View Exported Environment Variables

The concept of environment variables is central to operating systems and scripting environments. They allow you to pass configuration parameters to processes, control runtime behavior, and share critical information such as paths, credentials, and flags. When variables are exported, they become available to child processes, enabling consistency and modularization across applications.

1. What Are Environment Variables

Environment variables are key-value pairs maintained by the shell (or OS) that affect the behavior of running processes. Examples include:

• PATH: directories in which executables are searched.
• HOME: the current user’s home directory.
• LANG: locale and language preferences.

1.1 Exported vs. Local Variables

In shells like Bash or Zsh, you can define variables without exporting them:

To make MY_VAR available to child processes:

2. Methods to View Exported Variables

Unix-like systems offer several commands to display exported environment variables:

2.1 Example Usage

3. Platform Differences

3.1 Linux and macOS

• env, printenv, export -p are ubiquitous.
• Shell startup files: .bashrc, .bash_profile, .zshrc.

3.2 Windows

• Use set in Command Prompt or Get-ChildItem Env: in PowerShell.
• System environment variables can be configured via the Control Panel or setx command.

4. Practical Scenarios

• Automated Scripts: Passing credentials without hard-coding.
• Continuous Integration: Injecting build-time variables (e.g., CI_TOKEN).
• Containerization: Docker uses ENV directives to set exported variables.
• VPN Clients: Tools like OpenVPN and WireGuard often rely on environment variables (e.g., OPENVPN_CONFIG) for automated deployments.

5. Security and Best Practices

1. Least Privilege: Avoid exporting sensitive data unless necessary.
2. Secure Storage: Use vaults or secure stores limit visibility in ps listings.
3. Validation: Sanitize external inputs before exporting to prevent injection.
4. Rotation: Periodically rotate secrets and regenerate tokens.

6. Troubleshooting Tips

• If a child process doesn’t see your variable, ensure you export it in the correct shell scope.
• Use echo VARIABLE and env grep VARIABLE to confirm its presence.
• Check startup files and non-interactive shells (cron, systemd) which may not source your usual configs.

7. Further Reading

• Bash Reference Manual
• env(1) Manual Page
• Dockerfile ENV Documentation

Understanding and effectively managing exported environment variables is critical for secure, maintainable, and scalable systems. Whether you’re developing local scripts, deploying containers, or configuring VPN clients like OpenVPN in CI/CD pipelines, mastering this aspect will enhance your operational efficiency.