The Power of Linux Shell Environment Variables

If you’re working in a Linux environment, chances are you’ve encountered environment variables—even if you didn’t realize it at the time. They quietly power much of what goes on behind the scenes in your shell sessions, influencing everything from what shell prompt you see to which programs are available when you type a command. Whether you’re an experienced sysadmin or a new Linux user, mastering environment variables is essential for customizing and controlling your shell experience.

In this guide, we’ll take a dive into environment variables in the Linux shell. By the end, you’ll not only know how to view and set these variables, but also how to persist them, use them in scripts, and troubleshoot issues effectively.

What Are Environment Variables?

At a basic level, environment variables are dynamic named values that affect the behavior of running processes on your Linux system. Think of them as configuration settings that your shell (like Bash or Zsh) and applications refer to in order to understand how they should operate.

For example:

• The PATH variable tells the shell where to look for executable files.

• The HOME variable stores the path to your home directory.

• The LANG variable defines your system’s language and character encoding.

Environment Variables vs Shell Variables

There is an important distinction between shell variables and environment variables:

• Shell variables are local to the shell session in which they are defined.

• Environment variables are shell variables that have been exported, meaning they are inherited by child processes spawned from the shell.

Viewing Environment Variables

Before you can modify or use environment variables, it’s important to know how to inspect them.

View All Environment Variables

printenv

or

env

Both commands list environment variables currently set for the session.

View a Specific Variable

echo $HOME

This will display the current user’s home directory.

View All Shell Variables

set

This command displays all shell variables and functions. It’s broader than printenv.

Setting and Exporting Environment Variables

You can define your own variables or temporarily change existing ones within your shell.