#!/bin/sh
#
# Plugin to check system memory
# by hugme (nagios@hugme.org)
# You can find my checks here: https://github.com/hugme/Nag_checks
# Nagios script to check memory usage on linux server
# version 2.0.0
#
##########################################################

MEMINFO="/proc/meminfo"
OOMKILLINFO="/proc/vmstat"

##########################################################
# We call them functions because they're fun
##########################################################

print_help() {
cat << EOF
Linux Memory Plugin for Nagios
Copyright (c) hugme (nagios@hugme.org)
Version: 1.2.0
Last Modified: 10-07-2014
License: This software can be used for free unless I meet you, then you owe me lunch.

Usage: check_linux_memory -w [warning %] -c [critical %]

Options:
 -w [0-99]		= Your warning %. 20 means 20% of your memory can remain before a warning alarm. Do not use the % sign.
 -c [0-99]		= Your critical %. 10 means 10% of your memory can remain before a critical alarm. Do not use the % sign.
 -d [K,M,G,T]	= divider K=kilobytes, M=megabytes, G=gigabytes, T=terabytes
 -f		= Included for backwards compatability to older versions
 -n		= Don't Include cached memory as free memory when calculating your percentage free
 -K		= Don't check the OutOfMemory Kill counter
 -k [0-9999]	= Threshold for OOMKill alert (default: 0)
 -A		= Don't check awk capabilities (as of 2024: mawk can't printf an integer over 2^31)
EOF
	}

invalid_type() {
	echo "\nInvalid $1\n"
	print_help
	exit 3
	}

##############################################
## Suck in the user input
##############################################


while test -n "$1"; do
 case $1 in
  --help) print_help ; exit 0 ;;
  -A) AWK_CHECK=0 ;;
  -h) print_help ; exit 0 ;;
  -w) WARN="$2"; shift ;;
  -c) CRIT="$2"; shift ;;
  -d) DIV="$2"; shift ;;
  -n) NC=1 ;;
  -k) THRESHOLD_OOMKILL="$2"; shift ;;
  -K) DISABLE_OOMKILL=1 ;;
 esac
 shift
done

##############################################
## Set the defaults if needed
##############################################

[ -z "$WARN" ] && WARN=20
[ -z "$CRIT" ] && CRIT=10
[ -z "$DIV" ] && DIV=M
[ -z "$FC" ] && FC=0
[ -z "$DISABLE_OOMKILL" ] && DISABLE_OOMKILL=""
[ -z "$AWK_CHECK" ] && AWK_CHECK=1
[ -z "$THRESHOLD_OOMKILL" ] && THRESHOLD_OOMKILL=0

##############################################
## Check awk capabilities
##############################################

if [ "$AWK_CHECK" -gt 0 ] && [ "$( awk 'BEGIN{ printf "%ld", 3000000000 }' )" != "3000000000" ]; then
	echo "UNKNOWN this version of awk is not able to display big numbers."
	exit 3
fi

##############################################
## Check user input
##############################################

[ ! -z `echo $WARN | tr -d [:digit:]` ] && invalid_type "Warning: Warning value can only contain numbers"
[ ! -z `echo $CRIT | tr -d [:digit:]` ] && invalid_type "Critical: Critical value can only contain numbers"
[ "${WARN%.*}" -ge 100 ] && invalid_type "Warning: Warning must be smaller than 100%"
[ "${CRIT%.*}" -ge 100 ] && invalid_type "Critical: Critical must be smaller than 100%"
[ "${CRIT%.*}" -gt "${WARN%.*}" ] && invalid_type "Critical: Your Warning must be Higher than your Critical"

case $DIV in
	k|K) DIVNUM=1024;;
	m|M) DIVNUM=1048576;;
	g|G) DIVNUM=1073741824;;
	t|T) DIVNUM=1099511627776;;
	*) invalid_type;;
esac

[ ! -f "$MEMINFO" ] && {
	echo "Your Memory info file seems to be missing"
	exit 1
	}

if [ -z "$DISABLE_OOMKILL" ] && ! grep '^oom_kill ' "$OOMKILLINFO" >/dev/null 2>&1; then
	echo "UNKNOWN threshold set for oom_kill but the counter not available in '$OOMKILLINFO'."
	exit 3
fi

##############################################
## Do the work
## Pull the memory file into awk
## grab the lines we need
## Print the information
##############################################

RESULT=$(awk -v warnperct=$WARN -v critperct=$CRIT -v div=$DIV -v divnum=$DIVNUM -v nc=$NC -v disable_oomkill=$DISABLE_OOMKILL -v threshold_oomkill=$THRESHOLD_OOMKILL '
{
	UnitQuantity["B"]=1
	UnitQuantity["kB"]=1024
	UnitQuantity["MB"]=1048576
	UnitQuantity["GB"]=1073741824
	UnitQuantity["TB"]=1099511627776
}
/^MemTotal:/ { tot=$2*UnitQuantity[$3] }
/^MemFree:/ { free=$2*UnitQuantity[$3] }
/^Buffers:/ { buff=$2*UnitQuantity[$3] }
/^Cached:/ { cache=$2*UnitQuantity[$3] }
/^Active:/ { active=$2*UnitQuantity[$3] }
/^Inactive:/ { inactive=$2*UnitQuantity[$3] }
/^oom_kill / { oomkill=$2 }
END { if ( nc != 1 ) { free=free+cache+buff }
	{
		freeperct=free/tot*100
		warn=int(warnperct*tot/100)  # convert to int to avoid dealing with weird display
		crit=int(critperct*tot/100)
	}
	if ( freeperct > warnperct ) { result="OK" ; xit="0"}
	if ( freeperct <= warnperct ) {
		if ( freeperct > critperct ) { result="WARNING" ; xit="1" }
		else if ( freeperct <= critperct ) { result="CRITICAL" ; xit="2" }
		}
	if ( disable_oomkill != 1 ) {
		oomkill_display=" OOMKills:"oomkill
		oomkill_perfdata=" oomkill="oomkill";;"threshold_oomkill";0"
		if ( oomkill > threshold_oomkill ) { result="CRITICAL - Out of memory kills detected" ; xit="2" }
	}
	{
		printf "%d MEMORY %s - %.2f%% Free - Total:%.1f%s", xit, result, freeperct, tot/divnum, div
		printf " Active:%.1f%s", active/divnum, div
		printf " Inactive:%.1f%s", inactive/divnum, div
		printf " Buffers:%.1f%s", buff/divnum, div
		printf " Cached:%.1f%s", cache/divnum, div
		printf "%s", oomkill_display
		printf " |Active=%ldB;;;0;%ld", active, tot
		printf " Buffers=%ldB;;;0;%ld", buff, tot
		printf " Cached=%ldB;;;0;%ld", cache, tot
		printf " Free=%ldB;%ld;%ld;0;%ld", free, warn, crit, tot
		printf " Inactive=%ldB;;;0;%ld", inactive, tot
		printf "%s", oomkill_perfdata
	}
}' "$MEMINFO" "$OOMKILLINFO" )

echo ${RESULT#* }
exit ${RESULT%% *}