The
ln
command creates both
hard and soft (symbolic) links (
18.4
)
.
Only UNIX versions with symbolic links have the
-s
option, though:
%
ln
filename linkname
To create a hard link
%
ln -s
filename linkname
To create a symbolic link
In either case,
filename
must already exist. Otherwise you
will get an error message.
If you are using Berkeley UNIX,
linkname
must not exist - if it does, you will get an error.
Under System V,
linkname
may already exist; if you are
allowed to write the file,
ln
destroys its old contents and
creates your link.
If you don't have write access for
linkname
,
ln
asks whether or not it is OK to override the
file's protection.
For example:
%
ln foo bar
ln: override protection 444 for bar?
y
Typing
y
gives
ln
permission to destroy the file
bar
and create
the link.
Note that this will still fail if you don't have write
access to the directory.
You are allowed to omit the
linkname
argument from the
ln
command.
In this case,
ln
takes the last component of
filename
(i.e., everything after the last slash) and uses it
for
linkname
.
Of course, this assumes that
filename
doesn't
refer to the current directory.
If it does, the command will fail:
the link will already exist.
For example, the commands below are the same:
&..
|
%
ln -s ../archive/file.c
%
ln -s ../archive/file.c file.c
|
Both create a link from
file.c
in the current directory to
../archive/file.c
.
ln
also lets you create a group of links with one command,
provided that all of the links are in the same directory.
Here's how:
%
ln
file1 file2 file3 ... filen directory
This command uses the filename from each pathname
(after the last slash) as each link's name. It
then creates all the links within the given
directory
.
For example, the first command below is equivalent to the next two:
%
ln ../s/f1 ../s/f2 current
%
ln ../s/f1 current/f1
%
ln ../s/f2 current/f2
You can replace this list of files with a
wildcard expression (
15.2
)
,
as in:
&.
|
%
ln -s ../newversion/*.[ch]
|
Note that symbolic links can
get out-of-date (
18.6
)
.
[Hard links can also be "broken" in some situations.
For example, a text editor might rename the link
textfile
to
textfile.bak
, then create a new
textfile
during editing.
Previous links to
textfile
will now give you
textfile.bak
.
To track down this problem,
find the links (
17.22
)
to each file.
-
JP
]
To remove a link, either hard or symbolic, use the
rm
command.