Re: [Qemu-devel] For all targets and machine types: "start to monitor" smoke test

[Eric Blake]

On 08/07/2012 02:30 PM, Markus Armbruster wrote:
> Peter Maydell <address@hidden> writes:
> 
>> On 7 August 2012 20:55, Markus Armbruster <address@hidden> wrote:
>>> Anthony Liguori <address@hidden> 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   address@hidden    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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