src/realpath.c

   1 /* realpath - print the resolved path
   2    Copyright (C) 2011-2019 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 Pádraig Brady.  */
  18
  19 #include <config.h>
  20 #include <getopt.h>
  21 #include <stdio.h>
  22 #include <sys/types.h>
  23
  24 #include "system.h"
  25 #include "canonicalize.h"
  26 #include "die.h"
  27 #include "error.h"
  28 #include "relpath.h"
  29
  30 /* The official name of this program (e.g., no 'g' prefix).  */
  31 #define PROGRAM_NAME "realpath"
  32
  33 #define AUTHORS proper_name ("Padraig Brady")
  34
  35 enum
  36 {
  37   RELATIVE_TO_OPTION = CHAR_MAX + 1,
  38   RELATIVE_BASE_OPTION
  39 };
  40
  41 static bool verbose = true;
  42 static bool logical;
  43 static bool use_nuls;
  44 static const char *can_relative_to;
  45 static const char *can_relative_base;
  46
  47 static struct option const longopts[] =
  48 {
  49   {"canonicalize-existing", no_argument, NULL, 'e'},
  50   {"canonicalize-missing", no_argument, NULL, 'm'},
  51   {"relative-to", required_argument, NULL, RELATIVE_TO_OPTION},
  52   {"relative-base", required_argument, NULL, RELATIVE_BASE_OPTION},
  53   {"quiet", no_argument, NULL, 'q'},
  54   {"strip", no_argument, NULL, 's'},
  55   {"no-symlinks", no_argument, NULL, 's'},
  56   {"zero", no_argument, NULL, 'z'},
  57   {"logical", no_argument, NULL, 'L'},
  58   {"physical", no_argument, NULL, 'P'},
  59   {GETOPT_HELP_OPTION_DECL},
  60   {GETOPT_VERSION_OPTION_DECL},
  61   {NULL, 0, NULL, 0}
  62 };
  63
  64 void
  65 usage (int status)
  66 {
  67   if (status != EXIT_SUCCESS)
  68     emit_try_help ();
  69   else
  70     {
  71       printf (_("Usage: %s [OPTION]... FILE...\n"), program_name);
  72       fputs (_("\
  73 Print the resolved absolute file name;\n\
  74 all but the last component must exist\n\
  75 \n\
  76 "), stdout);
  77       fputs (_("\
  78   -e, --canonicalize-existing  all components of the path must exist\n\
  79   -m, --canonicalize-missing   no path components need exist or be a directory\
  80 \n\
  81   -L, --logical                resolve '..' components before symlinks\n\
  82   -P, --physical               resolve symlinks as encountered (default)\n\
  83   -q, --quiet                  suppress most error messages\n\
  84       --relative-to=DIR        print the resolved path relative to DIR\n\
  85       --relative-base=DIR      print absolute paths unless paths below DIR\n\
  86   -s, --strip, --no-symlinks   don't expand symlinks\n\
  87   -z, --zero                   end each output line with NUL, not newline\n\
  88 \n\
  89 "), stdout);
  90       fputs (HELP_OPTION_DESCRIPTION, stdout);
  91       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  92       emit_ancillary_info (PROGRAM_NAME);
  93     }
  94   exit (status);
  95 }
  96
  97 /* A wrapper around canonicalize_filename_mode(),
  98    to call it twice when in LOGICAL mode.  */
  99 static char *
 100 realpath_canon (const char *fname, int can_mode)
 101 {
 102   char *can_fname = canonicalize_filename_mode (fname, can_mode);
 103   if (logical && can_fname)  /* canonicalize again to resolve symlinks.  */
 104     {
 105       can_mode &= ~CAN_NOLINKS;
 106       char *can_fname2 = canonicalize_filename_mode (can_fname, can_mode);
 107       free (can_fname);
 108       return can_fname2;
 109     }
 110   return can_fname;
 111 }
 112
 113 /* Test whether canonical prefix is parent or match of path.  */
 114 static bool _GL_ATTRIBUTE_PURE
 115 path_prefix (const char *prefix, const char *path)
 116 {
 117   /* We already know prefix[0] and path[0] are '/'.  */
 118   prefix++;
 119   path++;
 120
 121   /* '/' is the prefix of everything except '//' (since we know '//'
 122      is only present after canonicalization if it is distinct).  */
 123   if (!*prefix)
 124     return *path != '/';
 125
 126   /* Likewise, '//' is a prefix of any double-slash path.  */
 127   if (*prefix == '/' && !prefix[1])
 128     return *path == '/';
 129
 130   /* Any other prefix has a non-slash portion.  */
 131   while (*prefix && *path)
 132     {
 133       if (*prefix != *path)
 134         break;
 135       prefix++;
 136       path++;
 137     }
