#!/bin/bash
# nagios plugin to check memory usage on Linux
#
USAGE="`basename $0` [-w|--warning]<percent free> [-c|--critical]<percent free>"
THRESHOLD_USAGE="WARNING threshold must be greater than CRITICAL: `basename $0` $*"
critical=""
warning=""
STATE_OK=0
STATE_WARNING=1
STATE_CRITICAL=2
STATE_UNKNOWN=3
# print usage
if [[ $# -lt 4 ]]
then
	echo ""
	echo "Wrong Syntax: `basename $0` $*"
	echo ""
	echo "Usage: $USAGE"
	echo ""
	exit 0
fi
# read input
while [[ $# -gt 0 ]]
  do
        case "$1" in
               -w|--warning)
               shift
               warning=$1
        ;;
               -c|--critical)
               shift
               critical=$1
        ;;
        esac
        shift
  done
# verify input
if [[ $warning -eq $critical || $warning -lt $critical ]]
then
	echo ""
	echo "$THRESHOLD_USAGE"
	echo ""
        echo "Usage: $USAGE"
	echo ""
        exit 0
fi
# Total memory available in MB
total=`free -m | head -2 | tail -1 | gawk '{print $2}'`
# Total memory used in MB
used=`free -m | head -2 | tail -1 | gawk '{print $3}'`
# Calc total minus used in MB
free=`free -m | head -2 | tail -1 | gawk '{print $7}'`

percent=$(awk "BEGIN {printf \"%0.0f\",100*${free}/${total}}")

# Memory usage (RSS) summed per user, in MB, as extra performance data
user_perf=$(ps -eo user:32,rss --no-headers | gawk '{mem[$1]+=$2} END {for (u in mem) printf "'\''mem_%s'\''=%.0fMB;;;; ", u, mem[u]/1024}')

if [[ "$percent" -le  $critical ]]
	then
		echo "CRITICAL - $free MB ($percent%) Free Memory|'Free memory'=$percent%;$warning;$critical;0;100 $user_perf"
		exit 2
fi
if [[ "$percent" -le  $warning ]]
        then
                echo "WARNING - $free MB ($percent%) Free Memory|'Free memory'=$percent%;$warning;$critical;0;100 $user_perf"
                exit 1
fi
if [[ "$percent" -gt  $warning ]]
        then
                echo "OK - $free MB ($percent%) Free Memory |'Free memory'=$percent%;$warning;$critical;0;100 $user_perf"
                exit 0
fi

