Random array with many numbers getting error

I have a homework to do: I need to measure the time for the bubblesort in a random array with 100000 numbers. I get an error when I try to randomly generate number.Also if I DON'T randomly generate numbers I get 0 everytime. I done this so far:

main.c 

int main()
{
    int *a,n = 0;
    srand(time(0));
    beolvas(&a,&n,"be.txt");
    clock_t start,stop;
    start = clock();
    bubblesort(a,n);
    stop = clock();
    float timespent = (stop - start)/CLOCKS_PER_SEC;
    printf("%f\n",timespent);

    kiir(a,n);
    free(a);
    return 0;
}

kibe.h

void beolvas(int **a,int *n,const char * file)
{
    int i;
    FILE * fin;
    fin = fopen("be.txt", "rt");
    *a = (int*)malloc(*n*sizeof(int));
    if(a == 0){printf("Error");return 0;}
    for(i = 0; i < 100000; ++i){
        *a = rand() % 100;
    }
    fclose(fin);
}
void bubblesort(int *a, int n)
{
    int i,j,csere;

    for(i = 0; i < n-1; ++i){
        for(j = 0; j < n - i -1; ++j){
            if (a[j] > a[j + 1]){
                csere = a[j];
                a[j] = a[j + 1];
                a[j + 1] = csere;
            }
        }
    }
}

void kiir(int *a,int n)
{
    int i;
    for(i = 0; i < n; ++i){
        printf("%i ",a[i]);
    }
}

As you see I need to use headers...It is really boring...