So far, we have looked at how we can check for errors. However, besides checking for errors, there is an aspect to this which is just as important: handling errors. We'll initially combine our previous experience with if and test to exit on errors, before we go on to introduce much smarter ways to handle errors!
As you might recall from the previous chapter, the if-then construct used by Bash is common to (almost) all programming languages. In its basic form, the idea is that you test for a condition (IF), and if that condition is true, you do something (THEN).
Here's a very basic example: if name is longer than or equal to 2 characters, then echo "hello ${name}". In this case, we assume that a name has to be, at the very least, 2 characters. If it is not, the input is invalid and we do not give it a "hello".
In the following script, if-then-exit.sh, we will see that our goal is to print the contents of a file using cat. However, before we do that, we check if the...