changing size of array - c

Question

I have the following code:
typedef struct my_data {
char* name;
}my_data;
my_data data[]={
{ .name = "Peter" },
{ .name = "James" },
{ .name = "John" },
{ .name = "Mike" }
};
void loaddata()
{
FILE * in;
if((in = fopen("data.txt","rt")) != NULL) {
memset(data, 0, sizeof(data));
int i = 0;
while(!feof(in))
{
fscanf(in,"%s", &data[i].name);
i++;
};
fclose(in);
}
}
to read contents and process them I use this:
for (i=0; i<sizeof(data)/sizeof(data[0]); i++)
but if the number of lines in file is less than the number of defined array I get a lot of empty records so I modified it into:
for (i=0; (i<sizeof(data)/sizeof(data[0])) && strlen(data[i].name)>0; i++)
which is working fine but I'm sure I will get errors if the number of lines in file will be larger than the defined array size.
Any idea how to make this code safe? To change array dynamically?
EDIT:
this way is working with size 300
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
typedef struct my_data {
char name[100];
}my_data;
struct my_data data[300];
my_data data_arr[]={
{ .name = "Peter" },
{ .name = "James" },
{ .name = "John" },
{ .name = "Mike" }
};
void process_data()
{
char name[100];
int i;
for (i=0; (i<sizeof(data)/sizeof(data[0])) && strlen(data[i].name)>0; i++) {
sprintf(name, "%s", data[i].name);
printf("%s\n", name);
}
}
void load_data()
{
int i = 0;
FILE * in;
if((in = fopen("data.txt","rt")) != NULL) {
while(!feof(in))
{
fscanf(in,"%s", &data[i].name);
i++;
};
fclose(in);
}
else
{
for (i=0; (i<sizeof(data_arr)/sizeof(data_arr[0])) && strlen(data_arr[i].name)>0; i++) {
sprintf(data[i].name, "%s", data_arr[i].name);
}
}
return;
}
int main()
{
load_data();
process_data();
return 0;
}

Answer 1

Arrays do not grow dynamically in C. So you have a few approaches:
get a pointer to a block of memory (using malloc) and use realloc whenever you need more space for an array - and index into your pointer
create a linked list using malloc for every new item you want to add to your list
Don't forget when using malloc to call free on every single block that you called malloc for.