A Beginner’s Guide to Linux Environment Variables

Hey there! If you’re new to Linux, you may have heard the term “environment variables” and wondered what they are and how they work. In short, environment variables are like secret agents that run in the background, passing information to programs about the system’s environment, such as paths to important files, preferred text editors, and more.

In this article, we’ll explore the ins and outs of environment variables in Linux. We’ll go over what they are and how they work, and we’ll show you how to set them up to get the most out of your system. From managing system configurations to running custom scripts, environment variables are a powerful tool that every Linux user should know how to use. So, whether you’re a seasoned Linux user or just getting started, join us as we dive into the world of environment variables on Linux.

What are Environment Variables in Linux?

Environment variables in Linux are system-wide or user-specific variables that store information related to the environment. This information can be system settings, user preferences, or even data that is required by a particular application. Environment variables are used to configure the behavior of applications, scripts, and system processes.

The Linux operating system uses a shell environment to manage environment variables. When a user logs in to the system, the shell reads the configuration files and sets up the environment variables according to the settings in these files. Environment variables can be used to specify default values for many system settings, such as the path to executable files, the location of configuration files, and user preferences.

How Linux Environment Variables Work

Linux environment variables work by storing data in memory that can be accessed by other processes and applications. When an application or process needs to access an environment variable, it calls a system function to retrieve the value of the variable from memory. Similarly, when an application or process needs to set the value of an environment variable, it calls a system function to update the value of the variable in memory.

Setting up Environment Variables

Setting up environment variables in Linux can be done using the export command. The export command is used to create an environment variable and assign it a value. For example, to set the PATH environment variable to include the /usr/local/bin directory, the following command can be used:

export PATH=$PATH:/usr/local/bin

In the above command, the $PATH variable contains the current value of the PATH environment variable. The colon separates the current value from the new value, which is /usr/local/bin in this case. The above command adds the /usr/local/bin directory to the existing path.

Environment variables can also be set up by adding them to the .bashrc or .bash_profile files in the user’s home directory. These files are executed when a user logs in to the system and can be used to set up custom environment variables. For example, to set up a custom environment variable called MYVAR, the following line can be added to the .bashrc file:

export MYVAR="Hello World"

Viewing Environment Variables

To view the current environment variables in Linux, the env command can be used. The env command displays all the current environment variables, including system and user-specific variables. For example, to view the current value of the PATH environment variable, the following command can be used:

env | grep PATH

The above command searches for the string “PATH” in the output of the env command and displays only the lines that contain this string.

Commonly Used Environment Variables in Linux

There are several environment variables that are commonly used in Linux. Some of these variables are:

1. HOME: This variable stores the path to the user’s home directory.
2. PATH: This variable contains a list of directories where executable files are stored.
3. USER: This variable stores the username of the current user.
4. SHELL: This variable stores the path to the user’s default shell.
5. TERM: This variable stores the type of terminal emulator that is currently being used.
6. DISPLAY: This variable is used to specify the X Window System display server.

Examples of Environment Variables in Linux

Environment variables are dynamic values that can affect the way processes behave. They are defined in the shell and inherited by child processes, so they are essential for scripting and automation. Each variable is a string with a name and a value, which can be set, modified, or deleted. There are two types of environment variables: user-specific and system-wide. User-specific variables are set for each user, while system-wide variables are set for the entire system.

Here are some examples of commonly used environment variables in Linux:

• PATH: This environment variable specifies the directories where executable files are located. When you enter a command in the terminal, the shell searches for the command in the directories specified in the PATH variable. For example, if you want to run a command called “my-program”, you can add the directory where the command is located to the PATH variable, and then you can run the command from anywhere in the system.

• HOME: This environment variable specifies the user’s home directory. It is used by many programs to determine the location of user-specific configuration files, cache, and data directories.
• LANG: This environment variable specifies the default language used by the system. It affects the behavior of programs that support internationalization and localization.
• PS1: This environment variable specifies the prompt that is displayed in the terminal. You can customize the prompt by setting the PS1 variable to a string that includes escape sequences. For example, you can set the prompt to display the current working directory, the date and time, the username, and more.
• TERM: This environment variable specifies the type of terminal that is being used. It affects the behavior of programs that interact with the terminal, such as text editors, pagers, and screen readers.