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  * 4. 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  * @(#) Copyright (c) 1991, 1993 The Regents of the University of California.  All rights reserved.
  33  * @(#)tail.c   8.1 (Berkeley) 6/6/93
  34  * $FreeBSD: src/usr.bin/tail/tail.c,v 1.6.2.2 2001/12/19 20:29:31 iedowse Exp $
  35  * $DragonFly: src/usr.bin/tail/tail.c,v 1.6 2005/03/01 21:37:33 cpressey Exp $
  36  */
  37
  38 #include <sys/types.h>
  39 #include <sys/stat.h>
  40 #include <errno.h>
  41 #include <unistd.h>
  42 #include <stdio.h>
  43 #include <stdlib.h>
  44 #include <string.h>
  45 #include <err.h>
  46 #include "extern.h"
  47
  48 int Fflag, fflag, rflag, rval, no_files;
  49 const char *fname;
  50
  51 file_info_t *files;
  52
  53 static void obsolete(char **);
  54 static void usage(void);
  55 static void getarg(int, enum STYLE, enum STYLE, enum STYLE *, int *, off_t *);
  56
  57 int
  58 main(int argc, char **argv)
  59 {
  60         struct stat sb;
  61         FILE *fp;
  62         off_t off = 0;
  63         enum STYLE style;
  64         int style_set;
  65         int i, ch;
  66         file_info_t *file;
  67
  68         obsolete(argv);
  69         style_set = 0;
  70         while ((ch = getopt(argc, argv, "Fb:c:fn:r")) != -1)
  71                 switch(ch) {
  72                 case 'F':       /* -F is superset of (and implies) -f */
  73                         Fflag = fflag = 1;
  74                         break;
  75                 case 'b':
  76                         getarg(512, FBYTES, RBYTES, &style, &style_set, &off);
  77                         break;
  78                 case 'c':
  79                         getarg(1, FBYTES, RBYTES, &style, &style_set, &off);
  80                         break;
  81                 case 'f':
  82                         fflag = 1;
  83                         break;
  84                 case 'n':
  85                         getarg(1, FLINES, RLINES, &style, &style_set, &off);
  86                         break;
  87                 case 'r':
  88                         rflag = 1;
  89                         break;
  90                 case '?':
  91                 default:
  92                         usage();
  93                 }
  94         argc -= optind;
  95         argv += optind;
  96
  97         no_files = argc ? argc : 1;
  98
  99         /*
 100          * If displaying in reverse, don't permit follow option, and convert
 101          * style values.
 102          */
 103         if (rflag) {
 104                 if (fflag)
 105                         usage();
 106                 if (style == FBYTES)
 107                         style = RBYTES;
 108                 else if (style == FLINES)
 109                         style = RLINES;
 110         }
 111
 112         /*
 113          * If style not specified, the default is the whole file for -r, and
 114          * the last 10 lines if not -r.
 115          */
 116         if (!style_set) {
 117                 if (rflag) {
 118                         off = 0;
 119                         style = REVERSE;
 120                 } else {
 121                         off = 10;
 122                         style = RLINES;
 123                 }
 124         }
 125
 126         if (*argv && fflag) {
 127                 files = malloc(no_files * sizeof(struct file_info));
 128                 if (files == NULL)
 129                         err(1, "Couldn't malloc space for files descriptors.");
 130
 131                 for (file = files; (fname = *argv++) != NULL; file++) {
 132                         file->file_name = strdup(fname);
 133                         if (! file->file_name)
 134                                 errx(1, "Couldn't alloc space for file name.");
 135                         file->fp = fopen(file->file_name, "r");
 136                         if (file->fp == NULL ||
 137                             fstat(fileno(file->fp), &file->st) == -1) {
 138                                 file->fp = NULL;
 139                                 ierr();
 140                                 continue;
 141                         }
 142                 }
 143                 follow(files, style, off);
 144                 for (i = 0, file = files; i < no_files; i++, file++)
 145                         free(file->file_name);
 146                 free(files);
 147         } else if (*argv) {
 148                 for (i = 0; (fname = *argv++) != NULL; ++i) {
 149                         if ((fp = fopen(fname, "r")) == NULL ||
 150                             fstat(fileno(fp), &sb)) {
 151                                 ierr();
 152                                 continue;
 153                         }
 154                         if (argc > 1) {
 155                                 showfilename(i, fname);
 156                                 (void)fflush(stdout);
 157                         }
 158
 159                         if (rflag)
 160                                 reverse(fp, style, off, &sb);
 161                         else
 162                                 forward(fp, style, off, &sb);
 163                         (void)fclose(fp);
 164                 }
 165         } else {
 166                 fname = "stdin";
 167
 168                 if (fstat(fileno(stdin), &sb)) {
 169                         ierr();
 170                         exit(1);
 171                 }
 172
 173                 /*
 174                  * Determine if input is a pipe.  4.4BSD will set the SOCKET
 175                  * bit in the st_mode field for pipes.  Fix this then.
