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b5e741091d
encounters an existing destination file, and gets an affirmative response, then first try to unlink the destination file rather than simply failing. Suggestion from Karl Berry.
549 lines
17 KiB
C
549 lines
17 KiB
C
/* `ln' program to create links between files.
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Copyright (C) 86, 89, 90, 91, 1995-2005 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software Foundation,
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Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
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/* Written by Mike Parker and David MacKenzie. */
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#include <config.h>
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#include <stdio.h>
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#include <sys/types.h>
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#include <getopt.h>
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#include "system.h"
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#include "same.h"
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#include "backupfile.h"
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#include "dirname.h"
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#include "error.h"
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#include "quote.h"
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#include "yesno.h"
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/* The official name of this program (e.g., no `g' prefix). */
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#define PROGRAM_NAME "ln"
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#define AUTHORS "Mike Parker", "David MacKenzie"
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#ifndef ENABLE_HARD_LINK_TO_SYMLINK_WARNING
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# define ENABLE_HARD_LINK_TO_SYMLINK_WARNING 0
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#endif
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/* In being careful not even to try to make hard links to directories,
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we have to know whether link(2) follows symlinks. If it does, then
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we have to *stat* the `source' to see if the resulting link would be
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to a directory. Otherwise, we have to use *lstat* so that we allow
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users to make hard links to symlinks-that-point-to-directories. */
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#if LINK_FOLLOWS_SYMLINKS
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# define STAT_LIKE_LINK(File, Stat_buf) \
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stat (File, Stat_buf)
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#else
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# define STAT_LIKE_LINK(File, Stat_buf) \
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lstat (File, Stat_buf)
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#endif
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/* Construct a string NEW_DEST by concatenating DEST, a slash, and
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basename(SOURCE) in alloca'd memory. Don't modify DEST or SOURCE. */
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#define FILE_BASENAME_CONCAT(new_dest, dest, source) \
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do \
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{ \
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const char *source_base; \
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char *tmp_source; \
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size_t buf_len = strlen (source) + 1; \
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\
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tmp_source = alloca (buf_len); \
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memcpy (tmp_source, (source), buf_len); \
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strip_trailing_slashes (tmp_source); \
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source_base = base_name (tmp_source); \
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\
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(new_dest) = alloca (strlen ((dest)) + 1 \
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+ strlen (source_base) + 1); \
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stpcpy (stpcpy (stpcpy ((new_dest), (dest)), "/"), source_base);\
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} \
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while (0)
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/* The name by which the program was run, for error messages. */
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char *program_name;
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/* FIXME: document */
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static enum backup_type backup_type;
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/* A pointer to the function used to make links. This will point to either
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`link' or `symlink'. */
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static int (*linkfunc) ();
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/* If true, make symbolic links; otherwise, make hard links. */
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static bool symbolic_link;
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/* If true, ask the user before removing existing files. */
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static bool interactive;
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/* If true, remove existing files unconditionally. */
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static bool remove_existing_files;
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/* If true, list each file as it is moved. */
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static bool verbose;
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/* If true, allow the superuser to *attempt* to make hard links
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to directories. However, it appears that this option is not useful
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in practice, since even the superuser is prohibited from hard-linking
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directories on most (all?) existing systems. */
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static bool hard_dir_link;
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/* If nonzero, and the specified destination is a symbolic link to a
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directory, treat it just as if it were a directory. Otherwise, the
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command `ln --force --no-dereference file symlink-to-dir' deletes
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symlink-to-dir before creating the new link. */
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static bool dereference_dest_dir_symlinks = true;
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static struct option const long_options[] =
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{
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{"backup", optional_argument, NULL, 'b'},
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{"directory", no_argument, NULL, 'F'},
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{"no-dereference", no_argument, NULL, 'n'},
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{"no-target-directory", no_argument, NULL, 'T'},
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{"force", no_argument, NULL, 'f'},
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{"interactive", no_argument, NULL, 'i'},
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{"suffix", required_argument, NULL, 'S'},
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{"target-directory", required_argument, NULL, 't'},
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{"symbolic", no_argument, NULL, 's'},
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{"verbose", no_argument, NULL, 'v'},
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{GETOPT_HELP_OPTION_DECL},
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{GETOPT_VERSION_OPTION_DECL},
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{NULL, 0, NULL, 0}
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};
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/* FILE is the last operand of this command. Return true if FILE is a
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directory. But report an error there is a problem accessing FILE,
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or if FILE does not exist but would have to refer to an existing
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directory if it referred to anything at all. */
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static bool
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target_directory_operand (char const *file)
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{
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char const *b = base_name (file);
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size_t blen = strlen (b);
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bool looks_like_a_dir = (blen == 0 || ISSLASH (b[blen - 1]));
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struct stat st;
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int err = ((dereference_dest_dir_symlinks ? stat : lstat) (file, &st) == 0
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? 0 : errno);
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bool is_a_dir = !err && S_ISDIR (st.st_mode);
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if (err && err != ENOENT)
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error (EXIT_FAILURE, err, _("accessing %s"), quote (file));
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if (is_a_dir < looks_like_a_dir)
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error (EXIT_FAILURE, err, _("target %s is not a directory"), quote (file));
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return is_a_dir;
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}
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/* Make a link DEST to the (usually) existing file SOURCE.
