14.1 Review of the Shell 
14.1.1 Shell overview
A shell is an interface between the user and the kernel. It acts as an interpreter or translator. In other words, the shell accepts commands issued by you, interprets these commands, and executes the appropriate programs. Shells can be command-line driven or Graphical. Shells are interchangeable making it possible to initiate or switch between them at any time in order to use certain features not available in other shells. This chapter will focus on the Korn (ksh) and C shells (csh), the two most widely used shells for end users. You can use the ps (process status) command to see which shell you are using.

Bourne shell ($) - The Bourne shell was the original shell program for the UNIX environment. It is the default shell for the Solaris computing environment. Stephen Bourne developed the Bourne shell for the AT&T System V.2 UNIX environment. This shell does not have aliasing, history or command line editing capabilities and is used primarily by system administrators. The Bourne shell prompt is a dollar sign ($), which is similar to a DOS C:> prompt.

Korn shell ($) - The Korn shell is a superset of the Bourne shell and was developed by Stephen Korn at Bell Labs. It has many of the Bourne shell features plus added features such as aliasing, history, and command line editing. This is the most widely used shell and is the industry standard for system users. The Korn shell prompt is also a dollar sign ($).

Note - Examples given in this course are based primarily on the Korn shell.

C shell (%) - A shell based on the C programming language. Like the Korn shell, it has additional features such as aliasing and history. The C shell was developed by Bill Joy of Sun Microsystems and is still widely used today. The C shell prompt is a percent sign (%).