returns a pointer to the null-terminated pathname of the terminal device
that is open on the file descriptor fd, or NULL on error
(for example, if fd is not connected to a terminal).
The return value may point to static data, possibly overwritten by the
stores this pathname in the buffer
returns a pointer to a pathname on success.
On error, NULL is returned, and
is set appropriately.
returns 0 on success, and an error number upon error.
Bad file descriptor.
File descriptor does not refer to a terminal device.
was too small to allow storing the pathname.