[ViewVC] Annotation of: cvs/cvsroot/Linux-Inotify2/README

NAME
    Linux::Inotify2 - scalable directory/file change notification

SYNOPSIS
  Callback Interface
     use Linux::Inotify2;

     # create a new object
     my $inotify = new Linux::Inotify2
        or die "unable to create new inotify object: $!";
     
 # 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;
     });

     # integration into AnyEvent (works with POE, Glib, Tk...)
     my $inotify_w = AnyEvent->io 
        fh => $inofity, poll => 'r', cb => sub { $inotify->poll }
     );

     # manual event loop
     1 while $inotify->poll;

  Streaming Interface
     use Linux::Inotify2 ;

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

     # create watch
     $inotify->watch ("/etc/passwd", IN_ACCESS)
        or die "watch creation failed" ;

     while () {
       my @events = $inotify->read;
       unless (@events > 0) {
         print "read error: $!";
         last ;
       }
       printf "mask\t%d\n", $_->mask foreach @events ; 
     }

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.

  The Linux::Inotify2 Class
    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, "undef" is returned and $! 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: $!";

    $watch = $inotify->watch ($name, $mask[, $cb])
        Add a new watcher to the given notifier. The watcher will create
        events on the pathname $name as given in $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_ONLYDIR           only watch the path if it is a directory
         IN_DONT_FOLLOW       don't follow a sym link
         IN_MASK_ADD          not supported with the current version of this module

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

        $cb is a perl code reference that, if given, is called for each
        event. It receives a "Linux::Inotify2::Event" object.

        The returned $watch object is of class "Linux::Inotify2::Watch".

        On error, "undef" is returned and $! 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 "/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;
           });

    $inotify->fileno
        Returns the fileno for this notify object. You are responsible for
        calling the "poll" method when this fileno becomes ready for
        reading.

    $inotify->blocking ($blocking)
        Clears ($blocking true) or sets ($blocking false) the "O_NONBLOCK"
        flag on the file descriptor.

    $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.

    $count = $inotify->read
        Reads events from the kernel. Blocks in blocking mode (default)
        until any event arrives. Returns list of "Linux::Inotify2::Event"
        objects or empty list if none (non-blocking mode) or error occured
        ($! should be checked).

  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:

    $event->w
    $event->{w}
        The watcher object for this event.

    $event->name
    $event->{name}
        The path of the filesystem object, relative to the watch name.

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

    $event->mask
    $event->{mask}
        The received event mask. In addition the the events described for
        "$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 any of the following flags are set,
         # then watchers for this event are automatically canceled
         IN_UNMOUNT           filesystem for watch'ed object was unmounted
         IN_IGNORED           file was ignored/is gone (no more events are delivered)
         IN_ONESHOT           only one event was generated

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

    $event->cookie
    $event->{cookie}
        The event cookie to "synchronize two events". Normally zero, this
        value is set when two events relating to the same file are
        generated. As far as I know, this only happens for "IN_MOVED_FROM"
        and "IN_MOVED_TO" events, to identify the old and new name of a
        file.

  The Linux::Inotify2::Watch Class
    Watch objects are created by calling the "watch" method of a notifier.

    It has the following members and methods:

    $watch->name
    $watch->{name}
        The name as specified in the "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.

    $watch->mask
    $watch->{mask}
        The mask as specified in the "watch" call.

    $watch->cb ([new callback])
    $watch->{cb}
        The callback as specified in the "watch" call. Can optionally be
        changed.

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

SEE ALSO
    AnyEvent, Linux::Inotify.

