cvsroot/Linux-Inotify2/Inotify2.pm

=head1 NAME

Linux::Inotify2 - scalable directory/file change notification

=head1 SYNOPSIS

 use Linux::Inotify2;

 # create a new object
 my $inotify = new Linux::Inotify2
    or die "Unable to create new inotify object: $!";
 
 # for Event:
 Event->io (fd =>$inotify->fileno, poll => 'r', cb => sub { $inotify->poll });
 # for Glib:
 add_watch Glib::IO $inotify->fileno, in => sub { $inotify->poll };
 # manually:
 1 while $inotify->poll;

 # add watchers
 $inotify->watch ("/etc/passwd", IN_ACCESS, sub {
    my $e = shift;
    my $name = $e->fullname;
    print "$name was accessed\n" if $e->IN_ACCESS;
    print "$name is no longer mounted\n" if $e->IN_UNMOUNT;
    print "$name is gone\n" if $e->IN_IGNORED;
    print "events for $name have been lost\n" if $e->IN_Q_OVERFLOW;
 
    # cancel this watcheR: remove no further events
    $e->w->cancel;
 });

=head1 DESCRIPTION

This module implements an interface to the Linux 2.6.13 and later Inotify
file/directory change notification sytem.

It has a number of advantages over the Linux::Inotify module:

   - it is portable (Linux::Inotify only works on x86)
   - the equivalent of fullname works correctly
   - it is better documented
   - it has callback-style interface, which is better suited for
     integration.

=head2 The Linux::Inotify2 Class

=over 4

=cut

package Linux::Inotify2;

use Carp ();
use Scalar::Util ();

use base 'Exporter';

BEGIN {
   $VERSION = 0.2;

   @constants = qw(
      IN_ACCESS IN_MODIFY IN_ATTRIB IN_CLOSE_WRITE
      IN_CLOSE_NOWRITE IN_OPEN IN_MOVED_FROM IN_MOVED_TO
      IN_CREATE IN_DELETE IN_DELETE_SELF IN_MOVE_SELF
      IN_ALL_EVENTS
      IN_UNMOUNT IN_Q_OVERFLOW IN_IGNORED
      IN_CLOSE IN_MOVE
      IN_ISDIR IN_ONESHOT
   );

   @EXPORT = @constants;

   require XSLoader;
   XSLoader::load Linux::Inotify2, $VERSION;
}

=item my $inotify = new Linux::Inotify2

Create a new notify object and return it. A notify object is kind of a
container that stores watches on filesystem names and is responsible for
handling event data.

On error, C<undef> is returned and C<$!> will be set accordingly. The followign errors
are documented:

 ENFILE   The system limit on the total number of file descriptors has been reached.
 EMFILE   The user limit on the total number of inotify instances has been reached.
 ENOMEM   Insufficient kernel memory is available.

Example:

   my $inotify = new Linux::Inotify2
      or die "Unable to create new inotify object: $!";

=cut

sub new {
   my ($class) = @_;

   my $fd = inotify_init;

   return unless $fd >= 0;

   bless { fd => $fd }, $class
}

=item $watch = $inotify->watch ($name, $mask, $cb)

Add a new watcher to the given notifier. The watcher will create events
on the pathname C<$name> as given in C<$mask>, which can be any of the
following constants (all exported by default) ORed together.

"file" refers to any filesystem object in the watch'ed object (always a
directory), that is files, directories, symlinks, device nodes etc., while
"object" refers to the object the watch has been set on itself:

 IN_ACCESS            object was accessed
 IN_MODIFY            object was modified
 IN_ATTRIB            object metadata changed
 IN_CLOSE_WRITE       writable fd to file / to object was closed
 IN_CLOSE_NOWRITE     readonly fd to file / to object closed
 IN_OPEN              object was opened
 IN_MOVED_FROM        file was moved from this object (directory)
 IN_MOVED_TO          file was moved to this object (directory)
 IN_CREATE            file was created in this object (directory)
 IN_DELETE            file was deleted from this object (directory)
 IN_DELETE_SELF       object itself was deleted
 IN_MOVE_SELF         object itself was moved
 IN_ALL_EVENTS        all of the above events

 IN_ONESHOT           only send event once

 IN_CLOSE             same as IN_CLOSE_WRITE | IN_CLOSE_NOWRITE
 IN_MOVE              same as IN_MOVED_FROM | IN_MOVED_TO

C<$cb> is a perl code reference that is called for each event. It receives
a C<Linux::Inotify2::Event> object.

The returned C<$watch> object is of class C<Linux::Inotify2::Watch>.

