POSIX.1, POSIX.1b and POSIX.1c (POSIX Services and Extensions for Embedded and Real-Time Systems)

LynxOS: Full implementation of POSIX.1, .1b and .1c.
lynxos-35pxPOSIX is such an integral part of LynxOS that we ship it with a copy of the O’Reilly POSIX manual.

In addition to the POSIX®.1 specification, the LynxOS® real-time operating system (RTOS) also fully implements the POSIX.1b and POSIX.1c subsets:

  1. POSIX.1: POSIX core services (the feature set usually found in UNIX® operating systems)
  2. POSIX.1b: real-time extensions
  3. POSIX.1c: thread extensions

While LynxOS fully supports the POSIX.1b and POSIX.1c subsets, many operating systems only partially support them—if at all.

For example, “traditional” RTOSes usually implement portions of POSIX.1b and POSIX.1c, but they may lack many of the core POSIX.1 features such as fork(). Then there are operating systems like UNIX and Linux®, which are by nature very close to the POSIX.1 specification, but which rarely implement all of the real-time and thread extensions of POSIX.1b and POSIX.1c.

POSIX.1
Core Services (incorporates Standard ANSI C)
POSIX.1b
Real-time extensions
POSIX.1c
Threads extensions
  • Process Creation and Control
  • Signals
  • Floating Point Exceptions
  • Segmentation Violations
  • Illegal Instructions
  • Bus Errors
  • Timers
  • File and Directory Operations
  • Pipes
  • C Library (Standard C)
  • I/O Port Interface and Control
  • Priority Scheduling
  • Real-Time Signals
  • Clocks and Timers
  • Semaphores
  • Message Passing
  • Shared Memory
  • Asynch and Synch I/O
  • Memory Locking
  • Thread Creation, Control, and Cleanup
  • Thread Scheduling
  • Thread Synchronization
  • Signal Handling
There are standardized tests approved by the IEEE for POSIX.1 conformance. POSIX.1 is the feature set most commonly found in UNIX operating systems, and the POSIX test suite was the means used to insure that UNIX operating systems are interoperable.LynxOS first passed the official NIST POSIX-conformance test suite FIPS 151-1, and was later recertified to the more stringent FIPS 151-2. The official sites for certified POSIX-conformant products are:

Currently, the NIST POSIX-conformance test suites do not cover the POSIX.1b and POSIX.1c extensions.opengroupHowever, a group of test suites is provided by the Open Group instead. These may be downloaded from the OpenGroup web site.