Operating system shell
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The shell of an operating system is a program that presents an interface to various operating system functions and services. The shell is so called because it is an outer layer of interface between the user and the innards of the operating system (The kernel).
Shells generally fall into 1 of two categories - commandline and graphical, providing a command line interface (CLI) to the operating system or a graphical user interface (GUI) respectively.
The relative merits of CLI and GUI based shells are often debated. CLI proponents claim that performing certain operations under CLI shells are much faster than that of GUI shells (such as moving files, for example), however GUI proponents claim the comparative ease-of-use and simplicity of GUI shells. The best choice is often determined by the type of use it will recieve. On a server mainly used for data transfers and processing with expert administration, a CLI is likely to be the best choice, likewise, for a computer to be mainly used for secretarial work by an office worker, a GUI whould probably be more appropriate.
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List of shells
Graphical (GUI) shells
Text (CLI shells)
- Almquist shell (ash)
- Bourne shell (sh) Written by Steve Bourne, while at Bell Labs. First distributed with Version 7 UNIX, circa 1978.
- Bourne-Again shell (bash)
- C shell (csh) Written by Bill Joy, while at the University of California, Berkeley. First distributed with BSD, circa 1979.
- PWD shell Written by John Mashey, while at Bell Labs. Distributed with the Programmer's Workbench UNIX, circa 1976.
- scsh (Scheme Shell)
- TENEX C shell (tcsh)
- Korn shell (ksh) Written by Dave Korn, while at Bell Labs.
- rc shell (rc)
- Z shell (zsh)
