From The Linux Programming Interface

> In an interactive shell, these three file
descriptors 0, 1 and 2 normally refer to the terminal under which the shell is running.

 1. Does "the terminal under which the shell is running" mean the
 controlling terminal of the session to which the interactive shell
 belongs?

 If yes, what if the shell's session doesn't have a controlling terminal?
 2. When the shell is created from its parent process, will the shell automatically create connection betwee file descriptors 0, 1 and 2 and the terminal, in each of
 the following cases (inheritance from the parent process of the shell):
 
 - if "the terminal under which the shell is running" or the controlling terminal has already been opened at a file descriptor
 which is not 0, 1 and 2? 
 
 - if the file descriptors 0, 1 and 2 have already been connected to a file which is not "the terminal under which the shell is running"
 or the controlling terminal?
 3. What if the shell in the quote is noninteractive?

Thanks.

Btw, just assume "shell" is POSIX or bash.