src/ln.c

   1 /* `ln' program to create links between files.
   2    Copyright (C) 86, 89, 90, 91, 1995-2001 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 2, or (at your option)
   7    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, write to the Free Software Foundation,
  16    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  17 \f
  18 /* Written by Mike Parker and David MacKenzie. */
  19
  20 #ifdef _AIX
  21  #pragma alloca
  22 #endif
  23
  24 #include <config.h>
  25 #include <stdio.h>
  26 #include <sys/types.h>
  27 #include <getopt.h>
  28
  29 #include "system.h"
  30 #include "same.h"
  31 #include "backupfile.h"
  32 #include "error.h"
  33 #include "quote.h"
  34
  35 /* The official name of this program (e.g., no `g' prefix).  */
  36 #define PROGRAM_NAME "ln"
  37
  38 #define AUTHORS "Mike Parker and David MacKenzie"
  39
  40 /* For long options that have no equivalent short option, use a
  41    non-character as a pseudo short option, starting with CHAR_MAX + 1.  */
  42 enum
  43 {
  44   TARGET_DIRECTORY_OPTION = CHAR_MAX + 1
  45 };
  46
  47 int link ();                    /* Some systems don't declare this anywhere. */
  48
  49 #ifdef S_ISLNK
  50 int symlink ();
  51 #endif
  52
  53 /* In being careful not even to try to make hard links to directories,
  54    we have to know whether link(2) follows symlinks.  If it does, then
  55    we have to *stat* the `source' to see if the resulting link would be
  56    to a directory.  Otherwise, we have to use *lstat* so that we allow
  57    users to make hard links to symlinks-that-point-to-directories.  */
  58
  59 #if LINK_FOLLOWS_SYMLINKS
  60 # define STAT_LIKE_LINK(File, Stat_buf) \
  61   stat (File, Stat_buf)
  62 #else
  63 # define STAT_LIKE_LINK(File, Stat_buf) \
  64   lstat (File, Stat_buf)
  65 #endif
  66
  67 /* Construct a string NEW_DEST by concatenating DEST, a slash, and
  68    basename(SOURCE) in alloca'd memory.  Don't modify DEST or SOURCE.  */
  69
  70 #define PATH_BASENAME_CONCAT(new_dest, dest, source)                    \
  71     do                                                                  \
  72       {                                                                 \
  73         const char *source_base;                                        \
  74         char *tmp_source;                                               \
  75                                                                         \
  76         tmp_source = (char *) alloca (strlen ((source)) + 1);           \
  77         strcpy (tmp_source, (source));                                  \
  78         strip_trailing_slashes (tmp_source);                            \
  79         source_base = base_name (tmp_source);                           \
  80                                                                         \
  81         (new_dest) = (char *) alloca (strlen ((dest)) + 1               \
  82                                       + strlen (source_base) + 1);      \
  83         stpcpy (stpcpy (stpcpy ((new_dest), (dest)), "/"), source_base);\
  84       }                                                                 \
  85     while (0)
  86
  87 int isdir ();
  88 int yesno ();
  89 void strip_trailing_slashes ();
  90
  91 /* The name by which the program was run, for error messages.  */
  92 char *program_name;
  93
  94 /* FIXME: document */
  95 enum backup_type backup_type;
  96
  97 /* A pointer to the function used to make links.  This will point to either
  98    `link' or `symlink'. */
  99 static int (*linkfunc) ();
 100
 101 /* If nonzero, make symbolic links; otherwise, make hard links.  */
 102 static int symbolic_link;
 103
 104 /* If nonzero, ask the user before removing existing files.  */
 105 static int interactive;
 106
 107 /* If nonzero, remove existing files unconditionally.  */
 108 static int remove_existing_files;
 109
 110 /* If nonzero, list each file as it is moved. */
 111 static int verbose;
 112
 113 /* If nonzero, allow the superuser to make hard links to directories. */
 114 static int hard_dir_link;
 115
 116 /* If nonzero, and the specified destination is a symbolic link to a
 117    directory, treat it just as if it were a directory.  Otherwise, the
 118    command `ln --force --no-dereference file symlink-to-dir' deletes
 119    symlink-to-dir before creating the new link.  */
 120 static int dereference_dest_dir_symlinks = 1;
 121
 122 static struct option const long_options[] =
 123 {
 124   {"backup", optional_argument, NULL, 'b'},
 125   {"directory", no_argument, NULL, 'F'},
 126   {"no-dereference", no_argument, NULL, 'n'},
 127   {"force", no_argument, NULL, 'f'},
 128   {"interactive", no_argument, NULL, 'i'},
 129   {"suffix", required_argument, NULL, 'S'},
 130   {"target-directory", required_argument, NULL, TARGET_DIRECTORY_OPTION},
 131   {"symbolic", no_argument, NULL, 's'},
 132   {"verbose", no_argument, NULL, 'v'},
 133   {"version-control", required_argument, NULL, 'V'}, /* Deprecated. FIXME. */
 134   {GETOPT_HELP_OPTION_DECL},
 135   {GETOPT_VERSION_OPTION_DECL},
 136   {NULL, 0, NULL, 0}
 137 };
 138
 139 /* Make a link DEST to the (usually) existing file SOURCE.
