Don't understand how to parse URDF file

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Hello all,

I am using Ubuntu 12.04 with ROS Indigo.

So I am following the URDF tutorial (Create your own urdf file) but after I create my .urdf file I don't understand how to parse it. The file is located in

/home/<user_name>/ROS/catkin_ws/src/learning_urdf/urdf/robot.urdf

where:

• catkin_ws -- my ROS workspace
• learning_urdf -- a package I created for this tutorial

the code in the robot.urdf is

<robot name="test_robot">
  <link name="link1" />
  <link name="link2" />
  <link name="link3" />
  <link name="link4" />

  <joint name="joint1" type="continuous">
    <parent link="link1"/>
    <child link="link2"/>
  </joint>

  <joint name="joint2" type="continuous">
    <parent link="link1"/>
    <child link="link3"/>
  </joint>

  <joint name="joint3" type="continuous">
    <parent link="link3"/>
    <child link="link4"/>
  </joint>
</robot>

and finally I run the command:

check_urdf robot.urdf

and get this error:

Error:   Error document empty.
         at line 72 in /build/buildd/urdfdom-0.2.10+dfsg/urdf_parser/src/model.cpp
ERROR: Model Parsing the xml failed

Looking more I found this but still not sure what to do. Do I need to run a command similar to this

rosrun xacro xacro.py rospack find pr2_description/robots/pr2.urdf.xacro -o /tmp/pr2.urdf

Do I need to first convert it to a xarco or somthing?

Where does to urdf file need to be for the command to run?