RuntimeEnv.md

Runtime Arguments vs. Environment Variables

Runtime Arguments:

• Definition: These are parameters passed to a program at the time it is executed. They are typically specified in the command line.
• Usage:
  • Directly affect the program's behavior for a specific run.
  • Ideal for options or configurations that might change frequently.
  • Example: If you have a script that processes files, you might pass the filename as a runtime argument (python process_file.py input.txt).

Environment Variables:

• Definition: These are key-value pairs set in the operating system environment. They are accessible by programs running within that environment.
• Usage:
  • Store configuration settings that are more static and applicable across multiple runs or even different programs.
  • Ideal for sensitive data like API keys, database connection strings, or settings that are less likely to change frequently.
  • Example: Setting an environment variable for a database URL (export DATABASE_URL='postgres://user:pass@localhost/dbname').

When to Use Which?

Use Runtime Arguments When:

• The configuration or input is likely to change frequently or varies from one execution to another.
• You need to provide different inputs or options for each run of the program.
• Example: Specifying a different input file each time you run a data processing script.

Use Environment Variables When:

• The configuration is relatively static and does not change often.
• You are dealing with sensitive information that you don't want to hard-code into your scripts.
• The same configuration is used across multiple runs or by multiple programs.
• Example: Storing database credentials or API keys that are used by multiple parts of your application.

Example Scenarios

1. Runtime Arguments:

   • A script that converts images to a different format:

     python convert_image.py input.jpg output.png

   • You might run this script multiple times with different input and output filenames.

2. Environment Variables:

   • A web application that needs to connect to a database:

     import os
     database_url = os.getenv('DATABASE_URL')

   • The DATABASE_URL might be set once and used by the application each time it runs, ensuring that the database credentials are not hard-coded.

Best Practices

• Security: Use environment variables for sensitive information to avoid exposing them in code or command line history.
• Flexibility: Use runtime arguments for values that change often to keep your programs flexible and reusable.
• Documentation: Clearly document the expected runtime arguments and required environment variables in your project's README or other documentation.

By understanding these differences and knowing when to use each, you can write more flexible, secure, and maintainable code.