Question

I wish to output large numbers with thousand-separators (commas or spaces) — basically the same as in How to display numeric in 3 digit grouping but using printf in C (GNU, 99).

If printf does not support digit grouping natively, how can I achieve this with something like printf("%s", group_digits(number))?

It must support negative integers and preferably floats, too.

Answer 1

If you can use POSIX printf, try

#include <locale.h>
setlocale(LC_ALL, ""); /* use user selected locale */
printf("%'d", 1000000);