Apple macOS 15 Sequoia is officially UNIX. If anyone cares...

Apple's latest OS release is the newest member of the Open Group list of officially verified UNIX variants – by quite some margin. Apple macOS 15 Sequoia appeared in mid-September and is an official, compliant version of UNIX™, but that may not mean exactly what you think. For instance, macOS does not use any AT&T source code …

[Peter Gathercole]

POSIX and UNIX

The original POSIX 1003.1 was essentially the same as the UNIX System V Interface Definition (SVID), Issue 2 published by AT&T around 1986. This was effectively the definition for System V release 3 (SVR3), although I think that it may have included stuff that appeared in SVR3.2. The last version of the SVID was issue 4, that was updated to conform to one of the slightly later versions of POSIX 1003.1, maintaining compatibility between the core genetic UNIX and POSIX.

I attended the SVR4 Developer conference in around 1988, and as part of the bundle of bumph given out, it included a copy of this issue of the SVID, which is still sitting on a shelf in one of my bookcases. I was told that I would get a copy of Issue 3 sent to me (which was updated for SVR4), but it never arrived.

The SVID (and hence the first edition of POSIX 1003.1) defined more than just the command set. It also defines a mandatory set of system calls, (essentially Chapter 2 in the UNIX manual) but does not describe any of the other sections, like the C library or device types.

POSIX 1003.1 has evolved quite a lot since then, and the various UNIX standards now maintained by The Open Group have taken over the maintenance of the UNIX brand, merging POSIX with the other UNIX branding.

I know why, but it's a shame that Linux as a community (whatever that is) has not bought into the standards promoted by The Open Group, or have not set up a similar single branding standard (forget the Linux Standard Base - it's dead), because variation between different Linux distributions are one of the reason why we see fragmentation of the Linux ecosystem.

[steelpillow]

Re: POSIX and UNIX

I do recall a flame war once in which Linux broke from POSIX compliance when Linus declared that POSIX was a broken standard and he had no intention of breaking Linux.

As for whether Linux is or is not a UNIX, do I detect a slight change of heart? ;o)

[Anonymous Coward]

Re: POSIX and UNIX

To be fair, the deltas are small(ish) and well documented.

I suspect at some point IBM will go to the OpenGroup and tell them that Linux is UNIX. One way or another the standards will line up with Linux's implementation. "GNU's Now Unix"?

[steelpillow]

Re: POSIX and UNIX

One distro has been Unix certfied. Presumably it incorporates pax and those other deltas in the build.

Might be easier, cheaper and more practicable for IBM to do the same with RHEL. But hey, let's not forget the wrong-footed monopoly plays.

[alrferreira]

Re: POSIX e UNIX

Linux = Linux Is Not UniX :-)

[Lars]

Re: POSIX and UNIX

Unix is more or less just a trademark and to use it you will have to pay somebody something. I don't think the Linux lot, who ever they are, give a shit or that anybody is demanding it,

[Peter Gathercole]

Re: POSIX and UNIX

UNIX is a trademark, and is protected as such. The cost is running the certification tests and registering the results. The use of the trademark is conditional on passing the verification suite.

It's been this way for several decades. As Liam pointed out in the original article, being able to use UNIX as part of the description or name of an OS is not conditional on having code from the original AT&T releases (Bell Labs Edition 7 was open-sourced, so doesn't really count when it comes to UNIX branding).

People may have noticed that I tend to use the term "Genetic UNIX" for OS systems that can trace their lineage back to System V, which is where the verification suites started.

UNIX-like OS's that don't have branding can probably trace much of their history through to BSD, which had to remove AT&T code during the dispute of the 70's, 80's and 90's which led to BSD 4.4Lite2, which was not only free of AT&T disputed code, but also available under a very permissive license.

The GNU part of GNU/Linux took a lot of stuff from BSD, and further developed it.

[Anonymous Coward]

Am I missing something?

MacOS has been UNIX certified for many years. At least since 10.11, El Capitan in 2015. Is this a different level of UNIX certification or just a slow news day?

[Peter Gathercole]

Re: Am I missing something?

Apple have separately listed Sequoia for Apple Silicon as a separate entry, even if the OS is ostensibly the same.

I don't know why they've done this specifically for their ARM based systems, unless the port involved a significant re-write of some of the main parts, but I guess they may be trying to differentiate the product lines for the future, although I don't see Apple selling any more Intel based Macs.

[Dan 55]

Re: Am I missing something?

