This book is about programming with the shell, not about using it at the command line. The information provided here is about editing the command line, creating a command prompt (the PS1 variable), or retrieving commands from the interactive history. This chapter is about scripts that will mostly be useful at the command line rather than in other scripts.
Many of the scripts presented in this chapter are shell functions. Some of them have to be that way because they change the environment. Others are functions because ...
