anchor.diff:        shopt -s nullglob
   
         # Use all the default udev rules.
  -      cp ${udev}/libexec/rules.d/*.rules $out/
  +      cp -v ${udev}/libexec/rules.d/*.rules $out/
   
         # Set a reasonable $PATH for programs called by udev rules.
         echo 'ENV{PATH}="${pkgs.coreutils}/bin:${pkgs.gnused}/bin:${pkgs.utillinux}/bin"' > $out/00-path.rules
  
positive.code:       # modified by the write_{cd,net}_rules helpers called from
        # 75-cd-aliases-generator.rules and
        # 75-persistent-net-generator.rules.
        ln -s /var/lib/udev/rules.d/70-persistent-cd.rules $out/
        ln -s /var/lib/udev/rules.d/70-persistent-net.rules $out/
      ''; # */
    };
  
  
negative.code:       
        # Add the udev rules from other packages.
        for i in ${toString cfg.packages}; do
          echo "Add rules for package $i"
          for j in $i/*/udev/rules.d/*; do
            ln -sv $j $out/$(basename $j)
          done
        done
  
  