Any advice on how a ruby script can set a config info that's per
parent process. In other words I want to be able to do something like:

  $ foo
  no setting

Then...

  $ foo 10

Which will store 10 somehow. And when I run foo again it can output
10.

  $ foo
  10

But if I close my terminal and/or open a new terminal then it will
have it's own setting.

  % foo
  no setting

Thanks.