Should the file be closed when the last byte is read (in this case its definitely reading all four bytes) or when the first byte after that is read (in this case it probably doesn't attempt to read more than 4 bytes)?
I'll answer my own question. Both Prelude.readFile and Data.ByteString.Lazy.Char8.readFile will keep the file open after reading the last byte and close it when trying to read further. Proof: module Main where import Control.Applicative -- import qualified Data.ByteString.Lazy.Char8 as B import Prelude as B stateFile = "1word32.bin" main = do x <- B.take 4 <$> B.readFile stateFile -- x <- B.take 5 <$> B.readFile stateFile print x B.writeFile stateFile x This works for Prelude and ByteString when taking 5 (there are exactly 4 bytes in "1word32.bin") and fail when taking 4. I'm not sure that this behavior is so bad.. there might be some advantages... but it might be nice to have it close after the last byte is read... However, I think probably the real blame here should probably go to Data.Binary which doesn't attempt to check that it has consumed all of its input after doing a "decode". If "decode" completes and there is unconsumed data, it should probably raise an error (it already raises errors for premature EOF). There's no reason for it not to, since it does not provide the unconsumed data to the caller when its done, anyway... Thoughts? Tim Newsham http://www.thenewsh.com/~newsham/