Batch variables not expanding at execution time - windows

Question

I'm writing a small inventory script for my IT department and I've run into a little stumbling block while trying to save myself some time.
My goal is to store the current location in a temporary local file (this batch file will be run on a flash drive) so that when I move from one computer to the next, I only have to change the location if it is not accurate. Basically so that if I start in Unit 1, Building A, Room 3, I only have to confirm what is correct and change what isn't.
Perhaps the location confirmation code will give you a better idea of what's going on here.
#echo off
setlocal
setlocal EnableDelayedExpansion
if not exist location.tmp (
echo , , > location.tmp
)
for /f "tokens=1-3 delims=," %%i in (location.tmp) do (
if not "%%i" == " " (
set unit=%%i
)
if not "%%j" == " " (
set building=%%j
)
if not "%%k" == " " (
set room=%%k
)
)
for %%i in (unit,building,room) do (
call :SUB_GET %%i
)
echo !unit!,!building!,!room!> location.tmp
endlocal
exit /b 0
:SUB_GET
if not defined %1 (
set /p %1=What %1?
goto :EOF
)
set /p new%1=What %1? (default is !%1!)
if not "!new%1!" == "" (
set %1=!new%1!
)
Everything works, except for when I try to allow it to keep the default. I want to be able to just hit enter if the value is correct, (e.g. "What room? (default is 403)" hit enter and then it keeps 403)
The problem is, when I do that, even though the code checks the new environment variable (the input) to see if it is empty, it still assigns the old variable the value of the new one (empty string).
What's even more confusing is if I create an existing location.tmp with defaults (like 1,A,4) and hit enter to confirm each one, the batch statement echo !unit!,!building!,!room!>location.tmp executes, but location.tmp is unchanged.
Any ideas what's going on here?

Answer 1

set /p %1=What %1? (default is !%1!)
If you simply reply Enter to set /p then the variable remains unchanged.
So - no need for new%1 - and even then new would have been sufficient as there is no obvious need for newROOM etc. You'd have had to clear new judiciously to avoid retaining stale data though.

Answer 2

The delayed execution of the variables in the line echo !unit!,!building!,!room!>location.tmp is causing them to be expanded too late and thus the statement doesn't properly execute for whatever reason. Replacing them with normal %variables% fixes both issues. It turns out the comparison was working correctly, just not getting expanded in time.
EDIT: No idea why, but the above is incorrect. The below script works perfectly fine...
#echo off
setlocal
setlocal EnableDelayedExpansion
if not exist location.tmp (
echo , , > location.tmp
)
for /f "tokens=1-3 delims=," %%i in (location.tmp) do (
if not "%%i" == " " (
set unit=%%i
)
if not "%%j" == " " (
set building=%%j
)
if not "%%k" == " " (
set room=%%k
)
)
for %%i in (unit,building,room) do (
call :SUB_GET %%i
)
echo !unit!,!building!,!room!> location.tmp
endlocal
exit /b 0
:SUB_GET
if not defined %1 (
set /p %1=What %1?
goto :EOF
)
set /p %1=What %1? (default is !%1!)