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

Revision:	1.8
Committed:	Tue Oct 7 17:25:11 2008 UTC (17 years, 11 months ago) by root
Branch:	MAIN
CVS Tags:	rel-1_2
Changes since 1.7:	+15 -14 lines
Log Message:	1.2
#	User	Rev	Content
1	root	1.1	NAME
2	root	1.2	Linux::Inotify2 - scalable directory/file change notification
3	root	1.1
4			SYNOPSIS
5	root	1.8	Callback Interface
6	root	1.2	use Linux::Inotify2;
7	root	1.1
8	root	1.3	# create a new object
9			my $inotify = new Linux::Inotify2
10	root	1.8	or die "unable to create new inotify object: $!";
11
12			# add watchers
13	root	1.3	$inotify->watch ("/etc/passwd", IN_ACCESS, sub {
14			my $e = shift;
15			my $name = $e->fullname;
16			print "$name was accessed\n" if $e->IN_ACCESS;
17			print "$name is no longer mounted\n" if $e->IN_UNMOUNT;
18			print "$name is gone\n" if $e->IN_IGNORED;
19			print "events for $name have been lost\n" if $e->IN_Q_OVERFLOW;
20	root	1.8
21			# cancel this watcher: remove no further events
22	root	1.3	$e->w->cancel;
23			});
24
25	root	1.8	# integration into AnyEvent (works with POE, Glib, Tk...)
26			my $inotify_w = AnyEvent->io
27			fh => $inofity, poll => 'r', cb => sub { $inotify->poll }
28			);
29
30			# manual event loop
31			1 while $inotify->poll;
32
33	root	1.6	Streaming Interface
34			use Linux::Inotify2 ;
35
36			# create a new object
37			my $inotify = new Linux::Inotify2
38			or die "Unable to create new inotify object: $!" ;
39
40			# create watch
41			$inotify->watch ("/etc/passwd", IN_ACCESS)
42			or die "watch creation failed" ;
43
44			while () {
45			my @events = $inotify->read;
46			unless (@events > 0) {
47			print "read error: $!";
48			last ;
49			}
50			printf "mask\t%d\n", $_->mask foreach @events ;
51			}
52
53	root	1.1	DESCRIPTION
54	root	1.3	This module implements an interface to the Linux 2.6.13 and later
55			Inotify file/directory change notification sytem.
56	root	1.2
57	root	1.3	It has a number of advantages over the Linux::Inotify module:
58	root	1.2
59			- it is portable (Linux::Inotify only works on x86)
60			- the equivalent of fullname works correctly
61			- it is better documented
62			- it has callback-style interface, which is better suited for
63			integration.
64
65	root	1.4	The Linux::Inotify2 Class
66	root	1.2	my $inotify = new Linux::Inotify2
67			Create a new notify object and return it. A notify object is kind of
68			a container that stores watches on filesystem names and is
69			responsible for handling event data.
70
71			On error, "undef" is returned and $! will be set accordingly. The
72			followign errors are documented:
73
74			ENFILE The system limit on the total number of file descriptors has been reached.
75			EMFILE The user limit on the total number of inotify instances has been reached.
76			ENOMEM Insufficient kernel memory is available.
77
78	root	1.3	Example:
79
80			my $inotify = new Linux::Inotify2
81			or die "Unable to create new inotify object: $!";
82
83	root	1.6	$watch = $inotify->watch ($name, $mask[, $cb])
84	root	1.2	Add a new watcher to the given notifier. The watcher will create
85			events on the pathname $name as given in $mask, which can be any of
86	root	1.3	the following constants (all exported by default) ORed together.
87
88			"file" refers to any filesystem object in the watch'ed object
89			(always a directory), that is files, directories, symlinks, device
90			nodes etc., while "object" refers to the object the watch has been
91			set on itself:
92
93			IN_ACCESS object was accessed
94			IN_MODIFY object was modified
95			IN_ATTRIB object metadata changed
96			IN_CLOSE_WRITE writable fd to file / to object was closed
97			IN_CLOSE_NOWRITE readonly fd to file / to object closed
98			IN_OPEN object was opened
99			IN_MOVED_FROM file was moved from this object (directory)
100			IN_MOVED_TO file was moved to this object (directory)
101			IN_CREATE file was created in this object (directory)
102			IN_DELETE file was deleted from this object (directory)
103			IN_DELETE_SELF object itself was deleted
104	root	1.5	IN_MOVE_SELF object itself was moved
105	root	1.3	IN_ALL_EVENTS all of the above events
106	root	1.2
107			IN_ONESHOT only send event once
108	root	1.7	IN_ONLYDIR only watch the path if it is a directory
109			IN_DONT_FOLLOW don't follow a sym link
110			IN_MASK_ADD not supported with the current version of this module
111	root	1.2
112	root	1.3	IN_CLOSE same as IN_CLOSE_WRITE \| IN_CLOSE_NOWRITE
113			IN_MOVE same as IN_MOVED_FROM \| IN_MOVED_TO
114	root	1.2
115	root	1.6	$cb is a perl code reference that, if given, is called for each
116			event. It receives a "Linux::Inotify2::Event" object.
117	root	1.2
118			The returned $watch object is of class "Linux::Inotify2::Watch".
119
120			On error, "undef" is returned and $! will be set accordingly. The
