ptg18186768 ptg18186768 An iconic symbol of the American West, Monument Valley is one of the natural wonders of the world. The red-sand desert region is located within the range of the Navajo Nation on the Arizona-Utah border and is host to towering sandstone rock formations that have been sculpted over time and soar 400 to 1,000 feet above the valley floor. Three of the valley’s most photographed peaks are the distinctive East and West Mitten Buttes and Merrick Butte. Shell Programming in Unix, Linux and OS X ptg18186768 Fourth Edition Developer’s Library ESSENTIAL REFERENCES FOR PROGRAMMING PROFESSIONALS Developer’s Library books are designed to provide practicing programmers with unique, high-quality references and tutorials on the programming languages and technologies they use in their daily work. All books in the Developer’s Library are written by expert technology practitioners who are especially skilled at organizing and presenting information in a way that’s useful for other programmers. Key titles include some of the best, most widely acclaimed books within their topic areas: PHP & MySQL Web Development Python Essential Reference Luke Welling & Laura Thomson David Beazley ISBN-13: 978-0-321-83389-1 ISBN-13: 978-0-672-32862-6 MySQL Programming in Objective-C ptg18186768 Paul DuBois Stephen G. Kochan ISBN-13: 978-0-672-32938-8 ISBN-13: 978-0-321-56615-7 Linux Kernel Development Programming in C Robert Love Stephen G. Kochan ISBN-13: 978-0-672-32946-3 ISBN-13: 978-0-321-77641-9 Developer’s Library books are available at most retail and online bookstores, as well as by subscription from Safari Books Online at safari.informit.com Developer’s Library informit.com/devlibrary Shell Programming in Unix, Linux and OS X ptg18186768 Fourth Edition Stephen G. Kochan Patrick Wood 800 East 96th Street, Indianapolis, Indiana 46240 Shell Programming in Unix, Linux and OS X, Fourth Edition Editor Copyright © 2017 by Pearson Education, Inc. Mark Taber Copy Editor All rights reserved. No part of this book shall be reproduced, stored in a retrieval system, or transmitted by any means, electronic, mechanical, photocopying, recording, or otherwise, Larry Sulky without written permission from the publisher. No patent liability is assumed with respect to Technical Editor the use of the information contained herein. Although every precaution has been taken in Brian Tiemann the preparation of this book, the publisher and author assume no responsibility for errors or Designer omissions. Nor is any liability assumed for damages resulting from the use of the informa- Chuti Prasertsith tion contained herein. Page Layout ISBN-13: 978-0-13-4449600-9 codeMantra ISBN-10: 0-13-449600-0 Printed in the United States of America First Printing: August 2016 The Library of Congress Control Number is on file. Trademarks All terms mentioned in this book that are known to be trademarks or service marks have been appropriately capitalized. The publisher cannot attest to the accuracy of this information. Use of a term in this book should not be regarded as affecting the validity of any trademark or service mark. Warning and Disclaimer Every effort has been made to make this book as complete and as accurate as possible, but no warranty or fitness is implied. The information provided is on an “as is” basis. The author and the publisher shall have neither liability nor responsibility to any person or entity with respect to any loss or damages arising from the information contained in this book. ptg18186768 Special Sales For information about buying this title in bulk quantities, or for special sales opportunities (which may include electronic versions; custom cover designs; and content particular to your business, training goals, marketing focus, or branding interests), please contact our corporate sales department at [email protected] or (800) 382-3419. For government sales inquiries, please contact [email protected] For questions about sales outside the U.S., please contact [email protected] Contents at a Glance Introduction 1 1 A Quick Review of the Basics 5 2 What Is the Shell? 39 3 Tools of the Trade 51 4 And Away We Go 93 5 Can I Quote You on That? 105 6 Passing Arguments 121 7 Decisions, Decisions 131 8 'Round and 'Round She Goes 163 9 Reading and Printing Data 185 10 Your Environment 209 ptg18186768 11 More on Parameters 239 12 Loose Ends 255 13 Rolo Revisited 273 14 Interactive and Nonstandard Shell Features 289 A Shell Summary 321 B For More Information 359 Index 363 Table of Contents Introduction 1 How This Book Is Organized 2 Accessing the Free Web Edition 3 1 A Quick Review of the Basics 5 Some Basic Commands 5 Displaying the Date and Time: The date Command 5 Finding Out Who’s Logged In: The who Command 5 Echoing Characters: The echo Command 6 Working with Files 6 Listing Files: The ls Command 7 Displaying the Contents of a File: The cat Command 7 Counting the Number of Words in a File: The wc Command 7 Command Options 8 Making a Copy of a File: The cp Command 8 Renaming a File: The mv Command 8 ptg18186768 Removing a File: The rm Command 9 Working with Directories 9 The Home Directory and Pathnames 10 Displaying Your Working Directory: The pwd Command 12 Changing Directories: The cd Command 12 More on the ls Command 15 Creating a Directory: The mkdir Command 17 Copying a File from One Directory to Another 18 Moving Files Between Directories 19 Linking Files: The ln Command 20 Removing a Directory: The rmdir Command 23 Filename Substitution 24 The Asterisk 24 Matching Single Characters 25 Filename Nuances 27 Spaces in Filenames 27 Other Weird Characters 28 Standard Input/Output, and I/O Redirection 28 Standard Input and Standard Output 28 Contents vii Output Redirection 30 Input Redirection 32 Pipes 33 Filters 35 Standard Error 35 More on Commands 36 Typing More Than One Command on a Line 36 Sending a Command to the Background 36 The ps Command 37 Command Summary 37 2 What Is the Shell? 39 The Kernel and the Utilities 39 The Login Shell 40 Typing Commands to the Shell 43 The Shell’s Responsibilities 44 Program Execution 45 Variable and Filename Substitution 47 ptg18186768 I/O Redirection 48 Hooking up a Pipeline 49 Environment Control 49 Interpreted Programming Language 50 3 Tools of the Trade 51 Regular Expressions 51 Matching Any Character: The Period (.) 51 Matching the Beginning of the Line: The Caret (^) 53 Matching the End of the Line: The Dollar Sign $ 53 Matching a Character Set: The [...] Construct 55 Matching Zero or More Characters: The Asterisk (*) 57 Matching a Precise Number of Subpatterns: \{...\} 59 Saving Matched Characters: \(...\) 61 cut 64 The -d and -f Options 66 paste 68 The -d Option 69 The -s Option 70 viii Contents sed 70 The -n Option 72 Deleting Lines 73 tr 74 The -s Option 76 The -d Option 77 grep 78 Regular Expressions and grep 81 The -v Option 82 The -l Option 82 The -n Option 83 sort 84 The -u Option 84 The -r Option 85 The -o Option 85 The -n Option 86 Skipping Fields 87 The -t Option 87 ptg18186768 Other Options 88 uniq 88 The -d Option 89 Other Options 90 4 And Away We Go 93 Command Files 93 Comments 96 Variables 97 Displaying the Values of Variables 98 Undefined Variables Have the Null Value 100 Filename Substitution and Variables 101 The ${variable} Construct 102 Built-in Integer Arithmetic 103 5 Can I Quote You on That? 105 The Single Quote 105 The Double Quote 109 The Backslash 111