Nagios3 plugin to check free memory

gistfile1.sh

#!/bin/sh
TOTAL="`free -m | grep Mem | sed -r 's/\s+/ /g' | cut -f2 -d' '`"
FREE="`free -m | grep Mem | sed -r 's/\s+/ /g' | cut -f4 -d' '`"
FREEP="`echo "$FREE*100/$TOTAL" | bc`"

usage(){
cat << EOF
usage: $0 options

This script tells how much of memory is available

OPTIONS:
   -h      Show this message
   -c      critical percentage of free memory
   -w      warning percentage of free memory
EOF
}

while getopts "hw:c:" OPTION
do
  case $OPTION in
    h)
      usage()
      exit
      ;;
    w)
      WARNING=$OPTARG
      ;;
    c)
      CRITICAL=$OPTARG
      ;;
  esac
done

[ -z $WARNING ] && echo "MEM UNKNOWN - Need to pas -w option" && exit 3
[ -z $CRITICAL ] && echo "MEM UNKNOWN - Need to pass -c option" && exit 3
[ $WARNING -le $CRITICAL ] && echo "MEM UNKNOWN - -c has to be less than -w" && exit 3

STATUS="OK"
[ $FREEP -le $WARNING ] && STATUS="WARNING"
[ $FREEP -le $CRITICAL ] && STATUS="CRITICAL"

echo "MEM $STATUS - $FREEP% free ($FREE MB out of $TOTAL MB) |mem=${FREE}MB;$WARNING;$CRITICAL;0;$TOTAL"

[ $STATUS = "OK" ] && exit 0
[ $STATUS = "WARNING" ] && exit 1
[ $STATUS = "CRITICAL" ] && exit 2
exit3