monitor the disk used

#!/bin/sh
#
#Name    : df-monitor.sh
#Author  : cnscn
#Mail    : [email protected]
#Time    : 2006-02-27 00:10
#Purpose : monitor the disk free, when the rate of  disk used is greater than 85% or another value, then mail you the info
#          And you can use wall instead of mail
#
#Usage:
#  crontab -e
#     */30 * * * * /opt/desktop-softs/df-monitor.sh >/dev/null 2>&1
#
#Result:
#  $mail
#    Subject: disk free warning
#
#    Disk: /dev/hda1    Whole: 12.22G   Used: 8.85G  UsedRate: 72.38%
#
###################################################################

#the mail subject
subject="disk free warning"

#the mail where to send to
tomail="root@localhost"

#function toSendMail
#Param : the content to mail

function toSendMail()
{
  if [ -n  "$*" ] ; then
     echo -e "$*" | mail -s "$subject"  "$tomail"   #you can use wall instead of mail
  fi  
}

#to calculte the rate of the disks used, and when the result is not null ,send the mail
toSendMail $(df | awk '(NR >1 && ($3/$2)>0.85 ) {printf "\"Disk: %s  Whole: %-3.2fG   Used: %-3.2fG  UsedRate: %2.2f%\"\\n",$1,$2/1000000,$3/1000000,$3/$2*100; }')