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Managing Dependencies with rosdep
Goal: Manage external dependencies using
Tutorial level: Intermediate
Time: 5 minutes
Author: Steve Macenski
This tutorial will explain how to manage external dependencies using
What is rosdep?
rosdep is ROS’s dependency management utility that can work with ROS packages and external libraries.
rosdep is a command-line utility for identifying and installing dependencies to build or install a package.
It can be or is invoked when:
Building a workspace and needing appropriate dependencies to build the packages within
Install packages (e.g.
sudo apt install ros-galactic-demo-nodes-cpp) to check the dependencies needed for it to execute
It has the ability to work over a single package or over a directory of packages (e.g. workspace).
A little about package.xml files
package.xml file contains a set of dependencies.
The dependencies in this file are generally referred to as “rosdep keys”.
These are represented in the tags
They specify in what situation each of the dependencies are required in.
For dependencies only used in testing the code (e.g.
For dependencies only used in building the code, use
For dependencies needed by headers the code exports, use
For dependencies only used when running the code, use
For mixed purposes, use
depend, which covers build, export, and execution time dependencies.
These dependencies are manually populated in the
package.xml file by the package’s creators and should be an exhaustive list of any non-builtin libraries and packages it requires.
How does rosdep work?
rosdep will check for
package.xml files in its path or for a specific package and find the rosdep keys stored within.
These keys are then cross-referenced against a central index to find the appropriate ROS package or software library in various package managers.
Finally, once the packages are found, they are installed and ready to go!
The central index is known as
rosdistro, which may be found here.
We’ll explore that more in the next section.
How do I know what keys to put in my package.xml?
Great question, I’m glad you asked!
For ROS packages (e.g.
nav2_bt_navigator), you may simply place the name of the package.
You can find a list of all released ROS packages in
<distro>/distribution.yaml for your given ROS distribution.
For non-ROS package system dependencies, we will need to find the keys for a particular library.
In general, there are two files of interest:
base.yaml in general contains the
apt system dependencies.
python.yaml in general contains the
pip python dependencies.
To find a key, search for your library in this file (preferably ctrl+F, its long) and find the name in
yaml that contains it.
This is the key to put in a
For example, imagine a package had a dependency on
doxygen because it is a great piece of software that cares about quality documentation (hint hint).
We would search
doxygen and come across:
doxygen: arch: [doxygen] debian: [doxygen] fedora: [doxygen] freebsd: [doxygen] gentoo: [app-doc/doxygen] macports: [doxygen] nixos: [doxygen] openembedded: [doxygen@meta-oe] opensuse: [doxygen] rhel: [doxygen] ubuntu: [doxygen]
That means our rosdep key is
doxygen, which would resolve to those various names in different operating system’s package managers for installation.
What if my library isn’t in rosdistro?
If your library isn’t in
rosdistro, you can experience the greatness that is open-source software development: you can add it yourself!
Pull requests for rosdistro are typically merged well within a week.
Detailed instructions may be found here for how to contribute new rosdep keys. If for some reason these may not be contributed openly, it is possible to fork rosdistro and maintain a alternate index for use.
How do I use the rosdep tool?
Now that we have some understanding of
rosdistro, we’re ready to use the utility itself!
Firstly, if this is the first time using
rosdep, it must be initialized via:
sudo rosdep init rosdep update
This will initialize rosdep and
update will update the locally cached rosdistro index.
It is a good idea to
update rosdep on occasion to get the latest index.
Finally, we can run
rosdep install to install dependencies.
Typically, this is run over a workspace with many packages in a single call to install all dependencies.
A call for that would appear as the following, if in the root of the workspace with directory
src containing source code.
rosdep install --from-paths src -y --ignore-src
Breaking that down:
--from-paths srcspecifies the path to check for
package.xmlfiles to resolve keys for
-ymeans to default yes to all prompts from the package manager to install without prompts
--ignore-srcmeans to ignore installing dependencies, even if a rosdep key exists, if the package itself is also in the workspace.
There are additional arguments and options available.
rosdep -h to see them.