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Date:      Tue, 28 Feb 2012 12:47:28 +0000
From:      Anton Shterenlikht <mexas@bristol.ac.uk>
To:        Jerome Herman <jherman@dichotomia.fr>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: posix compliance
Message-ID:  <20120228124728.GA57348@mech-cluster241.men.bris.ac.uk>
In-Reply-To: <4F4CC8D1.4070000@dichotomia.fr>
References:  <20120228091746.GA48977@mech-cluster241.men.bris.ac.uk> <4F4CB09B.7010806@herveybayaustralia.com.au> <20120228110323.GA56536@mech-cluster241.men.bris.ac.uk> <20120228062537.31ac74c0@scorpio> <20120228113213.GA56638@mech-cluster241.men.bris.ac.uk> <4F4CC8D1.4070000@dichotomia.fr>

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On Tue, Feb 28, 2012 at 01:30:09PM +0100, Jerome Herman wrote:
> On 28/02/2012 12:32, Anton Shterenlikht wrote:
> >On Tue, Feb 28, 2012 at 06:25:37AM -0500, Jerry wrote:
> >>On Tue, 28 Feb 2012 11:03:23 +0000
> >>Anton Shterenlikht articulated:
> >>
> >>>On Tue, Feb 28, 2012 at 08:46:51PM +1000, Da Rock wrote:
> >>>>On 02/28/12 19:17, Anton Shterenlikht wrote:
> >>>>>I'm putting together a small presentation
> >>>>>about FreeBSD for our IT support staff.
> >>>>>
> >>>>>Is fbsd POSIX compliant? Fully? Partially?
> >>>>>
> >>>>>The info here is a bit out of date:
> >>>>>
> >>>>>http://www.freebsd.org/projects/c99/index.html
> >>>>Looking at the doc its not that out of date. Just check the 9.x
> >>>>column.
> >>>Oh.. I see. I only looked in the top table.
> >>>
> >>>Still, I don't get an idea from the table of
> >>>how close FreeBSD is to full POSIX compliance.
> >>>I guess that's the aim, isn't it?
> >>The answer is rather simple. In your presentation you would simple
> >>indicate that FreeBSD is not fully compliant. You then have the option
> >>of making copies of all the pages referenced in the above URL and
> >>including them in the presentation packet you are supplying to the group
> >>or simply referring them to the above URL. Figuring out which is more
> >>impressive I'll leave up to you.
> >sorry to be a pain.
> >
> >Are we talking 10%, 50%, 90% complete?
> >
> >Does the above page include all tasks
> >that need to be completed? In other words,
> >if all tasks on the above page are ticked,
> >does this aumtomatically give 100% compliance,
> >or is it not that simple?
> >
> It is not that simple, POSIX is more a set of norms than a norm by 
> itself. There are Posix aspects that are not in FreeBSD and probably 
> never will be, other aspects that do exist in FreeBSD but you should 
> definitly not use them as they are painfull to use or flawed or both 
> (Posix capabilities for exemple). Also there are systems that do support 
> a fair part of Posix, but which are just a pain to use in a Posix 
> compatible environment, basically requiring you to code quite a lot of 
> tools to have a Posix environment. Basically Windows Server supports 
> quite a good deal of Posix norms, and it works well for small projects 
> or simple programs, but if you want to create a Posix compliant 
> distributed datastore you are in for a hell of a ride. Linux is becoming 
> basically the same, in that more and more core system tools have 
> dependencies on Linux specific API. (And I won't talk about MacOS X)
> A good way of making a presentation would be to first look at what 
> aspects of Posix you need and try to find out where these aspect are 
> best supported.
> Now a simple and true enough answer would be to say that FreeBSD has one 
> of the broader _and most usable_ Posix support, second only to Solaris. 
> (Way better than AIX and on par with HP-UX in my humble opinion). It is 
> mostly true in the sense that FreeBSD does support quite a lot of Posix 
> norms including the latest ones. It is false int the sense that AIX, 
> HP-UX IRIX and quite alot of others have a 100% certified compliance for 
> some (quite old now) Posix norms.  CF :
> http://en.wikipedia.org/wiki/POSIX
> http://en.wikipedia.org/wiki/Single_UNIX_Specification#BSD_descendants
> 
> At one point FreeBSD was very close to be fully Posix compliant with 
> norm 1.e, then norm 1.e was more or less thrown out the windows, and 
> posix norming system pretty much imploded at this time.
> 
> So basically it is quite hard to answer without first knowing exactly 
> why you need Posix compliance. It is also worth noting that porting an 
> application from one fully compliant OS to another is not always easier 
> than porting from that OS to a non compliant one. Quite a lot of 
> problems can arise in slightly different interpretations of the norm, 
> and quite a lot of assumption that are correct under one system will 
> require carefull tweaking and lib binding in another.
> Another thing that is worth noting is that Posix norming system is 
> dying, I do not know of one system that has compliance above UNIX03, a 
> norm written in 2001...

A very helpful reply, thanks

-- 
Anton Shterenlikht
Room 2.6, Queen's Building
Mech Eng Dept
Bristol University
University Walk, Bristol BS8 1TR, UK
Tel: +44 (0)117 331 5944
Fax: +44 (0)117 929 4423



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