Equivalent of formatted printf (c) to formatted cerr in C++

Question

I want an equivalent for printf("%2.2x", var); to cerr<< in C++.
code:

typedef unsigned char byte;  
static byte var[10];  
for(i=1; i<10; i++)  
   printf("%2.2x", var[i]);

The idea is to redirect the debugging to a file like this: ./myprog 2>out.txt.
If I don't ask too much I would like to receive explanations too.
Thanks!

Answer 1

Use fprintf(stderr, ...), e.g.:

fprintf(stderr, "%2.2x", var[i]);

Answer 2

You can do this with the stream manipulators in C++, for example:

#include <iostream>
#include <iomanip>
...
std::cerr << std::hex << std::setw(2) << std::setprecision(2) << (int)var[i];

I think setw is correct here, but have a play around, and some more are listed here: http://www.cplusplus.com/reference/iomanip/