Files.hsc

{-# OPTIONS -fffi #-}
-----------------------------------------------------------------------------
-- |
-- Module      :  System.Posix.Files
-- 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)
--
-- Functions defined by the POSIX standards for manipulating and querying the
-- file system. Names of underlying POSIX functions are indicated whenever
-- possible. A more complete documentation of the POSIX functions together
-- with a more detailed description of different error conditions are usually
-- available in the system's manual pages or from
-- <http://www.unix.org/version3/online.html> (free registration required).
--
-- When a function that calls an underlying POSIX function fails, the errno
-- code is converted to an 'IOError' using 'Foreign.C.Error.errnoToIOError'.
-- For a list of which errno codes may be generated, consult the POSIX
-- documentation for the underlying function.
--
-----------------------------------------------------------------------------

module System.Posix.Files (
    -- * File modes
    -- FileMode exported by System.Posix.Types
    unionFileModes, intersectFileModes,
    nullFileMode,
    ownerReadMode, ownerWriteMode, ownerExecuteMode, ownerModes,
    groupReadMode, groupWriteMode, groupExecuteMode, groupModes,
    otherReadMode, otherWriteMode, otherExecuteMode, otherModes,
    setUserIDMode, setGroupIDMode,
    stdFileMode,   accessModes,

    -- ** Setting file modes
    setFileMode, setFdMode, setFileCreationMask,

    -- ** Checking file existence and permissions
    fileAccess, fileExist,

    -- * File status
    FileStatus,
    -- ** Obtaining file status
    getFileStatus, getFdStatus, getSymbolicLinkStatus,
    -- ** Querying file status
    deviceID, fileID, fileMode, linkCount, fileOwner, fileGroup,
    specialDeviceID, fileSize, accessTime, modificationTime,
    statusChangeTime,
    isBlockDevice, isCharacterDevice, isNamedPipe, isRegularFile,
    isDirectory, isSymbolicLink, isSocket,

    -- * Creation
    createNamedPipe, 
    createDevice,

    -- * Hard links
    createLink, removeLink,

    -- * Symbolic links
    createSymbolicLink, readSymbolicLink,

    -- * Renaming files
    rename,

    -- * Changing file ownership
    setOwnerAndGroup,  setFdOwnerAndGroup,
#if HAVE_LCHOWN
    setSymbolicLinkOwnerAndGroup,
#endif

    -- * Changing file timestamps
    setFileTimes, touchFile,

    -- * Setting file sizes
    setFileSize, setFdSize,

    -- * Find system-specific limits for a file
    PathVar(..), getPathVar, getFdPathVar,
  ) where

#include "HsUnix.h"

import System.Posix.Error
import System.Posix.Types
import System.IO.Unsafe
import Data.Bits
import System.Posix.Internals
import Foreign
import Foreign.C

-- -----------------------------------------------------------------------------
-- POSIX file modes

-- The abstract type 'FileMode', constants and operators for
-- manipulating the file modes defined by POSIX.

-- | No permissions.
nullFileMode :: FileMode
nullFileMode = 0

-- | Owner has read permission.
ownerReadMode :: FileMode
ownerReadMode = (#const S_IRUSR)

-- | Owner has write permission.
ownerWriteMode :: FileMode
ownerWriteMode = (#const S_IWUSR)

-- | Owner has execute permission.
ownerExecuteMode :: FileMode
ownerExecuteMode = (#const S_IXUSR)

-- | Group has read permission.
groupReadMode :: FileMode
groupReadMode = (#const S_IRGRP)

-- | Group has write permission.
groupWriteMode :: FileMode
groupWriteMode = (#const S_IWGRP)

-- | Group has execute permission.
groupExecuteMode :: FileMode
groupExecuteMode = (#const S_IXGRP)

-- | Others have read permission.
otherReadMode :: FileMode
otherReadMode = (#const S_IROTH)

