X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=System%2FIO.hs;h=f33a167bde470fc98dde647bff36f6cde4152d4d;hb=b8ac498face4c8b16c06d30fbc86666b7dc28173;hp=1226fcc50ea16a3866da34c2b8f1c7496dd9a7f4;hpb=bb02d065adafd2366048fbbe28c42e02ebc0a1c0;p=ghc-base.git diff --git a/System/IO.hs b/System/IO.hs index 1226fcc..f33a167 100644 --- a/System/IO.hs +++ b/System/IO.hs @@ -6,7 +6,7 @@ -- License : BSD-style (see the file libraries/base/LICENSE) -- -- Maintainer : libraries@haskell.org --- Stability : provisional +-- Stability : stable -- Portability : portable -- -- The standard IO library. @@ -14,66 +14,121 @@ ----------------------------------------------------------------------------- module System.IO ( + -- * The IO monad + + IO, -- instance MonadFix + fixIO, -- :: (a -> IO a) -> IO a + + -- * Files and handles + + FilePath, -- :: String + Handle, -- abstract, instance of: Eq, Show. - HandlePosn(..), -- abstract, instance of: Eq, Show. - IOMode(ReadMode,WriteMode,AppendMode,ReadWriteMode), - BufferMode(NoBuffering,LineBuffering,BlockBuffering), - SeekMode(AbsoluteSeek,RelativeSeek,SeekFromEnd), + -- ** Standard handles + + -- | Three handles are allocated during program initialisation, + -- and are initially open. stdin, stdout, stderr, -- :: Handle + -- * Opening and closing files + + -- ** Opening files + openFile, -- :: FilePath -> IOMode -> IO Handle + IOMode(ReadMode,WriteMode,AppendMode,ReadWriteMode), + + -- ** Closing files + hClose, -- :: Handle -> IO () + + -- ** Special cases + + -- | These functions are also exported by the "Prelude". + + readFile, -- :: FilePath -> IO String + writeFile, -- :: FilePath -> String -> IO () + appendFile, -- :: FilePath -> String -> IO () + + -- ** File locking + + -- $locking + + -- * Operations on handles + + -- ** Determining the size of a file + hFileSize, -- :: Handle -> IO Integer + + -- ** Detecting the end of input + hIsEOF, -- :: Handle -> IO Bool isEOF, -- :: IO Bool + -- ** Buffering operations + + BufferMode(NoBuffering,LineBuffering,BlockBuffering), hSetBuffering, -- :: Handle -> BufferMode -> IO () hGetBuffering, -- :: Handle -> IO BufferMode hFlush, -- :: Handle -> IO () + + -- ** Repositioning handles + hGetPosn, -- :: Handle -> IO HandlePosn hSetPosn, -- :: HandlePosn -> IO () + HandlePosn, -- abstract, instance of: Eq, Show. + hSeek, -- :: Handle -> SeekMode -> Integer -> IO () + SeekMode(AbsoluteSeek,RelativeSeek,SeekFromEnd), +#if !defined(__NHC__) hTell, -- :: Handle -> IO Integer +#endif + + -- ** Handle properties + + hIsOpen, hIsClosed, -- :: Handle -> IO Bool + hIsReadable, hIsWritable, -- :: Handle -> IO Bool + hIsSeekable, -- :: Handle -> IO Bool + + -- ** Terminal operations + +#if !defined(__HUGS__) && !defined(__NHC__) + hIsTerminalDevice, -- :: Handle -> IO Bool + + hSetEcho, -- :: Handle -> Bool -> IO () + hGetEcho, -- :: Handle -> IO Bool +#endif + + -- ** Showing handle state + +#ifdef __GLASGOW_HASKELL__ + hShow, -- :: Handle -> IO String +#endif + + -- * Text input and output + + -- ** Text input + hWaitForInput, -- :: Handle -> Int -> IO Bool hReady, -- :: Handle -> IO Bool hGetChar, -- :: Handle -> IO Char hGetLine, -- :: Handle -> IO [Char] hLookAhead, -- :: Handle -> IO Char hGetContents, -- :: Handle -> IO [Char] + + -- ** Text output + hPutChar, -- :: Handle -> Char -> IO () hPutStr, -- :: Handle -> [Char] -> IO () hPutStrLn, -- :: Handle -> [Char] -> IO () hPrint, -- :: Show a => Handle -> a -> IO () - hIsOpen, hIsClosed, -- :: Handle -> IO Bool - hIsReadable, hIsWritable, -- :: Handle -> IO Bool - hIsSeekable, -- :: Handle -> IO Bool - isAlreadyExistsError, isDoesNotExistError, -- :: IOError -> Bool - isAlreadyInUseError, isFullError, - isEOFError, isIllegalOperation, - isPermissionError, isUserError, - - ioeGetErrorString, -- :: IOError -> String - ioeGetHandle, -- :: IOError -> Maybe Handle - ioeGetFileName, -- :: IOError -> Maybe FilePath + -- ** Special cases for standard input and output - try, -- :: IO a -> IO (Either IOError a) - bracket, -- :: IO a -> (a -> IO b) -> (a -> IO c) -> IO c - bracket_, -- :: IO a -> (a -> IO b) -> IO c -> IO c + -- | These functions are also exported by the "Prelude". - -- Non-standard extension (but will hopefully become standard with 1.5) is - -- to export the Prelude io functions via IO (in addition to exporting them - -- from the prelude...for