 176                  */
 177                 if (lseek(fileno(stdin), (off_t)0, SEEK_CUR) == -1 &&
 178                     errno == ESPIPE) {
 179                         errno = 0;
 180                         fflag = 0;              /* POSIX.2 requires this. */
 181                 }
 182
 183                 if (rflag)
 184                         reverse(stdin, style, off, &sb);
 185                 else
 186                         forward(stdin, style, off, &sb);
 187         }
 188         exit(rval);
 189 }
 190
 191 /*
 192  * Tail's options are weird.  First, -n10 is the same as -n-10, not
 193  * -n+10.  Second, the number options are 1 based and not offsets,
 194  * so -n+1 is the first line, and -c-1 is the last byte.  Third, the
 195  * number options for the -r option specify the number of things that
 196  * get displayed, not the starting point in the file.  The one major
 197  * incompatibility in this version as compared to historical versions
 198  * is that the 'r' option couldn't be modified by the -lbc options,
 199  * i.e. it was always done in lines.  This version treats -rc as a
 200  * number of characters in reverse order.  Finally, the default for
 201  * -r is the entire file, not 10 lines.
 202  */
 203 static void
 204 getarg(int units, enum STYLE forward_style, enum STYLE backward_style,
 205        enum STYLE *style, int *style_set, off_t *off)
 206 {
 207         char *p;
 208
 209         if (*style_set)
 210                 usage();
 211
 212         *off = strtoll(optarg, &p, 10) * units;
 213         if (*p != '\0')
 214                 errx(1, "illegal offset -- %s", optarg);
 215         switch (optarg[0]) {
 216         case '+':
 217                 if (*off != 0)
 218                         *off -= (units);
 219                 *style = forward_style;
 220                 break;
 221         case '-':
 222                 *off = -*off;
 223                 /* FALLTHROUGH */
 224         default:
 225                 *style = backward_style;
 226                 break;
 227         }
 228
 229         *style_set = 1;
 230 }
 231
 232 /*
 233  * Convert the obsolete argument form into something that getopt can handle.
 234  * This means that anything of the form [+-][0-9][0-9]*[lbc][Ffr] that isn't
 235  * the option argument for a -b, -c or -n option gets converted.
 236  */
 237 static void
 238 obsolete(char **argv)
 239 {
 240         char *ap, *p, *t;
 241         size_t len;
 242         char *start;
 243
 244         while ((ap = *++argv) != NULL) {
 245                 /* Return if "--" or not an option of any form. */
 246                 if (ap[0] != '-') {
 247                         if (ap[0] != '+')
 248                                 return;
 249                 } else if (ap[1] == '-')
 250                         return;
 251
 252                 switch(*++ap) {
 253                 /* Old-style option. */
 254                 case '0': case '1': case '2': case '3': case '4':
 255                 case '5': case '6': case '7': case '8': case '9':
 256
 257                         /* Malloc space for dash, new option and argument. */
 258                         len = strlen(*argv);
 259                         if ((start = p = malloc(len + 3)) == NULL)
 260                                 err(1, "malloc");
 261                         *p++ = '-';
 262
 263                         /*
 264                          * Go to the end of the option argument.  Save off any
 265                          * trailing options (-3lf) and translate any trailing
 266                          * output style characters.
 267                          */
 268                         t = *argv + len - 1;
 269                         if (*t == 'F' || *t == 'f' || *t == 'r') {
 270                                 *p++ = *t;
 271                                 *t-- = '\0';
 272                         }
 273                         switch(*t) {
 274                         case 'b':
 275                                 *p++ = 'b';
 276                                 *t = '\0';
 277                                 break;
 278                         case 'c':
 279                                 *p++ = 'c';
 280                                 *t = '\0';
 281                                 break;
 282                         case 'l':
 283                                 *t = '\0';
 284                                 /* FALLTHROUGH */
 285                         case '0': case '1': case '2': case '3': case '4':
 286                         case '5': case '6': case '7': case '8': case '9':
 287                                 *p++ = 'n';
 288                                 break;
 289                         default:
 290                                 errx(1, "illegal option -- %s", *argv);
 291                         }
 292                         *p++ = *argv[0];
 293                         (void)strcpy(p, ap);
 294                         *argv = start;
 295                         continue;
 296
 297                 /*
 298                  * Options w/ arguments, skip the argument and continue
 299                  * with the next option.
 300                  */
 301                 case 'b':
 302                 case 'c':
 303                 case 'n':
 304                         if (!ap[1])
 305                                 ++argv;
 306                         /* FALLTHROUGH */
 307                 /* Options w/o arguments, continue with the next option. */
 308                 case 'F':
 309                 case 'f':
 310                 case 'r':
 311                         continue;
 312
 313                 /* Illegal option, return and let getopt handle it. */
 314                 default:
 315                         return;
 316                 }
 317         }
 318 }
 319
 320 static void
 321 usage(void)
 322 {
 323         (void)fprintf(stderr,
 324             "usage: tail [-F | -f | -r] [-b # | -c # | -n #] [file ...]\n");
 325         exit(1);
 326 }