Linux Shell Scripting Bootcamp

✍ Scribed by James Kent Lewis

• Publisher: Packt Publishing
• Year: 2017
• Tongue: English
• Leaves: 208
• Category: Library

✦ Synopsis

Key Features

• 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.

Book Description

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.

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

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. He himself learned 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.He has written articles for IBM Developer Works and has one patent.

Table of Contents

1. Getting started with shell scripting
2. Working with variables
3. Using loops and the sleep command
4. Creating and calling subroutines
5. Creating Interactive Scripts
6. Automating Tasks with Scripts
7. Working with Files
8. Working with wget and curl
9. Debugging scripts
10. Scripting Best Practices

✦ Table of Contents

Cover
Copyright
Credits
About the Author
Acknowledgement
About the Reviewer
www.PacktPub.com
Customer Feedback
Table of Contents
Preface
Chapter 1: Getting Started with Shell Scripting
Getting started
Using a good text editor
Demonstrating the use of scripts
Chapter 1 - Script 1
Chapter 1 - Script 2
Chapter 1 - Script 3
Chapter 1 - Script 4
Chapter 1 - Script 5
Chapter 1 - Script 6
Summary
Chapter 2: Working with Variables
Using variables in scripts
Chapter 2 - Script 1
Validating parameters using conditional statements
Chapter 2 - Script 2
Comparison operators for strings
Chapter 2 - Script 3
Chapter 2 - Script 4
Chapter 2 - Script 5
Environment variables
Chapter 2 - Script 6
Chapter 2 - Script 7
Summary
Chapter 3: Using Loops and the sleep Command
Using loops
Chapter 3 - Script 1
Chapter 3 - Script 2
Chapter 3 - Script 3
Screen manipulation
Chapter 3 - Script 4
Chapter 3 - Script 5
Indenting your code
Chapter 3 - Script 6
Using the for statement
Chapter 3 - Script 7
Chapter 3 - Script 8
Leaving a loop early
Chapter 3 - Script 9
The sleep command
Chapter 3 - Script 10
Chapter 3 - Script 11
Watching a process
Chapter 3 - Script 12
Creating numbered backup files
Chapter 3 – Script 13
Summary
Chapter 4: Creating and Calling Subroutines
Clearing the screen
Chapter 4 - Script 1
File redirection
Command piping
Chapter 4 - Script 2
Chapter 4 - Script 3
Subroutines
Chapter 4 - Script 4
Using parameters
Chapter 4 - Script 5
Chapter 4 - Script 6
Making a current backup of your work
Chapter 4 – Script 7
Summary
Chapter 5: Creating Interactive Scripts
Chapter 5 - Script 1
Chapter 5 - Script 2
Chapter 5 - Script 3
Chapter 5 - Script 4
Chapter 5 - Script 5
Chapter 5 - Script 6
Chapter 5 - Script 7
Chapter 5 - Script 8
Summary
Chapter 6: Automating Tasks with Scripts
Chapter 6 - Script 1
Chapter 6 - Script 2
Chapter 6 - Script 3
Chapter 6 - Script 4
Cron
Chapter 6 - Script 5
Chapter 6 - Script 6
Chapter 6 - Script 7
Summary
Chapter 7: Working with Files
Writing files
Chapter 7 - Script 1
Reading files
Chapter 7 - Script 2
Chapter 7 - Script 3
Chapter 7 - Script 4
Reading and writing files
Chapter 7 - Script 5
Reading and writing files interactively
Chapter 7 - Script 6
File checksums
File encryption
Chapter 7 - Script 7
Summary
Chapter 8: Working with wget and curl
Introducing the wget program
wget options
wget return codes
wget configuration files
Chapter 8 - Script 1
wget and recursion
wget options
curl
curl options
Chapter 8 - Script 2
Summary
Chapter 9: Debugging Scripts
Syntax errors
Chapter 9 - Script 1
Chapter 9 - Script 2
Automatic backups
More syntax errors
Chapter 9 - Script 3
Logic errors
Chapter 9 - Script 4
Using set to debug scripts
Chapter 9 - Script 5 and Script 6
Chapter 9 - Script 7
Chapter 9 - Script 8
Chapter 9 - Script 9
Summary
Chapter 10: Scripting Best Practices
Verifying backups
ssh and scp
Find and use a good text editor
Environment variables and aliases
ssh prompt
Testing an archive
Progress indicator
Chapter 10 - Script 1
Creating new commands from a template
Chapter 10 – Script 2
Alerting the user
Chapter 10 – Script 3
Summary
Index