Custom exit codes (exit N) in Bash Scripting

Introduction

Custom exit codes help your script tell other programs or users what happened when it finished.

You want to show if a script worked or failed in a specific way.

You need to stop a script early and explain why.

You want other scripts to react differently based on your script's result.

Syntax

Bash Scripting

exit N

Replace N with a number from 0 to 255.

0 means success; any other number means an error or special condition.

Examples

Ends the script and says everything worked fine.

Bash Scripting

exit 0

Ends the script and signals a general error.

Bash Scripting

exit 1

Ends the script with a custom code 42 to show a specific error.

Bash Scripting

exit 42

Sample Program

This script checks if a file given as the first argument exists. It exits with 0 if yes, or 2 if no.

Bash Scripting

#!/bin/bash

# Check if a file exists
if [ -f "$1" ]; then
  echo "File exists."
  exit 0
else
  echo "File does not exist."
  exit 2
fi

Important Notes

Exit codes are numbers between 0 and 255 because the system uses 8 bits to store them.

Use different exit codes to help other scripts understand what happened.

Always use exit 0 for success to follow common practice.

Summary

Use 'exit N' to stop a script and send a number as the result.

0 means success; other numbers mean different errors or states.

Custom exit codes help scripts communicate clearly with each other.