Portable Operating System Interface(POSIX)

1. Overview

The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines the application programming interface (API), along with command-line shells and utility interfaces, for software compatibility with variants of Unix and other operating systems.

2. Description

Unix was selected as the basis for a standard system interface partly because it was "manufacturer-neutral". However, several major versions of Unix existed—so there was a need to develop a common-denominator system. The POSIX specifications for Unix-like operating systems originally consisted of a single document for the core programming interface, but eventually grew to 19 separate documents (POSIX.1, POSIX.2, etc). The standardized user command line and scripting interface were based on the UNIX System V shell. Many user-level programs, services, and utilities (including awk, echo, ed) were also standardized, along with required program-level services (including basic I/O: file, terminal, and network). POSIX also defines a standard threading library API which is supported by most modern operating systems. In 2008, most parts of POSIX were combined into a single standard (IEEE Std 1003.1-2008, also known as POSIX.1-2008).

As of 2014, POSIX documentation is divided into two parts:

• POSIX.1, 2013 Edition: POSIX Base Definitions, System Interfaces, and Commands and Utilities (which include POSIX.1, extensions for POSIX.1, Real-time Services, Threads Interface, Real-time Extensions, Security Interface, Network File Access, and Network Process-to-Process Communications, User Portability Extensions, Corrections, and Extensions, Protection and Control Utilities, and Batch System Utilities. This is POSIX 1003.1-2008 with Technical Corrigendum 1.)
• POSIX Conformance Testing: A test suite for POSIX accompanies the standard: VSX-PCTS or the VSX POSIX Conformance Test Suite.

The development of the POSIX standard takes place in the Austin Group (a joint working group among the IEEE, The Open Group, and the ISO/IEC JTC 1).

3. Modules

3.1 Clocks and timers

POSIX

3.2 Condition variables

3.3 Message queues

3.4 Mutual exclusion

3.5 Process scheduling

3.6 Semaphores

3.7 Thread management

3.8 Scheduling management

4. Reference

randu.org/tutorials/threads/

en.wikipedia.org/wiki/POSIX

xenomai.org/documentation/xenomai-3/html/xeno3prm/group__cobalt__api.html

en.wikipedia.org/wiki/Xenomai