You're misinterpreting the title. The author didn't intend "Unix" to literally mean only the official AT&T/TheOpenGroup UNIX® System to the exclusion of Linux.
The first sentence of "UNIX-like" makes that clear : >This is a catalog of things UNIX-like/POSIX-compliant operating systems can do atomically,
Further down, he then mentions some Linux specifics : >fcntl(fd, F_GETLK, &lock), fcntl(fd, F_SETLK, &lock), and fcntl(fd, F_SETLKW, &lock) . [...] There is a “mandatory locking” mode but Linux’s implementation is unreliable as it’s subject to a race condition.
Differing philosophies of how to interpret titles. Prescriptive vs Descriptive language.[0]
There can be different usages of the word "Unix":
#1: Unix is a UNIX(tm) System V descendent. More emphasis that the kernel needs to be UNIX. In this strict definition, you get the common reminder that "Linux is not a Unix!"
#2: "Unix" as a loose generic term for a family of o/s that looks/feels like Unix. This perspective includes using an o/s that has userland Unix utilities like cat/grep/awk. Sometimes deliberately styled as asterisk "*nix" or a suffix-qualifier "Unix-like" but often just written as a naked "Unix".
A Prescriptivist says the author's title is "incorrect". On the other hand, a Descriptivist looks at the whole content of the article -- notices the text has a lot of Linux specific info such as fcntl(,F_GETLEASE/F_SETLEASE), and every hyperlink to a man page url points to https://linux.die.net/man/ , etc -- and thus determines that the author is using "Unix"(#2) in the looser way that can include some Linux idiosyncrasies.
"Unix" instead of "*nix" as a generic term for Linux is not uncommon. Another example article where the authors use the so-called incorrect "Unix" in the title even though it's mostly discussing Linux CUPS instead of Solaris : https://www.evilsocket.net/2024/09/26/Attacking-UNIX-systems...
Which, FWIW, doesn't mean Linux. AFAIK there is no Linux distro that's fully compliant, even before you worry about the specifics of whether it's certified as compliant.
>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
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)
You're misinterpreting the title. The author didn't intend "Unix" to literally mean only the official AT&T/TheOpenGroup UNIX® System to the exclusion of Linux.
The first sentence of "UNIX-like" makes that clear : >This is a catalog of things UNIX-like/POSIX-compliant operating systems can do atomically,
Further down, he then mentions some Linux specifics : >fcntl(fd, F_GETLK, &lock), fcntl(fd, F_SETLK, &lock), and fcntl(fd, F_SETLKW, &lock) . [...] There is a “mandatory locking” mode but Linux’s implementation is unreliable as it’s subject to a race condition.