List root directory using ListBlobsByHierarchy using azure sdk

Question

I'm trying to list root directory in container.

Storage account: Data Lake Storage with hierarchical namespace ON

Interface used: BlobContainerClient

Folder structure
ROOT DIR:
dir1->blob2
blob1

    auto listBlobOptions = Azure::Storage::Blobs::ListBlobsOptions();
    auto blobPages = containerClient.ListBlobsByHierarchy("/", listBlobOptions);

    std::cout << "Blob Reading" << std::endl;
    for (const auto& blobItem : blobPages.Blobs)
    {
        std::cout << "******************" << std::endl;
        std::cout << blobItem.Name << std::endl;
    }

If I use "/" as delimiter, the directories that were created from Azure portal are not included. If I remove it, that all the blobs are being listed.

With "/" I would get only blob1, but without I would get

dir1,
blob1
dir1/blob2

Reason for Storage account and interface mismatch is because we are using private endpoints with subresource type BLOB, and DFS is forbidden in such case.

If I would use ListBlobs or not use "/" that would read all the blobs in the storage accounts, which is kind of problematic since there could be huge amount of it.

You need to list only root directory folders with files? you can see here sample image i.imgur.com/CFyK7Tp.png in this image you need list only folder1 only with files?. — Venkatesan
– Venkatesan, Commented Feb 19 at 10:50
So I would expect like this. If I pass "" for prefix, and "/" for delimiter, to get exactly same list as picture show. I do not care what is inside of folder1 and folder2. — John Doe
– John Doe, Commented Feb 19 at 10:58
Are you expecting like this i.imgur.com/I2M5i99.png from my above picture? — Venkatesan
– Venkatesan, Commented Feb 19 at 10:59

Venkatesan · Accepted Answer · 2025-02-19 11:13:56Z

1

List root directory using ListBlobsByHierarchy using azure sdk

You can use the below code that will list the root folder with files using Azure C++ SDK.

Code:

#include <iostream>
#include <azure/storage/blobs.hpp>

using namespace Azure::Storage::Blobs;

int main() {
    // Define your storage account connection string and container name
    std::string connectionString = "xxxxxx";
    std::string containerName = "xxx";

    // Create a BlobContainerClient
    BlobContainerClient containerClient = BlobContainerClient::CreateFromConnectionString(connectionString, containerName);
    ListBlobsOptions listBlobOptions;

    // Use "/" as the delimiter to list only the root contents
    auto blobPages = containerClient.ListBlobsByHierarchy("/", listBlobOptions);

    std::cout << "Listing contents of root directory in container: " << containerName << std::endl;

    // List directories (BlobPrefixes)
    for (const auto& prefix : blobPages.BlobPrefixes) {
        std::cout << "[Directory] " << prefix << std::endl;  // FIX: Use prefix as a string
    }

    // List files (Blobs)
    for (const auto& blobItem : blobPages.Blobs) {
        std::cout << "[File] " << blobItem.Name << std::endl;  // BlobItem is an object with .Name
    }

    return 0;
}

The above code lists files and directories at the root level using ListBlobsByHierarchy("/"), and prints them. Directories are retrieved from BlobPrefixes, while files are listed from Blobs.

Output:

Listing contents of root directory in container: sample
[Directory] folder1/
[Directory] folder2/
[File] 001.csv
[File] 002.csv
[File] 003.csv
[File] demo.csv

enter image description here

answered Feb 19 at 11:13

Venkatesan

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2 Comments

John Doe Feb 19 at 11:41

Aaaaa that makes sense. There is no such thing as folder when you are using BlobService interface, so they have to be picked up as prefixes. And now if I would like to go deeper, I would have to pass prefix to the options, and then to do like folderName= BlobPrefixesPrefix- prefix

Venkatesan Feb 19 at 11:49

Then you need to set Prefix = "folderName/" in ListBlobsOptions and call the ListBlobsByHierarchy("/", listBlobOptions) and Repeat for deeper levels.

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