Ignition Launch is used to run and manage plugins and programs. A configuration script can be used to specify which programs and plugins to execute. Alternatively, individual programs and plugins can be run from the command line.
In this tutorial we will explain the configuration scripts in the examples directory.
We can do many things:
- Run multiple executable commands
- Spawn a robot into simulation with plugins
To run a script use
ign launch LAUNCH_FILE_NAME
Launch files
Every script starts with these two tags, which specify the xml version and ignition version.
Multiple executable commands
We can run multiple commands from one file.
Take a look at the gazebo.ign launch file. This script runs the Gazebo server and Gazebo client. We need to just write the command in the command tag.
Spawn a robot into simulation with plugins
Now take a look at the factory.ign launch file. We defined a GazeboFactory plugin under which we included an X2 UGV robot and added the DiffDrive plugin to control the robot. We also added the StatePublisher plugin which publishes the the robot state information.
Launch simulation with plugins in separate processes
The gazebo_plugins.ign launch file loads some plugins and also starts simulation. The joystick plugin will be launched in its own process and will read from a joystick device and output data onto a topic. The JoyToTwist plugin also launches into a separate process and transforms a joystick message to a twist message. Finally, The GazeboServer plugin launches the Gazebo server.
The script can take a world as an argument. To run this script.
ign launch gazebo_plugins.ign [worldName:=<worldName>]
The [worldName] command line argument is optional. If left blank, or not specified, then "diff_drive" is used for the world name.
Example to load the shapes.sdf:
ign launch gazebo_plugins.ign worldName:=shapes
Launch file lookup
There is a lookup process happening if the specified file is not an absolute path. It searches for a file with the given name in paths as follows:
- current directory
- all paths specified in environment variable
IGN_LAUNCH_CONFIG_PATH
- a hardcoded install location (usually
/usr/share/ignition/ignition-launchN/configs/)
The IGN_LAUNCH_CONFIG_PATH environment variable can contain either a single path or a path list (new since 2.2.2). Path list is a colon-separated (on UNIX) or semicolon-separated (on Windows) list of absolute paths.