--- /dev/null
+--!!! Testing IO.hFileSize
+module Main(main) where
+
+import IO
+import Directory ( removeFile )
+
+main = do
+ sz <- hFileSize stdin `catch` (\ _ -> return (-1))
+ print sz
+ let fn = "io025.out"
+ hdl <- openFile fn WriteMode
+ removeFile fn
+ hPutStrLn hdl "file_size"
+ -- with default buffering
+ sz <- hFileSize hdl
+ print sz
+
+ hSetBuffering hdl NoBuffering
+ hPutStrLn hdl "file_size"
+ -- with no buffering
+ sz <- hFileSize hdl
+ print sz
+ hSetBuffering hdl LineBuffering
+ hPutStrLn hdl "file_size"
+ -- with line buffering
+ sz <- hFileSize hdl
+ print sz
+ hSetBuffering hdl (BlockBuffering (Just 4))
+ -- with block buffering
+ hPutStrLn hdl "file_size"
+ sz <- hFileSize hdl
+ print sz
+ hClose hdl
--- /dev/null
+-1
+10
+20
+30
+40
--- /dev/null
+--!!! Testing EOF (and the clearing of it)
+module Main(main) where
+
+import IO
+import Directory ( removeFile )
+
+main :: IO ()
+main = do
+ hdl <- openFile "io025.hs" ReadMode
+ flg <- hIsEOF hdl
+ print flg
+ hSeek hdl SeekFromEnd 0
+ flg <- hIsEOF hdl
+ print flg
+ hSeek hdl SeekFromEnd (-1)
+ flg <- hIsEOF hdl
+ print flg
+ hGetChar hdl
+ flg <- hIsEOF hdl
+ print flg
+ hSeek hdl SeekFromEnd (-1)
+ flg <- hIsEOF hdl
+ print flg
+ hClose hdl
--- /dev/null
+False
+True
+False
+True
+False
--- /dev/null
+-- !!! isEOF
+module Main(main) where
+
+import IO ( isEOF )
+
+main = do
+ flg <- isEOF
+ print flg
+
+
--- /dev/null
+-- !!! hIsEOF (on stdout)
+module Main(main) where
+
+import IO ( hIsEOF, stdout )
+
+main = do
+ flg <- hIsEOF stdout `catch` \ _ -> putStrLn "hIsEOF failed" >> return False
+ print flg
--- /dev/null
+hIsEOF failed
+False
--- /dev/null
+-- !!! Reconfiguring the buffering of a handle
+module Main(main) where
+
+import 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
+
--- /dev/null
+Hello stderr 1Hello stderr 2Hello stderr 3Hello stderr 4Hello stderr 5
\ No newline at end of file
--- /dev/null
+Buffering for stdin is: BlockBuffering Nothing
+Buffering for stdout is: BlockBuffering Nothing
+Buffering for stderr is: NoBuffering
+Buffering for stdin is: NoBuffering
+Buffering for stdin is: LineBuffering
+Buffering for stdin is: BlockBuffering (Just 2)
+Buffering for stdin is: BlockBuffering Nothing
+Caught illegal op: hSetBuffering stdin (BlockBuffering (Just (-3)))
+
+Hello stdout 1Buffering for stdout is: NoBuffering
+Hello stdout 2Buffering for stdout is: LineBuffering
+Hello stdout 3Buffering for stdout is: BlockBuffering (Just 2)
+Hello stdout 4Buffering for stdout is: BlockBuffering Nothing
+Hello stdout 5Caught illegal op: hSetBuffering stdout (BlockBuffering (Just (-3)))
+
+Buffering for stderr is: NoBuffering
+Buffering for stderr is: LineBuffering
+Buffering for stderr is: BlockBuffering (Just 2)
+Buffering for stderr is: BlockBuffering Nothing
+Caught illegal op: hSetBuffering stderr (BlockBuffering (Just (-3)))
+-- !!! Reconfiguring the buffering of a handle
+module Main(main) where
--- /dev/null
+--!!! Flushing
+module Main(main) where
+
+import IO
+import Directory ( removeFile )
+
+main = do
