How to save initial configuration? (program installation)

[Jason Zapman II]

I've written a program.  To install this program, I'm going to need to
initialize some stuff for the users environment, specifically the name/
location of an internal state file.

Currently, I'm hard coding the location of this file, but that's in-
elegant.  What I'd like to do is just ask the user, with a suggested
default.

My question is how do I save this answer?  It's kind of a chicken-and-
egg problem.

The only solution I've thought of is to write something that's self
modifying, but that's ugly (go in, grep for this variable
initialization, re-write that line with the new value, quit).  Is
there a better way to do this?  There almost has to be...

If not, are there some 'best practices' on how to do the self-
modification?

Thanks for any help;
Jason