sysctl_handle_string
error = sysctl_handle_string(oidp, an_conf, sizeof(an_conf), req);
error = sysctl_handle_string(oidp, an_conf_cache,
rc = sysctl_handle_string(oidp, buf, sizeof(buf), req);
arg, len, sysctl_handle_string, "A", __DESCR(descr))