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

More syntax errors

A fundamental problem with shell scripts is syntax errors don't usually show up until the line with the problem is parsed by the interpreter. Here's a common error that I still find myself doing more than I should. See if you can locate the problem by just reading the script:

Chapter 9 - Script 3

# 6/7/2017
echo "Chapter 9 - Script 3"

if [ $# -ne 1 ] ; then
 echo "Usage: script3 parameter"
 exit 255

echo "parm: $parm"

if [ "$parm" = "home" ] ; then
 echo "parm is home."
elif if [ "$parm" = "cls" ] ; then
 echo "parm is cls."
elif [ "$parm" = "end" ] ; then
 echo "parm is end."
 echo "Unknown parameter: $parm"

echo "End of script3"
exit 0

Here's the output:

Did you find my mistake? When I code an if...elif...else statement, I tend to copy and paste the first if statement. I then prepend elif to the next statement but forget to remove the if. This gets me almost every time.

Look at how I ran this script. I started first with just the name...