Single UNIX Specification
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The Single UNIX Specification (SUS) is the collective name of a family of standards for
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computer
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operating system
s, compliance with which is required to qualify for using the "
UNIX Unix (; trademarked as UNIX) is a family of multitasking, multiuser Multi-user software is computer software Software is a collection of Instruction (computer science), instructions and data (computing), data that tell a computer how to ...

UNIX
" trademark. The core specifications of the SUS are developed and maintained by the
Austin Group The Austin Group or the Austin Common Standards Revision Group is a joint technical working groupWorking Group may refer to: * Working group, an interdisciplinary group of researchers; or * Working Group (dogs), kennel club designation for certain ...
, which is a joint working group of
IEEE The Institute of Electrical and Electronics Engineers (IEEE) is a professional association A professional association (also called a professional body, professional organization, or professional society) seeks to advocacy, further a particul ...
, ISO JTC 1 SC22 and
The Open Group The Open Group is a global consortium that seeks to "enable the achievement of business objectives" by developing "Open-source model, open, vendor-neutral technology standards and certifications." It has over 840 member organizations and provides ...
. If an operating system is submitted to The Open Group for certification, and passes conformance tests, then it is deemed to be compliant with a UNIX standard such as UNIX 98 or UNIX 03. Very few
BSD The Berkeley Software Distribution (BSD) is a discontinued based on , developed and distributed by the (CSRG) at the . The term "BSD" commonly refers to its descendants, including , , , and . BSD was initially called Berkeley Unix because it ...

BSD
and
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Linux
-based operating systems are submitted for compliance with the Single UNIX Specification, although system developers generally aim for compliance with
POSIX The Portable Operating System Interface (POSIX) is a family of standard Standard may refer to: Flags * Colours, standards and guidons * Standard (flag), a type of flag used for personal identification Norm, convention or requirement * Sta ...
standards, which form the core of the Single UNIX Specification.


History


1980s: Motivation

The SUS emerged from a mid-1980s project to standardize
operating system An operating system (OS) is system software System software is software designed to provide a platform for other software. Examples of system software include operating systems like macOS macOS (; previously Mac OS X and later ...

operating system
interface Interface or interfacing may refer to: Academic journals * Interface (journal), ''Interface'' (journal), by the Electrochemical Society * ''Interface, Journal of Applied Linguistics'', now merged with ''ITL International Journal of Applied Lin ...
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.


1988: POSIX

In 1988, these standards became IEEE 1003 (also registered as
ISO The International Organization for Standardization (ISO ) is an international standard An international standard is a technical standard A technical standard is an established norm (social), norm or requirement for a repeatable technical task w ...
/
IECIEC may refer to: Businesses and organisations * International Electrotechnical Commission The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organizati ...
9945), or
POSIX The Portable Operating System Interface (POSIX) is a family of standard Standard may refer to: Flags * Colours, standards and guidons * Standard (flag), a type of flag used for personal identification Norm, convention or requirement * Sta ...
, which loosely stands for Portable Operating System Interface.


1990s: Spec 1170

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 450px, Unix genealogy tree 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. Origins Although AT&T Corporation created Unix, by the ...
. 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. Management over these specifications was assigned to
X/OpenX/Open Company, Ltd., originally the Open Group for Unix Systems, was a consortium founded by several European UNIX systems manufacturers in 1984 to identify and promote open standards in the field of information technology. More specifically, the or ...
who also received the
Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser Multi-user software is computer software Software is a collection of Instruction (computer science), instructions and data (computing), data that tell a computer how to ...

Unix
trademark from
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Novell
in 1993.
Unix InternationalUnix International (UI) was an association created in 1988 to promote open standards, especially the Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser Multi-user software is computer software Software is a collectio ...
(UI) merged into
Open Software Foundation The Open Software Foundation (OSF) was a not-for-profit industry consortium for creating an open standard An open standard is a standard that is publicly available and has various rights to use associated with it and may also have various properti ...
(OSF) in 1994 only to merge with X/Open to form
The Open Group The Open Group is a global consortium that seeks to "enable the achievement of business objectives" by developing "Open-source model, open, vendor-neutral technology standards and certifications." It has over 840 member organizations and provides ...
in 1996.


1994: Single UNIX Specification

This was a repackaging of the
X/Open Portability GuideX/Open Company, Ltd., originally the Open Group for Unix Systems, was a consortium founded by several European UNIX systems manufacturers in 1984 to identify and promote open standards in the field of information technology. More specifically, the or ...
(XPG), Issue 4, Version 2.


