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Does anybody know how to pass parameters to a xacro file from a launch file? For example, if I want to run a xacro file five times in my launch file, each time with different parameter, is there any way of achieving that? Your help would be much appreciated.
Tom
I had the same problem and solved it using the script but we found another way now. We use the following code to circumvent using tf_prefix because support has been dropped. I am not sure if this was added in hydro but we just tested the following code and it works. Please test with groovy and reply if it worked.
<param name="robot_description" command="$(find xacro)/xacro.py '$(find my_robot_description)/urdf/my_robot.urdf.xacro' prefix:=$(arg ns)" />
in the xacro file you can simply get the passed argument using $(arg prefix)
Quick question: would you know the syntax to define a "default" value for the prefix argument in xacro? I can't run xacro.py to convert the xacro file to urdf because the argument is not set. Thanks for the tip anyway, it helped a lot!
Oh, I found a workaround, I can pass the argument on the command line, such as: rosrun xacro xacro.py file.xacro > file.urdf prefix:=test
Just to help anybody else who may be having an issue here. You have to define your variable as a xacro:arg instead of a xacro:property. Someone at https://github.com/ros/xacro/issues/176 gave an example that really helped.
I was able to use the argument to evaluate conditional blocks e.g. load_camera:=0
<xacro:if value="$(arg load_camera)">
<... some xml code here ...>
</xacro:if>
AFAIK xacro currently does not support this, but this would be an extremely useful enhancement.
A quick and dirty solution is to use a wrapper around xacro, and change your parameter value using sed. This is a somewhat primitive solution, though you should be able to get the correct functionality through a decently written shell script.
EDIT: Support for this feature was added in ROS Hydro. See @kalectro's answer.
Is there something changed in Kinetic? If I try exactly the answer @kalectro provides, I get an error when launching the launch file: xxx.launch required the 'ns' arg to be set.
Please don't add answers to raise new questions. Also, you will need to setup the arg elsewhere in your launch file. http://wiki.ros.org/roslaunch/XML/arg
Asked: 2012-07-16 07:59:53 -0600
Seen: 15,170 times
Last updated: Feb 15 '18
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