Unicode C++

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. Unicode C++

#include <CkRestW.h>
#include <CkAuthAwsW.h>

void ChilkatSample(void)
    {
    bool success = false;

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

    CkRestW 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.
    bool bTls = true;
    int port = 443;
    bool bAutoReconnect = true;
    success = rest.Connect(L"s3-us-west-2.amazonaws.com",port,bTls,bAutoReconnect);

    //  Provide AWS credentials.
    CkAuthAwsW authAws;
    authAws.put_AccessKey(L"AWS_ACCESS_KEY");
    authAws.put_SecretKey(L"AWS_SECRET_KEY");
    authAws.put_ServiceName(L"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.put_Region(L"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.put_Host(L"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(L"HEAD",L"/starfish.jpg");
    if (success != true) {
        wprintf(L"%s\n",rest.lastErrorText());
        return;
    }

    //  Now get the response header.
    int statusCode = rest.ReadResponseHeader();
    if (statusCode < 0) {
        wprintf(L"%s\n",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.
        wprintf(L"response status code = %d\n",statusCode);
        wprintf(L"response status text = %s\n",rest.responseStatusText());
        wprintf(L"response header: %s\n",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:
    const wchar_t *etag = rest.responseHdrByName(L"ETag");
    wprintf(L"ETag: %s\n",etag);
    }