Environment Variable

To see a shell’s variables, issue set command or run:

$ printenv

The scope of the variable is the shell in which it’s defined so to make a variable and its value available to other programs, you can enter:

$ export BPVAR   

Or the shortcut for defining and exporting simultaneously is:

$ export BPVAR=3

This variable is now called an environment variable because it is available to other programs in the shell’s environment. 

Example: To add directories to your shell’s search path temporarily, modify its PATH variable. For example, to append /usr/sbin run: 

$ PATH=$PATH:/usr/sbin

To make your change permanent, you should edit bash startup file which is a hidden file in the home directory: 

$ vi ~/.bash_profile 

Then log out and log back in to load the contents.