How to backup a s3 bucket to the glacier

The AWS CLI now supports the --query parameter which takes a JMESPath expressions.

This means you can sum the size values given by list-objects using sum(Contents[].Size) and count like length(Contents[]).

This can be be run using the official AWS CLI as below and was introduced in Feb 2014

 aws s3api list-objects --bucket BUCKETNAME --output json --query "[sum(Contents[].Size), length(Contents[])]"

I see some useful comments are already here but will throw in just one comment: I would frankly go with putting your objects into S3 and then simply create a very short "Transition to Glacier" policy, like a few hours or 1 day old. You can access Glacier directly through the API, but the reason I would go this route is that you will still see your objects listed within S3, but you'll see in the "Storage Class" column that after a few days everything will have been moved into Glacier. Then, when/if you need to retrieve something out of Glacier, you can make the retrieval request (called "initiate restore" in the new ACTIONS menu of S3's web GUI) it's all right there for you to see and work with.

I'm a huge fan of the CLI for much of my AWS work, but I think until there's a really robust and usable CLI tool for Glacier, this seems easier to work with.