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. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  * @(#) Copyright (c) 1991, 1993 The Regents of the University of California.  All rights reserved.
  37  * @(#)tail.c   8.1 (Berkeley) 6/6/93
  38  * $FreeBSD: src/usr.bin/tail/tail.c,v 1.6.2.2 2001/12/19 20:29:31 iedowse Exp $
  39  * $DragonFly: src/usr.bin/tail/tail.c,v 1.6 2005/03/01 22:37:33 cpressey Exp $
  40  */
  41
  42 #include <sys/types.h>
  43 #include <sys/stat.h>
  44 #include <errno.h>
  45 #include <unistd.h>
  46 #include <stdio.h>
  47 #include <stdlib.h>
  48 #include <string.h>
  49 #include <err.h>
  50 #include "extern.h"
  51
  52 int Fflag, fflag, rflag, rval, no_files;
  53 const char *fname;
  54
  55 file_info_t *files;
  56
  57 static void obsolete(char **);
  58 static void usage(void);
  59 static void getarg(int, enum STYLE, enum STYLE, enum STYLE *, int *, off_t *);
  60
  61 int
  62 main(int argc, char **argv)
  63 {
  64         struct stat sb;
  65         FILE *fp;
  66         off_t off = 0;
  67         enum STYLE style;
  68         int style_set;
  69         int i, ch;
  70         file_info_t *file;
  71
  72         obsolete(argv);
  73         style_set = 0;
  74         while ((ch = getopt(argc, argv, "Fb:c:fn:r")) != -1)
  75                 switch(ch) {
  76                 case 'F':       /* -F is superset of (and implies) -f */
  77                         Fflag = fflag = 1;
  78                         break;
  79                 case 'b':
  80                         getarg(512, FBYTES, RBYTES, &style, &style_set, &off);
  81                         break;
  82                 case 'c':
  83                         getarg(1, FBYTES, RBYTES, &style, &style_set, &off);
  84                         break;
  85                 case 'f':
  86                         fflag = 1;
  87                         break;
  88                 case 'n':
  89                         getarg(1, FLINES, RLINES, &style, &style_set, &off);
  90                         break;
  91                 case 'r':
  92                         rflag = 1;
  93                         break;
  94                 case '?':
  95                 default:
  96                         usage();
  97                 }
  98         argc -= optind;
  99         argv += optind;
 100
 101         no_files = argc ? argc : 1;
 102
 103         /*
 104          * If displaying in reverse, don't permit follow option, and convert
 105          * style values.
 106          */
 107         if (rflag) {
 108                 if (fflag)
 109                         usage();
 110                 if (style == FBYTES)
 111                         style = RBYTES;
 112                 else if (style == FLINES)
 113                         style = RLINES;
 114         }
 115
 116         /*
 117          * If style not specified, the default is the whole file for -r, and
 118          * the last 10 lines if not -r.
 119          */
 120         if (!style_set) {
 121                 if (rflag) {
 122                         off = 0;
 123                         style = REVERSE;
 124                 } else {
 125                         off = 10;
 126                         style = RLINES;
 127                 }
 128         }
 129
 130         if (*argv && fflag) {
 131                 files = malloc(no_files * sizeof(struct file_info));
 132                 if (files == NULL)
 133                         err(1, "Couldn't malloc space for files descriptors.");
 134
 135                 for (file = files; (fname = *argv++) != NULL; file++) {
 136                         file->file_name = strdup(fname);
 137                         if (! file->file_name)
 138                                 errx(1, "Couldn't alloc space for file name.");
 139                         file->fp = fopen(file->file_name, "r");
 140                         if (file->fp == NULL ||
 141                             fstat(fileno(file->fp), &file->st) == -1) {
 142                                 file->fp = NULL;
 143                                 ierr();
 144                                 continue;
 145                         }
 146                 }
 147                 follow(files, style, off);
 148                 for (i = 0, file = files; i < no_files; i++, file++)
 149                         free(file->file_name);
 150                 free(files);
 151         } else if (*argv) {
 152                 for (i = 0; (fname = *argv++) != NULL; ++i) {
 153                         if ((fp = fopen(fname, "r")) == NULL ||
 154                             fstat(fileno(fp), &sb)) {
 155                                 ierr();
 156                                 continue;
 157                         }
 158                         if (argc > 1) {
 159                                 showfilename(i, fname);
 160                                 (void)fflush(stdout);
 161                         }
 162
 163                         if (rflag)
 164                                 reverse(fp, style, off, &sb);
 165                         else
 166                                 forward(fp, style, off, &sb);
 167                         (void)fclose(fp);
 168                 }
 169         } else {
 170                 fname = "stdin";
 171
 172                 if (fstat(fileno(stdin), &sb)) {
 173                         ierr();
 174                         exit(1);
 175                 }
 176
 177                 /*
 178                  * Determine if input is a pipe.  4.4BSD will set the SOCKET
 179                  * bit in the st_mode field for pipes.  Fix this then.
