a mark of ecphoneme

Have you ever created a directory in a long file path, then have to type out the long file path again with cd? Well no more!

mkdir /a/super/long/file/path/to/my/new/directory/
cd !$

Note: does not work with all shells. I know bash and zsh work.

In some shells the exclamation mark (!) can be used as an event designator to reference the command history. A lot of users have probably come across this for running the last command again, maybe if they forgot to use sudo

$ pacman -Syu
error: you cannot perform this operation unless you are root.
$ sudo !!

It can also be used with a number to run that command from the history, for example to run the very first command in your history incant

!1

Something I use quite a lot is the ability to reference a field from the last command, mostly the last field ($). As shown above you can use it to navigate to a directory you have just created, or anything requiring the last field of the previous command.

You can also reference the first argument using !^ or the command word using !:0. Note the colon before the zero.

These event and word designators are quite extensive so check the manpages for more information.