Parse a urdf file

Reading a URDF file

This tutorial starts off where the previous one ended. You should still have your my_urdf.xml file with a description of the robot shown below.

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

  $ roscd sandbox
  $ roscreate-pkg learning_urdf urdf
  $ roscd learning_urdf
  $ rosmake

Now first copy your my_urdf.xml file to the package we just created:

  $ cp /path/to/.../my_urdf.xml .

Create a folder src/ and fire up your editor to create a file called src/parser.cpp:

   1 #include <urdf/model.h>
   2 #include "ros/ros.h"
   3 
   4 int main(int argc, char** argv){
   5   ros::init(argc, argv, "my_parser");
   6   if (argc != 2){
   7     ROS_ERROR("Need a urdf file as argument");
   8     return -1;
   9   }
  10   std::string urdf_file = argv[1];
  11 
  12   urdf::Model model;
  13   if (!model.initFile(urdf_file)){
  14     ROS_ERROR("Failed to parse urdf file");
  15     return -1;
  16   }
  17   ROS_INFO("Successfully parsed urdf file");
  18   return 0;
  19 }

The real action happens in lines 11-12:

  11   urdf::Model model;

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.

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_urdf.xml

The output should look something like this:

  [ INFO] 1254520129.560927000: Successfully parsed urdf file

Now take a look at the code API to see how to start using the URDF model you just created.