De facto or de jure? Linux isn't technically one, sure, but given that Linux is where the OS hot-shit is now (e.g. eBPF, although I think FreeBSD has the basics - no idea whether it got merged but I saw a student project) is it not fair to say it's where Unix would've been had things been different?

Both, I would say, particularly with the GNU’s Not UNIX userland. I don’t think it matters much, though, as you can have a great non-UNIX OS, which Linux definitely is.

Also, we might forget it now, but in the past there were a lot of UNIX that were quite different in small and large ways. The differences between Linux and Darwin might be as great as the differences between SunOS and Xenix, or indeed NeXTSTEP, back in the day. Or maybe not, that was before my time, but my point is that UNIX was not a monolith and there were incompatibilities and different ways of doing things. So I guess yeah, Linux might be what one of these might have become.

I just find it ironic that so many people are keen to compare macOS to UNIX and just assume that macOS has to be the weird outsider, even though the reverse is actually true. The same people also often assume Linux-isms are the way UNIX works, like the now-dead comment about macOS’ commands not supporting GNU options.

Outside of macOS, commercial Unix is basically dead. In the old days I used to see all sorts of systems. One company had Solaris 2.x, SunOS 4.x, Digital Unix, HPUX, AIX. Now you rarely see anything other than Linux, though I still know a couple of AIX shops that went all in on IBM hardware and still swear by it.

Like it or not, right or wrong, when people say "Unix" today, they mean Linux with GNU userland.

The IBM mainframe operating system z/OS (formerly known as MVS) is a certified UNIX 95. (That's an older UNIX standard, but still valid.)

There are still a lot of IBM mainframes out there. Far less than there used to be, but IBM mainframes remain (even in 2020) a sector with many billions of dollars of annual revenue (if you add up hardware and software and services across both IBM and the ISV ecosystem). And the vast majority of those mainframes run z/OS. (They also run other operating systems – z/Linux, z/VM, z/VSE and z/TPF – but many of the sites running one of those other operating systems run z/OS as well.)

The UNIX component of z/OS is not merely a compatibility layer, a lot of operating system components and applications now rely on it. For example, the REST-based z/OS management console Zowe that IBM is now promoting runs under z/OS UNIX. My understanding is that IBM prefers (where possible) to develop new OS components and applications to run under z/OS UNIX rather than the traditional z/OS APIs. Anything written in Java (or other newer languages, such as node.js) is running on z/OS UNIX. So even if a z/OS site isn't doing anything directly on UNIX, they are almost certainly using OS components and applications which directly rely on it to function.

Obviously z/OS is absolutely dwarfed by Linux and macOS, but it is probably the healthiest of all the commercial Unixes – Oracle has put Solaris in maintenance mode, same for HPE and HP/UX, HPE killed Digital Unix years ago; AIX is healthier than Solaris or HP/UX, but I think z/OS is even healthier than AIX. z/OS licensing fees are a lot higher than AIX licensing fees, and the non-UNIX parts of z/OS (JCL, VSAM, CICS, IMS, etc) make it far harder to migrate off than AIX is.

Interesting. I had forgotten about z/OS. I don't know much about the mainframe world. Several years back, I did get it booted on the "Hercules" emulator, but making much real use of it was beyond my capabilities.

You just reminded me of this site, which I found incredibly useful back in the day when I was working closely with Solaris, Linux and OSX (as it was then known).

http://bhami.com/rosetta.html

> Linux isn't technically one, sure, but given that Linux is where the OS hot-shit is now (...) is it not fair to say it's where Unix would've been had things been different?

No, it's not fair. Linux is just the OS kernel. UNIX covers interfaces, from APIs to shells and apps distributed by default, which are way out of the scope of Linux. That's the responsibility of Linux distributionsm.

And by the way, there are linux distributions that are certified UNIX

https://unix.stackexchange.com/questions/293396/is-there-a-l...

Moreover, UNIX is standardized. The drive for standardization was derived from the fact that all vendors of UNIX-like OSes were pushing their quirky vendor-specific things. In fact, even within Linux there is no widely established standard regarding basic interfaces, let alone UNIX.

With this in mind, do note that macOS's market share is significantly larger than the aggregate market share of Linux-based UNIX-like distributions.

> And by the way, there are linux distributions that are certified UNIX

How was I not aware of this? Thanks for the link! And you make a very good point regarding kernel vs OS. I assumed Linux == GNU/Linux in this context (so ignoring Android and others), but it certainly is a gross over simplification.

> UNIX

I don't understand why UNIX is such a big deal in 2020. Linux has won, and at least one BSD has binary compatability with Linux. If anything, we should be taking about Linux compliance.

Having no strong package manager story, yet being UNIX compliant, seems like an extremely bizarre priority choice.

> at least one BSD has binary compatability with Linux.

Two BSDs (NetBSD and FreeBSD, no OpenBSD, don't know about Dragonfly), and a handful of Illumos distros (who call the feature LX-branded zones).

> If anything, we should be taking about Linux compliance.

Please no; a standard defined by one implementation isn't a standard.

> Please no; a standard defined by one implementation isn't a standard

Linux has another implementation: WSL 1

Linux has many implementations; some are more complete than others.

There is some value in standards such as UNIX and POSIX compared to whatever the maintainers of a GNU project decided this morning.

As for your second point, it just means that package management is irrelevant to UNIX (or POSIX) compliance. It did not prevent different package managers to appear over the years, because all the expected infrastructure was in place.

> It did not prevent different package managers

But did these UNIX package managers actually materialize? I guess my point is: is UNIX at all relevant? It had some really good ideas that were worth copying, but the world has moved on to greater ideas.

> I guess my point is: is UNIX at all relevant?

Obviously yes. I don't understand what is there so hard to understand.

I mean, just go learn about pretty much any field where you need to target a combination of platforms that don't agree on small arbitrary things, and how much wasted effort that consumes.

I'm still not buying it. We can all agree that UNIX should be relevant but, apart from Mac, when was the last time you used a bona-fide UNIX system?

You've assumed that your perspective is the correct one without justifying it. Sure, standards are important, but UNIX doesn't seem to be a successful (or modern) one.

> I don't understand why UNIX is such a big deal in 2020.

If you're interested in learning about why standards are "such a big deal" then you can start by discovering a phenomenon called linux fragmentation".

30% of Linux fragmentation comes from package managers. 30% of Linux fragmentation comes from the system process. 30% of fragmentation comes from choices concerning default installed packages.

UNIX covers exactly zero of those. If UNIX was worthwhile, we wouldn't have Linux fragmentation or, indeed, an article explaining how to run UNIX scripts on a UNIX-compliant OS (sure as shit ain't a standard if it doesn't actually work).