Detecting real-time file directory changes

In this recipe, we will instantly detect when a new file is created, modified, or deleted. Similar to the popular file synchronization software Dropbox, we will be able to do interesting actions every time such an event occurs.

Getting ready

Install the fsnotify package:

$ cabal install fsnotify

How to do it…

In a new file called Main.hs, perform these steps:

1. Import the relevant libraries:

   {-# LANGUAGE OverloadedStrings #-}
   import Filesystem.Path.CurrentOS
   import System.FSNotify
   import Filesystem
   import Filesystem.Path (filename)

2. Run the file watcher on the current directory:

   main :: IO ()
   
   main = do
     wd <- getWorkingDirectory
     print wd
   
     man <- startManager
     watchTree man wd (const True) doWork
     putStrLn "press return to stop"
   
     getLine
     putStrLn "watching stopped, press return to exit"
   
     stopManager man
     getLine
     return ()

3. Handle each of the file change events. In this recipe, we just print out the action to...