Use CLI s3api to Retrieve Metadata of Amazon S3 Object

In Amazon S3 CLI, there are only a handful commands:

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cp      ls      mb      mv      rb      rm      sync    website

We can use cp command to retrieve S3 object:

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$ aws s3 cp s3://mybucket/myfile.json myfile.json

But if only the metadata of the object, such as ETag or Content-Type is needed, the S3 CLI does not have any command to do that.

Now enter S3API CLI. Not only the CLI commands can retrieve S3 objects, but also associated metadata. For example, retrieve S3 object similar to aws s3 cp:

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$ aws s3api get-object --bucket mybucket --key myfile.json

Just need the metadata of the object, use head-object, which retrieves metadata without the object itself, as HTTP HEAD method:

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$ aws s3api head-object --bucket mybucket --key myfile.json
{
  "AcceptRanges": "bytes", 
  "ContentType": "application/json", 
  "LastModified": "Wed, 07 Jan 2015 12:00:00 GMT", 
  "ContentLength": 2015, 
  "ETag": "\"63aa0f9df87f6b54f150cf8a1011d2b0\"", 
  "Metadata": {}
}