They probably suddenly realised they had discontinued their last Intel machine a year ago (Mac Pro 2019) and won't renew the Intel certification.

[geoff61]

Re: Am I missing something?

UNIX certifications are for a specific OS on a specific hardware platform. Apple have had separate Intel and ARM certifications for every macOS release since 2020 (Big Sur). Back in the day, Solaris had separate SPARC and Intel certifications.

[ThomH]

Re: Am I missing something?

Potentially interesting for those who haven't encountered it before: this is the story of why and how OS X became UNIX certified by its primary architect.

Short version: Apple was calling it a UNIX despite not being certified. The Open Group filed a $200m lawsuit. One of Apple's tech leads was therefore paid $10m (!) to satisfy certification requirements within a year, of which he describes rewriting the kernel's internal signalling mechanism as the biggest chunk.

Nice work if you can get it.

[Peter Gathercole]

The UNIX brand

There are now very few companies that are really interested in UNIX as a brand. The only company that I know about that is still developing a UNIX system (apart from this addition from Apple) is IBM, and AIX appears to be the only certified UNX V7 compliant system (this announcement by Apple is basically saying that Apple Silicon MacOS is the same as their Intel products, and is only UNIX 03 branding). I don't expect any other company to put a product up for certification.

I can't imagine that there ae enough companies interested to keep the brand evolving. I think that even IBM will lose interest as their interest in AIX wanes, and they deprecate it in favour of RedHat Linux on Power.

[Dan 55]

Re: The UNIX brand

I wonder why IBM bothered to certify AIX 7.2 TL5 as a UNIX V7 in 2020, when UNIX V7 is ancient (1979). The previous versions of AIX, including AIX 7.1, are all certified as UNIX 03.

Unless they somehow managed to fail a test for compliance with UNIX 03?

[Peter Gathercole]

Re: The UNIX brand

No. You've missed some of the more recent subtleties over the UNIX brand.

UNIX V7 is the latest in the UNIX branding sequence, superseding the UNIX 03 standard (See https://www.opengroup.org/openbrand/register/catalog.htm).

It is NOT the version of UNIX from 1979. It is confusing, but I actually went back into a lot of ancient documentation when The Open Group first published their UNX V7 standard, and UNIX circa 1979 was actually called UNIX Edition 7 in almost all of the documentation published with that release, after Edition 7 of the UNIX manual,

I used to use UNIX Version 7 as an identifier for the 1979 release right up until the UNIX V7 standard was released, when I switched to calling it Edition 7, just to make sure there was no confusion about what I was saying. But it is notable that TUHS has got various branches of the source code labeled as V7, so I don't think I was alone in using that nomenclature.

I can't imagine what you would have to break in a modern UNIX to make it deemed as only UNIX Edition 7 compatible. Although things are recognisably similar, System 3 and System 5 added many, many more commands and features, and tried to regularize some of the options syntax. Using an Edition 7 system (in emulation, or using the i386 port that was done after SCO opened it up to a very permissive license) reminds one of just how primitive the systems we used to use were (I first used UNIX Edition 6 on a PDP11/34e in 1978 when I went to Uni,). No networking other than what you could run over serial lines, no graphical interfaces, not even Curses terminal handling, and a whole lot of things we take for granted (like vi) just not being present at all!

Strangely, usine a FreeBSD system recently reminded me (because of the syntax of some of the commands like "ps") that BSD systems are actually derrived from UNIX Edition 7, not UNIX System III or V.

[Dan 55]

Re: The UNIX brand

Thanks, I didn't realise. It seems an odd choice to they break with convention and call UNIX V7 instead of UNIX 16. I may even have seen UNIX V7 mentioned in the past and assumed it was referring to the 1979 version.

[stiine]

Re: The UNIX brand

At least they didn't calling it Unix 2024...

[Doctor Syntax]

Re: The UNIX brand

"There are now very few companies that are really interested in UNIX as a brand."

The plot was lost about 30 years ago, sad to say.

[Dan 55]

POSIX.1 vs POSIX.2

The POSIX.1 specification is all about C, it contains C header definitions and the C library specification. As does the 2004 revision, the 2017 revision, the 2024 revision...

POSIX.2 is for the command interpreter, shell, user environment, and related utilities.

If a system is not UNIX-like and not written in C and doesn't offer a C-like API and ABI, it's going to have a hard time being compliant with the POSIX.1 specification so it can't be a certified UNIX.