On error, C<undef> is returned and C<$!> will be set accordingly. The
following errors are documented:

 EBADF    The given file descriptor is not valid.
 EINVAL   The given event mask contains no legal events.
 ENOMEM   Insufficient kernel memory was available.
 ENOSPC   The user limit on the total number of inotify watches was reached or the kernel failed to allocate a needed resource.
 EACCESS  Read access to the given file is not permitted.

Example, show when C</etc/passwd> gets accessed and/or modified once:

   $inotify->watch ("/etc/passwd", IN_ACCESS | IN_MODIFY, sub {
      my $e = shift;
      print "$e->{w}{name} was accessed\n" if $e->IN_ACCESS;
      print "$e->{w}{name} was modified\n" if $e->IN_MODIFY;
      print "$e->{w}{name} is no longer mounted\n" if $e->IN_UNMOUNT;
      print "events for $e->{w}{name} have been lost\n" if $e->IN_Q_OVERFLOW;

      $e->w->cancel;
   });

=cut

sub watch {
   my ($self, $name, $mask, $cb) = @_;

   my $wd = inotify_add_watch $self->{fd}, $name, $mask;

   return unless $wd >= 0;
   
   my $w = $self->{w}{$wd} = bless {
      inotify => $self,
      wd      => $wd,
      name    => $name,
      mask    => $mask,
      cb      => $cb,
   }, Linux::Inotify2::Watch;

   Scalar::Util::weaken $w->{inotify};

   $w
}

=item $inotify->fileno

Returns the fileno for this notify object. You are responsible for calling
the C<poll> method when this fileno becomes ready for reading.

=cut

sub fileno {
   $_[0]{fd}
}

=item $count = $inotify->poll

Reads events from the kernel and handles them. If the notify fileno is
blocking (the default), then this method waits for at least one event
(and thus returns true unless an error occurs). Otherwise it returns
immediately when no pending events could be read.

Returns the count of events that have been handled.

=cut

sub poll {
   my ($self) = @_;

   my @ev = inotify_read $self->{fd};

   for (@ev) {
      my $w = $_->{w} = $self->{w}{$_->{wd}}
         or next; # no such watcher

      exists $self->{ignore}{$_->{wd}}
         and next; # watcher has been canceled

      $w->{cb}->(bless $_, Linux::Inotify2::Event);
      # TODO: what about IN_ONESHOT?
      $w->cancel if $_->{mask} & (IN_IGNORED | IN_UNMOUNT);
   }

   delete $self->{ignore};

   scalar @ev
}

sub DESTROY {
   inotify_close $_[0]{fd}
}

=back

=head2 The Linux::Inotify2::Event Class

Objects of this class are handed as first argument to the watch
callback. It has the following members and methods:

=over 4

=item $event->w

=item $event->{w}

The watcher object for this event.

=item $event->name

=item $event->{name}

The path of the filesystem object, relative to the watch name.

=item $watch->fullname

Returns the "full" name of the relevant object, i.e. including the C<name>
member of the watcher (if the the watch is on a directory and a dir entry
is affected), or simply the C<name> member itself when the object is the
watch object itself.

=item $event->mask

=item $event->{mask}

The received event mask. In addition the the events described for
C<$inotify->watch>, the following flags (exported by default) can be set:

 IN_ISDIR             event object is a directory

 IN_Q_OVERFLOW        event queue overflowed

 # when the following flags are set, then watchers are canceled automatically
 IN_UNMOUNT           filesystem for watch'ed object was unmounted
 IN_IGNORED           file was ignored/is gone (no more events are delivered)

=item $event->IN_xxx

Returns a boolean that returns true if the event mask matches the
event. All of the C<IN_xxx> constants can be used as methods.

=item $event->cookie

=item $event->{cookie}

The event cookie to "synchronize two events". Currently, this is always
zero, and I have no idea what it's supposed use is. Educate me!

=back

=cut

package Linux::Inotify2::Event;

sub w       { $_[0]{w}      }
sub name    { $_[0]{name}   }
sub mask    { $_[0]{mask}   }
sub cookie  { $_[0]{cookie} }

sub fullname {
   length $_[0]{name}
      ? "$_[0]{w}{name}/$_[0]{name}"
      : $_[0]{w}{name};
}

for my $name (@Linux::Inotify2::constants) {
   my $mask = &{"Linux::Inotify2::$name"};

   *$name = sub { ($_[0]{mask} & $mask) == $mask };
}

=head2 The Linux::Inotify2::Watch Class

Watch objects are created by calling the C<watch> method of a notifier.

