ln.c

linux开发技术详解一书的源码

      if (unlink (dest) && errno != ENOENT)
	{
	  error (0, errno, _("cannot remove %s"), quote (dest));
	  return 1;
	}
    }
  else if (errno != ENOENT)
    {
      error (0, errno, _("accessing %s"), quote (dest));
      return 1;
    }

  if (verbose)
    {
      printf ((symbolic_link
	       ? _("create symbolic link %s to %s")
	       : _("create hard link %s to %s")),
	      quote_n (0, dest), quote_n (1, source));
      if (backup_succeeded)
	printf (_(" (backup: %s)"), quote (dest_backup));
      putchar ('\n');
    }

  if ((*linkfunc) (source, dest) == 0)
    {
      return 0;
    }

  error (0, errno,
	 (symbolic_link
	  ? _("creating symbolic link %s to %s")
	  : _("creating hard link %s to %s")),
	 quote_n (0, dest), quote_n (1, source));

  if (dest_backup)
    {
      if (rename (dest_backup, dest))
	error (0, errno, _("cannot un-backup %s"), quote (dest));
    }
  return 1;
}

void
usage (int status)
{
  if (status != 0)
    fprintf (stderr, _("Try `%s --help' for more information.\n"),
	     program_name);
  else
    {
      printf (_("\
Usage: %s [OPTION]... TARGET [LINK_NAME]\n\
  or:  %s [OPTION]... TARGET... DIRECTORY\n\
  or:  %s [OPTION]... --target-directory=DIRECTORY TARGET...\n\
"),
	      program_name, program_name, program_name);
      fputs (_("\
Create a link to the specified TARGET with optional LINK_NAME.\n\
If LINK_NAME is omitted, a link with the same basename as the TARGET is\n\
created in the current directory.  When using the second form with more\n\
than one TARGET, the last argument must be a directory;  create links\n\
in DIRECTORY to each TARGET.  Create hard links by default, symbolic\n\
links with --symbolic.  When creating hard links, each TARGET must exist.\n\
\n\
"), stdout);
      fputs (_("\
Mandatory arguments to long options are mandatory for short options too.\n\
"), stdout);
      fputs (_("\
      --backup[=CONTROL]      make a backup of each existing destination file\n\
  -b                          like --backup but does not accept an argument\n\
  -d, -F, --directory         hard link directories (super-user only)\n\
  -f, --force                 remove existing destination files\n\
"), stdout);
      fputs (_("\
  -n, --no-dereference        treat destination that is a symlink to a\n\
                                directory as if it were a normal file\n\
  -i, --interactive           prompt whether to remove destinations\n\
  -s, --symbolic              make symbolic links instead of hard links\n\
"), stdout);
      fputs (_("\
  -S, --suffix=SUFFIX         override the usual backup suffix\n\
      --target-directory=DIRECTORY  specify the DIRECTORY in which to create\n\
                                the links\n\
  -v, --verbose               print name of each file before linking\n\
"), stdout);
      fputs (HELP_OPTION_DESCRIPTION, stdout);
      fputs (VERSION_OPTION_DESCRIPTION, stdout);
      fputs (_("\
\n\
The backup suffix is `~', unless set with --suffix or SIMPLE_BACKUP_SUFFIX.\n\
The version control method may be selected via the --backup option or through\n\
the VERSION_CONTROL environment variable.  Here are the values:\n\
\n\
"), stdout);
      fputs (_("\
  none, off       never make backups (even if --backup is given)\n\
  numbered, t     make numbered backups\n\
  existing, nil   numbered if numbered backups exist, simple otherwise\n\
  simple, never   always make simple backups\n\
"), stdout);
      printf (_("\nReport bugs to <%s>.\n"), PACKAGE_BUGREPORT);
    }
  exit (status);
}

int
main (int argc, char **argv)
{
  int c;
  int errors;
  int make_backups = 0;
  char *backup_suffix_string;
  char *version_control_string = NULL;
  char *target_directory = NULL;
  int target_directory_specified;
  unsigned int n_files;
  char **file;
  int dest_is_dir;

  program_name = argv[0];
  setlocale (LC_ALL, "");
  bindtextdomain (PACKAGE, LOCALEDIR);
  textdomain (PACKAGE);

  atexit (close_stdout);

