Ask user for Yes/No confirmation.
Used in a bat file to set errorlevel to 0 if user answers Y,
or 1 if N.
echo Do you really want to do this dangerous thing?
If ERRORLEVEL 1 GoTo NO
The confirm.exe version also looks for SET confirm=y or SET
confirm=n. If it sees it, the user does not need to key anything. It
acts as if the user had hit the Y or N.