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The Single UNIX Specification (SUS) is the collective name of a family of standards for computer
Computer

A computer is a machine that manipulates Data according to a list of Code .The first devices that resemble modern computers date to the mid-20th century , although the computer concept and various machines similar to computers existed earlier....
 operating system
Operating system

An operating system is an interface between hardware and applications; it is responsible for the management and coordination of activities and the sharing of the limited resources of the computer....
s to qualify for the name "Unix
Unix

Unix is a computer operating system originally developed in 1969 by a group of American Telephone & Telegraph employees at Bell Labs, including Ken Thompson , Dennis Ritchie, Douglas McIlroy, and Joe Ossanna....
". The SUS is developed and maintained by the Austin Group
Austin Group

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....
, based on earlier work by the IEEE and The Open Group
The Open Group

The Open Group is an industry consortium to set vendor- and technology-neutral open standards for computing infrastructure. It was formed when X/Open merged with the Open Software Foundation in 1996....
.

SUS emerged from a mid-1980s project to standardize operating system
Operating system

An operating system is an interface between hardware and applications; it is responsible for the management and coordination of activities and the sharing of the limited resources of the computer....
 interface
Interface (computer science)

Interface generally refers to an Abstraction_%28computer_science%29 that an entity provides of itself to the outside. This separates the methods of external communication from internal operation, and allows it to be internally modified without affecting the way outside entities interact with it, as well as provide Polymorphism in object-orien...
s for software designed for variants of the Unix operating system. The need for standardization arose because enterprises using computers wanted to be able to develop programs that could be used on the computer systems of different manufacturers without reimplementing the programs. Unix was selected as the basis for a standard system interface partly because it was manufacturer-neutral.






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The Single UNIX Specification (SUS) is the collective name of a family of standards for computer
Computer

A computer is a machine that manipulates Data according to a list of Code .The first devices that resemble modern computers date to the mid-20th century , although the computer concept and various machines similar to computers existed earlier....
 operating system
Operating system

An operating system is an interface between hardware and applications; it is responsible for the management and coordination of activities and the sharing of the limited resources of the computer....
s to qualify for the name "Unix
Unix

Unix is a computer operating system originally developed in 1969 by a group of American Telephone & Telegraph employees at Bell Labs, including Ken Thompson , Dennis Ritchie, Douglas McIlroy, and Joe Ossanna....
". The SUS is developed and maintained by the Austin Group
Austin Group

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....
, based on earlier work by the IEEE and The Open Group
The Open Group

The Open Group is an industry consortium to set vendor- and technology-neutral open standards for computing infrastructure. It was formed when X/Open merged with the Open Software Foundation in 1996....
.

History

The SUS emerged from a mid-1980s project to standardize operating system
Operating system

An operating system is an interface between hardware and applications; it is responsible for the management and coordination of activities and the sharing of the limited resources of the computer....
 interface
Interface (computer science)

Interface generally refers to an Abstraction_%28computer_science%29 that an entity provides of itself to the outside. This separates the methods of external communication from internal operation, and allows it to be internally modified without affecting the way outside entities interact with it, as well as provide Polymorphism in object-orien...
s for software designed for variants of the Unix operating system. The need for standardization arose because enterprises using computers wanted to be able to develop programs that could be used on the computer systems of different manufacturers without reimplementing the programs. Unix was selected as the basis for a standard system interface partly because it was manufacturer-neutral. These standards became in 1988 IEEE 1003 (also registered as ISO
International Organization for Standardization

The International Organization for Standardization , widely known as ISO , is an international standard-setting body composed of representatives from various national standards organizations....
/IEC
International Electrotechnical Commission

The International Electrotechnical Commission is a Non-profit organization, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies ? collectively known as "electrotechnology"....
 9945), or POSIX
POSIX

POSIX or "Portable Operating System Interface" is the collective name of a family of related standardizations specified by the Institute of Electrical and Electronics Engineers to define the application programming interface , along with shell and utilities interfaces for software compatible with variants of the Unix operating system, altho...
, which loosely stands for Portable Operating System Interface for uniX.

In the early 1990s, a separate effort known as the Common API Specification or Spec 1170 was initiated by several major vendors, who formed the COSE alliance in the wake of the Unix wars
Unix wars

The Unix wars were the struggles between vendors of the Unix computer operating system in the late 1980s and early 1990s to set the standard for Unix thenceforth....
. This specification became more popular because it was available at no cost, whereas the IEEE charged a substantial fee for access to the POSIX specification.

