src/ln.c

   1 /* `ln' program to create links between files.
   2    Copyright (C) 86, 89, 90, 91, 1995-2000 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
  34 /* The official name of this program (e.g., no `g' prefix).  */
  35 #define PROGRAM_NAME "ln"
  36
  37 #define AUTHORS "Mike Parker and David MacKenzie"
  38
  39 /* For long options that have no equivalent short option, use a
  40    non-character as a pseudo short option, starting with CHAR_MAX + 1.  */
  41 enum
  42 {
  43   TARGET_DIRECTORY_OPTION = CHAR_MAX + 1
  44 };
  45
  46 int link ();                    /* Some systems don't declare this anywhere. */
  47
  48 #ifdef S_ISLNK
  49 int symlink ();
  50 #endif
  51
  52 /* In being careful not even to try to make hard links to directories,
  53    we have to know whether link(2) follows symlinks.  If it does, then
  54    we have to *stat* the `source' to see if the resulting link would be
  55    to a directory.  Otherwise, we have to use *lstat* so that we allow
  56    users to make hard links to symlinks-that-point-to-directories.  */
  57
  58 #if LINK_FOLLOWS_SYMLINKS
  59 # define STAT_LIKE_LINK(File, Stat_buf) \
  60   stat (File, Stat_buf)
  61 #else
  62 # define STAT_LIKE_LINK(File, Stat_buf) \
  63   lstat (File, Stat_buf)
  64 #endif
  65
  66 /* Construct a string NEW_DEST by concatenating DEST, a slash, and
  67    basename(SOURCE) in alloca'd memory.  Don't modify DEST or SOURCE.  */
  68
  69 #define PATH_BASENAME_CONCAT(new_dest, dest, source)                    \
  70     do                                                                  \
  71       {                                                                 \
  72         const char *source_base;                                        \
  73         char *tmp_source;                                               \
  74                                                                         \
  75         tmp_source = (char *) alloca (strlen ((source)) + 1);           \
  76         strcpy (tmp_source, (source));                                  \
  77         strip_trailing_slashes (tmp_source);                            \
  78         source_base = base_name (tmp_source);                           \
  79                                                                         \
  80         (new_dest) = (char *) alloca (strlen ((dest)) + 1               \
  81                                       + strlen (source_base) + 1);      \
  82         stpcpy (stpcpy (stpcpy ((new_dest), (dest)), "/"), source_base);\
  83       }                                                                 \
  84     while (0)
  85
  86 int isdir ();
  87 int yesno ();
  88 void strip_trailing_slashes ();
  89
  90 /* The name by which the program was run, for error messages.  */
  91 char *program_name;
  92
  93 /* FIXME: document */
  94 enum backup_type backup_type;
  95
  96 /* A pointer to the function used to make links.  This will point to either
  97    `link' or `symlink'. */
  98 static int (*linkfunc) ();
  99
 100 /* If nonzero, make symbolic links; otherwise, make hard links.  */
 101 static int symbolic_link;
 102
 103 /* A string describing type of link to make.  For use in verbose
 104    diagnostics and in error messages.  */
 105 static const char *link_type_string;
 106
 107 /* If nonzero, ask the user before removing existing files.  */
 108 static int interactive;
 109
 110 /* If nonzero, remove existing files unconditionally.  */
 111 static int remove_existing_files;
 112
 113 /* If nonzero, list each file as it is moved. */
 114 static int verbose;
 115
 116 /* If nonzero, allow the superuser to make hard links to directories. */
 117 static int hard_dir_link;
 118
 119 /* If nonzero, and the specified destination is a symbolic link to a
 120    directory, treat it just as if it were a directory.  Otherwise, the
 121    command `ln --force --no-dereference file symlink-to-dir' deletes
 122    symlink-to-dir before creating the new link.  */
 123 static int dereference_dest_dir_symlinks = 1;
 124
 125 static struct option const long_options[] =
 126 {
 127   {"backup", optional_argument, NULL, 'b'},
 128   {"directory", no_argument, NULL, 'F'},
 129   {"no-dereference", no_argument, NULL, 'n'},
 130   {"force", no_argument, NULL, 'f'},
 131   {"interactive", no_argument, NULL, 'i'},
 132   {"suffix", required_argument, NULL, 'S'},
 133   {"target-directory", required_argument, NULL, TARGET_DIRECTORY_OPTION},
 134   {"symbolic", no_argument, NULL, 's'},
 135   {"verbose", no_argument, NULL, 'v'},
 136   {"version-control", required_argument, NULL, 'V'}, /* Deprecated. FIXME. */
 137   {GETOPT_HELP_OPTION_DECL},
 138   {GETOPT_VERSION_OPTION_DECL},
 139   {NULL, 0, NULL, 0}
 140 };
 141
 142 /* Make a link DEST to the (usually) existing file SOURCE.
