2.1. Introduction

This chapter presents the Unix commands of interest to users and programmers. Most of these commands appear in the "Commands" section of the online manual. With rare exception, this book purposely avoids system administration commands, because system administration is beyond its scope. The focus instead is on everyday commands, those used both interactively and for programming.

Summarizing three operating systems that are similar but not identical is a daunting task. In order to make a coherent presentation, the chapter is organized as follows: