How to read data from "/rosout" topic using c++ node.
I want to write a c++ node which subscribe the topic /rosout read data from it and print the extracted data on terminal using ROS_INFO().
Asked by kjitender469 on 2019-10-11 04:38:57 UTC
Answers
Hello,
ROS_INFO() will display the message in the terminal, but ROS_INFO() will also send a message to /rosout.
If you create a node that subscribe to /rosout and use ROS_INFO(), you will write an infinite loop because :
1 . Node receive message from /rosout
2 . Node print with ROS_INFO()
3 . ROS_INFO() Send a message to /rosout
4 . Go back to 1
For a simple example of how to do a subscriber, you can subscribe to /rosout and simply use std::cout for displaying the message (or your favorite logging system that doesn't use /rosout).
If you want to extract Warning, Error or Fatal level message, you can use a message filter, or just discarding message with logger level less than warning in the beginning of the callback function.
Asked by lmathieu on 2019-10-11 05:54:46 UTC
Comments
Ok. I have written a node using C++ but i am unable to extract "msg" field data from it. The type of rosout is rosmsgs_graph/Log. I want to extract the data from "msg" field and convert it into string.
Asked by kjitender469 on 2019-10-11 07:24:11 UTC
Comments
You just need a subscriber to the topic to read the data it contains. You can follow example here
Asked by Choco93 on 2019-10-11 04:59:20 UTC