[Haskell-cafe] createProcess running non-existent programs
mail at nh2.me
Fri Aug 31 03:19:30 CEST 2012
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 <alexander.kjeldaas at gmail.com>,
>> 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.
> 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
> 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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