Public/Get-specFileHashAndDownload.ps1
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function Get-specFileHashAndDownload { <# .SYNOPSIS Obtains the file hash for a local file and compares it with the hash of a remote file. Downloads the remote file if hashes differ or the local file does not exist. .DESCRIPTION This helper function obtains the hash of a local file and the hash of a remote file, compares them, and takes appropriate actions based on the comparison. .PARAMETER deviceScriptLocationOnDevice The local path of the file on the device. .PARAMETER deviceSourceURL The URL of the remote file. .EXAMPLE Get-specFileHashAndDownload -ScriptLocationOnDevice "C:\Path\ToLocal\File.ps1" -SourceURL "https://example.com/Remote/File.ps1" .NOTES Author: owen.heaume Version: 1.0 #> param ( [string]$deviceScriptLocationOnDevice, [string]$deviceSourceURL ) Write-Host "Obtaining local file hash: '$deviceScriptLocationOnDevice'...." -ForegroundColor DarkCyan -NoNewline #1. Get File hashes of the local file which will be used to compare against remote file. (Assign NULL if local file does not exist) If (Test-Path $deviceScriptLocationOnDevice) { $LocalHash = Get-SpecMDFileHashBase64 -FilePath $deviceScriptLocationOnDevice Write-Host 'OK' -ForegroundColor DarkGreen } else { $LocalHash = $null Write-Host 'File does not exist on this device' -ForegroundColor DarkGray } #2. Get the hash of the remote file Write-Host 'Obtaining the remote file hash....' -ForegroundColor DarkCyan -NoNewline try { $RemoteHash = Get-SpecMDFileHashBase64 -FileURL $deviceSourceURL -ErrorAction Stop Write-Host 'OK' -ForegroundColor DarkGreen } catch { Write-Host 'Unable to get the remote file hash - check the URL is correctly formed' -ForegroundColor DarkYellow } #2b. Display the hashes Write-Host 'Comparing hash values....' -ForegroundColor DarkCyan Write-Host " Local hash: $LocalHash" -ForegroundColor DarkGray Write-Host "Remote hash: $RemoteHash" -ForegroundColor DarkGray #3. If hashes match - then nothing to do if ($LocalHash -eq $RemoteHash) { Write-Host "The hashes match - the file stored on the device is the latest version`n" -ForegroundColor DarkGreen } #4. Hashes do not match, or the local file does not exist - download the file from blob storage. if ($LocalHash -ne $RemoteHash) { Write-Host 'Local file hash is different or null compared to remote file, so downloading remote file' -ForegroundColor DarkGray # Download file to designated path on the local device (overwrites if already there) $result = Get-SpecBlobFileFromURL -FileUrl $deviceSourceURL -DestinationFilePath $deviceScriptLocationOnDevice if ($null -eq $result) { Write-Host "Downloaded file OK`n" -ForegroundColor DarkGreen } else { Write-Host 'An error occurred downloading the file' -ForegroundColor DarkYellow } } } |