Btukfyl

I have a Windows batch file whose purpose is to set some environment variables, e.g.

=== MyFile.cmd ===

SET MyEnvVariable=MyValue

Users can run this prior to doing work that needs the environment variable, e.g.:

C:> MyFile.cmd

C:> echo "%MyEnvVariable%"    <-- outputs "MyValue"

C:> ... do work that needs the environment variable

This is roughly equivalent to the "Developer command prompt" shortcuts installed by Visual Studio, which set environment variables needed to run VS utilities.

However if a user happens to have a Powershell prompt open, the environment variable is of course not propagated back to Powershell:

PS C:> MyFile.cmd

PS C:> Write-Output "${env:MyEnvVariable}"  # Outputs an empty string

This can be confusing for users who switch between CMD and PowerShell.

Is there a way I can detect in my batch file MyFile.cmd that it was called from PowerShell, so that I can, for example, display a warning to the user? This needs to be done without any 3rd party utility.

Your own answer is robust and while it is generally slow due to needing to run a PowerShell process, it can be made significantly faster by optimizing the PowerShell command used to determine the calling shell:

@echo off

setlocal

CALL :GETPARENT PARENT

IF /I "%PARENT%" == "powershell" GOTO :ISPOWERSHELL

IF /I "%PARENT%" == "pwsh" GOTO :ISPOWERSHELL

endlocal



echo Not running from Powershell 

SET MyEnvVariable=MyValue



GOTO :EOF



:GETPARENT

SET "PSCMD=$ppid=$pid;while($i++ -lt 3 -and ($ppid=(Get-CimInstance Win32_Process -Filter ('ProcessID='+$ppid)).ParentProcessId)) {}; (Get-Process -EA Ignore -ID $ppid).Name"



for /f "tokens=*" %%i in ('powershell -noprofile -command "%PSCMD%"') do SET %1=%%i



GOTO :EOF



:ISPOWERSHELL

echo. >&2

echo ERROR: This batch file may not be run from a PowerShell prompt >&2

echo. >&2

exit /b 1

On my machine, this runs about 3 - 4 times faster (YMMV) - but still takes almost 1 second.

Note that I've added a check for process name pwsh as well, so as to make the solution work with PowerShell Core too.

Much faster alternative - though less robust:

The solution below relies on the following assumption, which is true in a default installation:

Only a system environment variable named PSModulePath is persistently defined in the registry (not also a user-specific one).

The solution relies on detecting the presence of a user-specific path in PSModulePath, which PowerShell automatically adds when it starts.

@echo off

echo %PSModulePath% | findstr %USERPROFILE% >NUL

IF %ERRORLEVEL% EQU 0 goto :ISPOWERSHELL



echo Not running from Powershell 

SET MyEnvVariable=MyValue



GOTO :EOF



:ISPOWERSHELL

echo. >&2

echo ERROR: This batch file may not be run from a PowerShell prompt >&2

echo. >&2

exit /b 1

Alternative approach for launching a new cmd.exe console window on demand:

Building on the previous approach, the following variant simply re-invokes the batch file in a new cmd.exe window on detecting that it is being run from PowerShell.

This is not only more convenient for the user, it also mitigates the problem of the solutions above yielding false positives: When run from an interactive cmd.exe session that was launched from PowerShell, the above solutions will refuse to run, even though they should, as PetSerAl points out.

While the solution below also doesn't detect this case per se, it still opens a useable - albeit new - window with the environment variables set.

@echo off

REM # Unless already being reinvoked via cmd.exe, see if the batch

REM # file is being run from PowerShell.

IF NOT %1.==_isNew. echo %PSModulePath% | findstr %USERPROFILE% >NUL

REM # If so, RE-INVOKE this batch file in a NEW cmd.exe console WINDOW.

IF NOT %1.==_isNew. IF %ERRORLEVEL% EQU 0 start "With Environment" "%~f0" _isNew & goto :EOF



echo Running from cmd.exe, setting environment variables...



REM # Set environment variables.

SET MyEnvVariable=MyValue



REM # If the batch file had to be reinvoked because it was run from PowerShell,

REM # but you want the user to retain the PowerShell experience,

REM # restart PowerShell now, after definining the env. variables.

IF %1.==_isNew. powershell.exe



GOTO :EOF

After setting all environment variables, note how the last IF statement, also re-invokes PowerShell, but in the same new window, based on the assumption that the calling user prefers working in PowerShell.

The new PowerShell session will then see newly defined environment variables, though note that you'll need two successive exit calls to close the window.

