Unix-like

Information about Unix-like

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Diagram of the relationships between several Unix-like systems


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. The term can include free software / open source operating systems inspired by Bell Labs’ Unix or designed to emulate its features, commercial and proprietary work-alikes, and even versions based on the licensed UNIX source code (which may be deemed so “Unix-like” that they are certified to bear the “UNIX” trademark). There is no formal standard for defining the term, and some difference of opinion is possible as to whether a certain OS is “Unix-like” or not.

The term “Unix-like” and the UNIX trademark

The Open Group owns the UNIX® trademark and administers the Single UNIX Specification, with the “UNIX” name being used as a certification mark. They do not approve of the construction “Unix-like”, and consider it misuse of their trademark. Their guidelines require “UNIX” to be presented in uppercase or otherwise distinguished from the surrounding text, strongly encourage using it as a branding adjective for a generic word such as “system”, and discourage its use in hyphenated phrases. The closest phrase they consider correct is “UNIX system-like”.[1]

Other parties frequently treat “Unix” as a genericised trademark, in much the same way that “Band-Aid” is used in reference to any bandage or “Xerox” to any photocopier. Some add a wildcard character to the name to make a euphemistic abbreviation like “Un*x” or “*nix” (the latter pronounced as "asternix", a play on the asterisk used for the wildcard), since Unix-like systems often have Unix-like names such as AIX, HP-UX, IRIX, Linux, Minix, Ultrix, and Xenix. These patterns do not literally match many system names, but are still generally recognized to refer to any UNIX descendant system, even those with completely dissimilar names such as Solaris, FreeBSD or Mac OS X. This is still contrary to Open Group guidelines.

As of 2007 there is an active legal battle between Wayne R. Gray and Open Group that centers on the use of UNIX as a trademark.[2] Trademark Trial and Appeal Board court documents indicate that Gray’s legal team is seeking for the Open Group to provide documentation for their trademark claim.

Categories

Dennis Ritchie, one of the original creators of UNIX, has expressed his opinion that Unix-like systems such as Linux are de facto UNIX systems. Eric S. Raymond has suggested that there are three kinds of Unix-like systems:
  • Genetic UNIX: Those systems with a historical connection to the AT&T codebase. Most but not all commercial UNIX systems fall into this category, as do the BSD systems, descendants of work done at the University of California, Berkeley in the late 1970s and early 1980s. Some of these systems have no original AT&T code but can still trace their ancestry to AT&T designs.
  • Trademark or Branded UNIX: These systems—largely commercial in nature—have been determined by the Open Group to meet the Single UNIX Specification and are allowed to carry the UNIX® name. Most such systems are commercial derivatives of the System V code base in one form or another, though a few (such as IBM's z/OS) earned the trademark through a POSIX compatibility layer and are not otherwise inherently Unix systems. Many Ancient UNIX Systems no longer meet this definition.
  • Functional UNIX: Broadly, any Unix-like system that behaves in a manner roughly consistent with the UNIX specification; more specifically, this can refer to systems such as Linux or Minix that behave similarly to a UNIX system but have no genetic or trademark connection to the AT&T code base. Most free/open-source implementations of the UNIX design, whether Genetic Unix or not, fall into the restricted definition of this third category due to the expense of obtaining Open Group certification.

Development of Unix-like systems

“Unix-like” systems started to appear in the late ’70s and early ’80s. Many proprietary versions, such as Idris (1978), Coherent (1983), and UniFlex (1985), aimed to provide businesses with the functionality available to academic users of UNIX.

When AT&T later allowed commercial licensing of UNIX in the 1980s, a variety of proprietary systems were developed based on it, including AIX, HP-UX, IRIX, Solaris, Tru64, Ultrix, and Xenix. These largely displaced the proprietary clones. Growing incompatibility between these systems led to the creation of interoperability standards, including POSIX and the Single UNIX Specification.

Meanwhile, the GNU Project was launched in 1983 with the goal of making GNU, an operating system which all computer users could freely use, study, modify, and redistribute. Various “Unix-like” operating systems developed alongside GNU, frequently sharing substantial components with it (leading to some disagreement about whether they should be called “GNU” or not). These primarily served as low-cost and unrestricted substitutes for UNIX, and include 4.4BSD, Linux, and Minix. Some of these have in turn been the basis for commercial “Unix-like” systems, such as BSD/OS and Mac OS X. Notably, the next release of Mac OS X, Leopard, is certified under the Single UNIX Specification.

The various BSD systems are notable in that they are in fact descendants of UNIX, developed by the University of California at Berkeley with UNIX source code from Bell Labs. However, the BSD code base has evolved since then, replacing all of the AT&T code. Since these operating systems are not certified as compliant with the Single UNIX Specification, they are referred to as "UNIX-'like'".

Current examples

Free software / open source

Most free/open-source Unix-like systems do not seek UNIX branding for their product even if fully or mostly conformant; the costs for certification (especially given frequent release cycles) are generally considered prohibitive. The term Freenix is sometimes used to refer to such systems. Components are often shared between systems, with hybrids possible.

