The roslaunch package comes with roslaunch tool as well as several support tools to assist in the process of launching ROS Nodes.

roslaunch

roslaunch is an important tool that manages the start and stop of ROS nodes. It takes one or more .launch files as arguments.

Launch syntax

Most roslaunch commands require the name of a launch file. You can either specify the file path of the launch file, or you can specify a package name and launch file in that package, e.g.

• $ roslaunch roslaunch example.launch

  or

  $ roscd roslaunch
  $ roslaunch example.launch

roslaunch <package-name> <launch-filename> [args]

• Launch <launch-filename> located in <package-name>, e.g.:

  $ roslaunch rospy_tutorials talker_listener.launch

  roslaunch will find a file with the matching name inside the specified package and run it.

roslaunch <launch-file-paths...> [args]

• Launch the file(s) specified by relative or absolute paths, e.g.

  $ roslaunch pr2_robot/pr2_bringup/pr2.launch

roslaunch - [args] New in Indigo

• Launch the roslaunch XML passed as standard input, e.g.

  $ rosrun package generate_launch | roslaunch -

-p port

• If you launched roscore on a different port using the -p option, you need to pass in the -p flag to roslaunch as well, e.g.

  $ roslaunch -p 1234 package filename.launch

  This will dynamically override the port setting in your ROS_MASTER_URI.

--wait

• Delay the launch until a roscore is detected.

--local

• Launch of the local nodes only. Nodes on remote machines will not be run.

--screen

• Force all node output to screen. Useful for node debugging.

--log New in Melodic

• Force all node output to log file. Also useful for node debugging.

-v

• Enable verbose printing. Useful for tracing roslaunch file parsing.

--dump-params

• Print parameters in launch file in YAML format.

Passing in args

If the file you are launching specifies args that require setting, you can do so using an identical syntax to ROS remapping arguments, e.g.:

roslaunch my_file.launch arg:=value

Non-launch options

The following options provide information about a launch file without actually doing a launch. These options use the same launch-file resolution as the regular roslaunch command. You can either specify the file path of the launch file, or you can specify a package name and launch file in that package, e.g. for the example.launch file in the roslaunch package, you can use:

• roslaunch --nodes roslaunch $ROS_ROOT/tools/roslaunch/example.launch

  or

  roslaunch --nodes roslaunch example.launch

--nodes <package-name> <launch-file>
--nodes <launch-file>

• List nodes by 'name' that are in <launch-file>. This is useful for figuring out the node name to pass to --args.

--args <node-name> <package-name> <launch-file>
--args <node-name> <launch-file>

• Display the command-line arguments that roslaunch uses when launching the node in <launch-file> named <node-name>. This is handy if you just want to launch that particular node for debugging, e.g.

  $ roslaunch --args my_node file.launch | bash

  You can also use this option with substitution args (for bash, you have to be careful to use single-quotes instead of double-quotes):

  $ roslaunch --args '$(anon my_node)' file.launch

--find <node-name> <package-name> <launch-file>
--find <node-name> <launch-file>

• Print name of launch file that the node named <node-name> is defined in. Launch files often have many includes, which can make it difficult to find where an actual <node> definition resides. For example:

  $ roslaunch --find /included/talker roslaunch example.launch

--files <filename>

• Print all files included in processing <filename>, including the file itself. This is useful for passing to other command line tools, e.g.

  $ roslaunch --files foo.launch | xargs grep stuff

--ros-args

• Display command-line arguments for this launch file

  <launch>
    <!-- ros_args.launch -->
    <arg name="foo" default="true" doc="I pity the foo'."/>
    <arg name="bar" doc="Someone walks into this."/>
    <arg name="baz" default="false"/>
    <arg name="nop"/>
    <arg name="fix" value="true"/>
  </launch>
  
  $> roslaunch --ros-args ros_args.launch
  Required Arguments:
    bar: Someone walks into this.
    nop: undocumented
  Optional Arguments:
    baz (default "false"): undocumented
    foo (default "true"): I pity the foo'.

Internal-use only options

roslaunch uses several command-line options that are for internal use only, including -c, -u, and --core.

Environment Variables (advanced users)

NOTE: this section is intended for advanced users only

• ROSLAUNCH_SSH_UNKNOWN

  • When launching on remote machines, SSH requires that the remote machine's key be stored in the local known_hosts file. You can set roslaunch to ignore this constraint and allow connections to machines for which you don't have keys established. This is a dangerous option as it introduces a security hole and should only be used if you understand the consequences.

roslaunch-deps

roslaunch-deps reports which ROS Packages a .launch file depends on. It can also track down command build problems, such as missing dependencies in package manifests or syntax errors.

Usage

To get warnings about dependencies missing in manifest files, run with the -w warn option:

$ roslaunch-deps -w file.launch

To get more verbose output to help track where a dependency is coming from, run with the -v verbose option:

$ roslaunch-deps -v file.launch

roslaunch-check

roslaunch-check is a command-line version of launch file checking. You can run by the follwoing:

$ rosrun roslaunch roslaunch-check launch            (passing a directory)
$ rosrun roslaunch roslaunch-check test/launch       (passing a sub directory)
$ rosrun roslaunch roslaunch-check launch/aa.launch  (passing a file)

roslaunch-logs

Roslaunch stores log files for a particular run together in a subdirectory of the ROS log directory ($ROS_ROOT/log or $ROS_LOG_DIR). In general, logs files are stored in ROS_LOG_DIR/run_id, where run_id is a unique ID associated with a particular run of a roscore.

Example:

# roslaunch-logs                                                                                               
/root/.ros/log/eef4c2b6-2c3f-11ea-96bb-0242ac110003

Usage

roslaunch-logs is meant to be used together with the 'cd' command, e.g.

cd `roslaunch-logs`
root@ea57f5de462a:~/.ros/log/eef4c2b6-2c3f-11ea-96bb-0242ac110003# 

You can type this command to quickly go to the directory with the log files for your nodes.