What are common uses?

Common uses of environment variables include:

1. Configuration Settings: Store application-specific settings, such as database connection strings, API keys, or feature flags.

2. System Paths: Define directories for executable files, such as the PATH variable, which specifies where the system looks for executable programs.

3. User Information: Store user-specific data, such as:

   • HOME: The current user's home directory.
   • USER: The name of the current user.

4. Locale Settings: Control language and regional settings, such as LANG or LC_ALL, which affect how programs display text and format data.

5. Temporary Files: Specify directories for temporary files using the TMPDIR variable, which some applications use to store temporary data.

6. Shell Behavior: Customize the behavior of the shell, such as PS1 for the command prompt appearance.

7. Application Modes: Indicate whether an application should run in development, testing, or production mode, often using variables like NODE_ENV for Node.js applications.

These uses help manage system behavior, enhance security, and improve application portability across different environments.