import Data.List
import System.Directory
import System.Posix.Files as PF
import Text.Printf
 
data StMode
    = BlkDev
    | CharDev
    | Dir
    | NamedPipe
    | RegFile
    | Sock
    | SymLink
    deriving (Eq, Ord)
 
instance Show StMode where
    show BlkDev = "block device"
    show CharDev = "character device"
    show Dir = "directory"
    show NamedPipe = "named pipe"
    show RegFile = "regular file"
    show Sock = "socket"
    show SymLink = "symbolic link"
 
getStMode :: FilePath -> IO StMode
getStMode fp =
    getSymbolicLinkStatus fp >>=
    (\x ->
         case () of
             _
                 | isBlockDevice x -> return BlkDev
                 | isCharacterDevice x -> return CharDev
                 | isNamedPipe x -> return NamedPipe
                 | isRegularFile x -> return RegFile
                 | isDirectory x -> return Dir
                 | PF.isSymbolicLink x -> return SymLink
                 | isSocket x -> return Sock)
 
groupByStMode :: [FilePath] -> IO [[(FilePath, StMode)]]
groupByStMode fps = do
    stModes <- mapM getStMode fps
    let zipped = zip fps stModes
        sorted = sortBy (\(_, m0) (_, m1) -> compare m0 m1) zipped
        grouped = groupBy (\(_, m0) (_, m1) -> m0 == m1) sorted
    return grouped
 
ls :: FilePath -> IO [FilePath]
ls fp = listDirectory fp >>= (\list -> return $ map ((fp ++ "/") ++) list)
 
main =
    ls "/proc" >>= groupByStMode >>=
    mapM_
        (\list ->
             let (toShow, toHide) = splitAt 10 list
              in printf "%-30s%s\n" "path" "type" >>
                 mapM_ (\x -> printf "%-30s%s\n" (fst x) (show $ snd x)) toShow >>
                 printf "%-30s%s" (show $ length toHide) "omited\n\n")
 

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