How to access AWS "subfolders" using ListObjects() in C++ SDK? - c++

Question

I am trying to list the objects in the "noaa-goes16/GLM-L2-LCFA/2021/140/05" bucket. The AWS C++ SDK says that in order to list the objects, you need to use the following function:
bool 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();
}
After passing the string to the function, I get the following error:
Aws::SDKOptions options;
Aws::InitAPI(options);
Aws::Client::ClientConfiguration clientConfig;
std::string object = "noaa-goes16/GLM-L2-LCFA/2021/140/05";
ListObject(object, clientConfig);
Output:
Error: ListObjects: The specified key does not exist.
noaa-goes16/GLM-L2-LCFA/2021/140/05
I have tried to add a "/" to the bucket name, and it states again that it does not exist.
If I just try "noaa-goes16" as the bucket name, it lists 1000 files that are not relevant to my application. How do I list the files in the "/05" subfolder using the AWS C++ SDK?
I tried to list the files in a subfolder of the noaa-goes16 bucket using the ListObjects() function in the AWS C++ SDK. I recieved an error that the subfolder I asked for does not exist. However, I know that the subfolder I am asking for does exist. I have tried to add a "/" to the end of the bucket, thinking this would resolve the error. This did not help. I have found that if I only put the main bucket object as the name ("noaa-goes16"), it works. However, I cannot list objects in a specific subfolder and would like to know how.

Answer 1

All! I have just figured it out! Hopefully, this thread helps others.
In order to get the subfolder, you need to use a method on the request object.
For example, in order to list all of the objects in the "GLM-L2-LCFA/2021/140/05" subfolder, add the Aws::String &prefix:
bool ListObjects(const Aws::String& bucketName, const Aws::String &prefix,
const Aws::Client::ClientConfiguration& clientConfig) {
Aws::S3::S3Client s3_client(clientConfig);
Aws::S3::Model::ListObjectsRequest request;
request.WithBucket(bucketName).WithPrefix(prefix);
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();
Now, pass the following:
Aws::Client::ClientConfiguration clientConfig;
std::string bucket = "noaa-goes16";
std::string prefix = "GLM-L2-LCFA/2021/140/05";
ListObjects(bucket, prefix, clientConfig);
Viola!