[ROS Q&A] 141 – How to Modify Logger Level in ROS (C++)

In this video we are going to see how to modify the Logger Level in ROS using C++.

This is a video trying to answer the following question posted at the ROS answers forum: https://answers.ros.org/question/98521/problems-with-logger-levels/

RELATED LINKS

▸ Original question: https://answers.ros.org/question/98521/problems-with-logger-levels/
▸ ROS Development Studio (RDS)
▸ Robot Ignite Academy

Step 1. Create a project in ROS Development Studio(ROSDS)

ROSDS helps you follow our tutorial in a fast pace without dealing without setting up an environment locally. If you haven’t had an account yet, you can create a free account here.

Step 2. Create package and file

Let’s create a package for testing in RDS by typing the following command.

cd ~/catkin_ws/src
catkin_create_pkg logs_test roscpp

Then we create a source file under the logs_test/src directory called logs.cpp with the following content.

#include <ros/ros.h>
#include <ros/console.h>
#include <stdlib.h>

int main(int argc, char** argv) {
    if (ros::console::set_logger_level(ROSCONSOLE_DEFAULT_NAME, ros::console::levels::Debug))
    {
        ros::console::notifyLoggerLevelsChanged();
    }
    
    ros::init(argc,argv,"log_demo");
    ros::NodeHandle nh;
    ros::Rate loop_rate(0.5); // We create a Rate object of 2Hz
    
    while (ros::ok()) //Endless loop until Ctrl+c
    {
        ROS_DEBUG("This is a DEBUG message");
        ROS_INFO("This is a INFO message");
        ROS_WARN("This is a WARN message");
        ROS_ERROR("This is a ERROR message");
        ROS_FATAL("This is a FATAL message");
        
        loop_rate.sleep();
        ros::spinOnce();
    }
    
    return 0;
}

In the CMakeLists.txt, please change the following content in build part.

...

## Declare a C++ executable
## With catkin_make all packages are built within a single CMake context
## The recommended prefix ensures that target names across packages don't collide
add_executable(logs_test src/logs.cpp)

...

## Add cmake target dependencies of the executable
## same as for the library above
add_dependencies(logs_test ${logs_test_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})

## Specify libraries to link a library or executable target against
target_link_libraries(logs_test
  ${catkin_LIBRARIES}
)

...

Then we can compile the code with the following command

cd ~/catkin_ws
catkin_make

While waiting for compilation, let’s create a launch file to launch the code much easier. Please create a launch folder under the logs_test directory and create a file called logs_test.launch under it with the following code.

<launch>
    <node pkg = "logs_test" type="logs_test" name="log_demo" output="screen" />
</launch>

Then we can run the following command in shell to launch the node.

roslaunch logs_test logs_test.launch

Since we set the lowest level logger in our code(DEBUG) we’ll see all 5 levels logs are printing. If you change it(e.g. to ERROR) and compile again, you should only see the ERROR and FATAL message.

Edit by: Tony Huang

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