Clean up stale .sdr files from Kindle (paperwhite)

cleanup.sh

#!/bin/sh
# Call this from your 'documents' directory

set -eu

for d in *.sdr
do
  if [ -d "$d" -a ! -n "$(find . -maxdepth 1 -type f -name "${d%.sdr}*" -print -quit)" ]
  then
    echo "$d"
    rm -rf "$d"
  fi
done