[1947293]

Re: POSIX.1 vs POSIX.2

You can provide C header files without implementing the functionality in C.

[Dan 55]

Re: POSIX.1 vs POSIX.2

You could, but it wouldn't be POSIX.1 compliant.

[jotheberlock]

Re: POSIX.1 vs POSIX.2

Why? I mean chunks of OS X are written in C++. Why would e.g. a C++ implementation of libc with a C wrapper around it not be POSX.1 compliant?

[Dan 55]

Re: POSIX.1 vs POSIX.2

Poster above said just provide the header files. Not the same as what you're saying.

[IvyKing]

Re: POSIX.1 vs POSIX.2

I don't think it really matters for POSIX compliance in what language was used for writing the code to implement the OS. What does matter is that the OS have a C compiler that will compile POSIX compatible C code successfully and that the resulting binary does what it is expected to do.

[Roland6]

Re: POSIX.1 vs POSIX.2

Yes POSIX was all about facilitating source code portability. We need to remember that back then, there was no industry standard cpu and machine architecture, plus “Unix” want a uniform standard.

The intent was thus to facilitate application source code portability: write your code to use POSIX APIs etc. and you should be able to successfully compile and run it on any POSIX compliant system.

Back in the late 1980s and early 1990s, you could miss out on contract because your system wasn’t in say Oracles priority list for porting.

Obviously, the rise of the x86 Wintel platform, brought a new level of standardisation enabling binary standardisation.

Linux has followed Wintel, but as we are seeing with the different package managers etc. you can not simply take any Linux binary and install/run it on your Linux system, you have to check compatibility, likewise Linux developers will only say their distribution has been tested on a limited number of Linux distributions…

[geoff61]

Re: POSIX.1 vs POSIX.2

POSIX.2 was merged into POSIX.1 in 2001. If you poke around in those links to the 2004, 2017, and 2024 revisions you'll find the shell and utilities stuff is in there.

[Skiver]

Saying the DEC OSF/1 was later marketed as Tru64 UNIX is a bit reductive. That latter was based on OSF/1, but it was a full featured commerical OS release. DEC OSF/1, the product, was mainly used on workstations. DEC sold MIPS based workstations running DEC OSF/1. Tru64 ran on Alpha and was either ported or was in the process of being ported to IA64 when HP pulled the plug on the Tru64 project.

I worked at DEC and made it through the Compaq and HP acquisitions, but sadly did not survive the end of Tru64 UNIX>

[Peter Gathercole]

OSF/1 was supposed to be a standard version of UNIX, in opposition to SVR4, created by UNIX vendors who either didn't want to take part, or were excluded from the SVR4 initiative that was being driven by AT&T, Sun, Amdahl, ICL, SCO (the original one) and several other UNIX system vendors of the time.

But the list of those excluded was mainly IBM, HP and DEC, and these three decided to set up this competing standard, for whatever reason they thought it was justified (I think they just wanted to muddy the waters and protect their own proprietary UNIX offerings).

Initially, IBM offered the kernel they were writing for AIX Version 3 (which was being written at the time for the upcoming RS/6000 line of systems), and they also contributed an early cut of their Logical Volume Manager. I don't remember which of the other parts came from HP or DEC.

The intention was to try to make a standardized version of UNIX that was not SVR4,

But it was interesting to note that it was only DEC that actually produced systems that ran a version of OSF/1. HP adopted some of the features back into HP/UX, and of course IBM went forward with AIX 3.1 and later, which was not compliant with OSF/1.

It is now somewhat ironic that IBM is the last player standing, after bringing AIX up to the POSIX 1003 standards, and effectively adopting the features to allow it to become System V compliant (AIX was already SVR2 compliant, IBM having a source code license for that version from earlier UNIX products) but adding the SVR3 and 4 features to comply with the later POSIX and SUS standards.

[Anonymous Coward]

I always thought Mac OS was a skin over BSD

EOF

[Handy Plough]

Re: I always thought Mac OS was a skin over BSD

If you look into the design of NeXTSTEP, it's was extremely advanced for its time. To be fair, even by modern standards, it still stands up. As Liam points out, the kernel is a hybrid of MACH and 386BSD, and the networking stack is BSD, much like Windows and Linux too (happy to be stood corrected on that on). Most of what was NeXTSTEP can still be found in modern macOS. Avie Tevanian and Bertrand Serlet are very clever chaps indeed...