Free of charge & closed source

Proprietary

* UNIX® branded systems

References

1. ^ [1]
2. ^ [2]
3. ^ [3]

See also

External links

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Unix and Unix-like operating systems
A/UX AIX BSD FreeBSD GNU HP-UX IRIX Linux Mac OS X NetBSD NEXTSTEP OpenBSD Plan 9 QNX Research Unix SCO OpenServer SINIX Solaris System V Tru64 Xenix
An operating system (OS) is the software that manages the sharing of the resources of a computer. An operating system processes system data and user input, and responds by allocating and managing tasks and internal system resources as a service to users and programs of the
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Unix (officially trademarked as UNIX®) is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy.
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The Single UNIX Specification (SUS) is the collective name of a family of standards for computer operating systems to qualify for the name "Unix". The SUS is developed and maintained by the Austin Group, based on earlier work by the IEEE and The Open Group.
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Free software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions only to ensure that further recipients can also do these things.
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Open source software is computer software which source code is available under a license (or arrangement such as the public domain) that meets the Open source definition. This permits users to use, change, and improve the software, and to redistribute it in modified or unmodified
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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.
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trademark or trade mark[1] is a distinctive sign or indicator of some kind which is used by an individual, business organization or other legal entity to uniquely identify the source of its products and/or services to consumers, and to distinguish its products or
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A certification mark on a commercial product indicates five things:
  • The existence of a legal follow-up or product certification agreement between the manufacturer

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A genericized trademark, generic trade mark, generic descriptor, or proprietary eponym, is a trademark or brand name that has become the colloquial or generic description for or synonymous with a particular class of product or service.
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Band-Aid is a registered trademark of Johnson & Johnson for their adhesive bandages used to cover small wounds. However, much of the consuming public in the United States, Canada, Brazil and Australia uses the term band-aid
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bandage is a piece of material used either to support a medical device such as a dressing or splint, or on its own to provide support to the body. Bandages are available in a wide range of types, from generic cloth strips, to specialised shaped bandages designed for a specific limb
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Xerox Corporation

Public (NYSE: XRX )
Founded Rochester, New York, USA (1906)
Headquarters Stamford, Connecticut, USA Offices in Rochester, New York

Key people Anne M. Mulcahy, Chairman & CEO
Ursula Burns, President
Larry Zimmerman, CFO
Gary R.
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A photocopier is a machine which makes paper copies of documents and other visual images quickly and cheaply. Most current photocopiers use a technology called xerography, a dry process using heat.
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For other meanings of 'wild card' see wild card.


The term wildcard character has the following meanings:

Telecommunication

In telecommunications, a wildcard character
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'

AIX (Advanced Interactive eXecutive) is the name given to a series of proprietary operating systems sold by IBM for several of its computer system platforms, based on UNIX System V while containing BSD extensions ("r" commands such as rlogin, rcp, rexec, etc.).
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HP-UX (Hewlett Packard UniX) is Hewlett-Packard's proprietary implementation of the Unix operating system, based on System V (initially System III). It runs on their PA-RISC range of processors and Intel's Itanium processor, and was also available for later Apollo/Domain systems.
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IRIX is a computer operating system developed by Silicon Graphics, Inc. (SGI) to run natively on their 32- and 64-bit MIPS architecture workstations and servers. Based on UNIX System V with BSD extensions, it is capable of extremely long uptimes, and its XFS file system is
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Linux (pronunciation: IPA: /ˈlɪnʊks/, lin-uks) is a Unix-like computer operating system. Linux is one of the most prominent examples of free software and open source development; its underlying source code can be
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MINIX is a free/open source, Unix-like operating system (OS) based on a microkernel architecture. Andrew S. Tanenbaum wrote the operating system to be used for educational purposes; MINIX also inspired the creation of the Linux kernel.
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Ultrix (officially all-caps ULTRIX) was the brand name of Digital Equipment Corporation's (DEC) native Unix systems. While ultrix is the Latin word for avenger, the name was chosen solely for its sound.
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Xenix was a version of the Unix operating system, licensed by Microsoft from AT&T in the late 1970s. The Santa Cruz Operation (SCO) later acquired exclusive rights to the software, and eventually began distributing it as SCO UNIX.
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The Solaris Operating System, usually known simply as Solaris, is a computer operating system developed by Sun Microsystems. It is certified against the Single Unix Specification as a version of Unix, and although historically a closed-source product, a majority of
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FreeBSD is a Unix-like free operating system descended from AT&T UNIX via the Berkeley Software Distribution (BSD) branch through the 386BSD and 4.4BSD operating systems.
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Mac OS X (IPA: /mæk.oʊ.ɛs.tɛn/) is a line of graphical operating systems developed, marketed, and sold by Apple Inc., the latest of which is pre-loaded on all currently shipping Macintosh computers.
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Wayne R. Gray is the president of iNUX, Inc. a Florida company that is involved in trademark litigation with X/Open over the UNIX trademark, or certification mark. He has claimed among other things that UNIX is a genericized trademark.
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The Trademark Trial and Appeal Board (or "TTAB") is a body within the United States Patent and Trademark Office (USPTO) responsible for hearing and deciding certain kinds of cases involving trademarks.
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Dennis MacAlistair Ritchie

Born September 9 1941 (1941--) (age 66)
Bronxville, New York
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Linux (pronunciation: IPA: /ˈlɪnʊks/, lin-uks) is a Unix-like computer operating system. Linux is one of the most prominent examples of free software and open source development; its underlying source code can be
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De facto is a Latin expression that means "in fact" or "in practice" but not spelled out by law. It is commonly used in contrast to de jure (which means "by law") when referring to matters of law, governance, or technique (such as standards), that are found in the
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Eric Steven Raymond (born December 4, 1957), often referred to as ESR, is a computer programmer, author and open source software advocate. His reputation within the hacker culture was established when he became the maintainer of the "Jargon File".
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