src/readlink.c

   1 /* readlink -- display value of a symbolic link.
   2    Copyright (C) 2002-2022 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 <https://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
  29 /* The official name of this program (e.g., no 'g' prefix).  */
  30 #define PROGRAM_NAME "readlink"
  31
  32 #define AUTHORS proper_name ("Dmitry V. Levin")
  33
  34 /* If true, do not output the trailing newline.  */
  35 static bool no_newline;
  36
  37 /* If true, report error messages.  */
  38 static bool verbose;
  39
  40 static struct option const longopts[] =
  41 {
  42   {"canonicalize", no_argument, NULL, 'f'},
  43   {"canonicalize-existing", no_argument, NULL, 'e'},
  44   {"canonicalize-missing", no_argument, NULL, 'm'},
  45   {"no-newline", no_argument, NULL, 'n'},
  46   {"quiet", no_argument, NULL, 'q'},
  47   {"silent", no_argument, NULL, 's'},
  48   {"verbose", no_argument, NULL, 'v'},
  49   {"zero", no_argument, NULL, 'z'},
  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     emit_try_help ();
  60   else
  61     {
  62       printf (_("Usage: %s [OPTION]... FILE...\n"), program_name);
  63       fputs (_("Print value of a symbolic link or canonical file name\n\n"),
  64              stdout);
  65       fputs (_("\
  66   -f, --canonicalize            canonicalize by following every symlink in\n\
  67                                 every component of the given name recursively;\
  68 \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,\
  72 \n\
  73                                 all components must exist\n\
  74 "), stdout);
  75       fputs (_("\
  76   -m, --canonicalize-missing    canonicalize by following every symlink in\n\
  77                                 every component of the given name recursively,\
  78 \n\
  79                                 without requirements on components existence\n\
  80   -n, --no-newline              do not output the trailing delimiter\n\
  81   -q, --quiet\n\
  82   -s, --silent                  suppress most error messages (on by default)\n\
  83   -v, --verbose                 report error messages\n\
  84   -z, --zero                    end each output line with NUL, not newline\n\
  85 "), stdout);
  86       fputs (HELP_OPTION_DESCRIPTION, stdout);
  87       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  88       emit_ancillary_info (PROGRAM_NAME);
  89     }
  90   exit (status);
  91 }
  92
  93 int
  94 main (int argc, char **argv)
  95 {
  96   /* If not -1, use this method to canonicalize.  */
  97   int can_mode = -1;
  98   int status = EXIT_SUCCESS;
  99   int optc;
 100   bool use_nuls = false;
 101
 102   initialize_main (&argc, &argv);
 103   set_program_name (argv[0]);
 104   setlocale (LC_ALL, "");
 105   bindtextdomain (PACKAGE, LOCALEDIR);
 106   textdomain (PACKAGE);
 107
 108   atexit (close_stdout);
 109
 110   while ((optc = getopt_long (argc, argv, "efmnqsvz", longopts, NULL)) != -1)
 111     {
 112       switch (optc)
 113         {
 114         case 'e':
 115           can_mode = CAN_EXISTING;
 116           break;
 117         case 'f':
 118           can_mode = CAN_ALL_BUT_LAST;
 119           break;
 120         case 'm':
 121           can_mode = CAN_MISSING;
 122           break;
 123         case 'n':
 124           no_newline = true;
 125           break;
 126         case 'q':
 127         case 's':
 128           verbose = false;
 129           break;
 130         case 'v':
 131           verbose = true;
 132           break;
 133         case 'z':
 134           use_nuls = true;
 135           break;
 136         case_GETOPT_HELP_CHAR;
 137         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 138         default:
 139           usage (EXIT_FAILURE);
 140         }
 141     }
 142
 143   if (optind >= argc)
 144     {
 145       error (0, 0, _("missing operand"));
 146       usage (EXIT_FAILURE);
 147     }
 148
 149   if (argc - optind > 1)
 150     {
 151       if (no_newline)
 152         error (0, 0, _("ignoring --no-newline with multiple arguments"));
 153       no_newline = false;
 154     }
 155
 156   for (; optind < argc; ++optind)
 157     {
 158       char const *fname = argv[optind];
 159       char *value = (can_mode != -1
 160                      ? canonicalize_filename_mode (fname, can_mode)
 161                      : areadlink_with_size (fname, 63));
 162       if (value)
 163         {
 164           fputs (value, stdout);
 165           if (! no_newline)
 166             putchar (use_nuls ? '\0' : '\n');
 167           free (value);
 168         }
 169       else
 170         {
 171           status = EXIT_FAILURE;
 172           if (verbose)
 173             error (0, errno, "%s", quotef (fname));
 174         }
 175     }
 176
 177   return status;
 178 }