First use of headers in c and really not understanding it well - c

Question

I using first time the HEADERS in c so I'm not understanding it well.
main.c
#include <stdio.h>
#include <stdlib.h>
#include "kibe.h"
int main()
{
int a[5],n,i;
beolvas(a,n,"be.txt");
kiir(a,n);
return 0;
}
kibe.h
#ifndef KIBE_H_INCLUDED
#define KIBE_H_INCLUDED
void beolvas(int*, int, const char *);
void kiir(int*, int);
#endif // KIBE_H_INCLUDED
kibe.c
#include <stdio.h>
#include <stdlib.h>
void beolvas(int *a,int n,const char * file)
{
int i;
FILE * fin;
fin = fopen("be.txt", "rt");
fscanf(fin,"%i",&n);
a = (int*)malloc(n*sizeof(int));
for(i = 0; i < n; ++i){
fscanf(fin,"%i",&a[i]);
}
free(a);
}
void kiir(int *a,int n)
{
int i;
for(i = 0; i < n; ++i){
printf("%i ",a[i]);
}
}
The problem is that I get memory garbage every time and the file contains five numbers which must be read and written to monitor. If I write the void kiir is code to void beolvas function it works well.

Answer 1

You allocate dynamic memory in your function beolvas but you never pass it out of the function. Your parameters a and n have to be output parameters, so you have to change your function signature. Apart form this use fclos to close the file. Adapt your code like this:
kibe.c
void beolvas( int **a, int *n, const char * file )
// ^^ ^ output paramters a and n
{
FILE * fin;
fin = fopen("be.txt", "rt");
fscanf( fin, "%i", n ); // read number of elements
// ( n is a pointer to an int )
*a = malloc( *n * sizeof(int) ); // allocate memors
for ( int i = 0; i < n; ++i)
{
fscanf(fin,"%i",(*a)+i); // read one element
// ( *a is the pointer to the dynamic memory,
// so (*a)+i is a pointer to (*a)[i] )
}
fclose(fin);
}
kibe.h
void beolvas( int**, int* , const char *);
main.c
int main()
{
int a* = NULL;
int n = 0;
beolvas( &a, &n,"be.txt");
// ^ ^
kiir( a, n );
free(a); // free the memory which was allocated inside function beolvas
return 0;
}