Bash-Beginners-Guide

Bash Guide for Beginners
3.7. Summary
The Bash environment can be configured globally and on a per user basis. Various configuration files are used
to fine-tune the behavior of the shell.
These files contain shell options, settings for variables, function definitions and various other building blocks
for creating ourselves a cosy environment.
Except for the reserved Bourne shell, Bash and special parameters, variable names can be chosen more or less
freely.
Because a lot of characters have double or even triple meanings, depending on the environment, Bash uses a
system of quoting to take away special meaning from one or multiple characters when special treatment is not
wanted.
Bash uses various methods of expanding command line entries in order to determine which commands to
execute.
3.8. Exercises
For this exercise, you will need to read the useradd man pages, because we are going to use the /etc/skel
directory to hold default shell configuration files, which are copied to the home directory of each newly added
user.
First we will do some general exercises on setting and displaying variables.
1. Create 3 variables, VAR1, VAR2 and VAR3; initialize them to hold the values "thirteen", "13" and
"Happy Birthday" respectively.
2. Display the values of all three variables.
3. Are these local or global variables?
4. Remove VAR3.
5. Can you see the two remaining variables in a new terminal window?
6. Edit /etc/profile so that all users are greeted upon login (test this).
7. For the root account, set the prompt to something like "Danger!! root is doing stuff in \w", preferably
in a bright color such as red or pink or in reverse video mode.
8. Make sure that newly created users also get a nice personalized prompt which informs them on which
system in which directory they are working. Test your changes by adding a new user and logging in
as that user.
9. Write a script in which you assign two integer values to two variables. The script should calculate the
surface of a rectangle which has these proportions. It should be aired with comments and generate
elegant output.
Don't forget to chmod your scripts!
Chapter 3. The Bash environment 55