Variables store information. Environment variables are available for the whole environment.An environment variable consists of name=value pair.

Existing Environment Variables:

• SHELL=/bin/bash= default shell program, in this case bash
• HOME=/home/nana= current user's home directory
• USER=nana = currently logged in user
• printenv = List all environment variables
• printenv | less = List all environment variables with less program
• printenv [environment variable] = Display value of given environment variable, e.g. printenv USER
• printenv | grep USER = Filter environment variables, which have 'USER' in the name
• echo $USER = Print value of USER environment variable

Create own Environment Variables:

• export DB_USERNAME=dbuser = Set environment variable 'DB_USERNAME' with value 'dbuser'
• export DB_PASSWORD=secretpwdvalue = Set environment variable 'DB_PASSWORD' with value 'secretpwdvalue'
• export DB_NAME=mydb = Set environment variable 'DB_NAME' with value 'mydb'
• printenv | grep DB = Filter environment variables for 'DB' characters
• export DB_NAME=newdbname = Set environment variable 'DB_NAME' to new value 'newdbname'

Delete Environment Variables:

• unset DB_NAME = Delete variable with name 'DB_NAME'

Persisting Environment Variables:

Persisting Environment Variables with shell specific configuration file: Environment variables set in terminal are only available in the current terminal session.