 140    Symbolic links to nonexistent files are allowed.
 141    If DEST is a directory, put the link to SOURCE in that directory.
 142    Return 1 if there is an error, otherwise 0.  */
 143
 144 static int
 145 do_link (const char *source, const char *dest)
 146 {
 147   struct stat source_stats;
 148   struct stat dest_stats;
 149   char *dest_backup = NULL;
 150   int lstat_status;
 151   int backup_succeeded = 0;
 152
 153   /* Use stat here instead of lstat.
 154      On SVR4, link does not follow symlinks, so this check disallows
 155      making hard links to symlinks that point to directories.  Big deal.
 156      On other systems, link follows symlinks, so this check is right.  */
 157   if (!symbolic_link)
 158     {
 159       if (STAT_LIKE_LINK (source, &source_stats) != 0)
 160         {
 161           error (0, errno, _("accessing %s"), quote (source));
 162           return 1;
 163         }
 164
 165       if (S_ISLNK (source_stats.st_mode))
 166         {
 167           error (0, 0, _("%s: warning: making a hard link to a symbolic link\
 168  is not portable"),
 169                  quote (source));
 170         }
 171
 172       if (!hard_dir_link && S_ISDIR (source_stats.st_mode))
 173         {
 174           error (0, 0, _("%s: hard link not allowed for directory"),
 175                  quote (source));
 176           return 1;
 177         }
 178     }
 179
 180   lstat_status = lstat (dest, &dest_stats);
 181   if (lstat_status != 0 && errno != ENOENT)
 182     {
 183       error (0, errno, _("accessing %s"), quote (dest));
 184       return 1;
 185     }
 186
 187   /* If the destination is a directory or (it is a symlink to a directory
 188      and the user has not specified --no-dereference), then form the
 189      actual destination name by appending base_name (source) to the
 190      specified destination directory.  */
 191   if ((lstat_status == 0
 192        && S_ISDIR (dest_stats.st_mode))
 193 #ifdef S_ISLNK
 194       || (dereference_dest_dir_symlinks
 195           && (lstat_status == 0
 196               && S_ISLNK (dest_stats.st_mode)
 197               && isdir (dest)))
 198 #endif
 199      )
 200     {
 201       /* Target is a directory; build the full filename. */
 202       char *new_dest;
 203       PATH_BASENAME_CONCAT (new_dest, dest, source);
 204       dest = new_dest;
 205
 206       /* Get stats for new DEST.  */
 207       lstat_status = lstat (dest, &dest_stats);
 208       if (lstat_status != 0 && errno != ENOENT)
 209         {
 210           error (0, errno, _("accessing %s"), quote (dest));
 211           return 1;
 212         }
 213     }
 214
 215   /* If --force (-f) has been specified without --backup, then before
 216      making a link ln must remove the destination file if it exists.