 143    Symbolic links to nonexistent files are allowed.
 144    If DEST is a directory, put the link to SOURCE in that directory.
 145    Return 1 if there is an error, otherwise 0.  */
 146
 147 static int
 148 do_link (const char *source, const char *dest)
 149 {
 150   struct stat source_stats;
 151   struct stat dest_stats;
 152   char *dest_backup = NULL;
 153   int lstat_status;
 154   int backup_succeeded = 0;
 155
 156   /* Use stat here instead of lstat.
 157      On SVR4, link does not follow symlinks, so this check disallows
 158      making hard links to symlinks that point to directories.  Big deal.
 159      On other systems, link follows symlinks, so this check is right.  */
 160   if (!symbolic_link)
 161     {
 162       if (STAT_LIKE_LINK (source, &source_stats) != 0)
 163         {
 164           error (0, errno, "%s", source);
 165           return 1;
 166         }
 167
 168       if (S_ISLNK (source_stats.st_mode))
 169         {
 170           error (0, 0, _("%s: warning: making a hard link to a symbolic link\
 171  is not portable"),
 172                  source);
 173         }
 174
 175       if (!hard_dir_link && S_ISDIR (source_stats.st_mode))
 176         {
 177           error (0, 0, _("%s: hard link not allowed for directory"), source);
 178           return 1;
 179         }
 180     }
 181
 182   lstat_status = lstat (dest, &dest_stats);
 183   if (lstat_status != 0 && errno != ENOENT)
 184     {
 185       error (0, errno, "%s", dest);
 186       return 1;
 187     }
 188
 189   /* If the destination is a directory or (it is a symlink to a directory
 190      and the user has not specified --no-dereference), then form the
 191      actual destination name by appending base_name (source) to the
 192      specified destination directory.  */
 193   if ((lstat_status == 0
 194        && S_ISDIR (dest_stats.st_mode))
 195 #ifdef S_ISLNK
 196       || (dereference_dest_dir_symlinks
 197           && (lstat_status == 0
 198               && S_ISLNK (dest_stats.st_mode)
 199               && isdir (dest)))
 200 #endif
 201      )
 202     {
 203       /* Target is a directory; build the full filename. */
 204       char *new_dest;
 205       PATH_BASENAME_CONCAT (new_dest, dest, source);
 206       dest = new_dest;
 207
 208       /* Get stats for new DEST.  */
 209       lstat_status = lstat (dest, &dest_stats);
 210       if (lstat_status != 0 && errno != ENOENT)
 211         {
 212           error (0, errno, "%s", dest);
 213           return 1;
 214         }
 215     }
 216
 217   /* If --force (-f) has been specified without --backup, then before
 218      making a link ln must remove the destination file if it exists.
