//en.cppreference.com/w/c/string/wide/wmemmove.html
#include <locale.h>
#include <stdio.h>
#include <wchar.h>
int main(void)
{
setlocale(LC_ALL, "en_US.utf8");
wchar_t str[] = L"αβγδεζηθικλμνξοπρστυφχψω";
printf("%ls\n", str);
wmemmove(str + 4, str + 3, 3); // copy from [δεζ] to [εζη]
printf("%ls\n", str);
}