 217      (with --backup, it just renames any existing destination file)
 218      But if the source and destination are the same, don't remove
 219      anything and fail right here.  */
 220   if (remove_existing_files
 221       && lstat_status == 0
 222       /* Allow `ln -sf --backup k k' to succeed in creating the
 223          self-referential symlink, but don't allow the hard-linking
 224          equivalent: `ln -f k k' (with or without --backup) to get
 225          beyond this point, because the error message you'd get is
 226          misleading.  */
 227       && (backup_type == none || !symlink)
 228       && (!symbolic_link || stat (source, &source_stats) == 0)
 229       && source_stats.st_dev == dest_stats.st_dev
 230       && source_stats.st_ino == dest_stats.st_ino
 231       /* The following detects whether removing DEST will also remove
 232          SOURCE.  If the file has only one link then both are surely
 233          the same link.  Otherwise check whether they point to the same
 234          name in the same directory.  */
 235       && (source_stats.st_nlink == 1 || same_name (source, dest)))
 236     {
 237       error (0, 0, _("%s and %s are the same file"),
 238              quote_n (0, source), quote_n (1, dest));
 239       return 1;
 240     }
 241
 242   if (lstat_status == 0 || lstat (dest, &dest_stats) == 0)
 243     {
 244       if (S_ISDIR (dest_stats.st_mode))
 245         {
 246           error (0, 0, _("%s: cannot overwrite directory"), quote (dest));
 247           return 1;
 248         }
 249       if (interactive)
 250         {
 251           fprintf (stderr, _("%s: replace %s? "), program_name, quote (dest));
 252           if (!yesno ())
 253             return 0;
 254         }
 255       else if (!remove_existing_files && backup_type == none)
 256         {
 257           error (0, 0, _("%s: File exists"), quote (dest));
 258           return 1;
 259         }
 260
 261       if (backup_type != none)
 262         {
 263           char *tmp_backup = find_backup_file_name (dest, backup_type);
 264           if (tmp_backup == NULL)
 265             xalloc_die ();
 266           dest_backup = (char *) alloca (strlen (tmp_backup) + 1);
 267           strcpy (dest_backup, tmp_backup);
 268           free (tmp_backup);
 269           if (rename (dest, dest_backup))
 270             {
 271               if (errno != ENOENT)
 272                 {
 273                   error (0, errno, _("cannot backup %s"), quote (dest));
 274                   return 1;
 275                 }
 276               else
 277                 dest_backup = NULL;
 278             }
 279           else
 280             {
 281               backup_succeeded = 1;
 282             }
 283         }
 284
 285       /* Try to unlink DEST even if we may have renamed it.  In some unusual
 286          cases (when DEST and DEST_BACKUP are hard-links that refer to the
 287          same file), rename succeeds and DEST remains.  If we didn't remove
 288          DEST in that case, the subsequent LINKFUNC call would fail.  */
 289       if (unlink (dest) && errno != ENOENT)
 290         {
 291           error (0, errno, _("cannot remove %s"), quote (dest));
 292           return 1;
 293         }
 294     }
 295   else if (errno != ENOENT)
 296     {
 297       error (0, errno, _("accessing %s"), quote (dest));
 298       return 1;
 299     }
 300
 301   if (verbose)
 302     {
 303       printf ((symbolic_link
 304                ? _("create symbolic link %s to %s")
 305                : _("create hard link %s to %s")),
 306               quote_n (0, dest), quote_n (1, source));
 307       if (backup_succeeded)
 308         printf (_(" (backup: %s)"), quote (dest_backup));
 309       putchar ('\n');
 310     }
 311
 312   if ((*linkfunc) (source, dest) == 0)
 313     {
 314       return 0;
 315     }
 316
 317   error (0, errno,
 318          (symbolic_link
 319           ? _("creating symbolic link %s to %s")
 320           : _("creating hard link %s to %s")),
 321          quote_n (0, dest), quote_n (1, source));
 322
 323   if (dest_backup)
 324     {
