DragonFly On-Line Manual Pages
LN(1) DragonFly General Commands Manual LN(1)
NAME
ln, link -- link files
SYNOPSIS
ln [-L | -P | -s [-F]] [-f | -iw] [-hnv] source_file [target_file]
ln [-L | -P | -s [-F]] [-f | -iw] [-hnv] source_file ... target_dir
link source_file target_file
DESCRIPTION
The ln utility creates a new directory entry (linked file) for the file
name specified by target_file. The target_file will be created with the
same file modes as the source_file. It is useful for maintaining
multiple copies of a file in many places at once without using up storage
for the ``copies''; instead, a link ``points'' to the original copy.
There are two types of links; hard links and symbolic links. How a link
``points'' to a file is one of the differences between a hard and
symbolic link.
The options are as follows:
-F If the target file already exists and is a directory, then remove
it so that the link may occur. The -F option should be used with
either -f or -i options. If none is specified, -f is implied. The
-F option is a no-op unless -s option is specified.
-L When creating a hard link to a symbolic link, create a hard link to
the target of the symbolic link. This is the default. This option
cancels the -P option.
-P When creating a hard link to a symbolic link, create a hard link to
the symbolic link itself. This option cancels the -L option.
-f If the target file already exists, then unlink it so that the link
may occur. (The -f option overrides any previous -i and -w
options.)
-h If the target_file or target_dir is a symbolic link, do not follow
it. This is most useful with the -f option, to replace a symlink
which may point to a directory.
-i Cause ln to write a prompt to standard error if the target file
exists. If the response from the standard input begins with the
character `y' or `Y', then unlink the target file so that the link
may occur. Otherwise, do not attempt the link. (The -i option
overrides any previous -f options.)
-n Same as -h, for compatibility with other ln implementations.
-s Create a symbolic link.
-v Cause ln to be verbose, showing files as they are processed.
-w Warn if the source of a symbolic link does not currently exist.
By default, ln makes hard links. A hard link to a file is
indistinguishable from the original directory entry; any changes to a
file are effectively independent of the name used to reference the file.
Directories may not be hardlinked, and hard links may not span file
systems.
A symbolic link contains the name of the file to which it is linked. The
referenced file is used when an open(2) operation is performed on the
link. A stat(2) on a symbolic link will return the linked-to file; an
lstat(2) must be done to obtain information about the link. The
readlink(2) call may be used to read the contents of a symbolic link.
Symbolic links may span file systems and may refer to directories.
Given one or two arguments, ln creates a link to an existing file
source_file. If target_file is given, the link has that name;
target_file may also be a directory in which to place the link; otherwise
it is placed in the current directory. If only the directory is
specified, the link will be made to the last component of source_file.
Given more than two arguments, ln makes links in target_dir to all the
named source files. The links made will have the same name as the files
being linked to.
When the utility is called as link, exactly two arguments must be
supplied, neither of which may specify a directory. No options may be
supplied in this simple mode of operation, which performs a link(2)
operation using the two passed arguments.
VARIANT SYMLINKS
DragonFly supports a special kind of dynamic symbolic link called a
variant symlink. The source_file of a variant symlink may contain one or
more variable names. Each of these variable names is enclosed in braces
and preceded by a dollar sign in the style of variable references in
sh(1) and csh(1).
Whenever a variant symlink is followed, each variable found in
source_file is replaced by its associated value. In this manner, a
variant symlink may resolve to different paths based on context. The
facility supports per-process, per-user, and system-wide varsyms.
Varsym variables can be set with the varsym(1) utility. Regular
environ(7) environment variables are not used to resolve variant
symlinks.
EXAMPLES
Create a symbolic link named /home/src and point it to /usr/src:
# ln -s /usr/src /home/src
Hard link /usr/local/bin/fooprog to file /usr/local/bin/fooprog-1.0:
# ln /usr/local/bin/fooprog-1.0 /usr/local/bin/fooprog
As an exercise, try the following commands:
# ls -i /bin/[
11553 /bin/[
# ls -i /bin/test
11553 /bin/test
Note that both files have the same inode; that is, /bin/[ is essentially
an alias for the test(1) command. This hard link exists so test(1) may
be invoked from shell scripts, for example, using the if [ ] construct.
In the next example, the second call to ln removes the original foo and
creates a replacement pointing to baz:
# mkdir bar baz
# ln -s bar foo
# ln -shf baz foo
Without the -h option, this would instead leave foo pointing to bar and
inside foo create a new symlink baz pointing to itself. This results
from directory-walking.
An easy rule to remember is that the argument order for ln is the same as
for cp(1): The first argument needs to exist, the second one is created.
A simple variable symlink example:
sysctl vfs.varsym_enable=1
ln -s 'a${fubar}b' test
echo 'Hello' > axxb
echo 'Goodbye' > ayyb
varsym fubar=xx; cat test
varsym fubar=yy; cat test
COMPATIBILITY
The -h, -i, -n, -v and -w options are non-standard and their use in
scripts is not recommended. They are provided solely for compatibility
with other ln implementations.
Variant symlinks are unique (among BSDs) to DragonFly.
The -F option is a FreeBSD extension and should not be used in portable
scripts.
SEE ALSO
varsym(1), link(2), lstat(2), readlink(2), stat(2), symlink(2),
symlink(7)
STANDARDS
The ln utility conforms to IEEE Std 1003.2-1992 (``POSIX.2'').
The simplified link command conforms to Version 2 of the Single UNIX
Specification (``SUSv2'').
HISTORY
An ln command appeared in Version 1 AT&T UNIX.
DragonFly 4.1 March 23, 2015 DragonFly 4.1