now.) - IO, -- instance MonadFix - FilePath, -- :: String - IOError, - ioError, -- :: IOError -> IO a - userError, -- :: String -> IOError - catch, -- :: IO a -> (IOError -> IO a) -> IO a interact, -- :: (String -> String) -> IO () - putChar, -- :: Char -> IO () putStr, -- :: String -> IO () putStrLn, -- :: String -> IO () @@ -81,25 +136,24 @@ module System.IO ( getChar, -- :: IO Char getLine, -- :: IO String getContents, -- :: IO String - readFile, -- :: FilePath -> IO String - writeFile, -- :: FilePath -> String -> IO () - appendFile, -- :: FilePath -> String -> IO () readIO, -- :: Read a => String -> IO a readLn, -- :: Read a => IO a -#ifndef __HUGS__ + -- * Binary input and output + +#if !defined(__NHC__) + openBinaryFile, -- :: FilePath -> IOMode -> IO Handle +#endif + +#if !defined(__HUGS__) && !defined(__NHC__) + hSetBinaryMode, -- :: Handle -> Bool -> IO () hPutBuf, -- :: Handle -> Ptr a -> Int -> IO () hGetBuf, -- :: Handle -> Ptr a -> Int -> IO Int + hPutBufNonBlocking, -- :: Handle -> Ptr a -> Int -> IO Int + hGetBufNonBlocking, -- :: Handle -> Ptr a -> Int -> IO Int #endif - - fixIO, -- :: (a -> IO a) -> IO a - -#ifndef __HUGS__ - hSetEcho, -- :: Handle -> Bool -> IO () - hGetEcho, -- :: Handle -> IO Bool - hIsTerminalDevice, -- :: Handle -> IO Bool -#endif + module System.IO.Error, ) where #ifdef __GLASGOW_HASKELL__ @@ -119,59 +173,166 @@ import Hugs.IO import Hugs.IOExts #endif -import System.IO.Error +#ifdef __NHC__ +import IO + ( Handle () + , HandlePosn () + , IOMode (ReadMode,WriteMode,AppendMode,ReadWriteMode) + , BufferMode (NoBuffering,LineBuffering,BlockBuffering) + , SeekMode (AbsoluteSeek,RelativeSeek,SeekFromEnd) + , stdin, stdout, stderr + , openFile -- :: FilePath -> IOMode -> IO Handle + , hClose -- :: Handle -> IO () + , hFileSize -- :: Handle -> IO Integer + , hIsEOF -- :: Handle -> IO Bool + , isEOF -- :: IO Bool + , hSetBuffering -- :: Handle -> BufferMode -> IO () + , hGetBuffering -- :: Handle -> IO BufferMode + , hFlush -- :: Handle -> IO () + , hGetPosn -- :: Handle -> IO HandlePosn + , hSetPosn -- :: HandlePosn -> IO () + , hSeek -- :: Handle -> SeekMode -> Integer -> IO () + , hWaitForInput -- :: Handle -> Int -> IO Bool + , hGetChar -- :: Handle -> IO Char + , hGetLine -- :: Handle -> IO [Char] + , hLookAhead -- :: Handle -> IO Char + , hGetContents -- :: Handle -> IO [Char] + , hPutChar -- :: Handle -> Char -> IO () + , hPutStr -- :: Handle -> [Char] -> IO () + , hIsOpen, hIsClosed -- :: Handle -> IO Bool + , hIsReadable, hIsWritable -- :: Handle -> IO Bool + , hIsSeekable -- :: Handle -> IO Bool + + , IO () + , FilePath -- :: String + ) +import NHC.IOExtras (fixIO) +#endif + +import System.IO.Error ( + isAlreadyExistsError, isDoesNotExistError, -- :: IOError -> Bool + isAlreadyInUseError, isFullError, + isEOFError, isIllegalOperation, + isPermissionError, isUserError, + + ioeGetErrorString, -- :: IOError -> String + ioeGetHandle, -- :: IOError -> Maybe Handle + ioeGetFileName, -- :: IOError -> Maybe FilePath + + try, -- :: IO a -> IO (Either IOError a) + + -- re-exports of Prelude names + IOError, + ioError, -- :: IOError -> IO a + userError, -- :: String -> IOError + catch -- :: IO a -> (IOError -> IO a) -> IO a + ) -- ----------------------------------------------------------------------------- -- Standard IO #ifndef __HUGS__ +-- | Write a character to the standard output device +-- (same as 'hPutChar' 'stdout'). + putChar :: Char -> IO () putChar c = hPutChar stdout c +-- | Write a string to the standard output device +-- (same as 'hPutStr' 'stdout'). + putStr :: String -> IO () putStr s = hPutStr stdout s +-- | The same as 'putStrLn', but adds a newline character. + putStrLn :: String -> IO () putStrLn s = do putStr s putChar '\n' +-- | The 'print' function outputs a value of any printable type to the +-- standard output device. +-- Printable types are those that are instances of class 'Show'; 'print' +-- converts values to strings for output using the 'show' operation and +-- adds a newline. +-- +-- For example, a program to print the first 20 integers and their +-- powers of 2 could be written as: +-- +-- > main = print ([(n, 2^n) | n <- [0..19]]) + print :: Show a => a -> IO () print x = putStrLn (show x) +-- | Read a character from the standard input device +-- (same as 'hGetChar' 'stdin'). + getChar :: IO Char