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).

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

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 PollWatcher

Build a file watcher, this method will change later

deltaDirWithCallbacks :: FilePath -> IO (CallbackWatcher PollWatcher)

Build a file watcher that allows to register callbacks

FRP based interface

module System.Delta.Class

class FileWatcher a where

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

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

Minimal complete definition

defaultWatcher, changedFiles, newFiles, deletedFiles, cleanUpAndClose, mergeWatchers

Methods

defaultWatcher :: FilePath -> IO a

Each type provides a default watcher for a pass

changedFiles :: a -> Event FileInfo

An event that gives some info on changed files (disjunct from deleted and new files)

newFiles :: a -> Event FilePath

An event that fires for each new file

deletedFiles :: a -> Event FilePath

An event that fires for each deleted path

cleanUpAndClose :: a -> IO ()

Free all possibly used resources. No event will fire after this.

mergeWatchers :: a -> a -> a

Merge two watchers that are watching different directories

watchPaths :: FileWatcher a => [FilePath] -> Maybe (IO a)

Create a watcher on all of the given paths

Instances

FileWatcher PollWatcher

Callback based interface

module System.Delta.Callback

data CallbackWatcher w

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 a => a -> IO (CallbackWatcher a)

Wrap a file watcher in a datatype that allows adding callbacks

Adding callbacks

withDeleteCallback

Arguments

:: FileWatcher a

=> CallbackWatcher a

-> (FilePath -> IO ())

An IO action on the deleted path

-> IO CallbackId

Add a callback that is executed when file deletion is detected

withChangedCallback

Arguments

:: FileWatcher a

=> CallbackWatcher a

-> (FileInfo -> IO ())

Action on changed file

-> IO CallbackId

Add a callback on a changed file

withNewCallback

Arguments

:: FileWatcher a

=> CallbackWatcher a

-> (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 :: FileWatcher a => CallbackWatcher a -> CallbackId -> IO ()

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

removeAllCallbacks :: FileWatcher a => CallbackWatcher a -> IO ()

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

closeCallbackWatcher :: FileWatcher a => CallbackWatcher a -> IO ()

Remove all callbacks and close the underlying FileWatcher