vi command output question

[utzoo!decvax!harpo!seismo!dmy]

Is there any way of putting the output of a ":" command in vi
into the current file (or better yet a specifiable file)?
In particular, I want to put the output of :f or <^G> into a file,
so that a startup script for vi can read this file and figure out
where I last left vi and (optionally) put me back there.

--dmy-- (David Yablon, NoVi, decvax!harpo!seismo!dmy)