1995 Edition

In 1995, the Open Group released the Single UNIX Specification Version 1, 1995 Edition. This specification consisted of: *System Interface Definitions, Issue 4, Version 2, *System Interfaces and Headers, Issue 4, Version 2, *Commands and Utilities, Issue 4, Version 2, *X/Open Curses, Issue 4 Version 2, *Networking Services, Issue 4, and was at the core of the UNIX 95 brand.


1997: Single UNIX Specification version 2

In 1997, the Open Group released the Single UNIX Specification Version 2. This specification consisted of: * the Base Definitions, Issue 5, * the System Interfaces and Headers, Issue 5, * the Commands and Utilities, Issue 5, * the Networking Services, Issue 5, * the X/Open Curses, Issue 4, Version 2, and was at the core of the UNIX 98 brand.


2001: Single UNIX Specification version 3, POSIX:2001

Beginning in 1998, a joint
working group A working group, or working party, is a group of experts working together to achieve specified goals. The groups are domain-specific and focus on discussion or activity around a specific subject area. The term can sometimes refer to an interdisc ...

working group
known as the
Austin Group The Austin Group or the Austin Common Standards Revision Group is a joint technical working groupWorking Group may refer to: * Working group, an interdisciplinary group of researchers; or * Working Group (dogs), kennel club designation for certain ...
began to develop the combined standard that would be known as the Single UNIX Specification Version 3 and as POSIX:2001 (formally: IEEE Std 1003.1-2001). It was released on January 30, 2002. This standard consisted of: * the Base Definitions, Issue 6, * the System Interfaces and Headers, Issue 6, * the Commands and Utilities, Issue 6, and is at the core of the UNIX 03 brand.


2004: POSIX:2004

In 2004, a new edition of the POSIX:2001 standard was released, incorporating two technical corrigenda. It is called POSIX:2004 (formally: IEEE Std 1003.1-2004).


2008: Single UNIX Specification version 4, POSIX:2008

In December 2008, the
Austin Group The Austin Group or the Austin Common Standards Revision Group is a joint technical working groupWorking Group may refer to: * Working group, an interdisciplinary group of researchers; or * Working Group (dogs), kennel club designation for certain ...
published a new major revision, known as POSIX:2008 (formally: IEEE Std 1003.1-2008). This is the core of the Single UNIX Specification, Version 4 (SUSv4). This standard consists of: * the Base Definitions, Issue 7, * the System Interfaces and Headers, Issue 7, * the Commands and Utilities, Issue 7.


2013 Edition

The Technical Corrigendum 1 is mostly targeting internationalization and it introduces a role-based access model. It was published in 2012 for the Unix Base specification and it is registered as the 2013 Edition of POSIX 2008. A trademark ''UNIX V7'' (not to be confused with V7 UNIX, the version of
Research Unix The term "Research Unix" refers to early versions of the Unix operating system for PDP-7, DEC PDP-7, PDP-11, VAX and Interdata 7/32 and 8/32 computers, developed in the Bell Labs Computing Sciences Research Center (CSRC). History The term ''Res ...
from 1979) has been created to mark compliance with SUS Version 4.


2016 Edition

The Technical Corrigendum 2 has been published in September 2016, leading into ''IEEE Std 1003.1-2008, 2016 Edition'' and ''Single UNIX Specification, Version 4, 2016 Edition''.


2018 Edition

In January 2018 an "administrative rollup" edition, susv4-2018, was released. It incorporates Single UNIX Specification version 4 TC1 and TC2, and is technically identical to the 2016 edition.


