Question

I am running the following cmd to set my system environment variable.

call C:\Windows\system32>reg add "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control
\Session Manager\Environment" /v JAVA_HOME /t REG_EXPAND_SZ /d "C:\Program Files\Java
\jdk1.6.0_37"

I want to do something similar with my path, but I dont want to overwrite the values that are there, I just want to add to them. Will running the above command overwrite or update? If it overwrites how would I get it to update instead?

Answer 1

Yes, REG ADD will overwrite the existing value, but I wrote a script that should help you.

Please pay attention to the characters after delims=: these aren’t spaces, it’s a single tab character (ASCII #9).

@ECHO OFF
REM Declare all variables as local.
SETLOCAL

SET GET_PATH=REG QUERY "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment" /v Path
SET SET_PATH=REG ADD "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment" /v Path /t REG_EXPAND_SZ /f /d

REM Get %PATH% from registry and filter REG output (drop all but actual %PATH% value).
FOR /F "tokens=3* delims=   " %%P IN ('%GET_PATH% ^| FINDSTR Path') DO SET RESULT=%%P

REM Check for the trailing semicolon.
IF "%RESULT:~-1%" == ";" (SET SEMICOLON=) ELSE (SET SEMICOLON=;)

REM Add new directories to %PATH%. 
SET DIRS=C:\Foo\Bar;E:\Bar\Baz
SET RESULT=%RESULT%%SEMICOLON%%DIRS%

REM Save result to the registry.
%SET_PATH% "%RESULT%"