File::ChangeNotify::Watcher(3) Role consumed by all watchers


version 0.26


my $watcher =
( directories => [ '/my/path', '/my/other' ],
filter => qr/\.(?:pm|conf|yml)$/,
exclude => ['t', 'root', qr(/(?!\.)[^/]+$),
sub { -e && ! -r }],
if ( my @events = $watcher->new_events() ) { ... }
# blocking
while ( my @events = $watcher->wait_for_events() ) { ... }


A "File::ChangeNotify::Watcher" monitors a directory for changes made to any file. You can provide a regular expression to filter out files you are not interested in. It handles the addition of new subdirectories by adding them to the watch list.

Note that the actual granularity of what each watcher class reports may vary. Implementations that hook into some sort of kernel event interface (Inotify, for example) have much better knowledge of exactly what changes are happening than one implemented purely in userspace code (like the Default class).

By default, events are returned in the form File::ChangeNotify::Event objects, but this can be overridden by providing an ``event_class'' attribute to the constructor.

The watcher can operate in a blocking/callback style, or you can simply ask it for a list of new events as needed.



This method creates a new watcher. It accepts the following arguments:
  • directories => $path
  • directories => \@paths

    This argument is required. It can be either one or many paths which should be watched for changes.

  • filter => qr/.../

    This is an optional regular expression that will be used to check if a file is of interest. This filter is only applied to files.

    By default, all files are included.

  • exclude => [...]

    An optional list of paths to exclude. This list can contain plain strings, regular expressions, or subroutine references. If you provide a string it should contain the complete path to be excluded.

    If you provide a sub, it should return a true value for paths to be excluded e.g. "exclude => [ sub { -e && ! -r } ],". The path will be passed as the first argument to the subroutine as well as in a localized $_.

    The paths can be either directories or specific files. If the exclusion matches a directory, all of its files and subdirectories are ignored.

  • follow_symlinks => $bool

    By default, symlinks are ignored. Set this to true to follow them.

    If this symlinks are being followed, symlinks to files and directories will be followed. Directories will be watched, and changes for directories and files reported.

  • sleep_interval => $number

    For watchers which call "sleep" to implement the "$watcher->wait_for_events()" method, this argument controls how long it sleeps for. The value is a number in seconds.

    The default is 2 seconds.

  • event_class => $class

    This can be used to change the class used to report events. By default, this is File::ChangeNotify::Event.


This method causes the watcher to block until it sees interesting events, and then return them as a list.

Some watcher subclasses may implement blocking as a sleep loop, while others may actually block.


This method returns a list of any interesting events seen since the last time the watcher checked.


If this is true, the watcher will report on all events.

Some watchers, like the Default subclass, are not smart enough to track things like a file being created and then immediately deleted, and can only detect changes between snapshots of the file system.

Other watchers, like the Inotify subclass, see all events that happen and report on them.


Bugs may be submitted through the RT bug tracker <> (or [email protected] <mailto:[email protected]>).

I am also usually active on IRC as 'drolsky' on "irc://".


Dave Rolsky <[email protected]>


This software is Copyright (c) 2016 by Dave Rolsky.

This is free software, licensed under:

  The Artistic License 2.0 (GPL Compatible)