Returns records from DNS servers. Built to be used as an external check from Zabbix.

dnscheck.sh

#!/bin/bash
#
# DNS Check Script
# Given two parameters, the DNS record type and a domainname
# Will return the record if exists, 'NXDOMAIN' if it doesnt.
#

DIG='/usr/bin/dig'
VALID_RECORDS=(
  'mx'
  'a'
  'aaaa'
  'cname'
  'ns'
  'ptr'
  'soa'
  'spf'
  'srv'
  'txt'
)

# Checks to see if arg1 is in array arg2     
# first line lets us pass a reference to a variable to this function
function containsItem() {
    eval maharray=\$\{${2}[@]\}                            
    case "${maharray}" in *"${1}"*) return 0 ;; esac
    return 1
}

# pulled from here: http://www.linuxjournal.com/content/validating-ip-address-bash-script
function valid_ip() {
    local  ip=$1
    local  stat=1

    if [[ $ip =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]; then
        OIFS=$IFS
        IFS='.'
        ip=($ip)
        IFS=$OIFS
        [[ ${ip[0]} -le 255 && ${ip[1]} -le 255 \
            && ${ip[2]} -le 255 && ${ip[3]} -le 255 ]]
        stat=$?
    fi
    return $stat
}

# exit with error if no name passed
if [ -z "${2}" ]; then
    exit 5
fi

# Exit if not valid record
RR_RECORD="$(echo ${1} | awk '{print tolower($0)}')"
if ! $(containsItem $RR_RECORD VALID_RECORDS); then
   echo "Please pass valid resource record"
   exit 1
fi 

# See if user passed specific DNS Server for us to try
if valid_ip ${3}; then
    RESULT="$($DIG +short @${3} ${1} ${2})"
else
    RESULT="$($DIG +short ${1} ${2})"
fi

# Return the output of our DNS query
if [ -z "${RESULT}" ]; then
    echo 'NXDOMAIN'
    exit 0
else
    echo "${RESULT}" | sort -n
    exit 0
fi