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File: coreutils.info,  Node: ln invocation,  Next: mkdir invocation,  Prev: link invocation,  Up: Special file types

12.2 `ln': Make links between files
===================================

`ln' makes links between files.  By default, it makes hard links; with
the `-s' option, it makes symbolic (or "soft") links.  Synopses:

     ln [OPTION]... [-T] TARGET LINKNAME
     ln [OPTION]... TARGET
     ln [OPTION]... TARGET... DIRECTORY
     ln [OPTION]... -t DIRECTORY TARGET...

   * If two file names are given, `ln' creates a link to the first file
     from the second.

   * If one TARGET is given, `ln' creates a link to that file in the
     current directory.

   * If the `--target-directory' (`-t') option is given, or failing
     that if the last file is a directory and the
     `--no-target-directory' (`-T') option is not given, `ln' creates a
     link to each TARGET file in the specified directory, using the
     TARGETs' names.


   Normally `ln' does not remove existing files.  Use the `--force'
(`-f') option to remove them unconditionally, the `--interactive'
(`-i') option to remove them conditionally, and the `--backup' (`-b')
option to rename them.

   A "hard link" is another name for an existing file; the link and the
original are indistinguishable.  Technically speaking, they share the
same inode, and the inode contains all the information about a
file--indeed, it is not incorrect to say that the inode _is_ the file.
Most systems prohibit making a hard link to a directory; on those where
it is allowed, only the super-user can do so (and with caution, since
creating a cycle will cause problems to many other utilities).  Hard
links cannot cross file system boundaries.  (These restrictions are not
mandated by POSIX, however.)

   "Symbolic links" ("symlinks" for short), on the other hand, are a
special file type (which not all kernels support: System V release 3
(and older) systems lack symlinks) in which the link file actually
refers to a different file, by name.  When most operations (opening,
reading, writing, and so on) are passed the symbolic link file, the
kernel automatically "dereferences" the link and operates on the target
of the link.  But some operations (e.g., removing) work on the link
file itself, rather than on its target.  The owner and group of a
symlink are not significant to file access performed through the link,
but do have implications on deleting a symbolic link from a directory
with the restricted deletion bit set.  On the GNU system, the mode of a
symlink has no significance and cannot be changed, but on some BSD
systems, the mode can be changed and will affect whether the symlink
will be traversed in file name resolution.  *Note Symbolic Links:
(libc)Symbolic Links.

   Symbolic links can contain arbitrary strings; a "dangling symlink"
occurs when the string in the symlink does not resolve to a file.
There are no restrictions against creating dangling symbolic links.
There are trade-offs to using absolute or relative symlinks.  An
absolute symlink always points to the same file, even if the directory
containing the link is moved.  However, if the symlink is visible from
more than one machine (such as on a networked file system), the file
pointed to might not always be the same.  A relative symbolic link is
resolved in relation to the directory that contains the link, and is
often useful in referring to files on the same device without regards
to what name that device is mounted on when accessed via networked
machines.

   When creating a relative symlink in a different location than the
current directory, the resolution of the symlink will be different than
the resolution of the same string from the current directory.
Therefore, many users prefer to first change directories to the
location where the relative symlink will be created, so that
tab-completion or other file resolution will find the same target as
what will be placed in the symlink.

   The program accepts the following options.  Also see *note Common
options::.

`-b'
`--backup[=METHOD]'
     *Note Backup options::.  Make a backup of each file that would
     otherwise be overwritten or removed.

`-d'
`-F'
`--directory'
     Allow users with appropriate privileges to attempt to make hard
     links to directories.  However, note that this will probably fail
     due to system restrictions, even for the super-user.

`-f'
`--force'
     Remove existing destination files.

`-i'
`--interactive'
     Prompt whether to remove existing destination files.

`-L'
`--logical'
     If `-s' is not in effect, and the source file is a symbolic link,
     create the hard link to the file referred to by the symbolic link,
     rather than the symbolic link itself.

`-n'
`--no-dereference'
     Do not treat the last operand specially when it is a symbolic link
     to a directory.  Instead, treat it as if it were a normal file.

     When the destination is an actual directory (not a symlink to one),
     there is no ambiguity.  The link is created in that directory.
     But when the specified destination is a symlink to a directory,
     there are two ways to treat the user's request.  `ln' can treat
     the destination just as it would a normal directory and create the
     link in it.  On the other hand, the destination can be viewed as a
     non-directory--as the symlink itself.  In that case, `ln' must
     delete or backup that symlink before creating the new link.  The
     default is to treat a destination that is a symlink to a directory
     just like a directory.

     This option is weaker than the `--no-target-directory' (`-T')
     option, so it has no effect if both options are given.

`-P'
`--physical'
     If `-s' is not in effect, and the source file is a symbolic link,
     create the hard link to the symbolic link itself.  On platforms
     where this is not supported by the kernel, this option creates a
     symbolic link with identical contents; since symbolic link contents
     cannot be edited, any file name resolution performed through either
     link will be the same as if a hard link had been created.

`-s'
`--symbolic'
     Make symbolic links instead of hard links.  This option merely
     produces an error message on systems that do not support symbolic
     links.

`-S SUFFIX'
`--suffix=SUFFIX'
     Append SUFFIX to each backup file made with `-b'.  *Note Backup
     options::.

`-t DIRECTORY'
`--target-directory=DIRECTORY'
     Specify the destination DIRECTORY.  *Note Target directory::.

`-T'
`--no-target-directory'
     Do not treat the last operand specially when it is a directory or a
     symbolic link to a directory.  *Note Target directory::.

`-v'
`--verbose'
     Print the name of each file after linking it successfully.


   If `-L' and `-P' are both given, the last one takes precedence.  If
`-s' is also given, `-L' and `-P' are silently ignored.  If neither
option is given, then this implementation defaults to `-P' if the
system `link' supports hard links to symbolic links (such as the GNU
system), and `-L' if `link' follows symbolic links (such as on BSD).

   An exit status of zero indicates success, and a nonzero value
indicates failure.

   Examples:

     Bad Example:

     # Create link ../a pointing to a in that directory.
     # Not really useful because it points to itself.
     ln -s a ..

     Better Example:

     # Change to the target before creating symlinks to avoid being confused.
     cd ..
     ln -s adir/a .

     Bad Example:

     # Hard coded file names don't move well.
     ln -s $(pwd)/a /some/dir/

     Better Example:

     # Relative file names survive directory moves and also
     # work across networked file systems.
     ln -s afile anotherfile
     ln -s ../adir/afile yetanotherfile