sort output of describe-instances?

Question

I saw the previous question on this topic, but the answer was just "pipe it to a scripting language!", which I find unsatisfying. I know that JMESPath has sort_by, and sort, but I can't figure out how to use them.

I have

aws ec2 describe-instances \
   --filters "Name=tag:Group,Values=production" "Name=instance-state-name,Values=running" "Name=tag:Name,Values=prod-*-${CURRENT_SHA}-*" \
   --query 'Reservations[*].Instances[*].[LaunchTime,InstanceId,PrivateIpAddress,Tags[?Key==`Name`] | [0].Value]' \
   --output table

And it outputs the right data, just in a random order. I want to sort by the last column of the data, Tag Name, aka Tags[?Key==`Name`], which in raw form looks like this:

{
  "Tags": [{
    "Value": "application-server-ab3634b34364a-2",
    "Key": "Name"
  }, {
    "Value": "production",
    "Key": "Group"
  }]
}

Thoughts?

Answer 1

short answer

add

[] | sort_by(@, &[3])

at the end of your expression. The brackets ([]) will flatten the structure, sort_by(...) will sort the result (which is a four-column table) by the fourth column. The full query will be:

--query 'Reservations[*].Instances[*].[LaunchTime,InstanceId,PrivateIpAddress,Tags[?Key==`Name`] | [0].Value][] | sort_by(@, &[3])'

long answer

inspecting your current query result

According to the describe-instances docs, the structure of the describe-instances output looks like this:

{
  "Reservations": [
    {
      "Instances": [
        {
          "LaunchTime": "..LaunchTime..",
          "InstanceId": "R1I1",
          "PrivateIpAddress": "..PrivateIpAddress..",
          "Tags": [{"Key": "Name", "Value": "foo"}]
        },
        {
          "LaunchTime": "..LaunchTime..",
          "InstanceId": "R1I2",
          "PrivateIpAddress": "..PrivateIpAddress..",
          "Tags": [{"Key": "Name", "Value": "baz"}]
        }
      ]
    },
    {
      "Instances": [
        {
          "LaunchTime": "..LaunchTime..",
          "InstanceId": "R2I1",
          "PrivateIpAddress": "..PrivateIpAddress..",
          "Tags": [{"Key": "Name", "Value": "bar"}]
        }
      ]
    }
  ]
}

Using your original query

--query 'Reservations[*].Instances[*].[LaunchTime,InstanceId,PrivateIpAddress,Tags[?Key==`Name`] | [0].Value]'

will output

[
  [
    [
      "..LaunchTime..",
      "R1I1",
      "..PrivateIpAddress..",
      "foo"
    ],
    [
      "..LaunchTime..",
      "R1I2",
      "..PrivateIpAddress..",
      "baz"
    ]
  ],
  [
    [
      "..LaunchTime..",
      "R2I1",
      "..PrivateIpAddress..",
      "bar"
    ]
  ]
]

flattening the query result

You can see in the above result of your query that you're getting a list of tables ([[{},{}],[{}]]). I suppose you instead want a single non-nested table ([{},{},{}]). To achieve that, simply add [] at the end of your query, i.e.

--query 'Reservations[*].Instances[*].[LaunchTime,InstanceId,PrivateIpAddress,Tags[?Key==`Name`] | [0].Value][]'

This will flatten the structure, resulting in

[
  [
    "..LaunchTime..",
    "R1I1",
    "..PrivateIpAddress..",
    "foo"
  ],
  [
    "..LaunchTime..",
    "R1I2",
    "..PrivateIpAddress..",
    "baz"
  ],
  [
    "..LaunchTime..",
    "R2I1",
    "..PrivateIpAddress..",
    "bar"
  ]
]

Now it's time to sort the table.

sorting the table

When using sort_by you shouldn't forget to prepend the expression by & (ampersand). This way you specify a reference to that expression, which is then passed to sort_by.

example: data | sort_by(@, &@) is equivalent to data | sort(@).

The TagName in the table you create ([LaunchTime,InstanceId,PrivateIpAddress,TagName]) is the fourth column. You can get that column by piping the table to the expression [3]:

TableExpression | [3]

But instead, you want to sort the table by the fourth column. You can do so like this:

TableExpression | sort_by(@, &[3])

and the resulting query will be:

--query 'Reservations[*].Instances[*].[LaunchTime,InstanceId,PrivateIpAddress,Tags[?Key==`Name`][] | [0].Value] | sort_by(@, &[3])'

Query result:

[
  [
    "..LaunchTime..",
    "R2I1",
    "..PrivateIpAddress..",
    "bar"
  ],
  [
    "..LaunchTime..",
    "R1I2",
    "..PrivateIpAddress..",
    "baz"
  ],
  [
    "..LaunchTime..",
    "R1I1",
    "..PrivateIpAddress..",
    "foo"
  ]
]