examples/FileIO.hs · streamly

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1import qualified Streamly.Prelude as S

2import qualified Streamly.Fold as FL

3import qualified Streamly.Mem.Array as A

4import qualified Streamly.FileSystem.File as File

6import Data.Char (ord)

7import System.Environment (getArgs)

9cat :: FilePath -> IO ()

10cat src = File.writeArrays "/dev/stdout" $ File.readArraysUpto (256*1024) src

12cp :: FilePath -> FilePath -> IO ()

13cp src dst = File.writeArrays dst $ File.readArraysUpto (256*1024) src

15ord' :: Num a => Char -> a

16ord' = (fromIntegral . ord)

18wcl :: FilePath -> IO ()

19wcl src = print =<< (S.length

20 $ FL.splitSuffixBy (== ord' '\n') FL.drain

21 $ File.read src)

23grepc :: String -> FilePath -> IO ()

24grepc pat src = print . (subtract 1) =<< (S.length

25 $ FL.splitOn (A.fromList (map ord' pat)) FL.drain

26 $ File.read src)

28avgll :: FilePath -> IO ()

29avgll src = print =<< (FL.foldl' avg

30 $ FL.splitSuffixBy (== ord' '\n') FL.length

31 $ File.read src)

32 where avg = (/) <$> toDouble FL.sum <*> toDouble FL.length

33 toDouble = fmap (fromIntegral :: Int -> Double)

35llhisto :: FilePath -> IO ()

36llhisto src = print =<< (FL.foldl' (FL.classify FL.length)

37 $ S.map bucket

38 $ FL.splitSuffixBy (== ord' '\n') FL.length

39 $ File.read src)

40 where

41 bucket n = let i = n `div` 10 in if i > 9 then (9,n) else (i,n)

43main :: IO ()

44main = do

45 src <- fmap head getArgs

47 putStrLn "cat" >> cat src -- Unix cat program

48 putStr "wcl " >> wcl src -- Unix wc -l program

49 putStr "grepc " >> grepc "aaaa" src -- Unix grep -c program

50 putStr "avgll " >> avgll src -- get average line length

51 putStr "llhisto " >> llhisto src -- get line length histogram

52 putStr "cp " >> cp src "dst-xyz.txt" -- Unix cp program