In the previous posts, we talked about some of the basic Linux commands, today we continue our journey, and we will talk about something essential in Linux, which is Linux environment variables.
Environment variables are a set of changing values that are baked into every Linux system. They are also used in other Unix-based systems for the very same purposes.
Environment variables are used by scripts and applications in various scenarios. Users and system processes are capable of accessing these environment variables, which is a stark contrast to regular shell variables.
Common Environment Variables
There exists a large variety of environment variables in the Linux operating system. They can be quite difficult to keep track of and commit to memory.
But it is extremely important that you are aware of the most common ones, as they can be very useful in a wide array of different system administration scenarios, as well as for personal use.
So, as either a brief refresher or an informative list, we’ll provide in easy examples below a complete list of some of the most common environment variables.
- USER – This environment variable is the currently logged user on a Linux system.
- HOME – This environment variable is the home directory of the current user on a Linux system.
- EDITOR – This environment variable is the default editor that is used to edit .txt files in your Linux terminal. This allows for programs to ascertain which text editor it is that you prefer to use for editing Linux applications.
- SHELL – This environment variable is the path of the present user’s shell. Many different shells can be used on a Linux system. A couple of the most common ones are Bash and ZSH. A shell is what interprets the commands you’re typing in, and the syntax and commands will change depending on which one you’re using. For nearly every Linux OS distro, Bash is the default and by far the most popular.
- LOGNAME – This environment variable is just the name of the current user.
- PATH – Containing a colon (:), this environment variable is a list of directories that will be searched when executing a command. When a command is run on the system, it will search those directories in the specified order of the file path. The system will continue to search these directories until it has found the first command that it can execute. Otherwise, you will receive an error message in your terminal that reads “command not found”.
- LANG – This environment variable is the current locale setting.
- TERM – This environment variable is the terminal emulation.
- MAIL – This environment variable is where the current user’s mail will be stored.
These are some of the environment variables that you should familiarize yourself with. It is also necessary to note that variables are case sensitive.
It is important that you make sure that you type the variable name with the right letter casing, otherwise, the output may be completely different.
Though it isn’t too big of a deal to remember as most of the environment variables are in the upper case.
Environment Variable Functions
Environment variables can be used to customize the way the system functions. They can also be used to modify code that tells applications on the system how to behave.
For example, many system applications and user-made scripts require access to the current user’s home directory.
We can achieve this by using the HOME environment. Utilizing HOME for a user made script will allow for any user on the system to run the script.
$ echo My home directory is $HOME > $HOME/info.log
$ cat $HOME/info.log My home directory is /home/nick
In this tutorial, we’ll explain how to view the currently configured environment variables and set new variables. Every Linux system has a set of these environment variables.
But you can also set new environment variables for temporary or permanent usage.
Using newly set environment variables is particularly useful when you need the environment variables to remain after a reboot. In the examples below, we’ll show how to employ both methods.
Get Environment Variables
command is one way to list all environment variables on Linux. You can see how we use its syntax in the Linux terminal in the example provided below.
Printing an entire list of every single environment variable on a Linux system may not be the best idea if you are just looking to get the information of a single variable.
But don’t worry, Linux has yet another convenient solution to a seemingly small problem; you can also use this command to list a specified variable by typing its name following the command.
The syntax for listing a specific variable is shown down below.
$ printenv SHELL
Checking specific variables though is not limited to just one at a time. You can also list multiple specific variables at the same time by using the
The syntax for checking multiple variables simultaneously is the same; you must simply list each environment variable after typing the printenv command. We’ll show an example of its syntax below.
$ printenv SHELL USER
In a Linux system, it is possible to utilize environment variables via command line or inside a Bash script. The way that this can be achieved is by prepending the environment variables with a dollar sign.
One of the most common environment variables that one might edit with is the $PATH variable. The $PATH variable allows the user to specify a directory that the Bash shell should search for applications when you execute commands.
$ printenv PATH /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin
Set Temporary Environment Variable
As we mentioned in an earlier section of this tutorial, we can set new environment variables in Linux. If you’ll also recall, it is possible to set both temporary and permanent variables.
