V8/usr/src/cmd/Mail/manual/cmds/visual

.ip \fBvisual\fP
It is often useful to be able to invoke one of two editors,
based on the type of terminal one is using.  To invoke
a display oriented editor, you can use the
.b visual
command.  The operation of the
.b visual
command is otherwise identical to that of the
.b edit
command.
.ne 2v+\n(psu
.sp \n(psu
Both the
.b edit
and
.b visual
commands assume some default text editors.  These default editors
can be overridden by the valued options
.q EDITOR
and
.q VISUAL
for the standard and screen editors.  You might want to do:
.(l
set EDITOR=/usr/ucb/ex VISUAL=/usr/ucb/vi
.)l