Linux守护进程

#define LOG_FILE "/var/log/resource_monitor.log"
#define CONFIG_FILE "/etc/daemon_config.conf"
#define TMP_DIR "/tmp"

// 定义轮询时间
#define MONITOR_INTERVAL 30  // 资源监控间隔 30 秒
#define CLEANUP_INTERVAL 600 // 清理间隔 10 分钟

int keep_running = 1;
FILE *log_fp = NULL;

// 守护进程初始化函数
void daemonize() {
    pid_t pid;

    // 1. 创建子进程并终止父进程
    pid = fork();
    if (pid < 0) exit(EXIT_FAILURE);
    if (pid > 0) exit(EXIT_SUCCESS);  // 父进程退出

    // 2. 创建新的会话
    if (setsid() < 0) exit(EXIT_FAILURE);

    // 3. 忽略 SIGCHLD 信号
    signal(SIGCHLD, SIG_IGN);

    // 4. 再次 fork，防止守护进程重新获得终端
    pid = fork();
    if (pid < 0) exit(EXIT_FAILURE);
    if (pid > 0) exit(EXIT_SUCCESS);

    // 5. 更改工作目录到根目录
    chdir("/");

    // 6. 重设文件权限掩码
    umask(0);

    // 7. 关闭不再需要的文件描述符
    close(STDIN_FILENO);
    close(STDOUT_FILENO);
    close(STDERR_FILENO);

    // 8. 重定向标准输入、输出、错误到 /dev/null
    open("/dev/null", O_RDONLY);
    open("/dev/null", O_WRONLY);
    open("/dev/null", O_WRONLY);

    // 打开系统日志
    openlog("resource_daemon", LOG_PID, LOG_DAEMON);
}

// 捕获信号的处理函数
void handle_signal(int signal) {
    switch (signal) {
        case SIGHUP:
            syslog(LOG_INFO, "Reloading configuration file...");
            // 重新加载配置文件
            if (log_fp) {
                fclose(log_fp);
            }
            log_fp = fopen(LOG_FILE, "a");
            if (log_fp == NULL) {
                syslog(LOG_ERR, "Failed to open log file");
                exit(EXIT_FAILURE);
            }
            break;
        case SIGTERM:
            syslog(LOG_INFO, "Daemon is shutting down...");
            if (log_fp) {
                fclose(log_fp);
            }
            closelog();
            keep_running = 0;  // 设置标志位，结束主循环
            break;
    }
}

// 资源监控功能
void monitor_resources() {
    FILE *fp;
    char buffer[128];

    // 记录当前时间
    time_t now = time(NULL);
    fprintf(log_fp, "Timestamp: %s", ctime(&now));

    // 记录 CPU 和内存使用情况
    fp = popen("vmstat 1 2 | tail -1", "r");
    if (fp != NULL) {
        fgets(buffer, sizeof(buffer) - 1, fp);
        fprintf(log_fp, "CPU/Memory Usage: %s\n", buffer);
        pclose(fp);
    }

    // 记录磁盘使用情况
    fp = popen("df -h /", "r");
    if (fp != NULL) {
        while (fgets(buffer, sizeof(buffer) - 1, fp) != NULL) {
            fprintf(log_fp, "Disk Usage: %s", buffer);
        }
        pclose(fp);
    }

    fflush(log_fp);  // 确保日志刷新到文件
}

// 定时清理 /tmp 目录
void cleanup_tmp() {
    DIR *dir;
    struct dirent *entry;
    char file_path[256];

    dir = opendir(TMP_DIR);
    if (dir == NULL) {
        syslog(LOG_ERR, "Failed to open /tmp directory");
        return;
    }

    while ((entry = readdir(dir)) != NULL) {
        if (entry->d_type == DT_REG) {  // 只删除常规文件
            snprintf(file_path, sizeof(file_path), "%s/%s", TMP_DIR, entry->d_name);
            if (unlink(file_path) == 0) {
                syslog(LOG_INFO, "Deleted file: %s", file_path);
            } else {
                syslog(LOG_ERR, "Failed to delete file: %s", file_path);
            }
        }
    }

    closedir(dir);
}

int main() {
    daemonize();

    // 打开日志文件
    log_fp = fopen(LOG_FILE, "a");
    if (log_fp == NULL) {
        syslog(LOG_ERR, "Failed to open log file");
        exit(EXIT_FAILURE);
    }

    // 捕获信号处理
    signal(SIGTERM, handle_signal);  // 用于进程关闭
    signal(SIGHUP, handle_signal);   // 用于重新加载配置

    time_t last_cleanup = time(NULL);

    // 主循环
    while (keep_running) {
        monitor_resources();  // 监控系统资源

        // 检查是否需要清理 tmp 目录
        if (difftime(time(NULL), last_cleanup) >= CLEANUP_INTERVAL) {
            cleanup_tmp();
            last_cleanup = time(NULL);
        }

        // 等待 30 秒后继续
        sleep(MONITOR_INTERVAL);
    }

    // 清理资源并退出
    if (log_fp) {
        fclose(log_fp);
    }
    closelog();

    return 0;
}

gcc resource_monitor.c -o resource_monitor
sudo ./resource_monitor

cat /var/log/resource_monitor.log

ps -ef | grep resource_monitor

kill