LPI Linux Certification in a Nutshell, 2nd Edition

Objective 1: Automating Tasks Using Scripts

Scripting is one of the oldest and most powerful tools in the Unix environment. Understanding scripts is also one of the most useful administrator skills when it comes to analyzing system problems, because setting down a procedure in a script, and testing it, forces the administrator to decide exactly what should be done.

The most common scripting languages in Linux are Perl and the Unix shells sh and bash . Perl is a complete scripting environment in itself. On most Linux installations, sh and bash are the same interpreter, but this is not the case on Unix in general. sh and bash adhere to the old toolbox philosophy of Unix: lots of little programs that do one task well. Among the subordinate tools they invoke are sed and awk.

Thus, using sed and awk is considered an integral part of shell scripting. One thing to note about Bash and shell scripting in general is that in an unfriendly environment it is quite easy for an intruder to subvert the scripts and turn them to their own uses.

To take this exam, you should already know scripting on the level described in the Objective so that you understand all the examples shown here. This book will not teach you to program. Scripting is complex enough that there are whole books devoted to the subject. We will only scratch the surface. The scripts shown in this chapter illustrate system administration tasks more than they help you learn programming.

Shell scripting is best suited for checking things ...