#include <iostream>
#include <string.h>
#include <stdio.h>

using namespace std;

int main()
{
  setlocale(LC_ALL, "ru_RU.UTF-8");
  int i = 0;
  wchar_t widets[] = L"АБВГДЕЁЖЗИЙКЛМНОПРСТУФХЦЧШЩЪЬЭЮЯ!";

  while(widets[i]){
    if((wchar_t)widets[i] >= 1040 && (wchar_t)widets[i] <= 1071 ) widets[i] = (wchar_t)widets[i] + 32;
    i++;
  }

  for(i=0;i<33;i++)
    printf("%lc\n",widets[i]);
}

std::wstring ws(L"some Русский тексн");
std::transform(ws.begin(), ws.end(), ws.begin(), std::bind2nd(std::ptr_fun(&std::tolower<wchar_t>), std::locale("ru_RU.UTF-8")));
std::wcout << ws;

#include <stdlib.h>
#include <stdio.h>
#include <wchar.h>
#include <wctype.h>
#include <locale.h>

int main(void)
    {
    char *utf_str = "ТАКОЙ вот текст", *u;
    wchar_t *w_str, *w;
    size_t len;

    setlocale(LC_ALL, "ru_RU.UTF8");

    /* To wide string */
    len = mbstowcs(NULL, utf_str, 0);
    w_str = malloc((len + 1) * sizeof(*w_str));
    mbstowcs(w_str, utf_str, len + 1);

    /* To upper */
    for(w = w_str; *w != 0; ++w)
        *w = towupper(*w);

    /* To multibyte string */
    len = wcstombs(NULL, w_str, 0);
    u = malloc((len + 1) * sizeof(*u));
    wcstombs(u, w_str, len + 1);
    
    printf("UPPER: %s\n", u);
    
    /* To lower */
    for(w = w_str; *w != 0; ++w)
        *w = towlower(*w);
    
    /* To multibyte string */
    len = wcstombs(NULL, w_str, 0);
    u = realloc(u, (len + 1) * sizeof(*u));
    wcstombs(u, w_str, len + 1);
    
    printf("lower: %s\n", u);
    
    free(u);
    free(w_str);

    return 0;
    }

string utf_str = "ТАКОЙ вот текст";
wstring w_str = utf_str;
//for (wstring::iterator w_it = w_str.begin(); it != w_str.end(); it++)
//   cout << *w_it << " ";
transform(w_str.begin(), w_str.end(), w_str.begin(), ::tolower);
string u = w_str;
cout << u << endl;

#include <boost/algorithm/string/replace.hpp>
using namespace std;

string string_to_lower (string source) {
boost::replace_all(source, "А", "а");
boost::replace_all(source, "Б", "б");
boost::replace_all(source, "В", "в");
boost::replace_all(source, "Г", "г");
boost::replace_all(source, "Д", "д");
boost::replace_all(source, "Е", "е");
boost::replace_all(source, "Ё", "ё");
boost::replace_all(source, "Ж", "ж");
boost::replace_all(source, "З", "з");
boost::replace_all(source, "И", "и");
boost::replace_all(source, "Й", "й");
boost::replace_all(source, "К", "к");
boost::replace_all(source, "Л", "л");
boost::replace_all(source, "М", "м");
boost::replace_all(source, "Н", "н");
boost::replace_all(source, "О", "о");
boost::replace_all(source, "П", "п");
boost::replace_all(source, "Р", "р");
boost::replace_all(source, "С", "с");
boost::replace_all(source, "Т", "т");
boost::replace_all(source, "У", "у");
boost::replace_all(source, "Ф", "ф");
boost::replace_all(source, "Х", "х");
boost::replace_all(source, "Ц", "ц");
boost::replace_all(source, "Ч", "ч");
boost::replace_all(source, "Ш", "ш");
boost::replace_all(source, "Щ", "щ");
boost::replace_all(source, "Ъ", "ъ");
boost::replace_all(source, "Ы", "ы");
boost::replace_all(source, "Ь", "ь");
boost::replace_all(source, "Э", "э");
boost::replace_all(source, "Ю", "ю");
boost::replace_all(source, "Я", "я");
return source;
}

#include <algorithm>
#include <fstream>
#include <iostream>
#include <locale>
using namespace std;

int main()
{
	setlocale(LC_ALL, "ru_RU.UTF-8");

	wifstream f( "data.txt" );
	f.imbue( locale( "ru_RU.UTF-8" ) );
	while( f.good() )
	{
		wstring s;
		f >> s;
		transform( s.begin(), s.end(), s.begin(), towlower );

		wcout << s << endl;
	}
}

wofstream of( "data2.txt" );
of.imbue( locale( "ru_RU.UTF-8" ) );
of << s << endl;

wstring s;
getline( f, s );