Specification

SUSv3 totals some 3700 pages, which are divided into four main parts: * Base Definitions (XBD) - a list of definitions and conventions used in the specifications and a list of C header files which must be provided by compliant systems. 84 header files in total are provided. * Shell and Utilities (XCU) - a list of utilities and a description of the shell, sh. 160 utilities in total are specified. * System Interfaces (XSH) - contains the specification of various functions which are implemented as
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s or
library A library is a collection of materials, books or media that are easily accessible for use and not just for display purposes. It is responsible for housing updated information in order to meet the user's needs on a daily basis. A library provid ...
functions. 1123 system interfaces in total are specified. * Rationale (XRAT) - the explanation behind the standard. The standard user command line and scripting interface is the
POSIX The Portable Operating System Interface (POSIX) is a family of standard Standard may refer to: Flags * Colours, standards and guidons * Standard (flag), a type of flag used for personal identification Norm, convention or requirement * Sta ...
shell, an extension of the
Bourne Shell The Bourne shell (sh) is a shell Shell may refer to: Architecture and design * Shell (structure)A shell is a type of structural element which is characterized by its geometry, being a three-dimensional solid whose thickness is very small when c ...
based on an early version of the
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. Other user-level programs, services and utilities include
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,
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, ed,
vi
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, and hundreds of others. Required program-level services include basic
I/O In computing, input/output (I/O, or informally io or IO) is the communication between an information processing system, such as a computer, and the outside world, possibly a human or another information processing system. Information, Inputs are t ...
(
file File or filing may refer to: Mechanical tools and processes * File (tool) A file is a tool used to remove fine amounts of material from a workpiece. It is common in woodworking, metalworking, and other similar trade and hobby tasks. Most are ...
, terminal, and
network Network, networking and networked may refer to: Science and technology * Network theory Network theory is the study of Graph (discrete mathematics), graphs as a representation of either symmetric relations or directed graph, asymmetric relat ...
) services. A test suite accompanies the standard. It is called PCTS or the POSIX Certification Test Suite. Additionally, SUS includes
CURSES A curse (also called an imprecation, malediction, hex, execration, malison, anathema, or commination) is any expressed wish that some form of adversity or misfortune will befall or attach to one or more persons, a place, or an object. In particu ...
(XCURSES) specification, which specifies 372 functions and 3 header files. All in all, SUSv3 specifies 1742 interfaces. Note that a system need not include
source code In , source code is any collection of code, with or without , written using a ''human-readable'' , usually as . The source code of a program is specially designed to facilitate the work of computer s, who specify the actions to be performed ...

source code
derived in any way from AT&T Unix to meet the specification. For instance,
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IBM
OS/390 OS/390 is an International Business Machines, IBM operating system for the System/390 IBM mainframes, IBM mainframe computers. Overview OS/390 was introduced in late 1995 in an effort to simplify the packaging and ordering for the key, entitled e ...
, now
z/OS z/OS is a 64-bit In computer architecture In computer engineering Computer engineering (CoE or CpE) is a branch of engineering Engineering is the use of scientific method, scientific principles to design and build machines, ...
, qualifies as a "Unix" despite having no code in common.


Marks for compliant systems

There are five official marks for conforming systems: * UNIX 93 * UNIX 95 - the mark for systems conforming to version 1 of the SUS * UNIX 98 - the mark for systems conforming to version 2 of the SUS * UNIX 03 - the mark for systems conforming to version 3 of the SUS * UNIX V7 - the mark for systems conforming to version 4 of the SUS (including Corrigenda)


Compliance


Currently registered UNIX systems


AIX

AIX AIX (Advanced Interactive eXecutive, pronounced , “ay-eye-ex”), is a series of proprietary Unix operating systems developed and sold by IBM for several of its computer platforms. Originally released for the IBM RT PC RISC A reduc ...
version 7, at either 7.1 TL5 (or later) or 7.2 TL2 (or later) are registered as UNIX 03 compliant. AIX version 7, at 7.2 TL5 (or later) are registered as UNIX V7 compliant.


EulerOS

EulerOS EulerOS is a commercial Linux distribution A Linux distribution (often abbreviated as distro) is an operating system An operating system (OS) is system software that manages computer hardware, computer software, software resources, and provide ...
2.0 for the
x86-64 x86-64 (also known as x64, x86_64, AMD64, and Intel 64) is a 64-bit In computer architecture In computer engineering Computer engineering (CoE or CpE) is a branch of engineering Engineering is the use of scientific method, ...
architecture is registered as UNIX 03 compliant. The UNIX 03 conformance statement shows that the standard C compiler is from the
GNU Compiler Collection The GNU Compiler Collection (GCC) is an optimizing compiler In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes a ...
(), and that the system is a
Linux distribution A Linux distribution (often abbreviated as distro) is an operating system An operating system (OS) is system software that manages computer hardware, computer software, software resources, and provides common daemon (computing), services for c ...
of the
Red Hat Red Hat, Inc. is an American that provides products to enterprises. Founded in 1993, Red Hat has its corporate headquarters in , with other offices worldwide. Red Hat has become associated to a large extent with its enterprise operating sys ...
family.


HP-UX

HP-UX HP-UX (from "Hewlett Packard Unix") is Hewlett Packard Enterprise The Hewlett Packard Enterprise Company (HPE) is an American multinational enterprise information technology company based in Houston, Texas Texas (, ) is a sta ...
11i V3 Release B.11.31 is registered as UNIX 03 compliant. Previous releases were registered as UNIX 95. HP-UX 11i features also provide partial conformance to the UNIX 98 specification.


macOS

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macOS macOS (; previously Mac OS X and later OS X) is a proprietary {{Short pages monitor