On Wed, May 29, 2019 at 10:07:38PM +0700, Tom Hale wrote:Ifsomebody can create a file named link_name between unlink and symlink, he can also remove and create a file named link_name after symlink.
I tbink there are some corner cases that can give different results if the symlink is not atomic. For example: Process A wants to symlink f1 --> f2, replacing any existing f1. Process B wants to create f1 if it doesn't already exist, or update it if it does. If f1 is a symlink, the file it's linked to should be updated. The end result should be that f1 exists and is a symlink to f2. If the symlink is not atomic, this can happen: 1. Process A sees that f1 already exists and deletes it. 2. Process B sees that f1 does not exist and creates a new file called f1. 3. Process A tries to symlink f1 to f2, which fails because there is now an existing file called f1. This violates the postcondition, because f1 is not a symlink to f2. -- Greg _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/
