In this chapter, we're going to talk about what happens when you start the shell. This may not sound very complicated, but you'll need to know how the shell starts in order to understand how you can change the shell's settings. We'll explain how you can configure the shell so that it starts up with the settings you want to use. We'll also show you how to influence the shell when you invoke it by name.
A large portion of this chapter deals with the shell's startup files, which is where you put commands to configure the shell. We'll show some of the things you put in there, and we'll introduce shell options, which are an important way of controlling the shell. Setting options is an essential use of startup files.