#!/bin/sh
set -xfu

drive="$1"
mountpoint="/media/sd-card-$(date +%s)"
backup_directory="$(pwd)"

trap clean EXIT
clean() {
  umount "$mountpoint"
  rmdir "$mountpoint"
  fsck.exfat "$drive"
}

filenames="$(fsck.exfat "$drive" 2>&1 | sed -nE "s/.* file '(.*?)' is not allocated.*/\1/p")"
mkdir "$mountpoint"
mount "$drive" "$mountpoint"

echo "$filenames" | while read -r filename; do
  find "$mountpoint" -type f -name "$filename" -exec mv {} "$backup_directory" \;
done