Nagios plugin that let you search within a logfile for a pattern ( could be empty ) and have a critical/warning value when the number of lines matching the pattern exceeds critical/warning within the last N minutes

check_last_logs_lines.sh

#!/usr/bin/env bash

##    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.
##

# ===============
# check_last_logs_lines - plugin to check the number of matching lines in a temporal timeframe
# ===============
# * Author: Andrea Baccega

# version 1.0 (12.Mar.2013)
# plugin return codes:
# 0     OK
# 1     Warning
# 2     Critical
# 3     Unknown

while getopts "hw:c:m:l:r:" opt
do
        case $opt in
                h)
                        showhelp=1
                        break
                ;;
                w)
                        declare -r warning="$OPTARG"
                ;;
                c)
                        declare -r critical="$OPTARG"
                ;;
                m)
                        declare -r minutes="$OPTARG"
                ;;
                l)
						declare -r logfile="$OPTARG"
                ;;
                r)
						declare -r regexp="$OPTARG"
				;;
                
        esac
done



printUsage() {
        echo "Usage: $0 [-h]  -l <logfile> -m <minutes> -r <regexp> -w <warning> -c <critical> "
        echo ""
        echo "Example: $0 -l /var/log/apache_errors.log -r 'HTTP/1\\.1\" 404' -m 5 -w 10 -c 30 "
}

printHelp() {
        printUsage
        echo ""
        echo "This plugin checks the number of messages processed by the logfile you specify in the last N minutes. matching an optional regexp"
        echo ""
        echo "For more details, see inside the script ;)"
        echo ""
        exit 3
}

getnrMesgs () {

	CURTIME=`date +%s`

	TIMEEGREP="("
	TIMEEGREP=$TIMEEGREP$(date +%R)
	for ((i=1;i<=$minutes; i++)); do
		TMP=$(date --date="@$(($CURTIME - $i * 60))" +%R)
		TIMEEGREP="$TIMEEGREP|$TMP"
	done;
	TIMEEGREP="$TIMEEGREP)"

	egrep "${regexp}" $logfile | tail -$(($critical + 1)) | egrep "${TIMEEGREP}" | wc -l


	
}

if [ "$showhelp" = "1" ]; then
        printHelp
        exit 3
fi

if [ ! "$warning" ] || [ ! "$critical" ] || [ ! "$minutes" ] || [ ! "$logfile" ]; then
        printUsage
        exit 3
fi

if [ ! $minutes -ge "0" ] || [ ! $minutes -le "180" ]; then
		printUsage
		exit 3
fi

if [ ! "$logfile" ]; then
        echo "Could not find the specified logfile!"
        exit 3
fi


if [ $warning -ge $critical ]; then
        echo "<warning> has to be smaller than <critical>!"
        exit 3
fi

nrmsgs=`getnrMesgs`

echo "Matched log entries in the last $minutes minutes: $nrmsgs"

if [ "$nrmsgs" -ge "$critical" ]; then
        exit 2
elif [ "$nrmsgs" -ge "$warning" ]; then
        exit 1
else
        exit 0
fi