In a message of Wed, 02 Sep 2015 00:57:45 +1000, Chris Angelico writes: >On Wed, Sep 2, 2015 at 12:45 AM, Steven D'Aprano <st...@pearwood.info> wrote: >> I assume the answer is "Yes", but is it safe to expect that >> tempfile.mkstemp() will only create a file that doesn't already exist? I >> presume that there's no chance of it over-writing an existing file (say, >> due to a race-condition). > >It depends on OS support, but with that, yes, it is guaranteed to be >safe; the file is opened with an exclusivity flag. Check your system's >man pages for details, or here: > >http://linux.die.net/man/3/open > >O_EXCL|O_CREATE makes an "atomic file creation" operation which will >fail if another process is doing the same thing. I'm not sure how >mkstemp() handles that failure, but my guess/expectation is that it >would pick a different file name and try again. > >ChrisA >-- >https://mail.python.org/mailman/listinfo/python-list
I remember discussion on the mercurial mailing list about somebody who had a problem with this in conjunction with a virus scanner that really wanted to get in and do things to the poor temp files. see: https://selenic.com/pipermail/mercurial-devel/2009-February/010197.html for a very, very long thread about it. Apparantly, you can get windows to complain that you cannot create a file because it already exists, and it doesn't go back and try this again for you. But at the time I found the discussion puzzling, as my thought was 'why are these people using mkstemp directly, instead of tempfile.NamedTemporaryFile which seems to be what they want. But I found this thread looking for a different problem with a mercurial repository that we had that was corrupted, a year or so after the thread was written, so I didn't want to go back and ask them about it _then_. Then in the general excitement --"Your raid system is buggy! It is inserting sludge in your files!" I forgot about this puzzlement. Until now. Laura -- https://mail.python.org/mailman/listinfo/python-list