Read an M3U playlist file exported from Apple Music and relativize the paths, copying content from the original location to the relative location.

relativize-playlist.sh

#!/bin/bash -
#
# Given a playlist, expected in M3U format, copies
# the songs listed in said playlist to the given
# output directory, creating a new playlist using
# relative path names. This new folder can then be
# shared more easily.

playlist="$1"   # Path to an M3U file.
tmpfile="$(mktemp playlist.XXXXX)"
output_dir="$2" # Where to place the new playlist.

mkdir -p "${output_dir}"

file -k "${playlist}" | grep -q "CR line terminators"
[ $? -eq 0 ] && command -v dos2unix && \
    dos2unix --convmode mac --newfile "${playlist}" "${tmpfile}" || \
    echo <<EOF
CR line endings detected but no conversion utility found.
If this script fails, try again after installing 'dos2unix':

    port install dos2unix

or

    brew install dos2unix
EOF
    

while read line; do
    cp "$line" "${output_dir}"
    sed -e '/^\// s/.*\///' "${tmpfile}" > "${output_dir}/${output_dir}.m3u"
done < <(grep -E '^/' "${tmpfile}")