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|
-- !!! Reconfiguring the buffering of a handle
module Main(main) where
import System.IO
queryBuffering :: String -> Handle -> IO ()
queryBuffering handle_nm handle = do
bufm <- hGetBuffering handle
putStrLn ("Buffering for " ++ handle_nm ++ " is: " ++ show bufm)
main = do
queryBuffering "stdin" stdin
queryBuffering "stdout" stdout
queryBuffering "stderr" stderr
-- twiddling the setting for stdin.
hSetBuffering stdin NoBuffering
queryBuffering "stdin" stdin
hSetBuffering stdin LineBuffering
queryBuffering "stdin" stdin
hSetBuffering stdin (BlockBuffering (Just 2))
queryBuffering "stdin" stdin
hSetBuffering stdin (BlockBuffering Nothing)
queryBuffering "stdin" stdin
let bmo = BlockBuffering (Just (-3))
hSetBuffering stdin bmo `catch` \ _ -> putStrLn ("Caught illegal op: hSetBuffering stdin " ++ showParen True (showsPrec 9 bmo) [])
putChar '\n'
-- twiddling the buffering for stdout
hPutStr stdout "Hello stdout 1"
hSetBuffering stdout NoBuffering
queryBuffering "stdout" stdout
hPutStr stdout "Hello stdout 2"
hSetBuffering stdout LineBuffering
queryBuffering "stdout" stdout
hPutStr stdout "Hello stdout 3"
hSetBuffering stdout (BlockBuffering (Just 2))
queryBuffering "stdout" stdout
hPutStr stdout "Hello stdout 4"
hSetBuffering stdout (BlockBuffering Nothing)
queryBuffering "stdout" stdout
hPutStr stdout "Hello stdout 5"
let bmo = BlockBuffering (Just (-3))
hSetBuffering stdout bmo `catch` \ _ -> putStrLn ("Caught illegal op: hSetBuffering stdout " ++ showParen True (showsPrec 9 bmo) [])
putChar '\n'
-- twiddling the buffering for stderr
hPutStr stderr "Hello stderr 1"
hSetBuffering stderr NoBuffering
queryBuffering "stderr" stderr
hPutStr stderr "Hello stderr 2"
hSetBuffering stderr LineBuffering
queryBuffering "stderr" stderr
hPutStr stderr "Hello stderr 3"
hSetBuffering stderr (BlockBuffering (Just 2))
queryBuffering "stderr" stderr
hPutStr stderr "Hello stderr 4"
hSetBuffering stderr (BlockBuffering Nothing)
queryBuffering "stderr" stderr
hPutStr stderr "Hello stderr 5"
let bmo = BlockBuffering (Just (-3))
hSetBuffering stderr bmo `catch` \ _ -> putStrLn ("Caught illegal op: hSetBuffering stderr " ++ showParen True (showsPrec 9 bmo) [])
ls <- hGetContents stdin
ls' <- putLine ls
hSetBuffering stdin NoBuffering
putLine ls'
return ()
putLine :: String -> IO String
putLine [] = return []
putLine (x:xs) = do
putChar x
case x of
'\n' -> return xs
_ -> putLine xs
|
