base-4.17.0.0: Basic libraries
Copyright(c) The University of Glasgow 1994-2008
Licensesee libraries/base/LICENSE
Maintainerlibraries@haskell.org
Stabilityinternal
Portabilitynon-portable
Safe HaskellTrustworthy
LanguageHaskell2010

GHC.IO.FD

Description

Raw read/write operations on file descriptors

Synopsis

Documentation

data FD Source #

Constructors

FD 

Fields

Instances

Instances details
BufferedIO FD Source #

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.FD

IODevice FD Source #

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.FD

RawIO FD Source #

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.FD

Show FD Source #

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.FD

openFileWith Source #

Arguments

:: FilePath

file to open

-> IOMode

mode in which to open the file

-> Bool

open the file in non-blocking mode?

-> (FD -> IODeviceType -> IO r)

act1: An action to perform on the file descriptor with the masking state restored and an exception handler that closes the file on exception.

-> ((forall x. IO x -> IO x) -> r -> IO s)

act2: An action to perform with async exceptions masked and no exception handler.

-> IO s 

Open a file and make an FD for it. Truncates the file to zero size when the IOMode is WriteMode.

openFileWith takes two actions, act1 and act2, to perform after opening the file.

act1 is passed a file descriptor and I/O device type for the newly opened file. If an exception occurs in act1, then the file will be closed. act1 must not close the file itself. If it does so and then receives an exception, then the exception handler will attempt to close it again, which is impermissible.

act2 is performed with asynchronous exceptions masked. It is passed a function to restore the masking state and the result of act1. It /must not/ throw an exception (or deliver one via an interruptible operation) without first closing the file or arranging for it to be closed. act2 may close the file, but is not required to do so. If act2 leaves the file open, then the file will remain open on return from openFileWith.

Code calling openFileWith that wishes to install a finalizer to close the file should do so in act2. Doing so in act1 could potentially close the file in the finalizer first and then in the exception handler. See openFile' for an example of this use. Regardless, the caller is responsible for ensuring that the file is eventually closed, perhaps using bracket.

openFile Source #

Arguments

:: FilePath

file to open

-> IOMode

mode in which to open the file

-> Bool

open the file in non-blocking mode?

-> IO (FD, IODeviceType) 

Open a file and make an FD for it. Truncates the file to zero size when the IOMode is WriteMode. This function is difficult to use without potentially leaking the file descriptor on exception. In particular, it must be used with exceptions masked, which is a bit rude because the thread will be uninterruptible while the file path is being encoded. Use openFileWith instead.

mkFD Source #

Arguments

:: CInt 
-> IOMode 
-> Maybe (IODeviceType, CDev, CIno) 
-> Bool

is a socket (on Windows)

-> Bool

is in non-blocking mode on Unix

-> IO (FD, IODeviceType) 

Make a FD from an existing file descriptor. Fails if the FD refers to a directory. If the FD refers to a file, mkFD locks the file according to the Haskell 2010 single writer/multiple reader locking semantics (this is why we need the IOMode argument too).

release :: FD -> IO () Source #