Linux Command Line and Shell Scripting Bible, 3rd Edition

Using Linux Environment Variables

IN THIS CHAPTER

Looking at environment variables

Creating your own local variables

Removing variables

Exploring default shell environment variables

Setting the PATH environment variable

Locating environment files

Using variable arrays

Linux environment variables help define your Linux shell experience. Many programs and scripts use environment variables to obtain system information and store temporary data and configuration information. Environment variables are set in lots of places on the Linux system, and you should know where these places are.

This chapter walks you through the world of Linux environment variables, showing where they are, how to use them, and even how to create your own. The chapter finishes off with how to use variable arrays.

Exploring Environment Variables

The bash shell uses a feature called environment variables to store information about the shell session and the working environment (thus the name environment variables). This feature also allows you to store data in memory that can be easily accessed by any program or script running from the shell. It is a handy way to store needed persistent data.

There are two environment variable types in the bash shell:

• Global variables
• Local variables

This section describes each type of environment variable and shows how to see and use them.

NOTE

Even though the bash shell uses ...