On Tue, 21 May 2024 at 03:44, Chet Ramey <chet.ra...@case.edu> wrote:
> On 5/17/24 1:15 PM, Robert Elz wrote: > > > | If `nosort' means no sorting, there is no imposed ordering, and > ascending > > | and descending are meaningless. > > > > Sure, but directory order, and reverse directory order aren't (and that's > > just a difference between the order in which you create the list as each > > new dirent is read from the directory - does it go at the head or tail). > > That's changing from one random order to another. > In the *general* case yes, the order should be treated as random. For example, readdir on a Linux ext4 fs returns directory entries in pseudo-random order; this is necessary to allow successive readdir calls to traverse a large directory, without skipping or repeating an existing entries, and without locking (so allowing additions, removals, and renamings to continue). (Connected to this, file positions returned by lseek(dir_fd, 0, SEEK_CUR) are pseudorandom numbers identifying the next directory entry to be fetched, not an indication of bytes read so far.) But it's not *always* random. For example, readdir on Linux's /proc/$pid/fd returns filedescriptors in ascending numerical order; likewise readdir on /proc returns process IDs in ascending numerical order (preceded by a bunch of other stuff, in an order that's well-defined in the kernel though perhaps not obvious to most users). Reversing those could be useful to some people. -Martin
