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## note = This tutorial assumes you [[urdf/Tutorials/Create your own urdf file|created your own urdf file]] or use one of the existing PR2 urdf files.
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## title = Parse a urdf file
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## description = This tutorial teaches you how to use the urdf parser
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<<IncludeCSTemplate(TutorialCSHeaderTemplate)>>

<<Buildsystem()>>

<<TableOfContents(4)>>

== Reading a URDF file ==
This tutorial starts off where the [[urdf/Tutorials/Create your own urdf file|previous one]] ended. You should still have your '''my_robot.urdf''' file with a description of the robot shown below.

{{attachment:link.png||height="468px",width="473px"}}

Let's first create a package with a dependency on the urdf parser in our sandbox:

{{{{#!wiki buildsystem rosbuild
{{{
  $ roscd
  $ cd sandbox
  $ roscreate-pkg testbot_description urdf
  $ roscd testbot_description
  $ rosmake
}}}
}}}}
{{{{#!wiki buildsystem catkin
{{{
  $ cd ~/catkin_ws/src
  $ catkin_create_pkg testbot_description urdf
  $ cd testbot_description
}}}
}}}}
Now create a /urdf folder to store the urdf file we just created:

{{{
mkdir urdf
cd urdf
}}}
This follows the convention of always storing your robot's URDF file in a ROS package named '''MYROBOT_description''' and within a subfolder named '''/urdf'''. Other standard subfolders of your robot's description package include '''/meshes''', '''/media''' and '''/cad''', like so:

{{{
/MYROBOT_description
  package.xml
  CMakeLists.txt
  /urdf
  /meshes
  /materials
  /cad
}}}
Next, copy your my_robot.urdf file to the package and folder we just created:

{{{
  $ cp /path/to/.../testbot_description/urdf/my_robot.urdf .
}}}
Create a folder '''src/''' and fire up your editor to create a file called '''src/parser.cpp''':

{{{#!cplusplus block=parser
#include <urdf/model.h>
#include "ros/ros.h"

int main(int argc, char** argv){
  ros::init(argc, argv, "my_parser");
  if (argc != 2){
    ROS_ERROR("Need a urdf file as argument");
    return -1;
  }
  std::string urdf_file = argv[1];

  urdf::Model model;
  if (!model.initFile(urdf_file)){
    ROS_ERROR("Failed to parse urdf file");
    return -1;
  }
  ROS_INFO("Successfully parsed urdf file");
  return 0;
}
}}}
The real action happens in lines 12-13. Here we create a parser object, and initialize it from a file by providing the filename. The ''initFile'' method returns true if the URDF file was parsed successfully.

{{{{#!wiki buildsystem rosbuild
Now let's try to run this code. First add the following line to your CMakeList.txt file:
{{{
  rosbuild_add_executable(parser src/parser.cpp)
}}}
build your package, and run it.
{{{
$ make
$ ./bin/parser my_robot.urdf
}}}
}}}}
{{{{#!wiki buildsystem catkin
Now let's try to run this code. First add the following lines to your CMakeList.txt file:
{{{
 add_executable(parser src/parser.cpp)
 target_link_libraries(parser ${catkin_LIBRARIES})
}}}
build your package, and run it.

{{{
$ cd ~/catkin_ws   
$ catkin_make
$ .<path>/parser <path>my_robot.urdf
# Example: ./devel/lib/testbot_description/parser ./src/testbot_description/urdf/my_robot.urdf
}}}
}}}}
The output should look something like this:

{{{
  [ INFO] 1254520129.560927000: Successfully parsed urdf file
}}}
Now take a look at the [[http://www.ros.org/doc/api/urdf/html/|code API]] to see how to start using the URDF model you just created. A good example of the URDF model class in action is `Robot::load()` in [[https://github.com/ros-visualization/rviz/|RViz]], in the file `src/rviz/robot/robot.cpp`.

Note: code is in https://github.com/ros/urdfdom_headers repository, reference it for Code API.

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