Book Image

Linux Command Line and Shell Scripting Bible - Third Edition

By : Richard Blum, Christine Bresnahan
Book Image

Linux Command Line and Shell Scripting Bible - Third Edition

By: Richard Blum, Christine Bresnahan

Overview of this book

The Linux command line enables you to type specific shell commands directly into the system to manipulate files and query system resources. Command line statements can be combined into short programs called shell scripts, a practice increasing in popularity due to its usefulness in automation. Linux is a robust system with tremendous potential, and Linux Command Line and Shell Scripting Bible opens the door to new possibilities. Linux Command Line and Shell Scripting Bible is your essential Linux guide. It contains new functional examples that are fully updated to align with the latest Linux features. Beginning with command line fundamentals, the book moves into shell scripting and shows you the practical application of commands in automating frequently performed functions. This book is a complete guide providing detailed instruction and expert advice working within this aspect of Linux. Whether used as a tutorial or as a quick reference, this book contains information that every Linux user should know.
Table of Contents (34 chapters)
Part I: The Linux Command Line
Part II: Shell Scripting Basics
Part III: Advanced Shell Scripting
Part IV: Creating Practical Scripts
End User License Agreement

Looking at Multiline Commands

When using the basic sed editor commands, you may have noticed a limitation. All the sed editor commands perform functions on a single line of data. As the sed editor reads a data stream, it divides the data into lines based on the presence of newline characters. The sed editor handles each data line one at a time, processing the defined script commands on the data line, and then moving on to the next line and repeating the processing.

Sometimes, you need to perform actions on data that spans more than one line. This is especially true if you're trying to find or replace a phrase.

For example, if you're looking for the phrase Linux System Administrators Group in your data, it's quite possible that the phrase's words can be split onto two lines. If you processed the text using a normal sed editor command, it would be impossible to detect the split phrase.

Fortunately, the designers behind the sed editor thought of that situation and devised...