 325       if (rename (dest_backup, dest))
 326         error (0, errno, _("cannot un-backup %s"), quote (dest));
 327     }
 328   return 1;
 329 }
 330
 331 void
 332 usage (int status)
 333 {
 334   if (status != 0)
 335     fprintf (stderr, _("Try `%s --help' for more information.\n"),
 336              program_name);
 337   else
 338     {
 339       printf (_("\
 340 Usage: %s [OPTION]... TARGET [LINK_NAME]\n\
 341   or:  %s [OPTION]... TARGET... DIRECTORY\n\
 342   or:  %s [OPTION]... --target-directory=DIRECTORY TARGET...\n\
 343 "),
 344               program_name, program_name, program_name);
 345       printf (_("\
 346 Create a link to the specified TARGET with optional LINK_NAME.\n\
 347 If LINK_NAME is omitted, a link with the same basename as the TARGET is\n\
 348 created in the current directory.  When using the second form with more\n\
 349 than one TARGET, the last argument must be a directory;  create links\n\
 350 in DIRECTORY to each TARGET.  Create hard links by default, symbolic\n\
 351 links with --symbolic.  When creating hard links, each TARGET must exist.\n\
 352 \n\
 353       --backup[=CONTROL]      make a backup of each existing destination file\n\
 354   -b                          like --backup but does not accept an argument\n\
 355   -d, -F, --directory         hard link directories (super-user only)\n\
 356   -f, --force                 remove existing destination files\n\
 357   -n, --no-dereference        treat destination that is a symlink to a\n\
 358                                 directory as if it were a normal file\n\
 359   -i, --interactive           prompt whether to remove destinations\n\
 360   -s, --symbolic              make symbolic links instead of hard links\n\
 361   -S, --suffix=SUFFIX         override the usual backup suffix\n\
 362       --target-directory=DIRECTORY  specify the DIRECTORY in which to create\n\
 363                                 the links\n\
 364   -v, --verbose               print name of each file before linking\n\
 365       --help                  display this help and exit\n\
 366       --version               output version information and exit\n\
 367 \n\
 368 "));
 369       printf (_("\
 370 The backup suffix is `~', unless set with --suffix or SIMPLE_BACKUP_SUFFIX.\n\
 371 The version control method may be selected via the --backup option or through\n\
 372 the VERSION_CONTROL environment variable.  Here are the values:\n\
 373 \n\
 374   none, off       never make backups (even if --backup is given)\n\
 375   numbered, t     make numbered backups\n\
 376   existing, nil   numbered if numbered backups exist, simple otherwise\n\
 377   simple, never   always make simple backups\n\
 378 "));
 379       puts (_("\nReport bugs to <bug-fileutils@gnu.org>."));
 380     }
 381   exit (status);
 382 }
 383
 384 int
 385 main (int argc, char **argv)
 386 {
 387   int c;
 388   int errors;
 389   int make_backups = 0;
 390   char *backup_suffix_string;
 391   char *version_control_string = NULL;
 392   char *target_directory = NULL;
 393   int target_directory_specified;
 394   unsigned int n_files;
 395   char **file;
 396   int dest_is_dir;
 397
 398   program_name = argv[0];
 399   setlocale (LC_ALL, "");
 400   bindtextdomain (PACKAGE, LOCALEDIR);
 401   textdomain (PACKAGE);
 402
 403   atexit (close_stdout);
 404
 405   /* FIXME: consider not calling getenv for SIMPLE_BACKUP_SUFFIX unless
 406      we'll actually use backup_suffix_string.  */
 407   backup_suffix_string = getenv ("SIMPLE_BACKUP_SUFFIX");
 408
 409   symbolic_link = remove_existing_files = interactive = verbose
 410     = hard_dir_link = 0;
 411   errors = 0;
 412
 413   while ((c = getopt_long (argc, argv, "bdfinsvFS:V:", long_options, NULL))
 414          != -1)
 415     {
 416       switch (c)
 417         {
 418         case 0:                 /* Long-named option. */
 419           break;
 420
 421         case 'V':  /* FIXME: this is deprecated.  Remove it in 2001.  */
 422           error (0, 0,
 423                  _("warning: --version-control (-V) is obsolete;  support for\
 424  it\nwill be removed in some future release.  Use --backup=%s instead."