Beginning in 1998, a joint working group
Working Group

Working Group can mean:*Working group, an interdisciplinary group of researchers; or*Working Group , kennel club designation for certain purebred dog breeds; or...
 known as the Austin Group
Austin Group

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....
 began to develop the combined standard that would be known as the Single UNIX Specification Version 3; it was released on January 30, 2002.

Specification

The user and software interfaces to the OS are specified in four main sections:

  • Base Definitions - a list of definitions and conventions used in the specifications and a list of C
    C (programming language)

    C is a general-purpose computer programming language originally developed in 1972 by Dennis Ritchie at the Bell Telephone Laboratories to implement the Unix operating system....
     header files which must be provided by compliant systems.
  • Shell and Utilities - a list of utilities and a description of the shell, sh
    Bourne shell

    The Bourne shell, or sh, was the default Unix shell of Version 7 Unix, and replaced the Thompson shell, whose executable file had the same name, sh....
    .
  • System Interfaces - a list of available C system calls which must be provided.
  • Rationale - the explanation behind the standard.


The standard user command line and scripting interface is the POSIX
POSIX

POSIX or "Portable Operating System Interface" is the collective name of a family of related standardizations specified by the Institute of Electrical and Electronics Engineers to define the application programming interface , along with shell and utilities interfaces for software compatible with variants of the Unix operating system, altho...
 shell, an extension of the Bourne Shell
Bourne shell

The Bourne shell, or sh, was the default Unix shell of Version 7 Unix, and replaced the Thompson shell, whose executable file had the same name, sh....
 based on an early version of the Korn Shell
Korn shell

The Korn shell is a Unix shell which was developed by David Korn in the early 1980s. It is backwards-compatible with the Bourne shell and includes many features of the C shell as well, such as a command history, which was inspired by the requests of Bell Labs users....
. Other user-level programs, services and utilities include awk
AWK (programming language)

AWK is a programming language that is designed for processing text-based data, either in files or data streams, and was created at Bell Labs in the 1970s....
, echo
Echo (computing)

In computing, echo is a command in DOS, OS/2, Microsoft Windows, Singularity , Unix and Unix-like operating systems that places a String on the computer terminal....
, ed, vi
Vi

vi is a family of screen-oriented text editors which share common characteristics, such as methods of invocation from the operating system command interpreter, and characteristic user interface features....
, and hundreds of others. Required program-level services include basic I/O
Input/output

In computing, input/output, or I/O, refers to the communication between an information processing system , and the outside world ? possibly a human, or another information processing system....
 (file
Computer file

A computer file is a block of arbitrary information, or resource for storing information, which is available to a computer program and is usually based on some kind of durable computer storage....
, terminal
Computer terminal

A computer terminal is an electronic or electromechanical computer hardware device that is used for entering data into, and displaying data from, a computer or a computing system....
, and network
Computer network

A computer network is a group of interconnected computers. Networks may be classified according to a wide variety of characteristics. This article provides a general overview of some types and categories and also presents the basic components of a network....
) services.

A test suite accompanies the standard. It is called PCTS or the Posix Certification Test Suite.

Note that a system need not include source code
Source code

In computer science, source code is any collection of statements or declarations written in some human-readable computer programming language....
 derived in any way from AT&T Unix to meet the specification. For instance, IBM
IBM

International Business Machines Corporation, abbreviated IBM and nicknamed "Big Blue" , is a multinational corporation computer technology and consulting corporation headquartered in Armonk, New York, New York, United States....
 OS/390
OS/390

OS/390 is an International Business Machines operating system for the System/390 IBM mainframes.OS/390 was introduced in late 1995 in an effort, led by the late Randy Stelman, to simplify the packaging and ordering for the key, entitled elements needed to complete a fully functional MVS operating system package....
, now z/OS
Z/OS

z/OS is a 64-bit operating system for mainframe computers, created by IBM. It is the successor to OS/390, which in turn followed MVS and combined a number of formerly separate, related products....
, qualifies as a "Unix" despite no code in common.

