[Haskell-cafe] createProcess shutting file handles
duncan.coutts at worc.ox.ac.uk
Sun Feb 15 08:07:22 EST 2009
On Sun, 2009-02-15 at 11:06 +0000, Duncan Coutts wrote:
> On Sun, 2009-02-15 at 09:24 +0000, Neil Mitchell wrote:
> > Hi
> > >> What have I done wrong? Did createProcess close the handle, and is
> > >> there a way round this?
> > >
> > > The docs for runProcess says:
> > >
> > > Any Handles passed to runProcess are placed immediately in the
> > > closed state.
> > >
> > > but the equivalent seems to be missing from the documentation for
> > > createProcess.
> > However the createProcess command structure has the close_fds flag,
> > which seems like it should override that behaviour, and therefore this
> > seems like a bug in createProcess.
> close_fds :: Bool
> Close all file descriptors except stdin, stdout and stderr in
> the new process
> This refers to inheriting open unix file descriptors (or Win32 HANDLEs)
> in the child process. It's not the same as closing the Haskell98 Handles
> in the parent process that you pass to the child process.
So lets not talk about if the current behaviour is a bug or not. It's
reasonably clear (if not brilliantly well documented) that it's the
The thing we want to talk about is what reason is there for the current
behaviour, if that's necessary and if it is the sensible default
behaviour. As I said before I don't know why it is the way it is. I'm
cc'ing the ghc users list in the hope that someone there might know.
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