//This program shows you how input redirection works.
#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <sys/types.h>

int main()
{
  int fd = -1;
  char sm[512];
  
  printf("What's the message? ");
  scanf("%s", sm);
  printf("The message was: %s\n", sm);
  
  printf("Redirecting\n");
  //opening a file
  fd = open("input_file.txt", O_RDONLY);
  //closing stdin
  close(0);
  //Duping the file descriptor for the file. Since we just closed stdin, the duped file descriptor is going to 
 //be 0.
  dup(fd);
  close(fd);

  printf("What's the message? ");
  scanf("%s", sm);
  printf("The message was: %s\n", &sm);
  
  
  return 0;
  
}