Roughly equivalent to "find .", only in less-than-POSIX ash

find-in-ash.noemptydirs.sh

#!/system/bin/sh

stat() {
    local lsout="$(ls -ld "$1" 2>/dev/null)"
    case "$lsout" in
	"") nex=1; fil= ; dir=  ;;
	d*) nex= ; fil= ; dir=1 ;;
	*)  nex= ; fil=1; dir=  ;;
    esac
}

nonempty() {
    case "$1" in
	"") return 1 ;;
	*)  return 0 ;;
    esac
}

flagset() {
    local vname="$1"
    local vval="$(eval "echo \$$vname")"
    nonempty "$vval"
}

forglob() {
    local root="$1"
    shift
    for ent in "$root"/* "$root"/.*; do
	case "$ent" in
	    */.) true ;;
	    */..) true ;;
	    *)
		# If the directory's empty, the glob expanded
		# to ".../*" which doesn't exist. Rule it out.
		stat "$ent"
		if ! flagset nex; then
		    cur="$ent"
		    eval "$*"
		fi
		;;
	esac
    done
}

oneent() {
    if flagset dir; then
	local d="$cur"
	hasfiles=
	forglob "$d" "hasfiles=1"
	if flagset hasfiles; then
	    echo "$d"
	    forglob "$d" oneent
	fi
    else
	echo "$cur"
    fi
}

cur=.
stat .
oneent

The use case is

# Get the list of files (and their parent dirs) on the sdcard
adb push find-in-ash.noemptydirs.sh /mnt/sdcard
adb shell
  cd /mnt/sdcard
  sh find-in-ash.noemptydirs.sh > filelst
  exit
adb pull /mnt/sdcard/filelst filelst.there

# Make a local copy of the sdcard, for backup
adb pull /mnt/sdcard/ sdcard

# Make sure we got everything
(cd sdcard && find .) > filelst.here
diff <(sort filelst.there) <(filelst.here)

(Yes, it sounds like it's just doing an extra check for paranoia, but adb actually missed some things the first time around. Not particularly encouraging.)

This would have been a lot simpler if toolbox (Android's BusyBox wanna-be) had tar, or if there was an obvious way to mount a Xoom's internal memory as USB Mass Storage. But this was fun, at least.