Mac::FSEvents - Monitor a directory structure for changes


  use Mac::FSEvents;

  my $fs = Mac::FSEvents->new(
      path          => '/',         # required, the path(s) to watch
                                    # optionally specify an arrayref of multiple paths
      latency       => 2.0,         # optional, time to delay before returning events
      since         => 451349510,   # optional, return events from this eventId
      watch_root    => 1,           # optional, fire events if the watched path changes
      ignore_self   => 1,           # optional, ignore events from this process
      file_events   => 1,           # optional, fire events on files instead of dirs
  ### OR
  my $fs = Mac::FSEvents->new( '/' ); # Only specify the path

  my $fh = $fs->watch;

  # Select on this filehandle, or use an event loop:
  my $sel = IO::Select->new($fh);
  while ( $sel->can_read ) {
      my @events = $fs->read_events;
      for my $event ( @events ) {
          printf "Directory %s changed\n", $event->path;

  # or use blocking polling:
  while ( my @events = $fs->read_events ) {

  # stop watching


This module implements the FSEvents API present in Mac OSX 10.5 and later. It enables you to watch a large directory tree and receive events when any changes are made to directories or files within the tree.

Event monitoring occurs in a separate C thread from the rest of your application.


new ( { ARGUMENTS } )
new ( PATH )

Create a new watcher. ARGUMENTS is a hash or hash reference with the following keys:


Required. A plain string or arrayref of strings of directories to watch. All subdirectories beneath these directories are watched.


Optional. The number of seconds the FSEvents service should wait after hearing about an event from the kernel before passing it along. Specifying a larger value may result in fewer callbacks and greater efficiency on a busy filesystem. Fractional seconds are allowed.

Default: 2.0


Optional. A previously obtained event ID may be passed as the since argument. A notification will be sent for every event that has happened since that ID. This can be useful for seeing what has changed while your program was not running.


(Only available on OS X 10.6 or greater)

Don't send events triggered by the current process. Useful if you are also modifying files in the watch list.


(Only available on OS X 10.7 or greater)

Send events for files. By default, only directory-level events are generated, and may be coelesced if they happen simultaneously. With this flag, an event will be generated for every change to a file.


Request notifications if the location of the paths being watched change. For example, if there is a watch for /foo/bar, and it is renamed to /foo/buzz, an event will be generated with the root_changed flag set.


Optional. Sets the flags provided to FSEventStreamCreate. In order to import the flag constants, you must provide :flags to use Mac::FSEvents.

This method of setting flags is discouraged in favor of using the constructor argument, above.

The following flags are supported:


No flags. The default.


Set by the watch_root constructor argument.


Set by the ignore_self constructor argument.


Set by the file_events constructor argument.


Begin watching. Returns a filehandle that may be used with select() or the event loop of your choice.


Returns an array of pending events. If using an event loop, this method should be called when the filehandle becomes ready for reading. If not using an event loop, this method will block until an event is available.

Events are returned as Mac::FSEvents::Event objects.

NOTE: Event paths are real file system paths, with all the symbolic links resolved. If you are watching a path with a symbolic link, use "abs_path" in Cwd if you need to make comparisons against the event's path.


Stop watching.


Andy Grundman, <>

Rob Hoelz, <>


Copyright (C) 2009 by Andy Grundman

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.8 or, at your option, any later version of Perl 5 you may have available.