-- | Others have write permission.
otherWriteMode :: FileMode
otherWriteMode = (#const S_IWOTH)

-- | Others have execute permission.
otherExecuteMode :: FileMode
otherExecuteMode = (#const S_IXOTH)

-- | Set user ID on execution.
setUserIDMode :: FileMode
setUserIDMode = (#const S_ISUID)

-- | Set group ID on execution.
setGroupIDMode :: FileMode
setGroupIDMode = (#const S_ISGID)

-- | Owner, group and others have read and write permission.
stdFileMode :: FileMode
stdFileMode = ownerReadMode  .|. ownerWriteMode .|. 
	      groupReadMode  .|. groupWriteMode .|. 
	      otherReadMode  .|. otherWriteMode

-- | Owner has read, write and execute permission.
ownerModes :: FileMode
ownerModes = (#const S_IRWXU)

-- | Group has read, write and execute permission.
groupModes :: FileMode
groupModes = (#const S_IRWXG)

-- | Others have read, write and execute permission.
otherModes :: FileMode
otherModes = (#const S_IRWXO)

-- | Owner, group and others have read, write and execute permission.
accessModes :: FileMode
accessModes = ownerModes .|. groupModes .|. otherModes

-- | Combines the two file modes into one that contains modes that appear in
-- either.
unionFileModes :: FileMode -> FileMode -> FileMode
unionFileModes m1 m2 = m1 .|. m2

-- | Combines two file modes into one that only contains modes that appear in
-- both.
intersectFileModes :: FileMode -> FileMode -> FileMode
intersectFileModes m1 m2 = m1 .&. m2

-- Not exported:
fileTypeModes :: FileMode
fileTypeModes = (#const S_IFMT)

blockSpecialMode :: FileMode
blockSpecialMode = (#const S_IFBLK)

characterSpecialMode :: FileMode
characterSpecialMode = (#const S_IFCHR)

namedPipeMode :: FileMode
namedPipeMode = (#const S_IFIFO)

regularFileMode :: FileMode
regularFileMode = (#const S_IFREG)

directoryMode :: FileMode
directoryMode = (#const S_IFDIR)

symbolicLinkMode :: FileMode
symbolicLinkMode = (#const S_IFLNK)

socketMode :: FileMode
socketMode = (#const S_IFSOCK)

-- | @setFileMode path mode@ changes permission of the file given by @path@
-- to @mode@. This operation may fail with 'throwErrnoPathIfMinus1_' if @path@
-- doesn't exist or if the effective user ID of the current process is not that
-- of the file's owner.
--
-- Note: calls @chmod@.
setFileMode :: FilePath -> FileMode -> IO ()
setFileMode name m =
  withCString name $ \s -> do
    throwErrnoPathIfMinus1_ "setFileMode" name (c_chmod s m)

-- | @setFdMode fd mode@ acts like 'setFileMode' but uses a file descriptor
-- @fd@ instead of a 'FilePath'.
--
-- Note: calls @fchmod@.
setFdMode :: Fd -> FileMode -> IO ()
setFdMode fd m =
  throwErrnoIfMinus1_ "setFdMode" (c_fchmod fd m)

foreign import ccall unsafe "fchmod" 
  c_fchmod :: Fd -> CMode -> IO CInt

-- | @setFileCreationMask mode@ sets the file mode creation mask to @mode@.
-- Modes set by this operation are subtracted from files and directories upon
-- creation. The previous file creation mask is returned.
--
-- Note: calls @umask@.
setFileCreationMask :: FileMode -> IO FileMode
setFileCreationMask mask = c_umask mask

-- -----------------------------------------------------------------------------
-- access()

