Ok, there seems to be a lot of confusion here about what POSIX is.
A long time ago, there were a lot of systems by various companies and groups that all claimed to be Unix, or at least Unix compatible. But, since there wasn’t a standardized definition of Unix, they weren’t all compatible with each other. The US government and other groups decided this was a problem and asked the IEEE to come up with a standard that the vendors could certify to. This standard is named POSIX and is composed of low level OS APIs, C language support, shells, utilities and a bunch of other components.
This meant that anything that targets POSIX should run on any POSIX system with nothing more than at most a recompile. There was a time, basically until the early ‘00s, that every major OS targeted being able to be certified POSIX in some way. This was great!
However, since Linux has won the Unix wars, with MacOS in a technical second place, the importance of POSIX has mostly gone away. It is still an important spec. Linux, MacOS and even Windows more or less maintain compatibility with it, but there isn’t a push for certification the way there once was. If it runs on a couple Linux distros and MacOS, that’s probably good enough.
EDIT: The jokes that you might see having to do with POSIX generally are about the fact that MacOS is certified POSIX compliant, but nobody really cares, while Linux has never been certified POSIX compliant but is the de facto standard UNIX and therefore the most common POSIX target.
Ok, there seems to be a lot of confusion here about what POSIX is.
A long time ago, there were a lot of systems by various companies and groups that all claimed to be Unix, or at least Unix compatible. But, since there wasn’t a standardized definition of Unix, they weren’t all compatible with each other. The US government and other groups decided this was a problem and asked the IEEE to come up with a standard that the vendors could certify to. This standard is named POSIX and is composed of low level OS APIs, C language support, shells, utilities and a bunch of other components.
This meant that anything that targets POSIX should run on any POSIX system with nothing more than at most a recompile. There was a time, basically until the early ‘00s, that every major OS targeted being able to be certified POSIX in some way. This was great!
However, since Linux has won the Unix wars, with MacOS in a technical second place, the importance of POSIX has mostly gone away. It is still an important spec. Linux, MacOS and even Windows more or less maintain compatibility with it, but there isn’t a push for certification the way there once was. If it runs on a couple Linux distros and MacOS, that’s probably good enough.
EDIT: The jokes that you might see having to do with POSIX generally are about the fact that MacOS is certified POSIX compliant, but nobody really cares, while Linux has never been certified POSIX compliant but is the de facto standard UNIX and therefore the most common POSIX target.