Batch File: If registry key's data is equal to - batch-file

Question

I'm trying to make a .bat toggler for certain Explorer settings. To do this I need the batch file to query the Registry key's data and then set the key accordingly. For example, in ActionScript 3 or JavaScript it would be something along the lines of this:
if (HideFileExt == "00000000"){
HideFileExt = 00000001;
else {
HideFileExt = 00000000;
}
This way, every time it runs it will set the key's data to be the opposite of what it currently is - a toggler.
I have Google-d this extensively and after quite a long time of chopping up and splicing multiple examples, I eventually got this:
REG QUERY HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced /v HideFileExt /t REG_DWORD /d 00000000
if errorlevel 1 (
echo Num 1
) else (
echo Num 2
)
rem The "echo Num"s are there just so that I could eventually figure out what the errorlevel does
which returns the error:
ERROR: Invalid syntax.
Type "REG QUERY /? for usage.
num 1
If I remove the /d 00000000 from the REG QUERY then it returns the accurate data value of the key without error. I have also tried it with /d 0, /d 0x0 and /d 0x00000000 and they didn't work either.

Answer 1

The /d switch doesn't do what you think. It is a modifier to the /f switch, which is used to specify a search pattern. Unfortunately, /v already defines a search pattern, and they do not get along.
To check whether HideFileExt is set to 0, you can pipe reg's result to find:
reg query HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced /v HideFileExt | find "0x0"
if errorlevel 1 echo "HideFileExt is 0"
if errorlevel 0 echo "HideFileExt is not 0"

Answer 2

The Answer from Dennis is correct, but I thought id paste the whole batch file so you can see it all working.
REG QUERY "HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced" /v "HideFileExt" | Find "0x0"
IF %ERRORLEVEL% == 1 goto turnoff
If %ERRORLEVEL% == 0 goto turnon
goto end
:turnon
REG ADD "HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced" /v
HideFileExt /t REG_DWORD /f /D 1
goto end
:turnoff
REG ADD "HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced" /v
HideFileExt /t REG_DWORD /f /D 0
goto end
:end
#exit

Answer 3

In 2020 this is how you can do it:
In cmd write:
powershell -executionpolicy unrestricted C:\path_to_powershell_file.ps1
Make a powershell file with the following code and save it (Example to check if chrome is default browser):
$path = 'HKCU:\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.html\UserChoice'
$value = 'ProgId'
$path_verif = Get-itemProperty -Path $path | Select-Object -ExpandProperty $value
if($path_verif -match 'chrome'){
Write-Host "Chrome is default browser" -ForegroundColor Green
} else{
Write-Host "Chrome is NOT default browser. -ForegroundColor Red
}