Copyright Sams Teach Yourself Shell Programming in 24 Hours

Although the C shell did not catch on for scripts, it has become extremely popular for interactive use. Some
of the key improvements responsible for this popularity follow:
● Command History. You can recall commands you previously executed for re- execution. You can
also edit the command before it is re-executed.
● Aliases. You can create short mnemonic names for commands. Aliases are a simplified form of the
Bourne shell functions.
● File Name Completion. You can have the C shell automatically complete a filename by just typing a
few characters of the file's name.
● Job Controls. The C shell enables you to execute multiple processes and control them using the
jobs command.
The C shell is usually installed on most systems as /bin/csh.
The TENEX/TOPS C shell, tcsh, is a newer version of the C shell that enables you to scroll through the
command history using the up and down arrow keys. It also enables you to edit commands using right and
left arrow keys.
Although it is widely available in educational UNIX machines, tcsh is not always present on corporate UNIX
machines. For more information on obtaining tcsh, take a look at the following URL:
http://www.primate.wisc.edu/software/csh-tcsh-book/
This page includes information on obtaining and installing tcsh in both source and binary form.
The Korn Shell
For a long time, the only two shells to choose from were the Bourne shell and the C shell. This meant that
most users had to know two shells, the Bourne shell for programming and the C shell for interactive use.
To rectify this situation, David Korn of AT&T Bell Labs wrote the Korn shell, ksh, which incorporates all the
C shell's interactive features into the Bourne shell's syntax. For this reason, the Korn shell has become a
favorite with users.
In recent years, most vendors have started to ship the Korn shell with their versions of UNIX. Usually you will
find it installed as /bin/ksh or /usr/bin/ksh.
In general, ksh can be treated as fully compatible with sh, but some differences will prevent scripts from
functioning correctly. These exceptions are noted throughout the book.
Some of the additional features that the Korn shell brings to the Bourne shell include the following:
● Command history and history substitution
● Command aliases and functions
● File name completion
● Arrays (see Chapter 7)
● Built-in integer arithmetic (see Chapter 8)