OpenSSL::Engine#ctrl_cmd

static VALUE
ossl_engine_ctrl_cmd(int argc, VALUE *argv, VALUE self)
{
    ENGINE *e;
    VALUE cmd, val;
    int ret;

    GetEngine(self, e);
    rb_scan_args(argc, argv, "11", &cmd, &val);
    ret = ENGINE_ctrl_cmd_string(e, StringValueCStr(cmd),
                                 NIL_P(val) ? NULL : StringValueCStr(val), 0);
    if (!ret) ossl_raise(eEngineError, NULL);

    return self;
}