Subj : Re: Threading and Timeouts
To   : comp.programming.threads
From : Marcin 'Qrczak' Kowalczyk
Date : Thu Jul 21 2005 12:40 am

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].

-- 
   __("<         Marcin Kowalczyk
   \__/       qrczak@knm.org.pl
    ^^     http://qrnik.knm.org.pl/~qrczak/

.