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_monitorsudo ./resource_monitor

cat /var/log/resource_monitor.log

ps -ef | grep resource_monitor

kill