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module Directory ( Permissions( Permissions, readable, writable, executable, searchable ), createDirectory, removeDirectory, removeFile, renameDirectory, renameFile, getDirectoryContents, getCurrentDirectory, setCurrentDirectory, doesFileExist, doesDirectoryExist, getPermissions, setPermissions, getModificationTime ) where import Time ( ClockTime ) data Permissions = Permissions { readable, writable, executable, searchable :: Bool } instance Eq Permissions where ... instance Ord Permissions where ... instance Read Permissions where ... instance Show Permissions where ... createDirectory :: FilePath -> IO () removeDirectory :: FilePath -> IO () removeFile :: FilePath -> IO () renameDirectory :: FilePath -> FilePath -> IO () renameFile :: FilePath -> FilePath -> IO () getDirectoryContents :: FilePath -> IO [FilePath] getCurrentDirectory :: IO FilePath setCurrentDirectory :: FilePath -> IO () doesFileExist :: FilePath -> IO Bool doesDirectoryExist :: FilePath -> IO Bool getPermissions :: FilePath -> IO Permissions setPermissions :: FilePath -> Permissions -> IO () getModificationTime :: FilePath -> IO ClockTime |
These functions operate on directories in the file system.
Any Directory operation could raise an isIllegalOperation, as described in Section 21.1; all other permissible errors are described below. Note that, in particular, if an implementation does not support an operation it should raise an isIllegalOperation. A directory contains a series of entries, each of which is a named reference to a file system object (file, directory etc.). Some entries may be hidden, inaccessible, or have some administrative function (for instance, "." or ".." under POSIX), but all such entries are considered to form part of the directory contents. Entries in sub-directories are not, however, considered to form part of the directory contents. Although there may be file system objects other than files and directories, this library does not distinguish between physical files and other non-directory objects. All such objects should therefore be treated as if they are files.
Each file system object is referenced by a path. There is normally at least one absolute path to each file system object. In some operating systems, it may also be possible to have paths which are relative to the current directory.
Computation createDirectory dir creates a new directory dir which is initially empty, or as near to empty as the operating system allows.
Error reporting. The createDirectory computation may fail with: isPermissionError if the user is not permitted to create the directory; isAlreadyExistsError if the directory already exists; or isDoesNotExistError if the new directory's parent does not exist.
Computation removeDirectory dir removes an existing directory dir. The implementation may specify additional constraints which must be satisfied before a directory can be removed (for instance, the directory has to be empty, or may not be in use by other processes). It is not legal for an implementation to partially remove a directory unless the entire directory is removed. A conformant implementation need not support directory removal in all situations (for instance, removal of the root directory).
Computation removeFile file removes the directory entry for an existing file file, where file is not itself a directory. The implementation may specify additional constraints which must be satisfied before a file can be removed (for instance, the file may not be in use by other processes).
Error reporting. The removeDirectory and removeFile computations may fail with: isPermissionError if the user is not permitted to remove the file/directory; or isDoesNotExistError if the file/directory does not exist.
Computation renameDirectory old new changes the name of an existing directory from old to new. If the new directory already exists, it is atomically replaced by the old directory. If the new directory is neither the old directory nor an alias of the old directory, it is removed as if by removeDirectory. A conformant implementation need not support renaming directories in all situations (for instance, renaming to an existing directory, or across different physical devices), but the constraints must be documented.
Computation renameFile old new changes the name of an existing file system object from old to new. If the new object already exists, it is atomically replaced by the old object. Neither path may refer to an existing directory. A conformant implementation need not support renaming files in all situations (for instance, renaming across different physical devices), but the constraints must be documented.
Error reporting. The renameDirectory and renameFile computations may fail with: isPermissionError if the user is not permitted to rename the file/directory, or if either argument to renameFile is a directory; or isDoesNotExistError if the file/directory does not exist.
Computation getDirectoryContents dir returns a list of all entries in dir. Each entry in the returned list is named relative to the directory dir, not as an absolute path.
If the operating system has a notion of current directories, getCurrentDirectory returns an absolute path to the current directory of the calling process.
Error reporting. The getDirectoryContents and getCurrentDirectory computations may fail with: isPermissionError if the user is not permitted to access the directory; or isDoesNotExistError if the directory does not exist.
If the operating system has a notion of current directories, setCurrentDirectory dir changes the current directory of the calling process to dir.
Error reporting. setCurrentDirectory may fail with: isPermissionError if the user is not permitted to change directory to that specified; or isDoesNotExistError if the directory does not exist.
The Permissions type is used to record whether certain operations are permissible on a file/directory. getPermissions and setPermissions get and set these permissions, respectively. Permissions apply both to files and directories. For directories, the executable field will be False, and for files the searchable field will be False. Note that directories may be searchable without being readable, if permission has been given to use them as part of a path, but not to examine the directory contents.
Note that to change
some, but not all permissions, a construct on the following lines must
be used.
makeReadable f = do
p <- getPermissions f
setPermissions f (p {readable = True})
The operation doesDirectoryExist returns True if the argument file
exists and is a directory, and False otherwise. The operation doesFileExist returns True
if the argument file exists and is not a directory, and False otherwise.
The getModificationTime operation returns the clock time at which the file/directory was last modified.
Error reporting. get(set)Permissions, doesFile(Directory)Exist, and getModificationTime may fail with: isPermissionError if the user is not permitted to access the appropriate information; or isDoesNotExistError if the file/directory does not exist. The setPermissions computation may also fail with: isPermissionError if the user is not permitted to change the permission for the specified file or directory; or isDoesNotExistError if the file/directory does not exist.