Re: [PATCH] Use access() to check file existence in GetNewRelFileNode().

F_OK seems to be better than R_OK because we want to check file existence
(not read permission) before creating the relation file with the path
later.

2018-05-17 17:09 GMT+08:00 Michael Paquier <michael(at)paquier(dot)xyz>:

> On Thu, May 17, 2018 at 04:09:27PM +0800, Paul Guo wrote:
> > Previous code uses BasicOpenFile() + close().
> >
> > access() should be faster than BasicOpenFile()+close() and access()
> > should be more correct since BasicOpenFile() could fail for various
> > cases (e.g. due to file permission, etc) even the file exists.
>
> Failing because of file permissions would be correct. There have been
> cases in the past, particularly on Windows, where anti-virus softwares
> wildly scan files, causing EACCES on various points of the data folder.
>
> > access() is supported on Linux/Unix. I do not have a Windows dev
> > environment, but MSDN tells me that access() is supported on Windows also
> > and there have been access() call in the workspace, so I assume there is
> no
> > portability issue.
>
> Yes, access() is spread already in the core code.
>
> - fd = BasicOpenFile(rpath, O_RDONLY | PG_BINARY);
>
> - if (fd >= 0)
> + if (access(rpath, F_OK) == 0)
>
> What you are looking for here is R_OK, no?
> --
> Michael
>