[Twisted-Python] Opening a fifo

[Phil Mayers]

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')
1

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?