Trouble with an object of objects (no arrays)

[jblaine]

I'm trying to make productive use of jq (cool tool) with input like the following. I am trying to extract the corresponding object's "dns_name" for any object having a specified "state". I failed to figure out any way to do this from the tutorial and manual. Any ideas?

{
  "i-09xxxxxx": {
    "id": "i-09xxxxxx",
    "keyname": "blah",
    "dns_name": "ec2-REDACTED.compute-1.amazonaws.com",
    "created_at": "Sat Aug 18 18:31:48 UTC 2012",
    "state": "running",
    "tags": "{\"node-type\"=>\"bastion\", \"Name\"=>\"bastion\"}",
    "private_dns_name": "ip-REDACTED.ec2.internal"
  },
  "i-0a8bxxxx": {
    "id": "i-0a8bxxxx",
    "keyname": "jblaine",
    "dns_name": null,
    "created_at": "Wed Dec 26 20:32:15 UTC 2012",
    "state": "terminated",
    "tags": "{\"Created-By\"=>\"Puppet\"}",
    "private_dns_name": null
  },
  "i-cedxxxxx": {
    "id": "i-cedxxxx",
    "keyname": "foo",
    "dns_name": null,
    "created_at": "Thu Sep 20 05:36:41 UTC 2012",
    "state": "stopped",
    "tags": "{\"Name\"=>\"graph-inserter-2\"}",
    "private_dns_name": null
  }
}

[stroan]

jq '.[] | select(.state == "running").dns_name'

This should do the trick I think.

[jblaine]

Thank you very much, that works.

I get 90% of why that works. The .[] is magic to me.

"If you use the .[foo] syntax, but omit the index entirely, it will return all of the elements of an array. "

But there was no array. :)

[stroan]

Ah, that must be undocumented. [] on an object returns all the values.