# OS X is not a true UNIX because of POSIX



## pwharff (Jun 9, 2003)

This weekend I got to speak to an old friend who knows a great deal about UNIX.  We started to talk about OS X and he tells me "OS X is not a true UNIX because OS X doesn't support POSIX".  He went on to tell me that OS X is "UNIX like" according to Apple, but he has yet to provide the link as to where it says this on Apple's site. I was aware that OS X is a UNIX system.  

So, my question is: Is what he is saying true? Is OS X a real UNIX system that supports POSIX?


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## pwharff (Jun 9, 2003)

I'm not sure how this falls into what OS X is?

Acronym for Portable Operating System Interface for UNIX, a set of IEEE and ISO standards that define an interface between programs and operating systems. By designing their programs to conform to POSIX, developers have some assurance that their software can be easily ported to POSIX-compliant operating systems. This includes most varieties of UNIX. 
The POSIX standards are now maintained by an arm of the IEEE called the Portable Applications Standards Committee (PASC).


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## Rhino_G3 (Jun 9, 2003)

POSIX is a standard for the unix based applications.  Most UNIX's aren't 100% truly POSIX compliant.  
OS X is fairly compliant, although not 100%


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## Giaguara (Jun 9, 2003)

Keep this in one thread. 

As long as the Unix stuff can be imported to OS X, i see no problem. If all OS X stuff aren't back-portable to  unix systems, i see no problem either.


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## lurk (Jun 9, 2003)

OS X is not Unix just because Apple has not paid for the moniker to be slapped on it.  If you want to argue from that position Linux is not Unix since there are a couple of issues in there as well but Windows NT is (officially Posix).  Also there are different Posix standards for different areas and they are not all implemented across all Unicies.

I have heard people argue that Solaris was not a true Unix because they put the complier and other stuff under /opt horror of horrors.  Cause we al know that /opt is not posix. 

This whole thing is just like trying to answer how many angels can dance on the head of a pin.

-Eric


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## pwharff (Jun 9, 2003)

Platform Vendors Supporting the Single UNIX Specification


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## Arden (Jun 9, 2003)

> _Originally posted by lurk _
> *This whole thing is just like trying to answer how many angels can dance on the head of a pin.*


42.  Duh!

I don't see how OS X isn't a real version of UNIX, considering that's basically _all_ it is:  BSD with Aqua grafted on top.


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## RacerX (Jun 9, 2003)

All this depends on what _real_ Unix is. Is it an OS based on System V? Is it an OS whose vendor has paid the Open Group for a license to use the term Unix? Is it an OS that can be sued by SCO? Is it an OS that is POSIX compliant? 

Personally, the argument tends to be pointless in all respect excepts one... price. After Apple acquired NeXT, it was selling OPENSTEP for $800. Why? Because of licenses that had to be paid for every copy Apple sold. By the time Apple was selling Rhapsody (Mac OS X Server 1.x.x) it had dropped to about $500. Why? Apple started to replace licensed parts of the OS with open source elements or proprietary elements that Apple developed. Mac OS X is now about $130. As an owner of a number of versions of OPENSTEP, Rhapsody and Mac OS X I am completely happy with the choices Apple made to get the price down. Paying more for saying Mac OS X _is_ UNIX won't make it run any better, only cost more.

I would point out that I also have Apple's _true_ Unix OS, A/UX, which is based on System V (release 2.2). Just because it licensed the ability to be a true Unix (and cost over $800 when it was new) doesn't mean it even holds a candle to Mac OS X of today.

From a strictly legal stand point, after the court battles between AT&T and BSD, it is commonly known that BSD is not considered UNIX by the Open Group. As the lineage of Mac OS X started out with 4.3BSD and 4.4BSD and later implemented aspects of NetBSD and OpenBSD and is now centered on elements ported from FreeBSD, I think it is safe to say that Apple isn't looking to spend the time or the money needed to try to fight the tide to get the Open Groups expensive label of _UNIX_ applied.

