[Interest] QLockFile

[Graham Labdon]

Hi
Yes, just figured that out.

I need to get the lock then open the real file ....

Thanks for your help



-----Original Message-----
From: interest-bounces+graham.labdon=avalonsciences.com at qt-project.org [mailto:interest-bounces+graham.labdon=avalonsciences.com at qt-project.org] On Behalf Of André Somers
Sent: 23 February 2015 11:12
To: interest at qt-project.org
Subject: Re: [Interest] QLockFile

Graham Labdon schreef op 23-2-2015 om 12:06:
> Hi
>
> It seems that I needed to do a removeStaleLockFile when I had previously stopped my program via the debugger.
>
> I can now get a lock on the file, however, I cannot now open it for writing.
Why would you want to write to a lock file? A lock file protects a resource, it isn't the same as the resource itself. I have not checked, but I guess the implementation writes the pid of the process that created the file into the file, and expects this to be the only content of the file.
>
> This is the pseudo code for what I need to do
>
> Lock file
> Open file
> Write text
> Close file
> Unlock file
>
> Is this the correct way ? - I guess not as I cannot open the file for 
> writing
That is because the file is not yours to write to. It is owned by QLockFile. At least, that is how I understand it.

André

>
> Thanks
>
> -----Original Message-----
> From: interest-bounces+graham.labdon=avalonsciences.com at qt-project.org 
> [mailto:interest-bounces+graham.labdon=avalonsciences.com at qt-project.o
> rg] On Behalf Of André Somers
> Sent: 23 February 2015 10:44
> To: interest at qt-project.org
> Subject: Re: [Interest] QLockFile
>
> Graham Labdon schreef op 23-2-2015 om 11:36:
>> Hi
>>
>> QString path = "C:\jobs\Test1\job.xcfg"; QFile file(path);
>>
>> bool res = file.open(QIODevice::WriteOnly);
>>
>> here res is true
> But, the path is once again wrong. Use \\ or /, but not \ in string literal paths.
>> BUT
>>
>> QString path = "C:\jobs\Test1\job.xcfg"; QLockFile lock(path);
>>
>> bool res = lock.tryLock();
>>
>> here res is false
>>
>> BUT
>> QLockFile lock("C:\jobs\Test1\job.xcfg");
>>
>> bool res = lock.tryLock();
>>
>> here res is true!
> And you are sure that you are only locking once? And what does error() return when tryLock fails?
>
> André
>
> P.S. Please keep the discussion on the list, not in private mail.
>
>> Thanks for your time
>> -----Original Message-----
>> From: 
>> interest-bounces+graham.labdon=avalonsciences.com at qt-project.org
>> [mailto:interest-bounces+graham.labdon=avalonsciences.com at qt-project.
>> o
>> rg] On Behalf Of André Somers
>> Sent: 23 February 2015 10:15
>> To: interest at qt-project.org
>> Subject: Re: [Interest] QLockFile
>>
>> Graham Labdon schreef op 23-2-2015 om 11:10:
>>> Yes I am sure
>>> I have tried this with numerous file locations and different ways of constructing a QLockFile and the ONLY on that works is if I hard code an non escaped file path.
>> The non-escaped path will point to a different location than what you think it points to. That may be why that one succeeds.
>>
>> I have used QLockFile successfully (with "dynamic" paths). So, there really is something wrong with your way of using it, not with QLockFile itself.
>>
>> Did you try opening a file yourself at the location you want from code using QFile and opening it write only? What happens if you do that?
>>
>> André
>>
>>> -----Original Message-----
>>> From: André Somers [mailto:andre at familiesomers.nl]
>>> Sent: 23 February 2015 10:07
>>> To: Graham Labdon
>>> Subject: Re: [Interest] QLockFile
>>>
>>> Graham Labdon schreef op 23-2-2015 om 11:00:
>>>> Hi
>>>> The filePath is definitely valid
>>>>
>>>> The only way I can get QLockFile to work at the moment is by hard coding an invalid c string as in my example.
>>>>
>>>> If I use double backslashes in the hard code version tryLock fails
>>>>
>>> Are you sure you can actually write at that location?
>>>
>>> André
>>>
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