c lang text file input sum of digits in rows

Question

//ok, thanks for help. i edited the code, passed a pointer and now the it prints the number from particular row, prints the number of that row, and prints the sum off all consiquent numbers. Good so far, but... What i want do do next, is to assign each of the sums to an array, so i can use for loop to check whether the resulting sum equals to any previous resulting sums. i use tab[n]==result; unfortunatelly after the while loop is done, all the array elements are empty...thanks//

include

include

int main()
{
    int result =0;

    read_ints("numbers.txt", &result);


}



void read_ints (const char* file_name, int *result)
{

  FILE* file = fopen ("numbers.txt", "r");
  int i = 0;
  int n=1; //row number//
  int tab[n]; //array

  if (file == NULL)
  {
   printf("unable to open file %s", file_name);

  }
  fscanf (file, "%d", &i);
  while (!feof (file))
    {
      printf ("%d ", i);
      *result += i;
      tab[n]==result;
      printf("row number: %d \n", n);
      n++;

      printf("\n sum of this number and all numbers before is: %d\n", *result);

      fscanf (file, "%d", &i);

    }
          printf("\nnumber from row number one is ... : %d\n", tab[1]);
  fclose (file);



}

Answer 1

Your code is mostly right. You're just calling read_ints incorrectly. You should pass in a pointer to result if you want a value returned.

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

void read_ints (const char* file_name, int *result) {
    FILE* file = fopen (file_name, "r");
    int i = 0;

    if (file == NULL) {
        printf("unable to open file %s\n", file_name);
        return;
    }

    fscanf (file, "%d", &i);
    while (!feof (file))
    {
        printf ("%d ", i);
        *result += i;
        printf("\n suma tej liczby ze wszystkimi poprzednimi wynosi: %d\n", *result);
        fscanf (file, "%d", &i);

    }
    fclose (file);
}

int main() {
    int result =0;

    read_ints("liczby.txt", &result);

}

Answer 2

the following proposed code:

1. properly checks for errors
2. properly passes the error text to stderr, including the text reason the system thinks the error occurred.
3. uses the returned value from fscanf() to control the loop
4. properly contains a 'prototype' for the sub function
5. properly uses void inside the parens of main() and the prototype of the sub function that receives no parameters.
6. consistently indents the code, for readability
7. cleanly compiles
8. documents why each header file is included

And now, the proposed code:

#include <stdio.h>   // FILE, perror(), fopen(), printf(), fclose()
#include <stdlib.h>  // exit(), EXIT_FAILURE



void read_ints ( void );


int main( void )
{
    read_ints();
}



void read_ints ()
{
    FILE* file = fopen ("liczby.txt", "r");
    if( !file )
    {
      perror( "fopen to read liczby.txt failed" );
      exit( EXIT_FAILURE );
    }


    int i = 0;
    int result = 0;
    while ( fscanf ( file, "%d", &i) == 1 )
    {
      printf ("%d ", i);
      result=result+i;
      printf("\n suma tej liczby ze wszystkimi poprzednimi wynosi: %d\n", result);
    }
    fclose (file);
}

Answer 3

//ok, the code looks better now, but still, the result values doesnt seem to store in the tab[] array. this is due to lack of a pointer or bad declaration of the array(?).
i intented it to be a dynamic array, so that i dont need to declare the specific size of the array.//

#include <stdio.h>
#include <stdlib.h>
void read_ints(const char* file_name, int *result);

int main()
{
    int result =0;
    read_ints("numbers.txt", &result);
}
void read_ints (const char* file_name, int *result)
{
  FILE* file = fopen ("numbers.txt", "r");
  int i = 0;
  int n=0; //row number//
  int m;
  int tab[m]; //array//
  if (file == NULL)
  {
   printf("unable to open file %s", file_name);
  }
  while ( fscanf (file, "%d", &i) ==1)
    {
       n++;
      printf ("%d\n ", i);
      *result += i;
      printf("\n we are at row nr. %d sum of this number and all numbers before is: %d\n", n, *result);
       tab[n]==*result;
    }
          printf("\nnumber from row number one is ... : %d\n", tab[1]); //this does not work properly //
  fclose (file);
}