How can I stream hexadecimal numbers with A-F (rather than a-f)?

Question

Is it possible to make ostream output hexadecimal numbers with characters A-F and not a-f?

int x = 0xABC;
std::cout << std::hex << x << std::endl;

This outputs abc whereas I would prefer to see ABC.

Could the downvoter of this question please be so kind as to explain to me what is so criminal about this question? As a matter of fact, I had opened MSDN for 'hex' in hopes to find the answer, but I didn't. So what's wrong with this question? — Armen Tsirunyan, Nov 07 '10 at 09:39
Don't know, but here's a upvote to counter it. I love doing that because it's fair (especially to those who have a genuine question - SO is meant to be for _all_ levels of developer, not just obnoxious know-it-alls like me) but mostly because it annoys the drive-by downvoters who can't even be bothered to leave a comment so that a question can be improved. Of course, they may well downvote my answer in retribution but it's not like I'm short of rep :-) — paxdiablo, Nov 07 '10 at 09:50
@paxdiablo: my feeling about retaliatory downvotes is that anyone likely to get involved in such nonsense has less than half my rep, so I'm going to win that one. Since I have less than half your rep, you can outlast twice as many... — Steve Jessop, Nov 07 '10 at 10:38

paxdiablo · Accepted Answer · 2017-06-21T02:12:14.197

12

Yes, you can use std::uppercase, which affects floating point and hexadecimal integer output:

std::cout << std::hex << std::uppercase << x << std::endl;

as in the following complete program:

#include <iostream>
#include <iomanip>

int main (void) {
    int x = 314159;
    std::cout << std::hex << x << " " << std::uppercase << x << std::endl;
    return 0;
}

which outputs:

4cb2f 4CB2F

edited Jun 21 '17 at 02:12

answered Nov 07 '10 at 09:25

paxdiablo

772,407
210
1,477
1,841

1

Will this modifier affect hex numbers only, or will it affect strings as well? – Jörgen Sigvardsson Nov 07 '10 at 10:03
2

Hex numbers and exponents in scientific notation. If you want to do strings, see http://stackoverflow.com/questions/735204/convert-a-string-in-c-to-upper-case – paxdiablo Nov 07 '10 at 10:10

score 1 · Answer 2 · answered Mar 03 '21 at 04:36

In C++20 you'll be able to use std::format to do this:

std::cout << std::format("{:X}\n", 0xABC);

Output:

ABC

In the meantime you can use the {fmt} library, std::format is based on. {fmt} also provides the print function that makes this even easier and more efficient (godbolt):

fmt::print("{:X}\n", 0xABC);

Disclaimer: I'm the author of {fmt} and C++20 std::format.

How can I stream hexadecimal numbers with A-F (rather than a-f)?

2 Answers2