Re: [Haskell-cafe] createProcess running non-existent programs

Well, overhead or not, it would be nice to at least have *some* solution. Currently, it just doesn't work. I am sure that as soon the functionality is there, somebody will step in to fake it fast. On 15/08/12 06:25, Donn Cave wrote:

Quoth Alexander Kjeldaas ,

...

See access(2)

... a classic "code smell" in UNIX programming, for the same reasons.

We can solve this problem in an efficient way that works well, and equally well, on any POSIX platform that supports F_CLOEXEC on pipes, and I can't think of anything that doesn't. The appended code is the basic gist of it. This was not invented by the Python world, but as suggested it's one of the things that we'd get from a review of their subprocess module.

Donn

spawn file cmd env = do (e0, e1) <- pipe fcntlSetFlag e1 F_CLOEXEC t <- fork (fex e0 e1) close e1 rx <- readFd e0 256 if null rx then return t else ioerr (chrToErrType rx) file where fex e0 e1 = do close e0 catch (execve file cmd env) (\ e -> writeFd e1 (errToChr e : ioeGetErrorString e)) ioerr (e, s) file = ioError (mkIOError e s Nothing (Just file))

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