# Set deleteUnattachedNics=1 if you want to delete unattached NICs
# Set deleteUnattachedNics=0 if you want to see the Id(s) of the unattached NICs
deleteUnattachedNics=0

unattachedNicsIds=$(az network nic list --query '[?virtualMachine==`null`].[id]' -o tsv)
for id in ${unattachedNicsIds[@]}
do
   if (( $deleteUnattachedNics == 1 ))
   then

       echo "Deleting unattached NIC with Id: "$id
       az network nic delete --ids $id
       echo "Deleted unattached NIC with Id: "$id
   else
       echo $id
   fi
done