| ln | |
|---|---|
 Example usage of ln utility | |
| Original author | AT&T Bell Laboratories |
| Developers | Variousopen-source andcommercial developers |
| Initial release | November 3, 1971; 54 years ago (1971-11-03) |
| Operating system | Unix,Unix-like,IBM i |
| Platform | Cross-platform |
| Type | Command |
| License | coreutils:GPLv3+ |
ln is ashellcommand for creating a link file to an existingfile ordirectory.[1] By default, the command creates ahard link, but with the-scommand line option, it creates asymbolic link.[2] Most systems disallow a hard link to a directory since such links could disrupt the structure of afile system and interfere with the operation of other utilities.[3] The command can create a symbolic link to non-existent file.[4]
The command appeared in Issue 2 of theX/Open Portability Guidelines.[5] The version inGNU Core Utilities was written by Mike Parker and David MacKenzie.[6]The command is available inWindows viaUnxUtils[7] and has been ported toIBM i.[8]
A link allows more than onepath to refer to the same file.
A hard link is a directory entry that refers to a file'sinode (an internalreference). A file can have multiple hard links – each referring to the sameinode.[9] Creating a hard link does not copy the contents of the file, but merely causes another name to be associated with the same content. When a hard link is created for a file, acounter in its inode is incremented, and removing a hard link results in decrementing the counter. A file is not deleted (to allow reusing its storage space) until its reference count reaches zero.[1][10] A hard link can only refer to an object on the samefile system.[11]
A symbolic link refers to another file by its path (a symbolic reference).[4] When encountered during pathname resolution, modify thepathname resolution to be taken to the location which the symbolic link contains. The content of a symbolic link is the target path, which can also be examined via thereadlink command.[12] A symbolic link may specify a path that does not refer to an existing file. Resolving such a symbolic link will fail until a file is created at its specified path. Also, a symbolic link to an existing file will fail to resolve if the file is moved.[9]
Per theSingle Unix Specification, theln command is specified in the Shell and Utilities (XCU) document.[13]POSIX includes a similar specification.[5]
If neither target file nor target directory are specified, links are created in the currentworking directory.
The specification indicates command line options that must be supported:
-f (force)Clobbers an existing file if the output path specifies an existing file-L If a source operand specifies a symbolic link, create a hard link to the link's target file-P If a source operand specifies a symbolic link, create a hard link to the symbolic link file-s Create symbolic links instead of hard links; causes-L and-P to be silently ignoredIf more than one of the mutually-exclusive options-L and-P is specified, the last option specified determines the resulting behavior.
If the-s option is not specified and neither a-L nor a-P option is specified, the implementation defines which of the-L and-P options is used by default.
The command creates a new link to the path indicated bysource, stored at the path indicated bytarget. The syntax is as follows:
ln [-fs] [-L|-P] source target
The command creates a new link to each file specified by thesource_# operands, stored in an existing directory indicated bytarget_dir.
ln [-fs] [-L|-P] source_1 source_2 ... target_dir
The following creates a hard link to filefoo calledbar.
ln foo bar
The following creates a symbolic link to filefoo calledbar.
ln -s foo bar
ln – Shell and Utilities Reference,The Single UNIX Specification, Version 5 fromThe Open Groupln(1) – Linux General CommandsManual from ManKier.com
ln(1) – Linux User CommandsManualln(1) – FreeBSD General CommandsManualln(1) – NetBSD General CommandsManualln(1) – OpenBSD General CommandsManualln(1) – Darwin andmacOS General CommandsManual| File system | |
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