Read a playlist from a file using bash, while keeping input-priority for player

playlist-play.sh

#!/bin/bash

# Read the playlist in a line at-a-time from the 4th file descriptor.
# This preserves stdin for mpv below, so mpv can still receive
# keyboard commands.
while read -r -u 4 songPath; do
  duration=$(
    ffmpeg -i "$songPath" |&  ## use ffmpeg in info mode
    grep Duration |  ## use `cut` to parse the song duration
    cut -d, -f 1 |   ##   "Duration: 00:02:21.234"
    cut -d: -f 3,4 | ##   -> "02:21.234"
    cut -d. -f 1);   ## assumes no song is longer than 59 minutes.

  # Issue a notification to the desktop with the song path and duration.
  notify-send "Now playing: $songPath - $duration";

  # Play the song. `mpv` can receive most keyboard commands, except
  # for those involving the shift key for some reason.
  mpv --no-video $songPath;

# final step: redirect the contents of the playlist into file
# descriptor 4 so that `read` above can receive it. The playlist file
# must be titled "playlist" and must reside in the current working
# directory.
done 4< playlist