DragonFly On-Line Manual Pages

LN(1)		       DragonFly General Commands Manual		 LN(1)


ln, link -- make links


ln [-fhinsv] source_file [target_file] ln [-fhinsv] source_file ... target_dir link source_file target_file


The ln utility creates a new directory entry (linked file) which has the same modes as the original 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, then unlink it so that the link may occur. (The -f option overrides any previous -i 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. 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. Hard links may not normally refer to directories and 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.


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.


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


The -h, -i, -n and -v 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.


varsym(1), link(2), lstat(2), readlink(2), stat(2), symlink(2), symlink(7)


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'').


An ln command appeared in Version 1 AT&T UNIX. DragonFly 4.1 September 27, 2009 DragonFly 4.1