Re: [Haskell-cafe] trying to understand runProcess handles

On Fri, Mar 03, 2006 at 09:05:49AM -0800, Donn Cave wrote:

To: haskell-cafe@haskell.org From: Donn Cave Date: Fri, 3 Mar 2006 09:05:49 -0800 (PST) Subject: Re: [Haskell-cafe] trying to understand runProcess handles

On Thu, 2 Mar 2006, Matthias Fischmann wrote: ...

...

The problem is that gnuplot terminates right away after it tries to read from stdin (I can see the shadow of a window appear and vanish immediately). I tried setFdOption, with no effect. Is this because the handles passed to runProcess are closed in the parent process, and therefore the pipe is teared down and useless?

I don't think so: If I run 'find /' instead of gnuplot, the process happily starts and I can hGetLine from stdout.

That doesn't necessarily disprove your hypothesis, since "find" doesn't read input. You might try "tr" instead, for example. I don't see anything about what you were doing that would be obviously different from runProcessInteractive, but as long as you're making a pipe for error output, you may as well read it and see if gnuplot has left any clue to its problem there.

that doesn't work -- all the handles are closed at least after the process has died. hard to tell whether the process dying caused the handles to close or whether the handles were closed already by then. m.