test "$SUDO" || skip test "$UNAME" = "Darwin" && skip clean_scratch mkdir scratch/{foo,mnt} sudo mount -t tmpfs tmpfs scratch/mnt trap "sudo umount scratch/mnt" EXIT ln -s ../mnt scratch/foo/bar "$XTOUCH" scratch/mnt/baz ln -s ../mnt/baz scratch/foo/qux bfs_diff -L scratch -xdev