How to use trap for signal handling in bash

Short answer

trap catches signals like INT, TERM, and EXIT to run cleanup code before a script terminates.

Steps

1. Trap Ctrl+C:

trap "echo 'Interrupted'; exit 1" INT

2. Cleanup on exit:

trap "rm -f /tmp/tempfile" EXIT

3. Ignore a signal:

trap "" HUP

4. Reset to default:

trap - INT

Tips

• Always clean up temporary files and locks with trap.
• ERR trap runs on any command failure when set -E is enabled.
• Define cleanup functions for complex scripts.

Common issues

• kill -9 (SIGKILL) cannot be trapped.
• Nested traps may overwrite each other; save and restore with variables.