script to convert file's cover art to an attachment in mka

conv.sh

#!/bin/bash
set -xe

mimetype(){
  file -i "$@" | grep -Eo '[a-z-]+/[a-z-]+;' | tr -d ';'
}

extes(){
  file -i "$@" | awk '{ print $2 }' | tr -d ';' | sed -E 's%^.+/%%'
}

for I in "$@" ; do
  ffmpeg -y -i "$I" -an -c:v copy /tmp/cover.jpg || rm -f /tmp/cover.jpg
  EXARGS=()
  if [[ -f /tmp/cover.jpg ]] ; then
    EXARGS+=(
      -attach /tmp/cover.jpg \
      -metadata:s:1 title="Album cover" -metadata:s:1 comment="Cover (front)" \
      -metadata:s:1 mimetype="$(mimetype /tmp/cover.jpg)" -metadata:s:1 filename="cover.$(extes /tmp/cover.jpg)"
    )
  fi
  ffmpeg -y -i "$I" -map 0:a:0 -map_metadata 0 -c copy -id3v2_version 3 \
    "${EXARGS[@]}" \
   "${I%.*}".mka
#  [[ ! -f /tmp/cover.jpg ]]
done