[david 12]

Re: I always thought Mac OS was a skin over BSD

networking stack is BSD, much like Windows

When MS adopted unix networking is around the same time that 'unix' stopped being equivalent to "unix networking" in many minds. I can remember a well-known unix source saying something like "I've tried NT4, and it /is/ unix.", and he wasn't the only one: in the late 90's, unix networking was the killer app of unix systems.

[Anonymous Coward]

Re: I always thought Mac OS was a skin over BSD

FreeBSD has always been good at networking* but the rise of IPv6 gave it a real push. The KAME project developed probably the world's first fully dual stack (IPv4+IPv6) networking stack. And because it was for FreeBSD the code was released under the permissive BSD license so other operating systems could take the work and integrate it. That's how FreeBSD's networking stack ended up in Windows, you could even see it in the acknowledgements section.

It's been over 15 years since I did anything with Windows, so things may have moved on since and MS may have written their own stack in the mean time, but that was quite remarkable at the time.

^{* It's why Netflix uses FreeBSD for its global caching infrastructure and many firewall appliances run a version of FreeBSD}

[Anonymous Coward]

But Toronto sucks

Concurrent Euclid -- now that's a sexy name for a programming language! But Toronto (even University of) ... pfffrrrrrttttt! (and TUNIS with it, obviously). Naahhh, the only true OS for Canada in the 70s and 80s was McGill's (university) MUSIC A and B, the Multi-User System for Interactive Computing! Properly baked in Montréal, intellectual pinnacle acme of the canucks! And yes, written in IBM/370 assembler and FORTRAN ... my-oh-my, THOSE were the days!

[_andrew]

Re: But Toronto sucks

I had the impression that QNX was originally written in Canada. Now there's a properly advanced operating system! Unix-feel, but properly microkernel and also real-time, with network-abstracted device drivers, so you could mount any peripheral from any other QNX system on the network and use it as though it was local.

[Anonymous Coward]

Re: But Toronto sucks

Yeah, it was a great way to exercise the Bionic Beaver! I'd date the OS' fame proper to 1990+ though, with POSIX-compliant QNX 4. That said, it rocks! (and it's from Waterloo, Kanata, and now Ottawa, just 180 km from mtl ...).

[Hi Wreck]

Re: But Toronto sucks

QNX started in Waterloo, ON (just a short drive by distance, but it takes forever on the infamous 401). It was inspired by Thoth (more correctly called Sloth). David Cheriton (who's he?) helped write that. Good times!

[ssokolow]

Re: But Toronto sucks

See also:

DOS/4GW (of DOS gaming fame) = "DOS/4G, Watcom Bundle Edition" → Watcom C/C++ → University of Waterloo.

(Basically, so many big-name DOS games showed that DOS/4GW banner because Watcom C/C++ struck a deal with Tenberry Software to include a limited-but-good-enough build of their DOS/4G extender with the compiler without the usual "the same as the whole compiler, paid again" license fee that was standard for commercial use of DPMI extenders at the time, and Watcom C/C++ was a product of Waterloo, Ontario, founded by former UWaterloo people.)

Heck, when Mr. Tenberry Software died a few years ago, he was in the middle of digging through his old floppies trying to find a newer version of DOS/4GW Professional (the paid-for upgrade with limitations removed) to donate to the Open Watcom C/C++ v2 project. Open Watcom is also what was used for the DOS and Windows 3.1 prototype builds of Retro City Rampage that buyers of the game get, so the ripples of UWaterloo continue.

[45RPM]

Hands on the table, I’m pissed. I’ve been drinking since lunch time - so what I say next should be considered in the light of excessive alcohol intake. And not just beer either. Beer. Wine. More beer. Rum. Probably some other drinks I’ve forgotten. But it’s Friday - and what else is POETS day for?

But I digress. Apple (weird. I don’t think I drank any cider or brandy. Remiss? Or forgetful?) is being criticised here for complying with standards. Often it gets criticised for, apparently, not complying with some (often imaginary) standard. Can they get a break?

As a software developer it seems to me that both Apple OSes and Linux based OSes (including those from Google) are scrupulously standards compliant - and hence easy to switch to and from.

The lock in is with Windows. I’m not even saying that’s a bad thing either (pissed, remember? All is good with the world!) If windows works for you then more power to your elbow. Enjoy. Just don’t bitch about some imaginary Apple lock in. ‘Cos it’s just that - imaginary.

But, speaking of lock in, I think there might be some spirits that I haven’t drink yet. Chin chin!

