Xcode provides everything developers need to create great applications for Mac, iPhone, and iPad. Xcode 4 has been streamlined to help you write better apps. It has unified user interface design, coding, testing, and debugging all within a single window. The Xcode IDE analyzes the details of your project to identify mistakes in both syntax and logic, it can even help fix your code for you.
Xcode runs on OS X Lion and includes the Xcode IDE, Instruments, iOS Simulator, the latest Mac OS X and iOS SDKs, and hundreds of powerful features:

Book Description

Introduction to the Command Line is a visual guide that teaches the most important Unix and Linux shell commands in a simple and straight forward manner. Command line programs covered in this book are demonstrated with typical usage to aid in the learning process and help you master the command line quickly and easily. Covers popular Unix, Linux, and BSD systems.