xacro generates empty `ur5.urdf` file from `ur5.urdf.xacro`

[kevin-thankyou-lin]

Hi!

I cloned the melodic-devel branch and followed the steps for building from source:

# retrieve the sources (replace '$ROS_DISTRO' with the ROS version you are using)
git clone -b $ROS_DISTRO-devel https://github.com/ros-industrial/universal_robot.git

cd $HOME/catkin_ws

# checking dependencies (again: replace '$ROS_DISTRO' with the ROS version you are using)
rosdep update
rosdep install --rosdistro $ROS_DISTRO --ignore-src --from-paths src

# building
catkin_make

# activate this workspace
source $HOME/catkin_ws/devel/setup.bash

However, when I run xacro on ur5.urdf.xacro, I get an empty file:

(igibson) thankyou-always@thankyou:~/code/catkin_ws/src/universal_robot/ur_description/urdf$ rosrun xacro xacro -o ur5.urdf ur5.urdf.xacro 

(igibson) thankyou-always@thankyou:~/code/catkin_ws/src/universal_robot/ur_description/urdf$ cat ur5.urdf 
<?xml version="1.0" encoding="utf-8"?>
<!-- =================================================================================== -->
<!-- |    This document was autogenerated by xacro from ur5.urdf.xacro                 | -->
<!-- |    EDITING THIS FILE BY HAND IS NOT RECOMMENDED                                 | -->
<!-- =================================================================================== -->
<robot>
</robot>

Would you know what the issue is?

[kevin-thankyou-lin]

Whoops, I'm supposed to use ur5_robot.urdf.xacro.