Read-only variables (readonly) in Bash Scripting - Mini Project: Build & Apply

Using Read-only Variables in Bash Scripts

📖 Scenario: You are writing a bash script to manage a simple configuration where some values must not change after being set. This is common in scripts that rely on fixed settings like file paths or version numbers.

🎯 Goal: Learn how to create read-only variables in bash so that their values cannot be changed later in the script.

📋 What You'll Learn

Create a variable with a fixed value

Make the variable read-only using the readonly command

Try to change the read-only variable (to see it fail)

Print the value of the read-only variable

💡 Why This Matters

🌍 Real World

Many bash scripts use read-only variables to protect important settings from accidental changes during execution.

💼 Career

Understanding read-only variables helps you write safer and more reliable automation scripts in system administration and DevOps roles.

1

Create a variable with a fixed value

Create a variable called config_path and set it to the string /etc/myapp/config.

Bash Scripting

# Create the variable 'config_path' with the value '/etc/myapp/config'
# Your code here

Need a hint?

Use = to assign the value without spaces, and wrap the path in double quotes.

2

Make the variable read-only

Use the readonly command to make the variable config_path read-only.

Bash Scripting

config_path="/etc/myapp/config"
# Make 'config_path' read-only
# Your code here

Need a hint?

Type readonly followed by the variable name.

3

Try to change the read-only variable

Try to assign the string /tmp/config to the variable config_path after it is made read-only.

Bash Scripting

config_path="/etc/myapp/config"
readonly config_path
# Try to change 'config_path' to '/tmp/config'
# Your code here

Need a hint?

Just write the assignment line again after readonly.

4

Print the value of the read-only variable

Print the value of config_path using echo.

Bash Scripting

config_path="/etc/myapp/config"
readonly config_path
config_path="/tmp/config"
# Print the value of 'config_path'
# Your code here

Need a hint?

Use echo "$config_path" to print the variable's value.