Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]


Groups > comp.lang.python > #95833

Re: Does mkstemp open files only if they don't already exist?

Path csiph.com!goblin3!goblin1!goblin.stu.neva.ru!uio.no!news.tele.dk!news.tele.dk!small.news.tele.dk!newsgate.cistron.nl!newsgate.news.xs4all.nl!nzpost1.xs4all.net!not-for-mail
Return-Path <rosuav@gmail.com>
X-Original-To python-list@python.org
Delivered-To python-list@mail.python.org
X-Spam-Status OK 0.032
X-Spam-Evidence '*H*': 0.94; '*S*': 0.00; 'cc:addr:python-list': 0.09; 'subject:Does': 0.09; 'subject:don': 0.09; 'subject:files': 0.09; "system's": 0.09; 'assume': 0.11; 'wed,': 0.15; 'from:addr:rosuav': 0.16; 'from:name:chris angelico': 0.16; 'presume': 0.16; 'subject:already': 0.16; 'url:linux': 0.16; 'wrote:': 0.16; '2015': 0.20; 'cc:2**0': 0.20; 'cc:addr:python.org': 0.20; 'handles': 0.20; 'sep': 0.22; 'am,': 0.23; 'header:In-Reply-To:1': 0.24; "doesn't": 0.26; 'message- id:@mail.gmail.com': 0.27; "i'm": 0.30; 'another': 0.32; "d'aprano": 0.33; 'steven': 0.33; 'file': 0.34; 'that,': 0.34; 'received:google.com': 0.35; 'fail': 0.35; 'but': 0.36; 'depends': 0.36; 'subject:?': 0.36; 'subject:: ': 0.37; 'expect': 0.37; 'support,': 0.37; 'doing': 0.38; 'sure': 0.39; 'details,': 0.60; 'url:3': 0.60; 'chance': 0.60; 'your': 0.60; 'different': 0.63; 'safe': 0.63; 'here:': 0.63; 'due': 0.65; 'guaranteed': 0.67; 'chrisa': 0.84; 'flag.': 0.84; 'safe;': 0.84; 'to:none': 0.91
DKIM-Signature v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:cc :content-type; bh=3EXU/1pX0KYjMAmt5XSaimwYc8ismYjavxcIQrjE1/4=; b=rhw/G1zvgZXldPfT367OdJilpew27i0M/xuRwXMjoFxmCh6ghu3mktXRTSu9dZ0umR JZMbuVZjLcUyWvDv2kOnHRQygDNPytnjuWT1Go/XmYMMwi68c6ygPFNgevaPaNXKLvao 5U4El8K1uW2+HaWAmNBfsOixljgbyqRufGpOtZ4uNkF0wTDSQqVOk/1uhbnRVBpA7g8R 9yiO8bHqBHDJnr2oOAIXeWCPT0DvN5T3fvdo7D3eKL1Kk3DXEhSpLeJ4GN/P9IX2NOZ2 QMMySL6qtJqTfnPeyn4vkIrQ2g8rYiRIApxs9gvoopasmnC5GFWR8/jLuH2R8N3feQV9 LmwQ==
MIME-Version 1.0
X-Received by 10.50.50.198 with SMTP id e6mr2981930igo.13.1441119465534; Tue, 01 Sep 2015 07:57:45 -0700 (PDT)
In-Reply-To <55e5b9ec$0$1649$c3e8da3$5496439d@news.astraweb.com>
References <55e5b9ec$0$1649$c3e8da3$5496439d@news.astraweb.com>
Date Wed, 2 Sep 2015 00:57:45 +1000
Subject Re: Does mkstemp open files only if they don't already exist?
From Chris Angelico <rosuav@gmail.com>
Cc "python-list@python.org" <python-list@python.org>
Content-Type text/plain; charset=UTF-8
X-BeenThere python-list@python.org
X-Mailman-Version 2.1.20+
Precedence list
List-Id General discussion list for the Python programming language <python-list.python.org>
List-Unsubscribe <https://mail.python.org/mailman/options/python-list>, <mailto:python-list-request@python.org?subject=unsubscribe>
List-Archive <http://mail.python.org/pipermail/python-list/>
List-Post <mailto:python-list@python.org>
List-Help <mailto:python-list-request@python.org?subject=help>
List-Subscribe <https://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
Newsgroups comp.lang.python
Message-ID <mailman.45.1441119467.23514.python-list@python.org> (permalink)
Lines 18
NNTP-Posting-Host 2001:888:2000:d::a6
X-Trace 1441119467 news.xs4all.nl 23851 [2001:888:2000:d::a6]:49934
X-Complaints-To abuse@xs4all.nl
Xref csiph.com comp.lang.python:95833

Show key headers only | View raw


On Wed, Sep 2, 2015 at 12:45 AM, Steven D'Aprano <steve@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

Back to comp.lang.python | Previous | NextPrevious in thread | Next in thread | Find similar | Unroll thread


Thread

Does mkstemp open files only if they don't already exist? Steven D'Aprano <steve@pearwood.info> - 2015-09-02 00:45 +1000
  Re: Does mkstemp open files only if they don't already exist? Chris Angelico <rosuav@gmail.com> - 2015-09-02 00:57 +1000
  Re: Does mkstemp open files only if they don't already exist? Laura Creighton <lac@openend.se> - 2015-09-01 19:09 +0200

csiph-web