Eric mailed the findutils list a while back to point out that POSIX will standardise a new -mount option for find which is similar to -xdev but differs in the way the mount point itself is handled. I believe that the POSIX nftw() library function also gets a new option FTW_XDEV,
Somewhat confusingly, System V did not behave in the way described in the POSIX standard. See for some additional background info: http://austingroupbugs.net/view.php?id=1133 (the POSIX issue about differing -xdev interpretations) https://savannah.gnu.org/bugs/?54745 (Eric's heads-up about that for findutils) https://savannah.gnu.org/bugs/index.php?42318 (an older but related bug report) Currently, find accepts the -xdev option and to implement this simply passes FTS_XDEV to fts(). Do the gnulib maintainers feel that the creation of the FTW_MOUNT/FTW_XDEV dichotomy in POSIX nftw() justifies an analogous thing in fts()? I think it's possible that there would be no efficiency consideration for find in particular, as GNU find will currently stat almost all the directories it searches in any case (from ftsfind.c): isdir = S_ISDIR(mode) || (FTS_D == ent->fts_info) || (FTS_DP == ent->fts_info) || (FTS_DC == ent->fts_info); if (isdir && (ent->fts_info == FTS_NSOK)) { /* This is a directory, but fts did not stat it, so * presumably would not be planning to search its * children. Force a stat of the file so that the * children can be checked. */ fts_set (p, ent, FTS_AGAIN); return; } One of the key difficulties for findutils would be testing; we can't create mount points in the regression tests, and selecting an already-existing one to use for a test seems a tricky proposition. Thanks, James.
