prune.sh

prune_old_backups() {
  [ -n "$backups_to_keep" ] || return
  local num_re="[0-9]+"
  [ "$backups_to_keep" =~ "$num_re" ] || { echo "Backups to keep needs to be a number"; return }
  num_of_backups=$(ls -l "$backup_dir" | wc -l)
  
  if [ "$num_of_backups" > "$backups_to_keep" ]; then
      echo "Pruning backups"
      dirs_to_remove=$(ls -t | awk "NR>$backups_to_keep")
      echo "would remove $dirs_to_remove"
      echo "echo $dir_to_remove | xargs rm -rf"
  fi
}