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Prevent unlink(...) warning

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  Prevent unlink(...) warning Simon <bad@example.com> - 2011-11-17 17:04 +0200
    Re: Prevent unlink(...) warning The Natural Philosopher <tnp@invalid.invalid> - 2011-11-17 15:18 +0000
      Re: Prevent unlink(...) warning Simon <bad@example.com> - 2011-11-17 19:21 +0200
        Re: Prevent unlink(...) warning The Natural Philosopher <tnp@invalid.invalid> - 2011-11-17 18:29 +0000
    Re: Prevent unlink(...) warning "Álvaro G. Vicario" <alvaro.NOSPAMTHANX@demogracia.com.invalid> - 2011-11-17 18:42 +0100
    Re: Prevent unlink(...) warning Jerry Stuckle <jstucklex@attglobal.net> - 2011-11-17 13:54 -0500

#3817 — Prevent unlink(...) warning

Hi,

I am having some race condition issues on my server when trying to 
delete a file.

//
function my_unlink( $filename )
{
   //  remove the old file
   clearstatcache(TRUE, $filename);
   if (file_exists($filename))
   {
     @unlink($filename);
   }
   else
   {
     return true;
   }

   clearstatcache(TRUE, $filename);
   return (!file_exists($filename));  // check it was deleted.
}
//

In some cases I get

unlink(/home/xxx/public_html/temp/yyy.zz) [function.unlink]: No such 
file or directory

How can I prevent the warning?

Thanks

Simon

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#3818

Simon wrote:
> Hi,
> 
> I am having some race condition issues on my server when trying to 
> delete a file.
> 

what makes you think its a race condition?

> //
> function my_unlink( $filename )
> {
>   //  remove the old file
>   clearstatcache(TRUE, $filename);
>   if (file_exists($filename))
>   {
>     @unlink($filename);
>   }
>   else
>   {
>     return true;
>   }
> 
>   clearstatcache(TRUE, $filename);
>   return (!file_exists($filename));  // check it was deleted.
> }
> //
> 

Why do you care about the stat cache?

> In some cases I get
> 
> unlink(/home/xxx/public_html/temp/yyy.zz) [function.unlink]: No such 
> file or directory
> 
> How can I prevent the warning?
> 
Why prevent it at all?

As long as the file is not there when you are finished - why not just 
unlink it anyway?

> Thanks
> 
> Simon
> 

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#3819

On 2011/11/17 05:18 PM, The Natural Philosopher wrote:
> Simon wrote:
>> Hi,
>>
>> I am having some race condition issues on my server when trying to
>> delete a file.
>>
>
> what makes you think its a race condition?

A guess really,

If I do:
...
if (file_exists($filename))
{

and followed by
...
   @unlink($filename);
}

And that gives me a

unlink(/home/xxx/public_html/temp/yyy.zz) [function.unlink]: No such 
file or directory

The something between file_exists(...) and @unlink(...) must have 
removed the file.
Either that or one of the two functions is not working as expected.

>
> Why do you care about the stat cache?
>

As per the doc, http://php.net/manual/en/function.clearstatcache.php, to 
make sure that file_exists($filename) does return a cached value.

>>
>> How can I prevent the warning?
>>
> Why prevent it at all?
>
> As long as the file is not there when you are finished - why not just
> unlink it anyway?
>

Because the warnings fill my logs and I aim for no warnings at all.

Simon

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#3821

Simon wrote:
> On 2011/11/17 05:18 PM, The Natural Philosopher wrote:
>> Simon wrote:
>>> Hi,
>>>
>>> I am having some race condition issues on my server when trying to
>>> delete a file.
>>>
>>
>> what makes you think its a race condition?
> 
> A guess really,
> 
> If I do:
> ...
> if (file_exists($filename))
> {
> 
> and followed by
> ...
>   @unlink($filename);
> }
> 
> And that gives me a
> 
> unlink(/home/xxx/public_html/temp/yyy.zz) [function.unlink]: No such 
> file or directory
> 
> The something between file_exists(...) and @unlink(...) must have 
> removed the file.
> Either that or one of the two functions is not working as expected.
> 

Hmm..what else CAN be deleting that file (unless you are doing the same 
thing twice)?

>>
>> Why do you care about the stat cache?
>>
> 
> As per the doc, http://php.net/manual/en/function.clearstatcache.php, to 
> make sure that file_exists($filename) does return a cached value.
> 
>>>
>>> How can I prevent the warning?
>>>
>> Why prevent it at all?
>>
>> As long as the file is not there when you are finished - why not just
>> unlink it anyway?
>>
> 
> Because the warnings fill my logs and I aim for no warnings at all.
> 

Well, that's reasonable..;-)
> Simon

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#3820

El 17/11/2011 16:04, Simon escribió/wrote:
> I am having some race condition issues on my server when trying to
> delete a file.
>
> //
> function my_unlink( $filename )
> {
> // remove the old file
> clearstatcache(TRUE, $filename);
> if (file_exists($filename))
> {
> @unlink($filename);
> }
> else
> {
> return true;
> }
>
> clearstatcache(TRUE, $filename);
> return (!file_exists($filename)); // check it was deleted.
> }
> //
>
> In some cases I get
>
> unlink(/home/xxx/public_html/temp/yyy.zz) [function.unlink]: No such
> file or directory
>
> How can I prevent the warning?


I can think of three possible approaches:

1. Try out flock() and find out whether it prevent other processes from 
removing the file and whether it allows _you_ to remove it.

2. Write a custom error handler and see if you can convert the warning 
into ErrorException. If you succeed, you can then try...catch around the 
unlink() call.

3. Keep the @ and live with it. I hate the error suppression operator as 
much as anyone but there're situations where trying to do without it is 
just not worth the effort.


-- 
-- http://alvaro.es - Álvaro G. Vicario - Burgos, Spain
-- Mi sitio sobre programación web: http://borrame.com
-- Mi web de humor satinado: http://www.demogracia.com
--

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#3822

On 11/17/2011 10:04 AM, Simon wrote:
> Hi,
>
> I am having some race condition issues on my server when trying to
> delete a file.
>
> //
> function my_unlink( $filename )
> {
> // remove the old file
> clearstatcache(TRUE, $filename);
> if (file_exists($filename))
> {
> @unlink($filename);
> }
> else
> {
> return true;
> }
>
> clearstatcache(TRUE, $filename);
> return (!file_exists($filename)); // check it was deleted.
> }
> //
>
> In some cases I get
>
> unlink(/home/xxx/public_html/temp/yyy.zz) [function.unlink]: No such
> file or directory
>
> How can I prevent the warning?
>
> Thanks
>
> Simon
>

In addition to what Álvaro said, if you're doing a lot of this in your 
scripts, I would suspect a database may be a better solution.

-- 
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstucklex@attglobal.net
==================

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