ddrescue on a directory recursively (using find) skipping existing equally sized targets preservering metadata

ddrfind.sh

#!/bin/bash
# ddrescue on a directory recursively (using find)
# skipping existing equally sized targets
# preservering metadata
# inspired by the-mikedavis ddrfind.fish

if [ -z $1 ] || [ ! -d $1 ] || [ -z $2 ] || [ ! -d $2 ]; then
	echo "Usage:   ddrfind.sh <input-dir> <output-dir-that-exists>"
	echo "Example: ddrfind.sh /Volumes/A/folder-to-rescue /Volumes/B"
	exit 1
fi

#sdir=${1##*/}
#echo "sdir=$sdir" #f.e. folder-to-rescue
spath=${1%/*}
#spathlen=${#spath}
#echo "spath=$spath ($spathlen)" #f.e. /Volumes/A

find $1 -print0 | while read -d $'\0' source
do
	# strip source path from left side
	target=${source#$spath} #f.e. folder-to-rescue/filename.txt
	#echo "target=$target"

        # source is directory
	if [ -d $source ]; then
		if [ ! -e "$2$target" ]; then
			echo "mkdir $2$target"
			#mkdir -p "$2$target"
		fi
        # source is file
	else
		# target does not exist
		#if [ ! -e "$2$target" ]; then
                # or size is different
		if [ ! -e "$2$target" ] || [ $(du -k "$source" | cut -f1) != $(du -k "$2$target" | cut -f1)  ]; then
			echo "rescueing $source $2$target"
			#sudo ddrescue -T 1 "$source" "$2$target" #forward
			sudo ddrescue -R -T 1 "$source" "$2$target" #reverse
			# stop on file io errors
			if [ $? -eq 1 ]; then
				exit $?
			fi
			# copy metadata
			sudo touch -r "$source" "$2$target"
		fi
	fi
done