shouhuled.c

守护进程

#include <stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<unistd.h>
#include <linux/fcntl.h>

#define LED_NUM         4
                                                                                
#define LED_OFF         0
#define LED_ON          1
#define LED_ON_ALL      0xF
#define LED_OFF_ALL     0x0



void init_daemon(void)
{
  int pid;
  int i;
  if(pid=fork())
    		exit(0);//父进程退出
  else if(pid< 0)
    		exit(1);
  setsid();
  chdir("");
  umask(0);
  if(pid=fork())
    	exit(0);
  else if(pid< 0)
   		 exit(1);
  for(i=0;i< 5;++i)
    		close(i);
 return;
}
int main(int argc, char ** argv)
{
	int i, j, wval, rval, fd;
	static char *driver = "/dev/led/0";
	init_daemon();
	fd = open(driver, O_RDWR);
  while(1)
  {
	sleep(5);
	for(i=0; i<6; i++)
	{
		if(i%2)
		{
			wval = LED_OFF_ALL;
			write(fd, &wval, 1);
			read(fd, &rval, 1);
			printf("Turn off all LEDs, readback val = 0x%02X\n", rval&0xF);
		}
		else
		{
			wval = LED_ON_ALL;
			write(fd, &wval, 1);
			read(fd, &rval, 1);
			printf("Turn on all LEDs, readback val = 0x%02X\n", rval&0xF);
		}			
		/* delay 1s */
		sleep(1);
	}
  }
  	close(fd);
	return 0;
}