Check if folder exist in s3 bucket

问题

How can I check if some folder exists in my s3 bucket using Ruby on Rails?

I’m using AWS:S3 official gem After initializing the global connection

AWS::S3::Base.establish_connection!(:access_key_id => 'my_key_id', :secret_access_key => ‘my_secret’) 

I have bucket named: myfirstbucket

With folder inside named: my_folder

With file inside my_folder named: my_pic.jpg

When I try to check if my_pic.jpg exist it work just fine

s3object.exists? “/my_folder/my_pic.jpg” , “myfirstbucket”
=>  True

How can I check only if the folder exists?

s3object = AWS::S3::S3Object
s3object.exists? “/my_folder/” , “myfirstbucket”
=>  False

回答1:

Use Bucket#objects:

bucket.objects({prefix: 'my/folder/'}).limit(1).any?

Returns a Collection of ObjectSummary resources. No API requests are made until you call an enumerable method on the collection. Client#list_objects will be called multiple times until every ObjectSummary has been yielded.

—http://docs.aws.amazon.com/sdkforruby/api/Aws/S3/Bucket.html#objects-instance_method

回答2:

You have to check

1. object key with trailing slash "/" is exists
2. If not exists, Is there any item in the directory?

For example: You have file "my_file" under folder "my_folder". The AWS S3 record my_folder/my_file will exist offcourse, but my_folder/ may not exists.

So you have to check twice

if bucket.object("my_folder/").exists?
  true
else
  bucket.objects({prefix: "my_folder/"}).limit(1).any?
end

See the document: http://docs.aws.amazon.com/AmazonS3/latest/UG/FolderOperations.html

回答3:

You could make a tree from you bucket.

http://docs.aws.amazon.com/AWSRubySDK/latest/AWS/S3/Tree.html

tree = bucket.as_tree
tree.children.select(&:branch?).collect(&:prefix).include?(“/my_folder/”)

来源：https://stackoverflow.com/questions/38285326/check-if-folder-exist-in-s3-bucket