-- | @fileAccess name read write exec@ checks if the file (or other file system
-- object) @name@ can be accessed for reading, writing and\/or executing. To
-- check a permission set the corresponding argument to 'True'.
--
-- Note: calls @access@.
fileAccess :: FilePath -> Bool -> Bool -> Bool -> IO Bool
fileAccess name read write exec = access name flags
  where
   flags   = read_f .|. write_f .|. exec_f
   read_f  = if read  then (#const R_OK) else 0
   write_f = if write then (#const W_OK) else 0
   exec_f  = if exec  then (#const X_OK) else 0

-- | Checks for the existence of the file.
--
-- Note: calls @access@.
fileExist :: FilePath -> IO Bool
fileExist name = 
  withCString name $ \s -> do
    r <- c_access s (#const F_OK)
    if (r == 0)
	then return True
	else do err <- getErrno
	        if (err == eNOENT)
		   then return False
		   else throwErrnoPath "fileExist" name

access :: FilePath -> CMode -> IO Bool
access name flags = 
  withCString name $ \s -> do
    r <- c_access s flags
    if (r == 0)
	then return True
	else do err <- getErrno
	        if (err == eACCES)
		   then return False
		   else throwErrnoPath "fileAccess" name

-- -----------------------------------------------------------------------------
-- stat() support

-- | POSIX defines operations to get information, such as owner, permissions,
-- size and access times, about a file. This information is represented by the
-- 'FileStatus' type.
--
-- Note: see @chmod@.
newtype FileStatus = FileStatus (ForeignPtr CStat)

-- | ID of the device on which this file resides.
deviceID         :: FileStatus -> DeviceID
-- | inode number
fileID           :: FileStatus -> FileID
-- | File mode (such as permissions).
fileMode         :: FileStatus -> FileMode
-- | Number of hard links to this file.
linkCount        :: FileStatus -> LinkCount
-- | ID of owner.
fileOwner        :: FileStatus -> UserID
-- | ID of group.
fileGroup        :: FileStatus -> GroupID
-- | Describes the device that this file represents.
specialDeviceID  :: FileStatus -> DeviceID
-- | Size of the file in bytes. If this file is a symbolic link the size is
-- the length of the pathname it contains.
fileSize         :: FileStatus -> FileOffset
-- | Time of last access.
accessTime       :: FileStatus -> EpochTime
-- | Time of last modification.
modificationTime :: FileStatus -> EpochTime
-- | Time of last status change (i.e. owner, group, link count, mode, etc.).
statusChangeTime :: FileStatus -> EpochTime

deviceID (FileStatus stat) = 
  unsafePerformIO $ withForeignPtr stat $ (#peek struct stat, st_dev)
fileID (FileStatus stat) = 
  unsafePerformIO $ withForeignPtr stat $ (#peek struct stat, st_ino)
fileMode (FileStatus stat) =
  unsafePerformIO $ withForeignPtr stat $ (#peek struct stat, st_mode)
linkCount (FileStatus stat) =
  unsafePerformIO $ withForeignPtr stat $ (#peek struct stat, st_nlink)
fileOwner (FileStatus stat) =
  unsafePerformIO $ withForeignPtr stat $ (#peek struct stat, st_uid)
fileGroup (FileStatus stat) =
  unsafePerformIO $ withForeignPtr stat $ (#peek struct stat, st_gid)
specialDeviceID (FileStatus stat) =
  unsafePerformIO $ withForeignPtr stat $ (#peek struct stat, st_rdev)
fileSize (FileStatus stat) =
  unsafePerformIO $ withForeignPtr stat $ (#peek struct stat, st_size)
accessTime (FileStatus stat) =
  unsafePerformIO $ withForeignPtr stat $ (#peek struct stat, st_atime)
modificationTime (FileStatus stat) =
  unsafePerformIO $ withForeignPtr stat $ (#peek struct stat, st_mtime)
statusChangeTime (FileStatus stat) =
  unsafePerformIO $ withForeignPtr stat $ (#peek struct stat, st_ctime)

