On Tue, May 31, 2016 at 12:22 PM, Anuradha Karuppiah
[off-list ref] wrote:

On Tue, May 31, 2016 at 11:59 AM, Stephen Hemminger
[off-list ref] wrote:

quoted

On Fri, 27 May 2016 21:37:14 -0700
Roopa Prabhu [off-list ref] wrote:

quoted

Sample output:
$bridge -j fdb show
[{
        "mac": "44:38:39:00:69:88",
        "dev": "swp2s0",
        "vlan": 2,
        "master": "br0",
        "state": "permanent"
    },{
        "mac": "00:02:00:00:00:01",
        "dev": "swp2s0",
        "vlan": 2,
        "master": "br0"
    },{
        "mac": "00:02:00:00:00:02",
        "dev": "swp2s1",
        "vlan": 2,
        "master": "br0"
    },{
        "mac": "44:38:39:00:69:89",
        "dev": "swp2s1",
        "master": "br0",
        "state": "permanent"
    },{
        "mac": "44:38:39:00:69:89",
        "dev": "swp2s1",
        "vlan": 2,
        "master": "br0",
        "state": "permanent"
    },{
        "mac": "44:38:39:00:69:88",
        "dev": "br0",
        "master": "br0",
        "state": "permanent"
    }
    ]

In most JSON I have seen, the output would be:

{
  "fdb" : [
     {
         "mac": "44:38:39:00:69:88",
         "dev": "swp2s0",
         "vlan": 2,
         "master": "br0",
         "state": "permanent"
     },
...
   ]
}

I.e never a bare array.

Yes Stephen, Adding an extra level would be one way to force the
format to json-object. And that would definitely be the way to do it
if we ever added a top level json dump - something like - "bridge -j
show".

But in the case of "bridge -j fdb show" that level is redundant. To be
consistent we would have to add that extra level to all json dumps
(even if they were already objects; such as the "bridge -j vlan
show").The google json style guide recommends against adding hierarchy
unless needed. And it is not that uncommon in java to have a
json-array of objects for e.g. http://json-schema.org/example1.html
talks about a schema that is an "array of products".

What do you recommend?

Hi Stephen,
We did a bit more digging around and found that other folks use json
output with top level array as well. Here’s a docker networks json
output sample -

vagrant@host-21 ~ $ docker network inspect red
[
    {
        "Name": "red",
        "Id": "d2fff9bafd7564c4012aa49f322fcd8f5743cc5ceb465dc218af5ba22c920981",
        "Scope": "global",
        "Driver": "overlay",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": {},
            "Config": [
                {
                    "Subnet": "10.252.20.0/24"
                }
            ]
        },
        "Internal": false,
        "Containers": {
            "c92084c1ebfb4f0a601537298c273078862207e3b564787ddd6ef564efbaca47":
{
                "Name": "ctr21",
                "EndpointID":
"e7468a70f13f1ea7b15445ab555374892ac41f71ea9023af1d9ede668bfd8742",
                "MacAddress": "02:42:0a:fc:14:03",
                "IPv4Address": "10.252.20.3/24",
                "IPv6Address": ""
            },
            "ep-9bfc004b4046512f0f0104fe022d3686f5237ae08475741f8d520552cbb63d45":
{
                "Name": "ctr22",
                "EndpointID":
"9bfc004b4046512f0f0104fe022d3686f5237ae08475741f8d520552cbb63d45",
                "MacAddress": "02:42:0a:fc:14:02",
                "IPv4Address": "10.252.20.2/24",
                "IPv6Address": ""
            }
        },
        "Options": {},
        "Labels": {}
    }
]

Adding an additional namespace to all the json outputs (just to avoid
a top-level json-array for some) seems redundant. If a namespace is
needed for other reasons we can definitely add it. So we think it
would be better to just go with the top-level json-array for a
list/set-of-objects outputs.

thanks
Anuradha.