Is OSX a POSIX OS?

linux macos operating-system posix
node ninja picture node ninja · Apr 26, 2011 · Viewed 30.4k times · Source

What is it that makes an OS a POSIX system? All versions of Linux are POSIX, right? What about OSX?

Answer

Rafe Kettler picture Rafe Kettler · Apr 26, 2011

Yes. POSIX is a group of standards that determine a portable API for Unix-like operating systems. Mac OSX is Unix-based (and has been certified as such), and in accordance with this is POSIX compliant. POSIX guarantees that certain system calls will be available.

Essentially, Mac satisfies the API required to be POSIX compliant, which makes it a POSIX OS.

All versions of Linux are not POSIX-compliant. Kernel versions prior to 2.6 were not compliant, and today Linux isn't officially POSIX-compliant because they haven't gone out of their way to get certified (which will likely never happen). Regardless, Linux can be treated as a POSIX system for almost all intents and purposes.

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