 138   return (!*prefix && (*path == '/' || !*path));
 139 }
 140
 141 static bool
 142 isdir (const char *path)
 143 {
 144   struct stat sb;
 145   if (stat (path, &sb) != 0)
 146     die (EXIT_FAILURE, errno, _("cannot stat %s"), quoteaf (path));
 147   return S_ISDIR (sb.st_mode);
 148 }
 149
 150 static bool
 151 process_path (const char *fname, int can_mode)
 152 {
 153   char *can_fname = realpath_canon (fname, can_mode);
 154   if (!can_fname)
 155     {
 156       if (verbose)
 157         error (0, errno, "%s", quotef (fname));
 158       return false;
 159     }
 160
 161   if (!can_relative_to
 162       || (can_relative_base && !path_prefix (can_relative_base, can_fname))
 163       || (can_relative_to && !relpath (can_fname, can_relative_to, NULL, 0)))
 164     fputs (can_fname, stdout);
 165
 166   putchar (use_nuls ? '\0' : '\n');
 167
 168   free (can_fname);
 169
 170   return true;
 171 }
 172
 173 int
 174 main (int argc, char **argv)
 175 {
 176   bool ok = true;
 177   int can_mode = CAN_ALL_BUT_LAST;
 178   const char *relative_to = NULL;
 179   const char *relative_base = NULL;
 180
 181   initialize_main (&argc, &argv);
 182   set_program_name (argv[0]);
 183   setlocale (LC_ALL, "");
 184   bindtextdomain (PACKAGE, LOCALEDIR);
 185   textdomain (PACKAGE);
 186
 187   atexit (close_stdout);
 188
 189   while (1)
 190     {
 191       int c = getopt_long (argc, argv, "eLmPqsz", longopts, NULL);
 192       if (c == -1)
 193         break;
 194       switch (c)
 195         {
 196         case 'e':
 197           can_mode &= ~CAN_MODE_MASK;
 198           can_mode |= CAN_EXISTING;
 199           break;
 200         case 'm':
 201           can_mode &= ~CAN_MODE_MASK;
 202           can_mode |= CAN_MISSING;
 203           break;
 204         case 'L':
 205           can_mode |= CAN_NOLINKS;
 206           logical = true;
 207           break;
 208         case 's':
 209           can_mode |= CAN_NOLINKS;
 210           logical = false;
 211           break;
 212         case 'P':
 213           can_mode &= ~CAN_NOLINKS;
 214           logical = false;
 215           break;
 216         case 'q':
 217           verbose = false;
 218           break;
 219         case 'z':
 220           use_nuls = true;
 221           break;
 222         case RELATIVE_TO_OPTION:
 223           relative_to = optarg;
 224           break;
 225         case RELATIVE_BASE_OPTION:
 226           relative_base = optarg;
 227           break;
 228         case_GETOPT_HELP_CHAR;
 229         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 230         default:
 231           usage (EXIT_FAILURE);
 232         }
 233     }
 234
 235   if (optind >= argc)
 236     {
 237       error (0, 0, _("missing operand"));
 238       usage (EXIT_FAILURE);
 239     }
 240
 241   if (relative_base && !relative_to)
 242     relative_to = relative_base;
 243
 244   bool need_dir = (can_mode & CAN_MODE_MASK) == CAN_EXISTING;
 245   if (relative_to)
 246     {
 247       can_relative_to = realpath_canon (relative_to, can_mode);
 248       if (!can_relative_to)
 249         die (EXIT_FAILURE, errno, "%s", quotef (relative_to));
 250       if (need_dir && !isdir (can_relative_to))
 251         die (EXIT_FAILURE, ENOTDIR, "%s", quotef (relative_to));
 252     }
 253   if (relative_base == relative_to)
 254     can_relative_base = can_relative_to;
 255   else if (relative_base)
 256     {
 257       char *base = realpath_canon (relative_base, can_mode);
 258       if (!base)
 259         die (EXIT_FAILURE, errno, "%s", quotef (relative_base));
 260       if (need_dir && !isdir (base))
 261         die (EXIT_FAILURE, ENOTDIR, "%s", quotef (relative_base));
 262       /* --relative-to is a no-op if it does not have --relative-base
 263            as a prefix */
 264       if (path_prefix (base, can_relative_to))
 265         can_relative_base = base;
 266       else
 267         {
 268           free (base);
 269           can_relative_base = can_relative_to;
 270           can_relative_to = NULL;
 271         }
 272     }
 273
 274   for (; optind < argc; ++optind)
 275     ok &= process_path (argv[optind], can_mode);
 276
 277   return ok ? EXIT_SUCCESS : EXIT_FAILURE;
 278 }