-- | Checks if this file is a block device.
isBlockDevice     :: FileStatus -> Bool
-- | Checks if this file is a character device.
isCharacterDevice :: FileStatus -> Bool
-- | Checks if this file is a named pipe device.
isNamedPipe       :: FileStatus -> Bool
-- | Checks if this file is a regular file device.
isRegularFile     :: FileStatus -> Bool
-- | Checks if this file is a directory device.
isDirectory       :: FileStatus -> Bool
-- | Checks if this file is a symbolic link device.
isSymbolicLink    :: FileStatus -> Bool
-- | Checks if this file is a socket device.
isSocket          :: FileStatus -> Bool

isBlockDevice stat = 
  (fileMode stat `intersectFileModes` fileTypeModes) == blockSpecialMode
isCharacterDevice stat = 
  (fileMode stat `intersectFileModes` fileTypeModes) == characterSpecialMode
isNamedPipe stat = 
  (fileMode stat `intersectFileModes` fileTypeModes) == namedPipeMode
isRegularFile stat = 
  (fileMode stat `intersectFileModes` fileTypeModes) == regularFileMode
isDirectory stat = 
  (fileMode stat `intersectFileModes` fileTypeModes) == directoryMode
isSymbolicLink stat = 
  (fileMode stat `intersectFileModes` fileTypeModes) == symbolicLinkMode
isSocket stat = 
  (fileMode stat `intersectFileModes` fileTypeModes) == socketMode

-- | @getFileStatus path@ calls gets the @FileStatus@ information (user ID,
-- size, access times, etc.) for the file @path@.
--
-- Note: calls @stat@.
getFileStatus :: FilePath -> IO FileStatus
getFileStatus path = do
  fp <- mallocForeignPtrBytes (#const sizeof(struct stat)) 
  withForeignPtr fp $ \p ->
    withCString path $ \s -> 
      throwErrnoPathIfMinus1_ "getFileStatus" path (c_stat s p)
  return (FileStatus fp)

-- | @getFdStatus fd@ acts as 'getFileStatus' but uses a file descriptor @fd@.
--
-- Note: calls @fstat@.
getFdStatus :: Fd -> IO FileStatus
getFdStatus (Fd fd) = do
  fp <- mallocForeignPtrBytes (#const sizeof(struct stat)) 
  withForeignPtr fp $ \p ->
    throwErrnoIfMinus1_ "getFdStatus" (c_fstat fd p)
  return (FileStatus fp)

-- | Acts as 'getFileStatus' except when the 'FilePath' refers to a symbolic
-- link. In that case the @FileStatus@ information of the symbolic link itself
-- is returned instead of that of the file it points to.
--
-- Note: calls @lstat@.
getSymbolicLinkStatus :: FilePath -> IO FileStatus
getSymbolicLinkStatus path = do
  fp <- mallocForeignPtrBytes (#const sizeof(struct stat)) 
  withForeignPtr fp $ \p ->
    withCString path $ \s -> 
      throwErrnoPathIfMinus1_ "getSymbolicLinkStatus" path (c_lstat s p)
  return (FileStatus fp)

foreign import ccall unsafe "lstat" 
  c_lstat :: CString -> Ptr CStat -> IO CInt

-- | @createNamedPipe fifo mode@  
-- creates a new named pipe, @fifo@, with permissions based on
-- @mode@. May fail with 'throwErrnoPathIfMinus1_' if a file named @name@
-- already exists or if the effective user ID of the current process doesn't
-- have permission to create the pipe.
--
-- Note: calls @mkfifo@.
createNamedPipe :: FilePath -> FileMode -> IO ()
createNamedPipe name mode = do
  withCString name $ \s -> 
    throwErrnoPathIfMinus1_ "createNamedPipe" name (c_mkfifo s mode)

