How do I clear all environment variables from a Windows shell session?

Question

If I start a new Windows shell session and type:

env

I see lots of environment variables set. I want to debug the running of a command line program by removing all environment variables from the current shell session.

I could go though one by one with the following approach:

SET FOO=
SET BAR=
SET ... ... ...

However is there a simple way to clear them all in one go?

Answer 1

You can write this in a batch file:

@echo off
if exist ".\backupenv.bat" del ".\backupenv.bat"
for /f "tokens=1* delims==" %%a in ('set') do (
echo set %%a=%%b>> .\backupenv.bat
set %%a=
)

It basically runs through each environment variable, backs them up to a batch file (backupenv.bat) and then clears each variable. To restore them you can run the backupenv.bat file.