Listing Keys Hierarchically Using a Prefix and Delimiter
The prefix and delimiter parameters limit the kind of results returned by a list operation. Prefix limits results to only those keys that begin with the specified prefix, and delimiter causes list to roll up all keys that share a common prefix into a single summary list result.
The purpose of the prefix and delimiter parameters is to help you organize and then browse your keys hierarchically. To do this, first pick a delimiter for your bucket, such as slash (/), that doesn't occur in any of your anticipated key names. Next, construct your key names by concatenating all containing levels of the hierarchy, separating each level with the delimiter.
For example, if you were storing information about cities, you might naturally organize them by continent, then by country, then by province or state. Because these names don't usually contain punctuation, you might select slash (/) as the delimiter. The following examples use a slash (/) delimiter.
If you stored data for every city in the world in this manner, it would become awkward
to manage a flat key namespace. By using
Delimiter with the list operation, you can use the hierarchy you've
created to list your data. For example, to list all the states in USA, set
America/USA/'. To list all the provinces in Canada for which you have data, set
A list request with a delimiter lets you browse your hierarchy at just one level,
skipping over and summarizing the (possibly millions of) keys nested at deeper levels. For
example, assume you have a bucket (
ExampleBucket) the following keys.
The sample bucket has only the
sample.jpg object at the root level. To list
only the root level objects in the bucket you send a GET request on the bucket with "/"
delimiter character. In response, Amazon S3 returns the
sample.jpg object key
because it does not contain the "/" delimiter character. All other keys contain the
delimiter character. Amazon S3 groups these keys and return a single
element with prefix value
photos/ that is a substring from the beginning of
these keys to the first occurrence of the specified delimiter.
<ListBucketResult xmlns="http://s3.amazonaws.com/doc/2006-03-01/"> <Name>ExampleBucket</Name> <Prefix></Prefix> <Marker></Marker> <MaxKeys>1000</MaxKeys> <Delimiter>/</Delimiter> <IsTruncated>false</IsTruncated> <Contents> <Key>sample.jpg</Key> <LastModified>2011-07-24T19:39:30.000Z</LastModified> <ETag>"d1a7fb5eab1c16cb4f7cf341cf188c3d"</ETag> <Size>6</Size> <Owner> <ID>75cc57f09aa0c8caeab4f8c24e99d10f8e7faeebf76c078efc7c6caea54ba06a</ID> <DisplayName>displayname</DisplayName> </Owner> <StorageClass>STANDARD</StorageClass> </Contents> <CommonPrefixes> <Prefix>photos/</Prefix> </CommonPrefixes> </ListBucketResult>