The following command is an example of how to create a temporary environment variable that won’t persist after a user logout, new shell, or when you reboot the system. In the example below, we’ll set a new environment variable called
Using the following command will create a new shell variable. Though, it is important to note that this environment variable will only be usable in the current terminal.
We’ll show you how to create environment variables in the next couple of examples.
Now that we’ve made a new sample shell variable, we can set this variable as a new environment variable. To set shell variables in your Linux terminal, you’ll need to use the
$ export VARIABLE
In the examples above, we showed you how to set temporary environment variables using two separate commands. But like in many other different scenarios in Linux, there exists useful alternatives to make certain operations more efficient and convenient; we can configure the non-persistent environment variable using just a single command with the syntax shown below.
$ export VARIABLE='VARIABLENAME'
Setting Permanent Environment Variables
As we mentioned in the “Setting Temporary Environment Variables” section of this tutorial, we can configure new environment variables to be both temporary and permanent.
Since we already covered setting temporary environment variables.
We’ll show in the examples below how to configure new environment variables to be persistent. This can be done through a few different files in Linux. The file you choose to edit depends on how exactly you plan to access the environment variables.
– This file exists in the user’s home directory and will store variables that can only be used by the respective user.
These variables will be reloaded any time the user starts a new shell.
– The variables that are stored here can be accessed by every user and will be loaded when a new shell has been opened.
– Variables that are stored here can be accessed system-wide.
Now that although you are aware of the three files where Bash configuration files can be edited through, you might be wondering now how one might put a custom variable inside the
We can do this by adding a line to the bottom of either file by using the syntax shown in the example below. Take note that we added
before each new variable.
$ export VARIABLE=’VARIABLENAME’
Upon running this command, you can then reload the edited files into the present session with the command shown in the example down below.
$ source ~/ .bashrc OR # source /etc/profile
Another thing to note is that if you are placing a new environment variable in the
configuration file, you aren’t required to type the
command. An example of the syntax can be seen down below.
The methods that we have shown in the examples above will allow you to make your variable configurations persist until you remove them.
You can also utilize the
command to print a shell variable. This can be useful if, for example, you are making a script whose purpose is to generate a sample text file in your current user’s home directory. And multiple different users will be running the script.
Then the home directory is gonna change all the time depending on who is running it. The script will check the $HOME variable to see which user’s home directory it should use.
As we explained in an earlier section of this tutorial, the $HOME environment variable is the user’s home directory. This check must be accurate as you won’t be able to run certain operations such as the script in our example if the $HOME is not the correct one.
You can check the $HOME variable for yourself using the command line in your terminal with the
command. The syntax is provided in the example below.
$ echo $HOME
Throughout this tutorial, we showed you how to set and check Linux environment variables in your terminal by using a variety of commands and methods.
Removing Environment Variables
But you might be wondering what to do if you want to remove an environment variable that you have set. This can be achieved by using the
command in the Linux terminal.
$ unset VARIABLE
In Linux, there exists a certain philosophy that is not present in operating systems like Windows, for example. And that’s that there are no operations or processes that can be reversed or undone.
The thinking here is that if something was important and wasn’t supposed to have been erased, it should have been backed up.
So, it is important to note that if you use the
command, like we just said above, it cannot be undone. Accidentally unsetting and removing an environment variable will cause it to be lost forever. So use this command with extreme care.
In this tutorial, we explored how to set environment variables on Linux and view a list of all existing variables. Environment variables are a helpful aspect in Linux that allows us to access changing information across different systems.
They can be particularly useful for system administrators as they’ll constantly run system processes and programs that need the information that Linux system environment variables carry.
If everything in this post that we have said about environment variables seems like a lot, don’t worry, some things are more important to remember than others.
What you should mainly try to keep in mind are the commands for setting, unsetting, and checking environment variables. These are the main functions of environment variables in Linux that you’ll utilize the most frequently.
Mokhtar is the founder of LikeGeeks.com. He works as a Linux system administrator since 2010. He is responsible for maintaining, securing, and troubleshooting Linux servers for multiple clients around the world. He loves writing shell and Python scripts to automate his work.