[prev in list] [next in list] [prev in thread] [next in thread] 

List:       pykde
Subject:    Re: [PyQt] QFileSystemWatcher triggering too many signals
From:       Giuseppe Corbelli <giuseppe.corbelli () copanitalia ! com>
Date:       2013-01-21 10:01:38
Message-ID: 50FD1202.7040403 () copanitalia ! com
[Download RAW message or body]

On 21/01/2013 08:49, Lars Beiderbecke wrote:
> Hello,
>
> I'm trying to watch a file for changes using QFileSystemWatcher:
>
> class MainWindow(QtGui.QMainWindow):
>
>      def __init__(self,parent,args=None):
>          QtGui.QMainWindow.__init__(self)
>          self.count = 0
>          self.watcher = QtCore.QFileSystemWatcher();
>          self.watcher.addPath("myfile");
>          self.connect(self.watcher, QtCore.SIGNAL("fileChanged(const
> QString&)"), self.check)
>
>      def check(self, file = "*"):
>          self.count += 1
>          print "Modified:", str(file), " #", self.count
>
> This works, more or less, as for every
>
> $ touch myfile
>
> I get exactly one invocation of check().  If the changes are larger,
> however, I get an excessive amount of invocations.  Some examples:
>
> $ dd if=/dev/urandom of=sample bs=1k count=100
> $ cp sample myfile
> ->  4 invocations
> $ vi myfile  # replacing first char, then :wq
> ->  21 invocations
> $ joe myfile  # ditto
> ->  11 invocations
> $ touch myfile
> ->  1 invocations
> $ cat sample>  watched
> ->  3 invocations
> $ cat sample sample>  watched
> ->  6 invocations
>
> Now I realize that editors may do weird things to files, but cp and
> cat? Is this behavior considered normal?

No answer on top of my mind, but I'd run all the commands (cp, vi, jo, cat) 
under strace and see all the related syscalls. Won't be surprised if the 
*notify system has some hooks related to common syscalls.

-- 
             Giuseppe Corbelli
WASP Software Engineer, Copan Italia S.p.A
Phone: +390303666318  Fax: +390302659932
E-mail: giuseppe.corbelli@copanitalia.com
_______________________________________________
PyQt mailing list    PyQt@riverbankcomputing.com
http://www.riverbankcomputing.com/mailman/listinfo/pyqt
[prev in list] [next in list] [prev in thread] [next in thread]