Portable Operating System Interface or POSIX is standardized application programming interface maintaining compatibility between application and OS. The term POSIX was proposed by Richard Stallman in response to the IEEE’s invitation to give a memorable name; POSIX was previously designated as IEEE-IX.
Brief Description of POSIX
The specification of user and software interface of the operating system is divided into four parts that make up the POSIX standard. There is a list of the standard conventions used including definitions and concepts, there is System interface ; Command line interpreter and utilities and Declarations. We are not elaborating simply because this webpage is not a text book reference page. Most of us need to know about POSIX for other usages related mainly with Linux Servers.
The standard POSIX shell is the Unix shell. Other utilities such as awk , vi or echo are also part of the POSIX standards.
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POSIX compliant operating systems

The following operating systems are POSIX compliant, they adhere to the entire standard:
A / UX, AIX, BlagOS, BSD / OS, Darwin ( Mac OS X ), HP-UX, INTEGRITY, IRIX, LynxOS, MINIX, OpenVMS, penOS, QNX, RTEMS, Solaris and OpenSolaris, UnixWare, velOSity, VxWorks
The following operating systems are largely POSIX compliant, these operating systems have not been officially certified as POSIX-compliant, but to keep the standards :
BeOS and its open-source successor to Haiku, Nucleus RTOS, FreeBSD, All Linux distributions, NetBSD, OpenBSD, PikeOS, SkyOS, SuperUX, Syllable, VSTA
The following operating systems are Compatibility compliant with extensions. These operating systems are not officially certified as POSIX-compliant, but are largely compliant with POSIX and is implemented through a kind of extension compatibility (usually translation libraries) or an intermediate layer of the kernel. Without this extension, they are usually not POSIX compliant :
The NT kernel of Microsoft Windows when using the Microsoft Windows Services for UNIX, eCos, Symbian OS, AmigaOS.
