linux后台服务编程简单样例

样例代码如下：

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


void get_format_time(char *str)
{
	
	time_t now;
	struct tm *timenow;
	time(&now);
	timenow = localtime(&now);
	sprintf(str,"%d-%02d-%02d %02d:%02d:%02d",1900+timenow->tm_year,1+timenow->tm_mon,timenow->tm_mday,timenow->tm_hour,timenow->tm_min,timenow->tm_sec);
}


int main()
{

	pid_t pid;
	int i,fd;
	char *buf = "This is a daemon program.\n";
	char time_str[50],content[100];

	if((pid = fork())<0)
	{
		printf("fork error\n");
		exit(1);
	}
	else if(pid > 0)
	{
		exit(0);
	}
	
	setsid();//create new session in son process.
	chdir("/");//change work directory to root.
	umask(0);//reset mask
	//close file descriptor extend from parent process.
	int fd_size = getdtablesize();
	for(i=0;i<fd_size;i++)
	{
		close(i);
	}
	while(1)
	{
		fd = open("/tmp/daemon.log",O_CREAT|O_WRONLY|O_APPEND,0600);
		if(fd<0)
		{
			exit(1);
		}
		get_format_time(time_str);
		sprintf(content,"%s | %s",time_str,buf);
		write(fd,content,strlen(content)+1);
		close(fd);
		sleep(10);
	}
	return 0;
}

更多信息可参考：http://blog.chinaunix.net/uid-27004869-id-4038979.html