System.Delta

Description

An umberella package for the delta library. This library can be used to monitor changed new deleted files in a given directory (or set of directories).

On non OS X systems this library polls the directories of interest recursively in certain intervals, but I will add OS-specific functionality to monitor the filesystem.

On OS X this library can use the File System Events API to detect changes without recursive directory traversal.

Examples

Create a watcher that prints a line if a new file is created in the monitored directory:

printNewFilePaths basePath = do
  watcher <- deltaDirWithCallbacks basePath
  withNewCallback watcher (\x -> putStrLn $ "new file: " ++ x)

Documentation

module System.Delta.Base

module System.Delta.Poll

Important functions

deltaDir :: FilePath -> IO FileWatcher

Build a file watcher, the concrete implementation is operating system dependent.

• The default uses polling (createPollWatcher)
• The watcher for OS X uses the FS Events API createFSEventsWatcher

deltaDirWithCallbacks :: FilePath -> IO CallbackWatcher

Build a file watcher that allows to register callbacks

FRP based interface

data FileWatcher

A type for watching a directory based on functional reactive programming At the core of this class are three event streams:

• changedFiles is a stream of canonicalized FilePaths on changed files
• newFiles is a stream of canonicalized FilePaths of newly created files
• deletedFiles is a stream of canonicalized FilePaths of deleted files

Constructors

FileWatcher

Fields

newFiles :: Event FilePath

Newly created files, renamed files

deletedFiles :: Event FilePath

Deleted files, renamed files

changedFiles :: Event FilePath

Changed files

cleanUpAndClose :: IO ()

A function to clean and close ^ this watcher

Callback based interface

data CallbackWatcher

Provides a callback based interface to an FRP base FileWatcher

data CallbackId

Id of a callback in a CallbackWatcher

Instances

Eq CallbackId

Ord CallbackId

withCallbacks :: FileWatcher -> IO CallbackWatcher

Wrap a file watcher in a datatype that allows adding callbacks

Adding callbacks

withDeleteCallback

Arguments

:: CallbackWatcher

-> (FilePath -> IO ())

An IO action on the deleted path

-> IO CallbackId

Add a callback that is executed when file deletion is detected

withChangedCallback

Arguments

:: CallbackWatcher

-> (FilePath -> IO ())

Action on changed file

-> IO CallbackId

Add a callback on a changed file

withNewCallback

Arguments

:: CallbackWatcher

-> (FilePath -> IO ())

An IO action on the new path

-> IO CallbackId

Add a callback that is executed when file creation is detected

Removing callbacks

unregisterCallback :: CallbackWatcher -> CallbackId -> IO ()

Unregister the given CallbackId from the FileWatcher does nothing if the CallbackId is not in the watcher

removeAllCallbacks :: CallbackWatcher -> IO ()

Remove all callbacks form the watcher. They will not be called after this

closeCallbackWatcher :: CallbackWatcher -> IO ()

Remove all callbacks and close the underlying FileWatcher