Screenshot of a sample Bash session, taken on Gentoo Linux.

A Unix shell, also called "the command line", provides the traditional user interface for the Unix operating system and for Unix-like systems. Users direct the operation of the computer by entering command input as text for a shell to execute. Within the Microsoft Windows suite of operating systems the analogous program is command.com, or cmd.exe for Windows NT-based operating systems. Download high resolution version (709x691, 20 KB)Screenshot of a sample session of bash on Linux. ... Download high resolution version (709x691, 20 KB)Screenshot of a sample session of bash on Linux. ... This article is about the Unix shell. ... The Gentoo Linux operating system (pronounced ) is a Linux distribution named after the Gentoo penguin. ... A command line interface or CLI is a method of interacting with a computer by giving it lines of textual commands (that is, a sequence of characters) either from keyboard input or from a script. ... The user interface is the part of a system exposed to users. ... Filiation of Unix and Unix-like systems 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. ... It has been suggested that Maintenance OS be merged into this article or section. ... 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 NASA Columbia Supercomputer. ... To meet Wikipedias quality standards, the lead section of this article may need to be expanded. ... COMMAND.COM is the name for the default operating system shell (or command line interpreter) for DOS and 16/32bits versions of Windows (95/98/98 SE/Me). ... This article needs additional references or sources for verification. ... Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. ...

The most generic sense of the term shell means any program that users use to type commands. Since in the Unix operating system users can select which shell they want to use (which program should execute when they login), many shells have been developed. It is called a "shell" because it hides the details of the underlying operating system behind the shell's interface. (Contrast that (the interface), with the "kernel", which refers to the lowest-level, or 'inner-most' component of an operating system). Similarly, graphical user interfaces for Unix, such as GNOME and KDE, are occasionally called visual shells or graphical shells. By itself, the term shell is usually associated with the command line. In Unix, any program can be the user's shell. Users who want to use a different syntax for typing commands can specify a different program as their shell. In computing, a shell is a piece of software that provides an interface for users (command line interpreter). ... It has been suggested that Maintenance OS be merged into this article or section. ... A kernel connects the application software to the hardware of a computer. ... A graphical user interface (GUI) is a type of user interface which allows people to interact with a computer and computer-controlled devices which employ graphical icons, visual indicators or special graphical elements called widgets, along with text labels or text navigation to represent the information and actions available to... This article needs additional references or sources for verification. ... KDE (K Desktop Environment) (IPA: ) is a free software project which aims to be a powerful system for an easy-to-use desktop environment. ...

The term shell also refers to a particular program, such as the Bourne shell, sh. The Bourne shell was the shell used in early versions of Unix and became a de facto standard; every Unix-like system has at least one shell compatible with the Bourne shell. The Bourne shell program is located in the Unix file hierarchy at /bin/sh. On some systems, such as BSD, /bin/sh is a Bourne shell or equivalent, but on other systems such as Linux, /bin/sh is likely to be a link to a compatible, but more feature-rich shell. POSIX specifies its standard shell as a strict subset of the Korn shell. The Bourne shell, or sh, was the default Unix shell of Unix Version 7, and replaced the Thompson shell, whose executable file had the same name, sh. ... Berkeley Software Distribution (BSD, sometimes called Berkeley Unix) is the Unix derivative distributed by the University of California, Berkeley, starting in the 1970s. ... Linux (IPA pronunciation: ) is a Unix-like computer operating system. ... In computing, a symbolic link (often shortened to symlink and also known as a soft link) consists of a special type of file that serves as a reference to another file. ... POSIX or Portable Operating System Interface[1] is the collective name of a family of related standards specified by the IEEE to define the application programming interface (API) for software compatible with variants of the Unix operating system. ... Korn shell logo. ...

Other types of shells

The Unix shell was unusual when first created. Since it is both an interactive command language and the language used to script the system, it is a scripting programming language. Many shells created for other operating systems, offer rough equivalents to Unix shell functionality. Scripting programming languages (commonly called scripting languages or script languages) are computer programming languages designed for scripting the operation of a computer. ...

