tail -f behaviour in ghc.

I suspect this is more of a "my patchy knowledge about file handles" question than a ghc or a Haskell question, but at the risk of revealing same in public... Is it possible to implement "follow mode" behaviour, a la tail -f, without using "seek" (or hSetPosn, which I assume is essentially seek slightly abstractified). Essentially this comes down to whether once a handle reaches "eof", whether than can be subsequently falsified. I suspect the intended and actual behaviour in all cases is "as per Unix handles", but shouldn't it in principle be specified independently thereof? Cheers, Alex.