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Symbolic links to nonexistent files are allowed.
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If DEST_IS_DIR, put the link to SOURCE in the DEST directory.
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Return true if successful. */
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static bool
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do_link (const char *source, const char *dest, bool dest_is_dir)
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{
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struct stat source_stats;
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struct stat dest_stats;
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char *dest_backup = NULL;
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bool lstat_ok = false;
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/* Use stat here instead of lstat.
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On SVR4, link does not follow symlinks, so this check disallows
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making hard links to symlinks that point to directories. Big deal.
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On other systems, link follows symlinks, so this check is right. */
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if (!symbolic_link)
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{
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if (STAT_LIKE_LINK (source, &source_stats) != 0)
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{
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error (0, errno, _("accessing %s"), quote (source));
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return false;
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}
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if (ENABLE_HARD_LINK_TO_SYMLINK_WARNING
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&& S_ISLNK (source_stats.st_mode))
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{
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error (0, 0, _("%s: warning: making a hard link to a symbolic link\
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is not portable"),
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quote (source));
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}
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if (!hard_dir_link && S_ISDIR (source_stats.st_mode))
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{
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error (0, 0, _("%s: hard link not allowed for directory"),
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quote (source));
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return false;
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}
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}
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if (dest_is_dir)
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{
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/* Treat DEST as a directory; build the full filename. */
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char *new_dest;
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FILE_BASENAME_CONCAT (new_dest, dest, source);
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dest = new_dest;
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}
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if (remove_existing_files || interactive || backup_type != no_backups)
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{
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lstat_ok = (lstat (dest, &dest_stats) == 0);
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if (!lstat_ok && errno != ENOENT)
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{
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error (0, errno, _("accessing %s"), quote (dest));
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return false;
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}
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}
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/* If --force (-f) has been specified without --backup, then before
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making a link ln must remove the destination file if it exists.
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(with --backup, it just renames any existing destination file)
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But if the source and destination are the same, don't remove
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anything and fail right here. */
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if (remove_existing_files
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&& lstat_ok
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/* Allow `ln -sf --backup k k' to succeed in creating the
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self-referential symlink, but don't allow the hard-linking
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equivalent: `ln -f k k' (with or without --backup) to get
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beyond this point, because the error message you'd get is
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misleading. */
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&& (backup_type == no_backups || !symbolic_link)
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&& (!symbolic_link || stat (source, &source_stats) == 0)
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&& SAME_INODE (source_stats, dest_stats)
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/* The following detects whether removing DEST will also remove
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SOURCE. If the file has only one link then both are surely
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the same link. Otherwise check whether they point to the same
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name in the same directory. */
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&& (source_stats.st_nlink == 1 || same_name (source, dest)))
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{
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error (0, 0, _("%s and %s are the same file"),
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quote_n (0, source), quote_n (1, dest));
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return false;
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}
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if (lstat_ok)
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{
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if (S_ISDIR (dest_stats.st_mode))
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{
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error (0, 0, _("%s: cannot overwrite directory"), quote (dest));
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return false;
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}
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if (interactive)
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{
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fprintf (stderr, _("%s: replace %s? "), program_name, quote (dest));
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if (!yesno ())
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return true;
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remove_existing_files = true;
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}
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if (backup_type != no_backups)
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{
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char *tmp_backup = find_backup_file_name (dest, backup_type);
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size_t buf_len = strlen (tmp_backup) + 1;
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dest_backup = alloca (buf_len);
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memcpy (dest_backup, tmp_backup, buf_len);
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free (tmp_backup);
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if (rename (dest, dest_backup))
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{
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if (errno != ENOENT)
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{
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error (0, errno, _("cannot backup %s"), quote (dest));
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return false;
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}
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else
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dest_backup = NULL;
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}
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}
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}
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if (verbose)
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{
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printf ((symbolic_link
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? _("create symbolic link %s to %s")
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: _("create hard link %s to %s")),
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quote_n (0, dest), quote_n (1, source));
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if (dest_backup)
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printf (_(" (backup: %s)"), quote (dest_backup));
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putchar ('\n');
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}
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if ((*linkfunc) (source, dest) == 0)
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return true;
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/* If the attempt to create a link failed and we are removing or
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backing up destinations, unlink the destination and try again.
