Environment Variables

Environment variables are a way for the shell and other processes to store and access values that can be used by programs running on the system. Some environment variables are set by default by the system, while others are set by the user or other processes.

To see a list of all the current environment variables, you can use the env command:

$ env 

This will output a list of all the environment variables currently set on the system, along with their values.

You can also use the printenv command to see the values of a specific environment variable:

$ printenv PATH /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games 

In this example, we're using printenv to display the value of the PATH environment variable, which is used by the shell to determine where to find executable files.

To set a new environment variable, you can use the export command followed by the variable name and its value:

$ export MY_VAR="Hello, World!" 

This will create a new environment variable called MY_VAR and set its value to "Hello, World!".

To make the environment variable permanent, you can add the export command to your shell's startup file. For example, if you're using the Bash shell, you can add the following line to your ~/.bashrc file:

export MY_VAR="Hello, World!" 

This will ensure that the environment variable is set every time you open a new terminal window or start a new shell session.

You can also unset an environment variable using the unset command:

$ unset MY_VAR 

This will remove the MY_VAR environment variable from the system.

Overall, environment variables are a powerful tool for configuring your system and customizing the behavior of your shell and other programs. By understanding how to work with environment variables, you can more effectively manage your system and improve your productivity on the command line.