Wicked Cool Shell Scripts

402 Pages·2·12.036 MB·English

by  Dave Taylor, Brandon Perry

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Shell scripts are an efficient way to interact with your • Tools for renaming and applying commands to files
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machine and manage your files and system opera- in bulk AA NN DD UU NN II XX SS YY SS TT EE MM SS
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tions. With just a few lines of code, your computer
• Image processing and editing tools
will do exactly what you want it to do. But you can EE
also use shell scripts for many other essential (and Whether you want to save time managing your system DD
not-so-essential) tasks. or just find new ways to goof off, these scripts are D A V E T A Y L O R A N D B R A N D O N P E R R Y

wicked cool! CC
This second edition of Wicked Cool Shell Scripts offers
a collection of useful, customizable, and fun shell scripts ABOUT THE AUTHORS OO
for solving common problems and personalizing your OO
Dave Taylor is the author of more than 20 books,
computing environment. Each chapter contains ready-
as well as thousands of magazine and newspaper LL
to-use scripts and explanations of how they work, why
articles, and is an award-winning public speaker. He
you’d want to use them, and suggestions for changing SS
was a contributor to BSD 4.4 UNIX, and his software
and expanding them. You’ll find a mix of classic favor- is included in all major UNIX distributions. HH
ites, like a disk backup utility that keeps your files safe
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when your system crashes, a password manager, a Brandon Perry started writing C# applications with
weather tracker, and several games, as well as the advent of the open source .NET implementation LL
23 brand-new scripts, including: Mono. In his free time, he enjoys writing modules for LL
the Metasploit framework, parsing binary files, and
• A ZIP code lookup tool that reports the city and state SS
fuzzing things.
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• A Bitcoin address information retriever
COVERS THE BOURNE-AGAIN SHELL (BASH) RR
• A suite of tools for working with cloud services like
FOR LINUX, UNIX, AND OS X II
Dropbox and iCloud
PP
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THE FINEST IN GEEK ENTERTAINMENT™ P T
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www.nostarch.com ERANY
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$34.95 ($40.95 CDN) RYDOR
“I LIE FLAT.”
This book uses a durable binding that won’t snap shut. PROGRAMMSHELVE IN:
IN
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EN
FSC FPO ERAL

Praise for the first edition of Wicked cool Shell ScriptS
“A must for any new or intermediate-level Linux administrator. This is the
book that every other publisher tries to imitate.”
—linuxworld
“I can’t give this book enough praise and high enough recommendation.
Quite simply, this is the book that I wish I would’ve had when I was just learn-
ing Linux.”
—steve suehring, linuxworld editor
“A great resource for intermediate to experienced shell programmers.”
—webdevreviews
“If you’re interested in the command line and shell scripting, this is an
excellent book which will extend your knowledge and provide more than a
hundred ready-to-run scripts.”
—macblog.com
“There are a few books in the [computer] field that remain useful for years
and years after their publishing date. Wicked Cool Shell Scripts is one of those
fortunate few.”
—the brainshed
“Incredibly fun (really!) and chock full of scripts.”
—slashdot

