s3presignedUrl()

FileMaker custom function to generate a presigned URL to upload/download/delete an object in S3

s3presignedUrl ( method ; bucket ; region ; theFilePath ; expireSeconds ; accessKey ; secretKey ; optionsObj )

PARAMETERS

• method | GET or PUT or DELETE or HEAD
• bucket | the bucket name
• region | eg: ca-central-1
• theFilePath | the full path to the file in the bucket eg: /folder/filename.pdf
• expireSeconds | the length of time that the URL will be valid
• accessKey | AWS Access Key
• secretKey | AWS Secret Key
• optionsObj | empty or JSON object containing optional parameters

OPTIONAL PARAMETERS

Optional parameters are passed as JSON inside the optionsObj parameter

• host | the provider's domain, not required for AWS. Must include the full hostname including the bucket name if required.
• token | the session token (e.g., from AWS STS), if your role requires you to include one.

USAGE

Generate a presigned URL with the desired method, then...

GET

You can use Insert From URL to download the object to a container or variable (to download a binary object to a variable in FileMaker, you must add the --FM-return-container-variable cURL option). Alternatively, reference the presigned URL in a web viewer (in an src attribute, for example). Note: You may need to change the CORS settings for your bucket in order to load the object into a web viewer.

PUT

Use Insert From URL with the following cURL options:

"-X PUT -H " & Quote ( "Content-Length: " & $fileSizeInBytes ) & " -H " & Quote ( "Content-Type: " & $contentType ) & " --data-binary @$container -D $responseHeaders"

$contentType is the mime type. For example APPLICATION/PDF or IMAGE/PNG. Having the correct content type stored in S3 is necessary to GET the object into a browser or web viewer. For example, without the content-type header IMAGE/PNG, a PNG file would simply by downloaded rather than displayed.

If the upload was successful, PatternCount ( $responseHeaders ; "200 OK" ) will return True.

DELETE

Use Insert From URL with the following cURL options:

"-X DELETE -D $responseHeaders"

If deletion was successful, PatternCount ( $responseHeaders ; "204 No Content" ) will return True.

HEAD

Use Insert From URL with the following cURL options:

--head

The result will include headers that you may wish to parse out, such as Content-Type and Content-Length. Here's one way to extract a header from the result $result:

Let ([
  ~header = "Content-Type" ;
  ~start = Position ( $result ; ~header ; 1 ; 1 ) + Length ( ~header ) + 2 ;
  ~end = Position ( $result ; "¶" ; ~start ; 1 ) ;
  ~value = Middle ( $result ; ~start ; ~end - ~start )
];
~value
)