Linux and Perl module Linux::Inotify2 – unable to receive events

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.

notifywatch -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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