Streaming basics - reading large file from RESTful API

Question

Hey all -
My command of PowerShell is pretty rudimentary, though I have written a number of scripts.  In a recent example, I was trying to redirect the output of my firm's RESTful API - a small .txt file - into a file, using | out-file <path and
file>.  THat worked 
just fine.  However, when I tried to do this with a docx or pdf file, the result was that I ended up with a small file that was 
unopenable.
I gather what I need to do is stream the content to a file, but I can't quite see how that is done in Powershell.  The files might  be
many MB in size and take upwards of 30 seconds to transfer.
Any basic guidance on how to approach this would be appreciated.  Thanks -
Paul
Paul

Answer 1

Oh so close!
I'm getting hung up on how to create and pass the session object itself. 
My first command,
Invoke-RestMethod -Uri
<apiKey>9588060291......</apiKey><email>...</email><password>...</password><endOtherSessions>T</endOtherSessions></createSession">https://test.lofco.com/v1/ILCGLServices/session?method=CREATE"&"client=DEV-TEST"&"xml=<createSession><apiKey>9588060291......</apiKey><email>...</email><password>...</password><endOtherSessions>T</endOtherSessions></createSession>
-SessionVariable s -Outfile 'c:\LofCo\Demos\API Code Samples\XML\Output\createsession_response.xml'
returns successfully; I can see in the output file the session ID. I was hoping this was captured in the variable s via the -SessionVariable approach, but when I run the second command:
Invoke-RestMethod -Uri
<acceptSplash>T</acceptSplash></workspaceEntryRequest">https://test.lofco.com/services/workspaces/entry?client=DEV-TEST"&"workspaceId=226691"&"method=CREATE"&"xml=<workspaceEntryRequest><acceptSplash>T</acceptSplash></workspaceEntryRequest>
-WebSession $s -Method Post -Outfile 'C:\LofCo\Demos\API Code Samples\XML\Output\enterexchange_response.xml'
I get a 403 error indicating the session has expired or is otherwise invalid. I'm clearly confused as to how to capture this session and pass it along...
Any pointers on that piece?  And thanks for your previous assistance.
Paul
Paul