守护进程实例

/*                                                                                                                                                                               
**守护进程实例,每隔5s向/tmp/daemon.log中写入当前系统时
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <time.h>
#include <string.h>
#define MAX_SIZE 65535

int main(int argc,char *argv[]){
        
    pid_t pc; 
    int i,fd;
    time_t timep;
    struct tm *timenow;
    char buff[128];

    //1.创建子进程，主进程退出
    pc = fork();
    if(pc == -1){
        perror("Create child process error");
        exit(1);
    }else if(pc > 0){ 
        exit(0);
    }   
    //2.在子进程中创建新会话
    setsid();
    //3.改变当前目录为根目录
    chdir("/");
    //4.重设文件权限掩码
    umask(0);
    //5.关闭文件描述符
    for(i=0;i<MAX_SIZE;i++){
        close(i);
    }   
    //守护进程创建完毕，编写守护进程的工作
    while(1){
        if((fd = open("/tmp/daemon.log",O_CREAT|O_WRONLY|O_APPEND,0600)) == -1){
            perror("Open error");
            exit(1);
        }
        //获取当前日期
        time(&timep);
        timenow = localtime(&timep);
        sprintf(buff,"%s",asctime(timenow));
        write(fd,buff,strlen(buff));
        close(fd);
        sleep(5);
    }

}