每日一c--文件重定向-pdup = dup2(pf_1, pf_2);/

#include "../apue.h"// > 重定向int main(int argc, char **argv){int pf_1, pf_2, pdup;//以整形来定义文件指针  int pf;//文件指针char buf[20];//字符数组int n;//整形变量if(argc != 3)//参数若果不是三个{printf("%s <file name>\n", argv[0]);return -1;}//close(0);//./exe file.txt tmp.txtpf_1 = open(argv[1], O_RDWR);//pf_1指向第一个文件   读写的方式打开  argv[1]文件if(pf == -1)//没成功的打开文件{perror("open");return -1;}//read(0, buf, sizeof(buf));pf_2 = open(argv[2], O_RDWR);//以读写方式打开文件argv【2】返回值是文件描述符if(pf == -1){perror("open");return -1;}pdup = dup2(pf_1, pf_2);//将2的指针指向1   实现了指针的重定向read(pdup, buf, sizeof(buf));printf("buf=%s pf_1=%d pf_2=%d pdup=%d\n", buf, pf_1,pf_2,pdup);close(pf_1);close(pf_2);//1#if 0close(1);pf = open(argv[1], O_RDWR);if(pf == -1){perror("open");return -1;}//write(pf, "hello world\n", 20);write(1,"hello world\n", 20);write(2,"open err", 20);n = read(0, buf, sizeof(buf));buf[n]='\0';write(1, buf, n);close(pf);#endif}