deleting all field headers except ...

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Is there a way to use formail to delete all field headers except a particular
list of them?  I'd like to do something like:

$ formail -I "" -u From < foo

and have this only print out the From field header.  This doesn't seem to
work, however.  Given that I only have a single pipe in the particular
script I'll be writing, I need to have a single program which has this
functionality.  Perhaps there's a way to do this in sed?

Thanks.


- -- 
Internet: dummy(_at_)c2(_dot_)org                   In real life: Robert Brown,
URL: http://www.c2.org/~dummy                          in sunny Berkeley, CA
       >> Leonardo da Vinci didn't eat meat. <<        waiting for The Big One
> > A child will cost you $12,000/year on average. <<  (510) 464-4604

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