src/realpath.c

   1 /* realpath - print the resolved path
   2    Copyright (C) 2011-2024 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 "relpath.h"
  27
  28 /* The official name of this program (e.g., no 'g' prefix).  */
  29 #define PROGRAM_NAME "realpath"
  30
  31 #define AUTHORS proper_name_lite ("Padraig Brady", "P\303\241draig Brady")
  32
  33 enum
  34 {
  35   RELATIVE_TO_OPTION = CHAR_MAX + 1,
  36   RELATIVE_BASE_OPTION
  37 };
  38
  39 static bool verbose = true;
  40 static bool logical;
  41 static bool use_nuls;
  42 static char const *can_relative_to;
  43 static char const *can_relative_base;
  44
  45 static struct option const longopts[] =
  46 {
  47   {"canonicalize-existing", no_argument, nullptr, 'e'},
  48   {"canonicalize-missing", no_argument, nullptr, 'm'},
  49   {"relative-to", required_argument, nullptr, RELATIVE_TO_OPTION},
  50   {"relative-base", required_argument, nullptr, RELATIVE_BASE_OPTION},
  51   {"quiet", no_argument, nullptr, 'q'},
  52   {"strip", no_argument, nullptr, 's'},
  53   {"no-symlinks", no_argument, nullptr, 's'},
  54   {"zero", no_argument, nullptr, 'z'},
  55   {"logical", no_argument, nullptr, 'L'},
  56   {"physical", no_argument, nullptr, 'P'},
  57   {GETOPT_HELP_OPTION_DECL},
  58   {GETOPT_VERSION_OPTION_DECL},
  59   {nullptr, 0, nullptr, 0}
  60 };
  61
  62 void
  63 usage (int status)
  64 {
  65   if (status != EXIT_SUCCESS)
  66     emit_try_help ();
  67   else
  68     {
  69       printf (_("Usage: %s [OPTION]... FILE...\n"), program_name);
  70       fputs (_("\
  71 Print the resolved absolute file name;\n\
  72 all but the last component must exist\n\
  73 \n\
  74 "), stdout);
  75       fputs (_("\
  76   -e, --canonicalize-existing  all components of the path must exist\n\
  77   -m, --canonicalize-missing   no path components need exist or be a directory\
  78 \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=DIR        print the resolved path relative to DIR\n\
  83       --relative-base=DIR      print absolute paths unless paths below DIR\n\
  84   -s, --strip, --no-symlinks   don't expand symlinks\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 /* A wrapper around canonicalize_filename_mode(),
  95    to call it twice when in LOGICAL mode.  */
  96 static char *
  97 realpath_canon (char const *fname, int can_mode)
  98 {
  99   char *can_fname = canonicalize_filename_mode (fname, can_mode);
 100   if (logical && can_fname)  /* canonicalize again to resolve symlinks.  */
 101     {
 102       can_mode &= ~CAN_NOLINKS;
 103       char *can_fname2 = canonicalize_filename_mode (can_fname, can_mode);
 104       free (can_fname);
 105       return can_fname2;
 106     }
 107   return can_fname;
 108 }
 109
 110 /* Test whether canonical prefix is parent or match of path.  */
 111 ATTRIBUTE_PURE
 112 static bool
 113 path_prefix (char const *prefix, char const *path)
 114 {
 115   /* We already know prefix[0] and path[0] are '/'.  */
 116   prefix++;
 117   path++;
 118
 119   /* '/' is the prefix of everything except '//' (since we know '//'
 120      is only present after canonicalization if it is distinct).  */
 121   if (!*prefix)
 122     return *path != '/';
 123
 124   /* Likewise, '//' is a prefix of any double-slash path.  */
 125   if (*prefix == '/' && !prefix[1])
 126     return *path == '/';
 127
 128   /* Any other prefix has a non-slash portion.  */
 129   while (*prefix && *path)
 130     {
 131       if (*prefix != *path)
 132         break;
 133       prefix++;
 134       path++;
 135     }
 136   return (!*prefix && (*path == '/' || !*path));
 137 }
 138
 139 static bool
 140 isdir (char const *path)
 141 {
 142   struct stat sb;
 143   if (stat (path, &sb) != 0)
 144     error (EXIT_FAILURE, errno, _("cannot stat %s"), quoteaf (path));
 145   return S_ISDIR (sb.st_mode);
 146 }
 147
 148 static bool
 149 process_path (char const *fname, int can_mode)
