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Environment Variables: System-Wide Variables

Environment variables are available to all processes. System provides some. You can set your own.

Here's the thing: Environment variables are useful. Learn the common ones. Use them.

Common System Variables​

PATH: Command Search Path​

echo $PATH

My take: PATH is where shell looks for commands. Important.

HOME: User Home​

echo $HOME
cd $HOME

My take: HOME is your home directory. Use it.

USER: Current User​

echo $USER

My take: USER is your username. Use it for personalization.

PWD: Current Directory​

echo $PWD

My take: PWD is current directory. Use it.

Setting Environment Variables​

Export​

export MY_VAR="value"

My take: export makes variables available to child processes.

In Script​

#!/bin/bash
export API_KEY="secret"

My take: Export in scripts. Make variables available.

Common Patterns​

Use HOME​

config_file="$HOME/.config/myapp.conf"

Use USER​

log_file="/var/log/${USER}_app.log"

What's Next?​

Now that you understand environment variables, let's talk about Variable Scope.

Personal note: Environment variables seemed mysterious at first. Then I learned the common ones. Now I use them constantly. They're everywhere. Learn them.