| 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
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
- data OpenFileFlags = OpenFileFlags {}
- defaultFileFlags :: OpenFileFlags
- openFd :: FilePath -> OpenMode -> OpenFileFlags -> IO Fd
- openFdAt :: Maybe Fd -> FilePath -> OpenMode -> OpenFileFlags -> IO Fd
- createFile :: FilePath -> FileMode -> IO Fd
- createFileAt :: Maybe Fd -> 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
- queryFdOption :: Fd -> FdOption -> IO Bool
- setFdOption :: Fd -> FdOption -> Bool -> IO ()
- type FileLock = (LockRequest, SeekMode, FileOffset, FileOffset)
- data LockRequest
- 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
Opening and closing files
data OpenFileFlags Source #
Correspond to some of the int flags from C's fcntl.h.
Constructors
| OpenFileFlags | |
Fields
| |
Instances
| Read OpenFileFlags Source # | |
Defined in System.Posix.IO.Common Methods readsPrec :: Int -> ReadS OpenFileFlags # readList :: ReadS [OpenFileFlags] # | |
| Show OpenFileFlags Source # | |
Defined in System.Posix.IO.Common Methods showsPrec :: Int -> OpenFileFlags -> ShowS # show :: OpenFileFlags -> String # showList :: [OpenFileFlags] -> ShowS # | |
| Eq OpenFileFlags Source # | |
Defined in System.Posix.IO.Common Methods (==) :: OpenFileFlags -> OpenFileFlags -> Bool # (/=) :: OpenFileFlags -> OpenFileFlags -> Bool # | |
| Ord OpenFileFlags Source # | |
Defined in System.Posix.IO.Common Methods compare :: OpenFileFlags -> OpenFileFlags -> Ordering # (<) :: OpenFileFlags -> OpenFileFlags -> Bool # (<=) :: OpenFileFlags -> OpenFileFlags -> Bool # (>) :: OpenFileFlags -> OpenFileFlags -> Bool # (>=) :: OpenFileFlags -> OpenFileFlags -> Bool # max :: OpenFileFlags -> OpenFileFlags -> OpenFileFlags # min :: OpenFileFlags -> OpenFileFlags -> OpenFileFlags # | |
defaultFileFlags :: OpenFileFlags Source #
Default values for the OpenFileFlags type.
Each field of OpenFileFlags is either False or Nothing
respectively.
openFd :: FilePath -> OpenMode -> OpenFileFlags -> IO Fd Source #
Open and optionally create this file. See Files
for information on how to use the FileMode type.
Arguments
| :: Maybe Fd | Optional directory file descriptor |
| -> FilePath | Pathname to open |
| -> OpenMode | Read-only, read-write or write-only |
| -> OpenFileFlags | Append, exclusive, truncate, etc. |
| -> IO Fd |
Open a file relative to an optional directory file descriptor.
Directory file descriptors can be used to avoid some race conditions when navigating changing directory trees, or to retain access to a portion of the directory tree that would otherwise become inaccessible after dropping privileges.
createFile :: FilePath -> FileMode -> IO Fd Source #
Arguments
| :: Maybe Fd | Optional directory file descriptor |
| -> FilePath | Pathname to create |
| -> FileMode | File permission bits (before umask) |
| -> IO Fd |
Create and open a file for write-only, with default flags, relative an optional directory file-descriptor.
Directory file descriptors can be used to avoid some race conditions when navigating changing directory trees, or to retain access to a portion of the directory tree that would otherwise become inaccessible after dropping privileges.
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!
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.
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
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 #
getLock :: Fd -> FileLock -> IO (Maybe (ProcessID, FileLock)) 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.
Pipes
createPipe :: IO (Fd, Fd) Source #
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.
Duplicating file descriptors
Converting file descriptors to/from Handles
handleToFd :: Handle -> IO Fd Source #
Extracts the Fd from a Handle. This function has the side effect
of closing the Handle (and flushing its write buffer, if necessary),
without closing the underlying Fd.
Warning: This means you take over ownership of the underlying Fd.
hClose on the Handle will no longer have any effect.
This will break common patterns to avoid file descriptor leaks,
such as using hClose in the cleanup action of Control.Exception.bracket,
making it a silent no-op.
Be sure to close the returned Fd yourself to not leak it.