 150 {
 151   char *can_fname = realpath_canon (fname, can_mode);
 152   if (!can_fname)
 153     {
 154       if (verbose)
 155         error (0, errno, "%s", quotef (fname));
 156       return false;
 157     }
 158
 159   if (!can_relative_to
 160       || (can_relative_base && !path_prefix (can_relative_base, can_fname))
 161       || (can_relative_to && !relpath (can_fname, can_relative_to, nullptr, 0)))
 162     fputs (can_fname, stdout);
 163
 164   putchar (use_nuls ? '\0' : '\n');
 165
 166   free (can_fname);
 167
 168   return true;
 169 }
 170
 171 int
 172 main (int argc, char **argv)
 173 {
 174   bool ok = true;
 175   int can_mode = CAN_ALL_BUT_LAST;
 176   char const *relative_to = nullptr;
 177   char const *relative_base = nullptr;
 178
 179   initialize_main (&argc, &argv);
 180   set_program_name (argv[0]);
 181   setlocale (LC_ALL, "");
 182   bindtextdomain (PACKAGE, LOCALEDIR);
 183   textdomain (PACKAGE);
 184
 185   atexit (close_stdout);
 186
 187   while (true)
 188     {
 189       int c = getopt_long (argc, argv, "eLmPqsz", longopts, nullptr);
 190       if (c == -1)
 191         break;
 192       switch (c)
 193         {
 194         case 'e':
 195           can_mode &= ~CAN_MODE_MASK;
 196           can_mode |= CAN_EXISTING;
 197           break;
 198         case 'm':
 199           can_mode &= ~CAN_MODE_MASK;
 200           can_mode |= CAN_MISSING;
 201           break;
 202         case 'L':
 203           can_mode |= CAN_NOLINKS;
 204           logical = true;
 205           break;
 206         case 's':
 207           can_mode |= CAN_NOLINKS;
 208           logical = false;
 209           break;
 210         case 'P':
 211           can_mode &= ~CAN_NOLINKS;
 212           logical = false;
 213           break;
 214         case 'q':
 215           verbose = false;
 216           break;
 217         case 'z':
 218           use_nuls = true;
 219           break;
 220         case RELATIVE_TO_OPTION:
 221           relative_to = optarg;
 222           break;
 223         case RELATIVE_BASE_OPTION:
 224           relative_base = optarg;
 225           break;
 226         case_GETOPT_HELP_CHAR;
 227         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 228         default:
 229           usage (EXIT_FAILURE);
 230         }
 231     }
 232
 233   if (optind >= argc)
 234     {
 235       error (0, 0, _("missing operand"));
 236       usage (EXIT_FAILURE);
 237     }
 238
 239   if (relative_base && !relative_to)
 240     relative_to = relative_base;
 241
 242   bool need_dir = (can_mode & CAN_MODE_MASK) == CAN_EXISTING;
 243   if (relative_to)
 244     {
 245       can_relative_to = realpath_canon (relative_to, can_mode);
 246       if (!can_relative_to)
 247         error (EXIT_FAILURE, errno, "%s", quotef (relative_to));
 248       if (need_dir && !isdir (can_relative_to))
 249         error (EXIT_FAILURE, ENOTDIR, "%s", quotef (relative_to));
 250     }
 251   if (relative_base == relative_to)
 252     can_relative_base = can_relative_to;
 253   else if (relative_base)
 254     {
 255       char *base = realpath_canon (relative_base, can_mode);
 256       if (!base)
 257         error (EXIT_FAILURE, errno, "%s", quotef (relative_base));
 258       if (need_dir && !isdir (base))
 259         error (EXIT_FAILURE, ENOTDIR, "%s", quotef (relative_base));
 260       /* --relative-to is a no-op if it does not have --relative-base
 261            as a prefix */
 262       if (path_prefix (base, can_relative_to))
 263         can_relative_base = base;
 264       else
 265         {
 266           free (base);
 267           can_relative_base = can_relative_to;
 268           can_relative_to = nullptr;
 269         }
 270     }
 271
 272   for (; optind < argc; ++optind)
 273     ok &= process_path (argv[optind], can_mode);
 274
 275   return ok ? EXIT_SUCCESS : EXIT_FAILURE;
 276 }