«

I'm pretty sure I've exhausted all searches and read all the forums
Google will turn up related to this issue.

I touch an empty file in a sh shell, fire up the python shell, open
the file for reading(tried all buffering options), register it with a
poll object for select.POLLIN and call poll(), but the poll never
blocks and always returns for the FD, EVENT combination I ask for, but
the file has not anything written to it.

Here's an example snippet:
>>> fd = os.open('/tmp/poll_test', os.O_RDONLY | os.O_SYNC)
>>> p = select.poll()
>>> p.register(fd, select.POLLIN)
>>> s = p.poll()
>>> os.read(fd, 10)
''
>>> s
[(3, 1)]
>>> fd
3

I was using the open builtin originally, but a forum I read suggested
that this created user level buffers that the system call wouldn't
know about(which didn't completely jive with me), so I switched to the
lower level os.open.

Am I not getting the proper spirit of select.poll? I know that read()
never blocks and I think I read somewhere that poll will return fd
that will not block for the EVENT registered -so in that regard it's
fitting.

Any help on what I'm missing would be appreciated.

"birdsong" <>wrote:

8<----------- select not blocking on empty file stuff -----------------

> Any help on what I'm missing would be appreciated.

Why do you expect it to block?
It is ready to read, to return end of file.

- Hendrik

On Feb 11, 10:36*pm, "Hendrik van Rooyen" <m...@microcorp.co.za>
wrote:
> "birdsong" <dav...@gmail.com>wrote:
>
> 8<----------- select not blocking on empty file stuff -----------------
>
> > Any help on what I'm missing would be appreciated.
>
> Why do you expect it to block?
> It is ready to read, to return end of file.
>
I expected it to block because of the name and meaning of the flag,
POLLIN, which I thought meant new data has arrived to be read. Since
I only registered a single file descriptor, I would have expected poll
to not return until there was new data to be read. I understand now
that it is not the case.