[Haskell] runProcess with out=err

[Simon Marlow]

On 28 July 2005 14:35, Ian Lynagh wrote:

> With the below code (compiled by ghc) I get
> "a.out: thread blocked indefinitely".
> 
> Changing the second (Just hout) to Nothing makes it run as expected.
> 
> If I dup fdout to get an fderr and then try to also convert that to
> a handle then I get "a.out: openFile: resource busy (file is locked)".
> 
> Is there a way to write this with stdout and stderr going to the same
> handle?
> 
> -------------------
> module Main (main) where
> 
> import System.Posix (openFd, defaultFileFlags, stdFileMode,
>                      OpenMode(ReadOnly, WriteOnly), fdToHandle)
> import System.Process (runProcess, waitForProcess)
> 
> main :: IO ()
> main = exec "echo" ["foo"] "in" "out"
> 
> exec :: String -> [String] -> FilePath -> FilePath -> IO ()
> exec c args inp out
>  = do fdin <- openFd inp ReadOnly Nothing defaultFileFlags
>       fdout <- openFd out WriteOnly (Just stdFileMode)
>       defaultFileFlags hin <- fdToHandle fdin
>       hout <- fdToHandle fdout
>       ph <- runProcess c args Nothing Nothing
>                        (Just hin) (Just hout) (Just hout)
>       waitForProcess ph >>= print

This bug was fixed in rev. 1.12 of System.Process.Internals, and has
been merged into the 6.4 branch.

Cheers,
	Simon