Marcel is a very lightweight daemon to publish data to an MQTT message bus. It can also subscript to topics to check for data validity / outages, sending alerts and trigger custom Lua scripts.

It was primarily made for smart housing but can be obviously used with any MQTT driven data.

Installation procedures and some reference information are provided on its GitHub : those pages aim to provide comprehensive information on Marcel's configuration as well as some usage cases.

Marcel understands following arguments to its command line.

Marcel (6.0502)
Publish Smart Home figures to an MQTT broker
Known options are :
        -h : this online help
        -v : enable verbose messages
        -f<file> : read <file> for configuration
                (default is '/usr/local/etc/Marcel.conf')
        -t : test configuration file and exit

-t is the most important one as it safely check your updated configuration file without interfering with an already running instance. It implies verbose output.