Hi,

you can just follow the one suggested by ghostdog74 and my point here is to use "df -kp" which will let the script use the POSIX output format so that, awk will always take the right field from df o/p.
Otherwise in conditions like when you have lengthy devive names usage of "df -k | awk..... would pickup the wrong feild and so may raise false alarms on your disk space!!

-ilan