Set Roon ZoneID on a bridge device

set_zone_id.sh

#!/bin/bash

# Endian changed the endiness of the arg
endian()
{
        v=$1 
        i=${#v}

        while [ $i -gt 0 ]
        do
                i=$[$i-2]
                endianResult=$endianResult${v:$i:2}
        done
}

# Script makes the assumption that there is only one output enabled on the Bridge. On this basis
# the script gets the last device file to be created, which will contain the unique_id of the output.
# The unique_id is used to create the zone_id
deviceFile=$(ls -Art /var/roon/RAATServer/Settings/device_*.json | tail -n 1)
echo "File Name: $deviceFile"

# The field unique_id is extracted from the device file.
# this take the form of 21d58030-868d-1363-89e4-23ada731ca6c
uniqueID=$(cat $deviceFile | jq '.unique_id')
echo "UniqueID: $uniqueID"

endian ${uniqueID:1:8}
endian ${uniqueID:10:+4}
endian ${uniqueID:15:+4}

segment4=${uniqueID:20:+4}
segment5=${uniqueID:25:+12}

# zone_id starts with 1601, then the unique_id from above. The first three segments are encoded 
# in big endian instead of little. There are also no hyphens
# Using the example above the zone_id would be:
# 16013080d5218d86631389e423ada731ca6c
zoneID="1601$endianResult$segment4$segment5"

echo "ZoneID: $zoneID"
echo  zoneID=$zoneID >> /etc/roonBridge.conf