>POSIX-compliant Which, FWIW, doesn't mean Linux. AFAIK there is no Linux distro that's fully compliant

I read author's use of "POSIX-compliant" as a loose and fuzzy family category rather than an exhaustive and authoritative reference on 100% strict compliance. Therefore, the author mentioning non-100%-compliant Linux is ok.

There seems to be 2 different expectations and interpretations of what the article is about.

- (1) article is attempting to be a strict intersection of all Unix-like systems that conform to official UNIX POSIX API. I didn't think this was a reasonable interpretation since we can't be sure the author actually verified/tested other POSIX-like systems such as FreeBSD, HP-UX, IBM AIX, etc.

- (2) article is a looser union of operating systems and can also include idiosyncracies of certain systems like Linux that the author is familiar with that don't apply to all other UNIX systems. I think some readers don't realize that all the author's citations to man pages point to Linux specific urls at : https://linux.die.net/man/

The ggp's (amstan) additional comment about renameat2(,,,,RENAME_EXCHANGE) is useful info and is consistent with interpretation (2).

If the author really didn't want Linux to be lumped in with "POSIX-like", it seems he would avoid linux.die.net and instead point to something more of a UNIX standard such as: https://unix.org/apis.html

[0] Intersection vs Union: https://en.wikipedia.org/wiki/Set_(mathematics)#Intersection

The slash is read as "OR" in this case.

As in: Unix-like OR POSIX-compliant

In that light, it's probably fine to not nitpick over certifications here.

AFAIK you don't even want to be POSIX-compliant unless having a sticker means more to you than being reasonable. Most projects knowingly steer away from compliance (and certifying compliance is probably also expensive)

EulerOS was certified UNIX some years ago.