Simple Bash DNS checker. Intended for bulk lookup by feeding it a list of hostnames.

dnscheck.sh

#!/bin/bash

# Does a host lookup of specified record type for given hostname(s). 
# Accepts single hostnames or a file containing a list of hostnames. 
# The optional 3rd parameter (expected value) gives a colored output
# for fast and easy visual analyzing.

# Usage: ./dnscheck [RECORD TYPE] [INPUT(FILE)] ('expected value')

EXPECTED="$3"

function main {
    if [[ ! "$1" ]] & [[ ! "$2" ]]; then
        echo -e "\e[1;31mI need something to work with...\e[0m"
        echo "Usage: ./dnscheck.sh [RECORD_TYPE] [INPUT] (expected value)"
    else
        if [[ -f "$2" ]]; then
            target=`cat "$2"`
        else
            target="$2"
        fi

        case $1 in
            "A" ) getA "$target" ;;
            "NS" ) getNS "$target" ;;
            "MX" ) getMX "$target" ;;
            * ) echo "Not a valid record" ;;
        esac
    fi
}

function getNS {
    for i in $1;
    do
        domain=`echo "$i" |rev |cut -d'.' -f 1,2 |rev`
        nameservers=`host -t NS $domain |awk '{print $4}'`
        if [[ ! "$EXPECTED" ]]; then
            echo -e "\e[1m$domain:\e[0m\n$nameservers"
        elif [[ $nameservers != *$EXPECTED* ]]; then
            echo -e "\e[1;31m$domain\e[0m:\n$nameservers"
        else
            echo -e "\e[1;32m$domain\e[0m:\n$nameservers"
        fi
    done
}

function getA {
    for i in $1;
    do
        ip_address=`host -t A $i |grep 'has address' |awk '{print $4}'`
        if [[ ! "$EXPECTED" ]]; then
            echo -e "\e[1m$i\e[0m: $ip_address"
        elif [[ $ip_address != *$EXPECTED* ]]; then
            echo -e "\e[1;31m$i\e[0m: $ip_address"
        else
            echo -e "\e[32m$i\e[0m: $ip_address"
        fi
    done
}

function getMX {
    for i in $1;
    do
        domain=`echo "$i" |rev |cut -d'.' -f 1,2 |rev`
        mxrecords_prio=`host -t MX $domain |grep 'handled by' |awk '{print $7,$6}'`
        if [[ ! "$EXPECTED" ]]; then
            echo -e "\e[1m$i\e[0m:\n$mxrecords_prio"
        elif [[ $mxrecords_prio != *$EXPECTED* ]]; then
            echo -e "\e[1;31m$i\e[0m:\n$mxrecords_prio"
        else
            echo -e "\e[32m$i\e[0m:\n$mxrecords_prio"
        fi
    done
}

main $1 $2