ps and wall; How do they work?

[Dan Bernstein]

By far the simplest solution to the wall ``problem'' is to have a file,
/etc/itmp, listing only interactive sessions.

Interactive isn't a well-defined concept: it's defined by the way people
and programs use it. write, wall, talk, and other communication programs
will never touch a session unless it's interactive. People won't set up
program-controlled sessions as interactive. Everyone will be happy.

Of course, as many of you know, I think /etc/utmp serves the function of
/etc/itmp quite admirably. write, wall, and talk are already set up to
interpret /etc/utmp in this way; all we have to do is realize that the
convention has been established.

In article <13859 at smoke.BRL.MIL> gwyn at smoke.BRL.MIL (Doug Gwyn) writes:
> Specifically, you assume that there is a person looking at data that
> is sent to every tty special device.  In many environments, that is far
> from correct.  For example, in mine there are printers attached to some
> ttys, with generic output blocked deliberately to prevent messing up what
> they are in the process of printing, and other ttys are being used for
> binary communication between cooperating processes (one on the host and
> one in the terminal).

Such ttys wouldn't be listed as interactive. Problem solved.

---Dan