Does s3cmd or the linode-cli support the ability to save a stream as an object the way the AWS utility's s3 subcommand does?

If you are wondering whether you can stream data into Object Storage without specifying the content length header first this should be possible with the s3cmd utility.

You would need to take a streaming buffer and pipe it to Object Storage via s3cmd. You'd need to make use of multipart uploads to accomplish this.

This should be possible using the --continue-put option.

  --continue-put        Continue uploading partially uploaded files or
                        multipart upload parts.  Restarts/parts files that
                        don't have matching size and md5.  Skips files/parts
                        that do.  Note: md5sum checks are not always
                        sufficient to check (part) file equality.  Enable this
                        at your own risk.

Source: https://s3tools.org/usage

In short, if you are able to accomplish this using s3cmd with AWS, it would - in theory - be compatible on our platform.