Use GetBucketAcl with an Amazon SDK or CLI

        /// <summary>
        /// Get the access control list (ACL) for the new bucket.
        /// </summary>
        /// <param name="client">The initialized client object used to get the
        /// access control list (ACL) of the bucket.</param>
        /// <param name="newBucketName">The name of the newly created bucket.</param>
        /// <returns>An S3AccessControlList.</returns>
        public static async Task<S3AccessControlList> GetACLForBucketAsync(IAmazonS3 client, string newBucketName)
        {
            // Retrieve bucket ACL to show that the ACL was properly applied to
            // the new bucket.
            GetACLResponse getACLResponse = await client.GetACLAsync(new GetACLRequest
            {
                BucketName = newBucketName,
            });

            return getACLResponse.AccessControlList;
        }

bool AwsDoc::S3::GetBucketAcl(const Aws::String &bucketName,
                              const Aws::Client::ClientConfiguration &clientConfig) {
    Aws::S3::S3Client s3_client(clientConfig);

    Aws::S3::Model::GetBucketAclRequest request;
    request.SetBucket(bucketName);

    Aws::S3::Model::GetBucketAclOutcome outcome =
            s3_client.GetBucketAcl(request);

    if (!outcome.IsSuccess()) {
        const Aws::S3::S3Error &err = outcome.GetError();
        std::cerr << "Error: GetBucketAcl: "
                  << err.GetExceptionName() << ": " << err.GetMessage() << std::endl;
    }
    else {
        Aws::Vector<Aws::S3::Model::Grant> grants =
                outcome.GetResult().GetGrants();

        for (auto it = grants.begin(); it != grants.end(); it++) {
            Aws::S3::Model::Grant grant = *it;
            Aws::S3::Model::Grantee grantee = grant.GetGrantee();

            std::cout << "For bucket " << bucketName << ": "
                      << std::endl << std::endl;

            if (grantee.TypeHasBeenSet()) {
                std::cout << "Type:          "
                          << GetGranteeTypeString(grantee.GetType()) << std::endl;
            }

            if (grantee.DisplayNameHasBeenSet()) {
                std::cout << "Display name:  "
                          << grantee.GetDisplayName() << std::endl;
            }

            if (grantee.EmailAddressHasBeenSet()) {
                std::cout << "Email address: "
                          << grantee.GetEmailAddress() << std::endl;
            }

            if (grantee.IDHasBeenSet()) {
                std::cout << "ID:            "
                          << grantee.GetID() << std::endl;
            }

            if (grantee.URIHasBeenSet()) {
                std::cout << "URI:           "
                          << grantee.GetURI() << std::endl;
            }

            std::cout << "Permission:    " <<
                      GetPermissionString(grant.GetPermission()) <<
                      std::endl << std::endl;
        }
    }

    return outcome.IsSuccess();
}

//! Routine which converts a built-in type enumeration to a human-readable string.
/*!
 \sa GetGranteeTypeString()
 \param type Type enumeration.
*/

Aws::String GetGranteeTypeString(const Aws::S3::Model::Type &type) {
    switch (type) {
        case Aws::S3::Model::Type::AmazonCustomerByEmail:
            return "Email address of an AWS account";
        case Aws::S3::Model::Type::CanonicalUser:
            return "Canonical user ID of an AWS account";
        case Aws::S3::Model::Type::Group:
            return "Predefined Amazon S3 group";
        case Aws::S3::Model::Type::NOT_SET:
            return "Not set";
        default:
            return "Type unknown";
    }
}

//! Routine which converts a built-in type enumeration to a human-readable string.
/*!
 \sa GetPermissionString()
 \param permission Permission enumeration.
*/