It has the following members and methods:

=item $watch->name

=item $watch->{name}

The name as specified in the C<watch> call. For the object itself, this is
the empty string.  For directory watches, this is the name of the entry
without leading path elements.

=item $watch->mask

=item $watch->{mask}

The mask as specified in the C<watch> call.

=item $watch->cb ([new callback])

=item $watch->{cb}

The callback as specified in the C<watch> call. Can optionally be changed.

=item $watch->cancel

Cancels/removes this watch. Future events, even if already queued queued,
will not be handled and resources will be freed.

=cut

package Linux::Inotify2::Watch;

sub name    { $_[0]{name} }
sub mask    { $_[0]{mask} }

sub cb {
   $_[0]{cb} = $_[1] if @_ > 1;
   $_[0]{cb}
}

sub cancel {
   my ($self) = @_;

   my $inotify = delete $self->{inotify}
      or return 1; # already canceled

   delete $inotify->{w}{$self->{wd}}; # we are no longer there
   $inotify->{ignore}{$self->{wd}} = 1; # ignore further events for one poll

   (Linux::Inotify2::inotify_rm_watch $inotify->{fd}, $self->{wd})
      ? 1 : undef
}

=head1 SEE ALSO

L<Linux::Inotify>.

=head1 AUTHOR

 Marc Lehmann <schmorp@schmorp.de>
 http://home.schmorp.de/

=cut

1
Revision:	1.9
Committed:	Tue Aug 23 02:45:23 2005 UTC (18 years, 10 months ago) by root
Branch:	MAIN
Changes since 1.8:	+2 -1 lines
Log Message:	* empty log message *
#	Content
1	=head1 NAME
2
3	Linux::Inotify2 - scalable directory/file change notification
4
5	=head1 SYNOPSIS
6
7	use Linux::Inotify2;
8
9	# create a new object
10	my $inotify = new Linux::Inotify2
11	or die "Unable to create new inotify object: $!";
12
13	# for Event:
14	Event->io (fd =>$inotify->fileno, poll => 'r', cb => sub { $inotify->poll });
15	# for Glib:
16	add_watch Glib::IO $inotify->fileno, in => sub { $inotify->poll };
17	# manually:
18	1 while $inotify->poll;
19
20	# add watchers
21	$inotify->watch ("/etc/passwd", IN_ACCESS, sub {
22	my $e = shift;
23	my $name = $e->fullname;
24	print "$name was accessed\n" if $e->IN_ACCESS;
25	print "$name is no longer mounted\n" if $e->IN_UNMOUNT;
26	print "$name is gone\n" if $e->IN_IGNORED;
27	print "events for $name have been lost\n" if $e->IN_Q_OVERFLOW;
28
29	# cancel this watcheR: remove no further events
30	$e->w->cancel;
31	});
32
33	=head1 DESCRIPTION
34
35	This module implements an interface to the Linux 2.6.13 and later Inotify
36	file/directory change notification sytem.
37
38	It has a number of advantages over the Linux::Inotify module:
39
40	- it is portable (Linux::Inotify only works on x86)
41	- the equivalent of fullname works correctly
42	- it is better documented
43	- it has callback-style interface, which is better suited for
44	integration.
45
46	=head2 The Linux::Inotify2 Class
47
48	=over 4
49
50	=cut
51
52	package Linux::Inotify2;
53
54	use Carp ();
55	use Scalar::Util ();
56
57	use base 'Exporter';
58
59	BEGIN {
60	$VERSION = 0.2;
61
62	@constants = qw(
63	IN_ACCESS IN_MODIFY IN_ATTRIB IN_CLOSE_WRITE
64	IN_CLOSE_NOWRITE IN_OPEN IN_MOVED_FROM IN_MOVED_TO
65	IN_CREATE IN_DELETE IN_DELETE_SELF IN_MOVE_SELF
66	IN_ALL_EVENTS
67	IN_UNMOUNT IN_Q_OVERFLOW IN_IGNORED
68	IN_CLOSE IN_MOVE
69	IN_ISDIR IN_ONESHOT
70	);
71
72	@EXPORT = @constants;
73
74	require XSLoader;
75	XSLoader::load Linux::Inotify2, $VERSION;
76	}
77
78	=item my $inotify = new Linux::Inotify2
79
80	Create a new notify object and return it. A notify object is kind of a
81	container that stores watches on filesystem names and is responsible for
82	handling event data.
83
84	On error, C<undef> is returned and C<$!> will be set accordingly. The followign errors
85	are documented:
86
87	ENFILE The system limit on the total number of file descriptors has been reached.
88	EMFILE The user limit on the total number of inotify instances has been reached.
89	ENOMEM Insufficient kernel memory is available.
90
91	Example:
92
