src/realpath.c

   1 /* realpath - print the resolved path
   2    Copyright (C) 2011-2012 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 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 "error.h"
  27 #include "quote.h"
  28
  29 /* The official name of this program (e.g., no 'g' prefix).  */
  30 #define PROGRAM_NAME "realpath"
  31
  32 #define AUTHORS proper_name_utf8 ("Padraig Brady", "P\303\241draig Brady")
  33
  34 enum
  35 {
  36   RELATIVE_TO_OPTION = CHAR_MAX + 1,
  37   RELATIVE_BASE_OPTION
  38 };
  39
  40 static bool verbose = true;
  41 static bool logical;
  42 static bool use_nuls;
  43 static const char *can_relative_to;
  44 static const char *can_relative_base;
  45
  46 static struct option const longopts[] =
  47 {
  48   {"canonicalize-existing", no_argument, NULL, 'e'},
  49   {"canonicalize-missing", no_argument, NULL, 'm'},
  50   {"relative-to", required_argument, NULL, RELATIVE_TO_OPTION},
  51   {"relative-base", required_argument, NULL, RELATIVE_BASE_OPTION},
  52   {"quiet", no_argument, NULL, 'q'},
  53   {"strip", no_argument, NULL, 's' /* FIXME: deprecate in 2013 or so */},
  54   {"no-symlinks", no_argument, NULL, 's'},
  55   {"zero", no_argument, NULL, 'z'},
  56   {"logical", no_argument, NULL, 'L'},
  57   {"physical", no_argument, NULL, 'P'},
  58   {GETOPT_HELP_OPTION_DECL},
  59   {GETOPT_VERSION_OPTION_DECL},
  60   {NULL, 0, NULL, 0}
  61 };
  62
  63 void
  64 usage (int status)
  65 {
  66   if (status != EXIT_SUCCESS)
  67     emit_try_help ();
  68   else
  69     {
  70       printf (_("Usage: %s [OPTION]... FILE...\n"), program_name);
  71       fputs (_("\
  72 Print the resolved absolute file name;\n\
  73 all but the last component must exist\n\
  74 \n\
  75 "), stdout);
  76       fputs (_("\
  77   -e, --canonicalize-existing  all components of the path must exist\n\
  78   -m, --canonicalize-missing   no components of the path need exist\n\
  79   -L, --logical                resolve '..' components before symlinks\n\
  80   -P, --physical               resolve symlinks as encountered (default)\n\
  81   -q, --quiet                  suppress most error messages\n\
  82       --relative-to=FILE       print the resolved path relative to FILE\n\
  83       --relative-base=FILE     print absolute paths unless paths below FILE\n\
  84   -s, --strip, --no-symlinks   don't expand symlinks\n\
  85   -z, --zero                   separate output with NUL rather than newline\n\
  86 \n\
  87 "), stdout);
  88       fputs (HELP_OPTION_DESCRIPTION, stdout);
  89       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  90       emit_ancillary_info ();
  91     }
  92   exit (status);
  93 }
  94
  95 /* A wrapper around canonicalize_filename_mode(),
  96    to call it twice when in LOGICAL mode.  */
  97 static char *
  98 realpath_canon (const char *fname, int can_mode)
  99 {
 100   char *can_fname = canonicalize_filename_mode (fname, can_mode);
 101   if (logical && can_fname)  /* canonicalize again to resolve symlinks.  */
 102     {
 103       can_mode &= ~CAN_NOLINKS;
 104       char *can_fname2 = canonicalize_filename_mode (can_fname, can_mode);
 105       free (can_fname);
 106       return can_fname2;
 107     }
 108   return can_fname;
 109 }
 110
 111 /* Test whether prefix is parent or match of path.  */
 112 static bool _GL_ATTRIBUTE_PURE
 113 path_prefix (const char *prefix, const char *path)
 114 {
 115   while (*prefix && *path)
 116     {
 117       if (*prefix != *path)
 118         break;
 119       prefix++;
 120       path++;
 121     }
 122   return (!*prefix && (*path == '/' || !*path));
 123 }
 124
 125 /* Return the length of the longest common prefix
 126    of PATH1 and PATH2, ensuring only full path components
 127    are matched.  Return 0 on no match.  */
 128 static int _GL_ATTRIBUTE_PURE
 129 path_common_prefix (const char *path1, const char *path2)
 130 {
 131   int i = 0;
 132   int ret = 0;
 133
 134   while (*path1 && *path2)
 135     {
 136       if (*path1 != *path2)
 137         break;
 138       if (*path1 == '/')
 139         ret = i;
 140       path1++;
 141       path2++;
 142       i++;
 143     }
 144
 145   if (!*path1 && !*path2)
 146     ret = i;
 147   if (!*path1 && *path2 == '/')
 148     ret = i;
 149   if (!*path2 && *path1 == '/')
 150     ret = i;
 151
 152   return ret;
 153 }
 154
 155 /* Output the relative representation if requested.  */
 156 static bool
 157 relpath (const char *can_fname)
 158 {
 159   if (can_relative_to)
 160     {
 161       /* Enforce --relative-base.  */
 162       if (can_relative_base)
 163         {
 164           if (!path_prefix (can_relative_base, can_fname)
 165               || !path_prefix (can_relative_base, can_relative_to))
 166             return false;