Aws::String GetPermissionString(const Aws::S3::Model::Permission &permission) {
    switch (permission) {
        case Aws::S3::Model::Permission::FULL_CONTROL:
            return "Can list objects in this bucket, create/overwrite/delete "
                   "objects in this bucket, and read/write this "
                   "bucket's permissions";
        case Aws::S3::Model::Permission::NOT_SET:
            return "Permission not set";
        case Aws::S3::Model::Permission::READ:
            return "Can list objects in this bucket";
        case Aws::S3::Model::Permission::READ_ACP:
            return "Can read this bucket's permissions";
        case Aws::S3::Model::Permission::WRITE:
            return "Can create, overwrite, and delete objects in this bucket";
        case Aws::S3::Model::Permission::WRITE_ACP:
            return "Can write this bucket's permissions";
        default:
            return "Permission unknown";
    }

    return "Permission unknown";
}

The following command retrieves the access control list for a bucket named my-bucket:

aws s3api get-bucket-acl --bucket my-bucket

Output:

{
    "Owner": {
        "DisplayName": "my-username",
        "ID": "7009a8971cd538e11f6b6606438875e7c86c5b672f46db45460ddcd087d36c32"
    },
    "Grants": [
        {
            "Grantee": {
                "DisplayName": "my-username",
                "ID": "7009a8971cd538e11f6b6606438875e7c86c5b672f46db45460ddcd087d36c32"
            },
            "Permission": "FULL_CONTROL"
        }
    ]
}

import software.amazon.awssdk.services.s3.model.S3Exception;
import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.s3.S3Client;
import software.amazon.awssdk.services.s3.model.GetObjectAclRequest;
import software.amazon.awssdk.services.s3.model.GetObjectAclResponse;
import software.amazon.awssdk.services.s3.model.Grant;
import java.util.List;

/**
 * Before running this Java V2 code example, set up your development
 * environment, including your credentials.
 *
 * For more information, see the following documentation topic:
 *
 * https://docs.aws.amazon.com/sdk-for-java/latest/developer-guide/get-started.html
 */

public class GetAcl {
    public static void main(String[] args) {
        final String usage = """

                Usage:
                  <bucketName> <objectKey>

                Where:
                  bucketName - The Amazon S3 bucket to get the access control list (ACL) for.
                  objectKey - The object to get the ACL for.\s
                """;

        if (args.length != 2) {
            System.out.println(usage);
            System.exit(1);
        }

        String bucketName = args[0];
        String objectKey = args[1];
        System.out.println("Retrieving ACL for object: " + objectKey);
        System.out.println("in bucket: " + bucketName);
        Region region = Region.US_EAST_1;
        S3Client s3 = S3Client.builder()
                .region(region)
                .build();

        getBucketACL(s3, objectKey, bucketName);
        s3.close();
        System.out.println("Done!");
    }

    public static String getBucketACL(S3Client s3, String objectKey, String bucketName) {
        try {
            GetObjectAclRequest aclReq = GetObjectAclRequest.builder()
                    .bucket(bucketName)
                    .key(objectKey)
                    .build();

            GetObjectAclResponse aclRes = s3.getObjectAcl(aclReq);
            List<Grant> grants = aclRes.grants();
            String grantee = "";
            for (Grant grant : grants) {
                System.out.format("  %s: %s\n", grant.grantee().id(), grant.permission());
                grantee = grant.grantee().id();
            }

            return grantee;
        } catch (S3Exception e) {
            System.err.println(e.awsErrorDetails().errorMessage());
            System.exit(1);
        }

        return "";
    }
}

Get the ACL permissions.

import { GetBucketAclCommand, S3Client } from "@aws-sdk/client-s3";

const client = new S3Client({});

export const main = async () => {
  const command = new GetBucketAclCommand({
    Bucket: "test-bucket",
  });

  try {
    const response = await client.send(command);
    console.log(response);
  } catch (err) {
    console.error(err);
  }
};

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_acl(self):
        """
        Get the ACL of the bucket.

        :return: The ACL of the bucket.
        """
        try:
            acl = self.bucket.Acl()
            logger.info(
                "Got ACL for bucket %s. Owner is %s.", self.bucket.name, acl.owner
            )
        except ClientError:
            logger.exception("Couldn't get ACL for bucket %s.", self.bucket.name)
            raise
        else:
            return acl