​It should have added - that's easy today.  Just buy an Apple Mac or create an HackenTosh, then ignore the Apple UI, just run from the terminal.  Darwin is Mach 2.5, with BSD under the covers.     Although to be fair, over the years, that have more and more diverted from a lot of core UNIX in many things in the back, but frankly, I do find it more UNIX-like than not and  40+ years of "muscle memory" in my fingers mostly get the right results.

Clem