Downloads and converts a YouTube video to an MP3 file. Credit: https://superuser.com/questions/611881/converting-a-youtube-video-to-mp3-using-ffmpeg-without-youtube-dl

youtube-to-mp3.sh

#!/bin/bash
set -e

# dependencies:
# - youtube-dl: https://ytdl-org.github.io/youtube-dl/
# - ffmpeg: https://ffmpeg.org/

# make sure youtube-dl dep exists
if ! command -v youtube-dl &> /dev/null
then
    echo "required dependency youtube-dl not found, exiting."
    exit 1
fi

# $1 is an env variable for the URL of the YouTube video being downloaded
if [[ $1 ]]
then
  echo "Downloading and converting YouTube video for $1..."
  # -x = Convert video files to audio-only files
  # --audio-format mp3 = convert to mp3 file format
  youtube-dl -x --audio-format mp3 $1
  exit 0
else
  echo "usage: ./youtube-to-mp3.sh <url>"
  exit 1
fi