[Haskell-cafe] Re: Silly I/O question

John Goerzen writes:

That failed, though, because getContents closes the file after it's been completely read (ugh -- why?).

getContents reads from standard input: you can't seek on that stream. Just think of "cat String -> IO () printTimes n msg = sequence_ (replicate n (putStr msg)) printTimes' :: Int -> String -> IO () printTimes' n msg = putStr (concat (replicate n msg)) This means, unfortunately, that you'll have to keep the whole file in memory, but if you want to read from standard input, there is no way around that. You could read the contents once, write it to a temporary file, and then copy it multiple times from there. Then you could do it in blocks. But that's probably not what you want to do.

But I couldn't figure out a way to make this either properly tail-recursive while handling the exception, or to avoid polling for EOF each time through the function.

You might want to write a function that copies the file _once_ and then just call that function several times. Like in the examples above. I don't think you need explicit recursion at all. Hope this is helpful. Peter