Does rostopic echo no longer work for arrays?

asked 2013-08-14 11:15:11 -0600

mattadc
3 ●1 ●1 ●4

updated 2013-08-14 11:19:42 -0600

Recently switched to groovy and rostopic doesn't seem to be able to handle arrays anymore. Does anyone know why?

Example for me, from a simple topic with a list of doubles: rostopic echo /robot/joint_states/position[1]

Results in:

Traceback (most recent call last):   File "/opt/ros/groovy/bin/rostopic", line 35, in <module>
    rostopic.rostopicmain()   File "/opt/ros/groovy/lib/python2.7/dist-packages/rostopic/__init__.py", line 1666, in rostopicmain
    _rostopic_cmd_echo(argv)   File "/opt/ros/groovy/lib/python2.7/dist-packages/rostopic/__init__.py", line 1026, in _rostopic_cmd_echo
    _rostopic_echo(topic, callback_echo, bag_file=options.bag)   File "/opt/ros/groovy/lib/python2.7/dist-packages/rostopic/__init__.py", line 692, in _rostopic_echo
    index = submsg_class.__slots__.index(field) ValueError: 'position[1]' is not in list`

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Are you sure that that topic is correct? Can you update this question with the results of rostopic info /robot/joint_states ?

SL Remy ( 2013-08-15 06:44:58 -0600 )edit

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answered 2013-08-15 12:01:44 -0600

Dirk Thomas
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updated 2013-08-15 12:12:16 -0600

It looks like a regression of https://github.com/ros/ros_comm/issues/242

It is fixed in https://github.com/ros/ros_comm/commit/2af3d693645f084086ef0a5c50f9b666ea0fc1fd and will be available with the next ros_comm release (1.9.48).

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Yes, this fixed the problem. Thank!

mattadc ( 2013-08-16 05:17:54 -0600 )edit

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answered 2013-08-15 08:15:39 -0600

mattadc
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updated 2013-08-15 08:17:50 -0600

My topic is correct. It's a standard sensor_msgs/JointState message type, so it does have a field position that's a float64 array.

Output of rostopic info is:

Type: sensor_msgs/JointState

Publishers: * /realtime_loop (http://p1307010:33103/)

I tried the echo of ...position/data[1] and also get an error, but a different one:

Traceback (most recent call last): ...snip...
File "/opt/ros/groovy/lib/python2.7/dist-packages/genpy/message.py", line 532, in _get_message_or_service_class raise ValueError("message type is missing package name: %s"%str(message_type)) ValueError: message type is missing package name: float64[]

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answered 2013-08-15 06:49:03 -0600

SL Remy
2022 ●26 ●49 ●67

This seems as if you expect an array of positions, but according to the the wiki, the array value is in data object .. something like rostopic echo /robot/joint_states/position/data[1] should work (assuming that the namespace is correct.. and that you really expected an array of joint states to be published.. then there's another issue)

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Does rostopic echo no longer work for arrays?

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