topic_tools relay support --filter flag like rostopic echo

[AravindaDP]

I would like to request feature request on either topic_tools relay or relay_field tool to support --filter flag like rostopic echo tool does.

Idea is to forward only a selected subset of tf messages or anything like that on a different topic.

Alternative solutions I tried:

• I tried using topic_tools transform with a ternary operator but it still published an empty message for excluded case.
• rostopic pub with piped echo works but I need this solution to be able to run through a ros launch file.

[dirk-thomas]

Please consider to contribute a pull request for your feature idea.

[AravindaDP]

@dirk-thomas

Thanks for the response. Sure I'll try submitting a PR

In the meantime I realized it's technically possible to wrap a shell script piping rotopic pub and echo for the same effect. But let's keep this opened for some time till either me or someone comes up with a PR as suggested.

[peci1]

Just to save some time of others - here's a bash oneliner that achieves this behavior (although it's not very nice):

rostopic pub /filtered_topic std_msgs/String < <(rostopic echo --filter 'm is not None' /in_topic)