Messages in this thread | | | Date | Sun, 31 Mar 2013 19:28:40 -0400 | From | Ric Wheeler <> | Subject | Re: openat(..., AT_UNLINKED) was Re: New copyfile system call - discuss before LSF? |
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On 03/31/2013 07:18 PM, Pavel Machek wrote: > Hi! > >>>>>> Take a look at how many actively used filesystems out there that have >>>>>> some variant of sillyrename(), and explain what you want to do in those >>>>>> cases. >>>>> Well. Yes, there are non-unix filesystems around. You have to deal >>>>> with silly files on them, and this will not be different. >>>> So this would be a local POSIX filesystem only solution to a problem >>>> that has yet to be formulated? >>> Problem is "clasical create temp file then delete it" is racy. See the >>> archives. That is useful & common operation. >> Which race are you concerned with exactly? >> >> User wants to test for a file with name "foo.txt" >> >> * create "foo.txt~" (or whatever) >> * write contents into "foo.txt~" >> * rename "foo.txt~" to "foo.txt" >> >> Until rename is done, the file does not exists and is not complete. >> You will potentially have a garbage file to clean up if the program >> (or system) crashes, but that is not racy in a classic sense, right? > Well. If people rsync from you, they will start fetching incomplete > foo.txt~. Plus the garbage issue.
That is not racy, just garbage (not trying to be pedantic, just trying to understand). I can see that the "~" file is annoying, but we have dealt with it for a *long* time :)
Until it has the right name (on either the source or target system for rsync), it is not the file you are looking for. > >> This is more of a garbage clean up issue? > Also. Plus sometimes you want temporary "file" that is > deleted. Terminals use it for history, etc...
There you would have a race, you can create a file and unlink it of course and still write to it, but you would have a potential empty file issue?
Ric
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