Alt text:
meme with the 'Always has been' format
Linux, MacOS, OpenBSD and ChromeOS logos on top of the Earth
The first astronaut says 'Wait, it's all Unix?'
A Windows logo, on top of the second astronaut.
The second astronaut says 'Always has been' and points a gun to the first astronaut.
Linux is unix-like, and not from the same family really. ChromeOS is based on linux, so similarly unix-like. Mac is Darwin, which is actually unix. Also all BSDs are unix
Nice to know, I've always thought BSD is actually UNIX.
The BSD variants are descendants of UNIX developed by the University of California at Berkeley, with UNIX source code from Bell Labs. However, the BSD code base has evolved since then, replacing all the AT&T code. Since the BSD variants are not certified as compliant with the Single UNIX Specification, they are referred to as "UNIX-like" rather than "UNIX".
More like file descriptor. File path is like address system, but it's not how you get all file descriptors. For example: sockets (there is bash's fake /dev/{tcp,udp}), epoll, timer, event, inotify.
In UNIX systems event systems have a list of filedescriptors with a callback for each. You could have your event loop an epoll fd itself and nest it in another.
"Mac OS X" was rebranded to "macOS" (or rather, "macOS" is the successor to "Mac OS X", but really just is the same but newer, the "upgrade" was just like any other update between Mac OS X versions afaik), and "Mac OS 9" does not belong to "macOS".
That is Windows NT personalities. It was originally able to run OS/2 stuff too. Doesn't really make NT a UNIX. Note: They used this stuff for WSLv1, but it was slow and had same issue as WINE. Swapping underlying implementation brings out bugs of the software above.
Un*x. All those projects hate Unix because AT&T started the sue against BSD that broke apart the status quo of open software at that time. Since then all free software is not unix. All of them are POSIX tho.
I always assumed that a lot of this boils down to semantics and trademark law.
OpenIndiana is a direct code-line descendant of Unix System V through OpenSolaris via Solaris. Thank you for that, Sun Microsystems. I understand (but haven't looked) that a lot of code these days is simply ported over from BSD or Linux. If you compare the source code to an old copy of the Lions book, you're probably not going to see any line-by-line overlap. Thank goodness - we shouldn't be literally running old operating systems from the '80s. I don't think that OpenIndiana is Unix-certified by the Open Group (Trademark).
The BSDs started out as a sort of 'Ship of Theseus' rebuild of an academic-licensed copy of Unix around the time that AT&T was getting litigious and corporate Unixes (Unices?) were starting to Balkanize.
GNU/Linux started out as a work-alike (functions the same but with totally different code) inspired by MINIX, which in turn was an education-licensed Unix work-alike designed to show basic operating system principles to students. I think that one or more linux-based operating systems have obtained UNIX certification from the Open Group, just like Apple did for MacOS (paying money and passing some tests). It doesn't seem like any of them are still paying to keep up the certification. Does it matter if they did at one point?
Going back to proprietary corporate Unixes, I believe that IBM AIX and HP-UX still exist as products. They started out as UNIX and have been developed continuously since then. They are both Certified Unix. By now, their codebases probably diverge substantially both from one another and from all of the Unix-likes. IBM also has a mainframe OS with a fascinating history that has nothing to do with UNIX. It is Certified Unix because it passes the right tests and IBM paid for certification. It is not UNIX code and doesn't descend from UNIX code.
Regarding the true Unix, there was also Unixware, which was AT&T's effort to move Unix to PCs (with Novell). It later passed on to SCO before they were sold, restructured, renamed and rebranded and subsequently became lunatics, In the end it seems like they offloaded it so some other company that's just letting it die.
It was a good system. Not super fun, but industrial strength server stuff that was really reliable. Bit of a shame.
But of course, Linux was just simpler for everyone, it just doesn't make sense to keep a million proprietary systems.
A part of me misses the days of dual-using a rock solid professional server OS for business and a cobbled-together similar OS for home computers and older hardware.
Cobbled-together became good enough. Then it became better in some cases. Then it became better in most cases. Now I haven't bothered with a non-Linux for over half a decade.
No, it's not unix. None of the systems in the meme are actually unix.
Linux is unix-like, made initially by 1 guy who just so happened to base it around another unix-like OS and has quite literally nothing to do with unix
BSD has no original AT&T unix code and while it does work in similar ways, it is still not unix
Windows is windows... The closest thing it has ever gotten to unix is the Windows Services for UNIX, which literally only existed so that M$ could claim POSIX compliance and get a lot of government money...