Default values (${var:-default}) in Bash Scripting - Mini Project: Build & Apply

Using Default Values in Bash Scripts with ${var:-default}

📖 Scenario: You are writing a simple bash script to greet users. Sometimes, the user might not provide their name. You want to make sure the script still works by using a default name when none is given.

🎯 Goal: Build a bash script that uses the ${var:-default} syntax to provide a default value for a variable if it is empty or unset.

📋 What You'll Learn

Create a variable called username with no value initially.

Create a variable called default_name with the value Guest.

Use the ${var:-default} syntax to assign a greeting name that uses username if set, or default_name if not.

Print the greeting message using the chosen name.

💡 Why This Matters

🌍 Real World

Scripts often need to handle missing inputs or environment variables. Using default values keeps scripts robust and user-friendly.

💼 Career

Knowing how to use default values in bash is essential for system administrators, DevOps engineers, and anyone automating tasks on Linux or Unix systems.

1

Set up the username variable with no value

Create a variable called username and set it to an empty string.

Bash Scripting

# Create the variable username with no value
# Your code here

Need a hint?

Use username="" to create an empty string variable.

2

Create a default_name variable with value Guest

Create a variable called default_name and set it to the string Guest.

Bash Scripting

username=""
# Create the variable default_name with value Guest
# Your code here

Need a hint?

Use default_name="Guest" to assign the default name.

3

Use ${var:-default} to choose the greeting name

Create a variable called greeting_name that uses ${username:-$default_name} to get username if set, or default_name if username is empty or unset.

Bash Scripting

username=""
default_name="Guest"
# Create greeting_name using ${username:-$default_name}
# Your code here

Need a hint?

Use greeting_name=${username:-$default_name} to assign the value.

4

Print the greeting message with the chosen name

Print the message Hello, <name>! where <name> is the value of greeting_name. Use echo and double quotes.

Bash Scripting

username=""
default_name="Guest"
greeting_name=${username:-$default_name}
# Print the greeting message
# Your code here

Need a hint?

Use echo "Hello, $greeting_name!" to print the greeting.