Hung readline on pipe

[Sean Dunn]

I'm using pipe2 to spawn a process and read it's stdout..  I do the
following, yet it still hangs.  Any observations?:


# Initialization part : Bipipe is an interface to pipe2.. just pretend.
#
cmd = 'generateInfo'
inst = bipipe.BiPipe(cmd, '', 1)

(self.mPipeOut, self.mPipeErrOut, self.mPipeIn, self.mPipePID) =
(inst.fromchild,  inst.childerr, inst.tochild, inst.pid)

fcntl.fcntl(self.mPipeOut.fileno(), FCNTL.F_SETFD, FCNTL.O_NDELAY)
fcntl.fcntl(self.mPipeErrOut.fileno(), FCNTL.F_SETFD, FCNTL.O_NDELAY)



# This part is actually in a separate function..  It reads input until
there's nothing on the pipe,
# and then breaks to do other processing, but will come back to this
section later.
#
while 1:
    (readList, writeList, exList) = select.select([self.mPipeOut,
self.mPipeErrOut], [], [], 0)

    if not readList:
        break
    #if

    for item in readList:
        char = item.read(1)
        self.CollectByte(char)
    #for
#while


At first it seems to work fine.  The while 1: loop runs, gets input,
breaks out, etc.  But I think when the child process exits, and there is
still stuff in the pipe to be read (before the while 1: gets around to
it) it hangs on the read() even though the select thinks there is
something there..  I have verified that the command I'm running
generates more than is being shown.  I was using a full readline()
before the read() thinking that maybe it was just hanging on looking for
a \n, but it still doesn't work.

Any ideas on how to cure this?

Thanks!
Sean


--
Sean Dunn               "I'm afraid. I'm afraid, Dave.
Digital Anvil            Dave, my mind is going. I can feel it.
VFX Software Engineer    I can feel it. I can feel it."
--


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