#!/bin/bash
function quit {
    case $1 in
        0)
            echo "OK$2"
        ;;
        1)
            echo "WARNING$2"
        ;;
        2)
            echo "CRITICAL$2"
        ;;
        3)
            echo "UNKNOWN$2"
        ;;
    esac
    exit $1
}
CHECKNET=`host kernel.org | grep "has address" | head -n 1`
if [ -z "$CHECKNET" ]; then
    quit 0
fi
CHECKHOST=`ping -c 3 -w 1 kernel.org | grep received | awk '{ print $4 }'`
if [ $CHECKHOST -lt 1 ]; then
    quit 0
fi
KERNEL=`uname -r`
SUBVERSION=`echo $KERNEL | sed -r "s/.*([0-9]+)$/\1/"`
MAINKERNEL=`echo $KERNEL | sed -r "s/([0-9]*)$//;s/([.]{1})$//"`

LASTKERNEL=`wget -q kernel.org -O /dev/stdout | sed -r "s/<[^>]*>//g;s/^[\ ]*//" | grep -i -A 1 stable | grep ${MAINKERNEL}`
echo -n "Check kernel ($KERNEL): "
if [ -z "${LASTKERNEL}" ]; then
    quit 2 ": $KERNEL too old"
else
    LASTSUBKERNEL=`echo ${LASTKERNEL} | sed -r "s/.*([0-9]+)$/\1/"`
    if [ "${SUBVERSION}" != "${LASTSUBKERNEL}" ]; then
        quit 1 ": Update available ${LASTKERNEL}"
    else
        quit 0
    fi
fi
quit 3