Bash – your single most favorite command-line trick using Bash?

bashcommand-line

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?

Best Solution

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