Are terminal writes atomic?

[Guy Harris]

>Indeed I should have qualified my statement, however almost everyone is
>familiar with Rochkind's _Advanced Unix Programming_ book, and they are
>aware it is a SYSTEM V book, not a 4BSD Unix book.
>Under System V, it is a known undocumented item.  By undocumented, I mean
>it was left out of the documentation and under ALL true Unix System V systems,
>atomic writes at the system call level are guaranteed.

And you believe that, in fact, *terminal* writes are atomic on S5?  I
don't - and I've checked the S5R3 code.  While S5 *does*, in fact, lock
the inode on "read"s and "write"s in some cases - as does 4.3BSD, in
fact - neither of them do so if the file is a character special file,
which terminals are.  Chris Torek's scenario appears to apply to S5 as
well.