[bash] Cleanup hook for temp files

Instead of: tmpfile=$(mktemp) # do stuff with $tmpfile rm "$tmpfile" # hope nothing failed before we got here Just use: cleanup() { rm -f "$tmpfile"; } trap cleanup EXIT tmpfile=$(mktemp) # do stuff with $tmpfile trap runs your function no matter how the script exits -- normal, error, Ctrl+C, kill. Your temp files always get cleaned up. No more orphaned junk in /tmp. Real world: # Lock file that always gets released cleanup() { rm -f /var/run/myapp.lock; } trap cleanup EXIT touch /var/run/myapp.lock # SSH tunnel that always gets torn down cleanup() { kill "$tunnel_pid" 2>/dev/null; } trap cleanup EXIT ssh -fN -L 5432:db:5432 jumpbox & tunnel_pid=$! # Multiple things to clean up cleanup() { rm -f "$tmpfile" "$pidfile" kill "$bg_pid" 2>/dev/null } trap cleanup EXIT The trick is defining trap before creating the resources. If your script dies between mktemp and the rm at the bottom, the file stays. With trap at the top, it never does. Works in bash, zsh, and POSIX sh. One of the few tricks that's actually portable.