(Go) S3 Get Object Metadata, such as ETag

Demonstrates how to get an S3 object's metadata using a HEAD request.

Chilkat Go Downloads Go Package for Windows, MacOS, Linux, Alpine Linux, Solaris

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    rest := chilkat.NewRest()

    // Connect to the Amazon AWS REST server in the desired region.
    // In this case we connect to S3 in the "us-west-2" region.
    bTls := true
    port := 443
    bAutoReconnect := true
    success := rest.Connect("s3-us-west-2.amazonaws.com",port,bTls,bAutoReconnect)

    // Provide AWS credentials.
    authAws := chilkat.NewAuthAws()
    authAws.SetAccessKey("AWS_ACCESS_KEY")
    authAws.SetSecretKey("AWS_SECRET_KEY")
    authAws.SetServiceName("s3")

    // This particular bucket is in the Oregon region, as opposed to the US Standard,
    // therefore the Region must be set appropriately.
    // Also note that we connected to "s3-us-west-2.amazonaws.com".
    authAws.SetRegion("us-west-2")

    success = rest.SetAuthAws(authAws)

    // Note: The above REST connection and setup of the AWS credentials
    // can be done once.  After connecting, any number of REST calls can be made.
    // The "auto reconnect" property passed to rest.Connect indicates that if
    // the connection is lost, a REST method call will automatically reconnect
    // if needed.
    // --------------------------------------------------------------------------

    // Set the bucket name via the HOST header.
    // In this case, the bucket name is "chilkat.ocean".
    // Note that the Host header should use "bucketName.s3.amazonaws.com", not "bucketName.s3-us-west-2.amazonaws.com"
    rest.SetHost("chilkat.ocean.s3.amazonaws.com")

    // Our object is "starfish.jpg".
    // Get the metadata.
    // Since we are sending a HEAD request, we shouldn't use any of the Full* methods.
    // Instead, send the request, then just read the response header.
    success = rest.SendReqNoBody("HEAD","/starfish.jpg")
    if success != true {
        fmt.Println(rest.LastErrorText())
        rest.DisposeRest()
        authAws.DisposeAuthAws()
        return
    }

    // Now get the response header.
    statusCode := rest.ReadResponseHeader()
    if statusCode < 0 {
        fmt.Println(rest.LastErrorText())
        rest.DisposeRest()
        authAws.DisposeAuthAws()
        return
    }

    // When successful, the S3 Storage service will respond with a 200 response code,
    // with an XML body.  
    if statusCode != 200 {
        // Examine the request/response to see what happened.
        fmt.Println("response status code = ", statusCode)
        fmt.Println("response status text = ", rest.ResponseStatusText())
        fmt.Println("response header: ", rest.ResponseHeader())
        rest.DisposeRest()
        authAws.DisposeAuthAws()
        return
    }

    // The response header contains information about the S3 object.
    // For example:

    // 	HTTP/1.1 200 OK
    // 	x-amz-id-2: GrV/hrB2EUkBlWc0h3JDdmVIrYDXfPC7CGvo/qSVRmYRPwilAOry8+4r2YWl4xJfa1HRYXrP808=
    // 	x-amz-request-id: 4BDC6D6AEA0BDEF3
    // 	Date: Mon, 13 May 2019 22:03:13 GMT
    // 	Last-Modified: Mon, 10 Nov 2014 16:10:23 GMT
    // 	ETag: "2e9c59dbf2662367dc97dfdda85da048"
    // 	Accept-Ranges: bytes
    // 	Content-Type: image/jpg
    // 	Content-Length: 6229
    // 	Server: AmazonS3

    // Get the ETag response header value:
    etag := rest.ResponseHdrByName("ETag")
    fmt.Println("ETag: ", *etag)

    rest.DisposeRest()
    authAws.DisposeAuthAws()