守护进程 得不到想要的结果

[henu_fyh]

题目很简单 就是让搞一个守护进程出来 然后每隔3S中在文件中写入一段话 下边代码 编译通过 但是无法实现题目要求

/* ************************************************************************
 *       Filename:  t.c
 *    Description:
 *        Version:  1.0
 *        Created:  2017年07月29日 12时28分27秒
 *       Revision:  none
 *       Compiler:  gcc
 *         Author:  fyh
 *        Company:  henu
 * ************************************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <fcntl.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <sys/stat.h>

//我想在守护进程的主程序中在文件中每隔3S中写入一段字符


void catch(int signo)
{
	int fd = open("1", O_RDWR|O_CREAT, 0644);

	write(fd, "---\n", 4);
}

void my()       //定义守护进程
{
	pid_t pid, sid;

	pid = fork();

	if (pid > 0)
		return ;
		
	sid = setsid();

	int ret = chdir("/home");

	umask(0002);

	close(0);

	int fd = open("/dev/null", O_RDWR);

	dup2(0, 1);
	dup2(0, 2);

	sigset_t set;
	sigemptyset(&set);
	sigaddset(&set, SIGALRM);

	struct sigaction temp1, temp2;
	temp1.sa_handler = catch;
	temp1.sa_flags = 0;
	temp1.sa_mask = set;

	sigaction(SIGALRM, &temp1, NULL);       //注册

	while (1)
	{
		alarm(3);       //每个3S发送一个信号
		//sleep(3);
	}

}

int main(int argc, char argv[])
{
	my();
    while (1);

    return 0;
}

[henu_fyh]

本人小白 刚学Linux系统编程

[LubinLew]

仅供参考 编译 gcc xx.c -lrt 运行 ./a.out 查看运行结果 tail -f /tmp/1

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <fcntl.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <time.h>
#include <pthread.h>


//real jobs
void timer_notify_cb(union sigval val)
{
	int fd = open("1", O_RDWR|O_CREAT|O_APPEND, 0644);
	write(fd, "---\n", 4);
	close(fd);
}

void cycling_job_timer(int period)
{
	/* Variable Definition */
	timer_t id;
	struct timespec spec;
	struct sigevent ent;
	struct itimerspec value;
	struct itimerspec get_val;
	
	/* Init */
	memset(&ent, 0x00, sizeof(struct sigevent));
	memset(&get_val, 0x00, sizeof(struct itimerspec));
	  
	/* create a timer */
	ent.sigev_notify = SIGEV_THREAD;
	ent.sigev_notify_function = timer_notify_cb;
	timer_create(CLOCK_MONOTONIC, &ent, &id);
	
	/* start a timer */
	value.it_value.tv_sec = period;
	value.it_value.tv_nsec = 0;
	value.it_interval.tv_sec = period;
	value.it_interval.tv_nsec = 0;
	timer_settime(id, 0, &value, NULL);
}

void daemonize(void)
{
	pid_t pid;
	int nullfd;

	/* step1 : clear file creation mask */
	umask(0);

	/* step2 : fork */
	pid = fork();
	if (pid < 0) {
		perror("fork failed");
		exit(EXIT_FAILURE);
	}
	else if (pid != 0) { // parent process exit
		printf("== the deamon pid is %u\n", pid);
		exit(EXIT_SUCCESS);
	}

	/* step3 : setsid */
	setsid();

	/* setp4 : chdir */
	chdir("/tmp/");

	/* step5 : close all open file descriptions */

	/* step6 : redirect standard IO/error */
	nullfd = open("/dev/null", O_RDWR);
	dup2(nullfd, STDIN_FILENO);
	dup2(nullfd, STDOUT_FILENO);
	dup2(nullfd, STDERR_FILENO);

	/* regeister timer */
	cycling_job_timer(3);
}

int main(int argc, char argv[])
{
	daemonize();

	while (1) {
		sleep(1);
	}

    return 0;
}