On Wed, Oct 09, 2024 at 10:00:01PM +0200, Ralph Boehme via samba-technical wrote:
Hm, interesting find
But I guess this won't help as with POSIX you can open() a file with
O_APPEND but then still call pread/pwrite on the resulting fd.
Is that true ?
The open(2) man page only says:
O_APPEND
The file is opened in append mode. Before each write(2), the file offset is positioned at the end of
the file, as if with lseek(2). The modification of the file offset and the write operation are per‐
formed as a single atomic step.
Aha ! It's not true (at least on Linux :-).
The pwrite(2) man page says:
BUGS
POSIX requires that opening a file with the O_APPEND flag should have no effect on the location at which
pwrite() writes data. However, on Linux, if a file is opened with O_APPEND, pwrite() appends data to the
end of the file, regardless of the value of offset.
So FILE_APPEND_DATA|SYNCHRONIZE == O_APPEND, on Linux at least.
