Hi Aankin_wang, According to ROS community support guidelines http://wiki.ros.org/Support this question should be better asked in http://answers.ros.org > Please do not post questions on the discourse.ros.org they should go to ROS Answers. > ROS Discourse is for news and general interest discussions. ROS Answers provides a forum which can > be filtered by tags to make sure the relevant people are included and not overload everyone. Best regards, Martin --- [Visit Topic](https://discourse.ros.org/t/how-to-access-the-instant-ros-callback-value/1888/2) or reply to this email to respond. If you do not want to receive messages from ros-users please use the unsubscribe link below. If you use the one above, you will stop all of ros-users from receiving updates. ______________________________________________________________________________ ros-users mailing list ros-users@lists.ros.org http://lists.ros.org/mailman/listinfo/ros-users Unsubscribe: