what does O_EXCL open flag do?

[martin at clubmed.hf.intel.com.ogc.edu]

Does anyone know what the O_EXCL flag for the open call is
supposed to do?  I have read the POSIX spec, but I don't quite
understand what the flag is for.  The only thing that
the POSIX spec says is that if O_EXCL and O_CREAT are set, open()
shall fail if the file exists.  What if just O_EXCL is set?

You can mail to me directly or post a followup...

Thanks...

                          
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