Copyright	(c) The University of Glasgow 2002
License	BSD-style (see the file libraries/base/LICENSE)
Maintainer	libraries@haskell.org
Stability	provisional
Portability	non-portable (requires POSIX)
Safe Haskell	Safe
Language	Haskell2010

System.Posix.IO

Contents

Input / Output

Description

POSIX IO support. These types and functions correspond to the unix functions open(2), close(2), etc. For more portable functions which are more like fopen(3) and friends from stdio.h, see System.IO .

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
fdReadBuf :: Fd -> Ptr Word8 -> ByteCount -> IO ByteCount
fdWriteBuf :: Fd -> Ptr Word8 -> ByteCount -> 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 Source #

stdOutput :: Fd Source #

stdError :: Fd Source #

Opening and closing files

data OpenMode Source #

Constructors

ReadOnly
WriteOnly
ReadWrite

data OpenFileFlags Source #

Correspond to some of the int flags from C's fcntl.h.

Constructors

OpenFileFlags
Fields append :: Bool O_APPEND exclusive :: Bool O_EXCL noctty :: Bool O_NOCTTY nonBlock :: Bool O_NONBLOCK trunc :: Bool O_TRUNC

defaultFileFlags :: OpenFileFlags Source #

Default values for the OpenFileFlags type. False for each of append, exclusive, noctty, nonBlock, and trunc.

openFd Source #

Arguments

:: FilePath
-> OpenMode
-> Maybe FileMode	Just x => creates the file with the given modes, Nothing => the file must exist.
-> OpenFileFlags
-> IO Fd

Open and optionally create this file. See Files for information on how to use the FileMode type.

createFile :: FilePath -> FileMode -> IO Fd Source #

Create and open this file in WriteOnly mode. A special case of openFd . See Files for information on how to use the FileMode type.

closeFd :: Fd -> IO () Source #

Close this file descriptor. May throw an exception if this is an invalid descriptor.

Reading/writing data

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

fdRead Source #

Arguments

:: Fd
-> ByteCount	How many bytes to read
-> IO ( String , ByteCount )	The bytes read, how many bytes were read.

Read data from an Fd and convert it to a String using the locale encoding. Throws an exception if this is an invalid descriptor, or EOF has been reached.

fdWrite :: Fd -> String -> IO ByteCount Source #

Write a String to an Fd using the locale encoding.

fdReadBuf Source #

Arguments

:: Fd
-> Ptr Word8	Memory in which to put the data
-> ByteCount	Maximum number of bytes to read
-> IO ByteCount	Number of bytes read (zero for EOF)

Read data from an Fd into memory. This is exactly equivalent to the POSIX read function.

fdWriteBuf Source #

Arguments

:: Fd
-> Ptr Word8	Memory containing the data to write
-> ByteCount	Maximum number of bytes to write
-> IO ByteCount	Number of bytes written

Write data from memory to an Fd . This is exactly equivalent to the POSIX write function.

Seeking

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

May throw an exception if this is an invalid descriptor.

File options

data FdOption Source #

Constructors

AppendOnWrite	O_APPEND
CloseOnExec	FD_CLOEXEC
NonBlockingRead	O_NONBLOCK
SynchronousWrites	O_SYNC

queryFdOption :: Fd -> FdOption -> IO Bool Source #

May throw an exception if this is an invalid descriptor.

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

May throw an exception if this is an invalid descriptor.

Locking

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

data LockRequest Source #

Constructors

ReadLock
WriteLock
Unlock

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

May throw an exception if this is an invalid descriptor.

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

May throw an exception if this is an invalid descriptor.

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

May throw an exception if this is an invalid descriptor.

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. May throw an exception if this is an invalid descriptor.