93	my $inotify = new Linux::Inotify2
94	or die "Unable to create new inotify object: $!";
95
96	=cut
97
98	sub new {
99	my ($class) = @_;
100
101	my $fd = inotify_init;
102
103	return unless $fd >= 0;
104
105	bless { fd => $fd }, $class
106	}
107
108	=item $watch = $inotify->watch ($name, $mask, $cb)
109
110	Add a new watcher to the given notifier. The watcher will create events
111	on the pathname C<$name> as given in C<$mask>, which can be any of the
112	following constants (all exported by default) ORed together.
113
114	"file" refers to any filesystem object in the watch'ed object (always a
115	directory), that is files, directories, symlinks, device nodes etc., while
116	"object" refers to the object the watch has been set on itself:
117
118	IN_ACCESS object was accessed
119	IN_MODIFY object was modified
120	IN_ATTRIB object metadata changed
121	IN_CLOSE_WRITE writable fd to file / to object was closed
122	IN_CLOSE_NOWRITE readonly fd to file / to object closed
123	IN_OPEN object was opened
124	IN_MOVED_FROM file was moved from this object (directory)
125	IN_MOVED_TO file was moved to this object (directory)
126	IN_CREATE file was created in this object (directory)
127	IN_DELETE file was deleted from this object (directory)
128	IN_DELETE_SELF object itself was deleted
129	IN_MOVE_SELF object itself was moved
130	IN_ALL_EVENTS all of the above events
131
132	IN_ONESHOT only send event once
133
134	IN_CLOSE same as IN_CLOSE_WRITE \| IN_CLOSE_NOWRITE
135	IN_MOVE same as IN_MOVED_FROM \| IN_MOVED_TO
136
137	C<$cb> is a perl code reference that is called for each event. It receives
138	a C<Linux::Inotify2::Event> object.
139
140	The returned C<$watch> object is of class C<Linux::Inotify2::Watch>.
141
142	On error, C<undef> is returned and C<$!> will be set accordingly. The
143	following errors are documented:
144
145	EBADF The given file descriptor is not valid.
146	EINVAL The given event mask contains no legal events.
147	ENOMEM Insufficient kernel memory was available.
148	ENOSPC The user limit on the total number of inotify watches was reached or the kernel failed to allocate a needed resource.
149	EACCESS Read access to the given file is not permitted.
150
151	Example, show when C</etc/passwd> gets accessed and/or modified once:
152
153	$inotify->watch ("/etc/passwd", IN_ACCESS \| IN_MODIFY, sub {
154	my $e = shift;
155	print "$e->{w}{name} was accessed\n" if $e->IN_ACCESS;
156	print "$e->{w}{name} was modified\n" if $e->IN_MODIFY;
157	print "$e->{w}{name} is no longer mounted\n" if $e->IN_UNMOUNT;
158	print "events for $e->{w}{name} have been lost\n" if $e->IN_Q_OVERFLOW;
159
160	$e->w->cancel;
161	});
162
163	=cut
164
165	sub watch {
166	my ($self, $name, $mask, $cb) = @_;
167
168	my $wd = inotify_add_watch $self->{fd}, $name, $mask;
169
170	return unless $wd >= 0;
171
172	my $w = $self->{w}{$wd} = bless {
173	inotify => $self,
174	wd => $wd,
175	name => $name,
176	mask => $mask,
177	cb => $cb,
178	}, Linux::Inotify2::Watch;
179
180	Scalar::Util::weaken $w->{inotify};
181
182	$w
183	}
184
185	=item $inotify->fileno
186
187	Returns the fileno for this notify object. You are responsible for calling
188	the C<poll> method when this fileno becomes ready for reading.
189
190	=cut
191
192	sub fileno {
193	$_[0]{fd}
194	}
195
196	=item $count = $inotify->poll
197
198	Reads events from the kernel and handles them. If the notify fileno is
199	blocking (the default), then this method waits for at least one event
200	(and thus returns true unless an error occurs). Otherwise it returns
201	immediately when no pending events could be read.
202
203	Returns the count of events that have been handled.
204
205	=cut
206
207	sub poll {
208	my ($self) = @_;
209
210	my @ev = inotify_read $self->{fd};
211
212	for (@ev) {
213	my $w = $_->{w} = $self->{w}{$_->{wd}}
214	or next; # no such watcher
215
216	exists $self->{ignore}{$_->{wd}}
217	and next; # watcher has been canceled
