1. CSCI 330 - The UNIX System Shell Startup and Variables
NIU - Department of Computer Science

2. UNIX Command Interpreters
CSCI The UNIX System

3. Login sequence establish connection run terminal emulation
The C Shell
Login sequence
establish connection
run terminal emulation
check userid and password
setup environment
start command interpreter: shell
startup settings
useful and helpful defaults
exit settings
CSCI The UNIX System
Copyright Department of Computer Science, Northern Illinois University, 2005

4. Shell startup settings
The C Shell
Shell startup settings
terminal settings
set path to find executables
define custom prompt
define command aliases
customize common behavior:
file name completion
file overwrite behavior
CSCI The UNIX System
Copyright Department of Computer Science, Northern Illinois University, 2005

5. Variables variable is a location in memory where values can be stored
The C Shell
Variables
variable is a location in memory where values can be stored
2 types of variables
environment
valid for complete login session
upper case by convention
shell
valid for each shell invocation
lower case
to display value
% echo $variable
CSCI The UNIX System
Copyright Department of Computer Science, Northern Illinois University, 2005

6. Predefined Environment Variables
The C Shell
Predefined Environment Variables
“printenv” displays all environment variables
Name
Meaning
HOME
The full pathname of your home directory
PATH
A List of directories to search for commands
MAIL
The full pathname of your mailbox
USER
Your user id
SHELL
The full pathname of your login shell
TERM
The type of your terminal
PWD
Current work directory
EDITOR
Default editor
DISPLAY
GUI location
CSCI The UNIX System
Copyright Department of Computer Science, Northern Illinois University, 2005