How can an environment variable be set in an operating system?

Environment variables in operating systems are set differently:

• In Linux/macOS (bash):

  • Temporary variable for the current session:

    export VARIABLE_NAME=value
    

  • To make the variable available in all new sessions, add it to configuration files such as ~/.bashrc or ~/.profile.

• In Windows (cmd):

  • Temporary variable for the current session:

    set VARIABLE_NAME=value
    

  • To set a variable permanently via the interface: "Control Panel" → "System" → "Advanced system settings" → "Environment Variables".
  • Using PowerShell:

    $Env:VARIABLE_NAME = "value"
    

Thus, environment variables can be set temporarily for the current session or permanently through configuration files or system settings.