[david 12]

The lock in is with Windows.

Windows NT was POSIX compliant for a while. Then POSIX went in one direction (POSIX ain't done till Windows won't run), and MS went in another: SFU was eventually replaced with a virtualized linux kernel, because users wanted linux compatibility rather than POSIX compatibility.

I infer from this article that the "unix" brand name (user land) has recently been merged with the "POSIX" brand name (API). the unix community has changed, and now very few people compile the Open Source for whatever POSIX applications they happen to be using.

[Bela Lubkin]

I infer from this article that the "unix" brand name (user land) has recently been merged with the "POSIX" brand name (API)

True, if by 'recently' you mean '20+ years ago'...

[Peter da Silva]

UNIX is any operating system based on the core system calls that made up v6 or v7 unix in the late '70s. That's the last time there was one UNIX. The tree of UNIX has spread since then, with grafts and new plantings and runners and seedlings and all the agricultural metaphors you could want. But that's where it starts. open close read write pipe fork exec stat ....

[Peter Gathercole]

I understand what you're saying, but even back in the Edition 6 and Edition 7 days, there was a lot of variation, and copious numbers of additions to the base versions as people wrote interesting things that they wanted to share, resulting almost in no two UNIX systems working quite the same. I came across the Calgary mods. the Keele mods, and of course the BSD add-on tapes for both Edition 6 and Edition 7.

Inside Bell Labs., there were tweaked versions of UNIX being used all over the place. It was almost the case that there were as many bespoke versions as there were groups wanting to use it. There was the internal Research UNIX branches, several of them, and then if you look at System III (which came from the commercial arm of AT&T in Columbus, not Murray Hill where UNIX started), it actually comes from the Programmers Work Bench (PWB) which was itself a branch of Edition 6, not Edition 7.

BSD was mostly built on Edition 7 as a base, but there was a lot of cross pollination between the different strands.

There was a lot added to transition from Edition 6 to Edition 7, and inside AT&T, this continued with Edition 8 which was not really seen outside of AT&T, and I believe Editions 9 and 10, before the main movers transitioned to Plan 9.

[Anonymous Coward]

You may think this is silly, but it isn't easy to do.

As one who was involved in the certification of MacOS 10.13 (High Sierram it WAS a while ago) this is a long process. You need to run a VERY complex set of programs and get the proper results. Some things are are truly strange in the test suite. It checks for proper and improper ways of doing things, then checks results of programs that call library routines. One particular bad problem was related to a compiler bug that cropped up in testing the tgama function. It wasn't pretty. If things don't go as expected, you can apply for exceptions and sometimes they are rejected (or accepted, it depends). All in all NOT an easy task.

One of the "benefits" of this is that some government can specify "Unix computers", and only those that are certified will get to do the bid. A pretty crafty marketing ploy if you ask me.

[Old Used Programmer]

Looking in odd places...

After reading the article, I just HAD to check... RPiOS 12 (Bookworm) 64 bit on a Pi5 does NOT include pax, by default. But it's available for install from the repositories (apt-cache search finds it).

[geoff61]

Re: Looking in odd places...

The output of "apt-cache show pax" includes: "This is the MirBSD paxtar implementation supporting the formats ar, bcpio, cpio, SVR4 cpio with and without CRC, old tar, and ustar, but not the format known as pax yet."

It likely conforms to POSIX.2-1992 but since it doesn't support the new "pax" format (i.e. "-x pax" in addition to the old "-x ustar" and "-x cpio") it doesn't conform to the later POSIX revisions and wouldn't be sufficient for a UNIX 03 certification.

[PRR]

...macOS does not use any AT&T source code –

So it is homeopathy? The active substance is repeatedly diluted until "...not even a single molecule of the original substance can be expected to remain in the product" and that is what makes it powerful?

[Bluck Mutter]

Sequoia Unix... The song remains the same

Being an old Unix head, starting 1981, I well remember the REAL Sequoia Unix system from the mid 80's.

https://dl.acm.org/doi/pdf/10.5555/327010.327218

https://pages.cs.wisc.edu/~david/papers/ieeecomputer1988_sequoia.pdf

To quote the second article:

"Sequoia has implemented its own proprietary kernel that offers a superset of the functionality of Unix System v"

Obviously being fault tolerant it needed to add stuff to Unix to support this.

Bluck

[Anonymous Coward]

I am going to assume the motivation for the bother of certification was to be able to sell said product into certain environments that specify it as a requirement. No doubt in some gov standards for procuring certain kinds of systems.

