Cygwin consists of two parts: a dynamic-link library ( DLL ) as an API compatibility layer providing a substantial part of the POSIX API functionality, and an extensive collection of software tools and applications that provide a Unix-like look and feel.

Support for compiling programs that do not require the POSIX compatibility layer provided by the Cygwin DLL used to be included in the default gcc, but is now provided by cross compilers contributed by the MinGW-w64 project.

* UWIN from AT & T Research implements a POSIX layer on top of the Win32 APIs.

The following are not officially certified as POSIX compatible, but they conform in large part to the standards by implementing POSIX support via some sort of compatibility feature, usually translation libraries, or a layer atop the kernel.

Cygnus was also the original developer of Cygwin, a POSIX layer and the GNU toolkit port to the Microsoft Windows operating system family, and of eCos, an embedded real-time operating system.

* bash — A Unix shell commonly run on Linux and other modern Unix-like systems, as well as on Windows via the Cygwin POSIX compatibility layer.

Although both Cygwin and MinGW can be used to port Unix software to Windows, they have different approaches: Cygwin aims to provide a complete POSIX layer that provides emulations of several system calls and libraries that exist on Linux, Unix, and the BSD variants.

The Berkeley Software Distribution ( BSD ) portion of the kernel provides the POSIX API ( BSD system calls ), the Unix process model atop Mach tasks, basic security policies, user and group ids, permissions, the network stack, the virtual file system code ( including a filesystem independent journaling layer ), several local file systems such as HFS / HFS +, the Network File System ( NFS ) client and server, cryptographic framework, UNIX System V inter-process communication ( IPC ), Audit subsystem, mandatory access control, and some of the locking primitives.

* ANSI / POSIX Environment, a POSIX compatibility layer for the Plan 9 operating system

Shortly after visiting the Be Inc. offices to see a demo of the computer, he began working on the BeOS, working initially in a number of areas including the kernel and the POSIX layer but most notably developing the Be File System alongside Cyril Meurillon, which replaced the Old Be File System written by Benoit Schillings which had itself replaced the original flat file system written by Meurillon.

KDE on Cygwin is the port of the Qt toolkit and the KDE desktop environment ( both of which are commonly found in Linux ) to the Windows Operating System by using Cygwin, a POSIX emulation layer.

It is programmed in the C programming language, and has a POSIX emulation layer.

The BSD layer in Mac OS X ( and Darwin ) is responsible for file-system security, including the management of the Unix ( POSIX ) permissions model.

It is written in Common Lisp and runs on all POSIX platforms such as Mac OS X, Unix, BSD, and GNU / Linux as well as under Microsoft Windows.

It runs in a variety of POSIX environments such as Linux, Android, FreeBSD and others, such as proprietary kernels, although many of the tools it provides are designed to work with interfaces provided by the Linux kernel.

On operating systems that support the SUS and POSIX standards, ps commonly runs with the options-ef, where "- e " selects every process and "- f " chooses the " full " output format.

Tin runs on any UNIX or POSIX platform.

Postfix runs on AIX, BSD, HP-UX, IRIX, GNU / Linux, Mac OS X, Solaris, Tru64 UNIX and, generally speaking, on every Unix-like operating system that ships with a C compiler and which delivers a standard POSIX development environment.

Cygwin consists of a library that implements the POSIX system call API in terms of Win32 system calls, a GNU development toolchain ( including GCC and GDB ) to allow software development, and a large number of application programs equivalent to those on Unix systems.

POSIX mandates 512-byte block sizes for the df and du utilities, reflecting the default size of blocks on disks.

When Richard Stallman and the GNU team were implementing POSIX for the GNU operating system, they objected to this on the grounds that most people think in terms of 1024 byte ( or 1 KiB ) blocks.

* Symbian OS with PIPS ( PIPS Is POSIX on Symbian )

The standard user command line and scripting interface is the POSIX shell, an extension of the Bourne Shell based on an early version of the Korn Shell.

The sh of FreeBSD, NetBSD ( and their derivatives ) are based on ash that has been enhanced to be POSIX conformant for the occasion.

Is POSIX on Symbian

It supports the POSIX API by way of its BSD lineage and a large number of programs written for various other UNIX-like systems can be compiled on Darwin with no changes to the source code.

