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

File checksums

You probably noticed the use of the sum command above. It displays the checksum and block count of files which can be used to determine if two or more files are the same file (that is, have the exact same contents).

Here is a real world example:

Suppose you are writing a book, and the files are being sent from the author to the publisher for review. The publisher makes some revisions and then sends the revised file back to the author. It is sometimes easy to get out of sync, and receive a file that doesn't look any different. If you run the sum command against the two files you can easily determine if they are the same.

Take a look at the following screenshot:

The first column is the checksum and the second column is the block count. If both of these are the same that means the contents of the files are identical. So, in this example bookfiles 1, 2, and 4 are the same. Bookfiles 3 and 5 are also the same. However, bookfiles 6, 7, and 8 don't match up with anything, and the last...