Re: [Gtk2hs-users] inputAdd's FD

[Christoph B. <ic...@ch...>]

"Brandon S. Allbery KF8NH" <al...@ec...> writes:

> On Jan 2, 2010, at 07:33 , Christoph Bauer wrote:
>> how do I use inputAdd from System.Glib.Mainloop? FD is an Int.
>> (This isn't visible in the documentation.)
>>
>> Fortunatly I need this for Linux, so I could create an ffi-call
>> to open(), but I guess I missed something.
>
>
> After studying the internals a bit, I ended up with:
>
> 	fdFD :: Fd -> Int
> 	fdFD (Fd fd) = fromEnum fd
>
> (Fd being System.Posix.IO.Fd)

Thanks. I the meantime I found a similar approach.  (But instead of
fromEnum is replaced by fromIntegral. Is there a difference?)

Unfortunatly I have another problem. Maybe it's more a glib, poll()
or unix problem, but maybe someone has a hint for me.

I'm waiting for a named pipe. A shell skript can write to the
pipe to control my program. The shell skript simply does an

echo cmd > /tmp/namedpipe

main = ...
   inputAdd fd [IOIn] priorityDefault (controlMe fd app)

controlMe fd app = do
  (s, l) <- fdRead fd 1024 `catch` \ _ -> return ("", 0)
  when (l > 0) $ writeIORef (skipVar app) True
  return (s /= "quit")

It works - but after the first command my program uses 100% CPU.

strace shows, that the epoll()-call returns with revents=POLLHUP.

poll([{fd=6, events=POLLIN}, {fd=9, events=POLLIN}], 2, 88) = 1 ([{fd=9, revents=POLLHUP}])

Is there a solution to this problem? My only idea is to close/reopen
my named pipe.

Thanks