 219      (with --backup, it just renames any existing destination file)
 220      But if the source and destination are the same, don't remove
 221      anything and fail right here.  */
 222   if (remove_existing_files
 223       && lstat_status == 0
 224       /* Allow `ln -sf --backup k k' to succeed in creating the
 225          self-referential symlink, but don't allow the hard-linking
 226          equivalent: `ln -f k k' (with or without --backup) to get
 227          beyond this point, because the error message you'd get is
 228          misleading.  */
 229       && (backup_type == none || !symlink)
 230       && (!symbolic_link || stat (source, &source_stats) == 0)
 231       && source_stats.st_dev == dest_stats.st_dev
 232       && source_stats.st_ino == dest_stats.st_ino
 233       /* The following detects whether removing DEST will also remove
 234          SOURCE.  If the file has only one link then both are surely
 235          the same link.  Otherwise check whether they point to the same
 236          name in the same directory.  */
 237       && (source_stats.st_nlink == 1 || same_name (source, dest)))
 238     {
 239       error (0, 0, _("`%s' and `%s' are the same file"), source, dest);
 240       return 1;
 241     }
 242
 243   if (lstat_status == 0 || lstat (dest, &dest_stats) == 0)
 244     {
 245       if (S_ISDIR (dest_stats.st_mode))
 246         {
 247           error (0, 0, _("%s: cannot overwrite directory"), dest);
 248           return 1;
 249         }
 250       if (interactive)
 251         {
 252           fprintf (stderr, _("%s: replace `%s'? "), program_name, dest);
 253           if (!yesno ())
 254             return 0;
 255         }
 256       else if (!remove_existing_files && backup_type == none)
 257         {
 258           error (0, 0, _("%s: File exists"), dest);
 259           return 1;
 260         }
 261
 262       if (backup_type != none)
 263         {
 264           char *tmp_backup = find_backup_file_name (dest, backup_type);
 265           if (tmp_backup == NULL)
 266             error (1, 0, _("virtual memory exhausted"));
 267           dest_backup = (char *) alloca (strlen (tmp_backup) + 1);
 268           strcpy (dest_backup, tmp_backup);
 269           free (tmp_backup);
 270           if (rename (dest, dest_backup))
 271             {
 272               if (errno != ENOENT)
 273                 {
 274                   error (0, errno, _("cannot backup `%s'"), dest);
 275                   return 1;
 276                 }
 277               else
 278                 dest_backup = NULL;
 279             }
 280           else
 281             {
 282               backup_succeeded = 1;
 283             }
 284         }
 285
 286       /* Try to unlink DEST even if we may have renamed it.  In some unusual
 287          cases (when DEST and DEST_BACKUP are hard-links that refer to the
 288          same file), rename succeeds and DEST remains.  If we didn't remove
 289          DEST in that case, the subsequent LINKFUNC call would fail.  */
 290       if (unlink (dest) && errno != ENOENT)
 291         {
 292           error (0, errno, _("cannot remove `%s'"), dest);
 293           return 1;
 294         }
 295     }
 296   else if (errno != ENOENT)
 297     {
 298       error (0, errno, "%s", dest);
 299       return 1;
 300     }
 301
 302   if (verbose)
 303     {
 304       printf (_("create %s %s to %s"), link_type_string, dest, source);
 305       if (backup_succeeded)
 306         printf (_(" (backup: %s)"), dest_backup);
 307       putchar ('\n');
 308     }
 309
 310   if ((*linkfunc) (source, dest) == 0)
 311     {
 312       return 0;
 313     }
 314
 315   error (0, errno, _("cannot create %s `%s' to `%s'"), link_type_string,
 316          dest, source);
 317
 318   if (dest_backup)
 319     {
 320       if (rename (dest_backup, dest))
