PowerShell for AWS: List only "folders" from S3 bucket?

Is there any easy way to use PowerShell to only get a list of "folders" from an S3 bucket, without listing every single object and just scripting a compiled list of distinct paths? There are hundreds of thousands of individual objects in the bucket I'm working in, and that would take a very long time.

It's possible this is a really stupid question and I'm sorry if that's the case, but I couldn't find anything on Google or SO to answer this. I've tried adding wildcards to -KeyPrefix and -Key params of Get-S3Object to no avail. That's the only cmdlet that seems like it might be capable of doing what I'm after.

Pointless backstory: I just want to make sure I'm transferring files to the correct, existing folders. I'm a contracted third party, so I don't have console login access and I'm not the person who maintains the AWS account.

I know this is possible using Java and C# and others, but I'm doing everything else involved with this fairly simple project in PS and was hoping to be able to stick with it.

Thanks in advance.

You can use the AWS Tools For PowerShell to list objects (via Get-S3Object) in the bucket and pull common prefixes from the response object.

Below is a small library to recursively retrieve subdirectories:

function Get-Subdirectories
{
  param
  (
    [string] $BucketName,
    [string] $KeyPrefix,
    [bool] $Recurse
  )

  @(get-s3object -BucketName $BucketName -KeyPrefix $KeyPrefix -Delimiter '/') | Out-Null

  if($AWSHistory.LastCommand.Responses.Last.CommonPrefixes.Count -eq 0)
  {
    return
  }

  $AWSHistory.LastCommand.Responses.Last.CommonPrefixes

  if($Recurse)
  {
    $AWSHistory.LastCommand.Responses.Last.CommonPrefixes | % { Get-Subdirectories -BucketName $BucketName -KeyPrefix $_ -Recurse $Recurse }
  }
}

function Get-S3Directories
{
  param
  (
    [string] $BucketName,
    [bool] $Recurse = $false
  )

  Get-Subdirectories -BucketName $BucketName -KeyPrefix '/' -Recurse $Recurse
}

This recursive function depends on updating the KeyPrefix on each iteration to check for subdirectories in each KeyPrefix passed to it. By setting the delimiter as '/', keys matching the KeyPrefix string before hitting the first occurance of the delimiter are rolled into the CommonPrefixes collection in the last response of $AWSHistory.

To retrieve only the top-level directories in an S3 Bucket:

PS C:/> Get-S3Directories -BucketName 'myBucket'

To retrieve all directories in an S3 Bucket:

PS C:/> Get-S3Directories -BucketName 'myBucket' -Recurse $true

This will return a collection of strings, where each string is a common prefix.

Example Output:

myprefix/
myprefix/txt/
myprefix/img/
myotherprefix/
...