Book Image

Linux Shell Scripting Cookbook, Second Edition - Second Edition

Book Image

Linux Shell Scripting Cookbook, Second Edition - Second Edition

Overview of this book

The shell remains one of the most powerful tools on a computer system — yet a large number of users are unaware of how much one can accomplish with it. Using a combination of simple commands, we will see how to solve complex problems in day to day computer usage.Linux Shell Scripting Cookbook, Second Edition will take you through useful real-world recipes designed to make your daily life easy when working with the shell. The book shows the reader how to effectively use the shell to accomplish complex tasks with ease.The book discusses basics of using the shell, general commands and proceeds to show the reader how to use them to perform complex tasks with ease.Starting with the basics of the shell, we will learn simple commands with their usages allowing us to perform operations on files of different kind. The book then proceeds to explain text processing, web interaction and concludes with backups, monitoring and other sysadmin tasks.Linux Shell Scripting Cookbook, Second Edition serves as an excellent guide to solving day to day problems using the shell and few powerful commands together to create solutions.
Table of Contents (16 chapters)
Linux Shell Scripting Cookbook
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
Index

Generating files of any size


For various reasons, you may need to generate a file filled with random data. It may be for creating a test file to perform tests, such as an application efficiency test that uses a large file as input, or to test the splitting of files into many parts, or to create loopback filesystems (loopback files are files that can contain a filesystem itself and these files can be mounted similarly to a physical device using the mount command). It takes effort to create such files by writing specific programs. So we use general utilities.

How to do it...

The easiest way to create a large-size file with the given size is to use the dd command. The dd command clones the given input and writes an exact copy to the output. Input can be stdin, a device file, a regular file, or so on. Output can be stdout, a device file, a regular file, or so on. An example of the dd command is as follows:

$ dd if=/dev/zero of=junk.data bs=1M count=1
1+0 records in
1+0 records out
1048576 bytes...