Besides, SCO has made the question of Unix somewhat dangerous these days (not for BSD based systems as there was a settlement that ended the rights of the holder of AT&T's Unix, who ever that is, to sue BSD). IBM, Sun and HP have been paying a number of _holders_ of the term UNIX for years, only to find out (in the case of IBM) that they can be dropped at the whim of any of them. 

Also POSIX has been somewhat out of the picture on the UNIX front for a few years now (though I thought it was a good idea... while it lasted).


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## Eckhart (Jun 10, 2003)

BSD(i) (plus all its derivates) are not Unix,
GNU is not Unix (that makes nearly 200 Linux Distros not Unix along the way),
Mac OSX is not Unix,
and now -- WOW -- IBM's OS/390, AIX, IRIX, SCO and Solaris are!! What a deal!

IBM's OS/390 is out of the race, AIX & IRIX are "staring at open graves" their vendors (IBM & SGI) have apparently changed their mind about them. And now there is this Open Group with a zilion reglementations about a zilion dead or dying projects. And there is SCO that desperatly tries to get any advantage out of their Unix license... This is getting grotesque. I find Solaris to be the only serious Unix(TM) system nowadays.

It's funny. I have bearly used anything of what is legally called a Unix(TM) system. Yet I have a clear notion of what "Unix" is. So, let us not care to much about a label. Mac OSX is "Mac OSX" -- yet so obviously built upon unix like technology, that you might called it a unix, if you want to...

I always refer to FreeBSD as a very clean and good example of what is unix (and indeed FreeBSD is pretty "unix", far more than Linux), although by license it is not. Yet a license does not define the OS, technology is what counts. And on that field, I refer to unix as to system that boots up a kernel, connects physical hardware to devices or mountpoints on my fs, handles multi-threading (SMP today aswell), cares about POSIX (libraries, headers that make porting from similar systems fairly easy, plus a gcc compiler to my hand) and at last gives me a shell user interface. Besides distinct applications/features also shaped my definition of a unix system: a certain directory structure, a set of standard binaries, transparent networking interfaces, udp, nfs, unix domain sockets, ascii configuration, login, passwd, ssh (telnet, rsh earlier) and much more...

You can complete or extensify this list and see that most will still apply to Mac OSX.

One last word:  I once had to setup a webserver (apache/mod_ssl/mod_perl) plus quotas and a bunch of ther stuff on a Solaris machine. Coming from what I considered unix, this was pure horror. I never returned to Solaris afterwards and sweared to continue using a "real" unix


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## Randman (Jun 10, 2003)

Pardon my ignorance on this subject, but does it really matter if it OS X is Unix, or just Unix-like??


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## symphonix (Jun 10, 2003)

Since the release of version 10.2, Mac OS X is supposed to be much more compliant with the POSIX standard, and as I understand it OS X is not far off being fully compliant. 

http://www.apple.com/macosx/jaguar/unix.html


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## Eckhart (Jun 10, 2003)

Both of what you (Randman|symphonix) said, is roughly what I also wanted to express. I do agree.

Btw, the sentence "iSync, therefore I am" really does appeal to my sense of humor. Quite creative - send it to Apple - they should put that into one of there commercials. ;D

Ok, I see, now we're finally heading off topic...


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## ApeintheShell (Jun 10, 2003)

are you talking about UNIX, unix, Unix, UnIx, or uNiX?

my OS selection is case sensitive


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## btoneill (Jun 11, 2003)

> _Originally posted by pwharff _
> *
> So, my question is: Is what he is saying true? Is OS X a real UNIX system that supports POSIX? *



He is completely and totally wrong, but for different reasons. He is right that OS X is not a true "UNIX", it's UNIX-like. But he's wrong for saying the fact that it's not a true UNIX is because it doesn't support POSIX. First, lets look at POSIX...

