#!/bin/sh
# Extract cover image from the given media (e.g. M4B or MP3)
for fn in "$@"; do
  cover_jpg="$(mktemp -u $(dirname "$fn")/cover-XXXXX.jpg)"
  if ffmpeg -v error -i "$fn" -map 0:v -map -0:V  -c copy "$cover_jpg"; then
    echo "$cover_jpg"
  else
    rm -f "$cover_jpg"
    echo "couldn't extract cover from $fn" >&2
  fi
done