src/readlink.c

   1 /* readlink -- display value of a symbolic link.
   2    Copyright (C) 2002-2010 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation, either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  16
  17 /* Written by Dmitry V. Levin */
  18
  19 #include <config.h>
  20 #include <stdio.h>
  21 #include <getopt.h>
  22 #include <sys/types.h>
  23
  24 #include "system.h"
  25 #include "canonicalize.h"
  26 #include "error.h"
  27 #include "areadlink.h"
  28 #include "quote.h"
  29
  30 /* The official name of this program (e.g., no `g' prefix).  */
  31 #define PROGRAM_NAME "readlink"
  32
  33 #define AUTHORS proper_name ("Dmitry V. Levin")
  34
  35 /* If true, do not output the trailing newline.  */
  36 static bool no_newline;
  37
  38 /* If true, report error messages.  */
  39 static bool verbose;
  40
  41 static struct option const longopts[] =
  42 {
  43   {"canonicalize", no_argument, NULL, 'f'},
  44   {"canonicalize-existing", no_argument, NULL, 'e'},
  45   {"canonicalize-missing", no_argument, NULL, 'm'},
  46   {"no-newline", no_argument, NULL, 'n'},
  47   {"quiet", no_argument, NULL, 'q'},
  48   {"silent", no_argument, NULL, 's'},
  49   {"verbose", no_argument, NULL, 'v'},
  50   {GETOPT_HELP_OPTION_DECL},
  51   {GETOPT_VERSION_OPTION_DECL},
  52   {NULL, 0, NULL, 0}
  53 };
  54
  55 void
  56 usage (int status)
  57 {
  58   if (status != EXIT_SUCCESS)
  59     fprintf (stderr, _("Try `%s --help' for more information.\n"),
  60              program_name);
  61   else
  62     {
  63       printf (_("Usage: %s [OPTION]... FILE\n"), program_name);
  64       fputs (_("Print value of a symbolic link or canonical file name\n\n"),
  65              stdout);
  66       fputs (_("\
  67   -f, --canonicalize            canonicalize by following every symlink in\n\
  68                                 every component of the given name recursively;\n\
  69                                 all but the last component must exist\n\
  70   -e, --canonicalize-existing   canonicalize by following every symlink in\n\
  71                                 every component of the given name recursively,\n\
  72                                 all components must exist\n\
  73 "), stdout);
  74       fputs (_("\
  75   -m, --canonicalize-missing    canonicalize by following every symlink in\n\
  76                                 every component of the given name recursively,\n\
  77                                 without requirements on components existence\n\
  78   -n, --no-newline              do not output the trailing newline\n\
  79   -q, --quiet,\n\
  80   -s, --silent                  suppress most error messages\n\
  81   -v, --verbose                 report error messages\n\
  82 "), stdout);
  83       fputs (HELP_OPTION_DESCRIPTION, stdout);
  84       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  85       emit_ancillary_info ();
  86     }
  87   exit (status);
  88 }
  89
  90 int
  91 main (int argc, char **argv)
  92 {
  93   /* If not -1, use this method to canonicalize.  */
  94   int can_mode = -1;
  95
  96   /* File name to canonicalize.  */
  97   const char *fname;
  98
  99   /* Result of canonicalize.  */
 100   char *value;
 101
 102   int optc;
 103
 104   initialize_main (&argc, &argv);
 105   set_program_name (argv[0]);
 106   setlocale (LC_ALL, "");
 107   bindtextdomain (PACKAGE, LOCALEDIR);
 108   textdomain (PACKAGE);
 109
 110   atexit (close_stdout);
 111
 112   while ((optc = getopt_long (argc, argv, "efmnqsv", longopts, NULL)) != -1)
 113     {
 114       switch (optc)
 115         {
 116         case 'e':
 117           can_mode = CAN_EXISTING;
 118           break;
 119         case 'f':
 120           can_mode = CAN_ALL_BUT_LAST;
 121           break;
 122         case 'm':
 123           can_mode = CAN_MISSING;
 124           break;
 125         case 'n':
 126           no_newline = true;
 127           break;
 128         case 'q':
 129         case 's':
 130           verbose = false;
 131           break;
 132         case 'v':
 133           verbose = true;
 134           break;
 135         case_GETOPT_HELP_CHAR;
 136         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 137         default:
 138           usage (EXIT_FAILURE);
 139         }
 140     }
 141
 142   if (optind >= argc)
 143     {
 144       error (0, 0, _("missing operand"));
 145       usage (EXIT_FAILURE);
 146     }
 147
 148   fname = argv[optind++];
 149
 150   if (optind < argc)
 151     {
 152       error (0, 0, _("extra operand %s"), quote (argv[optind]));
 153       usage (EXIT_FAILURE);
 154     }
 155
 156   value = (can_mode != -1
 157            ? canonicalize_filename_mode (fname, can_mode)
 158            : areadlink_with_size (fname, 63));
 159   if (value)
 160     {
 161       printf ("%s%s", value, (no_newline ? "" : "\n"));
 162       free (value);
 163       return EXIT_SUCCESS;
 164     }
 165
 166   if (verbose)
 167     error (EXIT_FAILURE, errno, "%s", fname);
 168
 169   return EXIT_FAILURE;
 170 }