Use GetBucketLifecycleConfiguration with an AWS SDK or CLI

        /// <summary>
        /// Returns a configuration object for the supplied bucket name.
        /// </summary>
        /// <param name="client">The S3 client object used to call
        /// the GetLifecycleConfigurationAsync method.</param>
        /// <param name="bucketName">The name of the S3 bucket for which a
        /// configuration will be created.</param>
        /// <returns>Returns a new LifecycleConfiguration object.</returns>
        public static async Task<LifecycleConfiguration> RetrieveLifecycleConfigAsync(IAmazonS3 client, string bucketName)
        {
            var request = new GetLifecycleConfigurationRequest()
            {
                BucketName = bucketName,
            };
            var response = await client.GetLifecycleConfigurationAsync(request);
            var configuration = response.Configuration;
            return configuration;
        }

The following command retrieves the lifecycle configuration for a bucket named amzn-s3-demo-bucket:

aws s3api get-bucket-lifecycle-configuration --bucket amzn-s3-demo-bucket

Output:

{
    "Rules": [
        {
            "ID": "Move rotated logs to Glacier",
            "Prefix": "rotated/",
            "Status": "Enabled",
            "Transitions": [
                {
                    "Date": "2015-11-10T00:00:00.000Z",
                    "StorageClass": "GLACIER"
                }
            ]
        },
        {
            "Status": "Enabled",
            "Prefix": "",
            "NoncurrentVersionTransitions": [
                {
                    "NoncurrentDays": 0,
                    "StorageClass": "GLACIER"
                }
            ],
            "ID": "Move old versions to Glacier"
        }
    ]
}

class BucketWrapper:
    """Encapsulates S3 bucket actions."""

    def __init__(self, bucket):
        """
        :param bucket: A Boto3 Bucket resource. This is a high-level resource in Boto3
                       that wraps bucket actions in a class-like structure.
        """
        self.bucket = bucket
        self.name = bucket.name


    def get_lifecycle_configuration(self):
        """
        Get the lifecycle configuration of the bucket.

        :return: The lifecycle rules of the specified bucket.
        """
        try:
            config = self.bucket.LifecycleConfiguration()
            logger.info(
                "Got lifecycle rules %s for bucket '%s'.",
                config.rules,
                self.bucket.name,
            )
        except:
            logger.exception(
                "Couldn't get lifecycle rules for bucket '%s'.", self.bucket.name
            )
            raise
        else:
            return config.rules