I'm stuck on Unit 3 creating a topic_publisher for a counter program

[richard.valenzuela-zavala191]

I think the issue is in my launch command. I followed the unit 2 to create a package called topic_publisher_pkg

[girishkumar.kannan]

Hi @richard.valenzuela-zavala191 ,

Welcome to this Community!

Could you please provide more info on your problem? What is happening? Are you having issues during compilation?

Please post the following as a code-block:

1. Your terminal output (as text) showing the error.
2. Your launch file.
3. Your CMakeLists.txt file

Regards,
Girish

[hugo.ortiz.kataoka]

Good Morning,

I seem to be having the same issue as @richard.valenzuela-zavala191 .

As he seems to not be answering the thread. I will give you my case. If my case happens to be not the same as his, I will move my question to a new topic with no problem.

Alright so following the Exercise 3.1 instructions, I created the following:

• topic_publisher_pkg with deps roscpp and std_msgs

• simple_topic_publisher code in which I copied the example code given.

• Launch file with the following code:
  < launch>
  < !-- topic_pubisher launch file–>
  < node pkg=“topic_publisher” type=“simple_topic_publisher” name=“topic_publisher” output=“screen”>
  < /node>
  < /launch>

• Modified CMakeLists.txt and added:
  add_executable(simple_topic_publisher src/simple_topic_publisher.cpp)
  add_dependencies(simple_topic_publisher ${simple_topic_publisher_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})
  target_link_libraries(simple_topic_publisher
  ${catkin_LIBRARIES}
  )

• The terminal output when launched:
  user:~/catkin_ws$ roslaunch topic_publisher_pkg topic_publisher_launch_file.launch
  … logging to /home/user/.ros/log/a0571150-efcc-11ed-aeda-0242ac160007/roslaunch-2_xterm-7885.log
  Checking log directory for disk usage. This may take a while.
  Press Ctrl-C to interrupt
  Done checking log file disk usage. Usage is <1GB.

started roslaunch server http://2_xterm:41355/

SUMMARY

PARAMETERS

• /rosdistro: noetic
• /rosversion: 1.15.9

NODES
/
topic_publisher (topic_publisher/simple_topic_publisher)

ROS_MASTER_URI=http://2_simulation:11311

ERROR: cannot launch node of type [topic_publisher/simple_topic_publisher]: topic_publisher
ROS path [0]=/opt/ros/noetic/share/ros
ROS path [1]=/home/user/catkin_ws/src
ROS path [2]=/home/simulations/public_sim_ws/src
ROS path [3]=/opt/ros/noetic/share
No processes to monitor
shutting down processing monitor…
… shutting down processing monitor complete

Thank you in advance, greetings.

Hugo

[bayodesegun]

@hugo.ortiz.kataoka

ERROR: cannot launch node of type [topic_publisher/simple_topic_publisher]: topic_publisher

This is the error. It means your C++ source has not been properly built. Were you able to run catkin_make successfully? Try again:

cd ~/catkin_ws
rm -rf build/ devel/
catkin_make
source devel/setup.bash

Ensure the commands above run without any errors.

Then, run the roslaunch command again.

[hugo.ortiz.kataoka]

@bayodesegun

Were you able to run catkin_make successfully?

Yes, I had been able to run catkin_make before.

[100%] Built target simple
[100%] Built target simple_topic_publisher

Either way, I followed your command lines and I got the same output as before.
ERROR: cannot launch node of type [topic_publisher/simple_topic_publisher]: topic_publisher

I have also tried completely removing the package and creating it back again the way I showed above but same thing.

[bayodesegun]

@hugo.ortiz.kataoka

Launch file with the following code:
< launch>
< !-- topic_pubisher launch file–>
< node pkg=“topic_publisher” type=“simple_topic_publisher” name=“topic_publisher” output=“screen”>
< /node>
< /launch>

After examining your package, I found that the name of your package is topic_publisher_pkg, not topic_publisher as you specified in the launch file.

So your launch file should have the pkg tag pkg=“topic_publisher_pkg”.

[hugo.ortiz.kataoka]

It did work!

Thanks a lot @bayodesegun.

Greetings,

Hugo