Sorry for creating this topic, but I've searched the whole Google for this solution, but I didn't found it.
In Windows, my app works fine with those <windows.h> and the Sleep (with upper S), then I went to Linux and started to re-learn C++ into it.
Installed Codeblocks normally, I can compile other programs normally, but when I use the sleep function, the system waits the whole sleep before printing the countdown correctly (as in Windows).
I think isn't a Codeblocks problem, it's probably an mistake commited by me.
The code:
#include <iostream>
#include <unistd.h>
using namespace std;
int main ()
{
    string login;
    string pass;
    int n=3;
    cout << "Login: ";
    cin >> login;
    cout << "Password: ";
    cin >> pass;
    cout << "Checking password...\n";
    cout << "Authenticating in ";
    while (n>0) {
          cout << n << " ";
        sleep(3);
        --n;
              }
    cout << "\n";
    if (login=="dezt" && pass=="test")
        cout << "System Authenticated.\n";
    else
        cout << "Access denied.\n";
    return 0;
}
I've tried a bunch of variations to make the countdown works properly, but the program waits 3 seconds, then print all at once the 3 2 1 and boom, without the fashion 3 (wait) 2 (wait) 1 (wait) ok.
OBS again: In Windows, it worked correctly (with changes in headers).
If this topic is inappropriate, please delete it.