Embedded Motion Control/Tutorials/Creating a ROS package
Description: This tutorial covers using roscreate-pkg or catkin to create a new package, and rospack to list package dependencies.
Before we create a package, let's see how the roscreate-pkg command-line tool works. This creates a new ROS package. All ROS packages consist of the many similar files : manifests, CMakeLists.txt, mainpage.dox, and Makefiles. roscreate-pkg eliminates many tedious tasks of creating a new package by hand, and eliminates common errors caused by hand-typing build files and manifests.
To create a new package in the current directory:
You can also specify dependencies of that package:
roscreate-pkg [package_name] [depend1] [depend2] [depend3]
Creating a New ROS Package
Now we're going to go into your home or project directory and create our beginner_tutorials package. We are going to make it depend on std_msgs, roscpp, and rospy, which are common ROS packages.
Now go your EMC group directory:
We can now use roscreate-pkg to create our first ROS package. However, there is a small problem: every package in ROS must have a unique name. This means if you and your group members all use the same package name and share these packages using the SVN, ROS won't know which of the packages to use. Therefore, create a package with a unique name:
roscreate-pkg beginner_tutorials_<YOUR_NAME> std_msgs rospy roscpp
You will see something similar to:
Created package directory /home/sdries/ros/emc/emc01/beginner_tutorials_sjoerd Created include directory /home/sdries/ros/emc/emc01/beginner_tutorials_sjoerd/include/beginner_tutorials_sjoerd Created cpp source directory /home/sdries/ros/emc/emc01/beginner_tutorials_sjoerd/src Created package file /home/sdries/ros/emc/emc01/beginner_tutorials_sjoerd/Makefile Created package file /home/sdries/ros/emc/emc01/beginner_tutorials_sjoerd/manifest.xml Created package file /home/sdries/ros/emc/emc01/beginner_tutorials_sjoerd/CMakeLists.txt Created package file /home/sdries/ros/emc/emc01/beginner_tutorials_sjoerd/mainpage.dox Please edit beginner_tutorials_sjoerd/manifest.xml and mainpage.dox to finish creating your package
You're going to want to spend some time looking at the manifest.xml file in your newly created package. Manifests play an important role in ROS as they define how packages are built, run, and documented.
Now lets make sure that ROS can find your new package. It is often useful to call rospack profile after making changes to your path so that new directories will be indexed:
rospack profile rospack find beginner_tutorials_<YOUR_NAME>
Should result in:
If this fails, it means ROS can't find your new package, which may be an issue with your ROS_PACKAGE_PATH. Make sure you correctly followed the steps in this previous tutorial .
Try moving to the directory for the package.
roscd beginner_tutorials_<YOUR_NAME> pwd
First-order package dependencies
When using roscreate-pkg earlier, a few package dependencies were provided. These first-order dependencies can now be reviewed with the rospack tool.
rospack depends1 beginner_tutorials_<YOUR_NAME>
std_msgs rospy roscpp
As you can see, rospack lists the same dependencies that were used as arguments when running roscreate-pkg. These dependencies for a package are stored in the manifest file. Take a look at the manifest file.
roscd beginner_tutorials<YOUR_NAME> cat manifest.xml
<package> ... <depend package="std_msgs"/> <depend package="rospy"/> <depend package="roscpp"/> </package>
Indirect package dependencies
In many cases, a dependency will also have its own dependencies. For instance, rospy has other dependencies.
rospack depends1 rospy
A package can have quite a few indirect dependencies. Luckily rospack can recursively determine all nested dependencies.
rospack depends beginner_tutorials_<YOUR_NAME>
cpp_common rostime roscpp_traits roscpp_serialization genmsg genpy message_runtime std_msgs rosgraph rosgraph_msgs catkin rospack roslib rospy rosconsole xmlrpcpp roscpp
ROS Client Libraries
You may be wondering what rospy and roscpp dependencies are from the previous examples. rospy and roscpp are Client Libraries. The client libraries allow different programming languages to communicate through ROS. rospy is the client library for Python. roscpp is the client library for C++.
Lets just list some of the commands we've used so far:
roscreate-pkg = ros+create-pkg : generates all the files needed to create a ROS package rospack = ros+pack(age) : provides information related to ROS packages rosstack = ros+stack : provides information related to ROS stacks
Now that you've made a new ROS package, let's see how we can use an SVN to share it among different systems with version history.