Embedding a launch file with a parameter

asked 2013-05-16 23:34:48 -0600

markkre
77 ●10 ●10 ●18

updated 2013-11-14 11:33:03 -0600

tfoote

58457 ●128 ●550 ●526 http://www.ros.org/

I have two ros launch files, A.launch and B.launch.

I want B.launch to be included in A.launch like that:

A.launch:

<launch>
    <node name="rosbridge" pkg="rosbridge" type="rosbridge.py" />
    <include file="$(find some_package_name)/launch/B.launch">
    </include>
    ...
</launch>

Works pretty nice. However, it becomes a problem, as soon as there is a parameter necessary in B.launch:

B.launch:

<launch>
    <node name="$(arg START_NODE_NAME)" pkg="some_package_name" type="some_type">
    </node>
</launch>

I tried to use the following tag in A.launch:

<launch>
    <node name="rosbridge" pkg="rosbridge" type="rosbridge.py" />
    <include file="$(find some_package_name)/launch/B.launch">
            <arg name="START_NODE_NAME" value="goal_server" />-->
    </include>
    ...
</launch>

but that didn't work out either.

Is that scenario just not possible?

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answered 2013-05-17 01:19:19 -0600

dornhege

31395 ●134 ●284 ●498

You're on the right track. You only need to define the arg in B.launch, i.e. add

<arg name="START_NODE_NAME" />

to the top of B.launch.

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works, thanks!

markkre ( 2013-05-23 02:06:55 -0600 )edit

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answered 2013-05-17 08:01:00 -0600

Thomas D

4347 ●33 ●65 ●86 http://denewiler.us/cv

The answer from @dornhege will work with no problems.

To go a bit further, I tend to treat launch files like a separate language, where each individual launch file is a function and the <arg> tags at the top of the launch file are the function parameters that have default values. To accomplish that I would put the following line just below the <launch> tag in both launch files:

<arg name="START_NODE_NAME" default="goal_server"/>

There are two benefits to this approach:

In A.launch you can simply have the following line:
```
<include file="$(find some_package_name)/launch/B.launch"/>
```
and you will have B.launch use goal_server as the node name.
You can remap arguments for your launch files when starting A.launch from the command line:
```
roslaunch your_package A.launch START_NODE_NAME:=new_goal_server
```
This is helpful when you want to try changing a few things without necessarily going into the actual files to modify values.

More tips can be found here for using roslaunch with large projects.

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Unfortunately this won't work. You still have to give the arg in 1., when you include B.launch and basically say: <arg name="START_NODE_NAME" value="$(arg START_NODE_NAME)"/>. If you don't, the default will always be used, even if you start as in 2! Changing this behavior is a proposed feature.

dornhege ( 2013-05-17 08:07:21 -0600 )edit

Thanks @dornhege. I thought this works for me, but I'll double-check it now. Do you know of an issue or ticket link for this where the discussion can continue?

Thomas D ( 2013-05-17 08:48:24 -0600 )edit

Proposed in http://www.ros.org/wiki/sig/roslaunch as "bubbling args".

dornhege ( 2013-05-17 09:36:44 -0600 )edit

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