POSIX

POSIX compatiblePOSIX standardixemul.libraryPOSIX.1POSIX.2UNIXUnix-likeIEEE POSIX P1003.2IEEE Standard 1003.5b-1996IEEE Std 1003.1-2008
The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems.wikipedia
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Application programming interface

APIAPIsapplication programming interfaces
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.
POSIX, Windows API and ASPI are examples of different forms of APIs.

Ed (text editor)

eded (programming language)ed editor
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).
It remains part of the POSIX and Open Group standards for Unix-based operating systems, alongside the more sophisticated full-screen editor vi.

UNIX System V

System VSVR4System V Release 4
The standardized user command line and scripting interface were based on the UNIX System V shell.
Since the early 1990s, due to standardization efforts such as POSIX and the commercial success of Linux, the division between System V and BSD has become less important.

Unix

Unix-likeUNIX-basedUX
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.
In the late 1980s, an open operating system standardization effort now known as POSIX provided a common baseline for all operating systems; IEEE based POSIX around the common structure of the major competing variants of the Unix system, publishing the first POSIX standard in 1988.

Austin Group

The development of the POSIX standard takes place in the Austin Group (a joint working group linking the IEEE, The Open Group and the ISO/IEC JTC 1 organizations).
The Austin Group or the Austin Common Standards Revision Group is a joint technical working group formed to develop and maintain a common revision of POSIX.1 and parts of the Single UNIX Specification.

C standard library

libcstandard librarystandard C library
C Library (Standard C)
The POSIX standard added several nonstandard C headers for Unix-specific functionality.

POSIX Threads

pthreadspthreadlibpthread
POSIX.1c: Threads extensions (IEEE Std 1003.1c-1995)
POSIX Threads is an API defined by the standard POSIX.1c, Threads extensions (IEEE Std 1003.1c-1995).

Bus error

busBus Errorsunaligned addresses
Bus Errors
On POSIX-compliant platforms, bus errors usually result in the SIGBUS signal being sent to the process that caused the error.

Operating system

operating systemsOScomputer operating system
The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems.
Unix interoperability was sought by establishing the POSIX standard.

Single UNIX Specification

SUSOpen Brand UNIX 03UNIX 95
The specifications are known under the name Single UNIX Specification, before they become a POSIX standard when formally approved by the ISO.
Very few BSD and Linux-based operating systems are submitted for compliance with the Single UNIX Specification, although system developers generally aim for compliance with POSIX standards, which form the core of the Single UNIX Specification.

Unix-like

*nixUnixlike
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.).
Growing incompatibility among these systems led to the creation of interoperability standards, including POSIX and the Single UNIX Specification.

Unix shell

shellshellssh
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.
Almquist shell (ash): written as a BSD-licensed replacement for the Bourne Shell; often used in resource-constrained environments. The sh of FreeBSD, NetBSD (and their derivatives) are based on ash that has been enhanced to be POSIX conformant for the occasion.

Integrity (operating system)

IntegrityINTEGRITY-178BGreen Hills INTEGRITY
Integrity
INTEGRITY is POSIX-certified and intended for use in embedded systems of 32-bits or 64-bits.

AWK

gawkAWK languageeither gawk or mawk
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).
This is like the getenv function in various standard libraries and POSIX.

Darwin (operating system)

DarwinDarwin operating systemApple Darwin
Darwin (core of OS X/macOS and iOS)
It is mostly POSIX-compatible, but has never, by itself, been certified as compatible with any version of POSIX.

MINIX

MINIX 3
MINIX (now MINIX3)
MINIX (from "mini-Unix") is a POSIX-compliant (since version 2.0), Unix-like operating system based on a microkernel architecture.

BeOS

Be Operating SystemBeBeOS 5
BeOS (and subsequently Haiku)
It has partial POSIX compatibility and access to a command-line interface through Bash, although internally it is not a Unix-derived operating system.

Linux Standard Base

LSBLinux Standard Base (LSB)LSB 4.1
Linux (most distributions — see Linux Standard Base)
The LSB is based on the POSIX specification, the Single UNIX Specification (SUS), and several other open standards, but extends them in certain areas.

NuttX

NuttX
Scalable from 8-bit to 32-bit microcontroller environments, the primary governing standards in NuttX are POSIX and ANSI standards.

LynxOS

LynxOS
Sometimes known as the Lynx Operating System, LynxOS features full POSIX conformance and, more recently, Linux compatibility.

MacOS

Mac OS XMacOS X
Darwin (core of OS X/macOS and iOS) macOS (since 10.5 Leopard)
At macOS's core is a POSIX-compliant operating system built on top of the XNU kernel, with standard Unix facilities available from the command line interface.

Richard Stallman

Richard M. StallmanStallman Stallman, Richard
Richard Stallman suggested the name POSIX to the IEEE instead of former IEEE-IX.
Stallman's influences on hacker culture include the name POSIX and the Emacs editor.

Asynchronous I/O

asynchronousnon-blocking I/Onon-blocking
Asynchronous and Synchronous I/O
SVR4 Unixes (and thus POSIX) offer both calls.

Cygwin

Cygwin projectWindows/Cygwin
Cygwin provides a largely POSIX-compliant development and run-time environment for Microsoft Windows.
Cygwin is a POSIX-compatible environment that runs natively on Microsoft Windows.

Nucleus RTOS

NucleusNucleus PLUSNucleus OS
Nucleus RTOS
C++, POSIX and Micro ITRON interfaces