Windows NT used to have a POSIX subsystem [1] that applications could use instead of the Win32 subsystem. So the Windows NT kernel is designed with the option of POSIX compatibility. Arguably the Subsystem for Linux is the current successor of the POSIX subsystem, providing POSIX compatible access to the kernel along with a POSIX compatible shell and UNIX commands.

Obviously the Win32 subsystem isn't POSIX compatible, but I'm not sure why we would want that.

1: https://en.wikipedia.org/wiki/Microsoft_POSIX_subsystem

That subsystem was just so they could tick off the “POSIX” box for Department of Defence.

That was one of many, then came SFU, followed by SUA.

GNU/Linux users should be happy that old Microsoft didn't bother to do that much with POSIX subsystem.

Had they actually invested into keeping it up to date, and many of us on PC land would never bothered with FOSS UNIX clones.

Yeah, that may be true, but on the other hand, had they made it useable, portabilith with other Unix would have been a simpler option.

Simpler than Win32 + Unix portability in any case. Or in some cases, software would have been ported to Win32 at all.

What UNIX portability?

Back when I was in the university, and Linux kernel was still at 1.0, I had the pleasure to write C and C++ code across Xenix, DG/UX, Aix, HP-UX, Solaris, BSD and naturally Linux also.

There is POSIX, there is what each OS actually do for the implementation defined behaviours, then the whole set of APIs that made each UNIX variant unique and were the selling point of the UNIX clone to start with.

Autoconf and friends did not start out of masochism.

>Yeah, that may be true, but on the other hand, had they made it useable, portabilith with other Unix would have been a simpler option.

That's not necessarily the case. See macOS which is using different GUI libraries, Metal instead of Vulkan etc.

So you can't recompile macOS apps to use them on Linux.

People forgot that Microsoft was one of the biggest UNIX vendors with Xenix and for a long time, Microsoft had the highest-volume AT&T Unix license.

In reality, there are very very few people who care about POSIX compatibility. Because there are no POSIX-compatible systems in the wild.

POSIX-certified systems conform to different POSIX standards. And most of them are of no use to the average developer such as AIX, HP-UX, Solaris.

The rest are largely compatible which means they are not compatible. And yes, that includes every single one of Linux distributions and FreeBSD.

I am beginning to think that while POSIX, Unix and X11 might have been innovative and very useful in the '70s and ' 80s, now they are really old and most of the computing landscape changed.

We need better operating systems metaphors.