 180                  */
 181                 if (lseek(fileno(stdin), (off_t)0, SEEK_CUR) == -1 &&
 182                     errno == ESPIPE) {
 183                         errno = 0;
 184                         fflag = 0;              /* POSIX.2 requires this. */
 185                 }
 186
 187                 if (rflag)
 188                         reverse(stdin, style, off, &sb);
 189                 else
 190                         forward(stdin, style, off, &sb);
 191         }
 192         exit(rval);
 193 }
 194
 195 /*
 196  * Tail's options are weird.  First, -n10 is the same as -n-10, not
 197  * -n+10.  Second, the number options are 1 based and not offsets,
 198  * so -n+1 is the first line, and -c-1 is the last byte.  Third, the
 199  * number options for the -r option specify the number of things that
 200  * get displayed, not the starting point in the file.  The one major
 201  * incompatibility in this version as compared to historical versions
 202  * is that the 'r' option couldn't be modified by the -lbc options,
 203  * i.e. it was always done in lines.  This version treats -rc as a
 204  * number of characters in reverse order.  Finally, the default for
 205  * -r is the entire file, not 10 lines.
 206  */
 207 static void
 208 getarg(int units, enum STYLE forward_style, enum STYLE backward_style,
 209        enum STYLE *style, int *style_set, off_t *off)
 210 {
 211         char *p;
 212
 213         if (*style_set)
 214                 usage();
 215
 216         *off = strtoll(optarg, &p, 10) * units;
 217         if (*p != '\0')
 218                 errx(1, "illegal offset -- %s", optarg);
 219         switch (optarg[0]) {
 220         case '+':
 221                 if (*off != 0)
 222                         *off -= (units);
 223                 *style = forward_style;
 224                 break;
 225         case '-':
 226                 *off = -*off;
 227                 /* FALLTHROUGH */
 228         default:
 229                 *style = backward_style;
 230                 break;
 231         }
 232
 233         *style_set = 1;
 234 }
 235
 236 /*
 237  * Convert the obsolete argument form into something that getopt can handle.
 238  * This means that anything of the form [+-][0-9][0-9]*[lbc][Ffr] that isn't
 239  * the option argument for a -b, -c or -n option gets converted.
 240  */
 241 static void
 242 obsolete(char **argv)
 243 {
 244         char *ap, *p, *t;
 245         size_t len;
 246         char *start;
 247
 248         while ((ap = *++argv) != NULL) {
 249                 /* Return if "--" or not an option of any form. */
 250                 if (ap[0] != '-') {
 251                         if (ap[0] != '+')
 252                                 return;
 253                 } else if (ap[1] == '-')
 254                         return;
 255
 256                 switch(*++ap) {
 257                 /* Old-style option. */
 258                 case '0': case '1': case '2': case '3': case '4':
 259                 case '5': case '6': case '7': case '8': case '9':
 260
 261                         /* Malloc space for dash, new option and argument. */
 262                         len = strlen(*argv);
 263                         if ((start = p = malloc(len + 3)) == NULL)
 264                                 err(1, "malloc");
 265                         *p++ = '-';
 266
 267                         /*
 268                          * Go to the end of the option argument.  Save off any
 269                          * trailing options (-3lf) and translate any trailing
 270                          * output style characters.
 271                          */
 272                         t = *argv + len - 1;
 273                         if (*t == 'F' || *t == 'f' || *t == 'r') {
 274                                 *p++ = *t;
 275                                 *t-- = '\0';
 276                         }
 277                         switch(*t) {
 278                         case 'b':
 279                                 *p++ = 'b';
 280                                 *t = '\0';
 281                                 break;
 282                         case 'c':
 283                                 *p++ = 'c';
 284                                 *t = '\0';
 285                                 break;
 286                         case 'l':
 287                                 *t = '\0';
 288                                 /* FALLTHROUGH */
 289                         case '0': case '1': case '2': case '3': case '4':
 290                         case '5': case '6': case '7': case '8': case '9':
 291                                 *p++ = 'n';
 292                                 break;
 293                         default:
 294                                 errx(1, "illegal option -- %s", *argv);
 295                         }
 296                         *p++ = *argv[0];
 297                         (void)strcpy(p, ap);
 298                         *argv = start;
 299                         continue;
 300
 301                 /*
 302                  * Options w/ arguments, skip the argument and continue
 303                  * with the next option.
 304                  */
 305                 case 'b':
 306                 case 'c':
 307                 case 'n':
 308                         if (!ap[1])
 309                                 ++argv;
 310                         /* FALLTHROUGH */
 311                 /* Options w/o arguments, continue with the next option. */
 312                 case 'F':
 313                 case 'f':
 314                 case 'r':
 315                         continue;
 316
 317                 /* Illegal option, return and let getopt handle it. */
 318                 default:
 319                         return;
 320                 }
 321         }
 322 }
 323
 324 static void
 325 usage(void)
 326 {
 327         (void)fprintf(stderr,
 328             "usage: tail [-F | -f | -r] [-b # | -c # | -n #] [file ...]\n");
 329         exit(1);
 330 }