Hi Kartik,

When using <args>, every launch file must be self-contained -- i.e. it
has to declare any args that it uses.   I updated the roslaunch/XML
documentation to make this more explicit.

Thus, test2.launch:

<launch>
   <arg name="name" />
   <param name="param" value="$(arg name)"/>
</launch>

Hope this helps,
Ken

On Fri, Jan 28, 2011 at 9:43 PM, Kartik Mohta <kartikmohta@gmail.com> wrote:
> Hi,
>
> Is there any help on how to properly use the $(arg) substitution in
> launch files? I followed the example given at
> http://www.ros.org/wiki/roslaunch/XML/arg but it gives me a "unused
> args" error.
>
> This is with ROS CTurtle on Ubuntu 10.10.
>
> $ cat test.launch
> <launch>
>    <include file="test2.launch">
>        <arg name="name" value="value"/>
>    </include>
> </launch>
>
> $ cat test2.launch
> <launch>
>    <param name="param" value="$(arg name)"/>
> </launch>
>
> $ roslaunch test.launch
> ...
> Checking log directory for disk usage. This may take awhile.
> Press Ctrl-C to interrupt
> Done checking log file disk usage. Usage is <1GB.
>
> unused args [name] for include of [test2.launch]
>
>
> --
> Kartik
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