Custom exit codes (exit N) in Bash Scripting - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does exit N do in a bash script?

exit N stops the script and sends the number N as the exit code to the system. This code tells if the script ended successfully or with an error.

beginner

Why use custom exit codes instead of just exit 0 or exit 1?

<p>Custom exit codes let you show different reasons for failure or success. For example, <code>exit 2</code> might mean "file not found," while <code>exit 3</code> means "permission denied." This helps other scripts or users understand what happened.</p>

beginner

What is the valid range for exit codes in bash scripts?

Exit codes must be between 0 and 255. 0 means success, and any number from 1 to 255 means different errors or statuses.

beginner

How can you check the exit code of the last command in bash?

Use the special variable $?. It holds the exit code of the last command or script run.

beginner

Example: What exit code will this script return?<br>

#!/bin/bash
if [ ! -f myfile.txt ]; then
  exit 2
else
  exit 0
fi

If myfile.txt does not exist, the script exits with code 2. Otherwise, it exits with 0 meaning success.

What does exit 0 usually mean in a bash script?

A The script ran successfully

B The script failed

C The script is still running

D The script has a syntax error

exit 0 means the script finished without errors.

Which exit code range is valid in bash scripts?

A Any positive number

B 1 to 100

C 0 to 1000

D 0 to 255

Bash exit codes must be between 0 and 255.

How do you get the exit code of the last command in bash?

A $!

B $?

C $#

D $$

$? holds the exit code of the last command.

If a script ends with exit 3, what does it mean?

A The script succeeded

B The script is running in background

C The script failed with a specific error

D The script is paused

Exit codes other than 0 usually mean different errors or statuses.

What happens if you use exit 300 in a bash script?

A It exits with code 44 (300 modulo 256)

B It exits with code 300

C It causes an error and script stops immediately

D It exits with code 0

Exit codes wrap around modulo 256, so 300 becomes 44.

Explain how and why you would use custom exit codes in a bash script.

Think about how scripts tell the system if they succeeded or failed.

Describe how to check the exit code of the last command and why it is useful.

This is how you know if a command worked before moving on.