Listing object keys programmatically
In Amazon S3, keys can be listed by prefix. You can choose a common prefix for the names of
related keys and mark these keys with a special character that delimits hierarchy. You can
then use the list operation to select and browse keys hierarchically. This is similar to how
files are stored in directories within a file system.
Amazon S3 exposes a list operation that lets you enumerate the keys contained in a bucket. Keys
are selected for listing by bucket and prefix. For example, consider a bucket named
"dictionary" that contains a key for every English word. You might make a
call to list all the keys in that bucket that start with the letter "q". List results are
always returned in UTF-8 binary order.
Both the SOAP and REST list operations return an XML document that contains the names of
matching keys and information about the object identified by each key.
SOAP support over HTTP is deprecated, but SOAP is still available over HTTPS.
New Amazon S3 features are not supported for SOAP. Instead of using SOAP, we recommend that you use
either the REST API or the AWS SDKs.
Groups of keys that share a prefix terminated by a special delimiter can be rolled up by
that common prefix for the purposes of listing. This enables applications to organize and
browse their keys hierarchically, much like how you would organize your files into
directories in a file system.
For example, to extend the dictionary bucket to contain more than just English words, you
might form keys by prefixing each word with its language and a delimiter, such as
"French/logical". Using this naming scheme and the hierarchical listing
feature, you could retrieve a list of only French words. You could also browse the top-level
list of available languages without having to iterate through all the lexicographically
intervening keys. For more information about this aspect of listing, see Organizing objects using prefixes.
REST API
If your application requires it, you can send REST requests directly. You can send a
GET request to return some or all of the objects in a bucket or you can use selection
criteria to return a subset of the objects in a bucket. For more information, see GET Bucket (List Objects) Version 2
in the Amazon Simple Storage Service API Reference.
List implementation efficiency
List performance is not substantially affected by the total number of keys in your
bucket. It's also not affected by the presence or absence of the prefix,
marker, maxkeys, or delimiter arguments.
Iterating through multipage results
As buckets can contain a virtually unlimited number of keys, the complete results of a
list query can be extremely large. To manage large result sets, the Amazon S3 API supports
pagination to split them into multiple responses. Each list keys response returns a page
of up to 1,000 keys with an indicator indicating if the response is truncated. You send
a series of list keys requests until you have received all the keys. AWS SDK wrapper
libraries provide the same pagination.
Examples
The following code examples show how to list objects in an S3 bucket.
- .NET
-
- AWS SDK for .NET
-
/// <summary>
/// Shows how to list the objects in an Amazon S3 bucket.
/// </summary>
/// <param name="client">An initialized Amazon S3 client object.</param>
/// <param name="bucketName">The name of the bucket for which to list
/// the contents.</param>
/// <returns>A boolean value indicating the success or failure of the
/// copy operation.</returns>
public static async Task<bool> ListBucketContentsAsync(IAmazonS3 client, string bucketName)
{
try
{
var request = new ListObjectsV2Request
{
BucketName = bucketName,
MaxKeys = 5,
};
Console.WriteLine("--------------------------------------");
Console.WriteLine($"Listing the contents of {bucketName}:");
Console.WriteLine("--------------------------------------");
ListObjectsV2Response response;
do
{
response = await client.ListObjectsV2Async(request);
response.S3Objects
.ForEach(obj => Console.WriteLine($"{obj.Key,-35}{obj.LastModified.ToShortDateString(),10}{obj.Size,10}"));
// If the response is truncated, set the request ContinuationToken
// from the NextContinuationToken property of the response.
request.ContinuationToken = response.NextContinuationToken;
}
while (response.IsTruncated);
return true;
}
catch (AmazonS3Exception ex)
{
Console.WriteLine($"Error encountered on server. Message:'{ex.Message}' getting list of objects.");
return false;
}
}
List objects with a paginator.
using System;
using System.Threading.Tasks;
using Amazon.S3;
using Amazon.S3.Model;
/// <summary>
/// The following example lists objects in an Amazon Simple Storage
/// Service (Amazon S3) bucket. It was created using AWS SDK for .NET 3.5
/// and .NET Core 5.0.
/// </summary>
public class ListObjectsPaginator
{
private const string BucketName = "doc-example-bucket";
public static async Task Main()
{
IAmazonS3 s3Client = new AmazonS3Client();
Console.WriteLine($"Listing the objects contained in {BucketName}:\n");
await ListingObjectsAsync(s3Client, BucketName);
}
/// <summary>
/// This method uses a paginator to retrieve the list of objects in an
/// an Amazon S3 bucket.
