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

This script (written for the ash in Android Honeycomb, which is missing many POSIX features) is roughly equivalent to find ., except that it omits empty directories. (The omission is intentional; if you'd rather see them too, change flagset hasfiles to true or something like that.)

Challenges included working without test (aka [), including not only an inability to write if [ -d "$foo" ] ... but also missing if [ "$v" = something ] !

Also some ugliness with globbing, since we have to implement bash's nullglob and dotglob. There's also no ${!indirect} support. And I hate not having real lexical scope.

Yeah that's all.

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.