- A Unix shell is a command-line interpreter or shell that provides a traditional user interface for the Unix operating system and for Unix-like systems. Users direct the operation of the computer by entering commands as text for a command line interpreter to execute or by creating text scripts of one or more such commands.
This article is meant to be a general introduction to command shells. Existing shells should be briefly mention here.
List of shells
- Bash — Shell, or command language interpreter, that will appear in the GNU operating system. Bash is an sh-compatible shell that incorporates useful features from the Korn shell (ksh) and C shell (csh). It is intended to conform to the IEEE POSIX P1003.2/ISO 9945.2 Shell and Tools standard. It offers functional improvements over sh for both programming and interactive use. In addition, most sh scripts can be run by Bash without modification.
- C shell — Command language interpreter usable both as an interactive login shell and a shell script command processor. It includes a command-line editor, programmable word completion, spelling correction, a history mechanism, job control and a C-like syntax.
- DASH — POSIX-compliant implementation of /bin/sh that aims to be as small as possible. It does this without sacrificing speed where possible. In fact, it is significantly faster than bash (the GNU Bourne-Again SHell) for most tasks.
- Fish — Smart and user-friendly command line shell for OS X, Linux, and the rest of the family.
- Korn shell — The KornShell language was designed and developed by David G. Korn at AT&T Bell Laboratories. It is an interactive command language that provides access to the UNIX system and to many other systems, on the many different computers and workstations on which it is implemented. The KornShell language is also a complete, powerful, high-level programming language for writing applications, often more easily and quickly than with other high-level languages. This makes it especially suitable for prototyping. There are two other widely used shells, the Bourne shell developed by Steven Bourne at AT&T Bell Laboratories, and the C shell developed by Bill Joy at the University of California. ksh has the best features of both, plus many new features of its own. Thus ksh can do much to enhance your productivity and the quality of your work, both in interacting with the system, and in programming. ksh programs are easier to write, and are more concise and readable than programs written in a lower level language such as C.
- Oh — Unix shell written in Go. It is similar in spirit but different in detail from other Unix shells. Oh extends the shell's programming language features without sacrificing the shell's interactive features.
- Zsh — Shell designed for interactive use, although it is also a powerful scripting language. Many of the useful features of bash, ksh, and tcsh were incorporated into zsh; many original features were added. The introductory document details some of the unique features of zsh.