How to skip file download with powershell if file exists

Question

I have the following script which downloads some files from channel 9:

function Get-Media
{
    [CmdletBinding()]
    param
    (
        [Object]
        $url,
        [Object]
        $title,
        [Object]
        $path
    )

    $u = New-Object System.Uri($url)
    $name = $title
    $extension = [System.IO.Path]::GetExtension($u.Segments[-1])
    $fileName = $name + $extension

    #$fileName = $fileName -replace "’", ''
    #$fileName = $fileName -replace "\?", ''
    #$fileName = $fileName -replace ":", ''
    #$fileName = $fileName -replace '/', ''
    #$fileName = $fileName -replace ",", ''
    #$fileName = $fileName -replace '"', ''
    #$fileName = $fileName -replace '|', ''
    #$fileName = $fileName -replace '\#', ''
    #$fileName = $fileName -replace '-', ''

    $fileName = $fileName -replace '(-|#|\||"|,|/|:|â|€|™|\?)', ''

    if (Test-Path($fileName)) {
        Write-Host 'Skipping file, already downloaded' -ForegroundColor Yellow
    }
    else
    {
        Invoke-WebRequest $url -OutFile (Join-Path -Path $path -ChildPath $fileName)
    }
}

function Get-VideosFromFeed
{
    [CmdletBinding()]
    param
    (
        [Object]
        $feedUrl,
        [Object]
        $folder,
        [Object]
        $path
    )

    $feed=[xml](New-Object System.Net.WebClient).DownloadString($feedUrl)

    $downloadPath = (Join-Path -Path $path -ChildPath $folder)

    if (Test-Path($downloadPath)) {
        Write-Host 'Skipping folder, already exists' -ForegroundColor Yellow
    }
    else
    {
        New-Item -Path $downloadPath -ItemType directory -WarningAction SilentlyContinue
    }

    foreach($i in $feed.rss.channel.item) {
        foreach($m in $i.group){
            foreach($u in $m.content `
                    | Where-Object { `
                            $_.url -like '*mid.mp4' `
                         } | Select-Object -Property @{Name='url'; Expression = {$_.url}}, `
                                                     @{Name='title'; Expression = {$i.title}})
            {
                Get-Media -url $u.url -title $u.title -path $downloadPath
            }
        }
    }
}

$physicalPath = "D:\Videos\Series"
Get-VideosFromFeed -feedUrl 'https://channel9.msdn.com/Series/Deep-Dive-into-the-Office-365-App-Model/feed/mp4high'                                            -path $physicalPath -folder 'Deep-Dive-into-the-Office-365-App-Model'

I need to improve it to skip the download if the file already exists.

Answer 1

You have to pass the whole path to the Test-Path cmdlet to check whether the file exist. Then all you have to do is to return the function:

# ....
$fileName = $fileName -replace '(-|#|\||"|,|/|:|â|€|™|\?)', ''
$filePath = Join-Path $path $fileName

if (Test-Path($filePath)) 
{
    Write-Host 'Skipping file, already downloaded' -ForegroundColor Yellow
    return
}

Invoke-WebRequest $url -OutFile $filePath