 425                    ), optarg);
 426           /* Fall through.  */
 427
 428         case 'b':
 429           make_backups = 1;
 430           if (optarg)
 431             version_control_string = optarg;
 432           break;
 433         case 'd':
 434         case 'F':
 435           hard_dir_link = 1;
 436           break;
 437         case 'f':
 438           remove_existing_files = 1;
 439           interactive = 0;
 440           break;
 441         case 'i':
 442           remove_existing_files = 0;
 443           interactive = 1;
 444           break;
 445         case 'n':
 446           dereference_dest_dir_symlinks = 0;
 447           break;
 448         case 's':
 449 #ifdef S_ISLNK
 450           symbolic_link = 1;
 451 #else
 452           error (1, 0, _("symbolic links are not supported on this system"));
 453 #endif
 454           break;
 455         case TARGET_DIRECTORY_OPTION:
 456           target_directory = optarg;
 457           break;
 458         case 'v':
 459           verbose = 1;
 460           break;
 461         case 'S':
 462           make_backups = 1;
 463           backup_suffix_string = optarg;
 464           break;
 465         case_GETOPT_HELP_CHAR;
 466         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 467         default:
 468           usage (1);
 469           break;
 470         }
 471     }
 472
 473   n_files = argc - optind;
 474   file = argv + optind;
 475
 476   if (n_files == 0)
 477     {
 478       error (0, 0, _("missing file argument"));
 479       usage (1);
 480     }
 481
 482   target_directory_specified = (target_directory != NULL);
 483   if (!target_directory)
 484     target_directory = file[n_files - 1];
 485
 486   /* If there's only one file argument, then pretend `.' was given
 487      as the second argument.  */
 488   if (n_files == 1)
 489     {
 490       static char *dummy[2];
 491       dummy[0] = file[0];
 492       dummy[1] = ".";
 493       file = dummy;
 494       n_files = 2;
 495       dest_is_dir = 1;
 496     }
 497   else
 498     {
 499       dest_is_dir = isdir (target_directory);
 500     }
 501
 502   if (symbolic_link)
 503     linkfunc = symlink;
 504   else
 505     linkfunc = link;
 506
 507   if (target_directory_specified && !dest_is_dir)
 508     {
 509       error (0, 0, _("specified target directory, %s is not a directory"),
 510              quote (target_directory));
 511       usage (1);
 512     }
 513
 514   if (backup_suffix_string)
 515     simple_backup_suffix = xstrdup (backup_suffix_string);
 516
 517   backup_type = (make_backups
 518                  ? xget_version (_("backup type"), version_control_string)
 519                  : none);
 520
 521   if (target_directory_specified || n_files > 2)
 522     {
 523       unsigned int i;
 524       unsigned int last_file_idx = (target_directory_specified
 525                                     ? n_files - 1
 526                                     : n_files - 2);
 527
 528       if (!target_directory_specified && !dest_is_dir)
 529         error (1, 0,
 530            _("when making multiple links, last argument must be a directory"));
 531       for (i = 0; i <= last_file_idx; ++i)
 532         errors += do_link (file[i], target_directory);
 533     }
 534   else
 535     {
 536       struct stat source_stats;
 537       const char *source;
 538       char *dest;
 539       char *new_dest;
 540
 541       source = file[0];
 542       dest = file[1];
 543
 544       /* When the destination is specified with a trailing slash and the
 545          source exists but is not a directory, convert the user's command
 546          `ln source dest/' to `ln source dest/basename(source)'.  */
 547
 548       if (dest[strlen (dest) - 1] == '/'
 549           && lstat (source, &source_stats) == 0
 550           && !S_ISDIR (source_stats.st_mode))
 551         {
 552           PATH_BASENAME_CONCAT (new_dest, dest, source);
 553         }
 554       else
 555         {
 556           new_dest = dest;
 557         }
 558
 559       errors = do_link (source, new_dest);
 560     }
 561
 562   exit (errors != 0);
 563 }