How do I check the filehash of a file thats online in PowerShell?

April 23, 2022

So well, I am making a pull request to Chris Titus Tech’s Ultimate Windows Toolkit, and I wanna make something that checks if it’s updated. But when I try running Get-FileHash -Algorithm SHA256 https://raw.githubusercontent.com/fgclue/etcher/master/desktop.ini It just says:

Get-FileHash: Cannot find drive. A drive with the name 'https' does not exist.

And I want to make it look something like this:

$hash = Get-FileHash -Algorithm SHA256 URL
$chash = Get-FileHash -Algorithm SHA256 win10debloat.ps1

if ($hash -ne $chash){
     Write-Host "There is an update!"
     Write-Host "Update?"
     $Opt = Read-Host "Choice"     
     if (Opt -ne y){
          exit
     }
     if (Opt -ne yn){
          Start-Process "https://github.com/ChrisTitusTech/win10script/"
          Write-Host Please download the new version and close this windows.
     }
}

>Solution :

I’m not totally sure what actually you want to compare but here is how you can test if what you have is up to date without downloading anything, in this case I believe you need to use IO.MemoryStream to get the hash of the remote file.

There is likely a better way to do it, also note, this code is using UTF8 Encoding with a BOM for getting the remote file bytes, you need to make sure the encoding is correct, i.e.: if you need UTF8 no BOM, use [System.Text.UTF8Encoding]::new().GetBytes(...) instead.

$uri = 'https://raw.githubusercontent.com/fgclue/etcher/master/desktop.ini'
$theHashIHave = Get-FileHash myfilehere.ext -Algorithm SHA256

try {
    $content = Invoke-RestMethod $uri
    $memstream = [System.IO.MemoryStream]::new(
        [System.Text.Encoding]::UTF8.GetBytes($content)
    )
    $thisFileHash = Get-FileHash -InputStream $memstream -Algorithm SHA256
    if($theHashIhave.Hash -eq $thisFileHash.Hash) {
        "all good"
    }
    else {
        "should update here"
    }
}
finally {
    $memstream.foreach('Dispose')
}