if-then-fi structure in Bash Scripting - Mini Project: Build & Apply

Basic Decision Making with if-then-fi Structure in Bash

📖 Scenario: You are writing a simple bash script to check if a number is positive. This is like checking if the temperature outside is above zero before deciding to wear a jacket.

🎯 Goal: Build a bash script that uses the if-then-fi structure to check if a variable number is greater than zero and print a message accordingly.

📋 What You'll Learn

Create a variable number with the value 5

Create a variable threshold with the value 0

Use an if statement with then and fi to check if number is greater than threshold

Print "Number is positive" if the condition is true

Print "Number is not positive" if the condition is false

💡 Why This Matters

🌍 Real World

Scripts often need to make decisions, like checking if a file exists or if a user input meets certain criteria. The if-then-fi structure is the basic way to do this in bash.

💼 Career

Understanding conditional statements in bash is essential for system administrators, DevOps engineers, and anyone automating tasks on Linux or Unix systems.

1

Create the number variable

Create a variable called number and set it to 5.

Bash Scripting

# Create a variable called number and set it to 5
# Your code here

Need a hint?

Use number=5 without spaces around the equals sign.

2

Create the threshold variable

Create a variable called threshold and set it to 0.

Bash Scripting

number=5
# Create a variable called threshold and set it to 0
# Your code here

Need a hint?

Use threshold=0 without spaces around the equals sign.

3

Write the if-then-fi condition

Write an if statement to check if number is greater than threshold. Use then and fi to mark the block. Inside the if, print "Number is positive". Use else to print "Number is not positive" if the condition is false.

Bash Scripting

number=5
threshold=0
# Write an if-then-fi block to check if number > threshold
# Print "Number is positive" if true, else print "Number is not positive"
# Your code here

Need a hint?

Use if [ "$number" -gt "$threshold" ] to compare numbers. Remember to close the block with fi.

4

Run the script and display the output

Run the script and print the output to show the message based on the if condition.

Bash Scripting

number=5
threshold=0
if [ "$number" -gt "$threshold" ]; then
    echo "Number is positive"
else
    echo "Number is not positive"
fi
# Run the script to display the output
# Your code here

Need a hint?

Just run the script. The output should be Number is positive.