Environment Basics

Bash · Reference cheat sheet

📋 Overview

The environment is a set of key/value variables available to your shell and the programs it starts. Common ones: PATH, HOME, USER, PWD. Scripts often read VAR=value settings for configuration.

🔧 Core concepts

Shell variables and environment variables are related; export promotes a shell variable into the environment.

💡 Examples

Inspect common variables:

echo "$HOME"
echo "$USER"
echo "$PWD"
echo "$PATH"

Set for one command:

LANG=C date
MESSAGE="hi" bash -c 'echo "$MESSAGE"'

Export for the current session:

export APP_ENV=development
echo "$APP_ENV"
env | grep APP_ENV

Add a directory to PATH (session only):

export PATH="$HOME/bin:$PATH"
which python || true

⚠️ Pitfalls

• Always quote expansions: "$VAR" — unquoted values with spaces break.
• export FOO = bar is wrong (spaces around =).
• Changing PATH incorrectly can make every command “not found.”
• Putting secrets in world-readable scripts or committing .env is unsafe.

🔗 Related

• getting_started.md
• navigation.md
• variables.md
• permissions_basics.md