(PowerShell) S3 Get Object Metadata, such as ETag

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

Chilkat .NET Downloads Chilkat .NET Assemblies

Add-Type -Path "C:\chilkat\ChilkatDotNet47-9.5.0-x64\ChilkatDotNet47.dll"

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

$rest = New-Object 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.
$bTls = $true
$port = 443
$bAutoReconnect = $true
$success = $rest.Connect("s3-us-west-2.amazonaws.com",$port,$bTls,$bAutoReconnect)

# Provide AWS credentials.
$authAws = New-Object 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 -ne $true) {
    $($rest.LastErrorText)
    exit
}

# Now get the response header.
$statusCode = $rest.ReadResponseHeader()
if ($statusCode -lt 0) {
    $($rest.LastErrorText)
    exit
}

# When successful, the S3 Storage service will respond with a 200 response code,
# with an XML body.  
if ($statusCode -ne 200) {
    # Examine the request/response to see what happened.
    $("response status code = " + $statusCode)
    $("response status text = " + $rest.ResponseStatusText)
    $("response header: " + $rest.ResponseHeader)
    exit
}

# 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")
$("ETag: " + $etag)