Re: opening twice with O_RDWR

[Mike - EMAIL IGNORED]

On Sun, 31 Dec 2006 06:28:46 -0800, Paul Pluzhnikov wrote:

> Mike - EMAIL IGNORED <m_d_berger_1900@yahoo.com> writes:
> 
>> In the code fragment below, I would have expected a
>> failure on the second open,
> 
> Why would you expect that?
> 
>> I would like to generate a failure.  How can I do this?
> 
> Use O_EXCL (which exists *just* for that purpose).
> 
>> The file is usually, but not always
>> present before the program is run.
> 

I think not. From man 2 open:

   O_EXCL When used with O_CREAT, if the file  already  exists  it  is  an
          error  and  the open will fail. In this context, a symbolic
          link exists, regardless of where its points to.  


Since in my case, a preexisting file does not mean a failure, this
will not serve unless I use a second "locking file".  I quick test
has verified this. If, in the above, the word "exists" were changed
to "opened", my purpose would be served.

[...]

Mike.