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ln(1)
NAME
ln - Make a hard link or a symbolic link to a file
SYNOPSIS
ln [-fs] sourcename [targetname]
ln [-fs] sourcename... targetdirectory
ln [-fns] sourcename targetname
ln [-fns] sourcename... targetdirectory
STANDARDS
Interfaces documented on this reference page conform to industry standards
as follows:
ln: XCU5.0
Refer to the standards(5) reference page for more information about
industry standards and associated tags.
OPTIONS
-f Forces the removal of existing target path names before linking.
-s [Tru64 UNIX] Creates symbolic links.
-n [Tru64 UNIX] If the target already exists, do not create the link, and
issue an error message. The -f option overrides the -n option. To use
the -n option, the CMD_ENV environment variable must be set to svr4.
OPERANDS
sourcename
Path name of a file to be linked.
targetname
The path name of the new directory entry to be created.
targetdirectory
A path name of an existing directory in which new entries are to be
created.
DESCRIPTION
A link is a directory entry that refers to a file. Usually, sourcename is
an existing file, and targetname does not exist. Thus, targetname becomes
a new name, or pseudonym for sourcename. A file, together with its size
and all its protection information, can have several links to it. There
are two kinds of links: hard links and symbolic links.
[Tru64 UNIX] By default ln makes hard links. A hard link to a file is
indistinguishable from the original directory entry. Changes to either
file affect both files. Hard links must be made to files in the local file
system: they cannot span file systems and cannot refer to directories.
[Tru64 UNIX] With the -s option, the command makes symbolic links,
including Context Dependent Symbolic Links (CDSLs). 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. A stat() on a
symbolic link returns the linked-to file. An lstat() must be done to obtain
information about the link. The readlink() call can be used to read the
contents of a symbolic link. Symbolic links can span file systems and can
refer to directories.
Given one or two arguments, ln creates a link to an existing sourcename
file. If targetname is omitted, then sourcename is used for the link, but
it must be created in a different directory than that of the source file.
If targetname is given, the link has that name. The targetname can also be
a directory in which to place the link; otherwise, it is placed in the
current directory. If only the directory is specified, the link is made to
the last component of the sourcename file.
Given more than two arguments, ln makes links to all the specified files
(sourcename) in the specified targetdirectory. The links made have the same
name as the files to which they are being linked.
If targetname exists, the command aborts unless the -f option is used.
SVID and System V Release 4 Conformance
[Tru64 UNIX] When the environment variable CMD_ENV is set to svr4, the
behavior of the base ln command is compatible with its behavior under
System V Release 4. There is also a version of the ln command provided in
the System V habitat that is conformant with the SVID standard. For more
information on the System V habitat, see the Command and Shell User's
Guide.
This section documents the behavior of the habitat version, and of the base
version with CMD_ENV set to svr4, insofar as the behavior differs from that
of the base ln command without CMD_ENV set. This section discusses only
hard links.
[Tru64 UNIX] In contrast to the base ln command without CMD_ENV set, these
versions of ln silently overwrite an existing targetname if it is not a
directory and has write permission. The -n option, available only in the
base command when CMD_ENV is set, prevents overwriting such an existing
target. Thus, for such an existing targetname, the base command ln -n with
CMD_ENV set behaves the same as does the base command ln with no options
and with CMD_ENV not set.
[Tru64 UNIX] If the targetname exists, is not a directory, and does not
have write permission, three possible conditions can exist, with each
condition producing a different behavior:
· [Tru64 UNIX] If the standard input is not a terminal, the command
attempts to silently unlink targetname and link the source file to it.
· [Tru64 UNIX] If the standard input is a terminal and the command line
does not include the -f option, the command prompts the user for
permission to unlink targetname. The habitat command compares the user
response to the system defined values for YESSTR and NOSTR. If the
user response matches the value for YESSTR, the command attempts to
unlink the target file and link the source file to targetname. If the
user response matches NOSTR, the command aborts. Similarly, with the
base command and CMD_ENV set, the operation aborts unless the user
response begins with a y.
· [Tru64 UNIX] If the standard input is a terminal and the command line
includes the -f option, the command attempts to silently unlink
targetname and link the source file to it.
NOTES
[Tru64 UNIX] You cannot link files across file systems without using the
-s option. That is, links across file systems must be symbolic links.
EXIT STATUS
The following exit values are returned:
0 All the specified files were linked successfully.
>0 An error occurred.
EXAMPLES
1. The following example creates a link (also called an alias) to a file:
ln chap1 intro
The previous command links chap1 to the intro file. If intro does not
already exist, the file name is created. If intro does exist and
permissions allow, the file is replaced by a link to chap1. The
following command forces the link even if intro exists and permissions
do not allow it to be overwritten:
ln -f chap1 intro
The previous command causes chap1 and intro to refer to the same file.
Any changes made to one file also appear in the other file. If one
name is deleted with the rm command, the file is not actually deleted
because it remains under the other name.
2. The following command links a file to the same name in an existing
directory:
ln index manual
The previous command links index to the new name manual/index.
3. The following command links several files to names in another
directory:
ln chap2 jim/chap3 /u/manual
The previous command links chap2 to the new name /u/manual/chap2 and
links jim/chap3 to /u/manual/chap3.
4. The following command uses ln with pattern-matching characters:
ln manual/* .
The previous command links all files in the directory manual into the
current directory (.), giving them the same names they have in manual.
Note that you must type a space between the * (asterisk) and the .
(dot).
5. The following command creates a link to the final component of a path
name:
ln -s /a/b/c/d/e
This creates a link, e, in the current directory to the file
/a/b/c/d/e.
6. The following command creates a link to a directory. In this example,
t1 is a subdirectory under d1:
ln -s /d1/t1 /d2
This creates a link from /d1/t1 to /d2 as follows:
# ls -lF /d2
lrwxrwxrwx 1 root system 11 Dec 13 14:00 /d2@ -> /d1/t1/
The path name for sourcename must be specified if the sourcename
differs from that of the targetdirectory. If the path name is not
specified, a link is created to a file, not to the intended directory.
For example, if the path name was not specified in this example, ls -
s t1 /d2 creates a link to a file named t1, instead of the directory
/d1/t1.
ENVIRONMENT VARIABLES
The following environment variables affect the execution of ln:
CMD_ENV
[Tru64 UNIX] When this environment variable is set to svr4, the
behavior of the ln command is compatible with its behavior under System
V Release 4. The -n option requires that this environment variable be
set to svr4.
LANG
Provides a default value for the internationalization variables that
are unset or null. If LANG is unset or null, the corresponding value
from the default locale is used. If any of the internationalization
variables contain an invalid setting, the utility behaves as if none of
the variables had been defined.
LC_ALL
If set to a non-empty string value, overrides the values of all the
other internationalization variables.
LC_CTYPE
Determines the locale for the interpretation of sequences of bytes of
text data as characters (for example, single-byte as opposed to
multibyte characters in arguments).
LC_MESSAGES
Determines the locale for the format and contents of diagnostic
messages written to standard error.
NLSPATH
Determines the location of message catalogues for the processing of
LC_MESSAGES.
SEE ALSO
Commands: cp(1), mv(1), rm(1)
Functions: chmod(2), link(2), open(2), readlink(2), stat(2), symlink(2)
Standards: standards(5)
Command and Shell User's Guide
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Index for
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Alphabetical
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Top of
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