[Twisted-Python] Opening a fifo

Phil Mayers p.mayers at imperial.ac.uk
Fri Nov 14 06:00:33 EST 2008

Paul Thomas wrote:
> On 14 Nov 2008, at 09:47, Phil Mayers wrote:
>> Paul Thomas wrote:
>>> Hi,
>>> I've run into a small problem where my twisted application needs to 
>>> open a fifo to talk to another process. On Linux at least, the open 
>>> blocks until the other end of the fifo is opened and this is blocking 
>>> my reactor.
>> Either of:
>> fd = os.open('thefifo', os.O_RDONLY | os.O_NONBLOCK)
>> fd = os.open('thefifo', os.O_RDWR)
>> ...will return immediately,
>> Try "man fifo" for a description of the vagaries.
> I've tried RDWR and I get errors in writing. I really need O_WRONLY, and 
> that fails with O_NONBLOCK unless the other end is open. Maybe I'll 
> chase down the RDWR problem again.

Really? It works for me in a repl:

[pjm3 at wildfire ~]$ mkfifo blah
[pjm3 at wildfire ~]$ python
 >>> import os
 >>> fd = os.open('blah', os.O_RDWR)
 >>> os.write(fd, 'a')

What errors are you getting? Possibly Twisted is getting confused 
because the fd is "readable" as well as "writeable".

Do you have sample code that's failing?

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