recvLn.hs

import qualified Data.ByteString.Char8 as B
import System.Hardware.Serialport (SerialPort, recv)

recvLn :: SerialPort -> IO B.ByteString
recvLn s = do
    -- Receive one byte at a time.
    first <- recv s 1
    rest <- if first == B.singleton '\n'
        then return $ B.empty
        else recvLn s
    -- Once the recursion finishes, we glue the parts together.
    return $ first `B.append` rest