121			following errors are documented:
122
123			EBADF The given file descriptor is not valid.
124			EINVAL The given event mask contains no legal events.
125			ENOMEM Insufficient kernel memory was available.
126			ENOSPC The user limit on the total number of inotify watches was reached or the kernel failed to allocate a needed resource.
127			EACCESS Read access to the given file is not permitted.
128
129			Example, show when "/etc/passwd" gets accessed and/or modified once:
130
131			$inotify->watch ("/etc/passwd", IN_ACCESS \| IN_MODIFY, sub {
132			my $e = shift;
133			print "$e->{w}{name} was accessed\n" if $e->IN_ACCESS;
134			print "$e->{w}{name} was modified\n" if $e->IN_MODIFY;
135			print "$e->{w}{name} is no longer mounted\n" if $e->IN_UNMOUNT;
136			print "events for $e->{w}{name} have been lost\n" if $e->IN_Q_OVERFLOW;
137
138			$e->w->cancel;
139			});
140
141	root	1.3	$inotify->fileno
142	root	1.2	Returns the fileno for this notify object. You are responsible for
143			calling the "poll" method when this fileno becomes ready for
144			reading.
145
146	root	1.6	$inotify->blocking ($blocking)
147			Clears ($blocking true) or sets ($blocking false) the "O_NONBLOCK"
148			flag on the file descriptor.
149
150	root	1.3	$count = $inotify->poll
151	root	1.2	Reads events from the kernel and handles them. If the notify fileno
152			is blocking (the default), then this method waits for at least one
153	root	1.3	event (and thus returns true unless an error occurs). Otherwise it
154			returns immediately when no pending events could be read.
155	root	1.2
156			Returns the count of events that have been handled.
157
158	root	1.6	$count = $inotify->read
159			Reads events from the kernel. Blocks in blocking mode (default)
160			until any event arrives. Returns list of "Linux::Inotify2::Event"
161			objects or empty list if none (non-blocking mode) or error occured
162			($! should be checked).
163
164	root	1.2	The Linux::Inotify2::Event Class
165			Objects of this class are handed as first argument to the watch
166			callback. It has the following members and methods:
167
168			$event->w
169			$event->{w}
170			The watcher object for this event.
171
172			$event->name
173			$event->{name}
174			The path of the filesystem object, relative to the watch name.
175
176			$watch->fullname
177			Returns the "full" name of the relevant object, i.e. including the
178	root	1.5	"name" member of the watcher (if the the watch is on a directory and
179			a dir entry is affected), or simply the "name" member itself when
180			the object is the watch object itself.
181	root	1.2
182			$event->mask
183			$event->{mask}
184			The received event mask. In addition the the events described for
185			"$inotify-"watch>, the following flags (exported by default) can be
186			set:
187
188	root	1.3	IN_ISDIR event object is a directory
189			IN_Q_OVERFLOW event queue overflowed
190	root	1.2
191	root	1.5	# when any of the following flags are set,
192			# then watchers for this event are automatically canceled
193	root	1.3	IN_UNMOUNT filesystem for watch'ed object was unmounted
194			IN_IGNORED file was ignored/is gone (no more events are delivered)
195	root	1.5	IN_ONESHOT only one event was generated
196	root	1.2
197			$event->IN_xxx
198			Returns a boolean that returns true if the event mask matches the
199			event. All of the "IN_xxx" constants can be used as methods.
200
201			$event->cookie
202			$event->{cookie}
203	root	1.5	The event cookie to "synchronize two events". Normally zero, this
204			value is set when two events relating to the same file are
205			generated. As far as I know, this only happens for "IN_MOVED_FROM"
206			and "IN_MOVED_TO" events, to identify the old and new name of a
207			file.
208	root	1.2
209			The Linux::Inotify2::Watch Class
210			Watch objects are created by calling the "watch" method of a notifier.
211
212			It has the following members and methods:
213
214			$watch->name
215			$watch->{name}
216	root	1.7	The name as specified in the "watch" call. For the object itself,
217			this is the empty string. For directory watches, this is the name of
218			the entry without leading path elements.
219	root	1.2
220			$watch->mask
221			$watch->{mask}
222	root	1.7	The mask as specified in the "watch" call.
223	root	1.2
224			$watch->cb ([new callback])
225			$watch->{cb}
226	root	1.7	The callback as specified in the "watch" call. Can optionally be
227			changed.
228	root	1.2
229			$watch->cancel
230	root	1.7	Cancels/removes this watch. Future events, even if already queued
231			queued, will not be handled and resources will be freed.
232	root	1.1
233			SEE ALSO
234	root	1.8	AnyEvent, Linux::Inotify.
235	root	1.1
236			AUTHOR
237			Marc Lehmann <schmorp@schmorp.de>
238			http://home.schmorp.de/
239