How to write a function in ROS2 ?

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Is it possible in ROS to multiply a Time with float and store it in a float and publish that ? something like : std_msgs::Float32 msg; msg.data = 2*ros::Time::now() If not, then just publish the time topic_publisher(ros::Time::now(). I tried both but unable to build.

Currently the time class is pretty primitive. The only thing you can get is integer nanoseconds, see: http://docs.ros2.org/ardent/api/rclcp... I'd recommend something like this for now: msg.data = (2 * ros::Time::now()).nanoseconds() / 1e9;

Or msg.data = (ros::Time::now().nanoseconds() / 1e9) * 2; depending on how you want to handle overflow and loss of precision.

@☻William Thanks for the suggestion but somehow i want the time stamp being displayed at the console. Something like : Publishing at 09:00:01 and i guess this will only give me a float or an integer value. Do you think using std_msgs::Time would be the right approach ?

@William Basically I want the wall clock time as the ouptut (with or without being multiplied by a factor)

I'd recommend using std::chrono 's date utilities to format it: http://en.cppreference.com/w/cpp/chrono or just divide the nanoseconds by 1e9.

You already suggested division by 1e9 in your previous comment. But that would also yield a floating value and not the timeclock.

As I said, if you want something nicer than floating point seconds, then you can use the standard library to get pretty printed times. The ROS message version of time, i.e. builtin_msgs::msg::Time, will not help you print it nicer.