ROS File Types

Given is a description of many of the ROS file types that you may encounter.

ROS Launch File

Roslaunch is used to start a group of nodes with specific topics and parameters. RosLaunch first checks for a roscore also known as the ros master and checks to see if it is running. Roslaunch will start roscore if one is not found. Then the Launch file runs all of the nodes within the launch file.

roslaunch <package name> <launch file>

Syntax

XML Format:

<launch>
   <node pkg="package_name" type="executable_name" name="desired_node_name">
       <param name="param1 name" type="param1 type" value="param1 value" />
       <param name="param2 name" type="param2 type" value="param2 value" />
       <remap from="original topic name" to="new topic name" />
   </node>
</launch>

Remapping a topic in a launch file

<node pkg="package_name" type="executable_name" name="desired_node_name">

   <remap from="original topic name" to="new topic name" />

</node>

Change default Parameter in a launch file

<node pkg="package_name" type="executable_name" name="desired_node_name">
   <param name="param1 name" type="param1 type" value="param1 value" />
   <param name="param2 name" type="param2 type" value="param2 value" />
</node>

ROS URDF File

A ROS URDF File is used to define models. Models can be a robot, or objects, and even scenery. URDF files are complex and we recommend the ros urdf tutorials

ROS .bag file

A RosBag file is a file used to record and playback any data within ROS. This allows you to play back a scenario and try new algorithms without having to rerun the entire scenario. It also helps you figure out what happens when your program does fail by playing back the exact data that caused it.

ROS .msg File

ROS Messages use a simplified messages description language for describing the data fields (aka messages) that ROS nodes publish. If you cannot find a message type that meets your need you can create a custom message to meet your needs.

ROS .srv Files

ROS srv files are used to setup a service.

ROS Parameter Files

ROS parameter files are .yaml files used to define program parameters.