char buf[INT_BUFSIZE_BOUND (uintmax_t)]; printf (_("The file is %s octets long.\n"), umaxtostr (size, buf));
where umaxtostr() has the following prototype:
char *umaxtostr (uintmax_t, char *);
and it returns its second argument (the address of the buffer provided by the caller) so it can be used easily as an argument in printf calls.