The past two posts, “How To Read Environment Variables In C# & .NET” and “How To Read Environment Variables In PowerShell”, have looked at how to read environment variables.

It is important to point out that environment variables are, in fact, scoped to three levels:

  1. Global (machine) level - accessible to all users and all processes running on the machine.
  2. User level - accessible by all processes initiated by the current user
  3. Process level - accessible only within the current process.

This is important to understand when setting and reading environment variables.

A machine-level environment variable is the same for all users on the machine, and, in fact, requires administrative rights to set and modify. These are useful for things like the PATH.

User-level environment variables are local to the current user, meaning any processes launched by the user can access them. These are useful for things like API keys.

Process-level environment variables are local to the current process and are destroyed once the process terminates.

When designing your applications and needing a way to share data between users or processes, these considerations should be taken into account.

TLDR

Environment variables are scoped per machine, user, and process.

Happy hacking!