LN(1) LN(1)
NAME
ln - make links between files
SYNOPSIS
ln[options] source [dest]
ln[options] source... directory
POSIX options: [-f][--]
GNU options (shortest form): [-bdfinsvF][-S backup-suffix][-V{num-
bered,existing,simple}][--help][--version][--]
DESCRIPTION
There are two concepts of 'link' in Unix, usually called hard link and
soft link. A hard link is just a name for a file. (And a file can have
several names. It is deleted from disk only when the last name is
removed. The number of names is given by ls(1). There is no such thing
as an 'original' name: all names have the same status. Usually, but not
necessarily, all names of a file are found in the filesystem that also
contains its data.)
A soft link (or symbolic link, or symlink) is an entirely different
animal: it is a small special file that contains a pathname. Thus,
soft links can point at files on different filesystems (possibly NFS
mounted from different machines), and need not point to actually exist-
ing files. When accessed (with the open(2) or stat(2) system calls), a
reference to a symlink is replaced by the operating system kernel with
a reference to the file named by the path name. (However, with rm(1)
and unlink(2) the link itself is removed, not the file it points to.
There are special system calls lstat(2) and readlink(2) that read the
status of a symlink and the filename it points to. For various other
system calls there is some uncertainty and variation between operating
systems as to whether the operation acts on the symlink itself, or on
the file pointed to.)
ln makes links between files. By default, it makes hard links; with
the -s option, it makes symbolic (or 'soft') links.
If only one file is given, it links that file into the current direc-
tory, that is, creates a link to that file in the current directory,
with name equal to (the last component of) the name of that file. (This
is a GNU extension.) Otherwise, if the last argument names an existing
directory, ln will create links to each mentioned source file in that
directory, with a name equal to (the last component of) the name of
that source file. (But see the description of the --no-dereference
option below.) Otherwise, if only two files are given, it creates a
link named dest to the file source. It is an error if the last argu-
ment is not a directory and more than two files are given.
By default, ln does not remove existing files or existing symbolic
links. (Thus, it can be used for locking purposes: it will succeed
only if dest did not exist already.) But it can be forced to do so
with the option -f.
On existing implementations, if it is at all possible to make a hard
link to a directory, this may be done by the superuser only. POSIX for-
bids the system call link(2) and the utility ln to make hard links to
directories (but does not forbid hard links to cross filesystem bound-
aries).
POSIXOPTIONS
-f Remove existing destination files.
-- Terminate option list.
GNUOPTIONS
-d,-F,--directory
Allow the super-user to make hard links to directories.
-f,--force
Remove existing destination files.
-i,--interactive
Prompt whether to remove existing destination files.
-n,--no-dereference
When given an explicit destination that is a symlink to a direc-
tory, treat that destination 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 direc-
tory. 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.
-s,--symbolic
Make symbolic links instead of hard links. This option merely
produces an error message on systems that do not support sym-
bolic links.
-v,--verbose
Print the name of each file before linking it.
GNUBACKUPOPTIONS
The GNU versions of programs like cp, mv, ln, install and patch will
make a backup of files about to be overwritten, changed or destroyed if
that is desired. That backup files are desired is indicated by the -b
option. How they should be named is specified by the -V option. In
case the name of the backup file is given by the name of the file
extended by a suffix, this suffix is specified by the -S option.
-b,--backup
Make backups of files that are about to be overwritten or
removed.
-S SUFFIX,--suffix=SUFFIX
Append SUFFIX to each backup file made. If this option is not
specified, the value of the SIMPLE_BACKUP_SUFFIX environment
variable is used. And if SIMPLE_BACKUP_SUFFIX is not set, the
default is '~'.
-V METHOD,--version-control=METHOD
Specify how backup files are named. The METHOD argument can be
'numbered' (or 't'), 'existing' (or 'nil'), or 'never' (or 'sim-
ple'). If this option is not specified, the value of the VER-
SION_CONTROL environment variable is used. And if VERSION_CON-
TROL is not set, the default backup type is 'existing'.
This option corresponds to the Emacs variable 'version-control'.
The valid METHODs are (unique abbreviations are accepted):
t, numbered
Always make numbered backups.
nil, existing
Make numbered backups of files that already have them,
simple backups of the others.
never, simple
Always make simple backups.
GNUSTANDARDOPTIONS
--help Print a usage message on standard output and exit successfully.
--version
Print version information on standard output, then exit success-
fully.
-- Terminate option list.
ENVIRONMENT
The variables LANG, LC_ALL, LC_CTYPE and LC_MESSAGES have the usual
meaning.
CONFORMINGTO
POSIX 1003.2. However, POSIX 1003.2 (1996) does not discuss soft links.
Soft links were introduced by BSD, and do not occur in System V release
3 (and older) systems.
SEEALSO
ls(1), rm(1), link(2), lstat(2), open(2), readlink(2), stat(2),
unlink(2)
NOTES
This page describes ln as found in the fileutils-4.0 package; other
versions may differ slightly. Mail corrections and additions to
aeb cwi.nl. Report bugs in the program to fileutils-
bugsgnu.edu.
GNU fileutils 4.0 1998-11 LN(1)
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