What are environmental variables in Linux?

What are Environmental Variables in Linux?

Environmental variables in Linux are a crucial part of the operating system that allow users to customize and configure the system to their liking. These variables are used to store and manipulate data that is not part of the kernel, but rather is specific to the user or the application. In this article, we will delve into the world of environmental variables in Linux and explore their significance, types, and usage.

What are Environmental Variables?

Environmental variables are variables that are defined outside of the kernel and are stored in the /etc/environment file. They are used to store data that is not part of the kernel, such as user preferences, application settings, and system configuration. Environmental variables are typically used to customize the system to the user’s liking, and they can be used to override the default settings of the system.

Types of Environmental Variables

There are several types of environmental variables in Linux, including:

• Environment variables: These are variables that are defined outside of the kernel and are stored in the /etc/environment file. They are used to store data that is not part of the kernel, such as user preferences, application settings, and system configuration.
• Shell variables: These are variables that are defined within the shell and are used to store data that is specific to the current shell session.
• System variables: These are variables that are defined outside of the kernel and are used to store data that is specific to the system as a whole.

How to Access Environmental Variables

Environmental variables can be accessed using the export command, which is used to define and set environmental variables. The export command is used to define variables that are specific to the current shell session, and they are stored in the shell’s environment.

Here is an example of how to access an environmental variable using the export command:

export MY_VAR="Hello, World!"

This will define a variable named MY_VAR with the value "Hello, World!" and store it in the shell’s environment.

How to Set Environmental Variables

Environmental variables can be set using the export command, which is used to define and set variables that are specific to the current shell session. The export command is used to set variables that are specific to the current shell session, and they are stored in the shell’s environment.

Here is an example of how to set an environmental variable using the export command:

export MY_VAR="Hello, World!"

This will define a variable named MY_VAR with the value "Hello, World!" and store it in the shell’s environment.

How to Check Environmental Variables

Environmental variables can be checked using the echo command, which is used to display the values of variables that are defined in the shell’s environment.

Here is an example of how to check an environmental variable using the echo command:

echo $MY_VAR

This will display the value of the MY_VAR variable, which is "Hello, World!".

How to Delete Environmental Variables

Environmental variables can be deleted using the unset command, which is used to remove variables that are defined in the shell’s environment.

Here is an example of how to delete an environmental variable using the unset command:

unset MY_VAR

This will remove the MY_VAR variable from the shell’s environment.

How to Set Environment Variables in System Configuration

Environmental variables can also be set in system configuration files, such as /etc/environment and /etc/sysconfig. These files are used to store data that is specific to the system as a whole, and they can be used to override the default settings of the system.

Here is an example of how to set an environmental variable in the /etc/sysconfig file:

export MY_VAR="Hello, World!"

This will define a variable named MY_VAR with the value "Hello, World!" and store it in the system’s configuration files.

How to Check System Variables

System variables can be checked using the echo command, which is used to display the values of variables that are defined in the system’s configuration files.

Here is an example of how to check a system variable using the echo command:

echo $MY_VAR

This will display the value of the MY_VAR variable, which is "Hello, World!".

Conclusion

Environmental variables are a crucial part of the Linux operating system, and they allow users to customize and configure the system to their liking. These variables are used to store data that is not part of the kernel, such as user preferences, application settings, and system configuration. By understanding how to access, set, and check environmental variables, users can customize their Linux system to suit their needs.

Table: Environmental Variables in Linux

Variable	Type	Usage
MY_VAR	Environment variable	Defined outside of the kernel and stored in /etc/environment
MY_VAR	Shell variable	Defined within the shell and used to store data specific to the current shell session
MY_VAR	System variable	Defined outside of the kernel and used to store data specific to the system as a whole
export	Command	Defines and sets environmental variables that are specific to the current shell session
export	Command	Sets environmental variables that are specific to the current shell session
echo	Command	Displays the values of variables that are defined in the shell’s environment
unset	Command	Removes variables that are defined in the shell’s environment
/etc/environment	File	Stores environmental variables that are specific to the system as a whole
/etc/sysconfig	File	Stores system variables that are specific to the system as a whole