/*
 * call-seq:
 *   strio.readline(sep_string=$/)   -> string
 *
 * See IO#readline.
 */
static VALUE
strio_readline(argc, argv, self)
    int argc;
    VALUE *argv;
    VALUE self;
{
    VALUE line = strio_gets(argc, argv, self);
    if (NIL_P(line)) rb_eof_error();
    return line;
}