Size of s3 bucket.

s3size.go

// Get the size of a public s3 bucket.
//
// Relies on the directory listing being public.
//
// Example usage:
//              s3size -bucket <bucketName>
//
package main
import (
        "encoding/xml"
        "flag"
        "fmt"
        "log"
        "net/http"
        "net/url"
)
type Content struct {
        Key    string
        Md5Sum string `xml:"ETag"`
        Size   int64
}
type Result struct {
        Contents    []Content
        IsTruncated bool
}
func main() {
        var bucketName string
        flag.StringVar(&bucketName, "bucket", "", "bucket to download")
        flag.Parse()
        bucketUrl := url.URL{Scheme: "https", Host: bucketName + ".s3.amazonaws.com"}
        // Request for list of files
        // (Possibly requiring multiple requests if bucket has lots of items)
        var result Result
        for {
                reqUrl := bucketUrl
                // If we already recieved a response,
                // continue from the end of list already received.
                if len(result.Contents) > 0 {
                        reqValues := reqUrl.Query()
                        reqValues.Set("marker", result.Contents[len(result.Contents)-1].Key)
                        reqUrl.RawQuery = reqValues.Encode()
                }
                res, err := http.Get(reqUrl.String())
                if err != nil {
                        log.Fatal(err)
                }
                
                xmlDecode := xml.NewDecoder(res.Body)
                xmlDecode.Decode(&result)
                res.Body.Close()
                // Received last of the list
                if !result.IsTruncated {
                        break
                }
        }
        var sum int64
        for _, content := range result.Contents {
                sum += content.Size
        }
        fmt.Println(sum)
}