UNIX Shells by Example, Third Edition

	Table of Contents
	Examples

UNIX Shells by Example, Third Edition
By Ellie Quigley
Publisher	: Prentice Hall PTR
Pub Date	: October 01, 2001
ISBN	: 0-13-066538-X
Pages	: 1040

Five UNIX shells, three essential utilities, one indispensable resource!

• Learn UNIX shell programming the easy way, using hands-on examples

• Covers all five leading UNIX shells-C, Bourne, Korn, bash, and tcsh

• By best-selling author Ellie Quigley, Silicon Valley's top UNIX instructor

The best-selling UNIX Shells by Example continues to be the only book you need to learn UNIX shell programming. UNIX Shells by Example, Third Edition adds thorough coverage of the new bash and tcsh shells to the full explanations in Quigley's famous treatment of the C, Bourne, and Korn shells and the awk, sed, and grep utilities, making this the most complete UNIX shell programming book available anywhere. Using proven techniques drawn from her acclaimed Silicon Valley UNIX classes, Quigley transforms you into an expert-level shell programmer. You'll learn what the shells are, what they do, and how to program them, as well as how and when to use awk, sed, and grep. Code examples, completely revised and classroom-tested for this edition, explain concepts first-hand and can serve as the basis for your own projects.

Explains the C, Bourne, Korn, bash, and tcsh shells in one cohesive way-you'll understand which shell to use and why Details the essential awk, sed, and grep programming utilities Offers proven teaching methods from a top UNIX shell instructor Provides source code and data files for all examples on the CD-ROM, so you can experiment with them on your own system UNIX system administrators, application developers, and power users will turn to this book again and again, both as a vital classroom learning tool and as a favorite reference manual.

