#!/bin/bash
for mkvfile in *.mkv; do
  filename=${mkvfile%.mkv}
  ffmpeg -i "${mkvfile}" -c:a copy -c:v copy -map 0:0 -map 0:1 -map 0:2 -map 0:3 -map 0:4 -movflags faststart "${filename}.mp4"
  if [[ ${?} == 0 ]]; then
    rm "${mkvfile}"
  fi
done