1Inotify2(3)           User Contributed Perl Documentation          Inotify2(3)
2
3
4

NAME

6       Linux::Inotify2 - scalable directory/file change notification
7

SYNOPSIS

9   Callback Interface
10        use Linux::Inotify2;
11
12        # create a new object
13        my $inotify = new Linux::Inotify2
14           or die "unable to create new inotify object: $!";
15
16        # add watchers
17        $inotify->watch ("/etc/passwd", IN_ACCESS, sub {
18           my $e = shift;
19           my $name = $e->fullname;
20           print "$name was accessed\n" if $e->IN_ACCESS;
21           print "$name is no longer mounted\n" if $e->IN_UNMOUNT;
22           print "$name is gone\n" if $e->IN_IGNORED;
23           print "events for $name have been lost\n" if $e->IN_Q_OVERFLOW;
24
25           # cancel this watcher: remove no further events
26           $e->w->cancel;
27        });
28
29        # integration into AnyEvent (works with EV, Glib, Tk, POE...)
30        my $inotify_w = AnyEvent->io (
31           fh => $inofity->fileno, poll => 'r', cb => sub { $inotify->poll }
32        );
33
34        # manual event loop
35        1 while $inotify->poll;
36
37   Streaming Interface
38        use Linux::Inotify2 ;
39
40        # create a new object
41        my $inotify = new Linux::Inotify2
42           or die "Unable to create new inotify object: $!" ;
43
44        # create watch
45        $inotify->watch ("/etc/passwd", IN_ACCESS)
46           or die "watch creation failed" ;
47
48        while () {
49          my @events = $inotify->read;
50          unless (@events > 0) {
51            print "read error: $!";
52            last ;
53          }
54          printf "mask\t%d\n", $_->mask foreach @events ;
55        }
56

