LookupDNS.hs

-- stack ghci --package dns --package bytestring

-- import Network.DNS.Resolver 
-- import Network.DNS.Lookup 
-- import qualified Data.ByteString.Char8 as BSC

-- reads newline separated domain names and dumps their A records to an output file.

readFile "/tmp/domains.txt" 
    >>= return . map BSC.pack . lines  
    >>= \domains -> mapM (\d -> withResolver seed (\s -> lookupA s d >>= return . (,) d )) domains 
    >>= \ts -> writeFile "/tmp/resolv.txt" $ unlines . map show $ ts
    
-- beware of very large files!