-- | @createDevice path mode dev@ creates either a regular or a special file
-- depending on the value of @mode@ (and @dev@). May fail with
-- 'throwErrnoPathIfMinus1_' if a file named @name@ already exists or if the
-- effective user ID of the current process doesn't have permission to create
-- the file.
--
-- Note: calls @mknod@.
createDevice :: FilePath -> FileMode -> DeviceID -> IO ()
createDevice path mode dev =
  withCString path $ \s ->
    throwErrnoPathIfMinus1_ "createDevice" path (c_mknod s mode dev)

foreign import ccall unsafe "mknod" 
  c_mknod :: CString -> CMode -> CDev -> IO CInt

-- -----------------------------------------------------------------------------
-- Hard links

-- | @createLink old new@ creates a new path, @new@, linked to an existing file,
-- @old@.
--
-- Note: calls @link@.
createLink :: FilePath -> FilePath -> IO ()
createLink name1 name2 =
  withCString name1 $ \s1 ->
  withCString name2 $ \s2 ->
  throwErrnoPathIfMinus1_ "createLink" name1 (c_link s1 s2)

-- | @removeLink path@ removes the link named @path@.
--
-- Note: calls @unlink@.
removeLink :: FilePath -> IO ()
removeLink name =
  withCString name $ \s ->
  throwErrnoPathIfMinus1_ "removeLink" name (c_unlink s)

-- -----------------------------------------------------------------------------
-- Symbolic Links

-- | @createSymbolicLink file1 file2@ creates a symbolic link named @file2@
-- which points to the file @file1@.
--
-- Symbolic links are interpreted at run-time as if the contents of the link
-- had been substituted into the path being followed to find a file or directory.
--
-- Note: calls @symlink@.
createSymbolicLink :: FilePath -> FilePath -> IO ()
createSymbolicLink file1 file2 =
  withCString file1 $ \s1 ->
  withCString file2 $ \s2 ->
  throwErrnoPathIfMinus1_ "createSymbolicLink" file1 (c_symlink s1 s2)

foreign import ccall unsafe "symlink"
  c_symlink :: CString -> CString -> IO CInt

-- ToDo: should really use SYMLINK_MAX, but not everyone supports it yet,
-- and it seems that the intention is that SYMLINK_MAX is no larger than
-- PATH_MAX.
#if !defined(PATH_MAX)
-- PATH_MAX is not defined on systems with unlimited path length.
-- Ugly.  Fix this.
#define PATH_MAX 4096
#endif

-- | Reads the @FilePath@ pointed to by the symbolic link and returns it.
--
-- Note: calls @readlink@.
readSymbolicLink :: FilePath -> IO FilePath
readSymbolicLink file =
  allocaArray0 (#const PATH_MAX) $ \buf -> do
    withCString file $ \s -> do
      len <- throwErrnoPathIfMinus1 "readSymbolicLink" file $ 
	c_readlink s buf (#const PATH_MAX)
      peekCStringLen (buf,fromIntegral len)

foreign import ccall unsafe "readlink"
  c_readlink :: CString -> CString -> CInt -> IO CInt

-- -----------------------------------------------------------------------------
-- Renaming files

-- | @rename old new@ renames a file or directory from @old@ to @new@.
--
-- Note: calls @rename@.
rename :: FilePath -> FilePath -> IO ()
rename name1 name2 =
  withCString name1 $ \s1 ->
  withCString name2 $ \s2 ->
  throwErrnoPathIfMinus1_ "rename" name1 (c_rename s1 s2)

-- -----------------------------------------------------------------------------
-- chown()

-- | @setOwnerAndGroup path uid gid@ changes the owner and group of @path@ to
-- @uid@ and @gid@, respectively.
--
-- If @uid@ or @gid@ is specified as -1, then that ID is not changed.
--
-- Note: calls @chown@.
setOwnerAndGroup :: FilePath -> UserID -> GroupID -> IO ()
setOwnerAndGroup name uid gid = do
  withCString name $ \s ->
    throwErrnoPathIfMinus1_ "setOwnerAndGroup" name (c_chown s uid gid)

foreign import ccall unsafe "chown"
  c_chown :: CString -> CUid -> CGid -> IO CInt

