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利用daemon()函数创建守护进程

1. 函数简介

#include <unistd.h>

int daemon(int nochdir, int noclose);

DESCRIPTION        The daemon() function is for programs wishing to detach themselves from        the controlling terminal and run in the background as system daemons.

       If nochdir is zero, daemon()  changes  the  process’s  current  working

       directory to the root directory ("/"); otherwise,

       If  noclose is zero, daemon() redirects standard input, standard output

       and standard error to /dev/null; otherwise,  no  changes  are  made  to        these file descriptors.

功能：创建一个守护进程

参数：

nochdir：=0将当前目录更改至“/”

noclose：=0将标准输入、标准输出、标准错误重定向至“/dev/null”

返回值：

成功：0

失败：-1

 

2. demo

#include 
   
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          #include 
          
           #define ERR_EXIT(m) \do \{\ perror(m);\ exit(EXIT_FAILURE);\}\while(0);int main(void){ time_t t; int fd; if(daemon(0, 1) < 0) { ERR_EXIT("daemon error"); } while(1) { fd = open("daemon.log", O_WRONLY|O_CREAT|O_APPEND, 0644); if(fd == -1) { ERR_EXIT("open error"); } t = time(0); char *buf = asctime(localtime(&t)); write(fd, buf, strlen(buf)); close(fd); sleep(60); } return 0;}
          
         
        
       
      
     
    
   

 

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