Listing instance name among other data with aws-cli 1.3.6

Question

Using aws-cli 1.3.6 I am trying to get a simple table of my ec2 instances with the Name and state. I have been looking at the --query and JMESpath documentation and I have been able to select the "Value" item of a Map which "Key" item is equal to Name. This is useful to get the instance-name. Therefore, the code below seems to work

aws ec2 describe-instances --output table --query 'Reservations[].Instances[].Tags[?Key==`Name`].Value' 

And delivers this:

------------------- |DescribeInstances| +-----------------+ |  Name1          | |  Name2          | +-----------------+ 

However, if I want to add the state, things get not as I would have expected. Using

aws ec2 describe-instances --output table --query 'Reservations[].Instances[].[Tags[?Key==`Name`].Value,State.Name]' 

Delivers

------------------- |DescribeInstances| +-----------------+ |  Name1          | |  stopped        | |  Name2          | |  stopped        | +-----------------+ 

instead of a two column table with name and state.

If we turn the output to JSON, we can see that the Tags selection returns a list (one-element list) and that's probably the issue:

[     [         [             "Name1"         ],         "stopped"     ],     [         [             "Name2"         ],         "stopped"     ] ] 

I have not been able to turn this list into an scalar by selecting the first element. This, does not work. Returns an empty list as the Name.

aws ec2 describe-instances --output json --query 'Reservations[].Instances[].[Tags[?Key==`Name`].Value[0],State.Name]' 

The same as this

aws ec2 describe-instances --output json --query 'Reservations[].Instances[].[Tags[?Key==`Name`].Value[][0],State.Name]' 

The only way I have figured out of addressing this is by means of the join function. Since I only expect one element, it is ok but I seems to be a little bit hacky.

aws ec2 describe-instances --output table --query 'Reservations[].Instances[].[join(`,`,Tags[?Key==`Name`].Value),State.Name]'  --------------------------- |    DescribeInstances    | +-------------+-----------+ |  Name1      |  stopped  | |  Name2      |  stopped  | +-------------+-----------+ 

The question, therefore, is: is there any way of picking the first element of the result of the filter (?Key==XXXX) bearing in mind that suffixing it with [0] seems not to work?

Thanks in advance!

Answer 1

The question, therefore, is: is there any way of picking the first element of the result of the filter (?Key==XXXX) bearing in mind that suffixing it with [0] seems not to work?

The way you phrased this question hints towards the solution in fact, namely Pipe Expressions (only available as of version 1.3.7 of the aws-cli though, hence impossible to figure out at question time):

pipe-expression  = expression "|" expression 

A pipe expression combines two expressions, separated by the | character. It is similar to a sub-expression with two important distinctions:

1. Any expression can be used on the right hand side. A sub-expression restricts the type of expression that can be used on the right hand side.
2. A pipe-expression stops projections on the left hand side for propagating to the right hand side. If the left expression creates a projection, it does not apply to the right hand side.

The emphasized part is key, as shown in the subsequent examples, notably:

If you instead wanted only the first sub list, ["first1", "second1"], you can use a pipe-expression:

foo[*].bar[0] -> ["first1", "first2"] foo[*].bar | [0] -> ["first1", "second1"] 

Solution

Thus, applying a pipe expression yields the desired result:

aws ec2 describe-instances --output table \   --query 'Reservations[].Instances[].[Tags[?Key==`Name`] | [0].Value, State.Name]'  ---------------------------------- |        DescribeInstances       | +--------------------+-----------+ |  Name1             |  stopped  | |  Name2             |  stopped  | +--------------------+-----------+ 

Answer 2

#!/bin/bash for r in `aws ec2 describe-regions --query Regions[*].RegionName --output text` do      #echo $r     aws ec2 describe-instances --region $r --query 'Reservations[*].Instances[*].{ID:InstanceId, type:InstanceType, launched:LaunchTime, name:Tags[?Key==`Name`].Value[]}' --output json | jq --arg R $r -r '.[] | .[] | [$R, .ID, .type, .launched, .name[0]] | @csv'  done 

Output:

"us-east-1","i-054f8253b9ed0746d","t2.micro","2018-10-31T01:57:52.000Z","xxx" "us-east-1","i-0638792b8b3057ce2","t2.nano","2018-10-23T03:49:24.000Z","yyy"