POSIX is "The Portable Operating System Interface". POSIX is also not a single standard, there are many many different POSIX standards ranging from C API's to the requirements for how a shell should work. There are currently around100 different POSIX specifications. So, which of the 100 POSIX specs is he talking about? 

Now, on to what it takes to be a UNIX, in order to call yourself a UNIX you must first pass a series of requirements. These requirements are set by "The Open Group" (http://www.opengroup.org). There are serveral different UNIX stardards, such as UNIX95 and UNIX98, which each have different requirements. Some of the requirements may be to meets some specific POSIX specifications, but thats not the onlyrequirement. Ofcourse, once you meet the requirements, you then have to pay the Open Group to use the UNIX name.

As to him knowing a "great deal" about UNIX, that is up in the air. It's clear he knows some buzz words and has half-read some articles about being called a UNIX, but anyone can regurgitate arguments that pop up on message boards all the time. The question to ask him would be: "Ok, name some OS's that are true UNIX OS's" I wouldn't be surprised if he lists Net/Free/OpenBSD as being a true UNIX, or BSD/OS. If he mentions AIX, ask him what versions of AIX. If he mentions linux, laugh at him and call him a twit, then laugh some more.

Brian


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## btoneill (Jun 11, 2003)

> _Originally posted by Randman _
> *Pardon my ignorance on this subject, but does it really matter if it OS X is Unix, or just Unix-like??  *



To most people it doesn't, but to people who want to try to flaunt their supposed knowledge of UNIX to make people think they are God's gift to computers by bringing up stupid arguements that no one really cares about, and that don't matter, but they think you will think it does because they sound "knowledgeable" it is important. It's people like him who give UNIX a bad name, and why so many people run away in fear the minute they hear "UNIX" in a conversation. 

Brian

PS: My OS is better then your OS, my Editor is better then your Editor, and your shell sucks.


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## Arden (Jun 12, 2003)

Hitler.  There, now this thread's dead. ::ha::


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## tony (Jun 13, 2003)

As an OS developer who has worked on POSIX compliance for a couple of UNIX OS's, there are a couple things I'd like to clearify.

- The cost of licensing is not a big issue.  The Open Group doesn't charge a lot for UNIX branding or licensing.  The real cost of becoming POSIX compliant is all of the developer hours that have to be spent making the system compliant, running test suites, and jumping through the endless bureaucratic hoops that are required by the Open Group.

- The main reason that companies are willing to do this is that there are contracts that require various levels of UNIX branding to even be allowed to bid on them.  I think this is especially true sometimes of government contracts.

- The vast majority of us have no reason to care whether OSX is UNIX, or only UNIX-like.


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## btoneill (Jun 13, 2003)

> _Originally posted by arden _
> *Hitler.  There, now this thread's dead. ::ha:: *



"No no he's not dead, he's, he's restin'"

Brian


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## Arden (Jun 13, 2003)

It's something like Godsford's Law (can someone please verify this?) that states that as soon as someone mentions Hitler or the Nazis, a thread on a forum is immediately dead.  So I killed this thread. ::ha::


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## Rhino_G3 (Jun 16, 2003)

> _Originally posted by btoneill _
> *...If he mentions linux, laugh at him and call him a twit, then laugh some more.
> 
> Brian *



For some reason this struck me as extremely funny today... I think I just need to get out more


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## asr (Jun 17, 2003)

> _Originally posted by arden _
> *It's something like Godsford's Law (can someone please verify this?) that states that as soon as someone mentions Hitler or the Nazis, a thread on a forum is immediately dead.  So I killed this thread. ::ha:: *



Sorry to delurk on an irrelevancy.

It's Godwin's Law.  And I think it technically only applies on Usenet.

But it still seems appropriate in this thread for some reason.

Asr
-- 
Wannabe future Mac user


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## adambyte (Jun 17, 2003)

Yeah... it seems like asking "What is true UNIX?" is kind of like asking "What is true faith/belief/religion?" The term has a basic core that most people can agree on, but it's all very relative.

