Re: Best way to check file modification time?

[Stefan Monnier]

>> I can easily move the mod time checking to a position in the code that's
>> closer to the actual reading or saving of the file, but I suspect that
>> only reduces the problem, it doesn't eliminate it altogether. So I'm
>> wondering if there's a Right Way Ѣ to do this. If not, any advice on how
>> to reduce the risks as much as possible would be great!

You can't solve this without locking.
The mod-time check has to be done before writing (since writing is
conditional on the result of the mod-time check), you have a race:

   User A checks mod-time
   User B checks mod-time
   User A writes
   User B writes

And this applies no matter how/when the mod-time was originally acquired.


        Stefan