DevOps Bootcamp · Lesson

Conditional Statements (if, else, elif)

Implement decision-making logic in your scripts using 'if', 'else', and 'elif' statements for dynamic behavior.

Conditional Statements (if, else, elif) is a free DevOps Bootcamp lesson on CoddyKit — lesson 3 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the DevOps Bootcamp learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

Why Conditionals Matter

In Bash scripting, sometimes you need your script to make decisions. Imagine a script that performs different actions based on user input or a file's existence.

This is where conditional statements come in! They allow your script to execute specific blocks of code only if certain conditions are met.

The Basic 'if' Statement

The simplest conditional is the if statement. It checks a condition, and if it's true, a block of commands is executed.

The syntax is:

if [ condition ]
then
# commands if condition is true
fi (marks the end of the if block)

Your First 'if' Script

Let's see a basic if statement in action. This script checks if a number is greater than 5.

Try changing the NUMBER value and running it!

#!/bin/bash

NUMBER=10

if [ $NUMBER -gt 5 ]
then
  echo "The number $NUMBER is greater than 5."
fi

echo "Script finished."

Crafting Test Conditions

The [ condition ] part is crucial. It's actually a command called test or its alias [.

You can also use [[ condition ]], which is a more advanced version providing better syntax and preventing word splitting issues. For beginners, [ ] is common.

Always put spaces around the brackets and operators.
Variables inside [ ] should usually be quoted (e.g., "$VARIABLE") to prevent errors with empty or multi-word values.

Comparing Numbers

When comparing numbers in Bash, you use specific operators:

-eq: Equal to
-ne: Not equal to
-gt: Greater than
-ge: Greater than or equal to
-lt: Less than
-le: Less than or equal to

These are used inside [ ] or [[ ]].

Comparing Strings

For comparing text (strings), different operators are used:

== or =: Equal to (== is preferred in [[ ]])
!=: Not equal to
-z "$STRING": True if string is empty (zero length)
-n "$STRING": True if string is not empty (non-zero length)

Remember to quote your string variables!

The 'if-else' Statement

What if you want to run one block of code if a condition is true, AND a different block if it's false?

That's what if-else is for! It provides an alternative path for your script.

The syntax is:

if [ condition ]
then
# commands if true
else
# commands if false
fi

'if-else' in Action

This script asks you for a number and tells you if it's positive or not. It uses an if-else structure.

Run it a few times with different inputs (e.g., 5, -3, 0).

#!/bin/bash

read -p "Enter a number: " NUM

if [ "$NUM" -gt 0 ]
then
  echo "$NUM is a positive number."
else
  echo "$NUM is not a positive number (it's zero or negative)."
fi

Multiple Choices with 'elif'

When you have more than two possible outcomes, you can use elif (short for "else if"). This allows you to check multiple conditions in sequence.

The syntax is:

if [ condition1 ]
then
# commands if condition1 is true
elif [ condition2 ]
then
# commands if condition1 is false AND condition2 is true
else
# commands if all conditions are false
fi

Advanced Decision Logic

Let's create a script that categorizes a user's age using if, elif, and else. This handles multiple scenarios.

Notice the use of && for combining conditions in [[ ]] (logical AND).

#!/bin/bash

read -p "Enter your age: " AGE

if [[ $AGE -lt 13 ]]
then
  echo "You are a child."
elif [[ $AGE -ge 13 && $AGE -lt 18 ]]
then
  echo "You are a teenager."
elif [[ $AGE -ge 18 && $AGE -lt 65 ]]
then
  echo "You are an adult."
else
  echo "You are a senior citizen."
fi

Conditional Check

Consider the following Bash script:

#!/bin/bash

SCORE=85

if [ $SCORE -lt 60 ]
then
  echo "Fail"
elif [ $SCORE -lt 80 ]
then
  echo "Pass"
else
  echo "Distinction"
fi

Conditionals Summary

Great job! You've learned how to make your Bash scripts smarter with conditional statements.

The if statement executes code if a condition is true.
else provides an alternative path if the if condition is false.
elif allows you to check multiple conditions in a sequence.
Remember to use appropriate operators (-eq for numbers, == for strings) and always close your if blocks with fi.

These tools are fundamental for creating dynamic and interactive scripts!

Frequently asked questions

Is the “Conditional Statements (if, else, elif)” lesson free?

Yes — the full text of “Conditional Statements (if, else, elif)” is free to read here on the web, and the DevOps Bootcamp course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the DevOps Bootcamp course, upgrade to CoddyKit PRO.

What will I learn in “Conditional Statements (if, else, elif)”?

Implement decision-making logic in your scripts using 'if', 'else', and 'elif' statements for dynamic behavior. You practise DevOps Bootcamp with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start DevOps Bootcamp?

No prior experience is required. DevOps Bootcamp on CoddyKit is structured for beginners through advanced learners; this is — lesson 3 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Conditional Statements (if, else, elif)” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this DevOps Bootcamp lesson?

Yes. Every DevOps Bootcamp lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

← Back to DevOps Bootcamp