or if test $num -eq 42, which is the most sensible way to do it in my view, since it really makes the point clear that what you're really evaluating is the exit

or if test $num -eq 42, which is the most sensible way to do it in my view, since it really makes the point clear that what you're really evaluating is the exit status of the evaluated command (and where '[' is simply an alias to 'test')