There is a tool for creating ROS Packages (roscreate-pkg), but, as you will see, there is nothing actually difficult here. roscreate-pkg prevents mistakes and saves effort, but packages are just a directory and a simple XML file.

Now we'll create a new foobar package. This tutorial assumes that we're working in the directory pkgs on your ROS_PACKAGE_PATH.

pkgs$ mkdir foobar
pkgs$ cd foobar

The very first thing we'll do is add our manifest file. The manifest.xml file allows tools like rospack to determine information about what your package depends upon.

Inside of foobar/manifest.xml put the following:

<package>
  <description brief="example package tutorial">A simple tutorial package</description>
  <author>Your Name Here</author>
  <license>BSD</license>
  <depend package="roscpp" />
  <depend package="std_msgs" />
</package>

Now that your package has a manifest, ROS can find it. Try executing the command:

rospack find foobar

If ROS is set up correctly you should see something like: /home/user/ros/pkgs/foobar. This is how ROS finds packages behind the scenes.

Note that this package now also has dependencies on roscpp and std_msgs. To see one example of why specifying these dependencies is useful, try executing the following commands rospack commands:

rospack export --lang=cpp --attrib=cflags foobar
rospack export --lang=cpp --attrib=lflags foobar

When you run these, rospack looks up the dependencies of foobar and generates the necessary list of includes or linking statements to compile and link the executable. These commands are used by the ROS build system to correctly compile and link your packages despite the modular nature of ROS. You'll probably never have to use these directly since our build system takes care of it for you. However, as you can see, they are reasonably easy use if you want to use a different build system.

In order to take advantage of this, we need to make two build files: a Makefile and CMakeLists.txt file.

Inside of foobar/Makefile, put:

include $(shell rospack find mk)/cmake.mk

This tells make that we're going to use CMake instead of Make to build this package.

Now we need the CMakeLists.txt file so that we can use CMake instead. ROS uses CMake for its more powerful flexibility when building across multiple platforms.

In foobar/CMakeLists.txt put:

cmake_minimum_required(VERSION 2.4.6)
include($ENV{ROS_ROOT}/core/rosbuild/rosbuild.cmake)
rosbuild_init()

That's all you need to start building a package in ROS. Of course, if you want it to actually start building something, you're going to need to learn a couple more CMake macros. See our CMakeLists guide for more information.