Answer here: What does !#:3 mean in a shell command

Basically, you can use it to shorten a command in combination with ':n', so:

$ cd /home/me/some/super/deep/dir/that/i/do/not/want/to/type/again ; ll !#:2 

Of course this is a bit silly example, because you could just do ll, but you get the idea, it can be used in sh scripts.

Answer here: What does !#:3 mean in a shell command

Basically, you can use it to shorten a command in combination with ':n', so:

$ cd /home/me/some/super/deep/dir/that/i/do/not/want/to/type/again ; ll !#:2 

Of course this is a bit silly example, because you could just do ll, but you get the idea, it can be used in sh scripts.