Environment Variables

By the end of this lesson you'll understand how the shell stores values, the difference between a shell variable and an environment variable, how PATH lets you run commands by name, and how to make your settings persist across every terminal session.

Learn Environment Variables in our free Command Line course — an interactive lesson with worked examples, a practice exercise and a quick reference.

Part of the free Cli course at LearnCodingFast — hands-on lessons with examples you run in your browser, plus practice exercises and a quick quiz.

1. Shell Variables vs Environment Variables

A plain assignment name=value creates a shell variable that only the current shell can see. To let a program you launch — a child process — inherit it, you must export it into the environment . That single distinction explains most "why can't my program see my variable?" confusion.

2. Reading and Inspecting Variables

Expand a value with $VAR or {'$ VAR '} — use the braces when the name touches other text. To list the whole environment use env (or printenv with no argument); to read one variable use printenv NAME . Note that printenv only sees exported variables, while echo $VAR expands any shell variable.

3. PATH: How the Shell Finds Commands

PATH is a colon-separated list of directories. When you type ls , the shell walks PATH left to right and runs the first ls it finds. To add your own folder, prepend it and keep the old value on the end with :$PATH — overwriting PATH entirely is how people accidentally make every command "not found".

4. The Exit Status: $?

The special variable $? holds the exit status of the command that just finished. By convention 0 means success and any non-zero value means a failure. Scripts lean on this constantly — it's how if decides whether the previous command worked.

5. Removing Variables with unset

When you no longer need a variable — especially a secret like an API token — remove it with unset . After unsetting, expanding the name gives an empty string because the variable simply no longer exists.

6. Persisting Variables Across Sessions

Anything you set in a shell vanishes when that shell closes. To load a variable every session, add the export line to a startup file. The right file depends on your shell and session type: ~/.bashrc for interactive non-login bash, ~/.bash_profile for login bash, and ~/.zshrc for zsh (the default on modern macOS). Use source to apply changes without opening a new terminal.

Fill in the one blank marked ___ using the # 👉 hint so the child bash can see the variable, then run it and check the Output panel matches.

Add a new folder to the front of PATH while keeping everything that was already there. Fill in the blank, then run it.

No blanks this time — just a brief and an outline. Combine export, $?, PATH inspection, and unset into a few commands that demonstrate everything from this lesson, and check your output against the hints in the comments.

Practice quiz

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