ln command

ln - Create hard links by default, symbolic links with --symbolic.

ln command in linux is used to create links between files or directories. Links allow you to reference the same file from multiple locations. There are two types of links: hard links and soft (symbolic) links.

Usage: ln [OPTION]... [-T] TARGET LINK_NAME

• OPTION: Flags which enhances the ln abilities.
• TARGET: file or directory you want to link to.
• LINK_NAME: name of the new link.

Examples

• Creating a hard link

  A hard link is a direct reference to the same data on disk as the original file. By default, ln creates hard links.

  $ ln original.txt hardlink.txt
  • Creates a hard link named hardlink.txt pointing to original.txt.
  • Both names point to the same file data and deleting one doesn’t affect the other.
  • Hard links share the same inode (inode is a file data identifier).
  • They only work within the same filesystem.
  • If original.txt is deleted, hardlink.txt still accesses the data.

• Creating a symbolic (soft) link

  A symbolic link (symlink) is a pointer to the original file’s path, like a shortcut. Use the -s (symbolic) option to create a symbolic link.

  $ ln -s original.txt symlink.txt
  • Creates a symbolic link named symlink.txt pointing to original.txt`.
  • If original.txt is deleted, symlink.txt becomes a broken link.
  • Symlinks can point to files or directories across filesystems.
  • They store a path, not the data itself.
  • Use ls -l to see symlinks (e.g., symlink.txt -> original.txt).

• Linking a directory

  Symbolic links are commonly used for directories (hard links to directories are rarely allowed).

  $ ln -s /home/user/docs /home/user/docs_shortcut
  • Creates a symlink docs_shortcut pointing to the docs directory.

• Forcing overwrite

  If the link name already exists, ln will fail unless you use -f (force) to overwrite it.

  $ ln -sf original.txt symlink.txt
  • Overwrites an existing symlink.txt with a new symbolic link to original.txt.

• Preventing overwrites

  Use -n (no-dereference) with symlinks to treat an existing symlink as a file, not its target.

  $ ln -snf newfile.txt symlink.txt
  • Replaces symlink.txt without affecting its original target.

To get help related to the ln command use --help option

$ ln --help
Usage: ln [OPTION]... [-T] TARGET LINK_NAME
  or:  ln [OPTION]... TARGET
  or:  ln [OPTION]... TARGET... DIRECTORY
  or:  ln [OPTION]... -t DIRECTORY TARGET...
In the 1st form, create a link to TARGET with the name LINK_NAME.
In the 2nd form, create a link to TARGET in the current directory.
In the 3rd and 4th forms, create links to each TARGET in DIRECTORY.
Create hard links by default, symbolic links with --symbolic.
By default, each destination (name of new link) should not already exist.
When creating hard links, each TARGET must exist.  Symbolic links
can hold arbitrary text; if later resolved, a relative link is
interpreted in relation to its parent directory.

Mandatory arguments to long options are mandatory for short options too.
      --backup[=CONTROL]      make a backup of each existing destination file
  -b                          like --backup but does not accept an argument
  -d, -F, --directory         allow the superuser to attempt to hard link
                                directories (note: will probably fail due to
                                system restrictions, even for the superuser)
  -f, --force                 remove existing destination files
  -i, --interactive           prompt whether to remove destinations
  -L, --logical               dereference TARGETs that are symbolic links
  -n, --no-dereference        treat LINK_NAME as a normal file if
                                it is a symbolic link to a directory
  -P, --physical              make hard links directly to symbolic links
  -r, --relative              create symbolic links relative to link location
  -s, --symbolic              make symbolic links instead of hard links
  -S, --suffix=SUFFIX         override the usual backup suffix
  -t, --target-directory=DIRECTORY  specify the DIRECTORY in which to create
                                the links
  -T, --no-target-directory   treat LINK_NAME as a normal file always
  -v, --verbose               print name of each linked file
      --help     display this help and exit
      --version  output version information and exit

The backup suffix is '~', unless set with --suffix or SIMPLE_BACKUP_SUFFIX.
The version control method may be selected via the --backup option or through
the VERSION_CONTROL environment variable.  Here are the values:

  none, off       never make backups (even if --backup is given)
  numbered, t     make numbered backups
  existing, nil   numbered if numbered backups exist, simple otherwise
  simple, never   always make simple backups

Using -s ignores -L and -P.  Otherwise, the last option specified controls
behavior when a TARGET is a symbolic link, defaulting to -P.