[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: $!";
 
     # 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;
     });

  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_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
    Linux::Inotify.

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

Revision:	1.6
Committed:	Mon Dec 19 16:50:27 2005 UTC (18 years, 7 months ago) by root
Branch:	MAIN
CVS Tags:	rel-1_0, rel-1_01
Changes since 1.5:	+35 -4 lines
Log Message:	* empty log message *
#	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	1.6	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			or die "Unable to create new inotify object: $!";
11
12			# for Event:
13			Event->io (fd =>$inotify->fileno, poll => 'r', cb => sub { $inotify->poll });
14			# for Glib:
15			add_watch Glib::IO $inotify->fileno, in => sub { $inotify->poll };
16			# manually:
17			1 while $inotify->poll;
18
19			# add watchers
20			$inotify->watch ("/etc/passwd", IN_ACCESS, sub {
21			my $e = shift;
22			my $name = $e->fullname;
23			print "$name was accessed\n" if $e->IN_ACCESS;
24			print "$name is no longer mounted\n" if $e->IN_UNMOUNT;
25			print "$name is gone\n" if $e->IN_IGNORED;
26			print "events for $name have been lost\n" if $e->IN_Q_OVERFLOW;
27
28	root	1.6	# cancel this watcher: remove no further events
29	root	1.3	$e->w->cancel;
30			});
31
32	root	1.6	Streaming Interface
33			use Linux::Inotify2 ;
34
35			# create a new object
36			my $inotify = new Linux::Inotify2
37			or die "Unable to create new inotify object: $!" ;
38
39			# create watch
40			$inotify->watch ("/etc/passwd", IN_ACCESS)
41			or die "watch creation failed" ;
42
43			while () {
44			my @events = $inotify->read;
45			unless (@events > 0) {
46			print "read error: $!";
47			last ;
48			}
49			printf "mask\t%d\n", $_->mask foreach @events ;
50			}
51
52	root	1.1	DESCRIPTION
53	root	1.3	This module implements an interface to the Linux 2.6.13 and later
54			Inotify file/directory change notification sytem.
55	root	1.2
56	root	1.3	It has a number of advantages over the Linux::Inotify module:
57	root	1.2
58			- it is portable (Linux::Inotify only works on x86)
59			- the equivalent of fullname works correctly
60			- it is better documented
61			- it has callback-style interface, which is better suited for
62			integration.
63
64	root	1.4	The Linux::Inotify2 Class
65	root	1.2	my $inotify = new Linux::Inotify2
66			Create a new notify object and return it. A notify object is kind of
67			a container that stores watches on filesystem names and is
68			responsible for handling event data.
69
70			On error, "undef" is returned and $! will be set accordingly. The
71			followign errors are documented:
72
73			ENFILE The system limit on the total number of file descriptors has been reached.
74			EMFILE The user limit on the total number of inotify instances has been reached.
75			ENOMEM Insufficient kernel memory is available.
76
77	root	1.3	Example:
78
79			my $inotify = new Linux::Inotify2
80			or die "Unable to create new inotify object: $!";
81
82	root	1.6	$watch = $inotify->watch ($name, $mask[, $cb])
83	root	1.2	Add a new watcher to the given notifier. The watcher will create
84			events on the pathname $name as given in $mask, which can be any of
85	root	1.3	the following constants (all exported by default) ORed together.
86
87			"file" refers to any filesystem object in the watch'ed object
88			(always a directory), that is files, directories, symlinks, device
89			nodes etc., while "object" refers to the object the watch has been
90			set on itself:
91
92			IN_ACCESS object was accessed
93			IN_MODIFY object was modified
94			IN_ATTRIB object metadata changed
95			IN_CLOSE_WRITE writable fd to file / to object was closed
96			IN_CLOSE_NOWRITE readonly fd to file / to object closed
97			IN_OPEN object was opened
98			IN_MOVED_FROM file was moved from this object (directory)
99			IN_MOVED_TO file was moved to this object (directory)
100			IN_CREATE file was created in this object (directory)
101			IN_DELETE file was deleted from this object (directory)
102			IN_DELETE_SELF object itself was deleted
103	root	1.5	IN_MOVE_SELF object itself was moved
104	root	1.3	IN_ALL_EVENTS all of the above events
105	root	1.2
106			IN_ONESHOT only send event once
107
108	root	1.3	IN_CLOSE same as IN_CLOSE_WRITE \| IN_CLOSE_NOWRITE
109			IN_MOVE same as IN_MOVED_FROM \| IN_MOVED_TO
110	root	1.2
111	root	1.6	$cb is a perl code reference that, if given, is called for each
112			event. It receives a "Linux::Inotify2::Event" object.
113	root	1.2
114			The returned $watch object is of class "Linux::Inotify2::Watch".
115
116			On error, "undef" is returned and $! will be set accordingly. The
