In this chapter, we're going to look at functions, and how these can enhance your scripts. The theory of functions is not too complicated: a function is a set of commands grouped together that can be called (executed) multiple times without having to write the whole set of commands again. As always, a good example is worth a thousand words, so let's dive right in with one of our favorite examples: printing Hello world!.
We now know it's relatively easy to get the words Hello world! to appear on our terminal. A simple echo "Hello world!" does just the trick. However, if we wanted to do this multiple times, how would we go about it? You could suggest using any kind of loop, which would indeed allow us to print multiple times. However, that loop also requires some extra code and planning up front. As you will notice, in practice loops are great for iterating over items, but not exactly suitable for reusing code in a predictable manner. Let's see how we can use...