Marks for compliant systems

There are two official marks for conforming systems
  • UNIX 98 - the mark for systems conforming to version 2 of the SUS (partial compliance)
  • UNIX 03 - the mark for systems conforming to version 3 of the SUS (full compliance)


Older UNIX standards (superseded)
  • UNIX93 (completely superseded)
  • UNIX95 (compliance still acceptable for some simpler software subsystems)


Compliance


AIX

AIX 5L V5.2 with some updates, and AIX 5L V5.3, are registered as UNIX 03 compliant. AIX 5L V5.2 is registered as UNIX 98 compliant.

HP/UX

HP-UX
HP-UX

HP-UX 11i is Hewlett-Packard's proprietary software implementation of the Unix operating system, based on UNIX System V . It runs on the HP 9000 PA-RISC-based range of central processing unit and HP Integrity Intel's Itanium-based systems, and was also available for later Apollo/Domain systems....
 11i V3 Release B.11.31 is registered as UNIX 03 compliant. Previous releases are registered as UNIX 95.

Mac OS X and Mac OS X Server


Mac OS X v10.5
Mac OS X v10.5

Mac OS X version 10.5 "Leopard" is the sixth Software version of Mac OS X, Apple Inc. desktop and server operating system for Apple Macintosh computers, and the successor to Mac OS X v10.4 "Tiger"....
 "Leopard" and Mac OS X Server
Mac OS X Server

Mac OS X Server is Apple's UNIX server operating system. Based on the same architecture as Mac OS X, Mac OS X Server includes additional services, applications and administration tools for managing and deploying servers....
 v10.5 "Leopard Server", released on October 26, 2007, are Open Brand UNIX 03 registered products when run on Intel processors.

SCO

UnixWare
UnixWare

UnixWare is a Unix operating system maintained by The SCO Group . Unixware is typically deployed as a Server rather than Desktop computer. Binary distributions of UnixWare are available for x86 architecture computers....
 7.1.3 is registered as UNIX 95 compliant. SCO OpenServer
SCO OpenServer

SCO OpenServer, previously SCO UNIX and SCO Open Desktop , is a closed source version of the Unix computer operating system developed by Santa Cruz Operation and now maintained by the SCO Group....
 5 is registered as UNIX 93 compliant.

Solaris

Solaris
Solaris Operating System

Solaris is a Unix-based operating system introduced by Sun Microsystems in 1992 as the successor to SunOS.Solaris is known for its scalability, especially on SPARC systems, and for originating many innovative features such as DTrace and ZFS....
 10 is registered as UNIX 03 compliant on 32-bit
32-bit

The range of integer values that can be stored in 32 bits is 0 through 4,294,967,295 or -2,147,483,648 through 2,147,483,647 using two's complement encoding....
 and 64-bit
64-bit

64-bit CPUs have existed in supercomputers since the 1960s and in RISC-based computer workstation and Server s since the early 1990s. In 2003 they were introduced to the mainstream personal computer arena, in the form of the x86-64 and 64-bit PowerPC processor architectures....
 x86 and SPARC
SPARC

SPARC is a Reduced Instruction Set Computer microprocessor instruction set Computer architecture originally designed in 1985 by Sun Microsystems....
 systems. Solaris 8 and 9 are registered as UNIX 98 compliant on the same platforms, except that they do not include support for 64-bit x86 systems.

Solaris 2.5.1 was also registered as UNIX 95 compliant on the PReP
Prep

Prep may refer to:* P-rep, a statistical value of the probability of replicating an observed effect* Curtis Sittenfeld#Prep, a novel by Curtis Sittenfeld...
 PowerPC
PowerPC

PowerPC is a RISC instruction set architecture created by the 1991 Apple Inc.?IBM?Motorola alliance, known as AIM alliance. Originally intended for personal computers, PowerPC CPUs have since become popular embedded system and high-performance processors....
 platform in 1996, but the product was withdrawn before more than a few dozen copies had been sold.

Tru64 UNIX

Tru64 UNIX
Tru64 UNIX

Tru64 UNIX is a 64-bit UNIX operating system for the DEC Alpha instruction set architecture , currently owned by Hewlett-Packard . Previously, Tru64 UNIX was a product of Compaq, and before that, Digital Equipment Corporation , where it was known as Digital UNIX ....
 V5.1A and later are registered as UNIX 98 compliant.

z/OS


IBM z/OS
Z/OS

z/OS is a 64-bit operating system for mainframe computers, created by IBM. It is the successor to OS/390, which in turn followed MVS and combined a number of formerly separate, related products....
 prior to 1.9 is registered as UNIX 95 compliant.

