Hello.
Playing with GHC, I met some oddity.
Consider the example:
> import IO
> import Concurrent
> import Posix
> import PosixIO
>
> main = do
> (fdIn, fdIn_send) <- createPipe
> hIn_send <- fdToHandle fdIn_send
> hIn <- fdToHandle fdIn
> -- The "waiter" is a simple tk/tcl script which
> -- prints "click" anytime I click a button.
> runProcess "./waiter" [] Nothing Nothing
> Nothing (Just hIn_send) Nothing
> -- hSetBuffering hIn LineBuffering {-2-}
> -- hSetBuffering stdin LineBuffering
> forkIO(interact stdin)
> -- forkIO(interact hIn) {-1-}
> main_cycle
> where
> interact hIn = do
> line <- hGetLine hIn
> numIn <- handleToInt {-made from handleToFd & fdToInt-}
> -- threadWaitRead numIn {-3-}
> putStrLn line
> interact hIn
> main_cycle = do
> putStrLn "tick"
> threadDelay 1000000
> main_cycle
The example works OK. It prints "tick" once a second and dups my input
as I type it. But, when I uncomment the line {-1-} to handle input from
child as well, everything is hanged on this read operation. Uncommenting
the {-3-} line helps, but, first, I'm not sure it is a right way and,
second, the matter is still unclear - what is the reason of such
difference?
Uncommenting the {-2-} lines doesn't help. I thing the reason is in
some inner properties of the handlers, but have no idea in which one.
Max.
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