ZFS check script

#!/bin/sh

echo "---------------------------------------------"

PIDFILE=/var/run/zfs/zfs_check.pid
EXPECTET_RESULT="all pools are healthy"
BAD_OUTPUT_FILE=/tmp/zfs_broken.log
MAILADDR="someuser@example.com;otheruser@example.org"
IFS=";"

ZPOOL=/sbin/zpool

send_mail() {
        echo "Sending mail to " $1
        echo $($ZPOOL status) | /usr/bin/mail -s $2 $1
}

if [ -e $PIDFILE ]
then
         PIDC=$(/bin/cat $PIDFILE)
         echo "ZFS check is already running!       PID: "$PIDC
         echo "Please use \"kill $PIDC\" to stop the Process (if you want to (because it hung,ect...))"
         echo "And remove the PID File by hand ($PIDFILE)"
         echo
else
         echo "Creating PID file"
         PID=$(echo $$)
         echo $PID > $PIDFILE
         RESULT=$($ZPOOL status -x)
         if [ "$RESULT" = "$EXPECTET_RESULT" ]
         then
                 #echo "Everything OK"
                 echo $RESULT

                  if [ -e $BAD_OUTPUT_FILE ]
                  then
                          echo "Normal working conditions reached."
                          echo "Removing bad output file..."
                          rm $BAD_OUTPUT_FILE

              set -- $MAILADDR
                          for addr in $@
                          do
                                   send_mail $addr "ZFS normal working conditions restored on $(hostname)"
                          done

                  fi
         else
                 if [ -e $BAD_OUTPUT_FILE ]
                 then
                         echo "Already send something..."
             echo "Updating output log"
                         date > $BAD_OUTPUT_FILE
                         $ZPOOL status >> $BAD_OUTPUT_FILE
                 else
                         echo "SOMETHING IS WRONG!"
                         date > $BAD_OUTPUT_FILE
                         $ZPOOL status >> $BAD_OUTPUT_FILE

                         set -- $MAILADDR
                         for addr in $@
                         do
                                  send_mail $addr "ZFS ERROR on $(hostname)"
                         done
                 fi
         fi

        echo "Removing PID file"
        /bin/rm $PIDFILE

fi

#---additional steps:
#Create a folder (or change the above path in /var/run/)
#mkdir /var/run/zfs/
#
#chmod +x /PATH/TO/THIS/SCRIPT.sh
#
#crontab -e
##ZFS Disk failure check
#*   *  *  *  *  /PATH/TO/THIS/SCRIPT.sh > /dev/null 2>&1
#
#---be sure that the user who executes the script can access the folder /var/run for PID file creation
#---or just comment it out, if you don't want to crate a PID file
#---zpool should obviously also be accessible for this user :)
#
#last update 2013-08-16