`Environment.GetEnvironmentVariable` on Unix: Clarify that it only sees environment-variable modifications made by *managed* callers, not also by native libraries

[mklement0]

Describe the issue or suggestion

Of technical necessity, on Unix-like platforms (but not on Windows), .NET maintains a private copy of the process environment block that is only seen by and can only be modified by managed callers, namely via Environment.SetEnvironmentVariable (for background information, see https://github.com/dotnet/runtime/issues/9529), which has two ramifications for P/Invoke calls to native libraries:

• Native libraries do NOT see in-process environment changes performed via Environment.SetEnvironmentVariable.

  • This already is documented, namely in System.Environment.SetEnvironmentVariable:

    • On non-Windows systems, calls to the SetEnvironmentVariable(String, String) method have no effect on any native libraries that are, or will be, loaded.

• Conversely, in-process environment modifications made by native libraries are not seen by managed callers.

  • This is currently not documented, and should be mentioned in the following topics:
    • The System.Environment.GetEnvironmentVariable method
    • The System.Environment.GetEnvironmentVariable methods fundamentals article.

---

Document Details

⚠ Do not edit this section. It is required for learn.microsoft.com ➟ GitHub issue linking.

• ID: 4803cbbd-7955-7443-fced-8461ee23d685
• Version Independent ID: 4734e5db-f0d4-6fa2-75cb-d0836fb12f36
• Content: System.Environment.GetEnvironmentVariable methods - .NET
• Content Source: docs/fundamentals/runtime-libraries/system-environment-getenvironmentvariable.md
• Service: dotnet-fundamentals
• GitHub Login: @gewarren
• Microsoft Alias: dotnetcontent