gistfile1.txt

{-# LANGUAGE OverloadedStrings #-}

import Control.Monad
import Control.Concurrent.MVar
import qualified Data.ByteString.Char8 as BS8
import Pipes.Cliff
import qualified Pipes.ByteString as PB
import System.Process
import System.IO
import System.Exit

toMVar mvar = forever $ do
  liftIO $ putStrLn "await"
  line <- await
  liftIO $ BS8.putStrLn line
  liftIO $ putMVar mvar line

client mvar = do
  yield "LiNe 1\n"
  line <- liftIO $ takeMVar mvar
  yield "LiNe 2\n"
  return ExitSuccess


mainCliff = do
  withProcess (pipeInputOutput Pipes.Cliff.Inherit (procSpec "tr" ["[A-Z]", "[a-z]"])) $
    \(toTr, fromTr) -> do
      mvar <- newEmptyMVar
      toTrAsync <- conveyor $ client mvar >-> toTr
      fromTrAsync <- conveyor $  fromTr >-> toMVar mvar
      wait toTrAsync
      wait fromTrAsync

main = do
  (hin, hout,_,ph) <- runInteractiveProcess "tr" ["[A-Z],[a-z]"] Nothing Nothing
  hSetBuffering hin NoBuffering
  hSetBuffering hout NoBuffering
  mvar <- newEmptyMVar
  toTrAsync <- async $ runEffect $ client mvar >-> PB.toHandle hin
  fromTrAsync <- async $ runEffect $ PB.fromHandle hout >-> toMVar mvar
  wait toTrAsync
  wait fromTrAsync