New submission from STINNER Victor <victor.stin...@haypocalc.com>:
os.rename() is atomic on Linux, but on Windows it raises an error if the
destination does already exist.
Not atomic pseudo-code for Windows:
if exists(b):
unlink(b)
rename(a, b)
Windows offers different functions depending on the version:
- MoveFileTransacted(): atomic! version >= (Windows Vista, Windows Server 2008)
- ReplaceFile(): version >= Windows 2000
- MoveFileEx() with MOVEFILE_REPLACE_EXISTING and MOVEFILE_WRITE_THROUGH
flags: not atomic (eg. "If the file is to be moved to a different volume, the
function simulates the move by using the CopyFile and DeleteFile functions."),
version >= Windows 2000
I don't think that it's possible to write an atomic rename (file) function for
any OS, so it's only a "best effort" atomic function. The documentation will
give a list of OS on which the operation *is* atomic (eg. Linux).
Note: os.rename() uses MoveFileW() on Windows.
----------
components: Library (Lib), Windows
messages: 106587
nosy: haypo
priority: normal
severity: normal
status: open
title: Atomic function to rename a file
versions: Python 3.2
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue8828>
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