[Rd] Bug in file.access on Windows when using network shares
tom@@@k@liber@ @ending from gm@il@com
Tue Jul 3 10:21:56 CEST 2018
thank you for your report. In general one cannot know reliably in
advance whether reading a file will work, if nothing else, there are
possible race conditions with other applications and/or the system (e.g.
a service may lock the file, move it away temporarily, etc). The only
correct way to handle errors is try the read and catch errors. Please
note there is a disclaimer in ?file.access to this effect.
If you still want to report a bug in file.access, please provide an
example that does not require a package, and provide more details (what
do you think would be the correct behavior, etc). From looking at the
code, when winAccessW/GetFileSecurityW fails to retrieve information
about the file, file.access would signal an error, which seems to be a
fine behavior for me. It is not surprising to me that in some cases
(like working on a local copy of a file in a distributed file-system),
the OS would not know whether a file is readable/writeable before trying
out on/syncing the distributed version.
On 07/03/2018 01:11 AM, Nick Kennedy wrote:
> Dear R-Devel,
> I've run into an issue with a package (vcfR) that uses file.access to check
> a file is readable before opening it. The issue is actually in base R
> though. I've looked into the package code, and it calls file.access(path,
> mode = 4). I've created a minimal working example of the code in winAccessW
> from src/gnuwin32/extra.c, and the problem arises when GetFileSecurityW is
> called on shared files under certain circumstances.
> One situation I've seen it in are when a file is shared from a non-Windows
> host (e.g. Linux), which is similar to the situation documented at
> The other situation arises when a file is cached offline by Windows Offline
> files feature. The call to GetFileSecurityW works fine when the network is
> up (and so the file is being accessed from the share), but fails when the
> network is down and the file is being accessed from the offline files cache.
> Is there any reason that there is a custom function here? Windows supports
> the use of access (as is used on other OSes), although the ISO C++ _waccess
> would be preferred. This seems to work well even in situations where the
> current code does not.
> [[alternative HTML version deleted]]
> R-devel using r-project.org mailing list
More information about the R-devel