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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 equivalent program is command.com.
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. 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 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, such
as bash.
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. Many regular users of a UNIX system still find a modern shell much more convenient for many tasks than any
GUI application.
Unix shells
See also
External link
- Unix
Shells - csh, ksh, bash, zsh, ... by Christopher Browne
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