Printing UTF-8 strings with printf – wide vs. multibyte string literals

printf("ο Δικαιοπολις εν αγρω εστιν\n");

prints the string literal (const char*, special characters are represented as multibyte characters). Although you might see the correct output, there are other problems you might be dealing with while working with non-ASCII characters like these. For example:

char str[] = "αγρω";
printf("%d %d\n", sizeof(str), strlen(str));

outputs 9 8, since each of these special characters is represented by 2 chars.

While using the L prefix you have the literal consisting of wide characters (const wchar_t*) and %ls format specifier causes these wide characters to be converted to multibyte characters (UTF-8). Note that in this case, locale should be set appropriately otherwise this conversion might lead to the output being invalid:

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

int main(void)
{
    setlocale(LC_ALL, "");
    printf("%ls", L"ο Δικαιοπολις εν αγρω εστιν");
    return 0;
}

but while some things might get more complicated when working with wide characters, other things might get much simpler and more straightforward. For example:

wchar_t str[] = L"αγρω";
printf("%d %d", sizeof(str) / sizeof(wchar_t), wcslen(str));

will output 5 4 as one would naturally expect.

Once you decide to work with wide strings, wprintf can be used to print wide characters directly. It’s also worth to note here that in case of Windows console, the translation mode of the stdout should be explicitly set to one of the Unicode modes by calling _setmode:

#include <stdio.h>
#include <wchar.h>

#include <io.h>
#include <fcntl.h>
#ifndef _O_U16TEXT
  #define _O_U16TEXT 0x20000
#endif

int main()
{
    _setmode(_fileno(stdout), _O_U16TEXT);
    wprintf(L"%s\n", L"ο Δικαιοπολις εν αγρω εστιν");
    return 0;
}