Linux Shell Scripting Bootcamp

Description

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 Getting started with shell scripting Working with variables Using loops and the sleep command Creating and calling subroutines Creating Interactive Scripts Automating Tasks with Scripts Working with Files Working with wget and curl Debugging scripts Scripting Best Practices 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