Generate the content

First create an empty directory to your iPod files, e. g.:

% mkdir ~/iPod

Then create a directory named music to place your songs:

% mkdir ~/iPod/music

Place all your songs in /music.

Generate the content based on iPod directory

% docker run -u $UID -w /ipod -v ~/iPod:/ipod dmitryrck/ipod-shuffle-4g -u -t -v /ipod

And sync all content of ~/iPod to your iPod.

Utils

Mount

# mount -t vfat /dev/disk/by-uuid/67C3-DCC4 -o uid=1000,gid=1000 /mnt

Create playlist for each directory

% find music -type f -iname '*m3u*' -exec rm '{}' \;

% find music -iname '*.mp3' \
  -execdir bash -c 'file="{}"; printf "%s\n" "${file##*/}" >> "${PWD##*/}.m3u"' \;

Replace space with _

perl-rename 'y/ /_/' *

Rename to lowcase

zmv '(*)' '${(L)1}'

perl-rename 'y/A-Z/a-z/' *

Convert m4a to mp3

% ffmpeg -i filename.m4a -acodec libmp3lame -ab 320k filename.mp3