getChar = hGetChar stdin +-- | Read a line from the standard input device +-- (same as 'hGetLine' 'stdin'). + getLine :: IO String getLine = hGetLine stdin +-- | The 'getContents' operation returns all user input as a single string, +-- which is read lazily as it is needed +-- (same as 'hGetContents' 'stdin'). + getContents :: IO String getContents = hGetContents stdin +-- | The 'interact' function takes a function of type @String->String@ +-- as its argument. The entire input from the standard input device is +-- passed to this function as its argument, and the resulting string is +-- output on the standard output device. + interact :: (String -> String) -> IO () interact f = do s <- getContents putStr (f s) +-- | The 'readFile' function reads a file and +-- returns the contents of the file as a string. +-- The file is read lazily, on demand, as with 'getContents'. + readFile :: FilePath -> IO String readFile name = openFile name ReadMode >>= hGetContents +-- | The computation 'writeFile' @file str@ function writes the string @str@, +-- to the file @file@. + writeFile :: FilePath -> String -> IO () writeFile name str = do hdl <- openFile name WriteMode hPutStr hdl str hClose hdl +-- | The computation 'appendFile' @file str@ function appends the string @str@, +-- to the file @file@. +-- +-- Note that 'writeFile' and 'appendFile' write a literal string +-- to a file. To write a value of any printable type, as with 'print', +-- use the 'show' function to convert the value to a string first. +-- +-- > main = appendFile "squares" (show [(x,x*x) | x <- [0,0.1..2]]) + appendFile :: FilePath -> String -> IO () appendFile name str = do hdl <- openFile name AppendMode hPutStr hdl str hClose hdl +-- | The 'readLn' function combines 'getLine' and 'readIO'. + readLn :: Read a => IO a readLn = do l <- getLine r <- readIO l return r --- raises an exception instead of an error +-- | The 'readIO' function is similar to 'read' except that it signals +-- parse failure to the 'IO' monad instead of terminating the program. + readIO :: Read a => String -> IO a readIO s = case (do { (x,t) <- reads s ; ("","") <- lex t ; @@ -181,14 +342,33 @@ readIO s = case (do { (x,t) <- reads s ; _ -> ioError (userError "Prelude.readIO: ambiguous parse") #endif /* __HUGS__ */ +-- | Computation 'hReady' @hdl@ indicates whether at least one item is +-- available for input from handle @hdl@. +-- +-- This operation may fail with: +-- +-- * 'isEOFError' if the end of file has been reached. + hReady :: Handle -> IO Bool hReady h = hWaitForInput h 0 +-- | The same as 'hPutStr', but adds a newline character. + hPutStrLn :: Handle -> String -> IO () hPutStrLn hndl str = do hPutStr hndl str hPutChar hndl '\n' +-- | Computation 'hPrint' @hdl t@ writes the string representation of @t@ +-- given by the 'shows' function to the file or channel managed by @hdl@ +-- and appends a newline. +-- +-- This operation may fail with: +-- +-- * 'isFullError' if the device is full; or +-- +-- * 'isPermissionError' if another system resource limit would be exceeded. + hPrint :: Show a => Handle -> a -> IO () hPrint hdl = hPutStrLn hdl . show @@ -199,3 +379,22 @@ hPrint hdl = hPutStrLn hdl . show fixIO :: (a -> IO a) -> IO a fixIO m = stToIO (fixST (ioToST . m)) #endif + +-- $locking +-- Implementations should enforce as far as possible, at least locally to the +-- Haskell process, multiple-reader single-writer locking on files. +-- That is, /there may either be many handles on the same file which manage +-- input, or just one handle on the file which manages output/. If any +-- open or semi-closed handle is managing a file for output, no new +-- handle can be allocated for that file. If any open or semi-closed +-- handle is managing a file for input, new handles can only be allocated +-- if they do not manage output. Whether two files are the same is +-- implementation-dependent, but they should normally be the same if they +-- have the same absolute path name and neither has been renamed, for +-- example. +-- +-- /Warning/: the 'readFile' operation holds a semi-closed handle on +-- the file until the entire contents of the file have been consumed. +-- It follows that an attempt to write to a file (using 'writeFile', for +-- example) that was earlier opened by 'readFile' will usually result in +-- failure with 'isAlreadyInUseError'.