[gentoo-user] bash wizardry needed: PATH and MANPATH grow and grow and grow

[Kevin O'Gorman]

I have inherited some pretty gnarly dotfiles that I don't really want to
fool with too much,
but I'm also unhappy with what they do to my environment.  They keep adding
the
same things over and over to some of the variables.

Does anyone know a nice little idiom for de-duping a colon-list like PATH or
MANPATH?
It has to retain one copy of each duplicate, preserving the order of *first*
appearances.
I know how to avoid duplicates when I do the coding myself:
       case :$PATH: in
             *:mynewthing:*) ;;
             *) export PATH=$PATH:mynewthing
       esac

I'm just not sure how best to turn the colon-list into something I can
iterate over.

Obviously, I use bash.

++ kevin

-- 
Kevin O'Gorman, PhD