node doesn't work after running rosrun

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I'm using a package named robot_localizaton offered by ROS downloaded from github.Here's the problem: I put a couple lines of code to export position data,it goes like this:

"cout<<"robot's y position: "<<filteredposition.pose.pose.position.y&lt;<endl;"&lt; p="">

but I didn't get desired output in the terminal after rosrun robot_localization ekf_localization_node(already get params loaded).I assume the node doesn't operate at all. What confuses me most is that running rostopic echo /odomfiltered leads to data stream output. Any answer would be appreciated,thank you so much.