ROS packages and manifest

Each package contains a manifest named package.xml that describes the package in the Extensible Markup Language (XML) format. In addition to providing a minimal specification describing the package, the manifest defines properties about the package such as the package name, version numbers, authors, maintainers, and any dependencies on other packages.

Occasionally, we would like to find packages that we wish to use and display the files involved. This section introduces several useful ROS commands:

The rospack command can be used to list ROS packages, locate packages by name, and determine if a package depends on another package, among other uses. For more information use the following command with the help or -h option in the form:

$ rospack help | less

We will use the turtlesim package for the examples here. To change directories to the location of turtlesim, use the following command:

$ roscd turtlesim

This changes the location on one of the author's workstations as follows:

linux@D158-45929:/opt/ros/kinetic/share/turtlesim$

On your computer, the $ command prompt will be preceded by the information about your computer. Generally, that information for our computers will be deleted in our examples using ROS commands. Once you are in the turtlesim directory, the standard Linux commands can be used with the subdirectories or files, or the ROS commands can be used. To determine the directories and files in the turtlesim directory but without changing to the turtlesim directory, use the following command:

$ rosls turtlesim

Here is the result from the home directory of the author's workstation with ROS installed:

cmake images  msg package.xml srv

To see the filenames of the images loaded with turtlesim, specify the images directory in the package as follows:

$ rosls turtlesim/images

The output of the preceding command is as follows:

box-turtle.png   groovy.png  indigo.svg   palette.png
diamondback.png  hydro.png   jade.png     robot-turtle.png
electric.png     hydro.svg   kinetic.png  sea-turtle.png
fuerte.png       indigo.png  kinetic.svg  turtle.png

There are various turtle images that can be used. The rosls turtlesim command will also work to show the contents of the turtlesim subdirectories: /msg for messages and /srv for services. These files will be discussed later. To see the manifest, type the following commands:

$ roscd turtlesim
$ cat package.xml

This will also show the dependencies, such as roscpp for C++ programs.

$ rospack find turtlesim

$ rospack list

$ rospack list | less

$ rospack list-names

$ rospack list-names | grep turtle