/// </summary>
/// <param name="client">An Amazon S3 client object.</param>
/// <param name="bucketName">The name of the S3 bucket whose objects
/// you want to list.</param>
public static async Task ListingObjectsAsync(IAmazonS3 client, string bucketName)
{
var listObjectsV2Paginator = client.Paginators.ListObjectsV2(new ListObjectsV2Request
{
BucketName = bucketName,
});
await foreach (var response in listObjectsV2Paginator.Responses)
{
Console.WriteLine($"HttpStatusCode: {response.HttpStatusCode}");
Console.WriteLine($"Number of Keys: {response.KeyCount}");
foreach (var entry in response.S3Objects)
{
Console.WriteLine($"Key = {entry.Key} Size = {entry.Size}");
}
}
}
}
- C++
-
- SDK for C++
-
bool AwsDoc::S3::ListObjects(const Aws::String &bucketName,
const Aws::Client::ClientConfiguration &clientConfig) {
Aws::S3::S3Client s3_client(clientConfig);
Aws::S3::Model::ListObjectsRequest request;
request.WithBucket(bucketName);
auto outcome = s3_client.ListObjects(request);
if (!outcome.IsSuccess()) {
std::cerr << "Error: ListObjects: " <<
outcome.GetError().GetMessage() << std::endl;
}
else {
Aws::Vector<Aws::S3::Model::Object> objects =
outcome.GetResult().GetContents();
for (Aws::S3::Model::Object &object: objects) {
std::cout << object.GetKey() << std::endl;
}
}
return outcome.IsSuccess();
}
- Go
-
- SDK for Go V2
-
// BucketBasics encapsulates the Amazon Simple Storage Service (Amazon S3) actions
// used in the examples.
// It contains S3Client, an Amazon S3 service client that is used to perform bucket
// and object actions.
type BucketBasics struct {
S3Client *s3.Client
}
// ListObjects lists the objects in a bucket.
func (basics BucketBasics) ListObjects(bucketName string) ([]types.Object, error) {
result, err := basics.S3Client.ListObjectsV2(context.TODO(), &s3.ListObjectsV2Input{
Bucket: aws.String(bucketName),
})
var contents []types.Object
if err != nil {
log.Printf("Couldn't list objects in bucket %v. Here's why: %v\n", bucketName, err)
} else {
contents = result.Contents
}
return contents, err
}
- Java
-
- SDK for Java 2.x
-
public static void listBucketObjects(S3Client s3, String bucketName ) {
try {
ListObjectsRequest listObjects = ListObjectsRequest
.builder()
.bucket(bucketName)
.build();
ListObjectsResponse res = s3.listObjects(listObjects);
List<S3Object> objects = res.contents();
for (S3Object myValue : objects) {
System.out.print("\n The name of the key is " + myValue.key());
System.out.print("\n The object is " + calKb(myValue.size()) + " KBs");
System.out.print("\n The owner is " + myValue.owner());
}
} catch (S3Exception e) {
System.err.println(e.awsErrorDetails().errorMessage());
System.exit(1);
}
}
//convert bytes to kbs.
private static long calKb(Long val) {
return val/1024;
}
- JavaScript
-
- SDK for JavaScript V3
-
Create the client.
// Create service client module using ES6 syntax.
import { S3Client } from "@aws-sdk/client-s3";
// Set the AWS Region.
const REGION = "us-east-1";
// Create an Amazon S3 service client object.
const s3Client = new S3Client({ region: REGION });
export { s3Client };
List the objects.
// Import required AWS SDK clients and commands for Node.js.
import { ListObjectsCommand } from "@aws-sdk/client-s3";
import { s3Client } from "./libs/s3Client.js"; // Helper function that creates an Amazon S3 service client module.
// Create the parameters for the bucket
export const bucketParams = { Bucket: "BUCKET_NAME" };
export const run = async () => {
try {
const data = await s3Client.send(new ListObjectsCommand(bucketParams));
console.log("Success", data);
return data; // For unit tests.
} catch (err) {
console.log("Error", err);
}
};
run();
List 1000 or more objects.
// Import required AWS SDK clients and commands for Node.js.
import { ListObjectsCommand } from "@aws-sdk/client-s3";
import { s3Client } from "./libs/s3Client.js"; // Helper function that creates an Amazon S3 service client module.
// Create the parameters for the bucket
export const bucketParams = { Bucket: "BUCKET_NAME" };
export async function run() {
// Declare truncated as a flag that the while loop is based on.
let truncated = true;
// Declare a variable to which the key of the last element is assigned to in the response.
let pageMarker;
// while loop that runs until 'response.truncated' is false.
while (truncated) {
try {
const response = await s3Client.send(new ListObjectsCommand(bucketParams));
// return response; //For unit tests
response.Contents.forEach((item) => {
console.log(item.Key);
});
// Log the key of every item in the response to standard output.
truncated = response.IsTruncated;
// If truncated is true, assign the key of the last element in the response to the pageMarker variable.
if (truncated) {
pageMarker = response.Contents.slice(-1)[0].Key;
// Assign the pageMarker value to bucketParams so that the next iteration starts from the new pageMarker.
bucketParams.Marker = pageMarker;
}
// At end of the list, response.truncated is false, and the function exits the while loop.
