Simple decision paths using command-line lists

We have used command-line lists (|| and &&), both in Chapter 1, The What and Why of Scripting with Bash, and in some of the scripts found in Chapter 2, Creating Interactive Scripts. Lists are one of the simplest conditional statements that we can create, and so we thought that it was appropriate to use them in the earlier examples before fully explaining them here.

Command-line lists are two or more statements that are joined using either the AND or OR notations:

• &&: AND
• ||: OR

Where the two statements are joined using the AND notation, the second command only runs if the first command succeeds. Whereas, with the OR notation, the second command will run only if the first command fails.

The decision on the success or failure of a command is taken by reading the exit code from the application. A zero represents a successful application completion and anything other than a zero represents a failure. We can test the success or failure...