Public/Save-DokuAttachment.ps1

function Save-DokuAttachment {
    [CmdletBinding(PositionalBinding = $true)]
    [OutputType([System.IO.FileInfo])]
    param
    (
        [Parameter(Mandatory = $true,
                   Position = 1,
                   ValueFromPipeline = $true,
                   ValueFromPipelineByPropertyName = $true,
                   HelpMessage = 'The full name of the file to get')]
        [ValidateNotNullOrEmpty()]
        [string[]]$FullName,
        [Parameter(Mandatory = $false,
                   Position = 2,
                   HelpMessage = 'The path to save the attachment to, including filename & extension')]
        [ValidateScript({ Test-Path -Path $_ -IsValid })]
        [string]$Path,
        [Parameter(Mandatory = $false,
                   Position = 3,
                   HelpMessage = 'Force creation of output file, overwriting any existing files')]
        [switch]$Force
    )

    begin {}

    process {
        foreach ($AttachmentName in $FullName) {
            $APIResponse = Invoke-DokuApiCall -MethodName 'wiki.getAttachment' -MethodParameters @($AttachmentName)
            if ($APIResponse.CompletedSuccessfully -eq $true) {
                Write-Verbose $APIResponse.XMLPayloadResponse
                if ((Test-Path -Path $Path) -and (!$Force)) {
                    Throw "File with that name already exists at: $Path"
                } else {
                    Remove-Item -Path $Path -Force -ErrorAction SilentlyContinue
                    $RawFileData = [string]($APIResponse.XMLPayloadResponse | Select-Xml -XPath "//value/base64").node.InnerText
                    $RawBytes = [Convert]::FromBase64String($RawFileData)
                    [IO.File]::WriteAllBytes($Path, $RawBytes) | Out-Null
                    $ItemObject = (Get-Item -Path $Path)
                    $ItemObject
                }
            } elseif ($null -eq $APIResponse.ExceptionMessage) {
                Write-Error "Fault code: $($APIResponse.FaultCode) - Fault string: $($APIResponse.FaultString)"
            } else {
                Write-Error "Exception: $($APIResponse.ExceptionMessage)"
            }
        } # foreach attachment
    } # process

    end {}
}