You can use the echo command to display the value of an environment variable. For example:
This displays the value of the environment variable PATH. The name of an environment variable is given in UPPER CASE.
The $ sign is a shell metacharacter that uses the value of the variable instead of its name.
The method for displaying the value of every variable varies according to which shell you are using.
For the Bourne shell use the command set to display the value of environment variables.
For the C and TC shell use the command printenv or env to display the value of environment variables and the command set to display the value of local shell variables.
If the list of variables is so long that it scrolls off the screen and you want to display the information one screenful at a time, pipe the output through a pager. For example:
set | more