Book Image

Linux Shell Scripting Bootcamp

By : James K Lewis
Book Image

Linux Shell Scripting Bootcamp

By: James K Lewis

Overview of this book

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.
Table of Contents (19 chapters)
Linux Shell Scripting Bootcamp
About the Author
About the Reviewer
Customer Feedback

The sleep command

I showed the sleep command earlier, let's look at that in much more detail. In general, the sleep command is used to introduce a delay in the script. For example, in the previous script if I had not used sleep the output would have scrolled off too quickly to see what was going on.

The sleep command takes a parameter indicating how long to make the delay. For example, sleep 1 means to introduce a delay of one second. Here are a few examples:

sleep 1       # sleep 1 second (the default is seconds)
sleep 1s      # sleep 1 second
sleep 1m      # sleep 1 minute
sleep 1h      # sleep 1 hour
sleep 1d      # sleep 1 day

The sleep command actually has a bit more capability that what is shown here. For more information, please consult the man page (man sleep).

Here's a script showing in more detail how sleep works:

Chapter 3 - Script 10

# 5/3/2017
echo "script10 - Linux Scripting Book"

echo "Sleeping seconds..."
while [ $x -le 5 ]
 let x++
 sleep 1