exec를 이용하여 백그라운드에서 명령어 수행(유닉스환경)

#include <stdio.h>  
#include <stdlib.h>  
#include <unistd.h>  
#include <sys/types.h>  
#include <sys/stat.h>  
#include <fcntl.h>  
 
#define EXIT_SUCCESS 0  
#define EXIT_FAILURE 1  
 
static void daemonize(void)  
{  
    pid_t pid, sid;  
    int fd;   
 
    /* already a daemon */  
    if ( getppid() == 1 ) return;  
 
    /* Fork off the parent process */  
    pid = fork();  
    if (pid < 0)    
    {     
        exit(EXIT_FAILURE);  
    }     
 
    if (pid > 0)    
    {     
        exit(EXIT_SUCCESS); /*Killing the Parent Process*/  
    }     
 
    /* At this point we are executing as the child process */  
 
    /* Create a new SID for the child process */  
    sid = setsid();  
    if (sid < 0)    
    {  
        exit(EXIT_FAILURE);  
    }  
 
    /* Change the current working directory. */  
    if ((chdir("/")) < 0)  
    {  
        exit(EXIT_FAILURE);  
    }  
 
 
    fd = open("/dev/null",O_RDWR, 0);  
 
    if (fd != -1)  
    {  
        dup2 (fd, STDIN_FILENO);  
        dup2 (fd, STDOUT_FILENO);  
        dup2 (fd, STDERR_FILENO);  
 
        if (fd > 2)  
        {  
            close (fd);  
        }  
    }  
 
    /*resettign File Creation Mask */  
    umask(027);  
}  
 
int main( int argc, char *argv[] )  
{  
    daemonize();  
 
    while(1)  
    {  
      /* Now we are a daemon -- do the work for which we were paid */  
 
      sleep(10);  
    }  
 
    return 0;  
}