 321         error (0, errno, _("cannot un-backup `%s'"), dest);
 322     }
 323   return 1;
 324 }
 325
 326 void
 327 usage (int status)
 328 {
 329   if (status != 0)
 330     fprintf (stderr, _("Try `%s --help' for more information.\n"),
 331              program_name);
 332   else
 333     {
 334       printf (_("\
 335 Usage: %s [OPTION]... TARGET [LINK_NAME]\n\
 336   or:  %s [OPTION]... TARGET... DIRECTORY\n\
 337   or:  %s [OPTION]... --target-directory=DIRECTORY TARGET...\n\
 338 "),
 339               program_name, program_name, program_name);
 340       printf (_("\
 341 Create a link to the specified TARGET with optional LINK_NAME.  If there is\n\
 342 more than one TARGET, the last argument must be a directory;  create links\n\
 343 in DIRECTORY to each TARGET.  Create hard links by default, symbolic links\n\
 344 with --symbolic.  When creating hard links, each TARGET must exist.\n\
 345 \n\
 346   -b, --backup[=CONTROL]      make a backup of each existing destination file\n\
 347   -d, -F, --directory         hard link directories (super-user only)\n\
 348   -f, --force                 remove existing destination files\n\
 349   -n, --no-dereference        treat destination that is a symlink to a\n\
 350                                 directory as if it were a normal file\n\
 351   -i, --interactive           prompt whether to remove destinations\n\
 352   -s, --symbolic              make symbolic links instead of hard links\n\
 353   -S, --suffix=SUFFIX         override the usual backup suffix\n\
 354       --target-directory=DIRECTORY  specify the DIRECTORY in which to create\n\
 355                                 the links\n\
 356   -v, --verbose               print name of each file before linking\n\
 357       --help                  display this help and exit\n\
 358       --version               output version information and exit\n\
 359 \n\
 360 "));
 361       printf (_("\
 362 The backup suffix is `~', unless set with --suffix or SIMPLE_BACKUP_SUFFIX.\n\
 363 The version control method may be selected via the --backup option or through\n\
 364 the VERSION_CONTROL environment variable.  Here are the values:\n\
 365 \n\
 366   none, off       never make backups (even if --backup is given)\n\
 367   numbered, t     make numbered backups\n\
 368   existing, nil   numbered if numbered backups exist, simple otherwise\n\
 369   simple, never   always make simple backups\n\
 370 "));
 371       puts (_("\nReport bugs to <bug-fileutils@gnu.org>."));
 372       close_stdout ();
 373     }
 374   exit (status);
 375 }
 376
 377 int
 378 main (int argc, char **argv)
 379 {
 380   int c;
 381   int errors;
 382   int make_backups = 0;
 383   char *backup_suffix_string;
 384   char *version_control_string = NULL;
 385   char *target_directory = NULL;
 386   int target_directory_specified;
 387   unsigned int n_files;
 388   char **file;
 389   int dest_is_dir;
 390
 391   program_name = argv[0];
 392   setlocale (LC_ALL, "");
 393   bindtextdomain (PACKAGE, LOCALEDIR);
 394   textdomain (PACKAGE);
 395
 396   /* FIXME: consider not calling getenv for SIMPLE_BACKUP_SUFFIX unless
 397      we'll actually use backup_suffix_string.  */
 398   backup_suffix_string = getenv ("SIMPLE_BACKUP_SUFFIX");
 399
 400   symbolic_link = remove_existing_files = interactive = verbose
 401     = hard_dir_link = 0;
 402   errors = 0;
 403
 404   while ((c = getopt_long (argc, argv, "bdfinsvFS:V:", long_options, NULL))
 405          != -1)
 406     {
 407       switch (c)
 408         {
 409         case 0:                 /* Long-named option. */
 410           break;
 411
 412         case 'V':  /* FIXME: this is deprecated.  Remove it in 2001.  */
 413           error (0, 0,
 414                  _("warning: --version-control (-V) is obsolete;  support for\
 415  it\nwill be removed in some future release.  Use --backup=%s instead."