Anyway, as long as my computer knows to sleep when it's closed, turn on when it's open, use my extra "mega-widescreen" pixels, and make use of devices as soon as they're plugged in, I don't give a crap what's under the hood. As long as it's a "true Mac," that's good for me.

Ha! I brought up the phrase "true Mac." Now we can argue about what THAT means. heheh.


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## Arden (Jun 17, 2003)

*true Mac*: _n._ a computer that runs any version of the Macintosh Operating System anywhere from 1.0 to 10.2.6.

There, that was easy!


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## wiz (Jun 18, 2003)

> _Originally posted by ApeintheShell _
> *are you talking about UNIX, unix, Unix, UnIx, or uNiX?
> 
> my OS selection is case sensitive *




LOL


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## Arden (Jun 18, 2003)

I think symphonix is a type of UNIX because his name ends in "-nix."  This is unconfirmed to date.


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## Sogni (Jun 18, 2003)

> _Originally posted by adambyte _
> *Yeah... it seems like asking "What is true UNIX?" *



What is The Matrix?


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## Arden (Jun 18, 2003)

That's definable.  The Matrix is a computer program designed by machines to control the collective consciousness of the human race as their bodies are used as an energy source.


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## Lycander (Jun 29, 2003)

> _I don't see how OS X isn't a real version of UNIX, considering that's basically all it is:  BSD with Aqua grafted on top. [/B]_


_
Not quite. Underneath Aqua is Darwin, not FreeBSD. Darwin borrows some BSD code but at the heart of Darwin is the Mach kernel. Mach was suppose to be a microkernel that depended on application servers to provide the rest of the OS functionality rather than squish it all in one fat monolithic binary. But... quote taken from http://www.wikipedia.org/wiki/Mach_kernel

Mach is not an operating system on its own, and is largely unusable without a set of servers - and those servers did not exist. In order to get some sort of usable system up and running, the Mach authors ported BSD onto the Mach kernel in a quick-and-dirty fashion: instead of breaking down BSD into parts and building each of them as a server, they simply compiled the entire kernel into one server and ran it. The result was known as POE.

Like most people have said in prior posts, even *BSD has strayed from true Unix, and Darwin is yet another step astray. But the Apple doesn't fall far from the tree, so they say _


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## Arden (Jun 29, 2003)

Good to know...


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## TommyWillB (Jun 29, 2003)

> _Originally posted by symphonix _
> *Since the release of version 10.2, Mac OS X is supposed to be much more compliant with the POSIX standard, and as I understand it OS X is not far off being fully compliant.
> 
> http://www.apple.com/macosx/jaguar/unix.html *


I can't help but noticing that this page never says OS X is Unix... It always says "Unix-based"...


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## TommyWillB (Jun 29, 2003)

> _Originally posted by arden _
> *true Mac: n. a computer that runs any version of the Macintosh Operating System anywhere from 1.0 to 10.2.6.
> 
> There, that was easy! *


I've never heard of the "Macintosh Operating System"...

Who makes that?


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## Lycander (Jun 29, 2003)

"Macintosh Operating System" me thinks is just a long way of spelling out MacOS. Don't know what they called it back in the days. But starting with OSX they should change the spelling to Machintosh


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## TommyWillB (Jun 30, 2003)

What they called it (them actually) back in the day:
http://www.theapplemuseum.com/index.php?id=tam&page=timeline&subpage=os


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## bracken (Jul 4, 2003)

> _Originally posted by pwharff _
> *We started to talk about OS X and he tells me "OS X is not a true UNIX because OS X doesn't support POSIX".  *



Windows 2000 is POSIX compliant, so is it a true UNIX?


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## griz (Jul 16, 2003)

I don't know, but I'd put my vote on Balmer & Gates as a couple of Unix.


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## Arden (Jul 16, 2003)

UNIX == Eunuchs... who knew?

Developers, developers, dev... oh, sorry.


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