Apple’s macOS UNIX certification is a lie

Summary

As an online discussion grows longer, the probability of a someone mentioning macOS is a UNIX approaches 1. In fact, it was only late last year that The Open Group announced that macOS 15.0 was, once again, certified as UNIX, continuing Apple’s long-standing tradition of certifying macOS releases as “real” UNIX®. What does any of this actually, mean, though? Well, it turns out that if you actually dive into Apple’s conformance statements for macOS’ UNIX certification, it doesn’t really mean anything at all.First and foremost, we have to understand what UNIX certification really means. In order to be allowed to use the UNIX trademark, your operating system needs to comply with the Single UNIX Specification (SUS), which specifies programming interfaces for C, a command-line shell, and user commands, more or less identical to POSIX, as well as the X/Open Curses specification. The latest version is SUS version 4, originally published in 2008, with amendments published in 2013 and 2016, which were rolled up into version 4 in 2018. The various versions of the SUS that exist, in turn, correspond to a specific UNIX trademark. In table form:TrademarkSUS versionSUS published in:SUS last amended in:UNIX® 93n.a.n.a.n.a.UNIX® 95Version 11994n.a.UNIX® 98Version 21997n.a.UNIX® 03Version 320022004UNIX® V7Version 420082016 (2018 for roll-up)When you read that macOS is a certified UNIX, which of these versions and trademarks do you assume macOS complies with? You’d assume they would just target the latest trademark and SUS version, right? This would allow macOS to carry the UNIX® V7 trademark, because they would conform to version 4 of the SUS, which dates to 2016. The real answer is that macOS 15.0 only conforms to version 3 of the SUS, which dates all the way back to the ancient times of 2004, and as such, macOS is only UNIX® 03 (on both Intel and ARM). However, you can argue this is just semantics, since it’s not like UNIX and POSIX are very inclined to change.So now, like the UNI...