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- Herausgeber: Packt Publishing
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
A quick and straightforward approach to writing shell scripts to accomplish different types of tasks on a Linux system.
About This Book
- Understand expressions and variables and how to use them practically
- Familiarize yourself with the various text filtering tools available in Linux
- A fast-paced and concise guide that gets you well versed with linux shell scripting.
Who This Book Is For
This book is for both GNU/Linux users who want to do amazing things with the shell and for advanced users looking for ways to make their lives with the shell more productive.
What You Will Learn
- Get acquainted with the basics of a shell script to serve as a refresher for more advanced topics
- Learn different ways to create and run a script
- Discuss the passing and verification of parameters, along with the verification of other items.
- Understand the different forms of conditions and loops, and go over the sleep command in detail
- Learn about different ways to handle the reporting of return codes
- Create an interactive script by reading the keyboard and use subroutines and interrupts
- Create scripts to perform backups and go over the use of encryption tools and checksums
- Use wget and curl in scripts to get data directly from the Internet
In Detail
Linux Shell Scripting Bootcamp is all about learning the essentials of script creation, validating parameters, and checking for the existence of files and other items needed by the script.
We will use scripts to explore iterative operations using loops and learn different types of loop statements, with their differences. Along with this, we will also create a numbered backup script for backup files.
Further, you will get well-versed with how variables work on a Linux system and how they relate to scripts. You'll also learn how to create and call subroutines in a script and create interactive scripts. The most important archive commands, zip and tar, are also discussed for performing backups. Later, you will dive deeper by understanding the use of wget and curl scripts and the use of checksum and file encryption in further chapters.
Finally, you will learn how to debug scripts and scripting best practices that will enable you to write a great code every time! By the end of the book, you will be able to write shell scripts that can dig data from the web and process it efficiently.
Style and approach
This book is all about fast and intensive learning. This means we don't waste time in helping readers get started. The new content is basically about filling in with highly-effective examples to build new things, solving problems in newer and unseen ways, and solving real-world examples.
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Seitenzahl: 154
Veröffentlichungsjahr: 2017
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Table of Contents
Linux Shell Scripting Bootcamp
Linux Shell Scripting Bootcamp
Copyright © 2017 Packt Publishing
All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.
Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.
Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.
First published: July 2017
Production reference: 1170717
Published by Packt Publishing Ltd.
Livery Place
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Birmingham B3 2PB, UK.
ISBN 978-1-78728-110-3
www.packtpub.com
Credits
Author
James Kent Lewis
Reviewer
Thushara Jayawardena
Commissioning Editor
Pratik Shah
Acquisition Editor
Namrata Patil
Content Development Editor
Amrita Noronha
Technical Editor
Jovita Alva
Copy Editor
SAFIS
Laxmi Subramanian
Project Coordinator
Shweta H Birwatkar
Proofreader
SAFIS
Laxmi Subramanian
Indexer
Pratik Shirodkar
Graphics
Tania Dutta
Production Coordinator
Arvindkumar Gupta
Cover Work
Arvindkumar Gupta
About the Author
James Kent Lewis has been in the computer industry for over 35 years. He started out writing basic programs in high school and used punch cards in college for his Pascal, Fortran, COBOL, and assembly language classes. Jim taught himself the C programming language by writing various utilities, including a fully-functional text editor, which he uses everyday.
He started out using DOS and AIX, and then OS/2. Linux is now his operating system of choice.
Jim has worked in the past for several companies, including IBM, Texas Instruments, Tandem, Raytheon, Hewlett-Packard, and others. Most of these positions dealt with low-level device drivers and operating system internals. In his spare time he likes to create video games in Java.
Jim has written articles for IBM Developer Works and has one patent. He has worked on Linux Utilities Cookbook with Packt Publishing.
Acknowledgement
First, I would like to thank Red Hat and CentOS for creating a great operating system. I used CentOS 6.8 exclusively in the writing of this book and it worked flawlessly. I would also like to thank my brother, David, for letting me bounce ideas off of him. Last, but certainly not least, I would like to thank my girlfriend, Gabriele. Her patience was greatly appreciated, and she also helped by letting me log into her Fedora laptop from time to time.
About the Reviewer
Thushara Jayawardena is a very strong asset in software development as well as in the software service industry with more than 15 years of experience in systems administrating. That experience has contributed to this book. The main responsibility of the current day job is performance engineering for a leading European ERP software provider. It translates to system configuration and installations, followed by end-to-end automated performance testing. Scripting is an integral part of all these components.
