think pipes: if an external process takes input via a handle and provides output via a handle, the haskell equivalent could do the same via a Chan, so it'd be easy to write mixed pipes.
for illustration, here is the kind of utility that i find missing in System.Process, using the Maybe lifting of Chan contents. this doesn't do any error handling, but allows for simple-minded pipes like: $ ghc -e 'cmd "cat" >|> fun (map Data.Char.toUpper) >|> cmd "grep WO" >>= \(i,o)->i "hello\nWORLD\n">>o >>= putStr' ProcUtils.hs WORLD $ ghc -e 'cmd "ls" >|> fun (map Data.Char.toUpper) >|> cmd "grep .HS" >>= \(i,o)->o >>= putStr' ProcUtils.hs PROCUTILS.HS X.HS Y.HS Z.HS lifting contents to Maybe is easy enough, i just find it hard to see the use-case for getChanContents without such lifting or any way to close Chans? claus ---------------------------------------------------pipe utitlities import System.Process import Control.Concurrent import System.IO import Data.Maybe cmd c = runInteractiveCommand c >>= \(i,o,e,p)->return (hPutStr i,hGetContents o) fun f = do i <- newChan o <- newChan forkIO $ fromChan i >>= toChan o . f return (toChan i,fromChan o) infixr >|> c1 >|> c2 = do (i1,o1) <- c1 (i2,o2) <- c2 forkIO $ o1 >>= i2 return (i1,o2) toChan c str = writeList2Chan c $ map Just str ++ [Nothing] fromChan c = getChanContents c >>= return . map fromJust . takeWhile isJust