Example of how to download a file using Posh-SSH via SSH/SFTP

Download-SFTPFile.ps1

#requires -Modules Posh-SSH

$hostname     = "server.contoso.com"
$keyFile      = "C:\_temp\ssh-key.pem"
$userName     = "johndoe"
$certPassword = ConvertTo-SecureString -String 'password' -AsPlainText -Force
$localPath    = "c:\_temp\file.dat"
$remotePath   = "/folder1/folder2/folder3"
$remoteFile   = "file.dat"

New-SFTPSession `
    -ComputerName $hostname `
    -KeyFile      $keyFile `
    -Credential   ([PSCredential]::new($userName, $certPassword)) `
    -AcceptKey

Set-SFTPLocation `
    -SessionId 0 `
    -Path $remotePath

Get-SFTPFile `
    -SessionId  0 `
    -RemoteFile $remoteFile `
    -LocalPath  $localPath `
    -Overwrite

Remove-SFTPSession `
    -SessionId 0