PIPE_BUF Was: Logging for critical messgaes

[Stanley Hopcroft]

On Fri, Dec 12, 2003 at 11:48:40AM -0500, Al Tobey wrote:
> 
> On Solaris: grep PIPE_BUF /usr/include/limits.h
> Linux: grep PIPE_BUF /usr/include/linux/limits.h
> Others: find /usr/include -type f -exec grep PIPE_BUF {} \;
>

  .. snip  

> Maybe it'd be worthwhile to teach configure how to discover this value
> and set it up instead of defaulting to the LCD.  Another option could be
> to call flock() where possible and ignore the atomic write size.  This
> is what I do in Nagios::Cmd.
>

To sum up :-

1 use min(PIPE_BUF_Sol, PIPE_BUF_Linux, PIPE_BUF_SysV, ..) 
  or the POSIX minimum value (512) for 'conforming implementations'.

1.1 Another approach (perhaps) to having configure determine a platform
dependent value - and therefore take advantage of local large values -
is the pathconfig() function

. make a fifo

. long local_pipe_buf = pathconf(my_fifo, _PC_PIPE_BUF);

(from 'Advanced Programming in the Unix Environment' ch 2).

2 Don't bother about atomicity promises from kernels; do it in
userland by each process using flock() with LOCK_EX to guarantee that
only one process is writing at a time and can therefore write as much as
it wants to

Thanks again for the crisp, educational thread and thank you Al for what
looks like a superb Perl module for Nagios.

Yours sincerely.

-- 
------------------------------------------------------------------------
Stanley Hopcroft
------------------------------------------------------------------------

'...No man is an island, entire of itself; every man is a piece of the
continent, a part of the main. If a clod be washed away by the sea,
Europe is the less, as well as if a promontory were, as well as if a
manor of thy friend's or of thine own were. Any man's death diminishes
me, because I am involved in mankind; and therefore never send to know
for whom the bell tolls; it tolls for thee...'

from Meditation 17, J Donne.


-------------------------------------------------------
This SF.net email is sponsored by: IBM Linux Tutorials.
Become an expert in LINUX or just sharpen your skills.  Sign up for IBM's
Free Linux Tutorials.  Learn everything from the bash shell to sys admin.
Click now! http://ads.osdn.com/?ad_id=1278&alloc_id=3371&op=click