Build and run a node (absolute beginner)

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Hello everyone,

I am very new into the world of ROS (catkin, sourcing etc.), I had Ubuntu 18.04 installed recently and ROS-Melodic as well.

I am trying to follow and build examples from Ouster here but I can't make Ros Node work so far. I should be able to launch "roslaunch ouster_ros os1.launch replay:=true" but I get this error message:

RLException: [os1.launch] is neither a launch file in package [ouster_ros] nor is [ouster_ros] a launch file name The traceback for the exception was written to the log file

I was told to check what's wrong with roswtf but there was no useful information.

I followed tutorials but it still seems not clear to me how to make everything work. I try to find other tutorials and videos for beginners, but it doesn't help me to understand.

• I am not even sure I built correctly the Sample ROS Node: how can I check a build goes well ?
• Should I always use "catkin_ws", or can I chose to name it "myProject_ws"?

Thank you