A problem with "extern"

I have write a short program that use a static globle variabl .That
variable has been modefied in another file, but the result is not as
expect,nothing to output to show that variable has been modefied!
/////////////// "main.h" ///////////
#ifndef MAIN_H
#define MAIN_H

#include <vector>

static std::vector<int> data;

 void init();

#endif

//////////////// "main.c" ////////////////
#include "main.h"
#include <iostream>
#include <vector>

using namespace std;
extern std::vector<int> data;
int main()
{

    init();
    vector<int>::iterator it = data.begin ();
    while(it != data.end ())
   {
        cout << (*it) << endl;
        ++it;
   }
  return 0;
}

////////////////////// "init.cpp" ////
#include "main.h"
#include <vector>

extern std::vector<int> data;

void init()
{
    data.push_back (1);
    data.push_back (2);
    data.push_back (3);
}
////////////////////
why???

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