@echo off & SetLocal EnableDelayedExpansion
set ran_no=%random:~-1,1%%random:~-1,1%%random:~-1,1%%random:~-1,1%
for /f "tokens=1* delims=:" %%a in ('findstr /n .* 1.txt') do (
set string=%%b
echo"!string!"|findstr /c:"code=1000" >nul && (
set string=!string:1000=%ran_no%!
echo\!string!
) || (echo\!string!)
)
pause
