One of the distinguishing things about the Unix philosophy is that the system's designers did not attempt to predict every need that users might have; instead, they tried to make it easy for each individual user to tailor the environment to their own particular needs. This is mainly done through configuration files;. These are also known as ``init files'';, ``rc files''; (for ``run control''), or even ``dot files'', because the filenames often begin with ``.''. If you'll recall, filenames that start with ``.'' aren't normally displayed by ls.
The most important configuration files are the ones used by the shell. Linux's default shell is bash;, and that's the shell this chapter covers. Before we go into how to customize bash, we should know what files bash looks at.