PATH environment variable containing other environment variables

Question

I know that I can query any environment variable by calling:

System.Environment.GetEnvironmentVariable();

Now for example, I want the value of windir, that is %SystemRoot%. However, the function interpretes it as C:\Windows (which is the value of SystemRoot).

I get the same behaviour by querying the registry key with Registry.LocalMachine.OpenSubKey()

Is there a way to get variable names from an environment variable instead of their paths? (I need it in order to easily switch between multiple installed versions of a SDK I work with.)

PATH tends to be a very messy affair with a mix of string literals and environment %variable% names. You'd have to first retrieve the value without getting the %variables% expanded. But if you get a string literal then you cannot know that there might be a variable name for it. — Hans Passant
– Hans Passant, Commented Dec 14, 2018 at 14:49

M-Peror · Accepted Answer · 2018-12-14 12:49:30Z

As far as I know, the only way to do that, is to read the environment variable directly from the registry and specify that you do not want it expanded:

registryKey.GetValue("PATH", "", RegistryValueOptions.DoNotExpandEnvironmentNames);

See the docs for RegistryValueOptions.

rory.ap · Accepted Answer · 2018-12-14 12:35:15Z

The fact that %WINDIR% and %SYSTEMROOT% have the same value is a mere coincidence. It's obvious why they would be, but they are still independent variables. Changing one would not result in the other being changed.

You would have to write something manually that sought out other environmental variables with the same value and substituted whatever replacement variable you had in mind, e.g. %SYSTEMROOT%.

Collectives™ on Stack Overflow

PATH environment variable containing other environment variables

2 Answers 2

1 Comment

Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Linked

Related