ASM Disk Group script

I need assistance with a script I can run as a cronjob that will send me the space of my ASM Disk groups (Total, free and used). I have the coding on how to send to my email but Im looking for details of whats inside script as to how to connect to sqlplus / as sysdba and execute sql query.
Any of you have a script in place that sends you your disk group info periodically so you know how much space is used?

Thanks