echo Error >/does/not/exist; echo One:$?
t=BAD
t=Ok >>/cant/be/created; echo One:$?
echo $t
! >/cant/be/created; echo Zero:$?
exec >/cant/be/created; echo One:$?
exec /bin/true >/cant/be/created; echo One:$?
! exec /bin/true >/cant/be/created; echo Zero:$?
echo Done