Debugging with PS4 in Bash Scripting - Mini Project: Build & Apply

Debugging Bash Scripts Using PS4

📖 Scenario: You are writing a bash script to calculate the total price of items bought. Sometimes the script does not work as expected. You want to learn how to debug it easily.

🎯 Goal: Learn how to use the PS4 variable and set -x to debug bash scripts by showing detailed command execution steps.

📋 What You'll Learn

Create a bash script with variables for item prices

Add a PS4 variable to customize debug output

Enable debugging with set -x

Calculate the total price using arithmetic

Print the total price

💡 Why This Matters

🌍 Real World

Debugging bash scripts is essential when automating tasks on servers or your computer. Using PS4 and set -x helps find errors quickly.

💼 Career

Many IT and DevOps jobs require writing and debugging shell scripts. Knowing how to use PS4 for debugging makes troubleshooting faster and easier.

1

Create variables for item prices

Create three variables called price1, price2, and price3 with values 10, 20, and 30 respectively.

Bash Scripting

# Create variables price1, price2, and price3 with values 10, 20, and 30
# Your code here

Need a hint?

Use simple assignment like price1=10 without spaces.

2

Add PS4 variable for debug prefix

Add a variable called PS4 and set it to the string '+ Line: $LINENO: ' to show the line number in debug output.

Bash Scripting

price1=10
price2=20
price3=30
# Set PS4 to '+ Line: $LINENO: '
# Your code here

Need a hint?

Use single quotes around the string and include $LINENO to show the current line number.

3

Enable debugging and calculate total

Add set -x to enable debugging. Then create a variable total that sums price1, price2, and price3 using arithmetic expansion.

Bash Scripting

price1=10
price2=20
price3=30
PS4='+ Line: $LINENO: '
# Enable debugging
# Calculate total as sum of price1, price2, and price3
# Your code here

Need a hint?

Use set -x on its own line. Use $(( )) for arithmetic.

4

Print the total price

Print the value of total using echo.

Bash Scripting

price1=10
price2=20
price3=30
PS4='+ Line: $LINENO: '
set -x
total=$((price1 + price2 + price3))
# Print total
# Your code here

Need a hint?

Use echo $total to display the total.