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Date: Fri, 22 Jan 2016 09:41:02 -0500
From: Diane Bruce <db@db.net>
To: Mateusz Guzik <mjguzik@gmail.com>, Jilles Tjoelker <jilles@stack.nl>,
 "Batutis, Ed" <Ed.Batutis@netapp.com>,
 "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org>,
 Diane Bruce <db@db.net>, Joerg Sonnenberger <joerg@britannica.bec.de>
Subject: Re: get number of open files in a process?
Message-ID: <20160122144102.GA92956@night.db.net>
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On Thu, Jan 21, 2016 at 11:51:11PM +0100, Mateusz Guzik wrote:
> On Thu, Jan 21, 2016 at 11:45:11PM +0100, Jilles Tjoelker wrote:
> > On Thu, Jan 21, 2016 at 07:44:01PM +0000, Batutis, Ed wrote:
...
> 
> This cannot work. POSIX mandates the lowest free fd is returned, so the
> N you see here can be extremely low, while the process is running out of
> fds.

The hack not mentioned here of course is to (mis-)use dup2() to shuffle
all your other fd's down by one as you close them. ;)

(This actually was used in early versions of the IRC Daemon. ;)
 Not for this reason however. )

> one to take - you have to have a very big reserve to not suddenly run
> out of fds, one would just limit amount of clients and, well, handle
> errors as they can pop up for reasons other than running out of fd slots.

I agree.

> 
> -- 
> Mateusz Guzik <mjguzik gmail.com>
> 

Diane
-- 
- db@FreeBSD.org db@db.net http://www.db.net/~db