bunch of mp4's to mkvs

#!/bin/sh

if [ -n "$(find -name *.mp4)" ]
then
  echo -e "\nContains .mp4 files, doing magic.\n"
else
  echo -e "\nNo mp4 files to convert\n"
  exit 0
fi


conversion_list=$(find -name *.mp4)
for conversion_item in $conversion_list; do
        printf '%s -> %2s\n' "$conversion_item" "${conversion_item::-4}.mkv"
        HandBrakeCLI -i $conversion_item --preset Normal -f av_mkv --output "${conversion_item::-4}.mkv"
done