How to format a number from 1123456789 to 1,123,456,789 in C?

Question

How can I in C language format a number from 1123456789 to 1,123,456,789? I tried using printf("%'10d\n", 1123456789); but that doesn't work.

Could you advise anything? The simpler the solution the better.

Answer 1

If your printf supports the ' flag (as required by POSIX 2008 printf()), you can probably do it just by setting your locale appropriately. Example:

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

int main(void)
{
    setlocale(LC_NUMERIC, "");
    printf("%'d\n", 1123456789);
    return 0;
}

And build & run:

$ ./example 
1,123,456,789

Tested on Mac OS X & Linux (Ubuntu 10.10).