777

		Copyright
		Preface
			ACKNOWLEDGMENTS
		Chapter 1.  Introduction to UNIX Shells
			Section 1.1.  Definition and Function
			Section 1.2.  System Startup and the Login Shell
			Section 1.3.  Processes and the Shell
			Section 1.4.  The Environment and Inheritance
			Section 1.5.  Executing Commands from Scripts
		Chapter 2.  The UNIX Toolbox
			Section 2.1.  Regular Expressions
			Section 2.2.  Combining Regular Expression Metacharacters
		Chapter 3.  The grep Family
			Section 3.1.  The grep Command
			Section 3.2.  grep Examples with Regular Expressions
			Section 3.3.  grep with Pipes
			Section 3.4.  grep with Options
			Section 3.5.  egrep (Extended grep)
			Section 3.6.  Fixed grep or Fast grep
			UNIX TOOLS LAB EXERCISE
		Chapter 4.  sed, the Streamlined Editor
			Section 4.1.  What Is sed?
			Section 4.2.  How Does sed Work?
			Section 4.3.  Addressing
			Section 4.4.  Commands and Options
			Section 4.5.  Error Messages and Exit Status
			Section 4.6.  sed Examples
			Section 4.7.  sed Scripting
			UNIX TOOLS LAB EXERCISE
		Chapter 5.  The awk Utility: awk as a UNIX Tool
			Section 5.1.  What Is awk?
			Section 5.2.  awk's Format
			Section 5.3.  Formatting Output
			Section 5.4.  awk Commands from Within a File
			Section 5.5.  Records and Fields
			Section 5.6.  Patterns and Actions
			Section 5.7.  Regular Expressions
			Section 5.8.  awk Commands in a Script File
			Section 5.9.  Review
			UNIX TOOLS LAB EXERCISE
		Chapter 6.  The awk Utility: awk Programming Constructs
			Section 6.1.  Comparison Expressions
			Section 6.2.  Review
			UNIX TOOLS LAB EXERCISE
		Chapter 7.  The awk Utility: awk Programming
			Section 7.1.  Variables
			Section 7.2.  Redirection and Pipes
			Section 7.3.  Pipes
			Section 7.4.  Closing Files and Pipes
			Section 7.5.  Review
			UNIX TOOLS LAB EXERCISE
			Section 7.6.  Conditional Statements
			Section 7.7.  Loops
			Section 7.8.  Program Control Statements
			Section 7.9.  Arrays
			Section 7.10.  awk Built-In Functions
			Section 7.11.  Built-In Arithmetic Functions
			Section 7.12.  User-Defined Functions (nawk)
			Section 7.13.  Review
			UNIX TOOLS LAB EXERCISE
			Section 7.14.  Odds and Ends
			Section 7.15.  Review
			UNIX TOOLS LAB EXERCISE
		Chapter 8.  The Interactive Bourne Shell
			Section 8.1.  Startup
			Section 8.2.  Programming with the Bourne Shell
			BOURNE SHELL LAB EXERCISES
		Chapter 9.  The C Shell
			Section 9.1.  The Interactive C Shell
			Section 9.2.  Programming with the C Shell
			C SHELL LAB EXERCISES
		Chapter 10.  The Korn Shell
			Section 10.1.  Interactive Korn Shell
			Section 10.2.  Programming with the Korn Shell
			KORN SHELL LAB EXERCISES
		Chapter 11.  The Interactive bash Shell
			Section 11.1.  Introduction
			Section 11.2.  Command Line Shortcuts
			Section 11.3.  Variables
			BASH SHELL LAB EXERCISES
		Chapter 12.  Programming with the bash Shell
			Section 12.1.  Introduction
			Section 12.2.  Reading User Input
			Section 12.3.  Arithmetic
			Section 12.4.  Positional Parameters and Command Line Arguments
			Section 12.5.  Conditional Constructs and Flow Control
			Section 12.6.  Looping Commands
			Section 12.7.  Functions
			Section 12.8.  Trapping Signals
			Section 12.9.  Debugging
			Section 12.10.  Processing Command Line Options with getopts
			Section 12.11.  The eval Command and Parsing the Command Line
			Section 12.12.  bash Options
			Section 12.13.  Shell Built-In Commands
			BASH SHELL LAB EXERCISES
		Chapter 13.  The Interactive TC Shell
			Section 13.1.  Introduction
			Section 13.2.  The TC Shell Environment
			Section 13.3.  Command Line Shortcuts
			Section 13.4.  Job Control
			Section 13.5.  Metacharacters
			Section 13.6.  Redirection and Pipes
			Section 13.7.  Variables
			Section 13.8.  Arrays
			Section 13.9.  Special Variables and Modifiers
			Section 13.10.  Command Substitution
			Section 13.11.  Quoting
			Section 13.12.  Built-In Commands
			TC SHELL LAB EXERCISES
		Appendix A.  Useful UNIX Utilities for Shell Programmers
			at at, batch execute commands at a later time
			awk pattern scanning and processing language
			banner make posters
			basename with a directory name delivers portions of the pathname
			bc processes precision arithmetic
			bdiff compares two big files
			cal displays a calendar
			cat concatenates and displays files
			chmod change the permissions mode of a file
			chown changes owner of file
			clear clears the terminal screen
			cmp compares two files
			compress compress, uncompress, zcat compress, uncompress files, or display expanded files
			cp copies files
			cpio copy file archives in and out
			cron the clock daemon
			crypt encodes or decodes a file
			cut removes selected fields or characters from each line of a file
			date displays the date and time or sets the date
			diff compares two files for differences diff [ bitw] [ c | Cn
			du summarizes disk usage
			echo echoes arguments
			egrep searches a file for a pattern using full regular expressions
			expr evaluates arguments as an expression
			fgrep search a file for a character string
			file determines the type of a file by looking at its contents
			find finds files
			finger displays information about local and remote users
			fmt simple text formatters
			fold folds long lines
			ftp file transfer program
			getopt(s) parses command line options
			grep searches a file for a pattern
			groups prints group membership of user
			id prints the username, user ID, group name and group ID
			jsh the standard, job control shell
			line reads one line
			logname gets the name of the user running the process
			lp sends output to a printer (AT&T)
			lpr sends output to a printer (UCB)
			lpstat print information about the status of the LP print service (AT&T)
			lpq print information about the status of the printer (UCB)
			ls lists contents of directory
			mail mail, rmail read mail or send mail to users
			mailx interactive message processing system
			make maintains, updates, and regenerates groups of related programs and files
			mesg permits or denies messages resulting from the write command
			mkdir creates a directory
			more browse or page through a text file
			mv move or rename files
			nawk pattern scanning and processing language
			newgrp log in to a new group
			news prints news items
			nice runs a command at low priority
			nohup makes commands immune to hangups and quits
			od octal dump
			pack pack, pcat, unpack compresses and expands files
			passwd changes the login password and password attributes
			paste merges same lines of several files or subsequent lines of one file
			pcat (see pack)
			pg displays files a page at a time
			pr prints files
			ps reports process status
			pwd displays the present working directory name
			rcp remote file copy
			rlogin remote login
			rm removes files from directories
			rmdir removes a directory
			rsh starts a remote shell
			ruptime shows the host status of local machines
			rwho who is logged in on local machines
			script creates a typescript of a terminal session
			sed streamlined editor
			size prints section sizes in bytes of object files
			sleep suspends execution for some number of seconds
			sort sort and/or merge files
			spell finds spelling errors
			split splits a file into pieces
			strings finds any printable strings in an object or binary file
			stty sets the options for a terminal
			su become superuser or another user
			sum calculates a checksum for a file
			sync updates the superblock and sends changed blocks to disk
			tabs set tab stops on a terminal
			tail displays the tail end of a file.
			talk allows you to talk to another user
			tar stores and retrieves files from an archive file, normally a tape device
			tee replicates the standard output
			telnet communicates with a remote host
			test evaluates an expression
			time displays a summary of time used by this shell and its children
			timex times a command; reports process data and system activity
			touch updates access time and/or modification time of a file
			tput initializes a terminal or queries the terminfo database
			tr translates characters
			true provide successful exit status
			tsort topological sort
			tty gets the name of the terminal
			umask sets file-creation mode mask for permissions
			uname prints name of current machine
			uncompress restores files to their original state after they have been compressed using the compress command
			uniq reports on duplicate lines in a file
			units converts quantities expressed in standard scales to other scales
			unpack expands files created by pack
			uucp copy files to another system, UNIX-to-UNIX system copy
			uuencode uuencode, uudecode encode a binary file into ASCII text in order to send it through e-mail, or convert it back into its original form
			wc counts lines, words, and characters
			what extracts SCCS version information from a file by printing information found after the @(#) pattern
			which locates a command and displays its pathname or alias (UCB)
			whereis locates the binary, source, and manual page files for a command (UCB)
			who displays who is logged on the system
			write writes a message to another user
			xargs constructs an argument list(s) and executes a command
			zcat uncompress a compressed file to standard output. Same as uncompress c
		Appendix B.  Comparison of the Shells
			Section B.1.  The Shells Compared
			Section B.2.  tcsh versus csh
			Section B.3.  bash versus sh
		Appendix C.  Steps for Using Quoting Correctly
			Section C.1.  Backslash
			Section C.2.  Single Quotes
			Section C.3.  Double Quotes
			Section C.4.  Combining Quotes
			Section C.5.  Setting the Shell Variable

