          */
 143         if (rflag) {
 144                 if (fflag)
 145                         usage();
 146                 if (style == FBYTES)
 147                         style = RBYTES;
 148                 else if (style == FLINES)
 149                         style = RLINES;
 150         }
 151
 152         /*
 153          * If style not specified, the default is the whole file for -r, and
 154          * the last 10 lines if not -r.
 155          */
 156         if (style == NOTSET) {
 157                 if (rflag) {
 158                         off = 0;
 159                         style = REVERSE;
 160                 } else {
 161                         off = 10;
 162                         style = RLINES;
 163                 }
 164         }
 165         if (*argv)
 166                 for (first = 1; (fname = *argv++) != NULL;) {
 167                         if ((fp = fopen(fname, "r")) == NULL ||
 168                             fstat(fileno(fp), &sb)) {
 169                                 ierr();
 170                                 continue;
 171                         }
 172                         if (argc > 1) {
 173                                 (void)printf("%s==> %s <==\n",
 174                                     first ? "" : "\n", fname);
 175                                 first = 0;
 176                                 (void)fflush(stdout);
 177                         }
 178
 179                         if (rflag)
 180                                 reverse(fp, style, off, &sb);
 181                         else
 182                                 forward(fp, style, off, &sb);
 183                         (void)fclose(fp);
 184                 }
 185         else {
 186                 fname = "stdin";
 187
 188                 if (fstat(fileno(stdin), &sb)) {
 189                         ierr();
 190                         exit(1);
 191                 }
 192
 193                 /*
 194                  * Determine if input is a pipe.  4.4BSD will set the SOCKET
 195                  * bit in the st_mode field for pipes.  Fix this then.
 196                  */
 197                 if (lseek(fileno(stdin), (off_t)0, SEEK_CUR) == -1 &&
 198                     errno == ESPIPE) {
 199                         errno = 0;
 200                         fflag = 0;              /* POSIX.2 requires this. */
 201                 }
 202
 203                 if (rflag)
 204                         reverse(stdin, style, off, &sb);
 205                 else
 206                         forward(stdin, style, off, &sb);
 207         }
 208         exit(rval);
 209 }
 210
 211 /*
 212  * Convert the obsolete argument form into something that getopt can handle.
 213  * This means that anything of the form [+-][0-9][0-9]*[lbc][fr] that isn't
 214  * the option argument for a -b, -c or -n option gets converted.
 215  */
 216 static void
 217 obsolete(char *argv[])
 218 {
 219         char *ap, *p, *t;
 220         int len;
 221         char *start;
 222
 223         while ((ap = *++argv) != NULL) {
 224                 /* Return if "--" or not an option of any form. */
 225                 if (ap[0] != '-') {
 226                         if (ap[0] != '+')
 227                                 return;
 228                 } else if (ap[1] == '-')
 229                         return;
 230
 231                 switch (*++ap) {
 232                 /* Old-style option. */
 233                 case '0': case '1': case '2': case '3': case '4':
 234                 case '5': case '6': case '7': case '8': case '9':
 235
 236                         /* Malloc space for dash, new option and argument. */
 237                         len = strlen(*argv);
 238                         if ((start = p = malloc(len + 3)) == NULL)
 239                                 xerr(1, "malloc");
 240                         *p++ = '-';
 241
 242                         /*
 243                          * Go to the end of the option argument.  Save off any
 244                          * trailing options (-3lf) and translate any trailing
 245                          * output style characters.
 246                          */
 247                         t = *argv + len - 1;
 248                         if (*t == 'f' || *t == 'r') {
 249                                 *p++ = *t;
 250                                 *t-- = '\0';
 251                         }
 252                         switch(*t) {
 253                         case 'b':
 254                                 *p++ = 'b';
 255                                 *t = '\0';
 256                                 break;
 257                         case 'c':
 258                                 *p++ = 'c';
 259                                 *t = '\0';
 260                                 break;
 261                         case 'l':
 262                                 *t = '\0';
 263                                 /* FALLTHROUGH */
 264                         case '0': case '1': case '2': case '3': case '4':
 265                         case '5': case '6': case '7': case '8': case '9':
 266                                 *p++ = 'n';
 267                                 break;
 268                         default:
 269                                 xerrx(1, "illegal option -- %s", *argv);
 270                         }
 271                         *p++ = *argv[0];
 272                         (void)strcpy(p, ap);
 273                         *argv = start;
 274                         continue;
 275
 276                 /*
 277                  * Options w/ arguments, skip the argument and continue
 278                  * with the next option.
 279                  */
 280                 case 'b':
 281                 case 'c':
 282                 case 'n':
 283                         if (!ap[1])
 284                                 ++argv;
 285                         /* FALLTHROUGH */
 286                 /* Options w/o arguments, continue with the next option. */
 287                 case 'f':
 288                 case 'r':
 289                         continue;
 290
 291                 /* Illegal option, return and let getopt handle it. */
 292                 default:
 293                         return;
 294                 }
 295         }
 296 }
 297
 298 static void
 299 usage(void)
 300 {
 301         (void)fprintf(stderr,
 302             "Usage: %s [-f | -F | -r] [-b # | -c # | -n #] [file ...]\n",
 303             getprogname());
 304         exit(1);
 305 }