CMD script to verify that DNS server is up and running. Useful for pihole.

verify_dns.cmd

@echo off
setlocal
if "%~1"=="" ( ECHO Specify DNS server to verify, e.g. %~nx0 192.168.1.17 & GOTO :EOF)
set DNSSERVER=%~1

REM To have this script run on user login:
REM
REM taskschd.msc
REM Action, Create Basic Task
REM Name: verify_htpc_pihole
REM Start: When I log on
REM Action: Start a program
REM Program: %windir%\system32\cmd.exe
REM Arguments: /c e:\bin\verify_htpc_pihole.cmd 192.168.1.17

ECHO Verifying DNS server at %DNSSERVER% . . .

:LOOP
set OUT=
for /f "usebackq delims=" %%f in (`nslookup.exe microsoft.com %DNSSERVER% 2^>nul`) do (
    SET OUT=%%f
    REM Only want first line of output.
    GOTO :DONE
)

:DONE
REM Should be "Server:  pi.hole"
if "%OUT:~0,7%"=="Server:" (
    GOTO :EOF
)

REM Assume "DNS request timed out."
echo DNS server unavailable! Retrying in 5 seconds...
REM Sleep for 5 seconds.
ping -n 6 127.0.0.1 >nul
GOTO :LOOP