Disk space cron monitor for Ubuntu

df.sh

#!/bin/bash
ADMIN="help@example.com"
ALERT=95
df -H  | grep -vE '^Filesystem|none|tmpfs|cdrom|varrun|varlock|udev|devshm|boot' | awk '{ print $4 " " $5 " " $6 }' | while read output;
do
  usep=$(echo $output | awk '{ print $2}' | cut -d'%' -f1  )
  partition=$(echo $output | awk '{ print $3 }' )
  free=$(echo $output | awk '{ print $1 }' )
  if [[ $usep -ge $ALERT ]]; then
    echo "Running out of space $partition ($usep% used, $free avail)
on $(hostname) at $(date)" |
     mail -s "Alert: Almost out of disk space $(hostname)" $ADMIN
  fi
done

Possible crontab to run hourly:

35 * * * * /usr/local/bin/df.sh