# RLException: neither a launch file package nor a launch file name

To get straight to the point I want to know how to fix this error and understand it, what is an RLException? Why am I getting this? How can I avoid this later? Below I will post what I did step by step:

This is the directory where I have my files

~/Desktop/Research/research_ws


This is the error i'm getting:

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


The following are the codes for dd_robot.urdf and ddrobot_rviz.launch respectively:

<robot name="dd_robot">

<visual>
<origin xyz = "0 0 0" rpy = "0 0 0" />
<geometry>
<box size = ".5 .5 .25"/>
</geometry>
</visual>
</robot>

    <!-- values passed by command line input -->
<arg name = "model" />
<arg name = "gui" default ="False" />

<!-- Set these parameters on Parameter Server -->
<param name = "robot_description"
textfile = "$$(find ros_robotics)/urdf/$$(arg model)" />
<param name = "use_gui" value = "$(arg gui)" /> <!-- Start 3 nodes: joint_state_publisher, robot_state_publisher rviz --> <node name = "joint_state_publisher" pkg = "joint_state_publisher" type = "joint_state_publisher" /> <node name = "robot_state_publisher" pkg = "robot_state_publisher" type = "state_publisher" /> <node name = "rviz" pkg = "rviz" type = "rviz" args = "-d$(find ros_robotics)/urdf.rviz"
required = "true" />
</launch>


I do not yet completely understand what is written in the above codes, I'm following the ROS robotics by example book Fairchild.

source devel/setup.bash

• Yes. Alternatively, you can add that line to your .bashrc file so you don't have to remember to source it in every new terminal.