This assumes you have already configured the aws command line tool. If not, check out my article on Getting Started with the AWS CLI.

• An IAM Policy allows certain actions (such create) on certain resources (such as EC2)
• An IAM User is typically a users account (such as john.doe) that contains an IAM Identity-Based Policy that allows certain actions (such as list) on certain resources (such S3)
• An IAM Role contains an IAM Policy that allows certain actions (such create) on certain resources (such as EC2). Let's say the Identity-Based Policy attached to john.doe does NOT allow "create S3"
  • The Role that allows "create S3" could be attached to john.doe - or, john.doe could Assume the Role:
    • Assume Role or Switch Role using Python boto3
    • Assume Role or Switch Role using Terraform
    • Assume Role or Switch Role using the AWS CLI
  • Often, a Role will have two Policies:
    • Trust Relationship
    • Permission Policy

The aws iam list-policies command can be used to list all of the available policies.

aws iam list-policies

And here is an example of how to limit the output using the --query option.

aws iam list-policies --query 'Policies[?PolicyName==`ReadOnlyAccess`]'

Something like this should be returned.

{
    "Policies": [
        {
            "PolicyName": "AdministratorAccess",
            "PolicyId": "ANPAIWMBCKSKIEE64ZLYK",
            "Arn": "arn:aws:iam::aws:policy/AdministratorAccess",
            "Path": "/",
            "DefaultVersionId": "v1",
            "AttachmentCount": 2,
            "PermissionsBoundaryUsageCount": 0,
            "IsAttachable": true,
            "CreateDate": "2015-02-06T18:39:46+00:00",
            "UpdateDate": "2015-02-06T18:39:46+00:00"
        },
        {
            "PolicyName": "PowerUserAccess",
            "PolicyId": "ANPAJYRXTHIB4FOVS3ZXS",
            "Arn": "arn:aws:iam::aws:policy/PowerUserAccess",
            "Path": "/",
            "DefaultVersionId": "v4",
            "AttachmentCount": 0,
            "PermissionsBoundaryUsageCount": 0,
            "IsAttachable": true,
            "CreateDate": "2015-02-06T18:39:47+00:00",
            "UpdateDate": "2019-03-20T22:19:03+00:00"
        }
    ]
}