117			following errors are documented:
118
119			EBADF The given file descriptor is not valid.
120			EINVAL The given event mask contains no legal events.
121			ENOMEM Insufficient kernel memory was available.
122			ENOSPC The user limit on the total number of inotify watches was reached or the kernel failed to allocate a needed resource.
123			EACCESS Read access to the given file is not permitted.
124
125			Example, show when "/etc/passwd" gets accessed and/or modified once:
126
127			$inotify->watch ("/etc/passwd", IN_ACCESS \| IN_MODIFY, sub {
128			my $e = shift;
129			print "$e->{w}{name} was accessed\n" if $e->IN_ACCESS;
130			print "$e->{w}{name} was modified\n" if $e->IN_MODIFY;
131			print "$e->{w}{name} is no longer mounted\n" if $e->IN_UNMOUNT;
132			print "events for $e->{w}{name} have been lost\n" if $e->IN_Q_OVERFLOW;
133
134			$e->w->cancel;
135			});
136
137	root	1.3	$inotify->fileno
138	root	1.2	Returns the fileno for this notify object. You are responsible for
139			calling the "poll" method when this fileno becomes ready for
140			reading.
141
142	root	1.6	$inotify->blocking ($blocking)
143			Clears ($blocking true) or sets ($blocking false) the "O_NONBLOCK"
144			flag on the file descriptor.
145
146	root	1.3	$count = $inotify->poll
147	root	1.2	Reads events from the kernel and handles them. If the notify fileno
148			is blocking (the default), then this method waits for at least one
149	root	1.3	event (and thus returns true unless an error occurs). Otherwise it
150			returns immediately when no pending events could be read.
151	root	1.2
152			Returns the count of events that have been handled.
153
154	root	1.6	$count = $inotify->read
155			Reads events from the kernel. Blocks in blocking mode (default)
156			until any event arrives. Returns list of "Linux::Inotify2::Event"
157			objects or empty list if none (non-blocking mode) or error occured
158			($! should be checked).
159
160	root	1.2	The Linux::Inotify2::Event Class
161			Objects of this class are handed as first argument to the watch
162			callback. It has the following members and methods:
163
164			$event->w
165			$event->{w}
166			The watcher object for this event.
167
168			$event->name
169			$event->{name}
170			The path of the filesystem object, relative to the watch name.
171
172			$watch->fullname
173			Returns the "full" name of the relevant object, i.e. including the
174	root	1.5	"name" member of the watcher (if the the watch is on a directory and
175			a dir entry is affected), or simply the "name" member itself when
176			the object is the watch object itself.
177	root	1.2
178			$event->mask
179			$event->{mask}
180			The received event mask. In addition the the events described for
181			"$inotify-"watch>, the following flags (exported by default) can be
182			set:
183
184	root	1.3	IN_ISDIR event object is a directory
185			IN_Q_OVERFLOW event queue overflowed
186	root	1.2
187	root	1.5	# when any of the following flags are set,
188			# then watchers for this event are automatically canceled
189	root	1.3	IN_UNMOUNT filesystem for watch'ed object was unmounted
190			IN_IGNORED file was ignored/is gone (no more events are delivered)
191	root	1.5	IN_ONESHOT only one event was generated
192	root	1.2
193			$event->IN_xxx
194			Returns a boolean that returns true if the event mask matches the
195			event. All of the "IN_xxx" constants can be used as methods.
196
197			$event->cookie
198			$event->{cookie}
199	root	1.5	The event cookie to "synchronize two events". Normally zero, this
200			value is set when two events relating to the same file are
201			generated. As far as I know, this only happens for "IN_MOVED_FROM"
202			and "IN_MOVED_TO" events, to identify the old and new name of a
203			file.
204	root	1.2
205			The Linux::Inotify2::Watch Class
206			Watch objects are created by calling the "watch" method of a notifier.
207
208			It has the following members and methods:
209
210			$watch->name
211			$watch->{name}
212			The name as specified in the "watch" call. For the object itself, this
213			is the empty string. For directory watches, this is the name of the
214			entry without leading path elements.
215
216			$watch->mask
217			$watch->{mask}
218			The mask as specified in the "watch" call.
219
220			$watch->cb ([new callback])
221			$watch->{cb}
222			The callback as specified in the "watch" call. Can optionally be
223			changed.
224
225			$watch->cancel
226			Cancels/removes this watch. Future events, even if already queued
227			queued, will not be handled and resources will be freed.
228	root	1.1
229			SEE ALSO
230	root	1.2	Linux::Inotify.
231	root	1.1
232			AUTHOR
233			Marc Lehmann <schmorp@schmorp.de>
234			http://home.schmorp.de/
235