[Interest] QFileSystemWatcher and kate

Christian Ehrlicher Ch.Ehrlicher at gmx.de
Mon Sep 4 20:00:20 CEST 2017

Am 04.09.2017 um 19:59 schrieb Christian Ehrlicher:
> Am 04.09.2017 um 02:17 schrieb Thiago Macieira:
>> On Sunday, 3 September 2017 05:21:26 -03 Christian Ehrlicher wrote:
>>> Hi,
>>> I stumbled across a problem with QFileSystemWatcher on Linux. It looks
>>> like the inotify implementation does not honor a file replace action as
>>> expected.
>>> I'm adding a file with addPath() to watch for changes. But after I edit
>>> the file with kate (or any other editor which saves the file in a temp
>>> file and then renaming it to correct name), the QFileSystemWatcher does
>>> no longer watch for modifications...
>>> Looking in the bug tracker I also found a bug which describes the
>>> problem:
>>> https://bugreports.qt.io/browse/QTBUG-19350?jql=text%20~%20%22qfilesystemwat 
>>> cher%22 So it looks like this bug exists since inotify support was 
>>> added but
>>> the bug report was closed because it was not reproducible (maybe not 
>>> tested
>>> with inotify).
>>> Therefore my question - how to reopen this bug or should I file a 
>>> new one?
>> Strictly speaking, the behaviour you're seeing is the correct one: 
>> the file you
>> were watching was not modified. It was deleted. The new contents do 
>> not belong
>> to this file, but to another. If you were using tail -f to follow 
>> this file you
>> wouldn't see anything -- you need -F.
>> So to fix this issue (the strictly correct behaviour is not the 
>> expected one),
>> we need to add some other mechanism, like tail's flag above. That's 
>> because
>> we'll need more resources, as we need to check the directory for change.
> I did some tests. The windows implementation works as I (as a user of 
> QFileSystemWatcher) would have expected it. A copy/rename of a file 
> does not trigger an unwatch of the file.
> Inotify by itself does not provide such a behavior but maybe checking 
> for IN_DELETE_SELF/IN_IGNORED and re-adding the file could be an option?
> At least the different behavior of the windows and inotify backend 
> should be documented somewhere...
Ah, and btw: even vi is using the temporary file 'trick' to save a file.


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