Haskell Core Libraries (unix package) Parent Contents Index

System.Posix.IO Portability non-portable (requires POSIX) Stability provisional Maintainer libraries@haskell.org

Contents

Input / Output Standard file descriptors Opening and closing files Reading/writing data Seeking File options Locking Pipes Duplicating file descriptors Converting file descriptors to/from Handles

Description

POSIX IO support

Synopsis

stdInput :: Fd stdOutput :: Fd stdError :: Fd data OpenMode = ReadOnly | WriteOnly | ReadWrite data OpenFileFlags = OpenFileFlags { append :: Bool exclusive :: Bool noctty :: Bool nonBlock :: Bool trunc :: Bool } defaultFileFlags :: OpenFileFlags openFd :: FilePath -> OpenMode -> Maybe FileMode -> OpenFileFlags -> IO Fd createFile :: FilePath -> FileMode -> IO Fd closeFd :: Fd -> IO () fdRead :: Fd -> ByteCount -> IO (String, ByteCount) fdWrite :: Fd -> String -> IO ByteCount fdSeek :: Fd -> SeekMode -> FileOffset -> IO FileOffset data FdOption = AppendOnWrite | CloseOnExec | NonBlockingRead | SynchronousWrites queryFdOption :: Fd -> FdOption -> IO Bool setFdOption :: Fd -> FdOption -> Bool -> IO () type FileLock = (LockRequest, SeekMode, FileOffset, FileOffset) data LockRequest = ReadLock | WriteLock | Unlock getLock :: Fd -> FileLock -> IO (Maybe (ProcessID, FileLock)) setLock :: Fd -> FileLock -> IO () waitToSetLock :: Fd -> FileLock -> IO () createPipe :: IO (Fd, Fd) dup :: Fd -> IO Fd dupTo :: Fd -> Fd -> IO Fd handleToFd :: Handle -> IO Fd fdToHandle :: Fd -> IO Handle

Input / Output

Standard file descriptors

stdInput :: Fd

stdOutput :: Fd

stdError :: Fd

Opening and closing files

data OpenMode

Constructors ReadOnly WriteOnly ReadWrite

data OpenFileFlags

Constructors OpenFileFlags append :: Bool exclusive :: Bool noctty :: Bool nonBlock :: Bool trunc :: Bool

defaultFileFlags :: OpenFileFlags

openFd :: FilePath -> OpenMode -> Maybe FileMode -> OpenFileFlags -> IO Fd

createFile :: FilePath -> FileMode -> IO Fd

closeFd :: Fd -> IO ()

Reading/writing data

Programmers using the fdRead and fdWrite API should be aware that EAGAIN exceptions may occur for non-blocking IO!

fdRead :: Fd -> ByteCount -> IO (String, ByteCount)

fdWrite :: Fd -> String -> IO ByteCount

Seeking

fdSeek :: Fd -> SeekMode -> FileOffset -> IO FileOffset

File options

data FdOption

Constructors AppendOnWrite CloseOnExec NonBlockingRead SynchronousWrites

queryFdOption :: Fd -> FdOption -> IO Bool

setFdOption :: Fd -> FdOption -> Bool -> IO ()

Locking

type FileLock = (LockRequest, SeekMode, FileOffset, FileOffset)

data LockRequest

Constructors ReadLock WriteLock Unlock

getLock :: Fd -> FileLock -> IO (Maybe (ProcessID, FileLock))

setLock :: Fd -> FileLock -> IO ()

waitToSetLock :: Fd -> FileLock -> IO ()

Pipes

createPipe :: IO (Fd, Fd)

The createPipe function creates a pair of connected file descriptors. The first component is the fd to read from, the second is the write end. Although pipes may be bidirectional, this behaviour is not portable and programmers should use two separate pipes for this purpose.

Duplicating file descriptors

dup :: Fd -> IO Fd

dupTo :: Fd -> Fd -> IO Fd

Converting file descriptors to/from Handles

handleToFd :: Handle -> IO Fd

fdToHandle :: Fd -> IO Handle

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