[libvirt] [PATCH] virsh: add custom readline generator

Lai Jiangshan laijs at cn.fujitsu.com
Wed Jul 20 08:42:49 UTC 2011

On 06/28/2011 05:29 PM, Michal Privoznik wrote:
> On 27.06.2011 21:39, Eric Blake wrote:
>> On 06/27/2011 12:06 PM, Michal Privoznik wrote:
>>>> That is, if you have command-based custom generators, then each command
>>>> has to repeat parsing functionality, then call back to common list
>>>> generators; whereas if you have option-based custom generators, then you
>>>> have fewer callbacks because all the smarts are tied to well-typed
>>>> options, and after all, it is the type of each option that determines
>>>> which list to generate, more than the type of the command that includes
>>>> the option.
>>> I was thinking about same feature and started to work on it during this
>>> weekend. But I ran into a problem. Basically, what I intended to
>>> implement, is:
>>> 1.) expand struct vshCmdDef for a char *(*callback) (const char *text,
>>> int state). But for real benefit, we need connection object, so we could
>>> e.g. list only inactive networks for 'net-start' command. And this is
>>> the problem, because we would have to make this object global (since
>>> readline functions does not allow passing any opaque value).
>> As gross as it is, a global object isn't entirely bad - virsh is
>> single-threaded.  And even if we want to make virsh threaded at some
>> point, I still think we can get away with adding a thread-local access
>> scheme.
>>> 2.) expand each command definition with its own completer. So e.g. for
>>> start commands we could only list inactive domains, networks, pools,
>>> whatever. For destroy only active objects. And so on.
>> So maybe we want both - an option-based completer that generates the
>> initial list, and a command-based completer that can then prune out
>> irrelevant options?
> Well, I would say that is the highest goal to be achieved. Although that
> implies parsing during options generation.
> But I don't think I get it. Option-based completer generates list for
> given option, command-based completer generates list for given command
> (entries from this list are options). Take detach-interface for
> instance. This have some options:
> --mac: here we want option-based completer to list mac addresses of a
> NICs of a domain specified by
> --domain: since this could be left out we want here command-base
> completer to either list all domains, or list only those domains which
> have a NIC.
> So then we get:
> # detach-interface <TAB><TAB>
> --mac --persistent domain1 domain2
> # detach-interface domain1 --mac <TAB><TAB>
> 00:11:22:33:44:55 01:23:45:67:89
> My point is - I can't see any pruning here. But maybe I've chosen wrong
> example. However, this example shows we need both types of completer.
> Michal

Hi, All

Are their any progress now?


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