check_memory

#!/bin/sh
################################################################################
# Linux memory utilization nagios plugin                                       #
# Copyright (c) 2019 Frostbyte <frostbytegr@gmail.com>                         #
#                                                                              #
# Credits:                                                                     #
# <github.com/hugme> - sample code for linux nagios checks                     #
# <devel@nagios-plugins.org> - plugin development guidelines                   #
#                                                                              #
# This program is free software: you can redistribute it and/or modify         #
# it under the terms of the GNU General Public License as published by         #
# the Free Software Foundation, either version 3 of the License, or            #
# (at your option) any later version.                                          #
#                                                                              #
# This program is distributed in the hope that it will be useful,              #
# but WITHOUT ANY WARRANTY; without even the implied warranty of               #
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the                #
# GNU General Public License for more details.                                 #
#                                                                              #
# You should have received a copy of the GNU General Public License            #
# along with this program.  If not, see <http://www.gnu.org/licenses/>.        #
################################################################################

# Usage helper function
usage() {
cat << EOF
Usage:
$0 [-w util_warn_threshold] [-c util_warn_threshold] [-u friendly_unit] [-n]
Friendly units: K=Kilobytes, M=Megabytes, G=Gigabytes, T=Terabytes.
Example: $0 -w 80 -c 90 -u M
Cached memory and buffers will not be included in system's free memory when calculating utilization, with the -n argument.
EOF
exit 3
}

# Input error helper function
inputError() {
	# Throw supplied error message and exit
	echo "$1"
	exit 3
}

# Parse user-supplied arguments
while getopts ":w:c:u:n" inputArgs; do
	case "${inputArgs}" in
		w) thresholdWarn="${OPTARG}" ;;
		c) thresholdCrit="${OPTARG}" ;;
		u) friendlyUnit="${OPTARG}" ;;
		n) noCachedMemory=1 ;;
		*) usage ;;
	esac
done
shift $((OPTIND-1))

# Apply any defaults if needed
[ -z "$friendlyUnit" ] && friendlyUnit=M
[ -z "$noCachedMemory" ] && noCachedMemory=0

# Validate any user-supplied arguments
[ -z "$thresholdWarn" ] || {
	[ -z $(echo $thresholdWarn | tr -d [:digit:]) ] || inputError "The warning threshold value may only contain numbers."
	[ $thresholdWarn -le 0 ] || [ $thresholdWarn -ge 100 ] && inputError "The warning threshold value must be between 1 and 99."
}
[ -z "$thresholdCrit" ] || {
	[ -z $(echo $thresholdCrit | tr -d [:digit:]) ] || inputError "The critical threshold value may only contain numbers."
	[ $thresholdCrit -le 0 ] || [ $thresholdCrit -ge 100 ] && inputError "The critical threshold value must be between 1 and 99."
}
[ ! -z "$thresholdWarn" ] && [ ! -z "$thresholdCrit" ] && [ $thresholdCrit -lt $thresholdWarn ] && inputError "The critical threshold value must be higher than or equal to the warning threshold value."
case $friendlyUnit in
	k|K) unitDivider=1 ;;
	m|M) unitDivider=1024 ;;
	g|G) unitDivider=1048576 ;;
	t|T) unitDivider=1073741824 ;;
	*) inputError "The friendly unit value may only be one of the following: K, M, G, or T. (Case Insensitive)" ;;
esac

# If the memory information file is missing
memoryInfo="/proc/meminfo"
[ -f "$memoryInfo" ] || {
	# Throw error and exit
	echo "The memory information file $memoryInfo is missing."
	exit 3
}

# Disable any non-specified thresholds
[ -z "$thresholdWarn" ] && thresholdWarn=0
[ -z "$thresholdCrit" ] && thresholdCrit=0

#Calculate and construct a standard nagios response
result=$(awk \
	-v thresholdWarn=$thresholdWarn \
	-v thresholdCrit=$thresholdCrit \
	-v friendlyUnit=$friendlyUnit \
	-v unitDivider=$unitDivider \
	-v noCachedMemory=$noCachedMemory \
	'/^MemTotal:/	{ memTotal=$2 }
	/^MemFree:/	{ memFree=$2 }
	/^Buffers:/	{ memBuffers=$2 }
	/^Cached:/	{ memCached=$2 }
	/^Active:/	{ memActive=$2 }
	/^Inactive:/	{ memInactive=$2 }
	END {
		if (noCachedMemory == 0) {
			memFree=memFree+memCached+memBuffers
		}
		memUsed=memTotal-memFree
		memUtil=memUsed/memTotal*100
		result="OK"
		exitCode=0
		if (memUtil > thresholdCrit && thresholdCrit > 0) {
			result="CRITICAL"
			exitCode=2
		} else if (memUtil > thresholdWarn && thresholdWarn > 0) {
			result="WARNING"
			exitCode=1
		}
		print exitCode" "result" - \
		Utilization: "memUtil"% \
		Total: "memTotal/unitDivider friendlyUnit" \
		Active: "memActive/unitDivider friendlyUnit" \
		Inactive: "memInactive/unitDivider friendlyUnit" \
		Buffers: "memBuffers/unitDivider friendlyUnit" \
		Cached: "memCached/unitDivider friendlyUnit" | \
		util="memUtil";"thresholdWarn";"thresholdCrit";0 \
		total="memTotal";0;0;0 \
		active="memActive";0;0;0 \
		inactive="memInactive";0;0;0 \
		buffers="memBuffers";0;0;0 \
		cached="memCached";0;0;0"
	}' "$memoryInfo")

# Respond and exit
echo ${result#* }
exit ${result%% *}