-- | Acts as 'setOwnerAndGroup' but uses a file descriptor instead of a
-- 'FilePath'.
--
-- Note: calls @fchown@.
setFdOwnerAndGroup :: Fd -> UserID -> GroupID -> IO ()
setFdOwnerAndGroup (Fd fd) uid gid = 
  throwErrnoIfMinus1_ "setFdOwnerAndGroup" (c_fchown fd uid gid)

foreign import ccall unsafe "fchown"
  c_fchown :: CInt -> CUid -> CGid -> IO CInt

#if HAVE_LCHOWN
-- | Acts as 'setOwnerAndGroup' but does not follow symlinks (and thus
-- changes permissions on the link itself).
--
-- Note: calls @lchown@.
setSymbolicLinkOwnerAndGroup :: FilePath -> UserID -> GroupID -> IO ()
setSymbolicLinkOwnerAndGroup name uid gid = do
  withCString name $ \s ->
    throwErrnoPathIfMinus1_ "setSymbolicLinkOwnerAndGroup" name
	(c_lchown s uid gid)

foreign import ccall unsafe "lchown"
  c_lchown :: CString -> CUid -> CGid -> IO CInt
#endif

-- -----------------------------------------------------------------------------
-- utime()

-- | @setFileTimes path atime mtime@ sets the access and modification times
-- associated with file @path@ to @atime@ and @mtime@, respectively.
--
-- Note: calls @utime@.
setFileTimes :: FilePath -> EpochTime -> EpochTime -> IO ()
setFileTimes name atime mtime = do
  withCString name $ \s ->
   allocaBytes (#const sizeof(struct utimbuf)) $ \p -> do
     (#poke struct utimbuf, actime)  p atime
     (#poke struct utimbuf, modtime) p mtime
     throwErrnoPathIfMinus1_ "setFileTimes" name (c_utime s p)

-- | @touchFile path@ sets the access and modification times associated with
-- file @path@ to the current time.
--
-- Note: calls @utime@.
touchFile :: FilePath -> IO ()
touchFile name = do
  withCString name $ \s ->
   throwErrnoPathIfMinus1_ "touchFile" name (c_utime s nullPtr)

-- -----------------------------------------------------------------------------
-- Setting file sizes

-- | Truncates the file down to the specified length. If the file was larger
-- than the given length before this operation was performed the extra is lost.
--
-- Note: calls @truncate@.
setFileSize :: FilePath -> FileOffset -> IO ()
setFileSize file off = 
  withCString file $ \s ->
    throwErrnoPathIfMinus1_ "setFileSize" file (c_truncate s off)

foreign import ccall unsafe "truncate"
  c_truncate :: CString -> COff -> IO CInt

-- | Acts as 'setFileSize' but uses a file descriptor instead of a 'FilePath'.
--
-- Note: calls @ftruncate@.
setFdSize :: Fd -> FileOffset -> IO ()
setFdSize (Fd fd) off =
  throwErrnoIfMinus1_ "setFdSize" (c_ftruncate fd off)

-- -----------------------------------------------------------------------------
-- pathconf()/fpathconf() support

data PathVar
  = FileSizeBits		  {- _PC_FILESIZEBITS     -}
  | LinkLimit                     {- _PC_LINK_MAX         -}
  | InputLineLimit                {- _PC_MAX_CANON        -}
  | InputQueueLimit               {- _PC_MAX_INPUT        -}
  | FileNameLimit                 {- _PC_NAME_MAX         -}
  | PathNameLimit                 {- _PC_PATH_MAX         -}
  | PipeBufferLimit               {- _PC_PIPE_BUF         -}
				  -- These are described as optional in POSIX:
  				  {- _PC_ALLOC_SIZE_MIN     -}
  				  {- _PC_REC_INCR_XFER_SIZE -}
  				  {- _PC_REC_MAX_XFER_SIZE  -}
  				  {- _PC_REC_MIN_XFER_SIZE  -}
 				  {- _PC_REC_XFER_ALIGN     -}
  | SymbolicLinkLimit		  {- _PC_SYMLINK_MAX      -}
  | SetOwnerAndGroupIsRestricted  {- _PC_CHOWN_RESTRICTED -}
  | FileNamesAreNotTruncated      {- _PC_NO_TRUNC         -}
  | VDisableChar		  {- _PC_VDISABLE         -}
  | AsyncIOAvailable		  {- _PC_ASYNC_IO         -}
  | PrioIOAvailable		  {- _PC_PRIO_IO          -}
  | SyncIOAvailable		  {- _PC_SYNC_IO          -}

