cron.c

这是一个我自己仿照linux下cron程序写的精简版的cron

        (void) snprintf(n, MAX_FNAME, CRON_TAB(User));
        if (!(crontab = fopen(n, "r"))) {
                /*no crontab before*/
                /*no such file or dir*/
                if (errno != ENOENT) {
                        perror(n);
                        snprintf(error,MAX_LINE,"%s: can not open file %s.",ProgramName,n);
                        log_err(error);
                        return(0);
                }
                fprintf(stderr, "no crontab for %s - using an empty one\n",User);
                if (!(crontab = fopen("/dev/null", "r"))) {
                        snprintf(error,MAX_LINE,"%s: can not open /dev/null.",ProgramName);
                        log_err(error);
                        return(0);
                }
        }
        del_rec();
        /*----------------------------------------------*/
        /*************** load the date ***************/
        while(fgets(line,MAX_LINE,crontab) != NULL) {
                if(!add_rec())
                        return 0;
                current_date = head;
                can_gets = 1;
                pt = 0;
                /****** to see if the line is an empty line or a comment line **/
                while(line[pt] == ' ' || line[pt] == '\t')
                        pt++;
                if(line[pt] == '#' || line[pt] == '\n')
                        continue;
                /*************** divide the date in to five part *****************/
                for(; i < 5; i++) {
                        finish = 0;
                        while(1) {
                                flag = get_next_token(buffer,line,&pt);
                                switch(flag) {
                                        case 1:
                                                if((num = check_number(buffer,i)) < 0) {
                                                        return 0;
                                                }
                                                record_it(current_date,i,num);
                                                finish = 1;
                                                break;
                                        case 2:
                                                record_it(current_date,i,'*');
                                                finish = 1;
                                                break;
                                        case 3:
                                                if((num = check_number(buffer,i)) < 0) {
                                                        return 0;
                                                }
                                                record_it(current_date,i,num);
                                                finish = 0;
                                                break;
                                        case 4:
                                        case 5:
                                        default:
                                                return 0;
                                                break;
                                }
                                if(finish)
                                        break;
                        }
                }
                strncpy(current_date->command,&line[pt],MAX_LINE);
                i = 0;
        }
        fclose(crontab);
        return(1);
}


void cron_sleep(int target)
{
        int seconds_to_wait;

        seconds_to_wait = (int)(target - time((time_t*)0)) + 1;

        if (seconds_to_wait > 0 && seconds_to_wait< 65)
                sleep((unsigned int) seconds_to_wait);
}

static int do_job(time_t current_time)
{
        struct tm *tm = localtime(&current_time);
        char error[MAX_LINE];
        date_rec * pt = head;

        while(pt) {
                if(/*pt->minute_rec[tm->tm_min] && pt->hour_rec[tm->tm_hour]
                             && pt->day_of_mon_rec[tm->tm_mday] && pt->mon_of_year_rec[tm->tm_mon]
                             && pt->day_of_week_rec[tm->tm_wday]*/
                        CHECK(pt->minute_rec,tm->tm_min)&&CHECK(pt->hour_rec,tm->tm_hour)&&
                        CHECK(pt->day_of_mon_rec,tm->tm_mday)&&CHECK(pt->mon_of_year_rec,tm->tm_mon)
                        &&CHECK(pt->day_of_week_rec,tm->tm_wday)) {
                        switch(fork()) {
                                case -1:
                                        snprintf(error,MAX_LINE,"%s: fork error.",ProgramName);
                                        log_err(error);
                                        return 0;
                                case 0:
                                        /* child */
                                        execlp("bash","bash","-c",pt->command,(char *)0);
                                        snprintf(error,MAX_LINE,"%s: execlp %s.",ProgramName,pt->command);
                                        log_err(error);
                                        break;
                                default:
                                        /* parent */
                                        break;
                        }
                }
                pt = pt->next;
        }
        return 1;
}

static void sigchld_handler(int x) {
	int save_errno = errno;
	int		waiter;
	pid_t		pid;

	for (;;) {
		pid = waitpid(-1, &waiter, WNOHANG);
		switch (pid) {
		case -1:
			errno = save_errno;
			return;
		case 0:
			errno = save_errno;
			return;
		default:
			break;
		}
	}
	errno = save_errno;
}



int main()
{
        /*---------------------------------------------------------------------------*/
        int ok = 1;
        int running_time;
        int modify_time;
        int check_time;
        int markfd;
        int check;
        char error[MAX_LINE];
        char n[MAX_FNAME];
        char * User;
        struct stat buf;
        struct passwd *pw;
        /*************** handle signal here ***************/
        //(void) signal(SIGCLD, SIG_IGN);
        (void) signal(SIGTERM, SIG_IGN);
	//(void) signal(SIGCHLD, sigchld_handler);




        //if(daemon_init() < 0)
        // log_err("Daemon fork fail");

        /*************** the body ***************/
        /* open the crontab */
        if (!(pw = getpwuid(getuid()))) {
                snprintf(error,MAX_LINE,"%s: your UID isn't in the passwd file.\n",
                         ProgramName);
                log_err(error);
                return(0);
        }
        /* dup the user id*/
        if (((User=strdup(pw->pw_name)) == NULL)) {
                snprintf(error,MAX_LINE, "%s: Memory allocation error\n",ProgramName);
                log_err(error);
                return(0);
        }

        (void) snprintf(n, MAX_FNAME, CRON_TAB(User));
        if((markfd = open(n,O_RDONLY, 0400)) == -1) {
                modify_time = time(0);
                check_time = modify_time;
        } else {
                /*************** get the last modify time the mark file ***************/
                if((check = fstat(markfd,&buf)) < 0) {
                        snprintf(error,MAX_LINE,"%s: stat fail!",ProgramName);
                        log_err(error);
                        exit(1);
                }
                close(markfd);
                modify_time = buf.st_mtime;
                check_time = modify_time;
        }
        /*************** load the command ***************/
        if(!load_rec()) {
                ok = 0;
                snprintf(error,MAX_LINE,"%s: load record from crontab fail!",ProgramName);
                log_err(error);
        }
        running_time = time(0);
        while(1) {
                if((markfd = open(n,O_RDONLY, 0400)) > 0) {
                        /******** check if there is any change of crontab **********/
                        if((check = fstat(markfd,&buf)) < 0) {
                                snprintf(error,MAX_LINE,"%s: stat fail!",ProgramName);
                                log_err(error);
                                exit(1);
                        }
                        check_time = buf.st_mtime;
                }
                /*************** if so load the command again ***************/
                if(modify_time != check_time) {
                        snprintf(error,MAX_LINE,"%s: load record from crontab again!",ProgramName);
                        log_err(error);
                        if(!load_rec()) {
                                ok = 0;
                                snprintf(error,MAX_LINE,"%s: load record from crontab fail!",ProgramName);
                                log_err(error);
                        }
                        modify_time = check_time;
                }

                if(ok) {
                        /* do the job */
                        do_job(running_time);
                } else
                        exit(1);
                /* sleep */
                running_time += SECONDS_PER_MINUTE;
                cron_sleep(running_time);
                close(markfd);
        }
}