/* A variant of the program that does not work */

#include <stdio.h>
#include <stdlib.h>
#define MAX_STR_LEN 100

int main(void) {

  FILE *file_pointer;
  char str[MAX_STR_LEN], ch;
  int i = 0;

  file_pointer = fopen("first-file", "r+");

  if (file_pointer != NULL){
    while ((ch = fgetc(file_pointer)) != EOF){
      str[i] = ch;
      fputc('X', file_pointer);             /* Does not work ... */
      i++;
    }
    str[i] = '\0';

    printf("Read from file: %s\n", str);

    fclose(file_pointer);
  }
  else{
    printf("Could not open file. Bye.");
    exit(EXIT_FAILURE);
  }

  return 0;
}