How to see message MQTT properties when using mosquitto_sub command

Question

I'm running Mosquitto command mosquitto_sub to subscribe to a topic and see the messages published there.

I would like to be able to see the MQTT properties used when someone publishes a message in that topic.

Is there any way?

Thanks

Have you read the [documentation for `mosquitto_sub`](https://mosquitto.org/man/mosquitto_sub-1.html)? — romkey, Jun 07 '22 at 23:14
Yes, I read it but I didn't understand the -D flag. I want to see all the MQTT properties, not sure why I have to define properties when I'm a subscriber. — italktothewind, Jun 07 '22 at 23:18
I would pay more attention to output format and protocol version. — romkey, Jun 07 '22 at 23:30
This looks like more like a graphic adventure hint rather than a Stack overflow answer. — italktothewind, Jun 08 '22 at 02:20
That would be why it’s a comment. See, you got it! I’m happy to upvote your answer. — romkey, Jun 08 '22 at 05:02

score 1 · Answer 1 · answered Jun 08 '22 at 02:18

You can use the format option (-F) that takes a pattern, for example:

mosquitto_sub -t <topic> -V mqttv5 -F %C

In the example above we are printing the Content type property (%C).

Don't forget the version option (-V) using mqttv5.

You can find more printable properties here: https://mosquitto.org/man/mosquitto_sub-1.html#outputformat (see MQTT related parameters)

1 Answers1