.. include:: ../header.txt

.. _shell_choice:

A Choice of Shells
===========================

.. describe:: shell

    The **shell** is the interface between the command prompt user and the
    operating system.  It interprets the user's commands and invokes the
    appropriate systems calls so that the commands are executed.

A Bit of Shell History
-------------------------

.. index:: shell history, ksh, bash, csh, tcsh, sh

* The first shell was the Bourne shell (`sh`) by Steven Bourne of AT&T Bell
  Labs.

* The C shell (csh) was developed for BSD Unix, to offer better programming,
  but much of the syntax was changed.  It has a few ancestor shells, which
  add additional features (tcsh).

* The Korn shell (ksh), by David Korn (AT&T Bell Labs) offered better
  programming like C shell, but followed the Bourne shell syntax.
  It is often called the K shell.

* The BASH shell (bash) is quite similar to the Korn shell, but was released
  by the GNU project with an open source license.

.. _chsh:

:command:`chsh`
---------------

.. index:: chsh
.. program:: chsh
.. describe:: chsh

    change your login shell

SYNOPSIS

    :command:`chsh` [ -s shell ] [ -l ] [ username ]

DESCRIPTION 

    :command:`chsh`  is  used to change your login shell.  If a shell is not
    given on the command line, :command:`chsh` prompts for one. The new
    shell must be one of the shells listed in the :file:`/etc/shells` file.


OPTIONS
    .. option:: -s, --shell

       Specify your login shell.

    .. option:: -l, --list-shells

       Print the list of shells listed in /etc/shells and exit.