100 Shell Programs in Unix

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We are grateful to many people for constructive comments and criticisms, and for their help in improving our code. The work of an author is only as good as the support from their family members and friends. Sarika Jain would like to specially thank her husband, Anuj Jain for letting her off all her household chores while working in the tree house on this project. Likewise, Shivani Jain wants to thank her all family members for their understanding and encouragement throughout this project. We cound not have done this without all of you.

—AUTHORS

PART I

INTRODUCTION

I. AN OVERVIEW

UNIX is an operating system which was first developed in the 1960s, and has been under constant development ever since. By operating system, we mean the suite of programs, which make the computer work. It is a stable, multi-user, multi-tasking system for servers, desktops and laptops. UNIX systems also have a graphical user interface (GUI) similar to Microsoft Windows, which provides an easy to use environment. UNIX (and Linux, which is Linus Torvald’s version of UNIX) has deep roots in the computer industry. UNIX is a very powerful multitasking and multi-user system. Multitasking means a user can run multiple programs simultaneously with in one single login of the system. Multi-user means that many users can simultaneously and securely use the same machine with their separate dumb terminals. The following figure shows a typical UNIX setup:

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