The relevance of it to even a technical audience is otherwise, debatable.

[naive]

It could also be Apple is courting software builders who have developed software for Posix compliant systems, to port their solutions to Apple systems, since the Posix compatibility indicates source code might compile without too many changes on Apple systems.

After all, Apple builds really good hardware, why not lift all the walled garden Mystique surrounding Apple systems, and tell the world: Hey guys if you are not a M$ sheeple, it will run on our stuff too !

[distinctmouse]

But what's the benefit of obtaining a Unix certification? Most linux distros dont have it but are still used everywhere. Thoughts?

[Handy Plough]

They (Apple) used the name UNIX in marketing for Tiger(?). The Open Group were displeased and sued. Apple decided to certify as it was cheaper than litigation or buying The Open Group, and they've certified ever since. It means that Apple can bid on contracts with organisations that require UNIX certification. It's also why Solaris, HP-UX and AIX are all still a thing, even though FOSS alternatives exist. That said, I'm surprised at this stage that SLES, Red Hat and Canonical haven't certified their products yet.

[MrBanana]

But is it though?

Whatever Unix derived underpinnings that Apple claim, the user experience reality of MacOS is just a thick layer of GUI shmoo. Sure, you'll see an /etc/passwd file, and a bunch of other welcoming, standard issue Unix like files. But they are just shiny flimflam that isolates the user from the engorged, shoddy, mess that Apple have applied in spades over the top. And only getting worse as they dumb down MacOS to be on a collision course with a mobile phone app.

[Handy Plough]

Re: But is it though?

Well, it clearly passed the Open Groups test suite and met their requirements, so yeah, it is.

[Anonymous Coward]

does this mean that Apple users will require a cravat and open toed sandals? The pony tail is common to both groups.

[brennan]

Nice article

Nice article, thank you

[jdzions]

Almost everything the main article had to say about POSIX is incorrect, to a moderate to immense degree.

I held multiple committee chair positions within IEEE-CS TCOS, the standards body which produced the POSIX family of standards, between 1988 and 1998. I wrote text, balloted on text, and chaired the management subcommittee that authorized projects under P1003. I was in the room when it happened. I know where the bodies are buried because I helped put many of them in the ground.

Take every mention of POSIX in the article (and in most of the comments) with a mountain of salt. Among other things: there are three programming language bindings to the POSIX base system APIs (C in 1003.1, Fortran in 1003.9, Ada in 1003.5). Shell and utilities were standardized in 1003.2 (not POSIX.1-anything). The rest of the article and comments are just as wrong in so many other ways...

Jason Zions

Past chair P1003.8, TCOS SEC PMC

[geoff61]

Jason, you're a little out of touch. There *were* three language bindings, but 1003.9 was withdrawn in 2003 according to https://standards.ieee.org/ieee/1003.9/1440/ and although 1003.5 doesn't seem to have been withdrawn, I can't find anything more recent than "Amendment 2", published 31 Dec 1999 (https://ieeexplore.ieee.org/document/815314) and that had Ada bindings to the ancient 1003.1-1996 C interfaces, three major revisions behind the current 1003.1-2024 standard, so it's questionable whether it is relevant any more. Also, although the shell and utilities *were* standardized in 1003.2-1992, 1003.2 was merged into 1003.1 in 2001, as I pointed out in an earlier comment.

(Note that I don't count 1003.1-2017 as a major revision, as it was just 1003.1-2008 with its two technical corrigenda rolled in. The reason it was produced is because IEEE rules require standards to be either revised or withdrawn after 10 years, which means that the IEEE website not showing the 1999 amendment to 1003.5 as withdrawn may be a mistake.)

Geoff Clare

Current Technical Editor of POSIX.1 and The Single UNIX Specification.

[Anonymous Coward]

No support for POSIX message queues in macOS

Last time I checked, macOS doesn't support posix message queues, only Sys V message queues. I guess that is not a requirement for POSIX compliance?

[geoff61]

Re: No support for POSIX message queues in macOS

Yes, POSIX calls it "the Message Passing option". It's one of a long list of options whose support can be queried via constants in <unistd.h> and calls to sysconf(). Some of the POSIX options are mandated for UNIX conformance, but Message Passing isn't one of those.

[Anal Leakage]

El Rag cares

… enough to make it click bait. Face it Reg, you just can’t quit Apple.