Understanding variables

Bash is more than just a shell. You could argue that it is very similar to a complete programming language, and you wouldn't be wrong. Bash is a scripting engine (we will get into scripting later) and there are many debates as to what distinguishes a scripting language from a programming language, and that line becomes more and more blurred as new languages come out. As with any scripting language, Bash supports variables. The concept of variables is very simple in Bash, but I figured I'd give it its own (relatively short) section to make sure you understand the basics. You can set a variable with a command such as the following:

myvar='Hello world!'

When Bash encounters an equal sign after a string, it assumes you're creating a variable. Here, we're creating a variable named myvar and setting it equal to Hello world! Whenever we refer to a variable, though, we need to specifically clarify to Bash that we're requesting...