Send alert for 80% threshold comparing two values from Disk partition

Need send a alert comparing two values of disk space for all partition It should check for SIZE and USED values and compare values makesure not more than 80%

Filesystem             Size   Used  Avail  Mounted
/dev/sda1              9,9G   3,3G   6,1G  /
none                    17G   213k    17G  /dev
none                    17G      0    17G  /dev/shm
none                    17G   103k    17G  /var/run
none                    17G      0    17G  /var/lock
none                   9,9G   3,3G   6,1G  /var/lib/ureadahead/debugfs
/dev/sda2               64G    17G    48G  /usr/local
/dev/md0               147G    43G   105G  /mnt
/dev/sde1              400G   203G   198G  /mnt/usbdisk

eg: /dev/sda1 used space is 3,3GB should not reach 80%, if reaches then it should send mail.

Solution

Here's an awk script I wrote years ago to do this very thing. Just put it in cron to run at a specified schedule.

#!/bin/sh

/bin/df | \

/usr/bin/awk '{if($5 ~ "%" && $6 !~ "proc") {used=$5} else {used=""}; \
              sub(/%/, "", used); \

              if(used > 80) print $6 " is at " used"%"}' |\
                  mail -s "Disk usage over limit" user@domain.com