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Re: Why would chmod( ... ) fail with "No such file or directory" [message #173163 is a reply to message #173161]

Fri, 25 March 2011 13:29

Jerry Stuckle
Messages: 2598
Registered: September 2010

Karma:

Senior Member

On 3/25/2011 8:37 AM, Simon wrote:
> On 3/25/2011 12:31 PM, "Álvaro G. Vicario" wrote:
>> El 25/03/2011 10:35, Simon escribió/wrote:
>>> Hi,
>>>
>>> I have some code that creates a temp file, writes to it and then calls
>>> chmod(...) to make sure that the file has 0644 permissions.
>>>
>>> // -------------
>>> // pseudo code
>>> //
>>> $tmpfname = 'xyx'; // come from another function.
>>>
>>> if (!($fd = @fopen($tmpfname, 'wb')))
>>> {
>>> return false;
>>> }
>>>
>>> fwrite($fd, $data ); // the data comes from another function has well.
>>> no warnings given.
>>
>> fwrite() returns FALSE if there was an error, you don't need to rely on
>> getting warnings.
>>
>>> fclose($fd); // no warnings given.
>>
>> Same with fclose().
>>
>>> chmod( $tmpfname, 0644 ); <!-- error here with "No such file or
>>> directory"
>>> // -------------
>>>
>>> The issue I have is that it works _sometimes_, in fact, 99% of the time
>>> it works.
>>> But from time to time the log reports that the file does not exist.
>>>
>>> But how it is possible, if the file opened successfully with fopen(
>>> ... )
>>
>> Perhaps that $tmpfname string that comes from another function is not
>> always unique. If the file was created by another process, you may not
>> be its owner thus you don't have permission to change permissions, or
>> the other process may have removed it while you were writing it. There
>> are a number of tools that can prevent access to a file for security
>> reasons (from PHP's safe mode to SELInux) and you don't always get an
>> accurate error message.
>>
>
> It make a lot of sense, and yes, it is very possible that the name is
> not unique, but I wonder how I could prevent the error/warning message
> in the first place.
>
> I cannot add a file_exists(...) just before chmod(...) because between
> the call to file_exists(...) and chmod(...) I could loose ownership of
> the file.
>
> Maybe I could/should use a temp name, open that temp file, write to it,
> close it, chmod(...) it and then just rename it.
>
> That might be a little better, maybe.
>
> Simon
>

This is always a problem when you use temporary files for storage.

But here's a different question - what is it you're trying to accomplish?

--
==================
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Jerry Stuckle
JDS Computer Training Corp.
jstucklex(at)attglobal(dot)net
==================

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[Message index]

		Why would chmod( ... ) fail with "No such file or directory" By: Simon on Fri, 25 March 2011 09:35
		Re: Why would chmod( ... ) fail with "No such file or directory" By: alvaro.NOSPAMTHANX on Fri, 25 March 2011 10:31
		Re: Why would chmod( ... ) fail with "No such file or directory" By: Simon on Fri, 25 March 2011 12:37
		Re: Why would chmod( ... ) fail with "No such file or directory" By: alvaro.NOSPAMTHANX on Fri, 25 March 2011 12:52
		Re: Why would chmod( ... ) fail with "No such file or directory" By: Jerry Stuckle on Fri, 25 March 2011 13:29
		Re: Why would chmod( ... ) fail with "No such file or directory" By: Leonardo Azpurua on Fri, 25 March 2011 14:14
		Re: Why would chmod( ... ) fail with "No such file or directory" By: The Natural Philosoph on Fri, 25 March 2011 14:00
		Re: Why would chmod( ... ) fail with "No such file or directory" By: crankypuss on Fri, 25 March 2011 17:52
		Re: Why would chmod( ... ) fail with "No such file or directory" By: Twayne on Fri, 25 March 2011 23:20

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