Is UNIX(TM) Multi-User?

[Barry Margolin]

In article <11945 at steinmetz.ge.com> davidsen at crdos1.UUCP (bill davidsen) writes:
>  Any multitasking o/s can be a multiuser system, provided that the user
>agent (shell or whatever) is a normal process. Given this, you can have
>multiple user agents running, connected to several users.

If "multiuser" means that more than one person can use the system
simultaneously, that is true, but I don't think this is a reasonable
definition of multiuser.

For example, Symbolics Lisp Machines run a multitasking O/S, and you
can have multiple user agents (one on the bitmapped console, others on
Telnet clients, X servers, or serial terminals) , but all the
processes share a single address space.  In particular, the userid and
the file server connections are global variables, so all the processes
are considered to be owned by the same user.  So, multiple people can
be using the system, but only one "user" is ever logged in.  There are
other pieces of global state that might not cause trouble, but would
probably cause confusion among multiple users.


Barry Margolin
Thinking Machines Corp.

barmar at think.com
{uunet,harvard}!think!barmar