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I have a topic containing several messages. How can I use 'rostopic echo' to echo only one message.

For example this is my topic containing the following messages:

Header      hdr
int32       runlevel
int32       sublevel
int32       last_seq
int32[2]    type
int32[6]    pos
float32[18]   ori

and I am just interested to see only message pos on my terminal.


Originally posted by Hossein on ROS Answers with karma: 45 on 2016-02-04

Post score: 1


Original comments

Comment by Hossein on 2016-02-04:
Is there anyway to decrease the rate of publishing? It's too fast and I can't see them.

Also is there anyway to plot them?

Comment by MichaelKorn on 2016-02-04:
please update your question, don't post an answer.

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1 Answer 1

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Regarding to the documentation of rostopic, this should work:

rostopic echo /my_topic/field_name

one complex example for typical tf messages:

rostopic echo /tf/transforms[0]/transform/translation/x

You can change the output rate (e.g. 1sec) with:

watch -n1 rostopic echo /my_topic/field_name

You can plot topics with rqt_plot


Originally posted by MichaelKorn with karma: 1480 on 2016-02-04

This answer was ACCEPTED on the original site

Post score: 11


Original comments

Comment by ahendrix on 2016-02-04:
I can confirm that the first version works. I use it frequently.

Comment by MichaelKorn on 2016-02-04:
@ahendrix: You are right. I tried it with tf and I failed to take into account that the field "transforms" is an array.

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