 416                    ), optarg);
 417           /* Fall through.  */
 418
 419         case 'b':
 420           make_backups = 1;
 421           if (optarg)
 422             version_control_string = optarg;
 423           break;
 424         case 'd':
 425         case 'F':
 426           hard_dir_link = 1;
 427           break;
 428         case 'f':
 429           remove_existing_files = 1;
 430           interactive = 0;
 431           break;
 432         case 'i':
 433           remove_existing_files = 0;
 434           interactive = 1;
 435           break;
 436         case 'n':
 437           dereference_dest_dir_symlinks = 0;
 438           break;
 439         case 's':
 440 #ifdef S_ISLNK
 441           symbolic_link = 1;
 442 #else
 443           error (1, 0, _("symbolic links are not supported on this system"));
 444 #endif
 445           break;
 446         case TARGET_DIRECTORY_OPTION:
 447           target_directory = optarg;
 448           break;
 449         case 'v':
 450           verbose = 1;
 451           break;
 452         case 'S':
 453           make_backups = 1;
 454           backup_suffix_string = optarg;
 455           break;
 456         case_GETOPT_HELP_CHAR;
 457         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 458         default:
 459           usage (1);
 460           break;
 461         }
 462     }
 463
 464   n_files = argc - optind;
 465   file = argv + optind;
 466
 467   if (n_files == 0)
 468     {
 469       error (0, 0, _("missing file argument"));
 470       usage (1);
 471     }
 472
 473   target_directory_specified = (target_directory != NULL);
 474   if (!target_directory)
 475     target_directory = file[n_files - 1];
 476
 477   /* If there's only one file argument, then pretend `.' was given
 478      as the second argument.  */
 479   if (n_files == 1)
 480     {
 481       static char *dummy[2];
 482       dummy[0] = file[0];
 483       dummy[1] = ".";
 484       file = dummy;
 485       n_files = 2;
 486       dest_is_dir = 1;
 487     }
 488   else
 489     {
 490       dest_is_dir = isdir (target_directory);
 491     }
 492
 493 #ifdef S_ISLNK
 494   if (symbolic_link)
 495     {
 496       linkfunc = symlink;
 497       link_type_string = _("symbolic link");
 498     }
 499   else
 500     {
 501       linkfunc = link;
 502       link_type_string = _("hard link");
 503     }
 504 #else
 505   link_type_string = _("link");
 506 #endif
 507
 508   if (target_directory_specified && !dest_is_dir)
 509     {
 510       error (0, 0, _("specified target directory, `%s' is not a directory"),
 511              target_directory);
 512       usage (1);
 513     }
 514
 515   backup_type = (make_backups
 516                  ? xget_version (_("--version-control"), version_control_string)
 517                  : none);
 518
 519   if (target_directory_specified || n_files > 2)
 520     {
 521       int i;
 522       unsigned int last_file_idx = (target_directory_specified
 523                                     ? n_files - 1
 524                                     : n_files - 2);
 525
 526       if (!target_directory_specified && !dest_is_dir)
 527         error (1, 0,
 528            _("when making multiple links, last argument must be a directory"));
 529       for (i = 0; i <= last_file_idx; ++i)
 530         errors += do_link (file[i], target_directory);
 531     }
 532   else
 533     {
 534       struct stat source_stats;
 535       const char *source;
 536       char *dest;
 537       char *new_dest;
 538
 539       source = file[0];
 540       dest = file[1];
 541
 542       /* When the destination is specified with a trailing slash and the
 543          source exists but is not a directory, convert the user's command
 544          `ln source dest/' to `ln source dest/basename(source)'.  */
 545
 546       if (dest[strlen (dest) - 1] == '/'
 547           && lstat (source, &source_stats) == 0
 548           && !S_ISDIR (source_stats.st_mode))
 549         {
 550           PATH_BASENAME_CONCAT (new_dest, dest, source);
 551         }
 552       else
 553         {
 554           new_dest = dest;
 555         }
 556
 557       errors = do_link (source, new_dest);
 558     }
 559
 560   if (verbose)
 561     close_stdout ();
 562   exit (errors != 0);
 563 }