Inotify2(3) User Contributed Perl Documentation Inotify2(3)NAMELinux::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 EV, Glib, Tk, POE...)
my $inotify_w = AnyEvent->io (
fh => $inofity->fileno, 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/
perl v5.14.0 2009-09-21 Inotify2(3)
