Environment Variables

An environment variable is a user-definable value that can affect the way running processes will behave on a computer. In Linux, we can check them with the command env and identify them because they start with the $ symbol.

Some of the most common preset environment variables are:

• $PATH: List of directories for searching executable files or other directories, by default contains directories of system applications and installed apps

• $USER: The user currently logged in

• $PWD: Current working directory

• $HOME: Home Directory path

• $$: Current shell PID

• $SHELL: The path to the current shell, determines which command-line interface you are using

• $TERM: Indicates the type of terminal to emulate when running the shell

• $LANG: Specifies the language and locale settings for the user environment

• $EDITOR: The default text editor set for the user

• $MAIL: The path to the user's mailbox

• $DISPLAY: Used in graphical environments to specify the display server to connect to

• $HISTSIZE: Defines the number of commands to remember in the command history for the current user session