unix-2.8.5.1: POSIX functionality
Copyright(c) The University of Glasgow 2002
LicenseBSD-style (see the file libraries/base/LICENSE)
Maintainerlibraries@haskell.org
Stabilityprovisional
Portabilitynon-portable (requires POSIX)
Safe HaskellSafe
LanguageHaskell2010

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

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

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.

openFdAt Source #

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 #

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

createFileAt 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!

fdRead Source #

Arguments

:: Fd 
-> ByteCount

How many bytes to read

-> IO (String, ByteCount)

The bytes read, how many bytes were read.

Deprecated: This function is scheduled to be dropped in favor of fdRead, because decoding e.g. UTF-8 streams partially is unsafe.

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

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.

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

dup :: Fd -> IO Fd Source #

May throw an exception if this is an invalid descriptor.

dupTo :: Fd -> Fd -> IO Fd Source #

May throw an exception if this is an invalid descriptor.

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.

fdToHandle :: Fd -> IO Handle Source #

Converts an Fd into a Handle that can be used with the standard Haskell IO library (see System.IO).