218
219	$w->{cb}->(bless $_, Linux::Inotify2::Event);
220	# TODO: what about IN_ONESHOT?
221	$w->cancel if $_->{mask} & (IN_IGNORED \| IN_UNMOUNT);
222	}
223
224	delete $self->{ignore};
225
226	scalar @ev
227	}
228
229	sub DESTROY {
230	inotify_close $_[0]{fd}
231	}
232
233	=back
234
235	=head2 The Linux::Inotify2::Event Class
236
237	Objects of this class are handed as first argument to the watch
238	callback. It has the following members and methods:
239
240	=over 4
241
242	=item $event->w
243
244	=item $event->{w}
245
246	The watcher object for this event.
247
248	=item $event->name
249
250	=item $event->{name}
251
252	The path of the filesystem object, relative to the watch name.
253
254	=item $watch->fullname
255
256	Returns the "full" name of the relevant object, i.e. including the C<name>
257	member of the watcher (if the the watch is on a directory and a dir entry
258	is affected), or simply the C<name> member itself when the object is the
259	watch object itself.
260
261	=item $event->mask
262
263	=item $event->{mask}
264
265	The received event mask. In addition the the events described for
266	C<$inotify->watch>, the following flags (exported by default) can be set:
267
268	IN_ISDIR event object is a directory
269
270	IN_Q_OVERFLOW event queue overflowed
271
272	# when the following flags are set, then watchers are canceled automatically
273	IN_UNMOUNT filesystem for watch'ed object was unmounted
274	IN_IGNORED file was ignored/is gone (no more events are delivered)
275
276	=item $event->IN_xxx
277
278	Returns a boolean that returns true if the event mask matches the
279	event. All of the C<IN_xxx> constants can be used as methods.
280
281	=item $event->cookie
282
283	=item $event->{cookie}
284
285	The event cookie to "synchronize two events". Currently, this is always
286	zero, and I have no idea what it's supposed use is. Educate me!
287
288	=back
289
290	=cut
291
292	package Linux::Inotify2::Event;
293
294	sub w { $_[0]{w} }
295	sub name { $_[0]{name} }
296	sub mask { $_[0]{mask} }
297	sub cookie { $_[0]{cookie} }
298
299	sub fullname {
300	length $_[0]{name}
301	? "$_[0]{w}{name}/$_[0]{name}"
302	: $_[0]{w}{name};
303	}
304
305	for my $name (@Linux::Inotify2::constants) {
306	my $mask = &{"Linux::Inotify2::$name"};
307
308	*$name = sub { ($_[0]{mask} & $mask) == $mask };
309	}
310
311	=head2 The Linux::Inotify2::Watch Class
312
313	Watch objects are created by calling the C<watch> method of a notifier.
314
315	It has the following members and methods:
316
317	=item $watch->name
318
319	=item $watch->{name}
320
321	The name as specified in the C<watch> call. For the object itself, this is
322	the empty string. For directory watches, this is the name of the entry
323	without leading path elements.
324
325	=item $watch->mask
326
327	=item $watch->{mask}
328
329	The mask as specified in the C<watch> call.
330
331	=item $watch->cb ([new callback])
332
333	=item $watch->{cb}
334
335	The callback as specified in the C<watch> call. Can optionally be changed.
336
337	=item $watch->cancel
338
339	Cancels/removes this watch. Future events, even if already queued queued,
340	will not be handled and resources will be freed.
341
342	=cut
343
344	package Linux::Inotify2::Watch;
345
346	sub name { $_[0]{name} }
347	sub mask { $_[0]{mask} }
348
349	sub cb {
350	$_[0]{cb} = $_[1] if @_ > 1;
351	$_[0]{cb}
352	}
353
354	sub cancel {
355	my ($self) = @_;
356
357	my $inotify = delete $self->{inotify}
358	or return 1; # already canceled
359
360	delete $inotify->{w}{$self->{wd}}; # we are no longer there
361	$inotify->{ignore}{$self->{wd}} = 1; # ignore further events for one poll
362
363	(Linux::Inotify2::inotify_rm_watch $inotify->{fd}, $self->{wd})
364	? 1 : undef
365	}
366
367	=head1 SEE ALSO
368
369	L<Linux::Inotify>.
370
371	=head1 AUTHOR
372
373	Marc Lehmann <schmorp@schmorp.de>
374	http://home.schmorp.de/
375
376	=cut
377
378	1