The Rock Ridge Interchange Protocol ( RRIP, IEEE P1282 ) is an extension to the ISO 9660 volume format, commonly used on CDROM and DVD media, which adds POSIX file system semantics.

Thus both Amiga Rock Ridge and the POSIX RRIP may be used simultaneously on the same volume.

Most of the Unix and Unix-like operating systems ( e. g. Linux, BSD, or Solaris ) support POSIX. 1e ACLs, based on an early POSIX draft that was abandoned.

Toward the end of the 1990s, the company ( now called QNX Software Systems ) began work on a completely new version of the QNX RTOS, designed from the ground up to be SMP capable, and to support all current POSIX APIs and any new POSIX APIs that could be anticipated while still retaining the microkernel architecture.

* Juce: An application framework written in C ++, used to write native software on numerous systems ( Microsoft Windows, POSIX, Mac OS X ), with no change to the code.

This standard uses CORBA on POSIX operating systems to coordinate various software modules.

Lex, originally written by Mike Lesk and Eric Schmidt and described in 1975, is the standard lexical analyzer generator on many Unix systems, and a tool exhibiting its behavior is specified as part of the POSIX standard.

Only a subset of POSIX calls was supported, and only one process could run at a time on node in co-processor mode — or one process per CPU in virtual mode.

It is based on standard Unix devices ( i. e. POSIX read, write, ioctl, etc .).

Plucker contains POSIX tools, scripts and " conduits " which work on Unix, Linux, Mac OS X, and Microsoft Windows.

Porting such a program between two standards-compliant platforms ( such as POSIX. 1 ) can be just a matter of loading the source code and recompiling it on the new platform.

Scsh is a POSIX API layered on top of the Scheme programming language in a manner to make the most of Scheme's capability for scripting.

DR-DOS and Microsoft Windows implementations also exist: within the SFU / SUA subsystem which provides a native implementation of a number of POSIX APIs, and also within third-party packages such as pthreads-w32, which implements pthreads on top of existing Windows API.

Cygwin 1. 5 represented them as Windows Explorer shortcuts, but this has been changed for reasons of performance and POSIX correctness.

Programmers do need to be careful though about mixing conflicting POSIX and Windows functions.

* MKS Inc .′ s MKS Korn shell — a proprietary implementation of the KornShell language from Microsoft Windows Services for UNIX ( SFU ) up to version 2. 0 ; according to David Korn, the MKS Korn shell was not fully compatible with KornShell in 1998 ; in SFU version 3. 0 Microsoft replaced the MKS Korn shell with a new POSIX. 2-compliant shell as part of Interix ;

* Microsoft POSIX subsystem, an optional Windows subsystem included in Windows NT-based operating systems up to Windows 2000.

It enables full POSIX compliance for certain Microsoft Windows products.

To be POSIX compliant, one must activate optional features of Windows NT and Windows 2000 Server.

* Interix – a full-featured POSIX and Unix environment subsystem for Microsoft's Windows NT-based operating systems

For instance, Microsoft Windows uses the API functions < tt > LoadLibrary </ tt >, < tt > LoadLibraryEx </ tt >, < tt > FreeLibrary </ tt > and < tt > GetProcAddress </ tt > with Microsoft Dynamic Link Libraries ; POSIX based systems, including most UNIX and UNIX-like systems, use < tt > dlopen </ tt >, < tt > dlclose </ tt > and < tt > dlsym </ tt >.

Today they are supported by the POSIX operating-system standard, most Unix-like operating systems such as FreeBSD, GNU / Linux, and Mac OS X, and also Windows operating systems such as Windows Vista, Windows 7 and to some degree in Windows 2000 and Windows XP in the form of Shortcut files.

* Microsoft Windows shortcuts normally refer to a destination by an absolute path ( starting from the root directory ), whereas POSIX symbolic links can refer to destinations via either an absolute or a relative path.

* Microsoft Windows application shortcuts contain additional metadata that can be associated with the destination, whereas POSIX symbolic links are just strings that will be interpreted as absolute or relative pathnames.

Apple's mDNSResponder has interfaces for C and Java and is available on BSD, Apple Mac OS X, Linux, other POSIX based operating systems and MS Windows.