On systems using a windowing system, some users may never use the shell directly. On Unix systems, the shell is still the implementation language of system startup scripts, including the program that starts the windowing system, the program that dials into the Internet, and many other essential functions. A windowing system is a graphical user interface (GUI) which uses the window as one of its primary metaphors. ...

On MS-DOS, OS/2, and Windows, equivalents to Unix system scripts are called batch files, and have either a ".bat" or ".cmd" extension. A newer CLI, codenamed Monad and to be released as the Windows PowerShell, will replace the existing NT command line, cmd.exe; it has many features derived from Unix shells, though it uses a somewhat different syntax. Microsofts disk operating system, MS-DOS, was Microsofts implementation of DOS, which was the first popular operating system for the IBM PC, and until recently, was widely used on the PC compatible platform. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... To meet Wikipedias quality standards, the lead section of this article may need to be expanded. ... In DOS and Windows, a batch file is a text file with a series of commands (see command line interface). ... A filename extension is a suffix to the name of a computer file applied to show its format. ... Windows PowerShell, previously Microsoft Shell or MSH (codenamed Monad) is an extensible command line interface (CLI) shell and scripting language product developed by Microsoft. ... This article needs additional references or sources for verification. ...

Many users of a Unix system still find a modern command line shell much more convenient for many tasks than any GUI application. GUI can refer to the following: GUI is short for graphical user interface, a term used to describe a type of interface in computing. ... This article does not cite any references or sources. ...

Due to the recent movement in favor of open source, most Unix shells have at least one version that is open source. Open source refers to projects that are open to the public and which draw on other projects that are freely available to the general public. ...

Shell categories

Unix shells can be broadly divided into four categories: Bourne-like, C Shell-like, nontraditional, and historical. On most modern Unix-like systems the current shell is held in the $SHELL environmental variable.

Bourne shell compatible

• Bourne shell (sh) -- Written by Steve Bourne, while at Bell Labs. First distributed with Version 7 Unix, circa 1978, and enhanced over the years.
  • Almquist shell (ash) -- Written as a BSD-licensed replacement for the Bourne Shell; often used in resource-constrained environments.
  • Bourne-Again shell (bash) -- Written as part of the GNU project to provide a superset of Bourne Shell functionality.
  • Korn shell (ksh) -- Written by David Korn, while at Bell Labs.
  • Z shell (zsh) -- considered as the most complete (read: the most features) shell

The Bourne shell, or sh, was the default Unix shell of Unix Version 7, and replaced the Thompson shell, whose executable file had the same name, sh. ... Steve Bourne is a computer scientist, most famous as the author of the Bourne shell (sh), which remains the standard command line interface to Unix. ... Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) was the main research and development arm of the United States Bell System. ... Seventh Edition Unix, also called Version 7 Unix, Version 7 or just V7, was an important early release of the Unix operating system. ... Year 1978 (MCMLXXVIII) was a common year starting on Sunday (link displays the 1978 Gregorian calendar). ... The Almquist shell (ash) is Kenneth Almquists clone of the Bourne shell. ... This article is about the UNIX shell named Bash. ... GNU (pronounced ) is a computer operating system composed entirely of free software. ... Korn shell logo. ... David Korn is a computer programmer, who is probably best known for creating the Korn shell, a command line shell interface/programming language for UNIX-like systems. ... Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) was the main research and development arm of the United States Bell System. ... The Z shell (zsh) is a Unix shell that can be used as an interactive login shell and as a powerful command interpreter for shell scripting. ...

C shell compatible

• C shell (csh) Written by Bill Joy, while at the University of California, Berkeley. First distributed with BSD, circa 1979.
  • TENEX C shell (tcsh)

The C shell (csh) is a Unix shell developed by Bill Joy for the BSD Unix system. ... Bill Joy William Nelson Joy (born Nov 8, 1954), commonly known as Bill Joy, is an American computer scientist. ... Sather tower (the Campanile) looking out over the San Francisco Bay and Mount Tamalpais. ... BSD redirects here; for other uses see BSD (disambiguation). ... Also: 1979 by Smashing Pumpkins. ... tcsh is a Unix shell, based on (and compatible with) the C shell (csh). ...

