Amazon S3: How to get a list of folders in the bucket?

Question

All that I found, it\'s this method GET Bucket But I can\'t understand how can I get only a list of folders in the current folder. Which prefix and delimiter I need to use?

Answer 1

For the sake of example, assume I have a bucket in the USEast1 region called MyBucketName, with the following keys:

 temp/
 temp/foobar.txt
 temp/txt/
 temp/txt/test1.txt
 temp/txt/test2.txt
 temp2/

Working with folders can be confusing because S3 does not natively support a hierarchy structure -- rather, these are simply keys like any other S3 object. Folders are simply an abstraction available in the S3 web console to make it easier to navigate a bucket. So when we're working programatically, we want to find keys matching the dimensions of a 'folder' (delimiter '/', size = 0) because they will likely be 'folders' as presented to us by the S3 console.

Note for both examples: I'm using the AWSSDK.S3 version 3.1 NuGet package.

Example 1: All folders in a bucket

This code is modified from this basic example in the S3 documentation to list all keys in a bucket. The example below will identify all keys that end with the delimiter character /, and are also empty.

IAmazonS3 client;
using (client = new AmazonS3Client(Amazon.RegionEndpoint.USEast1))
{
    // Build your request to list objects in the bucket
    ListObjectsRequest request = new ListObjectsRequest
    {
        BucketName = "MyBucketName"
    };

    do
    {
        // Build your call out to S3 and store the response
        ListObjectsResponse response = client.ListObjects(request);

        // Filter through the response to find keys that:
        // - end with the delimiter character '/' 
        // - are empty. 
        IEnumerable folders = response.S3Objects.Where(x =>
            x.Key.EndsWith(@"/") && x.Size == 0);

        // Do something with your output keys.  For this example, we write to the console.
        folders.ToList().ForEach(x => System.Console.WriteLine(x.Key));

        // If the response is truncated, we'll make another request 
        // and pull the next batch of keys
        if (response.IsTruncated)
        {
            request.Marker = response.NextMarker;
        }
        else
        {
            request = null;
        }
    } while (request != null);
}

Expected output to console:

temp/
temp/txt/
temp2/

Example 2: Folders matching a specified prefix

You could further limit this to only retrieve folders matching a specified Prefix by setting the Prefix property on ListObjectsRequest.

ListObjectsRequest request = new ListObjectsRequest
    {
        BucketName = "MyBucketName",
        Prefix = "temp/"
    };

When applied to Example 1, we would expect the following output:

temp/
temp/txt/

Further reading:

• S3 Documentation - Working With Folders
• .NET SDK Documentation - ListObjects