Learn Linux Shell Scripting - Fundamentals of Bash 4.4

Default values

On to parameter expansion! As we've hinted, Bash allows us to do many cool things directly with variables. We'll start with the seemingly simple example of defining a default value for your variables.

When dealing with user input, this makes both your life and the script user's life much easier: as long as there is a reasonable default value, we can make sure that we use that instead of throwing an error when the user does not supply the information we want.

We will reuse one of our earliest scripts, interactive.sh, from Chapter 8, Variables and User Input. It was a very simple script that did not verify user input, and was thus prone to all sorts of problems. Let's get it up-to-date and include our new default values for our ...