Glynn Clements wrote:
I have tried to use the various POpen-like implementations out there, but _none_ of them works with the most current GHC. Is there any way to communicate with external programs at the moment? Posix-only would be suffice at the moment.
There's the DIY solution, i.e. a direct translation of how popen() is implemented in C, e.g.:
module Main where
import IO import System import System.Posix
main = do (rfd, wfd) <- createPipe pid <- forkProcess (proc rfd wfd) closeFd wfd hRead <- fdToHandle rfd str <- hGetContents hRead putStr str stat <- getProcessStatus True False pid case stat of (Just (Exited code)) -> exitWith code _ -> exitWith (ExitFailure 127) where proc rfd wfd = do closeFd rfd dupTo wfd stdOutput executeFile "/bin/ls" False ["-l"] Nothing
The above has been (briefly) tested with ghc 6.2.1.
I had forgotten about Simon's System.Process module (at the time of the announcement, I was still on GHC 5.04.2, so I couldn't test it). Here's a version of the above code which uses runProcess:
module Main where
import IO ( hGetContents , hClose ) import System ( exitWith ) import System.Process ( runProcess , waitForProcess ) import System.Posix ( createPipe , fdToHandle )
main = do (rfd, wfd) <- createPipe hRead <- fdToHandle rfd hWrite <- fdToHandle wfd handle <- runProcess "/bin/ls" ["-l"] Nothing Nothing (Just hWrite) Nothing hClose hWrite str <- hGetContents hRead putStr str code <- waitForProcess handle exitWith code
And another version which uses runInteractiveProcess:
module Main where
import IO ( hGetContents ) import System ( exitWith ) import System.Process ( runInteractiveProcess , waitForProcess )
main = do (_, hOut, _, handle) <- runInteractiveProcess "/bin/ls" ["-l"] Nothing str <- hGetContents hOut putStr str code <- waitForProcess handle exitWith code
This last one isn't quite the same as popen(), as it automatically
associates each of the three standard descriptors with their own pipe,
whereas popen() only redirects one of stdin or stdout, while the other
one and stderr are inherited from the caller.
--
Glynn Clements