Unix-like

Last updated

Evolution of Unix and Unix-like systems, starting in 1969 Unix history-simple.svg
Evolution of Unix and Unix-like systems, starting in 1969

A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-like application is one that behaves like the corresponding Unix command or shell. Although there are general philosophies for Unix design, there is no technical standard defining the term, and opinions can differ about the degree to which a particular operating system or application is Unix-like.

Contents

Some well-known examples of Unix-like operating systems include Linux and BSD. These systems are often used on servers as well as on personal computers and other devices. Many popular applications, such as the Apache web server and the Bash shell, are also designed to be used on Unix-like systems.

One of the key features of Unix-like systems is their ability to support multiple users and processes simultaneously. This allows users to run multiple programs at the same time and to share resources such as memory and disk space. This is in contrast to many older operating systems, which were designed to only support a single user or process at a time. Another important feature of Unix-like systems is their modularity. This means that the operating system is made up of many small, interchangeable components that can be added or removed as needed. This makes it easy to customize the operating system to suit the needs of different users or environments.

Definition

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 a 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. [1]

Other parties frequently treat "Unix" as a genericized trademark. Some add a wildcard character to the name to make an abbreviation like "Un*x" [2] or "*nix", since Unix-like systems often have Unix-like names such as AIX, A/UX, HP-UX, IRIX, Linux, Minix, Ultrix, Xenix, and XNU. These patterns do not literally match many system names, but are still generally recognized to refer to any UNIX system, descendant, or work-alike, even those with completely dissimilar names such as Darwin/macOS, illumos/Solaris or FreeBSD.

In 2007, Wayne R. Gray sued to dispute the status of UNIX as a trademark, but lost his case, and lost again on appeal, with the court upholding the trademark and its ownership. [3] [4]

History

Simplified history of Unix-like operating systems Unix timeline.en.svg
Simplified history of Unix-like operating systems

"Unix-like" systems started to appear in the late 1970s and early 1980s. Many proprietary versions, such as Idris (1978), UNOS (1982), Coherent (1983), and UniFlex (1985), aimed to provide businesses with the functionality available to academic users of UNIX.

When AT&T allowed relatively inexpensive commercial binary sublicensing of UNIX in 1979, a variety of proprietary systems were developed based on it, including AIX, HP-UX, IRIX, SunOS, Tru64, Ultrix, and Xenix. These largely displaced the proprietary clones. Growing incompatibility among these systems led to the creation of interoperability standards, including POSIX and the Single UNIX Specification.

Various free, low-cost, and unrestricted substitutes for UNIX emerged in the 1980s and 1990s, including 4.4BSD, Linux, and Minix. Some of these have in turn been the basis for commercial "Unix-like" systems, such as BSD/OS and macOS. Several versions of (Mac) OS X/macOS running on Intel-based Mac computers have been certified under the Single UNIX Specification. [5] [6] [7] [8] [9] [10] [11] The BSD variants are 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 the AT&T code. Since the BSD variants are not certified as compliant with the Single UNIX Specification, they are referred to as "UNIX-like" rather than "UNIX".

Categories

Dennis Ritchie, one of the original creators of Unix, expressed his opinion that Unix-like systems such as Linux are de facto Unix systems. [12] Eric S. Raymond and Rob Landley have suggested that there are three kinds of Unix-like systems: [13]

Genetic UNIX

Those systems with a historical connection to the AT&T codebase. Most commercial UNIX systems fall into this category. So do the BSD systems, which are 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, although Apple macOS 10.5 and later is a BSD variant that has been certified, and EulerOS and Inspur K-UX are Linux distributions that have been certified. A few other systems (such as IBM 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, including having a "program which manages your login and command line sessions"; [14] 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, which costs thousands of dollars. [15]

Around 2001 Linux was given the opportunity to get a certification including free help from the POSIX chair Andrew Josey for the symbolic price of one dollar.[ citation needed ] There have been some activities to make Linux POSIX-compliant, with Josey having prepared a list of differences between the POSIX standard and the Linux Standard Base specification, [16] but in August 2005, this project was shut down because of missing interest at the LSB work group.[ citation needed ]

Compatibility layers

Some non-Unix-like operating systems provide a Unix-like compatibility layer, with varying degrees of Unix-like functionality.

