Chapter 3. Conditions Attached

I suppose we can say that we are now into the fine print of the script. These are the details that are written into our scripts using conditions to test if a statement should run or not. We are now ready to add some intelligence in scripts so our scripts become more robust, easier to use, and more reliable. Conditional statements can be written with simple command-line lists of AND or OR commands together or, more often, within traditional if statements.

In this chapter we will cover the following topics:

• Simple decision paths using command-line lists

• Verifying user input with lists

• Using the test shell built-in

• Creating conditional statements using if

• Extending if with else

• More conditions with elif

• Creating the backup.sh script using elif

• Using case statements

• Script – front-end with grep