text_cmds/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
  37 #include <sys/cdefs.h>
  38
  39 __FBSDID("$FreeBSD$");
  40
  41 #ifndef lint
  42 static const char copyright[] =
  43 "@(#) Copyright (c) 1991, 1993\n\
  44         The Regents of the University of California.  All rights reserved.\n";
  45 #endif
  46
  47 #ifndef lint
  48 static const char sccsid[] = "@(#)tail.c        8.1 (Berkeley) 6/6/93";
  49 #endif
  50
  51 #include <sys/types.h>
  52 #include <sys/stat.h>
  53
  54 #include <err.h>
  55 #include <errno.h>
  56 #include <stdio.h>
  57 #include <stdlib.h>
  58 #include <string.h>
  59 #include <unistd.h>
  60
  61 #include "extern.h"
  62
  63 int Fflag, fflag, qflag, rflag, rval, no_files;
  64 const char *fname;
  65
  66 file_info_t *files;
  67
  68 static void obsolete(char **);
  69 static void usage(void);
  70
  71 int
  72 main(int argc, char *argv[])
  73 {
  74         struct stat sb;
  75         FILE *fp;
  76         off_t off;
  77         enum STYLE style;
  78         int i, ch, first;
  79         file_info_t *file;
  80         char *p;
  81
  82         /*
  83          * Tail's options are weird.  First, -n10 is the same as -n-10, not
  84          * -n+10.  Second, the number options are 1 based and not offsets,
  85          * so -n+1 is the first line, and -c-1 is the last byte.  Third, the
  86          * number options for the -r option specify the number of things that
  87          * get displayed, not the starting point in the file.  The one major
  88          * incompatibility in this version as compared to historical versions
  89          * is that the 'r' option couldn't be modified by the -lbc options,
  90          * i.e. it was always done in lines.  This version treats -rc as a
  91          * number of characters in reverse order.  Finally, the default for
  92          * -r is the entire file, not 10 lines.
  93          */
  94 #define ARG(units, forward, backward) {                                 \
  95         if (style)                                                      \
  96                 usage();                                                \
  97         off = strtoll(optarg, &p, 10) * (units);                        \
  98         if (*p)                                                         \
  99                 errx(1, "illegal offset -- %s", optarg);                \
 100         switch(optarg[0]) {                                             \
 101         case '+':                                                       \
 102                 if (off)                                                \
 103                         off -= (units);                                 \
 104                         style = (forward);                              \
 105                 break;                                                  \
 106         case '-':                                                       \
 107                 off = -off;                                             \
 108                 /* FALLTHROUGH */                                       \
 109         default:                                                        \
 110                 style = (backward);                                     \
 111                 break;                                                  \
 112         }                                                               \
 113 }
 114
 115         obsolete(argv);
 116         style = NOTSET;
 117         while ((ch = getopt(argc, argv, "Fb:c:fn:qr")) != -1)
 118                 switch(ch) {
 119                 case 'F':       /* -F is superset of (and implies) -f */
 120                         Fflag = fflag = 1;
 121                         break;
 122                 case 'b':
 123                         ARG(512, FBYTES, RBYTES);
 124                         break;
 125                 case 'c':
 126                         ARG(1, FBYTES, RBYTES);
 127                         break;
 128                 case 'f':
 129                         fflag = 1;
 130                         break;
 131                 case 'n':
 132                         ARG(1, FLINES, RLINES);
 133                         break;
 134                 case 'q':
 135                         qflag = 1;
 136                         break;
 137                 case 'r':
 138                         rflag = 1;
 139                         break;
 140                 case '?':
 141                 default:
 142                         usage();
 143                 }
 144         argc -= optind;
 145         argv += optind;
 146
 147         no_files = argc ? argc : 1;
 148
 149         /*
 150          * If displaying in reverse, don't permit follow option, and convert
 151          * style values.
 152          */
 153         if (rflag) {
 154                 if (fflag)
 155                         usage();
 156                 if (style == FBYTES)
 157                         style = RBYTES;
 158                 else if (style == FLINES)
 159                         style = RLINES;
 160         }
 161
 162         /*
 163          * If style not specified, the default is the whole file for -r, and
 164          * the last 10 lines if not -r.
