GetEnvironmentVariable
Get the current value of a User- or Machine- scoped environment variable.
GetEnvironmentVariable is a command-line utility -- a .NET Console App -- that returns the current value of a User- (or even Machine-) scoped environment variable.
Since it is not possible to pass a Process-scoped environment variable back up to the parent / calling process (at least not without a lot of work), that leaves very few options when wanting to pass back a value from a program without creating a file.
User environment variables and Machine environment variables can, however, be passed back to the parent / calling process because they are saved in the Registry. The problem with using either of these is that only new processes are aware of the new values, but the parent / calling process does not reload environment variables, so changes in these two scopes are not immediately known.
It is possible to use REG QUERY to get the current value, but it is not easily usable due to all of the extra formatting around the value that is returned:
C:\>REG QUERY HKCU\Environment /v _MyTest
HKEY_CURRENT_USER\Environment
_MyTest REG_SZ bob
It is much easier to simply do:
C:\>GetEnvironmentVariable.exe -name _MyTest
bob
The reduced output makes it very easy to get the User or Machine environment variable into a local variable in a CMD script (i.e. batch file) using the FOR command:
Outside of a script:
C:\>FOR /F %A IN ('GetEnvironmentVariable.exe -name _MyTest') DO @SET _TempVariable=%A
C:\>echo %_TempVariable%
bob
Inside of a script:
Contents of TestGetVariable.cmd:
@ECHO OFF
FOR /F %%A IN ('GetEnvironmentVariable.exe -name _MyTest') DO SET _TempScriptVariable=%%A
ECHO Found: %_TempScriptVariable%
Running TestGetVariable.cmd:
C:\>TestGetVariable.cmd
Found: bob