View source for Embedded Motion Control/Tutorials/Finalizing your ROS setup

In the previous tutorial you created the directory ''~/ros/emc'' and used SVN to check out all software needed for this project. Now it is time to finalize the ROS set-up.

ROS uses a set of ''environment variables'' to keep track of where ROS packages are located, which ROS versions is used, etc. Think of an environment variable as a variable containing some information that is needed throughout your terminal session. Those environment variables are typically set when ''.bashrc'' is sourced, as was explained in a previous tutorial.

One important ROS environment variable is your '''ROS_PACKAGE_PATH'''. This contains the paths ROS will inspect while looking for a package or stack (''e.g.'' when you use ''roscd''), separated by colons. To check your ROS package path, type the following in a terminal:

<pre>echo $ROS_PACKAGE_PATH</pre>

It will return:

:<pre>/opt/ros/groovy/share:/opt/ros/groovy/stacks</pre>

Which means currently two directories are used by ROS: ''/opt/ros/groovy/share'' and ''/opt/ros/groovy/stacks''. This means the packages that were checked out into ''~/ros/emc'' cannot be found by ROS. Fortunately, we can change this. Open '''~/.bashrc''' in an editor, for example using:

<pre>gedit ~/.bashrc</pre>

Now add the following line:

<pre>export ROS_PACKAGE_PATH=~/emc/ros:$ROS_PACKAGE_PATH</pre>

When this statement is executed, the text ''$ROS_PACKAGE_PATH'' is replaced by the actual value of this variable (we used this above to check the content using the ''echo'' command). This means that the variable is ''pre-pended'' by ''~/emc/ros'' when this statement is executed.

Source the '''.bashrc'' file (using ''source ~/.basrc'') or start a new terminal. Now again check the content of the ''$ROS_PACKAGE_PATH'' variable:

<pre>echo $ROS_PACKAGE_PATH</pre>

The result should be:

:<pre>/home/YOUR_NAME/emc/ros:/opt/ros/groovy/share:/opt/ros/groovy/stacks</pre>

Now, ''~/emc/ros'' will also be checked by ROS when looking for packages. Try it:

<pre>roscd pico_example</pre>

Should navigate you to the ''pico_example'' package. The [[ Embedded Motion Control/Tutorials/Navigating the ROS filesystem | next tutorial ]] will explain in more detail what this ''roscd'' command does.