Unix-like definition by The Linux Information Project (LINFO)
Unix-like Definition
The term Unix-like is widely used to describe
that share many of the characteristics of the original , which was written in 1969 by
at , and its early successors.
The popularity of this term is mainly due to the fact that it is a very convenient and logical way of describing the numerous and diverse operating systems that fit into this category. It is also due in part to the controversy about what really is UNIX and how this term should be used. This controversy, in turn, has arisen largely as a result of the complex history of UNIX and the operating systems that have been based on it.
The category of Unix-like operating systems clearly includes those systems that have all three of the following characteristics: a direct
lineage from the original UNIX, obvious UNIX characteristics and officially describe themselves as being UNIX. Source code is the version of
as it is originally written (i.e., typed into a computer) by a human in
(i.e., human readable numeric ). Such systems include AIX (developed by IBM), HP-UX (developed by HP), IRIX (developed by Silicon Graphics), Solaris (developed by Sun Microsystems) and True64 (developed by Compaq for alpha processors and now owned by HP).
The category of Unix-like operating systems also includes UNIX . A clone is a
(i.e., an operating system or an ) that has functions and behavior similar to another program but which does not contain source code from that program.
The functions and behavior of the UNIX clones are so similar to those of the early (and later) versions of UNIX, in fact, that many knowledgeable users consider them to be UNIX. However, they do not have a direct lineage to the original UNIX source code, and most of them do not officially describe themselves as being UNIX. This category includes the BSDs (i.e., FreeBSD, NetBSD, OpenBSD and Darwin), , , QNX and Cygwin.
Unix-like operating systems also generally contain most or all of the enhancements and new features that were subsequently added at the University of California at Berkeley (UCB) and which are known as the Berkeley extensions. The Berkeley extensions include such now nearly universal innovations as the
, also referred to as csh,
(transmission control protocol/Internet protocol), which forms the basis for both the
and most local , , which allows a
(HDD) to simulate additional main , and the
. Thus, it has been suggested that operating systems that refer to themselves as UNIX might more appropriately call themselves something such as UNIX/Berkeley.
BSD (Berkeley Software Distribution), the version of UNIX developed at UCB in the 1970s and early 1980s, was widely considered to be a type of UNIX, as are its modern day descendants. In fact, BSD even included UNIX in its name, such as BSD UNIX 4.0, which was released in October 1980.
The original name for the operating system developed at Bell Labs was UNIX (all upper case). This term became a trademark that was eventually acquired by , an industry consortium that was formed in 1996. The Open Group attempts to permit operating systems to call themselves UNIX only if they both conform to its Single UNIX Specification and pay a substantial fee (which is one of its main sources of revenue). Thus, at least theoretically, an operating system would not have to contain any of the original UNIX source code or bear much superficial resemblance to the original UNIX to be permitted to call itself UNIX.
Adding to the complexity of the situation is the fact that there is some controversy as to whether the term UNIX is actually a valid trademark. This is because trademark law states that when a term becomes very widely used as a generic term (i.e., a term that describes a class of products rather than just a single brand) it can lose its legally protected trademark status.
Apple Computer, which uses Darwin (a Unix-like operating system based on BSD) as the core of its increasingly popular Mac OS X operating system, claims that the term UNIX has become generic and thus that it is not a legally valid trademark. Apple has vastly greater legal and financial resources than the BSDs or most of the Linux
(i.e., versions), and thus it is not afraid to call its operating system UNIX. In fact, it makes a number of statements on its website explicitly referring to itself as UNIX (and not as Unix-like), including the following: "Don't let its elegant and easy-to-use interface fool you. Beneath the surface of Mac OS X lies an industrial-strength UNIX foundation hard at work to ensure that your computing experience remains free of system crashes and compromised performance."
As a result, the Open Group is suing Apple Computer for alleged trademark violation. This is a necessary move for the Open Group, as attempting to protect a trademark from abuse can be an important factor in legal decisions about the validity of the trademark. However, some industry observers expect that this case will be settled quietly out of court because neither side wants to risk a negative judgment1.
The BSD operating systems are widely regarded as
(both in a monetary sense and with regard to use) implementations of UNIX, and thus as UNIX. However, in contrast to Apple, they make a point of not referring to themselves as being UNIX on their websites or other materials in order to avoid potentially costly legal problems. For example, FreeBSD, the most popular of the BSD systems (at least until the recent rise of Darwin), describes itself as being " . . . a very economical alternative to commercial UNIX® workstations." NetBSD describes itself on its homepage as " . . . a free, secure, and highly portable Unix-like Open Source operating system available for many platforms, . . . " OpenBSD describes itself as " . . . a FREE, multi-platform 4.4BSD-based UNIX-like operating system."
Some operating systems do not seek UNIX branding because the royalties would be prohibitively expensive for them due to the facts that they are updated frequently (which would require costly recertification) and that they are made available freely over the Internet. Moreover, developers of such systems generally feel that such branding would not provide any significant advantage, as their users are generally well informed and are interested in the intrinsic values of the systems rather than in their names.
The term Unix-like does not have any negative implication about the validity of the UNIX trademark. In fact, it could even be argued that it supports the trademark by providing a convenient term for describing operating systems that resemble the original UNIX and its early successors so that they, and their users, will not be tempted to inappropriately use the term UNIX.
Other terminology is also sometimes used to refer to Unix-like operating systems, particularly UN*X, Un*x, *NIX and *nix.
1An excellent summary of this dispute is provided by the article , OSViews, April 2005.
Created April 19, 2005. Updated June 18, 2006.
Copyright © 2005 - 2006 The Linux Information Project. All Rights Reserved.Unix-like系统关系图大全_运维之美_传送门
Unix-like系统关系图大全
音乐资源加载中...类Unix系统(英语：Unix-like)经常被称为un*x，ux，或nix，指各种的派生系统。比如、、公司的，以及各种与传统Unix类似的系统。例如：、、等。它们虽然有的是，有的是，但都相当程度地继承了原始UNIX的特性，有许多相似处，并且都在一定程度上遵守规范。UNIX的商标权由所拥有，只有匹配的UNIX系统才能使用UNIX这个名称，否则只能称为类UNIX(UNIX-like)。注：点击图片查看高清大图，文末有福利！类UNIX操作系统的相互关系图Unix操作系统的进化史Unix家族系谱图Linux各版本血缘关系GNU/Linux发行版时间线最新的GNU/Linux发行版时间线(GNU/Linux distro timeline 12.10)包含了从1992年至今几乎所有的发行版,大家可以从这张图上详细看看linux的各个发行版的发行时间状况。缩略图(图片太大不能上传)后台回复关键词:「Unix」，获取高清版关系图合集下载地址。
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