Bulk File Renaming Format Change - powershell

Question

I'm attempting a proof of concept for my department which attempts to extract attached files from .msg files located in a set of folders. I'm still struggling with getting up to speed with PowerShell, especially when using modules and rename features.
I found a module on-line that pretty well does everything I need except that I need a slightly different variant in the new attachment filename. i.e. Not sure how to modify line with code below...
$attFn = $msgFn -replace '\.msg$', " - Attachment - $($_.FileName)"
The code below extracts the attached files and renames them along the lines of...
An email file MessageFilename.msg, with an attachment AttachmentFilename.pdf extracts the attached filename to Messagefilename - Attachement - AttachmentFilename.pdf
I really need the attachment filename to be extracted into the format AttachmentFilename.pdf only. The problem I keep having is that I keep losing the path to the .msg filename so get errors when attempting the rename to a path that doesn't exist. I've tried a few options in debug mode but keep losing the path context when attempting the 'replace'.
Any help appreciated...
The borrowed code is...
##
## Source: https://chris.dziemborowicz.com/blog/2013/05/18/how-to-batch-extract-attachments-from-msg-files-using-powershell/
##
## Usage: Expand-MsgAttachment *
##
##
function Expand-MsgAttachment
{
[CmdletBinding()]
Param
(
[Parameter(ParameterSetName="Path", Position=0, Mandatory=$True)]
[String]$Path,
[Parameter(ParameterSetName="LiteralPath", Mandatory=$True)]
[String]$LiteralPath,
[Parameter(ParameterSetName="FileInfo", Mandatory=$True, ValueFromPipeline=$True)]
[System.IO.FileInfo]$Item
)
Begin
{
# Load application
Write-Verbose "Loading Microsoft Outlook..."
$outlook = New-Object -ComObject Outlook.Application
}
Process
{
switch ($PSCmdlet.ParameterSetName)
{
"Path" { $files = Get-ChildItem -Path $Path }
"LiteralPath" { $files = Get-ChildItem -LiteralPath $LiteralPath }
"FileInfo" { $files = $Item }
}
$files | % {
# Work out file names
$msgFn = $_.FullName
$msgFnbase = $_.BaseName
# Skip non-.msg files
if ($msgFn -notlike "*.msg") {
Write-Verbose "Skipping $_ (not an .msg file)..."
return
}
# Extract message body
Write-Verbose "Extracting attachments from $_..."
$msg = $outlook.CreateItemFromTemplate($msgFn)
$msg.Attachments | % {
# Work out attachment file name
$attFn = $msgFn -replace '\.msg$', " - Attachment - $($_.FileName)"
# Do not try to overwrite existing files
if (Test-Path -literalPath $attFn) {
Write-Verbose "Skipping $($_.FileName) (file already exists)..."
return
}
# Save attachment
Write-Verbose "Saving $($_.FileName)..."
$_.SaveAsFile($attFn)
# Output to pipeline
Get-ChildItem -LiteralPath $attFn
}
}
}
End
{
Write-Verbose "Done."
}
}

Answer 1

$msgFn = $_.FullName
says that it will be a full path in the form c:\path\to\file.msg.
So you can use:
# extract path, e.g. 'c:\path\to\'
$msgPath = Split-Path -Path $msgFn
# make new path, e.g. 'c:\path\to\attachment.pdf'
$newFn = Join-Path -Path $msgPath -ChildPath ($_.FileName)