How to get current locale of my environment?

From man 3 setlocale (New maxim: "When in doubt, read the entire manpage."):

If locale is "", each part of the locale that should be modified is set according to the environment variables.

So, we can read the environment variables by calling setlocale at the beginning of the program, as follows:

#include <iostream>
#include <locale.h>
using namespace std;

int main()
{
    setlocale(LC_ALL, "");
    cout << "LC_ALL: " << setlocale(LC_ALL, NULL) << endl;
    cout << "LC_CTYPE: " << setlocale(LC_CTYPE, NULL) << endl;
    return 0;
}

My system does not support the zh_CN locale, as the following output reveals:

$ ./a.out 
LC_ALL: en_US.utf8
LC_CTYPE: en_US.utf8
$ export LANG=zh_CN.UTF-8
$ ./a.out 
LC_ALL: C
LC_CTYPE: C

Windows: I have no idea about Windows locales. I suggest starting with an MSDN search, and then opening a separate Stack Overflow question if you still have questions.

Just figured out how to get locale by C++, simply use an empty string "" to construct std::locale, which does the same thing as setlocale(LC_ALL, "").

locale l("");
cout<<"Locale by C++: "<<l.name()<<endl;

This link described differences in details between C locale and C++ locale.