As Joe Cocker used to say "I get by with a little help from my friends".

In this case from Lieven Keersmaekers, whose comments led me to the following solution:

@echo off

setlocal

CALL :GETPARENT PARENT

IF /I "%PARENT%" == "powershell.exe" GOTO :ISPOWERSHELL

endlocal



echo Not running from Powershell 

SET MyEnvVariable=MyValue



GOTO :EOF



:GETPARENT

SET CMD=$processes = gwmi win32_process; $me = $processes ^| where {$_.ProcessId -eq $pid}; $parent = $processes ^| where {$_.ProcessId -eq $me.ParentProcessId} ; $grandParent = $processes ^| where {$_.ProcessId -eq $parent.ParentProcessId}; $greatGrandParent = $processes ^| where {$_.ProcessId -eq $grandParent.ParentProcessId}; Write-Output $greatGrandParent.Name



for /f "tokens=*" %%i in ('powershell -command "%CMD%"') do SET %1=%%i



GOTO :EOF



:ISPOWERSHELL

echo.

echo ERROR: This batch file may not be run from a PowerShell prompt

echo.

cmd /c "exit 1"

GOTO :EOF

I did something like this for Chocolatey's RefreshEnv.cmd script: Make refreshenv.bat error if powershell.exe is being used.

My solution didn't end being used, for unrelated reasons, but it's available in this repo: beatcracker/detect-batch-subshell. Here is copy of it, just in case.

Script that will only run if called directly from interactive command processor session

Script will detect if it's run from non-interactive session (cmd.exe /c detect-batch-subshell.cmd) and show approriate error message.

Non-interactive shell includes PowerShell/PowerShell ISE, Explorer, etc... Basically anything that will try to execute script by running it in the separate cmd.exe instance.

Hovewer, dropping into the cmd.exe session from PowerShell/PowerShell ISE and executing script there will work.

Dependencies

• 
  wmic.exe - comes with Windows XP Professional and up.

Example:

1. Open cmd.exe
   


2. Type detect-batch-subshell.cmd
   

Output:

> detect-batch-subshell.cmd



Running interactively in cmd.exe session.

Example:

1. Open powershell.exe
   


2. Type detect-batch-subshell.cmd
   

Output:

PS > detect-batch-subshell.cmd



detect-batch-subshell.cmd only works if run directly from cmd.exe!

Code

• detect-batch-subshell.cmd

@echo off



setlocal EnableDelayedExpansion



:: Dequote path to command processor and this script path

set ScriptPath=%~0

set CmdPath=%COMSPEC:"=%



:: Get command processor filename and filename with extension

for %%c in (!CmdPath!) do (

    set CmdExeName=%%~nxc

    set CmdName=%%~nc

)



:: Get this process' PID

:: Adapted from: http://www.dostips.com/forum/viewtopic.php?p=22675#p22675

set "uid="

for /l %%i in (1 1 128) do (

    set /a "bit=!random!&1"

    set "uid=!uid!!bit!"

)



for /f "tokens=2 delims==" %%i in (

    'wmic Process WHERE "Name='!CmdExeName!' AND CommandLine LIKE '%%!uid!%%'" GET ParentProcessID /value'

) do (

    rem Get commandline of parent

    for /f "tokens=1,2,*" %%j in (

        'wmic Process WHERE "Handle='%%i'" GET CommandLine /value'

    ) do (



        rem Strip extra CR's from wmic output

        rem http://www.dostips.com/forum/viewtopic.php?t=4266

        for /f "delims=" %%x in ("%%l") do (

            rem Dequote path to batch file, if any (3rd argument)

            set ParentScriptPath=%%x

            set ParentScriptPath=!ParentScriptPath:"=!

        )



        rem Get parent process path

        for /f "tokens=2 delims==" %%y in ("%%j") do (

            rem Dequote parent path

            set ParentPath=%%y

            set ParentPath=!ParentPath:"=!



            rem Handle different invocations: C:Windowssystem32cmd.exe , cmd.exe , cmd

            for %%p in (!CmdPath! !CmdExeName! !CmdName!) do (

                if !ParentPath!==%%p set IsCmdParent=1

            )



            rem Check if we're running in cmd.exe with /c switch and this script path as argument

            if !IsCmdParent!==1 if %%k==/c if "!ParentScriptPath!"=="%ScriptPath%" set IsExternal=1

        )

    )

)



if !IsExternal!==1 (

    echo %~nx0 only works if run directly from !CmdExeName!^^!

    exit 1

) else (

     echo Running interactively in !CmdExeName! session.

 )



endlocal