Bash-Beginners-Guide

Server: JPackage 1.5 for Fedora Core 2
Server: JPackage 1.5, generic
Server: Fedora Linux 2 - i386 - updates
Finding updated packages
Downloading needed headers
Resolving dependencies
Dependencies resolved
I will do the following:
[install: tuxracer 0.61-26.i386]
Is this ok [y/N]: EnterDownloading Packages
Running test transaction:
Test transaction complete, Success!
tuxracer 100 % done 1/1
Installed: tuxracer 0.61-26.i386
Transaction(s) Complete
8.3. Summary
In this chapter, we learned how to provide user comments and how to prompt for user input. This is usually
done using the echo/read combination. We also discussed how files can be used as input and output using file
descriptors and redirection, and how this can be combined with getting input from the user.
We stressed the importance of providing ample message for the users of our scripts. As always when others
use your scripts, it is better to give too much information than not enough. Here documents is a type of shell
construct that allows creation of lists, holding choices for the users. This construct can also be used to execute
otherwise interactive tasks in the background, without intervention.
8.4. Exercises
These exercises are practical applications of the constructs discussed in this chapter. When writing the scripts,
you may test by using a test directory that does not contain too much data. Write each step, then test that
portion of code, rather than writing everything at once.
1.
Bash Guide for Beginners
Write a script that asks for the user's age. If it is equal to or higher than 16, print a message saying that
this user is allowed to drink alcohol. If the user's age is below 16, print a message telling the user how
many years he or she has to wait before legally being allowed to drink.
As an extra, calculate how much beer an 18+ user has drunk statistically (100 liters/year) and print
this information for the user.
2. Write a script that takes one file as an argument. Use a here document that presents the user with a
couple of choices for compressing the file. Possible choices could be gzip, bzip2, compress and zip.
3. Write a script called homebackup that automates tar so the person executing the script always uses
the desired options (cvp) and backup destination directory (/var/backups) to make a backup of
his or her home directory. Implement the following features:
♦ Test for the number of arguments. The script should run without arguments. If any arguments
are present, exit after printing a usage message.
♦ Determine whether the backups directory has enough free space to hold the backup.
♦ Ask the user whether a full or an incremental backup is wanted. If the user does not have a
full backup file yet, print a message that a full backup will be taken. In case of an incremental
backup, only do this if the full backup is not older than a week.
Chapter 8. Writing interactive scripts 106