Download files over PSSession for PS<5 - powershell

Question

How do I download files from a remote server over a PSSession? I'm aware that PS5 introduced Copy-Item -FromSession, but both local and remote may be not running PS5. My files are also quite large so a simple Get-Content may be problematic.

Answer 1

You can read file on remote side as sequence of byte arrays, stream them thru remoting, and then assemble them back to file locally:
function DownloadSingleFile {
param(
[System.Management.Automation.Runspaces.PSSession] $FromSession,
[string] $RemoteFile,
[string] $LocalFile,
[int] $ChunkSize = 1mb
)
Invoke-Command -Session $FromSession -ScriptBlock {
param(
[string] $FileName,
[int] $ChunkSize
)
$FileInfo = Get-Item -LiteralPath $FileName
$FileStream = $FileInfo.OpenRead()
try {
$FileReader = New-Object System.IO.BinaryReader $FileStream
try {
for() {
$Chunk = $FileReader.ReadBytes($ChunkSize)
if($Chunk.Length) {
,$Chunk
} else {
break;
}
}
} finally {
$FileReader.Close();
}
} finally {
$FileStream.Close();
}
} -ArgumentList $RemoteFile, $ChunkSize | ForEach-Object {
$FileName = $ExecutionContext.SessionState.Path.GetUnresolvedProviderPathFromPSPath($LocalFile)
$FileStream = [System.IO.File]::Create($FileName)
} {
$FileStream.Write($_, 0, $_.Length)
} {
$FileStream.Close()
}
}