use Storable qw( nstore_fd retrieve_fd );

sub store_to_file {
    my ( $db, $data_ref ) = @_;

    sysopen( DF, $db, O_RDWR | O_CREAT, 0606 )
        or die "Can't open '$db', stopped: $!";
    flock( DF, LOCK_EX )
        or die
        "Can't get exclusive lock on '$db' for writing, stopped: $!";
    nstore_fd( $data_ref, *DF )
        or die "Can't store data: $@";
    truncate( DF, tell(DF) );
    close(DF);
    return 1;
}

sub retrieve_from_file {      # Certainly going to need this complementary function in the future,
                              # to read my students' information.
    my $db = shift;

    unless ( -e $db ) {
        store_to_file( [] );  # Initialize upon first-ever usage of this function if no student 
                              # information has been stored before, so it won't crash in that instance
                              # because the data file doesn't exist yet. Maybe there's an easier,
                              # softer way to instantiate the data file in this admittedly unusual
                              # scenario (which I managed to encounter last night).
    }

    open( DF, "< $db" )
        or die "Can't open '$db' for reading, stopped: $!";
    flock( DF, LOCK_SH )
        or die
        "Can't get shared lock on '$db' for reading, stopped: $!";
    my $data_ref = retrieve_fd(*DF);
    close(DF);
    return $data_ref;
}