src/readlink.c

   1 /* readlink -- display value of a symbolic link.
   2    Copyright (C) 2002-2015 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   {"zero", no_argument, NULL, 'z'},
  51   {GETOPT_HELP_OPTION_DECL},
  52   {GETOPT_VERSION_OPTION_DECL},
  53   {NULL, 0, NULL, 0}
  54 };
  55
  56 void
  57 usage (int status)
  58 {
  59   if (status != EXIT_SUCCESS)
  60     emit_try_help ();
  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;\
  69 \n\
  70                                 all but the last component must exist\n\
  71   -e, --canonicalize-existing   canonicalize by following every symlink in\n\
  72                                 every component of the given name recursively,\
  73 \n\
  74                                 all components must exist\n\
  75 "), stdout);
  76       fputs (_("\
  77   -m, --canonicalize-missing    canonicalize by following every symlink in\n\
  78                                 every component of the given name recursively,\
  79 \n\
  80                                 without requirements on components existence\n\
  81   -n, --no-newline              do not output the trailing delimiter\n\
  82   -q, --quiet,\n\
  83   -s, --silent                  suppress most error messages\n\
  84   -v, --verbose                 report error messages\n\
  85   -z, --zero                    end each output line with NUL, not newline\n\
  86 "), stdout);
  87       fputs (HELP_OPTION_DESCRIPTION, stdout);
  88       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  89       emit_ancillary_info (PROGRAM_NAME);
  90     }
  91   exit (status);
  92 }
  93
  94 int
  95 main (int argc, char **argv)
  96 {
  97   /* If not -1, use this method to canonicalize.  */
  98   int can_mode = -1;
  99   int status = EXIT_SUCCESS;
 100   int optc;
 101   bool use_nuls = false;
 102
 103   initialize_main (&argc, &argv);
 104   set_program_name (argv[0]);
 105   setlocale (LC_ALL, "");
 106   bindtextdomain (PACKAGE, LOCALEDIR);
 107   textdomain (PACKAGE);
 108
 109   atexit (close_stdout);
 110
 111   while ((optc = getopt_long (argc, argv, "efmnqsvz", longopts, NULL)) != -1)
 112     {
 113       switch (optc)
 114         {
 115         case 'e':
 116           can_mode = CAN_EXISTING;
 117           break;
 118         case 'f':
 119           can_mode = CAN_ALL_BUT_LAST;
 120           break;
 121         case 'm':
 122           can_mode = CAN_MISSING;
 123           break;
 124         case 'n':
 125           no_newline = true;
 126           break;
 127         case 'q':
 128         case 's':
 129           verbose = false;
 130           break;
 131         case 'v':
 132           verbose = true;
 133           break;
 134         case 'z':
 135           use_nuls = true;
 136           break;
 137         case_GETOPT_HELP_CHAR;
 138         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 139         default:
 140           usage (EXIT_FAILURE);
 141         }
 142     }
 143
 144   if (optind >= argc)
 145     {
 146       error (0, 0, _("missing operand"));
 147       usage (EXIT_FAILURE);
 148     }
 149
 150   if (argc - optind > 1)
 151     {
 152       if (no_newline)
 153         error (0, 0, _("ignoring --no-newline with multiple arguments"));
 154       no_newline = false;
 155     }
 156
 157   for (; optind < argc; ++optind)
 158     {
 159       const char *fname = argv[optind];
 160       char *value = (can_mode != -1
 161                      ? canonicalize_filename_mode (fname, can_mode)
 162                      : areadlink_with_size (fname, 63));
 163       if (value)
 164         {
 165           fputs (value, stdout);
 166           if (! no_newline)
 167             putchar (use_nuls ? '\0' : '\n');
 168           free (value);
 169         }
 170       else
 171         {
 172           status = EXIT_FAILURE;
 173           if (verbose)
 174             error (0, errno, "%s", quote (fname));
 175         }
 176     }
 177
 178   return status;
 179 }