!! repeats the last command — forgot sudo? Just run sudo !!. Saves retyping long commands constantly.

apt install something   # permission denied
sudo !!                 # runs: sudo apt install something

Ctrl+R searches your history — start typing any part of a previous command and it reverse-searches. Hit Ctrl+R again to cycle through matches. Far faster than arrow keys.

cd - goes back to where you just were — like the back button for your filesystem. Toggle between two directories constantly without typing paths.

Brace expansion saves repetitive typing — copy, rename, or operate on multiple files in one shot.

cp config.json{,.bak}          # copies to config.json.bak
mkdir -p project/{src,tests,docs}  # creates all three dirs

pgrep and pkill by name, not PID — instead of ps aux | grep thing | awk '{print $2}' | xargs kill, just:

pkill -f "hugo server"   # kills matching processes by name
pgrep -a node            # shows PIDs and full command for node processes