Intel XENIX 286 Programmers Guide (86) - Tenox.tc

CHAPTER 8
csh : C SHEll
The C shell program, csh, is a command language interpreter for XENIX system users.
The C shell, like the standard XENIX shell sh, is an interface between you and XENIX
commands and programs. It translates command lines typed at a terminal into
corresponding system actions, gives you access to information such as your login name,
home directory, and mailbox, and supports the construction of shell procedures for
automating system tasks.
This chapter explains how to use the C shell. It also explains the syntax and function of
C shell commands and features and shows how to use these features to create shell
procedures. The C shell is fully described in the entry csh in Appendix B, "Programming
Commands."
Invoking the C Shell
You can invoke the C shell from another shell by typing the csh command
csh
at the standard shell's command line. You can also direct the system to invoke the C
shell for you when you log in. If you have given the C shell as your login shell in your
/etc/passwd file entry, the system automatically starts the C shell when you log in.
After the system starts the C shell, the shell searches your home directory for the
command files .cshrc and .login. If the shell finds the files, it executes the commands
contained in them and then displays the C shell prompt, normally a percent sign (%}.
The .cshrc file typically contains commands to be executed each time you start a C
shell, and the .login file contains the commands to be executed each time you log into
the system. The following is an example of a typical .login file:
set ignoreeof
set mail = (lusr/spool/mail/bill)
set time = 15
set history = 10
mail
This file contains several set commands. The set command is executed directly by the
C shell; there is no corresponding XENIX program for this command. In the example,
set is used to set the C-shell variable ignoreeof, which shields the C shell from logging
out if CONTROL-D is pressed. Instead of CONTROL-D, the logout command is used to
log out of the system. Setting the mail variable in the example causes the C shell to
notify you if you receive any mail in the specified mailbox.
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