Is there a command to list AWS instances that results in short output?

Question

I have my AWS CLI set up and can use aws ec2 describe-instances to get the json object returned that describes all the known details of my instances. Is there an easy way to get just a short list, like instance name and instance id?

I want to be able to work with my instances on the command-line, but to get the instance ids (which commands like start-instances require), I have to scroll through all that output.

Answer 1

Yes, via the --query option.

This option allows you to filter down and return specific elements from the structure. There is a special wildcard [*] notation that allows you to iterate over lists of objects; we'll use this to iterate over the list of EC2 instances and return your desired values.

Retrieving InstanceID, Instance Tag Name as JSON:

aws ec2 describe-instances --query 'Reservations[*].Instances[*].[InstanceId, Tags[?Key==`Name`].Value | [0]]'

[
    [
        [
            "i-abcd1234",
            "MyFirstInstance"
        ]
    ],
    [
        [
            "i-efgh5678",
            "MySecondInstance"
        ]
    ]
]

Retrieving InstanceID, Instance Tag Name as Text:

If you don't want to work with json, you can also add the --output option to output text:

aws ec2 describe-instances --query 'Reservations[*].Instances[*].[InstanceId, Tags[?Key==`Name`].Value | [0]]' --output text

i-abcd1234      MyFirstInstance
i-efgh5678      MySecondInstance

Further reading:

• AWS CLI Documentation - Controlling Command Output