// $ ./test_boost.cpp <<< 'ТЕКСТ'
// текст

#include <iostream>
#include <locale>
#include <boost/locale.hpp>

int main() {
    boost::locale::generator gen;
    std::locale loc = gen("");
    std::string line;
    while (std::getline(std::cin, line))
        std::cout << boost::locale::to_lower(line, loc) << '\n';
}

#include <stdio.h>


void lover(char sh[255])
{
    
    int counter=0;
    
    while(sh[counter]!='\0')
    
    {  

        (sh[counter]==L'А') ? putchar(L'а'):
        (sh[counter]==L'Б') ? putchar(L'б'):
        (sh[counter]==L'В') ? putchar(L'в'):
        (sh[counter]==L'Г') ? putchar(L'г'):
        (sh[counter]==L'Д') ? putchar(L'д'):
        (sh[counter]==L'Е') ? putchar(L'е'):
        (sh[counter]==L'Ё') ? putchar(L'ё'):
        (sh[counter]==L'Ж') ? putchar(L'ж'):
        (sh[counter]==L'З') ? putchar(L'з'):
        (sh[counter]==L'И') ? putchar(L'и'):
        (sh[counter]==L'Й') ? putchar(L'й'):
        (sh[counter]==L'К') ? putchar(L'к'):
        (sh[counter]==L'Л') ? putchar(L'л'):
        (sh[counter]==L'М') ? putchar(L'м'):
        (sh[counter]==L'Н') ? putchar(L'н'):
        (sh[counter]==L'О') ? putchar(L'о'):
        (sh[counter]==L'П') ? putchar(L'п'):
        (sh[counter]==L'Р') ? putchar(L'р'):
        (sh[counter]==L'С') ? putchar(L'с'):
        (sh[counter]==L'Т') ? putchar(L'т'):
        (sh[counter]==L'У') ? putchar(L'у'):
        (sh[counter]==L'Ф') ? putchar(L'ф'):
        (sh[counter]==L'Х') ? putchar(L'х'):
        (sh[counter]==L'Ц') ? putchar(L'ц'):
        (sh[counter]==L'Ч') ? putchar(L'ч'):
        (sh[counter]==L'Ш') ? putchar(L'ш'):
        (sh[counter]==L'Щ') ? putchar(L'щ'):
        (sh[counter]==L'Ь') ? putchar(L'ь'):
        (sh[counter]==L'Ъ') ? putchar(L'ъ'):
        (sh[counter]==L'Э') ? putchar(L'э'):
        (sh[counter]==L'Ю') ? putchar(L'ю'):
        (sh[counter]==L'Я') ? putchar(L'я'):

        (sh[counter]=='A') ? putchar('a'):
        (sh[counter]=='B') ? putchar('b'):
        (sh[counter]=='C') ? putchar('c'):
        (sh[counter]=='D') ? putchar('d'):
        (sh[counter]=='E') ? putchar('e'):
        (sh[counter]=='F') ? putchar('f'):
        (sh[counter]=='G') ? putchar('g'):
        (sh[counter]=='H') ? putchar('h'):
        (sh[counter]=='I') ? putchar('i'):
        (sh[counter]=='J') ? putchar('j'):
        (sh[counter]=='K') ? putchar('k'):
        (sh[counter]=='L') ? putchar('l'):
        (sh[counter]=='M') ? putchar('m'):
        (sh[counter]=='N') ? putchar('n'):
        (sh[counter]=='O') ? putchar('o'):
        (sh[counter]=='P') ? putchar('p'):
        (sh[counter]=='Q') ? putchar('q'):
        (sh[counter]=='R') ? putchar('r'):
        (sh[counter]=='S') ? putchar('s'):
        (sh[counter]=='T') ? putchar('t'):
        (sh[counter]=='U') ? putchar('u'):
        (sh[counter]=='V') ? putchar('v'):
        (sh[counter]=='W') ? putchar('w'):
        (sh[counter]=='X') ? putchar('x'):
        (sh[counter]=='Y') ? putchar('y'):
        (sh[counter]=='Z') ? putchar('z'): putchar(sh[counter]);
        
        
        
         counter++;
        (sh[counter]=='\0') ? putchar('\n'): 0 ;
        };
    
    
    
    
    };
int main()

{

lover("АБВГДЕЁЖЗИЙКЛМНОПРСТУФХЦЧШЩЪЬЭЮЯ!");


};