What is your single most favorite command-line trick using Bash? [closed]

We all know how to use <ctrl>-R to reverse search through history, but did you know you can use <ctrl>-S to forward search if you set stty stop ""? Also, have you ever tried running bind -p to see all of your keyboard shortcuts listed? There are over 455 on Mac OS X by default.

What is your single most favorite obscure trick, keyboard shortcut or shopt configuration using bash?

Solution 1:

Renaming/moving files with suffixes quickly:
cp /home/foo/realllylongname.cpp{,-old}

This expands to:
cp /home/foo/realllylongname.cpp /home/foo/realllylongname.cpp-old

Solution 2:

cd -

It's the command-line equivalent of the back button (takes you to the previous directory you were in).

Solution 3:

Another favorite:

!!

Repeats your last command. Most useful in the form:

sudo !!

Solution 4:

My favorite is '^string^string2' which takes the last command, replaces string with string2 and executes it

$ ehco foo bar baz
bash: ehco: command not found
$ ^ehco^echo
foo bar baz

Bash command line history guide