DESCRIPTION

58       This module implements an interface to the Linux 2.6.13 and later
59       Inotify file/directory change notification sytem.
60
61       It has a number of advantages over the Linux::Inotify module:
62
63          - it is portable (Linux::Inotify only works on x86)
64          - the equivalent of fullname works correctly
65          - it is better documented
66          - it has callback-style interface, which is better suited for
67            integration.
68
69   The Linux::Inotify2 Class
70       my $inotify = new Linux::Inotify2
71           Create a new notify object and return it. A notify object is kind
72           of a container that stores watches on filesystem names and is
73           responsible for handling event data.
74
75           On error, "undef" is returned and $! will be set accordingly. The
76           followign errors are documented:
77
78            ENFILE   The system limit on the total number of file descriptors has been reached.
79            EMFILE   The user limit on the total number of inotify instances has been reached.
80            ENOMEM   Insufficient kernel memory is available.
81
82           Example:
83
84              my $inotify = new Linux::Inotify2
85                 or die "Unable to create new inotify object: $!";
86
87       $watch = $inotify->watch ($name, $mask[, $cb])
88           Add a new watcher to the given notifier. The watcher will create
89           events on the pathname $name as given in $mask, which can be any of
90           the following constants (all exported by default) ORed together.
91
92           "file" refers to any filesystem object in the watch'ed object
93           (always a directory), that is files, directories, symlinks, device
94           nodes etc., while "object" refers to the object the watch has been
95           set on itself:
96
97            IN_ACCESS            object was accessed
98            IN_MODIFY            object was modified
99            IN_ATTRIB            object metadata changed
100            IN_CLOSE_WRITE       writable fd to file / to object was closed
101            IN_CLOSE_NOWRITE     readonly fd to file / to object closed
102            IN_OPEN              object was opened
103            IN_MOVED_FROM        file was moved from this object (directory)
104            IN_MOVED_TO          file was moved to this object (directory)
105            IN_CREATE            file was created in this object (directory)
106            IN_DELETE            file was deleted from this object (directory)
107            IN_DELETE_SELF       object itself was deleted
108            IN_MOVE_SELF         object itself was moved
109            IN_ALL_EVENTS        all of the above events
110
111            IN_ONESHOT           only send event once
112            IN_ONLYDIR           only watch the path if it is a directory
113            IN_DONT_FOLLOW       don't follow a sym link
114            IN_MASK_ADD          not supported with the current version of this module
115
116            IN_CLOSE             same as IN_CLOSE_WRITE | IN_CLOSE_NOWRITE
117            IN_MOVE              same as IN_MOVED_FROM | IN_MOVED_TO
118
119           $cb is a perl code reference that, if given, is called for each
120           event. It receives a "Linux::Inotify2::Event" object.
121
122           The returned $watch object is of class "Linux::Inotify2::Watch".
123
124           On error, "undef" is returned and $! will be set accordingly. The
125           following errors are documented:
126
127            EBADF    The given file descriptor is not valid.
128            EINVAL   The given event mask contains no legal events.
129            ENOMEM   Insufficient kernel memory was available.
130            ENOSPC   The user limit on the total number of inotify watches was reached or the kernel failed to allocate a needed resource.
131            EACCESS  Read access to the given file is not permitted.
132
133           Example, show when "/etc/passwd" gets accessed and/or modified
134           once:
135
136              $inotify->watch ("/etc/passwd", IN_ACCESS | IN_MODIFY, sub {
137                 my $e = shift;
138                 print "$e->{w}{name} was accessed\n" if $e->IN_ACCESS;
139                 print "$e->{w}{name} was modified\n" if $e->IN_MODIFY;
140                 print "$e->{w}{name} is no longer mounted\n" if $e->IN_UNMOUNT;
141                 print "events for $e->{w}{name} have been lost\n" if $e->IN_Q_OVERFLOW;
142
143                 $e->w->cancel;
144              });
145
146       $inotify->fileno
147           Returns the fileno for this notify object. You are responsible for
148           calling the "poll" method when this fileno becomes ready for
149           reading.
150
151       $inotify->blocking ($blocking)
152           Clears ($blocking true) or sets ($blocking false) the "O_NONBLOCK"
153           flag on the file descriptor.
154
155       $count = $inotify->poll
156           Reads events from the kernel and handles them. If the notify fileno
157           is blocking (the default), then this method waits for at least one
158           event (and thus returns true unless an error occurs). Otherwise it
159           returns immediately when no pending events could be read.
160
161           Returns the count of events that have been handled.
162
163       $count = $inotify->read
164           Reads events from the kernel. Blocks in blocking mode (default)
165           until any event arrives. Returns list of "Linux::Inotify2::Event"
166           objects or empty list if none (non-blocking mode) or error occured
167           ($! should be checked).
168
169   The Linux::Inotify2::Event Class
170       Objects of this class are handed as first argument to the watch
171       callback. It has the following members and methods:
172
173       $event->w
174       $event->{w}
175           The watcher object for this event.
176
177       $event->name
178       $event->{name}
179           The path of the filesystem object, relative to the watch name.
180
181       $watch->fullname
182           Returns the "full" name of the relevant object, i.e. including the
183           "name" member of the watcher (if the the watch is on a directory
184           and a dir entry is affected), or simply the "name" member itself
185           when the object is the watch object itself.
186
187       $event->mask
188       $event->{mask}
189           The received event mask. In addition the the events described for
190           "$inotify-"watch>, the following flags (exported by default) can be
191           set:
192
193            IN_ISDIR             event object is a directory
194            IN_Q_OVERFLOW        event queue overflowed
195
196            # when any of the following flags are set,
197            # then watchers for this event are automatically canceled
198            IN_UNMOUNT           filesystem for watch'ed object was unmounted
199            IN_IGNORED           file was ignored/is gone (no more events are delivered)
200            IN_ONESHOT           only one event was generated
201
202       $event->IN_xxx
203           Returns a boolean that returns true if the event mask matches the
204           event. All of the "IN_xxx" constants can be used as methods.
205
206       $event->cookie
207       $event->{cookie}
208           The event cookie to "synchronize two events". Normally zero, this
209           value is set when two events relating to the same file are
210           generated. As far as I know, this only happens for "IN_MOVED_FROM"
211           and "IN_MOVED_TO" events, to identify the old and new name of a
212           file.
213
214   The Linux::Inotify2::Watch Class
215       Watch objects are created by calling the "watch" method of a notifier.
216
217       It has the following members and methods:
218
219       $watch->name
220       $watch->{name}
221           The name as specified in the "watch" call. For the object itself,
222           this is the empty string.  For directory watches, this is the name
223           of the entry without leading path elements.
224
225       $watch->mask
226       $watch->{mask}
227           The mask as specified in the "watch" call.
228
229       $watch->cb ([new callback])
230       $watch->{cb}
231           The callback as specified in the "watch" call. Can optionally be
232           changed.
233
234       $watch->cancel
235           Cancels/removes this watch. Future events, even if already queued
236           queued, will not be handled and resources will be freed.
237

SEE ALSO

239       AnyEvent, Linux::Inotify.
240

AUTHOR

242        Marc Lehmann <schmorp@schmorp.de>
243        http://home.schmorp.de/
244
245
246
247perl v5.12.0                      2009-09-21                       Inotify2(3)
Impressum