How to print specific byte of unsigned integer?

Question

I'm attempting to write a program in C that examines bytes in memory and prints their contents. Given a 4-byte unsigned integer, what would a function look like that prints a specific byte of the integer to stdout in hexadecimal? Does printf have some sort of capability like this built-in?

Here's the interface of what I'm looking for.

// number - the integer to be examined
// order - the byte to be examined, with 0 being the lowest-order
//         (first) byte and 3 being the highest order (last) byte
void print_byte(unsigned number, unsigned order);

If it's important for the implementation, this would be a little-endian machine.

Posting some code for us to complement on & correct would be a better start ;-) — Mawg says reinstate Monica, Jan 28 '15 at 09:15
@phadej Disagree that this is a close match to the posted duplicate. The purported duplicate show how to extract from an integer to integer. This post needs asks how to "print" a specific byte. Certainly code could use the duplicate and then print the result, but tighter methods could exists by-passing the integer to integer conversion as suggested in my above comment. — chux - Reinstate Monica, Jan 28 '15 at 16:14
@Mawg Sorry, there really isn't any code. I always post some snippet if I can. I'm asking for something that I would assume to be a one-line thing considering C is good for dealing with individual bytes. This just isn't something that would be easily found in common textbooks is why I decided to ask here. — Jared, Jan 28 '15 at 18:31

score 0 · Answer 1 · edited Jan 28 '15 at 15:17

0

Please Try This...

#include <stdio.h>
void print_byte(unsigned number, unsigned order)
{
    unsigned i = 0;

    i = (number >> (8*order)) & 0x000000FF;

    printf("Number:0x%08x, Byte:%02x, Order:%d\n",number,i,order);

    return;
}

int main(void) {

    print_byte(0x1f2e3d4c,0);
    print_byte(0x1f2e3d4c,1);
    print_byte(0x1f2e3d4c,2);
    print_byte(0x1f2e3d4c,3);

    return 0;
}

edited Jan 28 '15 at 15:17

Jonathan Leffler

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answered Jan 28 '15 at 05:06

jjm

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1

Weird construction... As for trying, "try this" instead: `(number >> 8*order) & 0xFF`. – Jongware Jan 28 '15 at 08:13

score 0 · Answer 2 · answered Jan 28 '15 at 16:22

If using C99 or later, use the length modifier "hh" after shifting. This modifier will convert the integer to unsigned/signed char before printing. Use 8 or CHAR_BIT depending on meaning of "byte".

printf("%hhX", number >> (order * 8));

or

#include <limits.h>
printf("%hhX", number >> (order * CHAR_BIT));

How to print specific byte of unsigned integer?

2 Answers2