shell script for monitoring server disk usage

monitor_du

#!/bin/sh
EXCLUDE=( Filesystem devtmpfs tmpfs );
USAGE_THRESHOLD=85;

PREV_IFS=$IFS;          # save the old IFS so we can restore it later
IFS="|";                # change the internal field separator to a pipe
EX="${EXCLUDE[*]}";     # join exclude partitions with pipe separator
IFS=$PREV_IFS;          # restore IFS

df -h | grep -Ev "^${EX}" | awk '{print $5 " " $1}' | while read output;
do
        percentage=$(echo $output | awk '{print $1}' | cut -d'%' -f1)
        part=$(echo $output | awk '{print $2}')
        hn=$(hostname)
        if [ $percentage -gt $USAGE_THRESHOLD ]; then
                echo "Running out of disk space on partition $part ($percentage%) on server $hn" |
                mail -s "$hn running out of disk space on $part" <email-address>
        fi
done