Propagate Value from One Topic to Another in MQTT Broker

#!/data/data/com.termux/files/usr/bin/sh -f

TAB=$(printf '\t')

# The output format specified by the -F option of 'mosquitto_sub'
# needs to match how it is subsequently 'read'.
mosquitto_sub -t 'openScaleSync/measurements/#' -F '%t\t%p\t@s\t%I' \
              -i "Scale Val Sub Client $$" \
| while true; do
    new_payload=$( IFS="$TAB" read -r topic payload time_processed time_processed_readable;
                   (>&2 echo $topic, $payload, $time_processed $time_processed_readable);
               echo "$payload" \
               | jq ". + { \
                           \"time\": ( .date / 1000 ), \
                           \"time_readable\": \
                      ( ( .date / 1000 ) \
                                    | strflocaltime(\"%Y-%m-%dT%H:%M:%S+0900\") \
                                  ), \
                       \"orig_topic\": \"${topic}\", \
                               \"time_processed\": ${time_processed}, \
                               \"time_processed_readable\": \"${time_processed_readable}\" \
                             } \
                         | del(.date)" \
             )
    mosquitto_pub -r -t 'xxxx/scale/weight' -m "$new_payload" \
                  -i "Scale Val Pub Client $$" ;
  done
exit 0