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POSIX 1003.1-2004 requires that ln -f A B must unlink B even on
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failure (e.g., when A does not exist). This is counterintuitive,
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and we submitted a defect report
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<http://www.opengroup.org/sophocles/show_mail.tpl?source=L&listname=austin-review-l&id=1795>
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(2004-06-24). If the committee does not fix the standard we'll
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have to change the behavior of ln -f, at least if POSIXLY_CORRECT
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is set. In the meantime ln -f A B will not unlink B unless the
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attempt to link A to B failed because B already existed.
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Try to unlink DEST even if we may have backed it up successfully.
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In some unusual cases (when DEST and DEST_BACKUP are hard-links
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that refer to the same file), rename succeeds and DEST remains.
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If we didn't remove DEST in that case, the subsequent LINKFUNC
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call would fail. */
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if (errno == EEXIST && (remove_existing_files || dest_backup))
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{
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if (unlink (dest) != 0)
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{
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error (0, errno, _("cannot remove %s"), quote (dest));
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return false;
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}
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if (linkfunc (source, dest) == 0)
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return true;
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}
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error (0, errno,
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(symbolic_link
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? _("creating symbolic link %s to %s")
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: _("creating hard link %s to %s")),
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quote_n (0, dest), quote_n (1, source));
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if (dest_backup)
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{
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if (rename (dest_backup, dest))
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error (0, errno, _("cannot un-backup %s"), quote (dest));
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}
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return false;
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}
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void
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usage (int status)
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{
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if (status != EXIT_SUCCESS)
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fprintf (stderr, _("Try `%s --help' for more information.\n"),
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program_name);
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else
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{
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printf (_("\
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Usage: %s [OPTION]... [-T] TARGET LINK_NAME (1st form)\n\
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or: %s [OPTION]... TARGET (2nd form)\n\
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or: %s [OPTION]... TARGET... DIRECTORY (3rd form)\n\
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or: %s [OPTION]... -t DIRECTORY TARGET... (4th form)\n\
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"),
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program_name, program_name, program_name, program_name);
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fputs (_("\
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In the 1st form, create a link to TARGET with the name LINK_NAME.\n\
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In the 2nd form, create a link to TARGET in the current directory.\n\
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In the 3rd and 4th forms, create links to each TARGET in DIRECTORY.\n\
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Create hard links by default, symbolic links with --symbolic.\n\
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When creating hard links, each TARGET must exist.\n\
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\n\
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"), stdout);
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fputs (_("\
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Mandatory arguments to long options are mandatory for short options too.\n\
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"), stdout);
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fputs (_("\
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--backup[=CONTROL] make a backup of each existing destination file\n\
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-b like --backup but does not accept an argument\n\
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-d, -F, --directory allow the superuser to attempt to hard link\n\
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directories (note: will probably fail due to\n\
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system restrictions, even for the superuser)\n\
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-f, --force remove existing destination files\n\
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"), stdout);
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fputs (_("\
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-n, --no-dereference treat destination that is a symlink to a\n\
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directory as if it were a normal file\n\
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-i, --interactive prompt whether to remove destinations\n\
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-s, --symbolic make symbolic links instead of hard links\n\
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"), stdout);
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fputs (_("\
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-S, --suffix=SUFFIX override the usual backup suffix\n\
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-t, --target-directory=DIRECTORY specify the DIRECTORY in which to create\n\
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the links\n\
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-T, --no-target-directory treat LINK_NAME as a normal file\n\
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-v, --verbose print name of each file before linking\n\
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"), stdout);
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fputs (HELP_OPTION_DESCRIPTION, stdout);
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fputs (VERSION_OPTION_DESCRIPTION, stdout);
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fputs (_("\
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\n\
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The backup suffix is `~', unless set with --suffix or SIMPLE_BACKUP_SUFFIX.\n\
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The version control method may be selected via the --backup option or through\n\
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the VERSION_CONTROL environment variable. Here are the values:\n\
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\n\
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"), stdout);
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fputs (_("\
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none, off never make backups (even if --backup is given)\n\
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numbered, t make numbered backups\n\
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existing, nil numbered if numbered backups exist, simple otherwise\n\
