Signal handling with trap in Bash Scripting - Mini Project: Build & Apply

Signal handling with trap

📖 Scenario: You are writing a simple bash script that runs a loop and waits for user interruption. You want to handle the interrupt signal gracefully to clean up before exiting.

🎯 Goal: Build a bash script that uses trap to catch the SIGINT signal (Ctrl+C) and print a friendly message before exiting.

📋 What You'll Learn

Create a variable called count and set it to 0

Create a trap command to catch SIGINT and run a function called handle_interrupt

Define a function called handle_interrupt that prints "Interrupt caught! Exiting..." and exits the script

Create a while loop that increments count every second and prints the current count

Print the final message when the script is interrupted

💡 Why This Matters

🌍 Real World

Signal handling is important in scripts that run continuously or wait for user input. It helps to clean up resources or save state before the script stops.

💼 Career

Many system administration and automation tasks require writing scripts that handle signals to avoid abrupt termination and data loss.

1

Create a counter variable

Create a variable called count and set it to 0.

Bash Scripting

# Create a variable called count and set it to 0
# Your code here

Need a hint?

Use count=0 to create the variable.

2

Set up the trap for SIGINT

Create a trap command to catch the SIGINT signal and run a function called handle_interrupt.

Bash Scripting

count=0
# Create a trap for SIGINT to call handle_interrupt
# Your code here

Need a hint?

Use trap handle_interrupt SIGINT to catch Ctrl+C.

3

Define the interrupt handler function

Define a function called handle_interrupt that prints "Interrupt caught! Exiting..." and exits the script.

Bash Scripting

count=0
trap handle_interrupt SIGINT

# Define the handle_interrupt function
# Your code here

Need a hint?

Define the function with handle_interrupt() { ... } and use echo and exit 0.

4

Create the counting loop and print output

Create a while loop that increments count every second and prints the current count using echo. The script should run until interrupted. The output should show the count numbers starting from 1.

Bash Scripting

count=0
trap handle_interrupt SIGINT

handle_interrupt() {
    echo "Interrupt caught! Exiting..."
    exit 0
}

# Create a while loop to increment count and print it every second
# Your code here

Need a hint?

Use while true; do ... done, increment count with count=$((count + 1)), print with echo, and pause with sleep 1.