On 08/07/2012 02:30 PM, Markus Armbruster wrote: > Peter Maydell <peter.mayd...@linaro.org> writes: > >> On 7 August 2012 20:55, Markus Armbruster <arm...@redhat.com> wrote: >>> Anthony Liguori <anth...@codemonkey.ws> writes: >>>> Perhaps we could add a QEMUMachine parameter that indicates that the >>>> machine doesn't start without special options. >>> >>> Recommend to make it a string that lists the mandatory options. >> >> How are you going to say "need either option foo or option bar" ? I'm >> pretty sure we have some of those (eg "either you need to pass a flash >> image or a kernel"). > > Yes, we do. > > The string should be suitable for inserting into -help.
Convention in other programs' -help output is to express a mandatory
selection from mutually exclusive options using {}, as in:
{ -foo | -bar }
If both options can be used together, but cannot both be omitted, then
this style works:
{ -foo [ -bar ] | -bar }
Mutually exclusive options, but where omission is okay, would then be:
[ { -foo | -bar } ]
or even this variant, to express the default when both are omitted:
{ -foo | [ -bar ] }
Using strings with metasyntax like that should be usable in qemu -help.
--
Eric Blake ebl...@redhat.com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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