trap for cleanup on exit in Bash Scripting - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output when the script exits?

Consider this Bash script that sets a trap to clean up a temporary file on exit. What will be printed when the script finishes?

Bash Scripting

#!/bin/bash

tmpfile=$(mktemp)
trap 'echo "Cleaning up $tmpfile"; rm -f "$tmpfile"' EXIT

echo "Temporary file created: $tmpfile"
exit 0

A Temporary file created: /tmp/tmp.abcd1234\nCleaning up /tmp/tmp.abcd1234

B Temporary file created: /tmp/tmp.abcd1234

C Cleaning up /tmp/tmp.abcd1234

D No output

💡 Hint

The trap command runs the cleanup command when the script exits.

The trap on EXIT runs the echo and rm commands when the script finishes, so both lines print.

💻 Command Output

intermediate

What happens if the script is interrupted with Ctrl+C?

Given this Bash script, what output will appear if the user presses Ctrl+C during the sleep?

Bash Scripting

#!/bin/bash

tmpfile=$(mktemp)
trap 'echo "Cleaning up $tmpfile"; rm -f "$tmpfile"' EXIT

echo "Temporary file created: $tmpfile"
sleep 10
exit 0

A Cleaning up /tmp/tmp.abcd1234

B Temporary file created: /tmp/tmp.abcd1234

C Temporary file created: /tmp/tmp.abcd1234\nCleaning up /tmp/tmp.abcd1234

D No output

💡 Hint

The EXIT trap runs even if the script is interrupted.

When Ctrl+C interrupts the script, the EXIT trap runs, printing the cleanup message and removing the file.

📝 Syntax

advanced

Which trap command correctly cleans up on script exit?

You want to run a cleanup command when the script exits. Which trap syntax is correct?

A trap rm -f $tmpfile EXIT

B trap {rm -f $tmpfile} EXIT

C trap (rm -f $tmpfile) EXIT

D trap 'rm -f $tmpfile' EXIT

💡 Hint

trap requires a quoted command string as the first argument.

trap 'commands' SIGNAL expects the commands as a quoted string. Options A, C, D are invalid syntax.

🔧 Debug

advanced

Why does this trap not run the cleanup command?

This script tries to clean up a file on exit but the cleanup command never runs. Why?

Bash Scripting

#!/bin/bash

tmpfile=$(mktemp)
trap 'rm -f $tmpfile' SIGINT

echo "Temporary file: $tmpfile"
sleep 5
exit 0

A Because the trap is set only for SIGINT, not EXIT, so normal exit skips cleanup

B Because $tmpfile is empty inside the trap command

C Because sleep prevents trap from running

D Because trap commands cannot remove files

💡 Hint

EXIT trap runs on any exit, SIGINT only on Ctrl+C.

The trap is set only for SIGINT (Ctrl+C). If the script exits normally, the trap does not run.

🚀 Application

expert

How to ensure cleanup runs even if script is killed by SIGTERM?

You want your Bash script to always remove a temporary file on exit, even if killed by SIGTERM. Which trap commands should you use?

A trap 'rm -f "$tmpfile"' EXIT; trap 'exit' SIGTERM

B trap 'rm -f "$tmpfile"' EXIT; trap 'rm -f "$tmpfile"' SIGTERM

C trap 'rm -f "$tmpfile"' EXIT SIGTERM

D trap 'rm -f "$tmpfile"' SIGTERM

💡 Hint

You can set multiple traps for different signals.

EXIT trap runs on normal exit, but SIGTERM kills immediately unless trapped separately. Setting both traps ensures cleanup.