On Sat, Jul 26, 2014 at 01:45:46PM -0400, Jonathan Callen wrote: *snip* > If you want to say "At most one of the flags 'foo', 'bar', and 'baz' > may be selected", then you say it like so (requires EAPI=5): > > REQUIRED_USE="?? ( foo bar baz )" > > If you want to say "Exactly one of the flags ...", then you use: > > REQUIRED_USE="^^ ( foo bar baz )" > > And, as always, you can say "At least one of the flags ..." with: > > REQUIRED_USE="|| ( foo bar baz )" > > While each of these can be written using the "foo? ( !bar )"-type > primitives, the messages portage outputs are generally better with > '??', '^^', and '||', as you might see something like: > > " > The following REQUIRED_USE flag constraints are unsatisfied: > at-most-one-of ( foo bar baz ) > " > > Which is, in my opinion, more readable.
Now I understand what ciaranm was suggesting in pkg_pretend. Note, this
is not shell syntax, but it conveys the idea...
pkg_pretend() {
count=0
for x in foo bar bas; do
use $x && count += 1
done
# Now, if count == 0 none of the flags are used, and
# if count > 1 more than one is used, so die whenever appropriate
# with any error message you choose.
}
William
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