trap for cleanup on exit in Bash Scripting - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the trap command do in bash scripting?

The trap command lets you run a specific command or script when the shell receives certain signals or when the script exits. It is often used to clean up temporary files or reset settings.

beginner

How do you use trap to run a cleanup function when a script exits?

You write a cleanup function and then use trap cleanup EXIT. This means the cleanup function runs automatically when the script finishes or is interrupted.

intermediate

Why is it useful to trap the EXIT signal in a script?

Trapping EXIT ensures that cleanup code runs no matter how the script ends, whether normally or due to an error or interruption. This helps keep your system clean and avoids leftover temporary files.

intermediate

What happens if you trap signals like INT or TERM in a script?

Trapping INT (interrupt) or TERM (terminate) lets your script handle those signals gracefully, such as cleaning up before exiting instead of stopping immediately.

beginner

Show a simple example of a bash script that creates a temp file and deletes it on exit using trap.

Example:

#!/bin/bash

tempfile=$(mktemp)

echo "Temp file created: $tempfile"

cleanup() {
  echo "Removing temp file"
  rm -f "$tempfile"
}

trap cleanup EXIT

# Script work here
sleep 5

What signal does trap cleanup EXIT catch in a bash script?

A Keyboard interrupt only

B System shutdown

C Script exit (normal or interrupted)

D File deletion

The EXIT signal triggers when the script ends for any reason, normal or interrupted.

Which command creates a temporary file in bash?

A tempfile

B mktemp

C touch temp

D createfile

mktemp safely creates a unique temporary file.

Why use trap to catch signals like INT or TERM?

A To run cleanup code before the script stops

B To speed up the script

C To ignore errors

D To create new files

Trapping these signals lets the script clean up before exiting.

What happens if you don’t use trap for cleanup in a script that creates temp files?

A Files are deleted automatically

B Script runs faster

C Script won’t run

D Temp files may remain and clutter the system

Without cleanup, temporary files can stay and waste space.

Which of these is a correct way to set a trap for cleanup on exit?

A trap cleanup EXIT

B trap EXIT cleanup

C trap cleanup SIGINT

D trap EXIT

The syntax is trap <command> <signal>, so trap cleanup EXIT is correct.

Explain how the trap command helps with cleanup in bash scripts.

Think about what happens when a script ends or is interrupted.

Describe a simple bash script scenario where trapping EXIT is important and what it does.

Imagine you create a file that should be deleted no matter how the script ends.