POSIX

POSIX:

The term POSIX (an abbreviation of Portable Operating System Interface) refers to a group of standards developed under the auspices of the Institute of Electrical and Electronic Engineers (IEEE), specifically its Portable Application Standards Committee (PASC, http://www.pasc.org/). The goal of the PASC standards is to promote the application portability at the source code level.
The name POSIX was suggested by Richard Stallman. The final X appears
because the names of most UNIX variants end in X. The standard notes that
the name should be pronounced “pahz-icks,” like “positive.”

POSIX.1 Conformant:

POSIX.1 documents an API for a set of services that should be made available to a program by a conforming operating system. An operating system that does this can be certified as POSIX.1 conformant. POSIX.1 is based on the UNIX system call and the C library function API, but it doesn’t require any particular implementation to be associated with this interface. This means that the interface can be implemented by any operating system, not specifically a UNIX operating system. In fact, some vendors have added APIs to their proprietary operating systems that make them POSIX.1 conformant, while at the same time leaving the underlying operating system largely unchanged.

POSIX.1b extensions:

The POSIX.1b realtime extensions include file synchronization, asynchronous
I/O, process scheduling, high-precision clocks and timers, and interprocess
communication using semaphores, shared memory, and message queues. The
prefix POSIX is often applied to the three interprocess communication methods to distinguish them from the similar, but older, System V semaphores, shared memory, and message queues. A related standard, POSIX.2, standardized the shell and various UNIX utilities, including the command-line interface of the C compiler.

What is FIPS?

FIPS is an abbreviation for Federal Information Processing Standard, the name of a set of standards specified by the US government for the purchase of its computer systems. In 1989, FIPS 151–1 was published. This standard was based on the 1988 IEEE POSIX.1 standard and the draft ANSI C standard.

Difference Between FIPS and POSIX:

The main difference between FIPS 151–1 and POSIX.1 (1988) was that the FIPS standard required some features that POSIX.1 left as optional. Because the US government is a major purchaser of computer systems, most computer vendors ensured that their UNIX systems conformed to the FIPS 151–1 version of POSIX.1.

What is SUSv3:

POSIX 1003.1–2001 replaces SUSv2, POSIX.1, POSIX.2, and a raft of other earlier POSIX standards. This standard is also known as the SUSv3 (Single UNIX Specification Version 3).

SUSv3 base specifications:

Base Definitions (XBD): This part contains definitions, terms, concepts, and specifications of the contents of header files. A total of 84 header file specifica-
tions are provided.

System Interfaces (XSH): This part begins with various useful background information. Its bulk consists of the specification of various functions (which are implemented as either system calls or library functions on specific UNIX implementations). A total of 1123 system interfaces are included in this part.

Shell and Utilities (XCU): This specifies the operation of the shell and various UNIX commands. A total of 160 utilities are specified in this part.

Rationale (XRAT): This part includes informative text and justifications relating to the earlier parts.
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