Introduction to Unix
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4.1. A Choice of Shells

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.

4.1.1. A Bit of Shell History

  • 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.

4.1.2. chsh

chsh

change your login shell

SYNOPSIS

chsh [ -s shell ] [ -l ] [ username ]

DESCRIPTION

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

Specify your login shell.

-l, --list-shells

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