Jens Petersen wrote,

Jens Petersen writes:

Also I just rediscovered Manuel Chakravarty's HPL (Haskell Ports Library), which provides a rather elegant, sophisticated approach.

http://www.cse.unsw.edu.au/~chak/haskell/ports/

It compiles fine under ghc-5.02.2, and using the BufferMode patch included at the end output seems to be ok,

Why LineBuffering? Doesn't really change anything for me (same GHC version).

but input of more than 2048 bytes doesn't seem to be being handled reliably. [..] mostly gives no output, but occasionally I see

Warning: Ports.listenToPort: Attempted to listen to a closed port!

Needs some debugging I guess. :)

I guess, it needs more documentation. Your test program is wrong in two places. The function `listenToPort' starts to listens at the given port exactly when `listenToPort' is executed; ie, any data that goes over the port earlier will not be received in the stream that this call to `listenToPort' returns. You wrote

outpt <- newPort ' ' errpt <- newPort ' ' let p = proc cmd args p inpt outpt errpt putStrLn "output:" out <- listenToPort outpt

As the processes `cmd' is fork()ed in a separate thread, it may already have finshed its business until you get to `listenToPort outpt', which means you have missed all the data. For similar reasons

errclosed <- isClosedPort errpt unless errclosed $ do err <- listenToPort errpt

isn't recommended. I changed your program to what I have appended. It then works for me for the % cat 4096 | test-processes cat test...except that I sometimes get a "Broken Pipe". So, I guess, I have to do some debugging after all (plus improve the documentation). Cheers, Manuel PS: I'll add your program to the ports/tests/ directory if you don't mind. -=- module Main where import Processes import Ports import IO (openFile, hGetContents, IOMode(..), hSetBuffering, BufferMode(..)) import Monad (unless) main :: IO() main = do inpt <- getContents withPorts [] $ \ (cmd:args) -> do outpt <- newPort ' ' errpt <- newPort ' ' out <- listenToPort outpt err <- listenToPort errpt let p = proc cmd args p inpt outpt errpt putStrLn "output:" mapM_ putStrLn $ lines out putStrLn "error:" putStr err putStrLn "test finished"