{ lib, stdenv, feh, findutils, gnugrep, coreutils, writeScript, backgrounds_directory ? "$HOME/Immagini/Sfondi" }:
let
  find = "${findutils}/bin/find";
  grep = "${gnugrep}/bin/grep";
  shuf = "${coreutils}/bin/shuf";
in
writeScript "update-background.sh" ''
  #!/bin/sh
  image=`${find} ${backgrounds_directory} -type f | ${grep} -v "/\." | ${shuf} -n 1`
  echo "image: $image"
  ${feh}/bin/feh --bg-fill --no-fehbg "$image"
''