Problem in creating .urdf files

edit

Hello everyone. I want to create .urdf file from the file lwa.urdf.xacro. My OS is Ubuntu 14.04 and ROS distribution is indigo.

In the folder: opt/ros/indigo/stacks/schunk_description/urdf/lwa

There are 3 files:

• lwa.gazebo.xacro
• lwa.transmission.xacro
• lwa.urdf.xacro

In terminal, I direct to this directory and command:

ros@ros:~$ rosrun xacro xacro.py lwa.urdf.xacro > lwa.urdf

ros@ros:/opt/ros/indigo/stacks/schunk_modular_robotics/schunk_description/urdf/lwa$ rosrun xacro xacro.py lwa.urdf.xacro > lwa.urdf
bash: lwa.urdf: Permission denied

I know that my question might be somehow silly. I am sorry but it probably refers to my lack of proper knowledge, esp. with Linux. I just guess it must have something to do with permissions. I would appreciate if someone help me or share his/her experience in creating .urdf files with me.

Thanks a lot,

Damon

P.S. Why do I need .urdf file? Gazebo works with .xacro files smoothly and I already can load the robot in gazebo or send the commands to it. The point is that I want to use Moveit! Moveit has an "assistant" which helps you make Moveit recognize your robot. When I load xacro file of PR2 robot in Moveit, the assistant works fine and seemingly creates a .urdf file for itself. But this doesn't work when I load xacro file of schunk. And the reason is that Moveit tries to build .urdf file and fails. This makes me feel if I want moveit work, I should first be able to create .urdf files.

Edit:

First of all, thanks for your time and attention. :) xacro has been introduced to replace urdf. Basically we should be able to create urdf from xacro. My schunk package (schunk_description) is in: opt/ros/indigo/stacks/schunk_modular_robotics

I thought if the problem is permissions, what if I try to make a copy of the package somewhere else and try again. So I copied the package to /Documents. And:

ros@ros:~$ cd Documents

ros@ros:~/Documents$ cd schunk_modular_robotics/schunk_description/urdf/lwa

ros@ros:~/Documents/schunk_modular_robotics/schunk_description/urdf/lwa$ rosrun xacro xacro.py lwa.urdf.xacro > lwa.urdf

This created an empty .urdf file. Here is the contents:

<?xml version="1.0" ?>
<!-- =================================================================================== -->
<!-- |    This document was autogenerated by xacro from lwa.urdf.xacro                 | -->
<!-- |    EDITING THIS FILE BY HAND IS NOT RECOMMENDED                                 | -->
<!-- =================================================================================== -->
<robot xmlns:xacro="http://www.ros.org/wiki/xacro">
</robot>

Moveit used to use .urdf file. But recently, they say the user can also browse to .xacro file as well. I think this is exactly what Moveit tries to do automatically, and probably the urdf file is also created. But since it is empty, Moveit fails. Here is when I try to browse the lwa.urdf.xacro file in Moveit:

An error message shown by setup assistant in a small window: "URDF/COLLADA file is not a valid robot model."

And when I look at the terminal, I see this:

[rospack] Error: no package given
[librospack ...