Subj : Re: Threading and Timeouts
To   : comp.programming.threads
From : Giancarlo Niccolai
Date : Thu Jul 21 2005 01:20 am

Marcin 'Qrczak' Kowalczyk wrote:

> Giancarlo Niccolai <searchforme@ingoogle.com> writes:
> 
>> If any of this weren't the case, then the POSIX specifications about
>> select() wouldn't be possibly fulfilled, as it explicitly says that after
>> that select() declares a socket ready, it MUST NOT BLOCK the very next
>> operation for which select() was queried .
> 
> POSIX specification for write() says that for pipes and fifos a
> partial write is only possible with O_NONBLOCK set. It implies that
> this is true also for other descriptors which are not files, e.g.:
> 
>        When attempting to write to a file descriptor (other  than  a  pipe
>         or
>        FIFO)  that  supports  non-blocking  writes  and cannot accept the
>        data immediately:
> 
>         * If the O_NONBLOCK flag is clear, write()  shall  block  the 
>         calling
>           thread until the data can be accepted.
> 
>         * If  the  O_NONBLOCK flag is set, write() shall not block the
>         thread.
>           If some data can be written without  blocking  the  thread, 
>           write() shall write what it can and return the number of bytes
>           written. Oth- erwise, it shall return -1 and set errno to
>           [EAGAIN].
> 

Yes. It specifically cites pipe and FIFO writes as exceptions; for normal
files and sockets (and for reads), the behavior is what I have described.
So this does not invalidates what I am saying.

Bests,
Giancarlo.

.