Any examples of non idempotent script someone is likely to write? Because I can't think of much apart from doing some logging like 'user x logged at time y' whi

Any examples of non idempotent script someone is likely to write? Because I can't think of much apart from doing some logging like 'user x logged at time y' which is likely to be fine to be written twice because it would be anyways if you open new terminal.