A symbolic link (or link) is a small file that points to another path. When a program opens the link, it gets the item that the link points to, the target.

Make a link: ln -s

ln -s TARGET LINK makes the link LINK, which points to TARGET:

learner@tidepool:~/shop$ ln -s menus/summer.txt menu.txt
learner@tidepool:~/shop$ ls -l
lrwxrwxrwx 1 learner learner   16 Oct 12 09:14 menu.txt -> menus/summer.txt
drwxr-xr-x 2 learner learner 4096 Oct 12 09:14 menus
learner@tidepool:~/shop$ cat menu.txt
ice tea

In ls -l, a link has the type l, and the arrow -> shows its target.

A relative target is read from the directory of the link, not from your current directory.

Why links are useful

A link gives one fixed name to something that changes. The shop keeps two menus. Programs always read menu.txt. To change the menu, change the link. Do not copy files.

Programs often use this for their versions, or releases: one directory for each release, and a link current to the one that runs.

A broken link

If you delete or move the target, the link stays and points to nothing. This is a broken link:

learner@tidepool:~/shop$ cat menu.txt
cat: menu.txt: No such file or directory

ls -l still lists the link and its old target.

Change where a link points

ln -s refuses a name that exists: File exists. Add flags:

-f replaces the old link. With a link to a directory, also add -n. Without -n, ln goes into the directory and makes the new link there.

rm LINK deletes only the link, never the target.