  /* FIXME: consider not calling getenv for SIMPLE_BACKUP_SUFFIX unless
     we'll actually use backup_suffix_string.  */
  backup_suffix_string = getenv ("SIMPLE_BACKUP_SUFFIX");

  symbolic_link = remove_existing_files = interactive = verbose
    = hard_dir_link = 0;
  errors = 0;

  while ((c = getopt_long (argc, argv, "bdfinsvFS:V:", long_options, NULL))
	 != -1)
    {
      switch (c)
	{
	case 0:			/* Long-named option. */
 	  break;

	case 'V':  /* FIXME: this is deprecated.  Remove it in 2001.  */
	  error (0, 0,
		 _("warning: --version-control (-V) is obsolete;  support for\
 it\nwill be removed in some future release.  Use --backup=%s instead."
		   ), optarg);
	  /* Fall through.  */

	case 'b':
	  make_backups = 1;
	  if (optarg)
	    version_control_string = optarg;
	  break;
	case 'd':
	case 'F':
	  hard_dir_link = 1;
	  break;
	case 'f':
	  remove_existing_files = 1;
	  interactive = 0;
	  break;
	case 'i':
	  remove_existing_files = 0;
	  interactive = 1;
	  break;
	case 'n':
	  dereference_dest_dir_symlinks = 0;
	  break;
	case 's':
#ifdef S_ISLNK
	  symbolic_link = 1;
#else
	  error (EXIT_FAILURE, 0,
		 _("symbolic links are not supported on this system"));
#endif
	  break;
	case TARGET_DIRECTORY_OPTION:
	  target_directory = optarg;
	  break;
	case 'v':
	  verbose = 1;
	  break;
	case 'S':
	  make_backups = 1;
	  backup_suffix_string = optarg;
	  break;
	case_GETOPT_HELP_CHAR;
	case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
	default:
	  usage (EXIT_FAILURE);
	  break;
	}
    }

  n_files = argc - optind;
  file = argv + optind;

  if (n_files == 0)
    {
      error (0, 0, _("missing file argument"));
      usage (EXIT_FAILURE);
    }

  target_directory_specified = (target_directory != NULL);
  if (!target_directory)
    target_directory = file[n_files - 1];

  /* If target directory is not specified, and there's only one
     file argument, then pretend `.' was given as the second argument.  */
  if (!target_directory_specified && n_files == 1)
    {
      static char *dummy[2];
      dummy[0] = file[0];
      dummy[1] = ".";
      file = dummy;
      n_files = 2;
      dest_is_dir = 1;
    }
  else
    {
      dest_is_dir = isdir (target_directory);
    }

  if (symbolic_link)
    linkfunc = symlink;
  else
    linkfunc = link;

  if (target_directory_specified && !dest_is_dir)
    {
      error (0, 0, _("%s: specified target directory is not a directory"),
	     quote (target_directory));
      usage (EXIT_FAILURE);
    }

  if (backup_suffix_string)
    simple_backup_suffix = xstrdup (backup_suffix_string);

  backup_type = (make_backups
		 ? xget_version (_("backup type"), version_control_string)
		 : none);

  if (target_directory_specified || n_files > 2)
    {
      unsigned int i;
      unsigned int last_file_idx = (target_directory_specified
				    ? n_files - 1
				    : n_files - 2);

      if (!target_directory_specified && !dest_is_dir)
	error (EXIT_FAILURE, 0,
	   _("when making multiple links, last argument must be a directory"));
      for (i = 0; i <= last_file_idx; ++i)
	errors += do_link (file[i], target_directory);
    }
  else
    {
      struct stat source_stats;
      const char *source;
      char *dest;
      char *new_dest;

      source = file[0];
      dest = file[1];

      /* When the destination is specified with a trailing slash and the
	 source exists but is not a directory, convert the user's command
	 `ln source dest/' to `ln source dest/basename(source)'.  */

      if (dest[strlen (dest) - 1] == '/'
	  && lstat (source, &source_stats) == 0
	  && !S_ISDIR (source_stats.st_mode))
	{
	  PATH_BASENAME_CONCAT (new_dest, dest, source);
	}
      else
	{
	  new_dest = dest;
	}

      errors = do_link (source, new_dest);
    }

  exit (errors != 0);
}