Other or exotic

• fish, friendly interactive shell, first released in 2005.
• mudsh, an "intelligent" game-like shell that operates like a MUD.
• zoidberg, a modular Perl shell written, configured, and operated entirely in Perl
• rc, the default shell on Plan 9 from Bell Labs and Version 10 Unix written by Tom Duff. Ports have been made to Inferno and Unix-like operating systems.
  • es shell (es) A functional programming rc-compatible shell written in the mid-1990s.
• scsh (Scheme Shell)

A list of various shells may be found at www.freebsd.org. fish is a UNIX command shell. ... In computer gaming, a MUD (Multi-User Dungeon, Domain or Dimension) is a multi-player computer game that combines elements of role-playing games, hack and slash style computer games and social chat rooms. ... The rc shell is the command line interface for the Version 10 Unix and Plan 9 operating systems. ... Plan 9 from Bell Labs is a distributed operating system, primarily used as a research vehicle. ... Tenth Edition Unix, also known as Version 10 Unix or V10, was the last version of the Research Unix operating system developed and used internally at Bell Labs. ... Thomas Douglas Selkirk Duff (b. ... Inferno is an operating system for creating and supporting distributed services. ... 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 es shell is a command line interpreter that uses a scripting language similar to the rc shell. ... Functional programming is a programming paradigm that conceives computation as the evaluation of mathematical functions and avoids state and mutable data. ... Scsh is a POSIX API layered on top of the Scheme programming language (currently only a Scheme 48 implementation exists, but others are planned) in a manner to make the most of schemes capability for scripting. ...

Historic

• Thompson shell (sh) -- The first Unix shell, written by Ken Thompson at Bell Labs. Distributed with Versions 1 through 6 of Unix, from 1971 to 1975. Considered very rudimentary by modern standards and not used on current systems, though available as part of some Ancient UNIX Systems.
• PWB shell or Mashey shell (sh) -- A version of the Thompson shell, augmented by John Mashey and others, while at Bell Labs. Distributed with the Programmer's Workbench UNIX, circa 1976.

The Thompson shell was the first Unix shell, introduced in the first version of Unix in 1971, and was written by Ken Thompson. ... Ken Thompson Kenneth Thompson (born February 4, 1943) is a pioneer of computer science notable for his contributions to the development of the C programming language and the UNIX operating system. ... Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) was the main research and development arm of the United States Bell System. ... Year 1971 (MCMLXXI) was a common year starting on Friday (link will display full calendar) of the 1971 Gregorian calendar. ... Year 1975 (MCMLXXV) was a common year starting on Wednesday (link will display full calendar) of the Gregorian calendar. ... Ancient UNIX is a term coined by Santa Cruz Operation (now Tarantella, Inc. ... The PWB shell (also known as the Mashey shell) was an early Unix shell distributed with some versions of Programmers Workbench UNIX circa 1975-1977. ... John Mashey is an ancient UNIX person, having started work on it at Bell Labs in 1973, and continuing to work there for 10 years. ... Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) was the main research and development arm of the United States Bell System. ... Programmers Workbench UNIX was an early version of the UNIX operating system. ... Year 1976 Pick up sticks(MCMLXXVI) was a leap year starting on Thursday (link will display full calendar) of the Gregorian calendar. ...

Further reading

• Ellie Quigley (2001). "Introduction to UNIX shells", Unix Shells by Example. Prentice Hall PTR. ISBN 013066538X.  — a history of the various shells, and the uses of and responsibilities of a shell on Unix

See also

• Shell
• Comparison of computer shells
• Shell script
• List of Unix programs
• Shell account

In computing, a shell is a piece of software that provides an interface for users (command line interpreter). ... A shell is a computer program which interacts with the userland and subsequently the kernel of an operating system. ... A shell script is a script written for the shell, or command line interpreter, of an operating system. ... This is a list of Unix programs. ... A shell account is a personal account that gives a user access to a Unix shell on another machine, usually through ssh (and historically telnet. ...

External links

• Unix Shells - csh, ksh, bash, zsh, ... by Christopher Browne
• In the Beginning was the Command Line by Neal Stephenson
• The Shell Review by Francis Wong
• shell (computing) history, types, definitions and technical information