ShowIP.hs

import System.Environment
import Control.Exception
import Control.Monad
import Network.Socket

main = do
  args <- getArgs
  case args of
    [host] -> catch (displayIPs host) $ \e -> do
                let err = show (e :: IOException)
                putStrLn $ "couldn't look up host " ++ host ++ " (" ++ err ++ ")"
    _ -> fail "usage: ShowIP <hostname>"

displayIPs :: String -> IO ()
displayIPs host = do
  let query = defaultHints { addrFamily = AF_INET, addrSocketType = Stream }
  infos <- getAddrInfo (Just query) (Just host) Nothing
  forM_ infos (putStrLn . show)