[get] How to format a URL to get a file from Amazon S3?

Perhaps not what the OP was after, but for those searching the URL to simply access a readable object on S3 is more like:

https://<region>.amazonaws.com/<bucket-name>/<key>

Where <region> is something like s3-ap-southeast-2.

Click on the item in the S3 GUI to get the link for your bucket.