Can you fool isatty AND log stdout and stderr separately?

Question

Problem

So you want to log the stdout and stderr (separately) of a process or subprocess, without the output being different from what you\'d see in the terminal i

Answer 1

Like this?

% ./challenge.py >stdout 2>stderr
% cat stdout 
This is a real tty :)
standard output data
% cat stderr 
standard error data

Because I cheated a little bit. ;-)

% echo $LD_PRELOAD
/home/karol/preload.so

Like so...

% gcc preload.c -shared -o preload.so -fPIC

I feel dirty now, but it was fun. :D

% cat preload.c
#include 

int isatty(int fd) {
    if(fd == 2 || fd == 1) {
        return 1;
    }
    return 0;
}

char* ttyname(int fd) {
    static char* fake_name = "/dev/fake";
    if(fd == 2 || fd == 1) {
        return fake_name;
    }
    return NULL;
}