environment-variables

Environment Variables

Environment variables are dynamic values that affect the behavior of running processes on a computer. They are part of the environment in which a process runs, and they are used by the operating system to configure software, control the behavior of applications, and set up the environment for user sessions.

History and Development

The concept of environment variables dates back to the early days of computing. They were introduced as a way to manage configurations in Unix-like operating systems. The earliest Unix systems from the 1970s used them to pass settings to programs, allowing for more flexible and dynamic system behavior without hardcoding settings into the applications themselves. Over time:

In POSIX systems, environment variables became standardized, allowing for cross-platform compatibility.
Microsoft adopted a similar concept with the Windows environment variables, though with different syntax and conventions.
With the advent of cloud computing and containerization technologies like Docker, environment variables have become crucial for configuration management in distributed systems.

Usage and Functionality

Environment variables serve several key functions:

Configuration Management: They allow for setting parameters like paths, ports, or connection strings without altering the source code.
User and Session Management: Variables like HOME or USER help tailor the user experience and system behavior.
Security: Sensitive information like API keys or passwords can be stored in environment variables, reducing the risk of exposing these in source code.
Scripting and Automation: They enable scripts to adapt to different environments without modification.
Environment Isolation: In containerized applications, environment variables are used to configure containers at runtime, ensuring isolation and consistency across different deployments.

Common Environment Variables

Some commonly used environment variables include:

PATH - Directories to search for executable files.
HOME - The home directory for the user.
USER - The current logged-in user's username.
LD_LIBRARY_PATH (on Unix-like systems) - Specifies directories to search for shared libraries.

Setting and Accessing Environment Variables

Environment variables can be set and accessed differently depending on the operating system:

Unix/Linux: Use the export command or set in some shells to set variables, and echo $VARIABLE_NAME to access them.
Windows: Use set or setx for temporary or permanent settings, respectively. Accessing is done with %VARIABLE_NAME%.
Programmatically: Languages like Python, Java, and others provide methods to access environment variables, e.g., os.environ in Python.

Sources:

Grok-Pedia