 165          */
 166         if (style == NOTSET) {
 167                 if (rflag) {
 168                         off = 0;
 169                         style = REVERSE;
 170                 } else {
 171                         off = 10;
 172                         style = RLINES;
 173                 }
 174         }
 175
 176         if (fflag && !argc) {
 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
 188         if (fflag) {
 189                 files = (struct file_info *) malloc(no_files * sizeof(struct file_info));
 190                 if (! files)
 191                         err(1, "Couldn't malloc space for file descriptors.");
 192
 193                 for (file = files; (fname = argc ? *argv++ : "stdin"); file++) {
 194                         file->file_name = malloc(strlen(fname)+1);
 195                         if (! file->file_name)
 196                                 errx(1, "Couldn't malloc space for file name.");
 197                         strncpy(file->file_name, fname, strlen(fname)+1);
 198                         file->fp = argc ? fopen(file->file_name, "r") : stdin;
 199                         if (file->fp == NULL ||
 200                             fstat(fileno(file->fp), &file->st)) {
 201                                 file->fp = NULL;
 202                                 ierr();
 203                                 continue;
 204                         }
 205                         if (!argc)
 206                                 break;
 207                 }
 208                 follow(files, style, off);
 209                 for (i = 0, file = files; i < no_files; i++, file++) {
 210                     free(file->file_name);
 211                 }
 212                 free(files);
 213         } else if (*argv) {
 214                 for (first = 1; (fname = *argv++);) {
 215                         if ((fp = fopen(fname, "r")) == NULL ||
 216                             fstat(fileno(fp), &sb)) {
 217                                 ierr();
 218                                 continue;
 219                         }
 220                         if (argc > 1 && !qflag) {
 221                                 (void)printf("%s==> %s <==\n",
 222                                     first ? "" : "\n", fname);
 223                                 first = 0;
 224                                 (void)fflush(stdout);
 225                         }
 226
 227 #ifdef __APPLE__
 228                         /* 3849683: don't read a directory */
 229                         if (S_IFDIR == (sb.st_mode & S_IFMT))
 230                                 continue;
 231 #endif
 232
 233                         if (rflag)
 234                                 reverse(fp, style, off, &sb);
 235                         else
 236                                 forward(fp, style, off, &sb);
 237                 }
 238         } else {
 239                 fname = "stdin";
 240
 241                 if (fstat(fileno(stdin), &sb)) {
 242                         ierr();
 243                         exit(1);
 244                 }
 245
 246                 if (rflag)
 247                         reverse(stdin, style, off, &sb);
 248                 else
 249                         forward(stdin, style, off, &sb);
 250         }
 251         exit(rval);
 252 }
 253
 254 /*
 255  * Convert the obsolete argument form into something that getopt can handle.
 256  * This means that anything of the form [+-][0-9][0-9]*[lbc][Ffr] that isn't
 257  * the option argument for a -b, -c or -n option gets converted.
 258  */
 259 static void
 260 obsolete(char *argv[])
 261 {
 262         char *ap, *p, *t;
 263         size_t len;
 264         char *start;
 265
 266         while ((ap = *++argv)) {
 267                 /* Return if "--" or not an option of any form. */
 268                 if (ap[0] != '-') {
 269                         if (ap[0] != '+')
 270                                 return;
 271                 } else if (ap[1] == '-')
 272                         return;
 273
 274                 switch(*++ap) {
 275                 /* Old-style option. */
 276                 case '0': case '1': case '2': case '3': case '4':
 277                 case '5': case '6': case '7': case '8': case '9':
 278
 279                         /* Malloc space for dash, new option and argument. */
 280                         len = strlen(*argv);
 281                         if ((start = p = malloc(len + 3)) == NULL)
 282                                 err(1, "malloc");
 283                         *p++ = '-';
 284
 285                         /*
 286                          * Go to the end of the option argument.  Save off any
 287                          * trailing options (-3lf) and translate any trailing
 288                          * output style characters.
 289                          */
 290                         t = *argv + len - 1;
 291                         if (*t == 'F' || *t == 'f' || *t == 'r') {
 292                                 *p++ = *t;
 293                                 *t-- = '\0';
 294                         }
 295                         switch(*t) {
 296                         case 'b':
 297                                 *p++ = 'b';
 298                                 *t = '\0';
 299                                 break;
 300                         case 'c':
 301                                 *p++ = 'c';
 302                                 *t = '\0';
 303                                 break;
 304                         case 'l':
 305                                 *t = '\0';
 306                                 /* FALLTHROUGH */
 307                         case '0': case '1': case '2': case '3': case '4':
 308                         case '5': case '6': case '7': case '8': case '9':
 309                                 *p++ = 'n';
 310                                 break;
 311                         default:
 312                                 errx(1, "illegal option -- %s", *argv);
 313                         }
 314                         *p++ = *argv[0];
 315                         (void)strcpy(p, ap);
 316                         *argv = start;
 317                         continue;
 318
 319                 /*
 320                  * Options w/ arguments, skip the argument and continue
 321                  * with the next option.
 322                  */
 323                 case 'b':
 324                 case 'c':
 325                 case 'n':
 326                         if (!ap[1])
 327                                 ++argv;
 328                         /* FALLTHROUGH */
 329                 /* Options w/o arguments, continue with the next option. */
 330                 case 'F':
 331                 case 'f':
 332                 case 'r':
 333                         continue;
 334
 335                 /* Illegal option, return and let getopt handle it. */
 336                 default:
 337                         return;
 338                 }
 339         }
 340 }
 341
 342 static void
 343 usage(void)
 344 {
 345         (void)fprintf(stderr,
 346             "usage: tail [-F | -f | -r] [-q] [-b # | -c # | -n #]"
 347             " [file ...]\n");
 348         exit(1);
 349 }