On Oct 16, 2007, at 1:48 PM, John Goerzen wrote:
I have been trying to implement a Haskell-like version of shell pipelines using runInteractiveProcess. I am essentially using hGetContents to grab the output from one command, and passing that to (forkIO $ hPutStr) to write to the next. Slow, but this is just an experiment.
As an aside, I personally would look to System.Posix.Process for this. Something like this would deal with the file descriptors in the fork ... fdfork fn dupfds closefds = do pid <- forkProcess $ execio return pid where dupe (a, b) = do dupTo a b closeFd a execio = do mapM_ dupe dupfds mapM_ closeFd closefds fn ... and then you can put the pipes directly between the processes ... -- date | tr '[A-Z]' '[a-z]' | read (a0, a1) <- createPipe (b0, b1) <- createPipe p1 <- fdfork tr [(b0, 0), (a1, 1)] [a0, b1] closeFd a1 p2 <- fdfork date [(b1, 1)] [a0, b0] closeFd b1 readfd a0 -- implementation left to reader where date = executeFile "/bin/date" False [] Nothing tr = executeFile "/usr/bin/tr" False ["[A-Z]", "[a-z]"] Nothing There's probably a nice way to wrap that up, so you're not keeping track of the file descriptors for all the pipes. Donn Cave, donn@drizzle.com