Re: [patch] pg_copy - a command for reliable WAL archiving

Greg Stark wrote:

> char path[PATH_MAX];
> fd = open("/path/to/dir", O_TMPFILE | O_RDWR,
> S_IRUSR | S_IWUSR);
>
> /* File I/O on 'fd'... */
>
> snprintf(path, PATH_MAX, "/proc/self/fd/%d", fd);
> linkat(AT_FDCWD, path, AT_FDCWD, "/path/for/file",
> AT_SYMLINK_FOLLOW);

Hmm, the real trick here is linkat(... "/proc/self/foobar"), not the
O_TMPFILE: you can have an open file descriptor to an "invisible" file
simply by creating a normal file and unlinking it. I looked at linkat()
yesterday but the idea of using /proc/self didn't occur to me. Nasty
trick :-( It seems linkat() is quite a bit more portable than
O_TMPFILE, fortunately ...

--
Álvaro Herrera http://www.2ndQuadrant.com/
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