插件check_log相关代码如下：

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#! /bin/sh

#
# Log file pattern detector plugin for Nagios
# Written by Ethan Galstad ()
# Last Modified: 07-31-1999
#
# Usage: ./check_log <log_file> <old_log_file> <pattern>
#
# Description:
#
# This plugin will scan a log file (specified by the <log_file> option)
# for a specific pattern (specified by the <pattern> option).  Successive
# calls to the plugin script will only report *new* pattern matches in the
# log file, since an copy of the log file from the previous run is saved
# to <old_log_file>.
#
# Output:
#
# On the first run of the plugin, it will return an OK state with a message
# of "Log check data initialized".  On successive runs, it will return an OK
# state if *no* pattern matches have been found in the *difference* between the
# log file and the older copy of the log file.  If the plugin detects any
# pattern matches in the log diff, it will return a CRITICAL state and print
# out a message is the following format: "(x) last_match", where "x" is the
# total number of pattern matches found in the file and "last_match" is the
# last entry in the log file which matches the pattern.
#
# Notes:
#
# If you use this plugin make sure to keep the following in mind:
#
#    1.  The "max_attempts" value for the service should be 1, as this
#        will prevent Nagios from retrying the service check (the
#        next time the check is run it will not produce the same results).
#
#    2.  The "notify_recovery" value for the service should be 0, so that
#        Nagios does not notify you of "recoveries" for the check.  Since
#        pattern matches in the log file will only be reported once and not
#        the next time, there will always be "recoveries" for the service, even
#        though recoveries really don't apply to this type of check.
#
#    3.  You *must* supply a different <old_file_log> for each service that
#        you define to use this plugin script - even if the different services
#        check the same <log_file> for pattern matches.  This is necessary
#        because of the way the script operates.
#
# Examples:
#
# Check for login failures in the syslog...
#
#   check_log /var/log/messages ./check_log.badlogins.old "LOGIN FAILURE"
#
# Check for port scan alerts generated by Psionic's PortSentry software...
#
#   check_log /var/log/message ./check_log.portscan.old "attackalert"
#

# Paths to commands used in this script.  These

# may have to be modified to match your system setup.
# TV: removed PATH restriction. Need to think more about what this means overall
#PATH=""
#将文件编码修改，解决乱码问题
cd /home/syslogin/2.250log/serverlog
#iconv -f gbk -t utf8 xh.log > xhutf8.log 
#iconv -f gbk -t utf8 dj.log > djutf8.log
ECHO="/bin/echo"
GREP="/bin/egrep"
DIFF="/usr/bin/diff"
TAIL="/usr/bin/tail"
CAT="/bin/cat"
RM="/bin/rm"
CHMOD="/bin/chmod"
TOUCH="/bin/touch"

PROGNAME=`/bin/basename $0`

PROGPATH=`echo $0 | sed -e 's,[\\/][^\\/][^\\/]*$,,'`
REVISION="1.4.15"

. $PROGPATH/utils.sh

print_usage() {

    echo "Usage: $PROGNAME -F logfile -O oldlog -q query"
    echo "Usage: $PROGNAME --help"
    echo "Usage: $PROGNAME --version"
}

print_help() {

    print_revision $PROGNAME $REVISION
    echo ""
    print_usage
    echo ""
    echo "Log file pattern detector plugin for Nagios"
    echo ""
    support
}

# Make sure the correct number of command line

# arguments have been supplied

if [ $# -lt 1 ]; then

    print_usage
    exit $STATE_UNKNOWN
fi

# Grab the command line arguments

#logfile=$1

#oldlog=$2
#query=$3
exitstatus=$STATE_WARNING #default
while test -n "$1"; do
    case "$1" in
        --help)
            print_help
            exit $STATE_OK
            ;;
        -h)
            print_help
            exit $STATE_OK
            ;;
        --version)
            print_revision $PROGNAME $REVISION
            exit $STATE_OK
            ;;
        -V)
            print_revision $PROGNAME $REVISION
            exit $STATE_OK
            ;;
        --filename)
            logfile=$2
            shift
            ;;
        -F)
            logfile=$2
            shift
            ;;
        --oldlog)
            oldlog=$2
            shift
            ;;
        -O)
            oldlog=$2
            shift
            ;;
        --query)
            query=$2
            shift
            ;;
        -q)
            query=$2
            shift
            ;;
        -x)
            exitstatus=$2
            shift
            ;;
        --exitstatus)
            exitstatus=$2
            shift
            ;;
        *)
            echo "Unknown argument: $1"
            print_usage
            exit $STATE_UNKNOWN
            ;;
    esac
    shift
done

# If the source log file doesn't exist, exit

if [ ! -e $logfile ]; then

    $ECHO "Log check error: Log file $logfile does not exist!\n"
    exit $STATE_UNKNOWN
elif [ ! -r $logfile ] ; then
    $ECHO "Log check error: Log file $logfile is not readable!\n"
    exit $STATE_UNKNOWN
fi

# If the old log file doesn't exist, this must be the first time

# we're running this test, so copy the original log file over to
# the old diff file and exit

if [ ! -e $oldlog ]; then

    $CAT $logfile > $oldlog
    $ECHO "Log check data initialized...\n"
    exit $STATE_OK
fi

# The old log file exists, so compare it to the original log now

# The temporary file that the script should use while

# processing the log file.
if [ -x /bin/mktemp ]; then
    tempdiff=`/bin/mktemp /tmp/check_log.XXXXXXXXXX`
else
    tempdiff=`/bin/date '+%H%M%S'`
    tempdiff="/tmp/check_log.${tempdiff}"
    $TOUCH $tempdiff
    $CHMOD 600 $tempdiff
fi

$DIFF $logfile $oldlog | $GREP -v "^>" > $tempdiff

# Count the number of matching log entries we have

count=`$GREP -c "$query" $tempdiff`

# Get the last matching entry in the diff file

lastentry=`$GREP "$query" $tempdiff | $TAIL -1`

$RM -f $tempdiff

$CAT $logfile > $oldlog

if [ $count -lt 2 ]; then # no matches, exit with no error

    gj=`tail -1 $logfile | cut -c 1-20`
    $ECHO "日志正常,检测最后时间是$gj,没有产生关键字眼→→$query"
    exitstatus=$STATE_OK
else # Print total matche count and the last entry we found
    gj=`echo $lastentry | cut -c 1-21`
    $ECHO "警告信息数为:$count 条,产生关键字眼 $query"
    exitstatus=$STATE_CRITICAL
fi

exit $exitstatus

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1，首先定义命令check_log;

#cd /usr/local/nagios/etc/objects

#vi commands.cfg

      # 'check_log'command detinition

define command{
    command_name     check_log
    command_line     $USER1$/check_log -F "$ARG1$" -O "$ARG2$" -q "$ARG3$"
}

2,定义监控参数；

define host{

  use  linux-server
  host_name     log-localhost
  alias         the log of localhost
  address    127.0.0.1
}
define service{
      use  local-service
     host_name   log-localhost
    service_description   messages日记关键字stop
    check_command        check_log!/var/log/messages!/var/log/messages.arc!stop

}

define service{
      use  local-service
     host_name   log-localhost
    service_description  messages日记关键字nagios error
    check_command        check_log!/var/log/messages!/var/log/messages.arc!nagios error
}