} catch (err) {
console.log("Error", err);
truncated = false;
}
}
}
run();
- Kotlin
-
- SDK for Kotlin
-
This is prerelease documentation for a feature in preview release. It is subject to change.
suspend fun listBucketObjects(bucketName: String) {
val request = ListObjectsRequest {
bucket = bucketName
}
S3Client { region = "us-east-1" }.use { s3 ->
val response = s3.listObjects(request)
response.contents?.forEach { myObject ->
println("The name of the key is ${myObject.key}")
println("The object is ${calKb(myObject.size)} KBs")
println("The owner is ${myObject.owner}")
}
}
}
private fun calKb(intValue: Long): Long {
return intValue / 1024
}
- PHP
-
- SDK for PHP
-
List objects in a bucket.
$s3client = new Aws\S3\S3Client(['region' => 'us-west-2', 'version' => 'latest']);
try {
$contents = $s3client->listObjects([
'Bucket' => $bucket_name,
]);
echo "The contents of your bucket are: \n";
foreach ($contents['Contents'] as $content) {
echo $content['Key'] . "\n";
}
} catch (Exception $exception) {
echo "Failed to list objects in $bucket_name with error: " . $exception->getMessage();
exit("Please fix error with listing objects before continuing.");
}
- Python
-
- SDK for Python (Boto3)
-
class ObjectWrapper:
"""Encapsulates S3 object actions."""
def __init__(self, s3_object):
"""
:param s3_object: A Boto3 Object resource. This is a high-level resource in Boto3
that wraps object actions in a class-like structure.
"""
self.object = s3_object
self.key = self.object.key
@staticmethod
def list(bucket, prefix=None):
"""
Lists the objects in a bucket, optionally filtered by a prefix.
:param bucket: The bucket to query. This is a Boto3 Bucket resource.
:param prefix: When specified, only objects that start with this prefix are listed.
:return: The list of objects.
"""
try:
if not prefix:
objects = list(bucket.objects.all())
else:
objects = list(bucket.objects.filter(Prefix=prefix))
logger.info("Got objects %s from bucket '%s'",
[o.key for o in objects], bucket.name)
except ClientError:
logger.exception("Couldn't get objects for bucket '%s'.", bucket.name)
raise
else:
return objects
- Ruby
-
- SDK for Ruby
-
require "aws-sdk-s3"
# Wraps Amazon S3 bucket actions.
class BucketListObjectsWrapper
attr_reader :bucket
# @param bucket [Aws::S3::Bucket] An existing Amazon S3 bucket.
def initialize(bucket)
@bucket = bucket
end
# Lists object in a bucket.
#
# @param max_objects [Integer] The maximum number of objects to list.
# @return [Integer] The number of objects listed.
def list_objects(max_objects)
count = 0
puts "The objects in #{@bucket.name} are:"
@bucket.objects.each do |obj|
puts "\t#{obj.key}"
count += 1
break if count == max_objects
end
count
rescue Aws::Errors::ServiceError => e
puts "Couldn't list objects in bucket #{bucket.name}. Here's why: #{e.message}"
0
end
end
def run_demo
bucket_name = "doc-example-bucket"
wrapper = BucketListObjectsWrapper.new(Aws::S3::Bucket.new(bucket_name))
count = wrapper.list_objects(25)
puts "Listed #{count} objects."
end
run_demo if $PROGRAM_NAME == __FILE__
- Rust
-
- SDK for Rust
-
This documentation is for an SDK in preview release. The SDK is subject to change and should not be used in production.
pub async fn list_objects(client: &Client, bucket_name: &str) -> Result<(), Error> {
let objects = client.list_objects_v2().bucket(bucket_name).send().await?;
println!("Objects in bucket:");
for obj in objects.contents().unwrap_or_default() {
println!("{:?}", obj.key().unwrap());
}
Ok(())
}
- SAP ABAP
-
- SDK for SAP ABAP
-
This documentation is for an SDK in developer preview release. The SDK is subject to change and is not recommended for use in production.
TRY.
oo_result = lo_s3->listobjects( " oo_result is returned for testing purpose "
iv_bucket = iv_bucket_name
).
MESSAGE 'Retrieved list of object(s) in S3 bucket' TYPE 'I'.
CATCH /aws1/cx_s3_nosuchbucket.
MESSAGE 'Bucket does not exist' TYPE 'E'.
ENDTRY.
- Swift
-
- SDK for Swift
-
This is prerelease documentation for an SDK in preview release. It is subject to change.
public func listBucketFiles(bucket: String) async throws -> [String] {
let input = ListObjectsV2Input(
bucket: bucket
)
let output = try await client.listObjectsV2(input: input)
var names: [String] = []
guard let objList = output.contents else {
return []
}
for obj in objList {
if let objName = obj.key {
names.append(objName)
}
}
return names
}
