Symbolic and Hard Links — ln

Symbolic Links — ln -s

A link lets you reach the same file under a different name. You create a symbolic link with ln -s target name, and it is a special file that stores the path (location) of the target. When you open name, it automatically follows the stored path to the target. In ls -l, the link's row shows where it points, as name -> target.

printf 'data\n' > target.txt   # Create the target file
ln -s target.txt link.txt     # Create a symbolic link
ls -l                         # Check link.txt -> target.txt
cat link.txt                  # Shows the contents of target.txt

① Create the target file with printf 'data\n' > target.txt.

② Add the option that makes ln create a symbolic link, then pass the target and the new name in that order to create link.txt.

③ Run ls -l and check that the link target appears as link.txt -> target.txt. (When you run it correctly, an explanation appears.)

Hard Links — ln

Without -s, ln target alias creates a hard link. While a symbolic link is a special file that stores a path to the target, a hard link is another name pointing to the same data body. Opening either name gives identical contents, and in ls -l a hard link shows no arrow — it looks like an ordinary file. Keep the distinction in mind: symbolic = a special file storing the target's path, hard = an alias to the same data body.

printf 'shared\n' > base.txt   # Create the target file
ln base.txt hard.txt          # Create a hard link
ls -l                         # hard.txt is listed without an arrow
cat hard.txt                  # Shows the same contents as base.txt

① Create the target file with printf 'shared\n' > base.txt.

② Use ln with no option, passing the target and the alias in that order, to create a hard link called hard.txt.

③ Run ls -l and check that hard.txt is listed like an ordinary file, with no arrow (->).

What Happens When You Delete the Target

Because a symbolic link is a special file that stores a path to the target, it loses what it points to once the target is gone. Because a hard link is another name pointing to the same data body, the contents remain even after the original name is gone. Delete the target and see the difference for yourself.

printf 'v\n' > orig.txt       # Create the target file
ln -s orig.txt sl.txt         # Symbolic link
ln orig.txt hl.txt            # Hard link
rm orig.txt                   # Delete the target
cat sl.txt                    # Loses its target and fails
cat hl.txt                    # Contents remain and can be shown

① Create the target with printf 'v\n' > orig.txt.

② Create a symbolic link with ln -s orig.txt sl.txt and a hard link with ln orig.txt hl.txt.

③ Delete the target with rm orig.txt.

④ Run cat sl.txt and cat hl.txt and compare the difference in results.

⑤ Run ls -l and check how the two links look in ls -l after the deletion.