If you're new to Linux shell scripting, understanding how to use variables in Bash is one of the first and most essential skills to master. Bash (Bourne Again Shell) is a widely-used shell and scripting language for automating tasks in Unix-like systems. Learning how to use variables can make your scripts more powerful, flexible, and readable. This guide simplifies the concept and provides you with the basic tools to start scripting effectively.

What Are Bash Variables?

A variable in Bash is essentially a container to hold data — such as text strings, numbers, or command results — that your script can use and manipulate. Think of them as placeholders that can be referenced later in your script.

Declaring and Using Variables

Declaring a variable in Bash is simple:

name="LinuxUser"



There should be no spaces around the = symbol. To access the value of the variable, prefix it with a $:

echo "Hello, $name!"



This will output: Hello, LinuxUser!

Variables are case-sensitive and typically written in lowercase or uppercase based on convention. For example, environment variables like PATH are usually in uppercase.

Types of Variables

There are two main types of variables in Bash:

Local/User-defined variables – Created by you during script execution.





Environment variables – Predefined by the system, available globally across sessions and scripts.





You can export user-defined variables to become environment variables using:

export name



Using Command Substitution

Command substitution allows you to store the output of a command in a variable:

current_time=$(date)

echo "The current time is $current_time"



This assigns the current date and time to the current_time variable.

Quoting and Best Practices

Use quotes when assigning or referencing variables that contain spaces:

greeting="Hello, World"

echo "$greeting"



Avoid using unnecessary spaces around the equal sign, and quote your variables when used within strings to prevent word splitting or unexpected behavior.

Readonly and Unset Variables

If you want a variable to be immutable:

readonly version="1.0"



To remove a variable:

unset name



Learn More with Real Examples

For a detailed walkthrough with real-world examples, refer to this excellent resource: How to Use Variables in Bash. It covers everything from simple declarations to advanced usage like arrays, arithmetic operations, and variable scope.

Whether you're writing automation scripts, managing system tasks, or learning Linux for development purposes, mastering Bash variables is a foundational skill. As you grow more confident, you can explore more advanced scripting concepts built upon this simple but powerful feature.