List all buckets
s3cmd la
List files within one bucket
s3cmd ls s3://com.example.int.backup/
Download a file
s3cmd get s3://BUCKET/OBJECT LOCAL_FILE
Upload a file
s3cmd put FILE [FILE...] s3://BUCKET[/PREFIX]
Delete a file
s3cmd del s3://com.example.int.backup/git_bitbucket_saved.tar.gz