Hi all,
I've got a but it code below thats not quite working as I expect
it to. The basic idea is that it opens a master/slave pair of
pseudo terminals, forks a child process and then perform
bi-directional communication between the parent and the child
via the master/slave psuedo terminal.
The thing does really need to forkProcess because once the
comms is working I want to exec another process in the child.
I also intend to dup the file descriptors so that stdin, stdout
and stderr all point to the slave's end of the pty.
The code below *almost* works. Its currently printing out:
parent : Forked child was here!
parent : Message from parent.
Read 21 bytes
while I think it should print:
parent : Forked child was here!
parent : Read 21 bytes
Any clues on why 'Message from parent.' is also ending up on
stdout? This is ghc-6.12.1 on Debian Linux.
Cheers,
Erik
import System.Posix.IO
import System.Posix.Process
import System.Posix.Terminal
import System.Posix.Types
main :: IO ()
main
= do (master, slave) <- openPseudoTerminal
_childId <- forkProcess $ forkedChild (master, slave)
closeFd slave
runParent master
runParent :: Fd -> IO ()
runParent fd
= do (str, _) <- fdRead fd 1024
putStr $ "parent : " ++ str
_ <- fdWrite fd "Message from parent.\n"
(str2, _) <- fdRead fd 1024
putStr $ "parent : " ++ str2
forkedChild :: (Fd, Fd) -> IO ()
forkedChild (master, fd)
= do closeFd master
_ <- fdWrite fd "Forked child was here!\n"
(_, count) <- fdRead fd 1024
_ <- fdWrite fd $ "Read " ++ show count ++ " bytes\n"
closeFd fd
--
----------------------------------------------------------------------
Erik de Castro Lopo
http://www.mega-nerd.com/
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