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 multi- ple 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 sym- bolic 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 indistinguish- able from the original directory entry; any changes to a file are effec- tively 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 speci- fied, 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 sup- plied, neither of which may specify a directory. No options may be sup- plied in this simple mode of operation, which performs a link(2) opera- tion 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 vari- ant symlink may resolve to different paths based on context. The facil- ity 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 sym- links.

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