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How to cast from hexadecimal to string in C?

Answer 1

+1 A:

You cannot cast from a number to a string in C. You'll have to call a function for that purpose.

Martinho Fernandes 2009-11-20 23:07:42

Answer 2

+9 A:

You cannot simply 'cast', you will need to use sprintf to do the convertion:

unsigned int hex = 0xABC123FF;
char hexString[256];
sprintf(hexString, "0x%08X", hex);

If you want to 'cast' it to string in order to print it, you can use printf directly:

unsigned int hex = 0xABC123FF;
printf("0x%08X", hex);

LiraNuna 2009-11-20 23:09:13

How about `snprintf`? :-)

James McNellis 2009-11-20 23:10:36

I thought `snprintf` is BSD only?

LiraNuna 2009-11-20 23:12:14

It's in the C99 standard library.

James McNellis 2009-11-20 23:13:18

Oh wow, I did not know that. sadly, OP did not give platform/compiler, so I would like to keep it compatible with non-C99 compilers (read as: MSVC).

LiraNuna 2009-11-20 23:15:00

MSVC has a version called `_snprintf`.

Greg Hewgill 2009-11-20 23:19:01

I should mention that `_snprintf` does *not* nul-terminate the output string if the formatted string is longer than the buffer, so one should wrap `_snprintf` inside a `snprintf` function that calls `_snprintf` and then explicitly terminates the buffer (to make it behave the same as `snprintf` on other platforms).

Greg Hewgill 2009-11-20 23:27:51

Yay.. let's complicate the OP's request even more! Look, The OP is most definitely a beginner. Do you want to complicate his understanding by using `#ifdef`'s to re-define `_snprintf` and to handle the problem Greg suggested? I'm sorry, but I won't complicate this answer for a beginner.

LiraNuna 2009-11-20 23:32:04

Not to mention no 32bit or 64bit number has 256 hexadecimal digits.

LiraNuna 2009-11-20 23:34:43

My comments were not meant for the OP, but rather for people who might come across this page in the future and believe that `sprintf` or `_snprintf` is a good, safe idea.

Greg Hewgill 2009-11-20 23:36:21

`sprintf` is perfectly safe when used the way LiraNuna did. An upper bound on the number of digits produced by `%x` can be determined from the range of the input number.

caf 2009-11-21 01:22:51

always use "08x" instead "8x"

Arabcoder 2009-11-21 13:17:58

Answer 3

A:

Just stumbled over this old thread. Who says one cannot cast hex to string? That's a lie, I can:

unsigned int hex = 0xABC123FF;
char *str = (char*)&hex;

Okay it doesn't make sense printing it as C string (zero terminated), but I casted it ;)

AndiDog 2010-01-14 12:07:07

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