Thread: Read file of ints, sort it and write to another file

I'am having some problems with files. I try to write the sorted array to the file but it just fills it with trash.
My understanding is that i open a new file called Inteiros2.txt and it fwriting writes the numbers. But that's clearly not the case, what's rong?

Code:

#include <stdio.h>

void SelectionSort(int v[], int n)
{
    for(int i=0;i<n-1;i++)
    {
        int iMin=i;
        for(int j=i+1;j<n;j++)
        {
            if(v[j]<v[iMin])
                iMin=j;
        }
        int aux=v[i];
        v[i]=v[iMin];
        v[iMin]=aux;
        
    }
}
int main()
{
    FILE *f;
    f=fopen("C:\\Users\\PC\\Documents\\Inteiros.txt", "r");
    if(f==NULL)
    {
        printf("Erro\n");
        return 0;
    }    
    int numbers[100], num, i=0;
    while(fscanf(f, "%d", &num)>0)
    {
        numbers[i]=num;
        i++;    
    }
    fclose(f);
    printf("%d numbers were read\n", i);
    SelectionSort(numbers, 61);
    for(int i=0;i<61;i++)
    {
        printf("%d --> %d\n", i, numbers[i]);
    }
    FILE *f2=fopen("C:\\Users\\PC\\Documents\\Inteiros2.txt", "w");
    if(f==NULL)
    {
        printf("Erro\n");
        return 0;
    }
    fwrite(numbers, sizeof(int), 61,f2);
    fclose(f2);
}

I thought i was doing that with the 61 parameter in the fwrite function.
I changed the array to numbers[61] but Inteiros2.txt is still with trash. See there how it looks:

That worked as if by magic... Thanks guys!

Code:

#include <stdio.h>
#define NUM_NUMBERS 61


void SelectionSort(int v[], int n)
{
    int iMin;
    for(int i=0;i<n-1;i++)
    {
        iMin=i;
        for(int j=i+1;j<n;j++)
        {
            if(v[j]<v[iMin])
            {
                iMin=j;
            }
        }
        int aux=v[i];
        v[i]=v[iMin];
        v[iMin]=aux;    
    }
}




int main()
{
    FILE *f, *f2;
    int inteiros[NUM_NUMBERS], number, i=0;
    f=fopen("C:\\Users\\PC\\Documents\\Inteiros.txt", "r");
    if(f==NULL)
        printf("Erro\n");
        
    while(i <NUM_NUMBERS && fscanf(f, "%d",&number)==1)
    {
        inteiros[i]=number;
        i++;
    }
    printf("Foram lidos %d numeros\n", i);
    fclose(f);
    SelectionSort(inteiros, NUM_NUMBERS);
    f2=fopen("C:\\Users\\PC\\Documents\\Inteiros2.txt", "w");
    for(int i=0;i<NUM_NUMBERS;i++)
    {
        fprintf(f2, "%d\n", inteiros[i]);
        
    }
    fclose(f2);


    return 0;
    
}

When you open your file for reading, you check if it opened successfully ... but then still try to access it either way. If the file failed to open, you should take appropriate action. In your case, since the entire program depends on that file, you should exit the program if it failed to open properly.

When you open your file for writing, you don't even check if it opened successfully.

[edit] I see these checks in the original version of the program ... where'd they go?