How to print unsigned char[] as HEX in C++?

问题:

I would like to print the following hashed data. How should I do it?

unsigned char hashedChars[32];
SHA256((const unsigned char*)data.c_str(),
       data.length(), 
       hashedChars);
printf("hashedChars: %X\n", hashedChars);  // doesn't seem to work??

回答1:

The hex format specifier is expecting a single integer value but you're providing instead an array of char. What you need to do is print out the char values individually as hex values.

printf("hashedChars: ");
for (int i = 0; i < 32; i++) {
  printf("%x", hashedChars[i];
}
printf("\n");

Since you are using C++ though you should consider using cout instead of printf (it's more idiomatic for C++.

cout << "hashedChars: ";
for (int i = 0; i < 32; i++) {
  cout << hex << hashedChars[i];
}
cout << endl;