IBM has announced that z/OS 1.9, released on September 28,2007, will "better align" with UNIX 03 (partial or full compliance is unclear thus far).

Other compliant systems

Other operating systems registered as UNIX 95 or UNIX 93 compliant:
  • NCR
    NCR Corporation

    NCR Corporation is a technology company specializing in products for the retail and financial sectors. Its main products are point of sale, automatic teller machines, cheque processing systems, barcode reader, and business consumables....
     UNIX SVR4
  • NEC
    NEC

    is a Japan multinational corporation IT company headquartered in Minato, Tokyo, Japan. NEC, part of the Sumitomo Group, provides information technology and network solutions to business enterprises, communications services providers and government....
     UX/4800


Non-registered Unix-like systems


Vendors of Unix-like
Unix-like

A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....
 systems such as Linux
Linux

Linux is a generic term referring to Unix-like computer operating systems based on the Linux kernel. Their development is one of the most prominent examples of free and open source software collaboration; typically all the underlying source code can be used, freely modified, and redistributed by anyone under the terms of the GNU GPL license...
 and BSD do not typically certify their distribution
Software distribution

A software distribution, also referred to as a software distro, is a bundle of a specific software , already compiled and configured. It is generally the closest thing to a turnkey form of a usually GNU General Public License, free software source code for a software....
s, as the cost of certification and the rapidly changing nature of such distributions make the process too expensive to sustain.

BSD
No freely available BSD system has been registered as SUS compliant.

FreeBSD has a "C99 and POSIX Conformance Project" which aims for full compliance with a large subset of the SUS.

Darwin
Darwin (operating system)

Darwin is an open source POSIX-compliant computer operating system released by Apple Inc. in 2000. It is composed of code developed by Apple, as well as code derived from NEXTSTEP, FreeBSD, and other free software projects....
 is an open source operating system: it is essentially the open source subset of Mac OS X. Darwin is compliant with the SUS 03 .

Linux

No Linux distribution has been registered as SUS compliant.

The Linux Standard Base
Linux Standard Base

The Linux Standard Base, or LSB, is a joint project by several Linux distributions under the organizational structure of the Linux Foundation to standardize the software system structure used with the Linux operating system....
 was formed in 2001 as an attempt to standardize the internal structures of Linux-based systems for increased compatibility. It is based on, and also extends in several areas, the POSIX specifications, Single UNIX Specification, and other open standards. It is de facto
De facto

De facto is a Latin expression that means "concerning the fact" or in practice but not necessarily ordained by law. It is commonly used in contrast to de jure when referring to matters of law, governance, or technique that are found in the common experience as created or developed without or contrary to a regulation....
 accepted and followed by many Linux distributions.

See also

  • Unix wars
    Unix wars

    The Unix wars were the struggles between vendors of the Unix computer operating system in the late 1980s and early 1990s to set the standard for Unix thenceforth....
  • Native POSIX Thread Library
    Native POSIX Thread Library

    The Native POSIX Thread Library is a software feature that enables the Linux kernel to run programs written to use POSIX Threads fairly efficiently....
     for a Linux-specific implementation of the popular POSIX threads library
  • Functional specification
    Functional specification

    A functional specification in systems engineering and software development, is the set of documentation that describes the requested behavior of an engineering system....
  • UNIX manual
    Manual page (Unix)

    Almost all substantial Unix and Unix-like operating systems have extensive documentation known as man pages . The Unix command used to display them is man....
  • Open system (computing)
    Open system (computing)

    Open systems are computer systems that provide some combination of interoperability, porting, and open standards. The term was popularized in the early 1980s, mainly to describe systems based on Unix, especially in contrast to the more entrenched mainframe computer and minicomputers in use at that time....
  • Open standard
    Open standard

    An open standard is a standard that is publicly available and has various rights to use associated with it, and various properties of how it was designed....


External links

  • (Living Internet)
  • (Eric S. Raymond
    Eric S. Raymond

    Eric Steven Raymond , often referred to as ESR, is a computer programmer, author and open source software advocate. His name became known within the hacker culture when he became the maintainer of the "Jargon File"....
    , The Art of Unix Programming
    The Art of Unix Programming

    The Art of Unix Programming by Eric Raymond is a book about the history and culture of Unix programming from its earliest days in 1969 to now, covering both genetic derivations such as BSD and conceptual ones such as Linux....
    )