Other means of Windows-Unix interoperability include:

See also

Related Research Articles

<span class="mw-page-title-main">Minix</span> Unix-like operating system

MINIX is a Unix-like operating system based on a microkernel architecture. Since version 2.0, it has been POSIX compliant.

The Portable Operating System Interface is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines both the system and user-level application programming interfaces (APIs), along with command line shells and utility interfaces, for software compatibility (portability) with variants of Unix and other operating systems. POSIX is also a trademark of the IEEE. POSIX is intended to be used by both application and system developers.

The Single UNIX Specification (SUS) is a standard for computer operating systems, compliance with which is required to qualify for using the "UNIX" trademark. The standard specifies programming interfaces for the C language, a command-line shell, and user commands. The core specifications of the SUS known as Base Specifications are developed and maintained by the Austin Group, which is a joint working group of IEEE, ISO/IEC JTC 1/SC 22/WG 15 and The Open Group. 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.

Darwin is the core Unix-like operating system of macOS, iOS, watchOS, tvOS, iPadOS, audioOS, visionOS, and bridgeOS. It previously existed as an independent open-source operating system, first released by Apple Inc. in 2000. It is composed of code derived from NeXTSTEP, FreeBSD, other BSD operating systems, Mach, and other free software projects' code, as well as code developed by Apple.

pwd Directory information command on various operating systems

In Unix-like and some other operating systems, the pwd command writes the full pathname of the current working directory to the standard output.

<span class="mw-page-title-main">A/UX</span> Early Unix-based operating system from Apple Computer

A/UX is a Unix-based operating system from Apple Computer for Macintosh computers, integrated with System 7's graphical interface and application compatibility. It is Apple's first official Unix-based operating system, launched in 1988 and discontinued in 1995 with version 3.1.1. A/UX requires select 68k-based Macintosh models with an FPU and a paged memory management unit (PMMU), including the Macintosh II, SE/30, Quadra, and Centris series.

uname Standard UNIX utility that prints name and other details about the machine

uname is a computer program in Unix and Unix-like computer operating systems that prints the name, version and other details about the current machine and the operating system running on it.

<span class="mw-page-title-main">UNIX System V</span> Early commercial UNIX operating system

Unix System V is one of the first commercial versions of the Unix operating system. It was originally developed by AT&T and first released in 1983. Four major versions of System V were released, numbered 1, 2, 3, and 4. System V Release 4 (SVR4) was commercially the most successful version, being the result of an effort, marketed as Unix System Unification, which solicited the collaboration of the major Unix vendors. It was the source of several common commercial Unix features. System V is sometimes abbreviated to SysV.

In computer networking, STREAMS is the native framework in Unix System V for implementing character device drivers, network protocols, and inter-process communication. In this framework, a stream is a chain of coroutines that pass messages between a program and a device driver. STREAMS originated in Version 8 Research Unix, as Streams.

<span class="mw-page-title-main">Tanenbaum–Torvalds debate</span> 1990s debate regarding the Linux kernel

The Tanenbaum–Torvalds debate was a written debate between Andrew S. Tanenbaum and Linus Torvalds, regarding the Linux kernel and kernel architecture in general. Tanenbaum, the creator of Minix, began the debate in 1992 on the Usenet discussion group comp.os.minix, arguing that microkernels are superior to monolithic kernels and therefore Linux was, even in 1992, obsolete. The debate has sometimes been considered a flame war.

<span class="mw-page-title-main">Minix 3</span> Unix-like operating system

Minix 3 is a small, Unix-like operating system. It is published under a BSD-3-Clause license and is a successor project to the earlier versions, Minix 1 and 2.

<span class="mw-page-title-main">Linux</span> Family of Unix-like operating systems

Linux is a generic name for a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution (distro), which includes the kernel and supporting system software and libraries, many of which are provided by the GNU Project.

