On 10/19/20 9:52 AM, Gregory P. Smith wrote: > > > On Mon, Oct 19, 2020 at 6:28 AM Ivan Pozdeev via Python-Dev > <python-dev@python.org <mailto:python-dev@python.org>> wrote: > > > On 19.10.2020 14:47, Steve Dower wrote: > > On 19Oct2020 1242, Steve Dower wrote: > >> On 15Oct2020 2239, Rob Cliffe via Python-Dev wrote: > >>> TLDR: In os.scandir directory entries, atime is always a copy of > mtime rather than the actual access time. > >> > >> Correction - os.stat() updates the access time to _now_, while > os.scandir() returns the last access time without updating it. > > > > Let me correct myself first :) > > > > *Windows* has decided not to update file access time metadata *in > directory entries* on reads. os.stat() always[1] looks at the file > entry > > metadata, while os.scandir() always looks at the directory entry > metadata. > > Is this behavior documented somewhere? > > Such weirdness certaintly something that needs to be documented but > I really don't like describing such quirks that are out of our control > and may be subject to change in Python documentation. So we should > only consider doing so if there are no other options. > > > I'm sure this is covered in MSDN. Linking to that if it has it in a > concise explanation would make sense from a note in our docs. > > If I'm understanding Steve correctly this is due to Windows/NTFS storing > the access time potentially redundantly in two different places. One > within the directory entry itself and one with the file's own metadata. > Those of us with a traditional posix filesystem background may raise > eyeballs at this duplication, seeing a directory as a place that merely > maps names to inodes with the inode structure (equiv: file entry > metadata) being the sole source of truth. Which ones get updated when > and by what actions is up to the OS. > > So yes, just document the "quirk" as an intended OS behavior. This is > one reason scandir() can return additional information on windows vs > what it can return on posix. The entire point of scandir() is to return > as much as possible from the directory without triggering reads of the > inodes/file-entry-metadata. :) > > -gps
depending on atimes isn't a consistently reliable mechanism anyway, since filesystems on Linux et. al. are allowed to be mounted so as to not independently update access times. _______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-le...@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/QXNHYK6NDECISIOZVO4BCW2O6UXRZJGO/ Code of Conduct: http://python.org/psf/codeofconduct/