 167         }
 168
 169       /* Skip the prefix common to --relative-to and path.  */
 170       int common_index = path_common_prefix (can_relative_to, can_fname);
 171       const char *relto_suffix = can_relative_to + common_index;
 172       const char *fname_suffix = can_fname + common_index;
 173
 174       /* Replace remaining components of --relative-to with '..', to get
 175          to a common directory.  Then output the remainder of fname.  */
 176       if (*relto_suffix)
 177         {
 178           ++relto_suffix;
 179           printf ("%s", "..");
 180           for (; *relto_suffix; ++relto_suffix)
 181             {
 182               if (*relto_suffix == '/')
 183                 printf ("%s", "/..");
 184             }
 185
 186           printf ("%s", fname_suffix);
 187         }
 188       else
 189         {
 190           if (*fname_suffix)
 191             printf ("%s", ++fname_suffix);
 192           else
 193             printf ("%c", '.');
 194         }
 195
 196       putchar (use_nuls ? '\0' : '\n');
 197
 198       return true;
 199     }
 200
 201   return false;
 202 }
 203
 204 static bool
 205 isdir (const char *path)
 206 {
 207   struct stat sb;
 208   if (stat (path, &sb) != 0)
 209     error (EXIT_FAILURE, errno, _("cannot stat %s"), quote (path));
 210   return S_ISDIR (sb.st_mode);
 211 }
 212
 213 static bool
 214 process_path (const char *fname, int can_mode)
 215 {
 216   char *can_fname = realpath_canon (fname, can_mode);
 217   if (!can_fname)
 218     {
 219       if (verbose)
 220         error (0, errno, "%s", quote (fname));
 221       return false;
 222     }
 223
 224   if (!relpath (can_fname))
 225     printf ("%s%c", can_fname, (use_nuls ? '\0' : '\n'));
 226
 227   free (can_fname);
 228
 229   return true;
 230 }
 231
 232 int
 233 main (int argc, char **argv)
 234 {
 235   bool ok = true;
 236   int can_mode = CAN_ALL_BUT_LAST;
 237   const char *relative_to = NULL;
 238   const char *relative_base = NULL;
 239
 240   initialize_main (&argc, &argv);
 241   set_program_name (argv[0]);
 242   setlocale (LC_ALL, "");
 243   bindtextdomain (PACKAGE, LOCALEDIR);
 244   textdomain (PACKAGE);
 245
 246   atexit (close_stdout);
 247
 248   while (1)
 249     {
 250       int c = getopt_long (argc, argv, "eLmPqsz", longopts, NULL);
 251       if (c == -1)
 252         break;
 253       switch (c)
 254         {
 255         case 'e':
 256           can_mode &= ~CAN_MODE_MASK;
 257           can_mode |= CAN_EXISTING;
 258           break;
 259         case 'm':
 260           can_mode &= ~CAN_MODE_MASK;
 261           can_mode |= CAN_MISSING;
 262           break;
 263         case 'L':
 264           can_mode |= CAN_NOLINKS;
 265           logical = true;
 266           break;
 267         case 's':
 268           can_mode |= CAN_NOLINKS;
 269           logical = false;
 270           break;
 271         case 'P':
 272           can_mode &= ~CAN_NOLINKS;
 273           logical = false;
 274           break;
 275         case 'q':
 276           verbose = false;
 277           break;
 278         case 'z':
 279           use_nuls = true;
 280           break;
 281         case RELATIVE_TO_OPTION:
 282           relative_to = optarg;
 283           break;
 284         case RELATIVE_BASE_OPTION:
 285           relative_base = optarg;
 286           break;
 287         case_GETOPT_HELP_CHAR;
 288         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 289         default:
 290           usage (EXIT_FAILURE);
 291         }
 292     }
 293
 294   if (optind >= argc)
 295     {
 296       error (0, 0, _("missing operand"));
 297       usage (EXIT_FAILURE);
 298     }
 299
 300   if (relative_base && !relative_to)
 301     {
 302       error (0, 0, _("--relative-base requires --relative-to"));
 303       usage (EXIT_FAILURE);
 304     }
 305
 306   bool need_dir = (can_mode & CAN_MODE_MASK) == CAN_EXISTING;
 307   if (relative_to)
 308     {
 309       can_relative_to = realpath_canon (relative_to, can_mode);
 310       if (!can_relative_to)
 311         error (EXIT_FAILURE, errno, "%s", quote (relative_to));
 312       if (need_dir && !isdir (can_relative_to))
 313         error (EXIT_FAILURE, ENOTDIR, "%s", quote (relative_to));
 314     }
 315   if (relative_base)
 316     {
 317       can_relative_base = realpath_canon (relative_base, can_mode);
 318       if (!can_relative_base)
 319         error (EXIT_FAILURE, errno, "%s", quote (relative_base));
 320       if (need_dir && !isdir (can_relative_base))
 321         error (EXIT_FAILURE, ENOTDIR, "%s", quote (relative_base));
 322     }
 323
 324   for (; optind < argc; ++optind)
 325     ok &= process_path (argv[optind], can_mode);
 326
 327   exit (ok ? EXIT_SUCCESS : EXIT_FAILURE);
 328 }