Copyright | (c) The University of Glasgow 1994-2008 |
---|---|
License | see libraries/base/LICENSE |
Maintainer | libraries@haskell.org |
Stability | internal |
Portability | non-portable |
Safe Haskell | Trustworthy |
Language | Haskell2010 |
Handle operations implemented by file descriptors (FDs)
Synopsis
- stdin :: Handle
- stdout :: Handle
- stderr :: Handle
- openFile :: FilePath -> IOMode -> IO Handle
- openBinaryFile :: FilePath -> IOMode -> IO Handle
- openFileBlocking :: FilePath -> IOMode -> IO Handle
- mkHandleFromFD :: FD -> IODeviceType -> FilePath -> IOMode -> Bool -> Maybe TextEncoding -> IO Handle
- fdToHandle :: FD -> IO Handle
- fdToHandle' :: CInt -> Maybe IODeviceType -> Bool -> FilePath -> IOMode -> Bool -> IO Handle
- handleToFd :: Handle -> IO FD
Documentation
openFile :: FilePath -> IOMode -> IO Handle Source #
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 (on POSIX systems) is a FIFO without a reader andWriteMode
was requested; orisPermissionError
if the user does not have permission to open the file.
Note: if you will be working with files containing binary data, you'll want to
be using openBinaryFile
.
openBinaryFile :: FilePath -> IOMode -> IO Handle Source #
Like openFile
, but open the file in binary mode.
On Windows, reading a file in text mode (which is the default)
will translate CRLF to LF, and writing will translate LF to CRLF.
This is usually what you want with text files. With binary files
this is undesirable; also, as usual under Microsoft operating systems,
text mode treats control-Z as EOF. Binary mode turns off all special
treatment of end-of-line and end-of-file characters.
(See also hSetBinaryMode
.)
openFileBlocking :: FilePath -> IOMode -> IO Handle Source #
Like openFile
, but opens the file in ordinary blocking mode.
This can be useful for opening a FIFO for writing: if we open in
non-blocking mode then the open will fail if there are no readers,
whereas a blocking open will block until a reader appear.
Since: 4.4.0.0
mkHandleFromFD :: FD -> IODeviceType -> FilePath -> IOMode -> Bool -> Maybe TextEncoding -> IO Handle Source #
fdToHandle :: FD -> IO Handle Source #
Turn an existing file descriptor into a Handle. This is used by various external libraries to make Handles.
Makes a binary Handle. This is for historical reasons; it should probably be a text Handle with the default encoding and newline translation instead.