pathVarConst :: PathVar -> CInt
pathVarConst v = case v of
	LinkLimit     			-> (#const _PC_LINK_MAX)
	InputLineLimit			-> (#const _PC_MAX_CANON)
	InputQueueLimit			-> (#const _PC_MAX_INPUT)
	FileNameLimit			-> (#const _PC_NAME_MAX)
	PathNameLimit			-> (#const _PC_PATH_MAX)
	PipeBufferLimit			-> (#const _PC_PIPE_BUF)
	SetOwnerAndGroupIsRestricted	-> (#const _PC_CHOWN_RESTRICTED)
	FileNamesAreNotTruncated	-> (#const _PC_NO_TRUNC)
	VDisableChar			-> (#const _PC_VDISABLE)

#ifdef _PC_SYNC_IO
	SyncIOAvailable		-> (#const _PC_SYNC_IO)
#else
	SyncIOAvailable		-> error "_PC_SYNC_IO not available"
#endif

#ifdef _PC_ASYNC_IO
	AsyncIOAvailable	-> (#const _PC_ASYNC_IO)
#else
	AsyncIOAvailable	-> error "_PC_ASYNC_IO not available"
#endif

#ifdef _PC_PRIO_IO
	PrioIOAvailable		-> (#const _PC_PRIO_IO)
#else
	PrioIOAvailable		-> error "_PC_PRIO_IO not available"
#endif

#if _PC_FILESIZEBITS
	FileSizeBits		-> (#const _PC_FILESIZEBITS)
#else
	FileSizeBits		-> error "_PC_FILESIZEBITS not available"
#endif

#if _PC_SYMLINK_MAX
	SymbolicLinkLimit	-> (#const _PC_SYMLINK_MAX)
#else
	SymbolicLinkLimit	-> error "_PC_SYMLINK_MAX not available"
#endif


-- | @getPathVar var path@ obtains the dynamic value of the requested
-- configurable file limit or option associated with file or directory @path@.
-- For defined file limits, @getPathVar@ returns the associated
-- value.  For defined file options, the result of @getPathVar@
-- is undefined, but not failure.
--
-- Note: calls @pathconf@.
getPathVar :: FilePath -> PathVar -> IO Limit
getPathVar name v = do
  withCString name $ \ nameP -> 
    throwErrnoPathIfMinus1 "getPathVar" name $ 
      c_pathconf nameP (pathVarConst v)

foreign import ccall unsafe "pathconf" 
  c_pathconf :: CString -> CInt -> IO CLong


-- | @getFdPathVar var fd@ obtains the dynamic value of the requested
-- configurable file limit or option associated with the file or directory
-- attached to the open channel @fd@. For defined file limits, @getFdPathVar@
-- returns the associated value.  For defined file options, the result of
-- @getFdPathVar@ is undefined, but not failure.
--
-- Note: calls @fpathconf@.
getFdPathVar :: Fd -> PathVar -> IO Limit
getFdPathVar fd v =
    throwErrnoIfMinus1 "getFdPathVar" $ 
      c_fpathconf fd (pathVarConst v)

foreign import ccall unsafe "fpathconf" 
  c_fpathconf :: Fd -> CInt -> IO CLong