https://www.tutorialspoint.com/unix/unix-using-variables.htm
https://www.serverlab.ca/tutorials/linux/administration-linux/how-to-set-environment-variables-in-linux/
export NAME=VALUE
export JAVA_HOME=/opt/openjdk11
unset VARIABLE_NAME
unset JAVA_HOME
::Listing All Set Environment Variables::
set
variable_name=variable_value
NAME="John Doe"
echo $NAME
readonly NAME
export NAME
Linux Variable Types
When a shell is running, three main types of variables are present −
Local Variables
Environment Variables
Shell Variables
