Inotify2 + AnyEvent

Dear Monks, I have a perfectly working perl/Tk script that we use for network management. It runs on Centos 5.6 and perl version is 5.8.8 I installed a new PC running Centos 5.7 and perl 5.8.8. I made sure all perl modules the script needs are installed. But I keep on getting the following error on the new machine:

Unable to create sub named "" at /usr/lib/perl5/site_perl/5.8.8/i386-l
+inux-thread-multi/AnyEvent.pm line 1488.
[download]

The lines in the script relevant to this are:

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

# add watchers --watch the snmptrapd.log file
$watchObject = $inotify->watch ("/var/log/snmptrapd.log", IN_MODIFY, \
+&processTrap);

$inotify_w = AnyEvent->io (
                           fh => $inotify->fileno,
                           poll => 'r',
                           cb => sub {
                                      $inotify->poll ;
                                     },
                          );

MainLoop;
[download]

The sub processTrap is defined.If I comment the

$inotify_w= AnyEvent->io (...
[download]

line, the code does not give an error and quit. But obviously I need that line. Any wisdom is appreciated...

Comment on Inotify2 + AnyEvent Select or Download Code
Re: Inotify2 + AnyEvent by rcaputo (Chaplain) on Oct 04, 2011 at 16:19 UTC
You have Tk at your disposal. Have you tried using Tk's fileevents directly? See Tk::Event's documentation for some ideas. `-- Rocco Caputo - http://poe.perl.org/ - irc://irc.perl.org/poe`	[reply]
Re: Inotify2 + AnyEvent by zentara (Archbishop) on Oct 04, 2011 at 17:20 UTC
Just a guess from knowing how finicky calling subs by reference sometimes can be. Instead of `$watchObject = $inotify->watch ( "/var/log/snmptrapd.log", IN_MODIFY, \&processTrap);` [download] try `$watchObject = $inotify->watch ( "/var/log/snmptrapd.log", IN_MODIFY, &processTrap() ); or "/var/log/snmptrapd.log", IN_MODIFY, processTrap() ); or "/var/log/snmptrapd.log", IN_MODIFY, sub{ processTrap() } );` [download] anyways, experiment around with the way you call that sub. In the Ionotify2 docs, the examples show .... sub{ } notation, and I know Tk can get very fussy about the way subs are called. One tip, if you use &, include the (). I'm not really a human, but I play one on earth. Old Perl Programmer Haiku ................... flash japh	[reply] [d/l] [select]
Re^2: Inotify2 + AnyEvent (now ne later) by tye (Cardinal) on Oct 04, 2011 at 17:44 UTC
I'd use `\&processTrap`. The `sub { procesTrap() }` should also work, but I don't recommend using that with Tk because I find that it can leak memory (and I don't know if Inotify2 avoids that problem). The other two things you suggested don't pass in a reference to code to be called later; they just call the code right then and then pass in whatever that code returns. - tye	[reply] [d/l] [select]
Re^3: Inotify2 + AnyEvent (now ne later) by dlal66 (Acolyte) on Oct 04, 2011 at 19:16 UTC
Thank you gentlemen for replying. I tried the suggestions provided but they did not work. So I checked and saw that the script was working on the machine that had AnyEvent version 5.34 installed. I checked the version of AnyEvent on the machine that has the issue and saw that it was running version 7.02 of AnyEvent. So I downloaded the version 5.34 of AnyEvent and after installion, my application is running fine on the new machine. So I guess the version 7.02 introduced a bug. Thanks again for your replies.	[reply]
Re: Inotify2 + AnyEvent by zentara (Archbishop) on Oct 05, 2011 at 09:44 UTC
To amplify with a code example, look at this Tk code. When the code ref for the button callback is left hanging naked, it gets executed at creation time. I suspected that is what was happening in your Ionotify2 code, the naked coderef was been acted upon at creation time, giving the error can't find "". `#!/usr/bin/perl use warnings; use strict; use Tk; my $mw = new MainWindow; $mw->geometry("400x200"); my $button = $mw->Button(-text => "Sub test exit", # this naked coderef is incorrect, as it causes # the callback to be executed at button creation # time, instead of later at button press -command => \&callback(time), # below is correct method, put [] around coderef # -command => [ \&callback, time ], )->pack(); MainLoop; sub callback{ my $in = shift; print "$in exiting\n"; Tk::exit; } __END__` [download] I'm not really a human, but I play one on earth. Old Perl Programmer Haiku ................... flash japh	[reply] [d/l]
Re^2: Inotify2 + AnyEvent (naked code ref) by tye (Cardinal) on Oct 05, 2011 at 16:08 UTC
No, `\&callback(time)` is not a "naked code ref". Yes, the similar-looking `\&callback` is a code ref, but adding `(time)` on the end changes the parsing to `\(&callback(time))`, that is, a call to `callback(time)` but ignoring prototypes and then returning reference(s) to the returned scalar value(s). - tye	[reply] [d/l] [select]
Re^3: Inotify2 + AnyEvent (naked code ref) by zentara (Archbishop) on Oct 05, 2011 at 20:31 UTC
I know you are smarter than me about this stuff, but even without adding (time), to the coderef `# -command => \&callback(time), -command => \&callback,` [download] still executes the sub callback at button creation time, causing a pre-mature exit, and crash. I'm not really a human, but I play one on earth. Old Perl Programmer Haiku ................... flash japh	[reply] [d/l]
Re^4: Inotify2 + AnyEvent (naked code ref) by tye (Cardinal) on Oct 05, 2011 at 21:05 UTC
Re^5: Inotify2 + AnyEvent (naked code ref) by zentara (Archbishop) on Oct 06, 2011 at 10:06 UTC
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Inotify2 + AnyEvent

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