On Thu, 2009-09-10 at 16:05 +0100, Ian Lynagh wrote:
On Wed, Aug 26, 2009 at 05:42:19PM +0100, Simon Marlow wrote:
As far as buffering goes, Handles currently couple buffering modes, which is potentially frustrating if one wants, e.g., no buffering on recv, but block buffering on send.
Buffering is always invisible on input - if there is any input available, you'll see it immediately. It has performance implications only - but I can't imagine you'd want to deliberately reduce performance by turning off buffering (in fact, I think the new I/O library doesn't even honour NoBuffering on input Handles).
So is this program supposed to not be valid (or at least, to not behave as I would expect)?
import Control.Monad import System.Environment import System.IO import System.Posix.Process
main :: IO () main = do [get] <- getArgs hSetBuffering stdin NoBuffering when (read get) $ do x <- hGetChar stdin putStrLn ("Got: " ++ show x) executeFile "cat" True [] Nothing
So you're accessing the stdin file descriptor via the stdin Handle and also directly via cat. Note that there's no API in Haskell code to get at the unadorned FD while keeping the Handle open. Duncan