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)
2
Part I: The Linux Command Line
13
Part II: Shell Scripting Basics
20
Part III: Advanced Shell Scripting
28
Part IV: Creating Practical Scripts
32
End User License Agreement

Summary

This chapter examined the world of Linux environment variables. Global environment variables can be accessed from any child shell spawned by the parent shell in which they're defined. Local environment variables can be accessed only from the process in which they're defined.

The Linux system uses both global and local environment variables to store information about the system environment. You can access this information from the shell command line interface, as well as within shell scripts. The bash shell uses the system environment variables defined in the original Unix Bourne shell, as well as lots of new environment variables. The PATH environment variable defines the search pattern the bash shell takes to find an executable command. You can modify the PATH environment variable to add your own directories, or even the current directory symbol, to make running your programs easier.

You can also create your own global and local environment variables for your own use...