Tag Archive: inotify


Example code using Perl’s Linux::Inotify2 module with POE

Filed Under: Linux, OS, Perl by Jason L Froebe — Leave a comment
October 7, 2008

The examples in Linux::Inotify2 are for Event, Glib::IO and a manual loop. With the help of rcaputo, tye and Animator over on Perlmonks.org, I was able to get Linux::Inotify2 to work with POE. :)

#!/usr/bin/perl

use strict;
use warnings;

use Linux::Inotify2;
use POE;

$|++;

POE::Session->create
  ( inline_states =>
      { _start => sub {
            $_[KERNEL]->alias_set(‘notify’);
            $_[HEAP]{inotify} = new Linux::Inotify2
              or die "Unable to create new inotify object: $!";

            $_[HEAP]{inotify}->watch("/tmp/j", IN_CLOSE_WRITE, $_[SESSION]->postback("watch_hdlr"))
              or die "Unable to watch dir: $!";

            my $inotify_FH;
            open $inotify_FH, "< &=" . $_[HEAP]{inotify}->fileno or die "Can’t fdopen: $!\n";
            $_[KERNEL]->select_read( $inotify_FH, "inotify_poll" );
        },
        inotify_poll => sub {
          $_[HEAP]{inotify}->poll;
        },
        watch_hdlr => \&watch_hdlr,
      },
  );

sub watch_hdlr {
  my $event = $_[ARG1][0];

  my $name = $event->fullname;

  print "$name was accessed\n" if $event->IN_ACCESS;
  print "$name is no longer mounted\n" if $event->IN_UNMOUNT;
  print "$name is gone\n" if $event->IN_IGNORED;
  print "$name is new\n" if $event->IN_CLOSE_WRITE;
  print "events for $name have been lost\n" if $event->IN_Q_OVERFLOW;
}

POE::Kernel->run();

exit 0;

Create files for testing:

jason@jfroebe-laptop:~$ dd if=/dev/zero of=/tmp/j/p bs=1M count=2
2+0 records in
2+0 records out
2097152 bytes (2.1 MB) copied, 0.112971 s, 18.6 MB/s

Output

jason@jfroebe-laptop:~/bin$ ./test_poe_linux_inotify.pl
/tmp/j/p is new
/tmp/j/p is new
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Linux and Perl module Linux::Inotify2 – unable to receive events

Filed Under: Linux, OS, Perl by Jason L Froebe — Leave a comment
October 3, 2008

Hi all,

I’m trying to monitor a directory “/tmp/j” with Linux::Inotify2 to be notified when a file is accessed or when a (write) file descriptor is closed. So far, I haven’t been able to receive any notification events :( My guess is that I’m missing something simple.

#!/usr/bin/perl

use strict;
use warnings;

use Linux::Inotify2;

$|++;

my $inotify = new Linux::Inotify2
 or die "Unable to create new inotify object: $!";
 
1 while $inotify->poll;

$inotify->watch("/tmp/j", IN_ACCESS | IN_CLOSE_WRITE, sub {
 my $event = shift;
 
 my $name = $event->fullname;
 
 print "$name was accessed\n" if $event->IN_ACCESS;
 print "$name is no longer mounted\n" if $event->IN_UNMOUNT;
 print "$name is gone\n" if $event->IN_IGNORED;
 print "$name is new\n" if $event->IN_CLOSE_WRITE;
 print "events for $name have been lost\n" if $event->IN_Q_OVERFLOW;
 print "jjjj\n";
 
 $event->w->cancel;
}) or die "watch creation failed: $!";

$ dd if=/dev/zero of=/tmp/j/p bs=1M count=2
2+0 records in
2+0 records out
2097152 bytes (2.1 MB) copied, 0.101007 s, 20.8 MB/s

The script runs with no warnings.
linux kernel 2.6.24-19-generic

update:
To rule out an issue with the os, I tested with the inotifywatch of the inotify tools package. Running the dd command above several times.

$  inotifywatch -v -e access -e modify -t 20 -r /tmp/j
Establishing watches…
Setting up watch(es) on /tmp/j
OK, /tmp/j is now being watched.
Total of 1 watches.
Finished establishing watches, now collecting statistics.
Will listen for events for 20 seconds.
total  modify  filename
18     18      /tmp/j/

Update to the update:
Did more testing. Looks like the perldoc is wrong. The $inotify->poll needs to be called AFTER the $inotify->watch routines are set!
Thanks Animator for making me rethink how I was calling it. Working code:

#!/usr/bin/perl

use strict;
use warnings;

use Linux::Inotify2;

$|++;

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

$inotify->watch("/tmp/j", IN_ACCESS | IN_CLOSE_WRITE, sub {
 my $event = shift;
 
 my $name = $event->fullname;
 
 print "$name was accessed\n" if $event->IN_ACCESS;
 print "$name is no longer mounted\n" if $event->IN_UNMOUNT;
 print "$name is gone\n" if $event->IN_IGNORED;
 print "$name is new\n" if $event->IN_CLOSE_WRITE;
 print "events for $name have been lost\n" if $event->IN_Q_OVERFLOW;
 print "jjjj\n";

 # $event->w->cancel;
}) or die "watch creation failed: $!";

1 while $inotify->poll;

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