W i c k e d co o l
S h e l l S c r i p tS
2 n d ed i t i o n
101 Scripts for linux,
oS X, and UniX Systems
by dave taylor and
Brandon Perry
San Francisco
WICKED COOL SHELL SCRIPTS, 2ND EDITION. Copyright © 2017 by Dave Taylor and Brandon Perry.
All rights reserved. No part of this work may be reproduced or transmitted in any form or by any means,
electronic or mechanical, including photocopying, recording, or by any information storage or retrieval
system, without the prior written permission of the copyright owner and the publisher.
Fifth printing
26 25 24 23 22 5 6 7 8 9
ISBN-10: 1-59327-602-8
ISBN-13: 978-1-59327-602-7
Publisher: William Pollock
Production Editor: Laurel Chun
Cover Illustration: Josh Ellingson
Interior Design: Octopod Studios
Developmental Editor: Liz Chadwick
Technical Reviewer: Jordi Gutiérrez Hermoso
Additional Technical Reviewers: Therese Bao, Mark Cohen,
Matt Cone, Grant McWilliams, and Austin Seipp
Copyeditor: Paula L. Fleming
Compositors: Laurel Chun and Janelle Ludowise
Proofreader: James Fraleigh
Indexer: Nancy Guenther
For information on distribution, translations, or bulk sales, please contact No Starch Press, Inc. directly:
No Starch Press, Inc.
245 8th Street, San Francisco, CA 94103
phone: [phone]; [email protected]
www.nostarch.com
The Library of Congress has catalogued the first edition as follows:
Taylor, Dave.
Wicked cool shell scripts / Dave Taylor.
p. cm.
ISBN 1-59327-012-7
1. UNIX (Computer file) 2. UNIX Shells. I. Title.
QA76.76.O63T3895 2004
005.4'32--dc22
2003017496
No Starch Press and the No Starch Press logo are registered trademarks of No Starch Press, Inc. Other
product and company names mentioned herein may be the trademarks of their respective owners. Rather
than use a trademark symbol with every occurrence of a trademarked name, we are using the names only
in an editorial fashion and to the benefit of the trademark owner, with no intention of infringement of the
trademark.
The information in this book is distributed on an “As Is” basis, without warranty. While every precaution
has been taken in the preparation of this work, neither the authors nor No Starch Press, Inc. shall have any
liability to any person or entity with respect to any loss or damage caused or alleged to be caused directly or
indirectly by the information contained in it.
About the Authors
Dave Taylor has been in the computer industry since 1980. He was a
contributor to BSD 4.4 UNIX, and his software is included in all major
UNIX distributions. He is an award-winning public speaker and has written
thousands of magazine and newspaper articles. He is the author of more
than 20 books, including Learning Unix for OS X (O’Reilly Media), Solaris 9
for Dummies (Wiley Publishing), and Sams Teach Yourself Unix in 24 Hours
(Sams Publishing). A popular columnist for Linux Journal magazine,
he also maintains a customer tech support and gadget reviews website,
askdavetaylor.com.
Brandon Perry started writing C# applications with the advent of the open
source .NET implementation Mono. In his free time, he enjoys writing
modules for the Metasploit framework, parsing binary files, and fuzzing
things.
About the technical reviewer
Jordi Gutiérrez Hermoso is a coder, mathematician, and hacker-errant.
He has run Debian GNU/Linux exclusively since 2002, both at home
and at work. Jordi is involved with GNU Octave, a free numerical com-
puting environment largely compatible with Matlab, and with Mercurial,
a distributed version-control system. He enjoys pure and applied math-
ematics, skating, swimming, and knitting. Lately he’s been thinking a lot
about greenhouse gas emissions and rhino conservation efforts.

Brief Contents
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiii
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxv
Chapter 0: A Shell Scripts Crash Course . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Chapter 1: The Missing Code Library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Chapter 2: Improving on User Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Chapter 3: Creating Utilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
Chapter 4: Tweaking Unix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Chapter 5: System Administration: Managing Users . . . . . . . . . . . . . . . . . . . . . . . . . 117
Chapter 6: System Administration: System Maintenance . . . . . . . . . . . . . . . . . . . . . . 145
Chapter 7: Web and Internet Users . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
Chapter 8: Webmaster Hacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
Chapter 9: Web and Internet Administration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217
Chapter 10: Internet Server Administration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
Chapter 11: OS X Scripts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
Chapter 12: Shell Script Fun and Games . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
Chapter 13: Working with the Cloud . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299
Chapter 14: ImageMagick and Working with Graphics Files . . . . . . . . . . . . . . . . . . 313
Chapter 15: Days and Dates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
Appendix A: Installing Bash on Windows 10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341
Appendix B: Bonus Scripts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355