4.5.5 Links

There are two methods of associating a file foo with a different filename bar.

• a hard link is a duplicate name for an existing file (ln foo bar),

• a symbolic link, or "symlink", is a special file that points to another file by name (ln -s foo bar).

See the following example for the changes in link counts and the subtle differences in the result of the rm command.

     $ echo "Original Content" > foo
     $ ls -l foo
     -rw-r--r--    1 osamu    osamu           4 Feb  9 22:26 foo
     $ ln foo bar     # hard link
     $ ln -s foo baz  # symlink
     $ ls -l foo bar baz
     -rw-r--r--    2 osamu    osamu           4 Feb  9 22:26 bar
     lrwxrwxrwx    1 osamu    osamu           3 Feb  9 22:28 baz -> foo
     -rw-r--r--    2 osamu    osamu           4 Feb  9 22:26 foo
     $ rm foo
     $ echo "New Content" > foo
     $ cat bar
     Original Content
     $ cat baz
     New Content

The symlink always has nominal file access permissions of "rwxrwxrwx", as shown in the above example, with the effective access permissions dictated by the permissions of the file that it points to.

The . directory links to the directory that it appears in, thus the link count of any new directory starts at 2. The .. directory links to the parent directory, thus the link count of the directory increases with the addition of new subdirectories.