ln(1)

NAME

ln — link files and directories

SYNOPSIS

ln [-f] [-i] [-s] file1 new_file

ln [-f] [-i] [-s] file1 [file2]... dest_directory

ln [-f] [-i] [-s] directory1 [directory2]... dest_directory

DESCRIPTION

The ln command links:

file1 to a new or existing new_file,
file1 to a new or existing file named file1 in existing dest_directory,
file1, file2, ... to new or existing files of the same name in existing dest_directory,
directory1, directory2, ... to new directories of the same name in existing dest_directory,
or it creates symbolic links between files or between directories.

If links are to dest_directory, corresponding file or directory names in that directory are linked to file1, file2, ..., or directory1, directory2, ..., etc., as appropriate. If two or more existing files or directories (excluding destination file name new_file) are specified, the destination must be a directory. If new_file already exists as a regular file (or link to another file), its contents (or the existing link) and its ACL are destroyed only if the -f option is specified. The ACL on the new_file after the link is the same as that of the source_file file.

If the -f and -i options are specified and the link being created is the name of an existing link or ordinary file and the access permissions of the file forbid writing, ln asks permission to overwrite the file. If the access permissions of the directory forbid writing, ln aborts and returns with the error message:

cannot unlink new_file

(even if the file is an ordinary file and not a link to another file). When asking for permission to overwrite an existing file or link, ln prints the mode (see chmod(2) and Access Control Lists below), followed by the first letters of the words yes and no in the current native language, prompting for a response, and reading one line from the standard input. If the response is affirmative and is permissible, the operation occurs; if not, the command proceeds to the next source file, if any.

Hard links are created with the same ownerships and permissions as the file or directory to which they are linked. If ownership or permissions are changed on a link or file, the same changes appear on corresponding hard links. The ln command does not permit hard links to a directory.

Symbolic links are created with the ownership of the creator and the permissions are of the creator's current umask. Once created, the symbolic link ownership and permissions will not change, since the mode and ownership of the symbolic link is ignored by the system.

If file1 is a file and new_file is a link to an existing file or an existing file with other links, new_file is disassociated from the existing file and links and linked to file1. When ln creates a link to a new or existing file name, ownerships and permissions are always identical to those for the file to which it is linked. If chown, chgrp, or chmod is used to change ownership or permissions of a file or link, the change applies to the file and all associated links. The last modification time and last access time of the file and all associated links are identical (see chown(1) and chmod(1)).

For a discussion of symbolic links, see symlink(4).

Options

The ln command recognizes the following options:

-f: Force existing destination path names to be removed to allow the link.
-i: Write a prompt to the standard error output requesting confirmation for each link that would overwrite an existing file. This option takes effect only if used in conjunction with the -f option.
-s: Cause ln to create symbolic links instead of the usual hard links. A symbolic link contains the name of the file to which it is linked. The referenced file is used when an open() operation is performed on the link (see open(2)). A stat() on a symbolic link returns the linked-to file; an lstat() must be performed to obtain information about the link (see stat(2)). A readlink() call can be used to read the contents of the symbolic link (see readlink(2)). Symbolic links may span file systems and refer to directories.

Access Control Lists (ACLs)

If optional ACL entries are associated with new_file, ln displays a plus sign (+) after the access mode when asking permission to overwrite the file.

If new_file is a new file, it inherits the access control list of file1, altered to reflect any difference in ownership between the two files (see acl(5) and aclv(5)). In JFS file systems, new files created by ln do not inherit their parent directory's default ACL entries (if any), but instead retain their original ACLs.

EXTERNAL INFLUENCES

Environment Variables

LC_CTYPE determines the interpretation of text as single byte and/or multibyte characters.

LANG and LC_CTYPE determine the local language equivalent of y (for yes/no queries).

LANG determines the language in which messages are displayed.

If LC_CTYPE is not specified in the environment or is set to the empty string, the value of LANG is used as a default for each unspecified or empty variable. If LANG is not specified or is set to the empty string, a default of C (see lang(5)) is used instead of LANG. If any internationalization variable contains an invalid setting, ln behaves as if all internationalization variables are set to C. See environ(5).

International Code Set Support

Single byte and multibyte character code sets are supported.

EXAMPLES

The following command creates file1 and file2 in dest_dir, which are linked back to the original files file1 and file2:

ln -f file1 file2 dest_dir 

If file1 and/or file2 exists in the destination directory, it is removed and replaced by a link to file1 or file2, respectively. If existing file file1 or file2 is a link to another file or a file with links, the existing file remains. Only the link is broken and replaced by a new link to file1 or file2.

WARNINGS

ln does not create hard links across file systems.

DEPENDENCIES

NFS

Access control lists of networked files are summarized (as returned in st_mode by stat()), but not copied to the new file. When using ln on such files, a + is not printed after the mode value when asking for permission to overwrite a file.

AUTHOR

ln was developed by AT&T, the University of California, Berkeley and HP.

STANDARDS CONFORMANCE

ln: SVID2, SVID3, XPG2, XPG3, XPG4, POSIX.2