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

Defining BRE Patterns

The most basic BRE pattern is matching text characters in a data stream. This section demonstrates how you can define text in the regular expression pattern and what to expect from the results.

Plain text

Chapter 18 demonstrated how to use standard text strings in the sed editor and the gawk program to filter data. Here's an example to refresh your memory:

$ echo "This is a test" | sed -n '/test/p'
This is a test
$ echo "This is a test" | sed -n '/trial/p'
$ echo "This is a test" | gawk '/test/{print $0}'
This is a test
$ echo "This is a test" | gawk '/trial/{print $0}'

The first pattern defines a single word, test. The sed editor and gawk program scripts each use their own version of the print command to print any lines that match the regular expression pattern. Because the echo statement contains the word “test” in the text string, the data stream text matches...