Copyright

Library of Congress Cataloging-in-Publication Data

Quigley, Ellie.

UNIX shells by example / Ellie Quigley. -- 3rd ed.

p. cm.

ISBN 0-13-066538-X

1. UNIX (Computer file) 2. UNIX Shells. I. Title.

QA76.76.O63 Q54 2001

005.4'32--dc21

2001050075

2002 by Prentice Hall P T R

Prentice-Hall, Inc.

Upper Saddle River, NJ 07458

Prentice Hall books are widely used by corporations and government agencies for training, marketing, and resale.

The publisher offers discounts on this book when ordered in bulk quantities. For more information, contact: Corporate Sales Department, Phone: [phone]; Fax: [phone]; E-mail: [e-mail]; or write: Prentice Hall PTR, Corp. Sales Dept., One Lake Street, Upper Saddle River, NJ 07458.

All products or services mentioned in this book are the trademarks or service marks of their respective companies or organizations.

All rights reserved. No part of this book may be reproduced, in any form or by any means, without permission in writing from the publisher.

Printed in the United States of America

10 9 8 7 6 5 4 3 2 1

Credits

Production editor/compositor:

Vanessa Moore

Acquisitions editor:

Mark Taub

Marketing manager:

Bryan Gambrel

Manufacturing manager:

Maura Zaldivar

Editorial assistant:

Sarah Hand

Cover design director:

Jerry Votta

Cover designer:

Anthony Gemmellaro

Project coordinator:

Anne R. Garcia

Pearson Education Ltd.

Pearson Education Australia PTY, Limited

Pearson Education Singapore, Pte. Ltd

Pearson Education North Asia Ltd.

Pearson Education Canada, Ltd.

Pearson Educaci n de Mexico, S.A. de C.V.

Pearson Education Japan

Pearson Education Malaysia, Pte. Ltd.

Pearson Education, Upper Saddle River, New Jersey

Dedication

This book is dedicated to my papa, Archibald MacNichol Main, Jr., the best father in the world.

