Most powerful examples of Unix commands or scripts every programmer should know

Question

There are many things that all programmers should know, but I am particularly interested in the Unix/Linux commands that we should all know. For accomplishing tasks that we may

Answer 1

I find commandlinefu.com to be an excellent resource for various shell scripting recipes.

Examples

Common

# Run the last command as root
sudo !!

# Rapidly invoke an editor to write a long, complex, or tricky command
ctrl-x ctrl-e

# Execute a command at a given time
echo "ls -l" | at midnight

Esoteric

# output your microphone to a remote computer's speaker
dd if=/dev/dsp | ssh -c arcfour -C username@host dd of=/dev/dsp