How do I use --query parameter in aws rds describe-db-instances command

Question

Here is the Synopsis of describe-db-instances

 [--db-instance-identifier <value>]
 [--filters <value>]
 [--cli-input-json <value>]
 [--starting-token <value>]
 [--page-size <value>]
 [--max-items <value>]
 [--generate-cli-skeleton <value>]

I want to know what values in I should use for -db-instance-identifier, --filters, ... ?

If I want to use aws rds describe-db-instances --query, what values I must use in the --query ? Below is the example I got from internet: where are these values from (DBInstanceArn, Engine, DBInstanceIdentifier in --query) ???

aws rds describe-db-instances \
    --query 'DBInstances[*].[DBInstanceArn,Engine,DBInstanceIdentifier]' \
    --output text

And what is the syntax of --query 'DBInstances[*].[DBInstanceArn,Engine,DBInstanceIdentifier]'

Solution

The --query parameter is available in most of the aws cli commands. It helps you control the output of the command execution. You might want to read http://docs.aws.amazon.com/cli/latest/userguide/controlling-output.html#controlling-output-filter which details how it works in general.

In the case of aws rds describe-db-instances (you can check doc or run aws rds describe-db-instances help to find out about the output values), the execution of the command will return a long list of attributes for the DB, for each of the DB you run :

{
    "DBInstances": [
        {
            "PubliclyAccessible": true,
            "MasterUsername": "TestDB",
            "MonitoringInterval": 0,
            "LicenseModel": "general-public-license",
            "VpcSecurityGroups": [
                {
                    "Status": "active",
                    "VpcSecurityGroupId": "sg-5a69722b"
                }
            ],
            "CopyTagsToSnapshot": false,
            "OptionGroupMemberships": [
                {
                    "Status": "in-sync",
                    "OptionGroupName": "default:mysql-5-6"
                }
            ],
            "PendingModifiedValues": {
                "MasterUserPassword": "****"
            },
            "Engine": "mysql",
            "MultiAZ": false,
            "DBSecurityGroups": [],
            "DBParameterGroups": [
                {
                    "DBParameterGroupName": "default.mysql5.6",
                    "ParameterApplyStatus": "in-sync"
                }
            ],
            "AutoMinorVersionUpgrade": false,
            "PreferredBackupWindow": "06:52-07:22",
            "DBSubnetGroup": {
                "Subnets": [
                    {
                        "SubnetStatus": "Active",
                        "SubnetIdentifier": "subnet-50dea718",
                        "SubnetAvailabilityZone": {
                            "Name": "us-east-1d"
                        }
                    },
                    {
                        "SubnetStatus": "Active",
                        "SubnetIdentifier": "subnet-c5bba9a0",
                        "SubnetAvailabilityZone": {
                            "Name": "us-east-1b"
                        }
                    },
                    {
                        "SubnetStatus": "Active",
                        "SubnetIdentifier": "subnet-5ff24a05",
                        "SubnetAvailabilityZone": {
                            "Name": "us-east-1a"
                        }
                    },
                    {
                        "SubnetStatus": "Active",
                        "SubnetIdentifier": "subnet-98a39da4",
                        "SubnetAvailabilityZone": {
                            "Name": "us-east-1e"
                        }
                    },
                    {
                        "SubnetStatus": "Active",
                        "SubnetIdentifier": "subnet-42b42c4e",
                        "SubnetAvailabilityZone": {
                            "Name": "us-east-1f"
                        }
                    },
                    {
                        "SubnetStatus": "Active",
                        "SubnetIdentifier": "subnet-4d28a961",
                        "SubnetAvailabilityZone": {
                            "Name": "us-east-1c"
                        }
                    }
                ],
                "DBSubnetGroupName": "default",
                "VpcId": "vpc-1b70fd62",
                "DBSubnetGroupDescription": "default",
                "SubnetGroupStatus": "Complete"
            },
            "ReadReplicaDBInstanceIdentifiers": [],
            "AllocatedStorage": 5,
            "DBInstanceArn": "arn:aws:rds:us-east-1:325979260958:db:testdb",
            "BackupRetentionPeriod": 0,
            "DBName": "TestDB",
            "PreferredMaintenanceWindow": "wed:10:19-wed:10:49",
            "DBInstanceStatus": "creating",
            "IAMDatabaseAuthenticationEnabled": false,
            "EngineVersion": "5.6.35",
            "AvailabilityZone": "us-east-1e",
            "DomainMemberships": [],
            "StorageType": "gp2",
            "DbiResourceId": "db-5VK47WZ6OTS5VEA7OJUF4XH5OI",
            "CACertificateIdentifier": "rds-ca-2015",
            "StorageEncrypted": false,
            "DBInstanceClass": "db.t2.micro",
            "DbInstancePort": 0,
            "DBInstanceIdentifier": "testdb"
        }
    ]
}

You might not be interested into all those elements but want to specifically get subpart of the list. Thats when you will specify the attributes using the --query parameter

I can limit the number of elements to DBInstanceArn, Engine and DBInstanceIdentifier by running the following

$ aws rds describe-db-instances --query 'DBInstances[*].[DBInstanceArn,Engine,DBInstanceIdentifier]'
[
    [
        "arn:aws:rds:us-east-1:325979260958:db:testdb",
        "mysql",
        "testdb"
    ]
]

The syntax used in the query parameter is JMESPath. As the output of the command is a JSon document, it helps you parse it.

Comments

[TuiNho]

How to use the " aws rds describe-db-instances --querry " ?

[John Rotenstein]

Welcome to StackOverflow! Unfortunately, your question is unclear. Please Edit your question and let us know what you are trying to accomplish, what you have tried so far and what errors you are experiencing. For tips on asking a good question, see: How do I ask a good question?

[John Rotenstein]

Are you just asking for a link to the documentation?

[TuiNho]

Frederic, Thank you very much indeed for your great help. I extremely appreciated it.