Windows – Why is the PATH environment variable different from the command prompt

command lineenvironment-variablespowershellwindows 7

A bit of important background: my company has a generic login VBS script that makes modifications to the user PATH environment variable upon login and allows me to run software that has dependencies on mapped DFS fileshares. I also recently installed the Windows Powershell SDK to my Windows 7 Enterprise machine and attempted to try out modifying my PATH environment variable from the Powershell command line.

Following this, I noticed that I could no longer run applications that correspond to these login PATH modifications and that the environment variable editor PATH was set to something different than what was showing up when I issued an 'echo %PATH%' from the command prompt.

So for example (simplification), from the environment variable editor (My Computer properties -> Advanced System Settings -> Environment Variables) I had 

 C:\MyDir\; C:\MyOtherDir

whereas when I did 'echo %PATH%' from a command prompt I got:

 C:\MyDir\

Has anyone else had a similar issue and was there some sort of resolution? When I googled for help, I came upon this:

(Related?) StackOverflow Thread

It occurred to me that if the login script was initiated by something other than my Explorer.exe environment, then that was the problem. However, when I ran the login script myself, my PATH from command prompt was unchanged. What would this have to do with PowerShell? I'm missing how this is connected to that install completely.

Best Answer

Windows has two classes of environment variables system environment variables and user environment variables. If you are using echo %PATH% you will see your user environment variable PATH. Only if there is no user variable defined, the system variable will be in effect for user processes.

The PATH separator ; should not be followed by a blank.

The following Microsoft note might be helpful:

You can modify user environment variables by editing the following Registry key:

   HKEY_CURRENT_USER \ 
         Environment

You can modify system environment variables by editing the following Registry key:

   HKEY_LOCAL_MACHINE \ 
               SYSTEM \ 
    CurrentControlSet \ 
              Control \ 
      Session Manager \ 
          Environment

Note that any environment variable that needs to be expanded (for example, when you use %SYSTEM%) must be stored in the registry as a REG_EXPAND_SZ registry value. Any values of type REG_SZ will not be expanded when read from the registry.

Additional remark: Whenever a process changes its environment (rather than the registry settings which define the environment for new processes), the changes are only visible for child processes.

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