Linux By Karthick Dkk

Debug Bash Script

Bash script step-by-step execution

Photo by RoonZ nl on Unsplash

Hey Mate! Welcome to another blog post!

If you want to see the step-by-step execution of a bash script to understand what it’s doing or to debug it, you can use the -x option when running the script or include it within the script itself. This will display each command as it gets executed, along with any variables that are expanded.

Option 1: Run Script with Debugging (-x)

When you execute the script, add -x to the command:

bash -x script.sh

This will show each command, along with its expanded arguments, as it’s executed.

Option 2: Add Debugging Inside the Script

Add the following line at the top of your bash script to enable debugging for the whole script:

#!/bin/bash
set -x

If you only want debugging for specific parts of the script, you can turn it on and off as needed:

#!/bin/bash
echo "This part runs without debugging"

set -x  # Turn on debugging
echo "Debugging starts here"

ls -l

set +x  # Turn off debugging
echo "Debugging stopped"

Linux Commands for DevOps & Sysadmins

Example Script

Here’s an example script with step-by-step debugging enabled:

#!/bin/bash
set -x

echo "Step 1: Updating the package list"
sudo apt update
echo "Step 2: Installing Nginx"
sudo apt install -y nginx
echo "Step 3: Starting Nginx service"
sudo systemctl start nginx

set +x

echo "Script execution completed"

When you run this script, every command between set -x and set +x will be displayed with its expanded arguments.

Why Use Step-by-Step Execution?

1. Debugging: Identify issues or incorrect variable values.
2. Understanding: Learn exactly how your script…