KENV_UNSET
ret = kenv(KENV_UNSET, env, NULL, 0);
case KENV_UNSET:
case KENV_UNSET:
(void)kenv(KENV_UNSET, KENV_VAR_NAME, NULL, 0);
(void)kenv(KENV_UNSET, KENV_VAR_NAME, NULL, 0);
error = kenv(KENV_UNSET, KENV_VAR_NAME, NULL, 0);
(void)kenv(KENV_UNSET, KENV_VAR_NAME, NULL, 0);