Convert Apple Books or iTunes Books to general EPUB format

convert_to_epub.sh

#!/usr/bin/env bash

for f in *.epub; do
  if [ -d "$f" ]; then
    echo "Converting: $f"

    cd "$f"

    find . -name "iTunesMetadata*.plist" -delete 2>/dev/null
    zip -0X "../tmp.epub" mimetype >/dev/null
    zip -rDX9 "../tmp.epub" * -x "*.DS_Store" -x mimetype >/dev/null

    cd ..
    rm -rf "$f"
    mv tmp.epub "$f"
  elif [[ $(unzip -l "$f" 2>/dev/null | grep iTunesMetadata) == "" ]]; then
    echo "Already clean: $f"
  else
    echo "Unexpected file: $f"
  fi
done