Re: inotify problem

[Perlbotics]

in reply to inotify problem

Same here (SuSE 11.4, Perl 5.14.1, Linux::Inotify2 V1.22) - works.

As AM already said, it depends on how you change the file and if you rename the original file during the process. Try the following changes, run stat file_to_watch before and after your experiment.

 ## my $w = $notify->watch ($file_to_watch, IN_MODIFY, \&on_change) or
+ die $!;
 my    $w = $notify->watch ($file_to_watch, IN_MODIFY | IN_MOVE_SELF, 
+\&on_change2) or die $!;

...
sub on_change2 {
  my($e) = @_;

  print $e->fullname, " changed ";
  print " and also moved!" if $e->IN_MOVE_SELF;
  print "\n";
}
 

E.g., if I mix edit the file using Emacs and echo, the program stops reporting changes. If I append to the Emacs backup file (file_to_watch~) the modifications are reported again. The original file is watched, regardless of the fact that it has been renamed.

You could monitor the (file-name-)changes (IN_MOVE_SELF) and just re-init the watcher to keep track of further changes applied to the file identified by its name, not by its inode.

[morgon]

Thanks for the suggestions, the problem is that when you get the event that the file has moved the copy does not yet exist (preventing a new watch), so you need to watch the directory as well...

Here what seems to work for me, any improvements welcome:

 
use strict;

use Linux::Inotify2;
use File::Basename qw(dirname);
use File::Spec;

$|++;

my ($file_to_watch)=@ARGV;

my $notify = Linux::Inotify2->new or die $!;

&setup_watch;

sub setup_watch {
  $notify->watch ($file_to_watch, IN_MODIFY | IN_MOVE_SELF, \&watch_fi
+le) or die $!;
}

sub watch_file {
  my($e)=@_;

  my $fn = $e->fullname;

  if($e->IN_MODIFY) {
     print "$fn changed\n";
  }

  if($e->IN_MOVE_SELF) {
     print "old $fn moved\n";
     $e->w->cancel;
     my $dir = dirname $fn;
     $notify->watch ($dir, IN_CREATE, \&watch_dir) or die $!;
  }
}

sub watch_dir {
  my($e)=@_;
  
   my $fn = File::Spec->canonpath($e->fullname);
   return unless $fn eq $file_to_watch;

   $e->w->cancel;
   print "$fn newly created (probably changed)\n";
   setup_watch;
}

while(1) { 
  my $n = $notify->poll; 
  print "handled $n events\n\n"; 
}