(Visual FoxPro) S3 Get Object Metadata, such as ETag

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

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

LOCAL loRest
LOCAL lnBTls
LOCAL lnPort
LOCAL lnBAutoReconnect
LOCAL lnSuccess
LOCAL loAuthAws
LOCAL lnStatusCode
LOCAL lcEtag

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

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Rest')
loRest = CreateObject('Chilkat.Rest')

* Connect to the Amazon AWS REST server in the desired region.
* In this case we connect to S3 in the "us-west-2" region.
lnBTls = 1
lnPort = 443
lnBAutoReconnect = 1
lnSuccess = loRest.Connect("s3-us-west-2.amazonaws.com",lnPort,lnBTls,lnBAutoReconnect)

* Provide AWS credentials.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.AuthAws')
loAuthAws = CreateObject('Chilkat.AuthAws')
loAuthAws.AccessKey = "AWS_ACCESS_KEY"
loAuthAws.SecretKey = "AWS_SECRET_KEY"
loAuthAws.ServiceName = "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".
loAuthAws.Region = "us-west-2"

lnSuccess = loRest.SetAuthAws(loAuthAws)

* 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"
loRest.Host = "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.
lnSuccess = loRest.SendReqNoBody("HEAD","/starfish.jpg")
IF (lnSuccess <> 1) THEN
    ? loRest.LastErrorText
    RELEASE loRest
    RELEASE loAuthAws
    CANCEL
ENDIF

* Now get the response header.
lnStatusCode = loRest.ReadResponseHeader()
IF (lnStatusCode < 0) THEN
    ? loRest.LastErrorText
    RELEASE loRest
    RELEASE loAuthAws
    CANCEL
ENDIF

* When successful, the S3 Storage service will respond with a 200 response code,
* with an XML body.  
IF (lnStatusCode <> 200) THEN
    * Examine the request/response to see what happened.
    ? "response status code = " + STR(lnStatusCode)
    ? "response status text = " + loRest.ResponseStatusText
    ? "response header: " + loRest.ResponseHeader
    RELEASE loRest
    RELEASE loAuthAws
    CANCEL
ENDIF

* 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:
lcEtag = loRest.ResponseHdrByName("ETag")
? "ETag: " + lcEtag

RELEASE loRest
RELEASE loAuthAws