Check if file is in use before exporting - loops

Question

I'm writing a script that will export an excel file to a PDF. I got that part working, However, because I'm saving on top of an existing PDF it cannot be open when the export happens. I'm looking for a way to have PowerShell check if the file is currently open, and if so, wait for X seconds and then check again. If not it can proceed.
It currently works perfectly and breaks if the PDF is open, however I need it to loop.
Here's what I have so far:
$path = "c:\users\XXXXX\documents"
$xlFixedFormat = "Microsoft.Office.Interop.Excel.xlFixedFormatType" -as [type]
$excelFiles = Get-ChildItem -Path $path -Include spreadsheet.xlsx -Recurse
$File = "c:\users\XXXXX\documents\Exported.pdf"
try {
[IO.File]::OpenWrite($File).Close();
$true
} catch {
break
}
$objExcel = New-Object -ComObject Excel.Application
$objExcel.Visible = $false
foreach ($wb in $excelFiles) {
$filepath = Join-Path -Path $path -ChildPath ($wb.BaseName + ".pdf")
$workbook = $objExcel.Workbooks.Open($wb.FullName, 3)
$workbook.Saved = $true
"saving $filepath"
$workbook.ExportAsFixedFormat($xlFixedFormat::xlTypePDF, $filepath)
$objExcel.Workbooks.Close()
}
$objExcel.Quit()

Answer 1

This should do what you want; thanks to Ben Baird for the Test-FileLock function.
function Test-FileLock {
param ([parameter(Mandatory=$true)][string]$Path)
$oFile = New-Object System.IO.FileInfo $Path
if ((Test-Path -Path $Path) -eq $false)
{
return $false
}
try
{
$oStream = $oFile.Open([System.IO.FileMode]::Open, [System.IO.FileAccess]::ReadWrite, [System.IO.FileShare]::None)
if ($oStream)
{
$oStream.Close()
}
# file is unlocked.
$false
}
catch
{
# file is locked by a process.
return $true
}
}
$path = "c:\users\XXXXX\documents"
$xlFixedFormat = "Microsoft.Office.Interop.Excel.xlFixedFormatType" -as [type]
$excelFiles = Get-ChildItem -Path $path -Include spreadsheet.xlsx -Recurse
$File = "c:\users\XXXXX\documents\Exported.pdf"
while((Test-FileLock $file) -eq $true)
{
Start-Sleep -Seconds 3
}
$objExcel = New-Object -ComObject Excel.Application
$objExcel.Visible = $false
foreach ($wb in $excelFiles) {
$filepath = Join-Path -Path $path -ChildPath ($wb.BaseName + ".pdf")
$workbook = $objExcel.Workbooks.Open($wb.FullName, 3)
$workbook.Saved = $true
"saving $filepath"
$workbook.ExportAsFixedFormat($xlFixedFormat::xlTypePDF, $filepath)
$objExcel.Workbooks.Close()
}
$objExcel.Quit()
The code will check for a file lock and if it is detected wait 3 seconds and then try again. Once the lock is cleared the PDF export code will run.