Multiple node-ID assignation

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I'm a neophyte of ROS programming: i need to use the same ROS-node for multiple independent agents; in other words i want to automatically replicate a node (during the launching), each one with its own ID. In addition i'd like to use this ID in each node in such a way that i can define a topic for each agent (node) using a string and an integer (ID) variable. can someone help me? thanks