dup 复制文件描述符

#include<stdio.h>#include<unistd.h>//#include<sys/stat.h>//#include<fcntl.h>//#include<stdlib.h>//dup 复制文件描述符int main(int argc,char *argv[]){    int fd;    char buf[10];    if(argc != 2)    {        printf("usage %s <filename>\n",argv[0]);        exit(1);    }    fd = open(argv[1],O_RDWR | O_CREAT,0664);    if(fd < 0)    {        perror("fail to open");        exit(1);    }//从标准文件读取,复制文件描述符           fgets(buf,10,stdin);    dup(STDIN_FILENO);    write(fd,buf,10);    return 0;}