char * getline(FILE * fi,size_t line_length,size_t line_number)
{

size_t i;
char * aux_string;
char * p;
if (fi==NULL)
    return NULL;

if ((aux_string = malloc(line_length*sizeof(char)))==NULL)
    return NULL;

i=0;
while(fgets(aux_string,line_length,fi)!=NULL||feof(fi)!=0)
 {

    if (i==line_number)
    {

        if ((p=strchr(aux_string,'n'))!=NULL)
        {
            *p='';
        }

        return aux_string;
    }
    i++;

 }
return NULL;
}

puts(getline(file_a,MAX_LENGTH,0));
puts(getline(file_a,MAX_LENGTH,0));