How to print 1 byte with printf?

Question

I know that when using %x with printf() we are printing 4 bytes (an int in hexadecimal) from the stack. But I would like to print only

Answer 1

You need to be careful how you do this to avoid any undefined behaviour.

The C standard allows you to cast the int to an unsigned char then print the byte you want using pointer arithmetic:

int main()
{
    int foo = 2;
    unsigned char* p = (unsigned char*)&foo;
    printf("%x", p[0]); // outputs the first byte of `foo`
    printf("%x", p[1]); // outputs the second byte of `foo`
}

Note that p[0] and p[1] are converted to the wider type (the int), prior to displaying the output.