简单的处理定时任务的守护进程

#include <stdio.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <pwd.h>
#include <time.h>
#include <signal.h>
#include <sys/wait.h>



int daemon(int, int);
char *daemon_log = "/u01/log/daemon.log";
int add_log(char*, char*);
void sig_handler(int);
void restart_sleep(int);
int is_daemon = 1;
int is_root = 1;


int main()
{
    fprintf(stdout, "daemon start\n");    
    int ret;
    //是否切换到普通用户
    if (!is_root) {
        if (getuid() == 0 || geteuid() == 0) {
            char *username = "flynetcn";
            struct passwd *pw;
            if ((pw = getpwnam(username)) == 0) {
                fprintf(stderr, "can't find the user %s\n", username);
                return 1;
            }
            if (setgid(pw->pw_gid) < 0 || setuid(pw->pw_uid) < 0) {
                fprintf(stderr, "failed to assume identity of user %s\n", username);
                return 1;
            }
        }
    }
    //防止僵死子进程
    struct sigaction sa, oldsa;
    sa.sa_handler = sig_handler;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = SA_RESTART;
    if (sigaction(SIGCHLD, &sa, &oldsa) == -1) {
        fprintf(stderr, "sigaction(SIGCHLD) error\n");
        return 1;
    }
    //切换到守护进程
    if (is_daemon) {
        ret = daemon(1, 0);
        if (ret == -1) {
            fprintf(stderr, "failed to daemon\n");
            return 1;
        }
    }



    /**
     * do something
     */

    int crontimers[3][2];
    //task 1
    crontimers[0][0] = 3;
    crontimers[0][1] = 6;
    //task 2
    crontimers[1][0] = -1;
    crontimers[1][1] = 6;
    //task 3
    crontimers[2][0] = -1;
    crontimers[2][1] = 36;
    //tasks comm
    char *croncomm[3];
    croncomm[0] = "echo task1 >> /dev/null 2>&1";
    croncomm[1] = "echo task2 >> /dev/null 2>&1";
    croncomm[2] = "echo task3 >> /dev/null 2>&1";

    char buf[1024];
    char tbuf[50];
    time_t timestamp;
    struct tm *now;
    int time_left;
    int cron_num;
    cron_num = sizeof(croncomm)/sizeof(char*);
    int hok, i;
    while (1) {
        timestamp = time(NULL);
        now = localtime(&timestamp);
        strftime(tbuf, 30, "%Y-%m-%d %H:%M:%S", now);
        //
        sprintf(buf, "%s ------\n", tbuf);
        add_log(buf, daemon_log);
        for (i=0; i<cron_num; i++) {
            hok=0;
            sprintf(buf, "task %d :\n", i);
            add_log(buf, daemon_log);
            if (crontimers[i][0]==-1 || now->tm_hour==crontimers[i][0]) {
                hok = 1;
                add_log("hok\n", daemon_log);
            } else {
                continue;
            }
            if (crontimers[i][1]==now->tm_min && croncomm[i]) {
                add_log("mok\n", daemon_log);
                sprintf(buf, "run %s\n", croncomm[i]);
                add_log(buf, daemon_log);
                ret = fork();
                if (ret == 0) {
                    system(croncomm[i]);
                    exit(0);
                }
            }
        }
        timestamp = time(NULL);
        now = localtime(&timestamp);
        time_left = 60 - now->tm_sec;
        restart_sleep(time_left);
    }

    /**
     * end
     */


}


int add_log(char *str, char *logfile)
{
    FILE *fp;
    if ((fp = fopen(logfile, "a")) == NULL) {
        return -1;
    }
    if (!(*str) || fputs(str, fp)==EOF) {
        fclose(fp);
        return -1;
    }
    fflush(fp);
    fclose(fp);
    return 0;
}


int daemon(int nochdir, int noclose)
{
    int fd, ret;
    ret = fork();
    switch (ret) {
        case -1: return -1;
        case 0: break;
        default: exit(0);
    }

    if (setsid() == -1)
        return -1;

    if (nochdir == 0) {
        if(chdir("/") != 0) {
            perror("chdir");
            return -1;
        }
    }

    if (noclose == 0 && (fd = open("/dev/null", O_RDWR, 0)) != -1) {
        if(dup2(fd, STDIN_FILENO) < 0) {
            perror("dup2 stdin");
            return -1;
        }
        if(dup2(fd, STDOUT_FILENO) < 0) {
            perror("dup2 stdout");
            return -1;
        }
        if(dup2(fd, STDERR_FILENO) < 0) {
            perror("dup2 stderr");
            return -1;
        }

        if (fd > STDERR_FILENO) {
            if(close(fd) < 0) {
                perror("close");
                return -1;
            }
        }
    }
    return 0;
}


void sig_handler(int sig)
{
    if (sig == SIGCHLD) {
        int status;
        pid_t pid;
        pid = wait(&status);
    }
}

//防止被信号中断
void restart_sleep(int sec)
{
    int left;
    left = sec;
    while (left > 0) {
        left = sleep(left);
    }
}