Create ROS workspace - check if properly overlayed

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I have ROS kinetic and i am following the tutorial: [ http://wiki.ros.org/ROS/Tutorials/Ins... ] After I enter:

echo $ROS_PACKAGE_PATH

I expect this:

/home/youruser/catkin_ws/src:/opt/ros/kinetic/share

But instead, I'm getting a blank line, as a return. I've already checked if the file setup.bash is included in /opt/ros/kinetic/ as well as in /catkin_ws/devel/. Also, i've sourced it: $ source devel/setup.bash, but still no output after echo. Any idea? thanks a lot