By Vangie Beal
UNIX is a multi-user, multitasking operating system (OS) that was developed at AT&T Bell Labs in the late 1960s. It was designed to be used exclusively by programmers and became a leading operating system for workstations because of its portability, flexibility, and power. Historically, it has been less popular in the personal computer market than professional settings, but numerous UNIX distributions like FreeBSD, Linux, and macOS brought UNIX principles into the mainstream.
- A kernel, which is the source code that includes configuration, device drivers, file structures, memory management, system calls, etc.
- A development environment, which allows users to recreate the entire system from source code
- Documentation, including manual pages and larger files that detail major subsystems
- Commands, which allow users to navigate the operating system and perform specific actions, as well as maintenance and general utility applications
UNIX commands are numerous and case-sensitive. Some basic commands include:
- ls (lists files)
- mv (rename or move files)
- cd (changes directory)
- mkdir (creates new directory)
- history (shows history of previous commands)
Not all UNIX commands are universal, so some are specific to the device on which UNIX is being used. This list contains more examples of basic commands and how they are used.
History of UNIX
UNIX was created by a small team of programmers that was led by Ken Thompson and Dennis Ritchie. It was one of the first operating systems to be written in the C programming language, which meant that it could be installed on virtually any computer in which a C compiler existed. This natural portability combined with its low price made it a popular choice among universities. However, antitrust regulations prohibited Bell Labs from marketing it as a full-scale product, so it was generally regarded as more expensive than competing operating systems.
Bell Labs distributed the operating system in its source language form, so anyone who obtained a copy could modify and customize it for their unique needs. By the end of the 1970s, dozens of UNIX derivatives were running at various sites. After its government-mandated breakup in 1982, AT&T began to market UNIX in earnest. It also began the long and arduous process of defining a standard version of UNIX.
Today, the trademarked “UNIX” and the “Single UNIX Specification” interface are owned by The Open Group. An operating system that is certified by The Open Group to use the UNIX trademark conforms to the Single UNIX Specification. The specification is updated every few years to certify new UNIX derivatives that are aligned with UNIX V7, the last version of UNIX that was released in 1979.
Regarding implementation of the UNIX trademark, The Open Group released the following statement in a 2003 press release:
“As the owner of the UNIX trademark, The Open Group has separated the UNIX trademark from any actual code stream itself, thus allowing multiple implementations. Since the introduction of the Single UNIX Specification, there has been a single, open, consensus specification that defines the requirements for a conformant UNIX system. There is also a mark, or brand, that is used to identify those products that have been certified as conforming to the Single UNIX Specification, initially UNIX 93, followed subsequently by UNIX 95, UNIX 98 and now UNIX 03. Both the specification and the UNIX trademark are managed and held in trust for the industry by The Open Group.”
UNIX vs. Linux
Although Linux is not a direct derivative of UNIX, it was born out of the desire for an open source alternative to UNIX and leverages several BSD components. Today’s Linux distributions originated in the early 1990s with Richard Stallman’s GNU (“GNU’s Not Unix!”) project. Stallman wanted to create an operating system that was adjacent to the proprietary UNIX but was widely available and free to use. However, this proved to be an implementation challenge without a dedicated kernel.
Linus Torvald’s Linux kernel combined GNU components with open source BSD components and MIT’s X Window System to bring Linux distributions to life as they’re known today. The open source nature of Linux operating systems has spurred hundreds of unique distributions that are popular for personal and commercial use alike.
Some practical differences between UNIX and Linux systems are distinct:
|Source model||Open source||Usually proprietary (some distributions are open source)|
|License type||Public license||Proprietary license|
|Cost||Usually free (some distributions are paid)||Usually more expensive (some distributions are free or device-dependent)|
|Standard||No current standardization||Single UNIX Specification|
|Kernel approach||Monolithic||Monolithic, microkernel, or hybrid|
|Default shell||BASH (Bourne Again Shell)||Bourne Shell|
|Threat recognition and resolution speed||Faster (community-based)||Slower (patch dependent)|
|Intended use||Personal or professional||Professional|
|Distribution examples||Ubuntu, Fedora, Red Hat, Android||Solaris, HP-UX, macOS|