Day 55beginnerMar 27, 2026

Persist Environment Variables the Right Way

Environment variables let you configure applications without hardcoding values — but only if you persist them correctly.

linuxconfigurationfundamentals

What

Environment variables configure application behavior without hardcoding values. They can be set temporarily for a single session using export, or persisted permanently by adding them to shell profile files like ~/.bashrc or ~/.zshrc. Every process inherits the environment of its parent.

Why It Matters

Hardcoding config values like API keys, database URLs, and feature flags into source code is a security risk and deployment nightmare. Environment variables separate configuration from code, making it easy to change settings per environment (dev, staging, prod) without modifying your application.

Example

# Set a variable for the current session only
export API_KEY="abc123"
export DATABASE_URL="postgres://localhost:5432/mydb"

# Persist variables by adding to your shell profile
# For bash:
echo 'export API_KEY="abc123"' >> ~/.bashrc

# For zsh:
echo 'export API_KEY="abc123"' >> ~/.zshrc

# Apply changes without restarting the terminal
source ~/.bashrc    # or: source ~/.zshrc

# List all environment variables
env
printenv

# Check a specific variable
echo $API_KEY
printenv API_KEY

# Unset a variable
unset API_KEY

bash

Common Mistake

Adding variables to ~/.bashrc but forgetting to run 'source ~/.bashrc' afterward, then wondering why the variable isn't available in the current terminal. Changes to profile files only take effect in new shells or after sourcing.

Quick Fix

After editing ~/.bashrc or ~/.zshrc, always run 'source ~/.bashrc' (or 'source ~/.zshrc') in your current terminal. Or simply open a new terminal window — it will automatically load the updated profile.