How to Print Box Characters in C (Windows)

Question

How might one go about printing an em dash in C?

One of these: —

Whenever I do: printf("—") I just get a ù in the terminal.

Thank you.

EDIT: The following code is supposed to print out an Xs an Os looking grid with em dashes for the horizontal lines.

int main ()
{
    char grid[3][3] = {{'a', 'a', 'a'}, {'a', 'a', 'a'}, {'a', 'a', 'a'}};

    int i, j;

    for (i = 0; i < 3; i++) {
        for (j = 0; j < 3; j++) {
            if (j != 0)
            {
                printf("|");
            }
            printf("  %c  ", grid[i][j]);
        }
        if (i != 2)
        {
            printf("\n——————————————\n");
        }
    }

    return 0;
}

Output: (The "ù"s should be "—"s)

  a  |  a  |  a
ùùùùùùùùùùùù
  a  |  a  |  a
ùùùùùùùùùùùù
  a  |  a  |  a

EDIT: I'm on Windows 10 x64 using Codeblocks 16.01 with C11.

EDIT: I was informed of box characters and the question has morphed into how to print those, hence the title and tag change.

Answer 1

In standard C, you use wide characters and wide strings:

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

int main(void)
{
    setlocale(LC_ALL, "");
    fwide(stdout, 1);

    wprintf(L" \n");

    wprintf(L"   │   │   \n");
    wprintf(L"───┼───┼───\n");
    wprintf(L"   │   │   \n");
    wprintf(L"───┼───┼───\n");
    wprintf(L"   │   │   \n");

    return EXIT_SUCCESS;
}

You can use wide character constants like L'┼'; their conversion specifier for printf() and wprintf() functions is %lc. Similarly, a wide string constant has an L prefix, and its conversion specifier is %ls.

Unfortunately, you are limited to the mangled version of C Microsoft provides, so it may or may not work for you.

---

The above code does not work in Windows, because Microsoft does not want it to. See Microsoft documentation on setlocale() for details:

The set of available locale names, languages, country/region codes, and code pages includes all those supported by the Windows NLS API except code pages that require more than two bytes per character, such as UTF-7 and UTF-8.

In other words, Microsoft's C localization is limited to one-byte code pages, and specifically excludes any Unicode locales. This is, however, purely part of Microsoft's EEE strategy to bind you, a budding developer, to Microsoft's own walled garden, so that you will not write actual portable C code (or, horror of horrors, avail yourself to POSIX C), but are mentally locked to the Microsoft model. You see, you can use _setmode() to enable Unicode output.

As I do not use Windows at all myself, I cannot verify whether the following Windows-specific workarounds actually work or not, but it is worth trying. (Do report your findings in a comment, Windows users, please, so I can fix/include this part of this answer.)

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

#ifdef _WIN32
#include <io.h>
#include <fcntl.h>

static int set_wide_stream(FILE *stream)
{
    return _setmode(_fileno(stream), _O_U16TEXT);
}

#else

static int set_wide_stream(FILE *stream)
{
    return fwide(stream, 1);
}

#endif

int main(void)
{
    setlocale(LC_ALL, "");

    /* After this call, you must use wprintf(),
       fwprintf(), fputws(), putwc(), fputwc()
       -- i.e. only wide print/scan functions
       with this stream.
       You can print a narrow string using e.g.
       wprintf(L"%s\n", "Hello, world!");
    */
    set_wide_stream(stdout, 1);

    /* These may not work in Windows, because
       the code points are 0x1F785 .. 0x1F7AE
       and Windows is probably limited to
       Unicode 0x0000 .. 0xFFFF */
    wprintf(L" \n");

    /* These are from the Box Drawing Unicode block,
       U+2500 ─, U+2502 │, and U+253C ┼,
       and should work everywhere. */
    wprintf(L"   │   │   \n");
    wprintf(L"───┼───┼───\n");
    wprintf(L"   │   │   \n");
    wprintf(L"───┼───┼───\n");
    wprintf(L"   │   │   \n");

    return EXIT_SUCCESS;
}