Hi,
On 16/03/2021 16:51, John Reiser wrote:
On 3/16/21, David Howells wrote:
John Reiser <jreiser@xxxxxxxxxxxx> wrote:
See the manual page "man 2 getdents".
Um, which bit? I don't see anything obvious to that end.
On that manual page:
=====
The system call getdents() reads several linux_dirent structures from
the directory
referred to by the open file descriptor fd into the buffer pointed to
by dirp.
[snip]]
On success, the number of bytes read is returned.
=====
So the return value is related to the size of the directory; the sum
of the values
returned before End-Of-File should be quite close to the .st_size of
the directory.
If a program is walking through the directory, reading all the entries
via getdents64(),
then .st_size of the directory is the only thing known in advance
about the total size.
(Of course anything involving a directory can depend on concurrent
create/delete/rename
of files within the directory.)
If you are looking for a hint on how large a buffer to allocate, then
st_blksize is generally used as a hint for directory reads, or
otherwise, a fixed size buffer or a page or two. The st_size field is
meaningless for directories and you'll get all kinds of odd results
depending on the filesystem that is in use, so best avoided,
Steve.
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