子进程的输出重定向到父进程

int service_mgmt_start(struct service_base *service)
{
    pthread_mutex_lock(&(sg_service_mgmt.data_lock)); // lock
    if (service->running) {
        pthread_mutex_unlock(&(sg_service_mgmt.data_lock)); // unlock
        return 0;
    }
    if (service->prepare_handler) {
        int ret = service->prepare_handler(service);
        if (ret != 0) {
            RM_LOGE("service: %s prepare failed! code = %d", service->name, ret);
        }
    }

    RM_LOGI("service: %s prepare finished", service->name);

    int pid = fork();
    if (pid < 0) {
        perror("fork error:");
        pthread_mutex_unlock(&(sg_service_mgmt.data_lock)); // unlock
        return -1;
    }
    if (pid > 0) { /* parent */
        service->pid = pid;
        service->running = 1;
        RM_LOGI("fork success");

        if (!strstr(service->name, "bluetoothctl")) {
            waitpid(service->pid, NULL, 0);
            service->pid = 0;
            service->running = 0;
        }
        pthread_mutex_unlock(&(sg_service_mgmt.data_lock)); // unlock
        return 0;
    }
    /* child */
    pthread_mutex_unlock(&(sg_service_mgmt.data_lock)); // unlock
    // TODO: change output
    if (!strstr(service->name, "dnsmasq")) {
        int stdout_fd = open("/dev/null", O_WRONLY);
        int stderr_fd = open("/dev/null", O_WRONLY);
        dup2(stdout_fd, STDOUT_FILENO);
        dup2(stderr_fd, STDERR_FILENO);
        close(stdout_fd);
        close(stderr_fd);
    }

    execvp(service->argv[0], service->argv);
    exit(127);
}