Iam working on Free BSD 5.3 version. U all know that the output of 'df' command looks as follows:

Filesystem 1K-blocks Used Avail Capacity Mounted on
/dev/ad0s1a 253678 59116 174268 25% /
devfs 1 1 0 100% /dev
/dev/ad0s1e 253678 24280 209104 10% /tmp
/dev/ad0s1f 8913022 2615376 5584606 32% /usr
/dev/ad0s1d 253678 30246 203138 13% /var
devfs 1 1 0 100% /var/named/dev


Now i want to check which partition if greater than 90% full without scanning the first row of record. How to do this ? PLease anyone of u help me with this?