printf all characters in a string using HEX i.e. printf("%X", string.c

I'm on an embedded Linux platform which uses C but also printf for logging.

I receive data in string type - "\241\242" - but they're unprintable characters.

On the sender side, I type in a hex number in string format i.e. "A1A2" but the sender encodes it as the number 0xA1A2 so on the receiver, I cannot use printf("%s", thing.c_str())

I can use printf("%X") but only for one character at a time in a for loop printf("%X", thing[i]). The for-loop would be ok except that since I need to use the logging macro, each hex character comes out on a separate line.

QUESTION

Is there a way to use ONE printf("%X") to print all the characters in the string as hex?
Something like printf("%X\n", uuid.c_str());

The output of below code.

500E00
A1A2

I think it's printing the pointer from .c_str() as a hex number.

// Example program
#include <iostream>
#include <string>
using namespace std;

int main()
{
  string uuid = "\241\242";
  
  printf("%X\n", uuid.c_str());
  
  for(int i=0; i < uuid.size(); i  )
  {
    printf("%hhX", uuid[i]);   
  }  

}

CodePudding user response：

Is there a way to use ONE printf("%X") to print all the characters in the string as hex?

No.

Is there a way

You can write your own printf with your own specifier that will do whatever you want. You might be interested in printk used in linux kernel for inspiration, I think that would be %*pEn or %*ph or %*phN.

On glibc you can add your own format specifier https://www.gnu.org/software/libc/manual/html_node/Customizing-Printf.html .