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UNIX shell
*** Shopping-Tip: UNIX shell
A '''Unix shell''', also called "the
command line", provides the traditional
user interface for the
Unix operating system. 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.
The most generic sense of the term ''shell'' means ''any'' program that users use to type commands; it is called a "shell" because it hides the details of the underlying
operating system behind the shell's interface (contrast "
kernel (computer science) 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 sometimes 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.
The term ''shell'' also refers to a particular program, namely 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 the equivalent of the Bourne shell. The Bourne shell program is located in the UNIX file hierarchy at
/bin/sh. On some systems, such as
Berkeley Software Distribution BSD,
/bin/sh is a Bourne shell or equivalent, but on other systems such as
Linux,
/bin/sh is likely to be a
Symbolic_link link to a compatible, but more feature-rich shell, such as
Bash.
POSIX specifies the standard shell as a strict subset of the
Korn shell.
The Unix shell is unusual since it is in both an interactive command language and the language used to script the system; it is a
scripting programming language.
On systems using a
windowing system, some users may never use the shell directly, though 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.
On Windows, equivalents to Unix system scripts are called
batch files, and have either a ".bat" or ".cmd"
filename_extension extension.
Many regular users of a UNIX system still find a modern command line shell much more convenient for many tasks than any
GUI application software application.
Unix shells
Bourne shell compatible
*
Bourne shell (sh) Written by
Stephen Bourne Steve Bourne, while at
Bell Labs. First distributed with
Version 7 Unix, circa
1978.
**
Almquist shell (ash)
**
Bourne-Again shell (bash)
**
Korn shell (ksh) Written by
David Korn, while at
Bell Labs.
**
Z shell (zsh)
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)
Other
*
Friendly_interactive_shell fish, first released in 2005.
*
rc shell the default shell on
Plan 9 from Bell Labs and
Version 10 Unix written by
Tom Duff. Ports have been made to
Inferno (operating system) Inferno and
Unix-like operating systems.
**
es shell (es) A
functional programming rc-compatible shell written in the mid-1990s.
*
scsh (Scheme Shell)
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.
*
PWB 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.
See also
*
Shell script
*
List of Unix programs
*
Shell account
External links
-
'' Unix Shells - csh, ksh, bash, zsh, ... '' by Christopher Browne
-
''In the Beginning was the Command Line'' by Neal Stephenson
Category:Unix software
Category:System administration
Category:Unix shells
de:Unix-Shell
fr:Interpréteur de commandes
hu:Unix rendszerhéj
ja:シェル
no:Unix-skall
nn:Unix-skal
pl:Sh
ru:КоманднаÑ? оболочка UNIX
sq:Sh
zh:Unix shell
see
Unix_shell
*** Shopping-Tip: UNIX shell
