NAME

AnyEvent::Filesys::Notify - An AnyEvent compatible module to monitor files/directories for changes

SYNOPSIS

use AnyEvent::Filesys::Notify;

        my $notifier = AnyEvent::Filesys::Notify->new(
            dirs     => [ qw( this_dir that_dir ) ],
            interval => 2.0,             # Optional depending on underlying watcher
            filter   => sub { shift !~ /\.(swp|tmp)$/ },
            cb       => sub {
                my (@events) = @_;
                # ... process @events ...
            },
        );

        # enter an event loop, see AnyEvent documentation
        Event::loop();

DESCRIPTION

This module provides a cross platform interface to monitor files and directories within an AnyEvent event loop. The heavy lifting is done by Linux::INotify2 or Mac::FSEvents on their respective O/S. A fallback which scans the directories at regular intervals is include for other systems. See IMPLEMENTATIONS for more on the backends.

Events are passed to the callback (specified as a CodeRef to `cb' in the constructor) in the form of AnyEvent::Filesys::Notify::Events.

METHODS
new()
A constructor for a new AnyEvent watcher that will monitor the files in the given directories and execute a callback when a modification is detected. No action is take until a event loop is entered.

Arguments for new are:

dirs

dirs => [ '/var/log', '/etc' ],

An ArrayRef of directories to watch. Required.

interval

interval => 1.5, # seconds

        Specifies the time in fractional seconds between file system checks
        for the AnyEvent::Filesys::Notify::Role::Fallback implementation.

        Specifies the latency for Mac::FSEvents for the
        `AnyEvent::Filesys::Notify::Role::Mac' implementation.

        Ignored for the `AnyEvent::Filesys::Notify::Role::Linux'
        implementation.

filter

            filter => qr/\.(ya?ml|co?nf|jso?n)$/,
            filter => sub { shift !~ /\.(swp|tmp)$/,

        A CodeRef or Regexp which is used to filter wanted/unwanted events.
        If this is a Regexp, we attempt to match the absolute path name and
        filter out any that do not match. If a CodeRef, the absolute path
        name is passed as the only argument and the event is fired only if
        there sub returns a true value.

cb

cb => sub { my @events = @_; ... },

        A CodeRef that is called when a modification to the monitored
        directory(ies) is detected. The callback is passed a list of
        AnyEvent::Filesys::Notify::Events. Required.

no_external

no_external => 1,

        Force the use of the Fallback watcher implementation. This is not
        encouraged as the Fallback implement is very inefficient, but it
        does not require either Linux::INotify2 nor Mac::FSEvents. Optional.

WATCHER IMPLEMENTATIONS
Linux
Uses Linux::INotify2 to monitor directories. Sets up an `AnyEvent->io' watcher to monitor the `$inotify->fileno' filehandle.

Mac
Uses Mac::FSEvents to monitor directories. Sets up an `AnyEvent->io' watcher to monitor the `$fsevent->watch' filehandle.

Fallback
A simple scan of the watched directories at regular intervals. Sets up an `AnyEvent->timer' watcher which is executed every `interval' seconds (or fractions thereof). `interval' can be specified in the constructor to AnyEvent::Filesys::Notify and defaults to 2.0 seconds.

This is a very inefficient implementation. Use one of the others if possible.

Why Another Module For File System Notifications

At the time of writing there were several very nice modules that accomplish the task of watching files or directories and providing notifications about changes. Two of which offer a unified interface that work on any system: Filesys::Notify::Simple and File::ChangeNotify.

AnyEvent::Filesys::Notify exists because I need a way to simply tie the functionality those modules provide into an event framework. Neither of the existing modules seem to work with well with an event loop. Filesys::Notify::Simple does not supply a non-blocking interface and File::ChangeNotify requires you to poll an method for new events. You could fork off a process to run Filesys::Notify::Simple and use an event handler to watch for notices from that child, or setup a timer to check File::ChangeNotify at regular intervals, but both of those approaches seem inefficient or overly complex. Particularly, since the underlying watcher implementations (Mac::FSEvents and Linux::INotify2) provide a filehandle that you can use and IO event to watch.

This is not slight against the authors of those modules. Both are well respected, are certainly finer coders than I am, and built modules which are perfect for many situations. If one of their modules will work for you by all means use it, but if you are already using an event loop, this module may fit the bill.

SEE ALSO

Modules used to implement this module AnyEvent, Mac::FSEvents, Linux::INotify2, Moose.

Alternatives to this module Filesys::Notify::Simple, File::ChangeNotify.

BUGS

Please report any bugs or suggestions at http://rt.cpan.org/

AUTHOR

Mark Grimes, <mgrimes@cpan.org>

COPYRIGHT AND LICENSE

Copyright (C) 2009 by Mark Grimes

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.2 or, at your option, any later version of Perl 5 you may have available.