You are right, perhaps "guess" is the wrong term, I meant that it is unreasonably hard to identify and remember which is which.

Usually you settle on one or two “go to” functions, if you don’t write your own wrapper function anyway. Given the subtleties of their semantics, fully descriptive names also seem unachievable. But really, familiarity comes with repeated exposure. If you use these every day, you’ll learn rather quickly.

It's a good point. To be fair, any system that lasts as long as C has will have legacy cruft that you need to learn to step around and it's hard to get rid of. Relative to other standards, C has been remarkably disciplined at keeping things clean.