Delving into Windows PowerShell

Delving into Windows Powershell

Originally posted on 2019-03-11.

During the duration of my open source releases, I found myself going back to Flashpoint and curating for fun.

Freearcade (as I mentioned in my previous post) is a site that mainly has Java applet games and those games tend to have a lot of assets.

Deciding to curate another Java applet game, I realized that it wasn’t only Wiz3 with a bunch of assets but this game as well.

Flashpoint comes with autocurator scripts (which I didn’t know at the time)but I decided to make my own using Windows PowerShell. I’ve been wanting to learn Powershell scripting after enjoying bash, and decided that as a struggling Windows developer, I should get to know the tools on this platform. So this dilemma was a good excuse.

So this is my first PowerShell script.

Issue:

Doing HTTP GET requests on multiple Flashpoint redirector 404s.

Redirector

You can copy all 404 URLs by hitting Tools -> Copy All 404 Not Found URLs. It’s tedious to go to each URL and download files one by one.

Solution:

Make a PowerShell Script to automate it.

The Script URL

Get-Assets.ps1

<# A useful powershell script to download files off of URLs #>

# $output = whatever folder location you want the script to save the files to. 
$output = "..\..\Flashpoint Core 2.3\Games\Flash\htdocs\ww2.freearcade.com\Jetslalom.jav\"
$client = new-object System.Net.WebClient

Accept the location of where the user wants to save the assets to in $output (This is currently manually changed in the script itself - need to do it through the UI)
$client sets the Webclient object that provides methods to send data and receive data from URLs

while($select -ne 0){
    Write-Host "Select from the following options:
                        1. Exit script
                        2. Grab asset from one URL
                        3. Grab multiple assets from multiple URLs"
    $select = Read-Host -Prompt "Enter your selection"

The while line loops the prompt until the user exits the script so that you can keep grabbing multiple or single assets without restarting.
Write-Host writes to the screen, and Read-Host reads user input - as opposed to using Write-Host, you can use the -Prompt instead. But here I wanted to show all the options for the script.

    switch($select){
        1{
            $url = Read-Host -Prompt "Enter URL (with http included)"
            $file = Split-Path $url -Leaf
            $client.DownloadFile($url, $output + $file)
        }

The switch statement is explanatory for the script selections
If it’s selection 1, read user input and save it
PowerShell doesn’t download files off of a URL location without knowing the name of the file prior. But with a script it’s impossible to anticipate what filename something will be. So Split-Path $url -Leaf splits the URL into portions, the -Leaf parameter referring to the last section of a URL (i.e http://www.example.com/src/leaf.png would grab just the leaf of the URL, leaf.png)
Then using the WebClient object, we can use the method DownloadFile to download from the URL and save it to the $output path plus the leaf portion of the URL we extracted, in this case an asset file.

        2{
            $txt = Read-Host -Prompt "Enter location of input file with the 404 URLS (if in same directory, it's .\ syntax"
            foreach($line in Get-Content $txt){
                $filename = Split-Path $line -leaf
                $client.DownloadFile($line, $output + $filename)
            }
        }
    }

For multiple URLs, we ask the user to place the copied 404s from Redirector into a txt file for easy processing. They are divided by a line break (but that doesn’t matter to PowerShell).
The foreach method loops through the file, using Get-Content cmdlet. In the MS docs, text files are “read one line at a time and returns a collection of objects, each of which represents a line of content”. So we can right away Split-Path again to get the names of the files and download each line (which is a URL).


    # Line 29 is optional, it's to make sure the game is reset to run the new assets
    Stop-Process -name "appletviewer" -ErrorAction SilentlyContinue
}

Stop-Process line stops the appletviewer (which is running the game), as a way to force the tester to restart the game. Redirector (and the game) does not update the fact that the assets have been downloaded dynamically. A restart is required to continue debugging.
-ErrorAction SilentlyContinue Allows the command to fail without complaining if it finds that the process is not running at the moment.

Write-Host "Thanks for using my tool!"

<# TODO: Allow users to specify output location - most likely manually for now
 - Maybe talk to redirector to grab 404 urls
 - Dynamically add missing folders #>

Rest of the code with some TODOs.

This script I passed on to the Discord and was happy to see that some people had cloned it on Github (through the analytics). It’s optimized for Freearcade.com java applets but I hope to expand it to become better.

/ Delving into Windows PowerShell Created 2019-03-11 Modified 2019-03-11