Linux began in 1991 as a personal project by Finnish student Linus Torvalds to create a new free operating system kernel. The resulting Linux kernel has been marked by constant growth throughout its history. Since the initial release of its source code in 1991, it has grown from a small number of C files under a license prohibiting commercial distribution to the 4.15 version in 2018 with more than 23.3 million lines of source code, not counting comments, under the GNU General Public License v2 with a syscall exception meaning anything that uses the kernel via system calls are not subject to the GNU GPL.

<span class="mw-page-title-main">Microsoft POSIX subsystem</span> Subsystem shipped with the first versions of Windows NT

Microsoft POSIX subsystem is one of four subsystems shipped with the first versions of Windows NT, the other three being the Win32 subsystem which provided the primary API for Windows NT, plus the OS/2 and security subsystems.

<span class="mw-page-title-main">Unix</span> Family of computer operating systems

Unix is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and others.

<span class="mw-page-title-main">NetBSD</span> Free and open-source Unix-like operating system

NetBSD is a free and open-source Unix-like operating system based on the Berkeley Software Distribution (BSD). It was the first open-source BSD descendant officially released after 386BSD was forked. It continues to be actively developed and is available for many platforms, including servers, desktops, handheld devices, and embedded systems.

Comparison of user features of operating systems refers to a comparison of the general user features of major operating systems in a narrative format. It does not encompass a full exhaustive comparison or description of all technical details of all operating systems. It is a comparison of basic roles and the most prominent features. It also includes the most important features of the operating system's origins, historical development, and role.

References

  1. ↑ "Legal: Trademark Guidelines". The Open Group. Archived from the original on October 2, 2013. Retrieved November 4, 2013.
  2. ↑ Eric S. Raymond; Guy L. Steele Jr. "UN*X". The Jargon File . Retrieved January 22, 2009.
  3. ↑ Gray v. Novell, X/Open Company, The SCO Group(11th Cir.January 7, 2011), Text .
  4. ↑ "More Wayne Gray. No! Again? Still?! Yes. He Wants to Reopen Discovery in the USPTO Dispute". Groklaw . April 22, 2011. Archived from the original on June 18, 2022. Retrieved September 26, 2022.
  5. ↑ "Mac OS X Version 10.5 on Intel-based Macintosh computers". The Open Group. Retrieved December 4, 2014.
  6. ↑ "Mac OS X Version 10.6 on Intel-based Macintosh computers". The Open Group. Retrieved December 4, 2014.
  7. ↑ "Mac OS X Version 10.8 on Intel-based Macintosh computers". The Open Group. Retrieved December 4, 2014.
  8. ↑ "OS X Version 10.9 on Intel-based Macintosh computers". The Open Group. Retrieved December 4, 2014.
  9. ↑ "OS X version 10.10 Yosemite on Intel-based Mac computers". The Open Group. Retrieved October 23, 2015.
  10. ↑ "OS X version 10.11 El Capitan on Intel-based Mac computers". The Open Group. Retrieved October 23, 2015.
  11. ↑ "macOS version 10.12 Sierra on Intel-based Mac computers". The Open Group. Retrieved October 13, 2016.
  12. ↑ Interview with Dennis M. Ritchie Manuel Benet, LinuxFocus, July 1999
  13. ↑ The meaning of 'Unix' Eric Raymond and Rob Landley, OSI Position Paper on the SCO-vs.-IBM Complaint
  14. ↑ "Introduction to UNIX – Part 1: Basic Concepts". Archived from the original on April 5, 2018. Retrieved April 4, 2014.
  15. ↑ "The Open Brand Fee Schedule". The Open Group. November 6, 2003. Retrieved July 22, 2022.
  16. ↑ Andrew Josey (August 20, 2005). "Conflicts between ISO/IEC 9945 (POSIX) and the Linux Standard Base". The Open Group. Retrieved July 23, 2012.
  17. ↑ "What is the Windows Subsystem for Linux?". Microsoft Docs. July 18, 2023.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.