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simple, never always make simple backups\n\
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"), stdout);
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printf (_("\nReport bugs to <%s>.\n"), PACKAGE_BUGREPORT);
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}
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exit (status);
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}
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int
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main (int argc, char **argv)
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{
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int c;
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bool ok;
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bool make_backups = false;
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char *backup_suffix_string;
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char *version_control_string = NULL;
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char const *target_directory = NULL;
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bool no_target_directory = false;
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int n_files;
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char **file;
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initialize_main (&argc, &argv);
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program_name = argv[0];
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setlocale (LC_ALL, "");
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bindtextdomain (PACKAGE, LOCALEDIR);
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textdomain (PACKAGE);
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atexit (close_stdout);
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/* FIXME: consider not calling getenv for SIMPLE_BACKUP_SUFFIX unless
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we'll actually use backup_suffix_string. */
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backup_suffix_string = getenv ("SIMPLE_BACKUP_SUFFIX");
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symbolic_link = remove_existing_files = interactive = verbose
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= hard_dir_link = false;
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while ((c = getopt_long (argc, argv, "bdfinst:vFS:T", long_options, NULL))
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!= -1)
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{
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switch (c)
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{
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case 'b':
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make_backups = true;
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if (optarg)
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version_control_string = optarg;
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break;
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case 'd':
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case 'F':
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hard_dir_link = true;
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break;
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case 'f':
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remove_existing_files = true;
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interactive = false;
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break;
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case 'i':
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remove_existing_files = false;
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interactive = true;
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break;
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case 'n':
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dereference_dest_dir_symlinks = false;
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break;
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case 's':
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#ifdef S_ISLNK
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symbolic_link = true;
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#else
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error (EXIT_FAILURE, 0,
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_("symbolic links are not supported on this system"));
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#endif
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break;
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case 't':
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if (target_directory)
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error (EXIT_FAILURE, 0, _("multiple target directories specified"));
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else
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{
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struct stat st;
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if (stat (optarg, &st) != 0)
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error (EXIT_FAILURE, errno, _("accessing %s"), quote (optarg));
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if (! S_ISDIR (st.st_mode))
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error (EXIT_FAILURE, 0, _("target %s is not a directory"),
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quote (optarg));
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}
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target_directory = optarg;
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break;
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case 'T':
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no_target_directory = true;
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break;
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case 'v':
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verbose = true;
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break;
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case 'S':
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make_backups = true;
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backup_suffix_string = optarg;
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break;
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case_GETOPT_HELP_CHAR;
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case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
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default:
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usage (EXIT_FAILURE);
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break;
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}
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}
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n_files = argc - optind;
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file = argv + optind;
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if (n_files <= 0)
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{
|
||
error (0, 0, _("missing file operand"));
|
||
usage (EXIT_FAILURE);
|
||
}
|
||
|
||
if (no_target_directory)
|
||
{
|
||
if (target_directory)
|
||
error (EXIT_FAILURE, 0,
|
||
_("Cannot combine --target-directory "
|
||
"and --no-target-directory"));
|
||
if (n_files != 2)
|
||
{
|
||
if (n_files < 2)
|
||
error (0, 0,
|
||
_("missing destination file operand after %s"),
|
||
quote (file[0]));
|
||
else
|
||
error (0, 0, _("extra operand %s"), quote (file[2]));
|
||
usage (EXIT_FAILURE);
|
||
}
|
||
}
|
||
else if (!target_directory)
|
||
{
|
||
if (n_files < 2)
|
||
target_directory = ".";
|
||
else if (2 <= n_files && target_directory_operand (file[n_files - 1]))
|
||
target_directory = file[--n_files];
|
||
else if (2 < n_files)
|
||
error (EXIT_FAILURE, 0, _("target %s is not a directory"),
|
||
quote (file[n_files - 1]));
|
||
}
|
||
|
||
if (symbolic_link)
|
||
linkfunc = symlink;
|
||
else
|
||
linkfunc = link;
|
||
|
||
if (backup_suffix_string)
|
||
simple_backup_suffix = xstrdup (backup_suffix_string);
|
||
|
||
backup_type = (make_backups
|
||
? xget_version (_("backup type"), version_control_string)
|
||
: no_backups);
|
||
|
||
if (target_directory)
|
||
{
|
||
int i;
|
||
ok = true;
|
||
for (i = 0; i < n_files; ++i)
|
||
ok &= do_link (file[i], target_directory, true);
|
||
}
|
||
else
|
||
ok = do_link (file[0], file[1], false);
|
||
|
||
exit (ok ? EXIT_SUCCESS : EXIT_FAILURE);
|
||
}
|