extract audio track from multiple .mp4 files

extract.sh

#!/bin/bash

eval "files=($(ls ./*/*))"
for f in "${files[@]}"; do
#   printf '%s\n' "$f"
#   printf '%s\n' './wangwangduimp3/'"$f"'.mp3'
    ffmpeg -i $f -map 0:a -acodec libmp3lame -y './wangwangduimp3/'"$f"'.mp3'
done