Book Image

Bash Cookbook

By : Ron Brash, Ganesh Sanjiv Naik
Book Image

Bash Cookbook

By: Ron Brash, Ganesh Sanjiv Naik

Overview of this book

In Linux, one of the most commonly used and most powerful tools is the Bash shell. With its collection of engaging recipes, Bash Cookbook takes you through a series of exercises designed to teach you how to effectively use the Bash shell in order to create and execute your own scripts. The book starts by introducing you to the basics of using the Bash shell, also teaching you the fundamentals of generating any input from a command. With the help of a number of exercises, you will get to grips with the automation of daily tasks for sysadmins and power users. Once you have a hands-on understanding of the subject, you will move on to exploring more advanced projects that can solve real-world problems comprehensively on a Linux system. In addition to this, you will discover projects such as creating an application with a menu, beginning scripts on startup, parsing and displaying human-readable information, and executing remote commands with authentication using self-generated Secure Shell (SSH) keys. By the end of this book, you will have gained significant experience of solving real-world problems, from automating routine tasks to managing your systems and creating your own scripts.
Table of Contents (15 chapters)
Title Page
Copyright and Credits
Packt Upsell
Contributors
Preface
Index

Calculating statistics and reducing duplicates based on file contents


At first glance, calculating statistics based on the contents of a file might not be among the most interesting tasks one could accomplish with Bash scripting, however, it can be useful in several circumstances. Let's imagine that our program takes user input from several commands. We could calculate the length of the input to determine if it is too little or too much. Alternatively, we could also determine the size of a string to determine buffer sizes for a program written in another programming language (such as C/C++):

$ wc -c <<< "1234567890"
11 # Note there are 10 chars + a new line or carriage return \n
$ echo -n "1234567890" | wc -c
10

Note

We can use commands like wc to calculate the number of occurrences of words, total number of lines, and many other actions in conjunction to the functionality provided by your script.

Better yet, what if we used a command called strings to output all printable ASCII strings...