Linux_C dup()

/*
 * stdinredir2.c
 * shows two more methods for redirecting standard input
 * use #define to set one or the other
 */
#include <stdio.h>
#include <fcntl.h>
/*#define CLOSE_DUP  /*open, close, dup, close */
/*#define USE_DUP2   /*opne, dup2, close */
int main(void) {
  int fd, newfd;
  char line[100];
  //read and print lines
  fgets(line, 100, stdin);
  printf("line: %s", line);
  
  fd=open("/home/wiz/wizcode/psh1.c", O_RDONLY);  /* open the disk file */

  #ifdef CLOSE_DUP
     close(0);
     newfd=dup(fd);              /*copy open fd to 0*/
  #else
     newfd=dup2(fd,0);           /*close 0, dup fd to 0*/
  #endif
  if(newfd!=0){
    fprintf(stderr, "Could not duplicate fd to 0
");
    exit(1);
  }
  close(fd);
  fgets(line, 100, stdin); printf("%s", line);
  fgets(line, 100, stdin); printf("%s", line);
  fgets(line, 100, stdin); printf("%s", line);
  return 0;
}