ROS software is organized into packages, each of which contains some combination of code, data, and documentation. Usually there is a package for each 'function' of your robot. For example, you can have a package for navigation or for sensor capturing. Thanks to the contributing community, there are many pre built packages available to download for free.

Let's create our first package!

• Creating a packages

cd ~/catkin_ws/src
catkin_create_pkg my_awesome_code rospy

This creates a new package named my_awesome_code. Inside that folder we'll find a /src directory where we will put our python code.

The roscore command is a service that provides connection information to nodes so that they can transmit messages to one another. It is necessary to run this command before launching any package.

To run a package, we use the rosrun command executed like this:

rosrun PACKAGE EXECUTABLE [ARGS]

PACKAGE is the name of the created package, for example my_awesome_code, and EXECUTABLE is the name of the python file containing the code. Attention! The python file needs to be executable, juste use sudo chmod +x file.py