Comment by eutectic

And in Haskell (feel free to include this):

    import Control.Concurrent (threadDelay)                                         
    import System.IO

    main :: IO ()                                                                   
    main = withFile "/sys/class/leds/beaglebone:green:usr0/brightness" AppendMode go
      where put h s = hPutStrLn h s >> threadDelay 2000000                          
            go  h   = let m = put h "0" >> put h "1" >> m in m