{-# LANGUAGE CPP, PackageImports #-}
#if __GLASGOW_HASKELL__ >= 701
{-# LANGUAGE Safe #-}
#endif
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.
-- ** Standard handles
-- | Three handles are allocated during program initialisation,
-- and are initially open.
stdin, stdout, stderr, -- :: Handle
-- * Opening and closing files
-- ** Opening files
withFile,
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 and changing the size of a file
hFileSize, -- :: Handle -> IO Integer
hSetFileSize, -- :: Handle -> Integer -> IO ()
-- ** 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),
hTell, -- :: Handle -> IO Integer
-- ** Handle properties
-- | Each of these operations returns 'True' if the handle has the
-- the specified property, or 'False' otherwise.
hIsOpen, hIsClosed, -- :: Handle -> IO Bool
hIsReadable, hIsWritable, -- :: Handle -> IO Bool
hIsSeekable, -- :: Handle -> IO Bool
-- ** Terminal operations
hIsTerminalDevice, -- :: Handle -> IO Bool
hSetEcho, -- :: Handle -> Bool -> IO ()
hGetEcho, -- :: Handle -> IO Bool
-- ** Showing handle state
hShow, -- :: Handle -> IO String
-- * 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 ()
-- ** Special cases for standard input and output
-- | These functions are also exported by the "Prelude".
interact, -- :: (String -> String) -> IO ()
putChar, -- :: Char -> IO ()
putStr, -- :: String -> IO ()
putStrLn, -- :: String -> IO ()
print, -- :: Show a => a -> IO ()
getChar, -- :: IO Char
getLine, -- :: IO String
getContents, -- :: IO String
readIO, -- :: Read a => String -> IO a
readLn, -- :: Read a => IO a
) where
import "base" System.IO hiding (openFile, hWaitForInput)
import qualified "base" System.IO as Base
-- $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 'System.IO.Error.isAlreadyInUseError'.
-- SDM: custom verison of openFile docs removing reference to 'openBinaryFile'
-- | Computation 'openFile' @file mode@ allocates and returns a new, open
-- handle to manage the file @file@. It manages input if @mode@
-- is 'ReadMode', output if @mode@ is 'WriteMode' or 'AppendMode',
-- and both input and output if mode is 'ReadWriteMode'.
--
-- If the file does not exist and it is opened for output, it should be
-- created as a new file. If @mode@ is 'WriteMode' and the file
-- already exists, then it should be truncated to zero length.
-- Some operating systems delete empty files, so there is no guarantee
-- that the file will exist following an 'openFile' with @mode@
-- 'WriteMode' unless it is subsequently written to successfully.
-- The handle is positioned at the end of the file if @mode@ is
-- 'AppendMode', and otherwise at the beginning (in which case its
-- internal position is 0).
-- The initial buffer mode is implementation-dependent.
--
-- This operation may fail with:
--
-- * 'isAlreadyInUseError' if the file is already open and cannot be reopened;
--
-- * 'isDoesNotExistError' if the file does not exist; or
--
-- * 'isPermissionError' if the user does not have permission to open the file.
--
openFile :: FilePath -> IOMode -> IO Handle
openFile = Base.openFile
-- SDM: local version of docs for hWaitForInput, omitting GHC-specific notes.
-- If hWaitForInput finds anything in the Handle's buffer, it
-- immediately returns. If not, it tries to read from the underlying
-- OS handle. Notice that for buffered Handles connected to terminals
-- this means waiting until a complete line is available.
-- | Computation 'hWaitForInput' @hdl t@
-- waits until input is available on handle @hdl@.
-- It returns 'True' as soon as input is available on @hdl@,
-- or 'False' if no input is available within @t@ milliseconds. Note that
-- 'hWaitForInput' waits until one or more full /characters/ are available,
-- which means that it needs to do decoding, and hence may fail
-- with a decoding error.
--
-- If @t@ is less than zero, then @hWaitForInput@ waits indefinitely.
--
-- This operation may fail with:
--
-- * 'isEOFError' if the end of file has been reached.
--
-- * a decoding error, if the input begins with an invalid byte sequence
-- in this Handle's encoding.
--
hWaitForInput :: Handle -> Int -> IO Bool
hWaitForInput = Base.hWaitForInput