#!/bin/sh
# sh. not fucking bash.

if [ ! $# -gt 0 ]; then
    echo "Usage: $0 <inputfile> [filterdomain]"
    exit 1;
fi

tld=$1
shift
digopts='+norecurse +nocmd +nocomments +nostats +noadditional +noquestion'

domfilter=0
# handle the filterdomain
if [ $# -gt 0 ]; then
    domfilter=1
    filter_domain=$1
    echo "using domfilter: '$filter_domain'"
fi

get_tldns() {
    tld=`echo $1 | sed 's/^.*\.//'`
    host -t ns $tld. | head -1 | awk '{print $4}'
}


echo > $tld.ns
for i in `cat $tld`;
  do
  echo "Checking $i..."
  if [ $domfilter -eq 1 ]; then
      dig @`get_tldns $i` $i NS $digopts | grep NS | grep -iv $filter_domain'\.$' >> $tld.ns
  else
      dig @`get_tldns $i` $i NS $digopts | grep NS >> $tld.ns
  fi
done