His spare time is spent partly developing a user guide for tourist attractions for Android and IOS devices. The cloud backend for the solution comprises Mongo Cloud DB services and Heroku app dynos, run on Nodejs. Thushara also spends time with systems on chip devices such as Raspberry Pi and Arduino-like boards. Here, the focus is on IOT-type solutions.
Thushara is a loving father and husband who values his family very much and makes sure homebrewing doesn't come between him and family. He's been living nomadic since 2007, or rather migrated to Sweden with his family and moved around a bit in Sweden, and currently is living south of the beautiful port city of Gothenburg. He enjoys Scandinavian life, simplicity, and respect very much and is keen on improving his skiing skills during the winters up in the Swedish mountains. He has also worked on Raspberry Pi Android Projects.
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Preface
In Linux Shell Scripting Bootcamp, you will begin by learning the essentials of script creation. You will learn how to validate parameters and also how to check for the existence of files. Moving on, you will get well-versed with how variables work on a Linux system and how they relate to scripts. You'll also learn how to create and call subroutines and create interactive scripts. Finally, you will learn how to debug scripts and scripting best practices, which will enable you to write a great code every time! By the end of the book you will be able to write shell scripts that can dig data from the Web and process it efficiently.
What this book covers
Chapter 1, Getting Started with Shell Scripting, begins with the basics of script design. How to make a script executable is shown as is creating an informative Usage message. The importance of return codes is also covered with the use and validation of parameters.
Chapter 2, Working with Variables, discusses how to declare and use both environment and local variables. We also speak about how math is performed and how to work with arrays.
Chapter 3, Using Loops and the sleep Command, introduces the use of loops to perform iterative operations. It also shows how to create a delay in a script. The reader will also learn how to use loops and the sleep command in a script.
Chapter 4, Creating and Calling Subroutines,starts with some very simple scripts and then proceeds to cover some simple subroutines that take parameters.
Chapter 5, Creating Interactive Scripts, explains the use of the read built-in command to query the keyboard. Further, we explore some of the different options to read and also cover the use of traps.
Chapter 6, Automating Tasks with Scripts, describes the creation of scripts to automate a task. The proper way to use cron to run a script automatically at a specific time is covered. The archive commands zip and tar are also discussed for performing compressed backups.
Chapter 7, Working with Files, introduces the use of the redirection operator for writing out a file and use of read command for reading a file. Checksums and file encryption are also discussed, and a way to convert the contents of a file into a variable is also covered.
Chapter 8, Working with wget and curl, discusses the usage of wget and curl in scripts. Along with this, return codes are also discussed with a couple of example scripts.
Chapter 9, Debugging Scripts, explains some techniques to prevent common syntax and logic errors. A way to send output from a script to another terminal using the redirection operator was also discussed.
Chapter 10, Scripting Best Practices, discusses some practices and techniques that will help the reader create good code every time.
What you need for this book
Any Linux machine that has Bash should be able to run these scripts. This includes desktops, laptops, embedded devices, BeagleBone, and so on. Windows machines running Cygwin or some other emulated Linux environment will also work.
There are no minimum memory requirements.
Who this book is for
This book is for both GNU/Linux users who want to do amazing things with the shell and for advanced users looking for ways to make their lives with the shell more productive
Conventions
In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.
Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: You can see that the echo statement Start of x loop was displayed A block of code is set as follows:
Any command-line input or output is written as follows:
New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: "Clicking the Next button moves you to the next screen."
Note
Warnings or important notes appear in a box like this.
Tip
Tips and tricks appear like this.
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To send us general feedback, simply e-mail <[email protected]>, and mention the book's title in the subject of your message.
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Once the file is downloaded, please make sure that you unzip or extract the folder using the latest version of:
The code bundle for the book is also hosted on GitHub at https://github.com/PacktPublishing/Linux-Shell-Scripting-Bootcamp. We also have other code bundles from our rich catalog of books and videos available at https://github.com/PacktPublishing/. Check them out!
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Questions
If you have a problem with any aspect of this book, you can contact us at <[email protected]>, and we will do our best to address the problem.
Chapter 1. Getting Started with Shell Scripting
This chapter is a brief introduction to shell scripting. It will assume the reader is mostly familiar with script basics and will serve as a refresher.
The topics covered in this chapter are as follows:
Getting started
You will always be able to create these scripts under a guest account, and most will run from there. It will be clearly stated when root access is needed to run a particular script.
The book will assume that the user has put a (.) at the beginning of the path for that account. If not, to run a script prepend ./ to the filename. For example:
The scripts will be made executable using the chmod command.
