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.

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.

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

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:

echo "Start of x loop"
x=0
while [ $x -lt 5 ]
do
 echo "x: $x"
 let x++
 

Any command-line input or output is written as follows:

guest1 $ ps auxw | grep script7

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."

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