Node.js

S3 Get Object Metadata, such as ETag

See more Amazon S3 (new) Examples

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

NODEJS_PRELUDE

function chilkatExample() {

    var success = false;

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

    var rest = new 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.
    var bTls = true;
    var port = 443;
    var bAutoReconnect = true;
    success = rest.Connect("s3-us-west-2.amazonaws.com",port,bTls,bAutoReconnect);

    //  Provide AWS credentials.
    var authAws = new chilkat.AuthAws();
    authAws.AccessKey = "AWS_ACCESS_KEY";
    authAws.SecretKey = "AWS_SECRET_KEY";
    authAws.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".
    authAws.Region = "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.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.
    success = rest.SendReqNoBody("HEAD","/starfish.jpg");
    if (success !== true) {
        console.log(rest.LastErrorText);
        return;
    }

    //  Now get the response header.
    var statusCode = rest.ReadResponseHeader();
    if (statusCode < 0) {
        console.log(rest.LastErrorText);
        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.
        console.log("response status code = " + statusCode);
        console.log("response status text = " + rest.ResponseStatusText);
        console.log("response header: " + rest.ResponseHeader);
        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:
    var etag = rest.ResponseHdrByName("ETag");
    console.log("ETag: " + etag);

}

chilkatExample();