Avoid bash expanding local files in grep arguments

update_ip.sh

@@ -12,7 +12,7 @@ zone=dyn.example.com
 host=desktop
 secret=""
 
-server_ip=$( dig +short ${server} | grep [0-9] | head -1 )
+server_ip=$( dig +short ${server} | grep "[0-9]" | head -1 )
 iface=$( ip route get ${server_ip} | grep -Po '(?<=(dev ))(\S+)' )
 
 # TODO trigger not via cron, but using ip monitor in a while/sleep loop: