Remove-UnlockedTempFiles.ps1

# Declare variable storing target user's username.
$User = "TEST"
# Set working directory to C:\Users\$User\AppData\Local\Temp.
Set-Location -LiteralPath C:\Users\$User\AppData\Local\Temp
# Declare variable storing a timestamp of 24 hours ago.
$CurrentTimeMinus24Hours = (Get-Date).AddHours(-24)
# Declare variable (array) storing list of files in temp directory.
$Files = @(Get-ChildItem -Path . -File)
# Declare variable storing Log file.
$Log = "C:\TempFileDeletionLog.log"

# Function for getting a precise DateTime string for use in logging. It will be formatted for your timezone.
function Get-DateTimeString {
    Get-Date -Format O
}

<#
Function to test whether or not a file is locked. Credit to Ben Baird here:
https://social.technet.microsoft.com/Forums/windowsserver/en-US/74ea3752-9403-4296-ab98-d03fcc12b608/how-to-check-to-see-if-a-file-is-openlocked-before-trying-to-copy-it?forum=winserverpowershell
#>
function Test-FileLock
{
	param
	(
		[parameter(Mandatory=$true,ValueFromPipelineByPropertyName=$true)]
		[Alias("FullName")]
		[string]$Path,
		[switch]$PassThru
	)
	begin {}
	Process
	{
	 $oFile = New-Object System.IO.FileInfo $Path

	 if ((Test-Path -Path $Path) -eq $false)
	 {
		 if ($PassThru.IsPresent -eq $false)
		 {
		 	$false
		 }
	 	return
	 }

	 try
	 {
		 $oStream = $oFile.Open([System.IO.FileMode]::Open, [System.IO.FileAccess]::ReadWrite, [System.IO.FileShare]::None)
		 if ($oStream)
		 {
		  $oStream.Close()
		 }
		 if ($PassThru.IsPresent -eq $false)
		 {
		 	$false
		 }
		 else
		 {
		 	Get-Item $Path
		 }
	 }
	 catch
	 {
	 	# file is locked by a process.
		 if ($PassThru.IsPresent -eq $false)
		 {
		 	$true
		 }
	 }
	}
	end {}
}

# ForEach loop that will test for multiple conditions, take actions based on those conditions, and log the results based on those actions for every file in the $Files array.
$ErrorActionPreference = "SilentlyContinue"
foreach ($File in $Files) {
    if ($File.LastWriteTime -lt $CurrentTimeMinus24Hours) {
		$File | Test-FileLock -PassThru | Remove-Item
        if ((Get-Item $File).Exists) {
			Add-Content -Path $Log -Value "$(Get-DateTimeString)> C:\$User\AppData\Local\Temp\$File was not deleted because it was locked."
		} else {
            Add-Content -Path $Log -Value "$(Get-DateTimeString)> C:\$User\AppData\Local\Temp\$File has been deleted."
        }
    } else {
        Add-Content -Path $Log -Value "$(Get-DateTimeString)> C:\$User\AppData\Local\Temp\$File was not deleted because it has been written to in the last 24 hours."
    }
}