How to create a custom environment variable?

Creating Custom Environment Variables in Linux

In the Linux operating system, environment variables are a set of key-value pairs that provide information about the user's working environment. These variables are accessible to all running processes and can be used to customize the behavior of applications and the shell itself.

While Linux comes with a set of predefined environment variables, you can also create your own custom environment variables to suit your specific needs. This can be particularly useful when you need to store and access information that is specific to your workflow or project.

Step 1: Understanding Environment Variables

Environment variables in Linux are stored in the shell's environment, which is a collection of key-value pairs that are accessible to all processes spawned by the shell. These variables can be used to store a wide range of information, such as file paths, configuration settings, or user preferences.

Some common examples of environment variables in Linux include:

PATH: Specifies the directories where the shell should search for executable files.
HOME: Represents the user's home directory.
SHELL: Specifies the default shell for the user.
EDITOR: Specifies the default text editor for the user.

Step 2: Creating a Custom Environment Variable

To create a custom environment variable in Linux, you can use the export command in the shell. The syntax for creating a new environment variable is as follows:

export VARIABLE_NAME="value"

Here's an example of creating a custom environment variable called MY_CUSTOM_VAR and assigning it a value:

export MY_CUSTOM_VAR="Hello, World!"

Once you've created the variable, you can access its value using the $ symbol:

echo $MY_CUSTOM_VAR

This will output the value of the MY_CUSTOM_VAR environment variable, which is "Hello, World!".

Step 3: Making the Custom Environment Variable Persistent

By default, the custom environment variable you created will only be available in the current shell session. If you want the variable to be available across multiple shell sessions, you'll need to make it persistent.

To do this, you can add the export command to one of the shell configuration files, such as ~/.bashrc (for Bash) or ~/.zshrc (for Zsh). This ensures that the variable is set every time you start a new shell session.

Here's an example of adding the MY_CUSTOM_VAR environment variable to the .bashrc file:

echo "export MY_CUSTOM_VAR='Hello, World!'" >> ~/.bashrc

After making this change, the MY_CUSTOM_VAR environment variable will be available in all new shell sessions.

Visualizing the Concept with a Mermaid Diagram

Here's a Mermaid diagram that illustrates the process of creating a custom environment variable in Linux:

graph TD A[Start] --> B[Open a shell] B --> C[Use the 'export' command to create a new environment variable] C --> D[Assign a value to the variable] D --> E[Access the variable using the '$' symbol] E --> F[Make the variable persistent by adding it to a shell configuration file] F --> G[End]

By following these steps, you can create and manage custom environment variables in your Linux environment, allowing you to customize your workflow and access important information more easily.