Setting and Using Environment Variables
Introduction
Environment variables are a set of dynamic values that can affect the way running processes will behave on a computer. They are part of the environment in which a process runs. In this tutorial, we will cover how to set and use environment variables using the command line.
Setting Environment Variables
Setting environment variables can differ between operating systems. Below we will see how to set environment variables on Windows, macOS, and Linux.
Windows
On Windows, you can set an environment variable using the set command for the current session or using the System Properties for a permanent setting.
To set an environment variable for the current session:
set VAR_NAME=value
Example:
set PATH=C:\MyProgram\Bin;%PATH%
macOS/Linux
On macOS and Linux, you can set environment variables using the export command.
To set an environment variable:
export VAR_NAME=value
Example:
export PATH=/usr/local/myprogram/bin:$PATH
Using Environment Variables
Once an environment variable is set, you can use it in your scripts and programs.
Accessing Environment Variables
To access environment variables in different operating systems and scripting languages:
Windows Command Prompt
Use the following syntax to access an environment variable:
%VAR_NAME%
macOS/Linux Shell
Use the following syntax to access an environment variable:
$VAR_NAME
Python
Use the os module to access environment variables:
import os
value = os.getenv('VAR_NAME')
Examples
Example 1: Setting and Using an Environment Variable in Windows
Step 1: Set the environment variable
set MY_VAR=HelloWorld
Step 2: Use the environment variable
echo %MY_VAR%
Example 2: Setting and Using an Environment Variable in Linux
Step 1: Set the environment variable
export MY_VAR=HelloWorld
Step 2: Use the environment variable
echo $MY_VAR
Example 3: Using Environment Variables in a Python Script
Step 1: Set the environment variable (example in Linux)
export MY_VAR=HelloWorld
Step 2: Create a Python script to use the environment variable
import os
value = os.getenv('MY_VAR')
print(value)
Conclusion
Environment variables are a crucial aspect of the development and runtime environments. They help in setting up the necessary configurations and paths required by various applications. This tutorial provided an overview of how to set and use them across different operating systems and within scripts. Understanding and using environment variables effectively can significantly improve your workflow and application management.