Preface

Playing the "shell" game is a lot of fun. This book was written to make your learning experience both fun and profitable. Since the first edition was published, I have heard from many of you who have been helped by my book to realize that shell programming doesn't need to be difficult at all! Learning by example makes it easy and fun. In fact, due to such positive feedback, I have been asked by Prentice Hall to produce this new, updated version to include two additional and popular shells, the Bash and TC shells. Although often associated with Linux systems, the Bash and TC shells are freely available to anyone using UNIX as well. In fact, today many UNIX users prefer these shells to the traditional UNIX shells because they offer an enhanced and flexible interactive environment, as well as improved programming capabilities.

Writing UNIX Shells by Example is the culmination of 19 years of teaching and developing classes for the various shells and those UNIX utilities most heavily used by shell programmers. The course notes I developed for teaching classes have been used by the University of California Santa Cruz and University of California Davis UNIX programs, Sun Microsystems Education, Apple Computer, DeAnza College, and numerous vendors throughout the world. Depending on the requirements of my client, I normally teach one shell at a time rather than all of them. To accommodate the needs of so many clients, I developed separate materials for each of the respective UNIX shells and tools.

Whether I am teaching "Grep, Sed, and Awk," "Bourne Shell for the System Administrator," or "The Interactive Korn Shell," one student always asks, "What book can I get that covers all the shells and the important utilities such as grep, sed, and awk? Should I get the awk book, or should I get a book on grep and sed? Is there one book that really covers it all? I don't want to buy three or four books in order to become a shell programmer."

In response, I can recommend a number of excellent books covering these topics separately, and some UNIX books that attempt to do it all, but the students want one book with everything and not just a quick survey. They want the UNIX tools, regular expressions, all three shells, quoting rules, a comparison of the shells, exercises, and so forth, all in one book. This is that book. As I wrote it, I thought about how I teach the classes and organized the chapters in the same format. In the shell programming classes, the first topic is always an introduction to what the shell is and how it works. Then we talk about the UNIX utilities such as grep, sed, and awk, the most important tools in the shell programmer's toolbox. When learning about the shell, it is presented first as an interactive program where everything can be accomplished at the command line, and then as a programming language where the programming constructs are described and demonstrated in shell scripts. (Since the C and TC shells are almost identical as programming languages, there are separate chapters describing interactive use, but only one chapter discussing programming constructs.) When shell programming classes are over, whether they last two days or a week or even a semester, the students are proficient and excited about writing scripts. They have learned how to play the shell game. This book will teach how to play the same game whether you take a class or just play by yourself.

Having always found that simple examples are easier for quick comprehension, each concept is captured in a small example followed by the output and an explanation of each line of the program. This method has proven to be very popular with those who learned Perl programming from my first book, Perl by Example, and UNIX Shells by Example now has been well-received for those who needed to write, read, and maintain shell programs.

The five shells are presented in parallel so that if, for example, you want to know how redirection is performed in one shell, there is a parallel discussion of that topic in each of the other shell chapters. For a quick comparison chart, see Appendix B of this book.

It is a nuisance to have to go to another book or the UNIX man pages when all you want is enough information about a particular command to jog your memory on how the command works. To save you time, Appendix A contains a list of useful commands, their syntax and definitions. Examples and explanations are provided for the more robust and often-used commands.

The comparison chart in Appendix B will help you keep the different shells straight, especially when you port scripts from one shell to another, and serve as a quick syntax check when all you need is a reminder of how the construct works.

One of the biggest hurdles for shell programmers is using quotes properly. The section on quoting rules in Appendix C presents a step-by-step process for successful quoting in some of the most complex command lines. This procedure has dramatically reduced the amount of time programmers waste when debugging scripts with futile attempts at matching quotes properly.

I think you'll find this book a valuable tutorial and reference. The objective is to explain through example and keep things simple so that you have fun learning and save time. Since the book replicates what I say in my classes, I am confident that you will be a productive shell programmer in a short amount of time. Everything you need is right here at your fingertips. Playing the shell game is fun. You'll see!

Ellie Quigley ([e-mail])

ACKNOWLEDGMENTS

I would like to thank and acknowledge the following people, without whose help this book would not have been published:

Mark Taub, my acquisitions editor, and Vanessa Moore, my production editor at Prentice Hall; Beth Gerra, Roberta Harvey, and Gary Wilson for reviewing the original material; Steve Hansen for hardware and software support. Finally, I would like to thank all my students at UC Santa Cruz, UC Davis, and Sun Microsystems for their feedback.