Classic Shell Scripting

Chapter 1. Background

This chapter provides a brief history of the development of the Unix system. Understanding where and how Unix developed and the intent behind its design will help you use the tools better. The chapter also introduces the guiding principles of the Software Tools philosophy, which are then demonstrated throughout the rest of the book.

Unix History

It is likely that you know something about the development of Unix, and many resources are available that provide the full story. Our intent here is to show how the environment that gave birth to Unix influenced the design of the various tools.

Unix was originally developed in the Computing Sciences Research Center at Bell Telephone Laboratories.^[1] The first version was developed in 1970, shortly after Bell Labs withdrew from the Multics project. Many of the ideas that Unix popularized were initially pioneered within the Multics operating system; most notably the concepts of devices as files, and of having a command interpreter (or shell ) that was intentionally not integrated into the operating system. A well-written history may be found at http://www.bell-labs.com/history/unix.

Because Unix was developed within a research-oriented environment, there was no commercial pressure to produce or ship a finished product. This had several advantages:

• The system was developed by its users. They used it to solve real day-to-day computing problems.

• The researchers were free to experiment and to change programs as needed. Because ...