For GT NS6262 class, a script to get IP addresses from hostnames

lookup.rb

require 'resolv'
filename = ARGV[0]
batch_size = ARGV[1].to_i
outfile = File.open('ip-addresses.txt','w+')
domains = File.readlines(filename)
groups = domains.each_slice(batch_size)

threads = []
results = []
groups.each_with_index do |group,index|
  threads << Thread.new do
    result = group.map do |domain|
      begin
        ip = Resolv.getaddress(domain.chomp)
	ip.include?(":") ? nil : ip
      rescue
        nil
      end
    end
    results[index] = result
  end
end
threads.each(&:join)

results.each do |batch|
  batch.each do |ip|
    outfile.puts ip
  end
end

outfile.close

# To call from the command line on the class provided VM, with timing:
# time ruby lookup.rb <input file> <batch size>
# The first argument is the filename you want to scan
# The second argument is how many hosts each thread should scan
# Example:
# time ruby lookup.rb joe1-top-1ht.txt 100