+ hFlush stdin `catch` \ _ -> putStrLn "No can do - flushing read-only handles isn't legal"
+ putStr "Hello,"
+ hFlush stdout
+ putStr "Hello - "
+ hFlush stderr
+ hdl <- openFile "io029.hs" ReadMode
+ hFlush hdl `catch` \ _ -> putStrLn "No can do - flushing read-only handles isn't legal"
+ hClose hdl
+ hdl <- openFile "io029.out" WriteMode
+ removeFile "io029.out"
+ hFlush hdl
+ hClose hdl
+ hdl <- openFile "io029.out" AppendMode
+ removeFile "io029.out"
+ hFlush hdl
+ hClose hdl
+ hdl <- openFile "io029.out" ReadWriteMode
+ removeFile "io029.out"
+ hFlush hdl
+ hClose hdl
--- /dev/null
+No can do - flushing read-only handles isn't legal
+Hello,Hello - No can do - flushing read-only handles isn't legal
--- /dev/null
+--!!! file positions (hGetPosn and hSetPosn)
+module Main(main) where
+
+import IO
+import Monad ( accumulate )
+
+testPosns :: Handle -> BufferMode -> IO ()
+testPosns hdl bmo = do
+ hSetBuffering hdl bmo
+ putStrLn ("Testing positioning with buffer mode set to: " ++ show bmo)
+ testPositioning hdl
+
+bmo_ls = [NoBuffering, LineBuffering, BlockBuffering Nothing,
+ BlockBuffering (Just 511),BlockBuffering (Just 3), BlockBuffering (Just 11)]
+
+main = do
+ hdl <- openFile "io030.hs" ReadMode
+ sequence (zipWith testPosns (repeat hdl) bmo_ls)
+ hClose hdl
+
+testPositioning hdl = do
+ hSeek hdl AbsoluteSeek 0 -- go to the beginning of the file again.
+ ps <- getFilePosns 10 hdl
+ hSeek hdl AbsoluteSeek 0
+ putStr "First ten chars: "
+ ls <- hGetChars 10 hdl
+ putStrLn ls
+ -- go to the end
+ hSeek hdl SeekFromEnd 0
+ ls <- accumulate (map (\ p -> hSetPosn p >> hGetChar hdl) ps)
+ putStr "First ten chars: "
+ putStrLn ls
+
+ -- position ourselves in the middle.
+ sz <- hFileSize hdl
+ hSeek hdl AbsoluteSeek (sz `div` 2)
+ ls <- accumulate (map (\ p -> hSetPosn p >> hGetChar hdl) ps)
+ putStr "First ten chars: "
+ putStrLn ls
+
+hGetChars :: Int -> Handle -> IO String
+hGetChars n h = accumulate (replicate n (hGetChar h))
+
+getFilePosns :: Int -> Handle -> IO [HandlePosn]
+getFilePosns 0 h = return []
+getFilePosns x h = do
+ p <- hGetPosn h
+ hGetChar h
+ ps <- getFilePosns (x-1) h
+ return (p:ps)
--- /dev/null
+Testing positioning with buffer mode set to: NoBuffering
+First ten chars: --!!! file
+First ten chars: --!!! file
+First ten chars: --!!! file
+Testing positioning with buffer mode set to: LineBuffering
+First ten chars: --!!! file
+First ten chars: --!!! file
+First ten chars: --!!! file
+Testing positioning with buffer mode set to: BlockBuffering Nothing
+First ten chars: --!!! file
+First ten chars: --!!! file
+First ten chars: --!!! file
+Testing positioning with buffer mode set to: BlockBuffering (Just 511)
+First ten chars: --!!! file
+First ten chars: --!!! file
+First ten chars: --!!! file
+Testing positioning with buffer mode set to: BlockBuffering (Just 3)
+First ten chars: --!!! file
+First ten chars: --!!! file
+First ten chars: --!!! file
+Testing positioning with buffer mode set to: BlockBuffering (Just 11)
+First ten chars: --!!! file
+First ten chars: --!!! file
+First ten chars: --!!! file
projects / ghc-hetmet.git / commitdiff