How to Set and Unset Local, User and System Wide Environment Variables in Linux

Environment Variables are some special variables that are defined in shell and are needed by programs while executing. They can be system defined or user defined. System defined variables are those which are set by system and are used by system level programs. in Broader terms, an environment variable can be in three types, local environment variable, user environment variable and system wide environment variable, which will be discussed in this article.