Linux::Inotify2 - scalable directory/file change notification
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;
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 ; }
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.
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:
undef
$!
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: $!";
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.
$name
$mask
"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.
$cb
Linux::Inotify2::Event
The returned $watch object is of class Linux::Inotify2::Watch.
$watch
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:
/etc/passwd
$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; $e->w->cancel; });
Returns the fileno for this notify object. You are responsible for calling the poll method when this fileno becomes ready for reading.
poll
Clears ($blocking true) or sets ($blocking false) the O_NONBLOCK flag on the file descriptor.
O_NONBLOCK
Reads events from the kernel and handles them. If the notify fileno is blocking (the default), then this method waits for at least one event (and thus returns true unless an error occurs). Otherwise it returns immediately when no pending events could be read.
Returns the count of events that have been handled.
Reads events from the kernel. Blocks in blocking mode (default) until any event arrives. Returns list of Linux::Inotify2::Event objects or empty list if none (non-blocking mode) or error occured ($! should be checked).
Objects of this class are handed as first argument to the watch callback. It has the following members and methods:
The watcher object for this event.
The path of the filesystem object, relative to the watch name.
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.
name
The received event mask. In addition the the events described for $inotify-watch>, the following flags (exported by default) can be set:
$inotify-
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
Returns a boolean that returns true if the event mask matches the event. All of the IN_xxx constants can be used as methods.
IN_xxx
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.
IN_MOVED_FROM
IN_MOVED_TO
Watch objects are created by calling the watch method of a notifier.
watch
It has the following members and methods:
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.
The mask as specified in the watch call.
The callback as specified in the watch call. Can optionally be changed.
Cancels/removes this watch. Future events, even if already queued queued, will not be handled and resources will be freed.
AnyEvent, Linux::Inotify.
Marc Lehmann <schmorp@schmorp.de> http://home.schmorp.de/
To install Linux::Inotify2, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Linux::Inotify2
CPAN shell
perl -MCPAN -e shell install Linux::Inotify2
For more information on module installation, please visit the detailed CPAN module installation guide.