Explore useful Automation Techniques with Powershell on Windows

March 03, 2021

Introduction

We will list few interesting automation techniques with powershell.

Get the directory of your current script

$script_path = dir "$($myInvocation.MyCommand.Definition)"
$script_path = $script_path.DirectoryName

Get the name of your script

$script_name = $MyInvocation.MyCommand.Name

Writing something to console

Write-Output "================================================"
Write-Output ""
Write-Output "  My Fancy Banner"
Write-Output ""
Write-Output "  - Installs All Dependencies"
Write-Output ""
Write-Output "  To run silently add -Silent"
Write-Output "================================================"
Write-Output ""

Import Modules

If you have written powershell script in another file, you can include that with Import-Module

$script_path = dir "$($myInvocation.MyCommand.Definition)"
$script_path = $script_path.DirectoryName

Import-Module $script_path\Modules\my-module.psm1

Check user Admin or not

First we can write functions

function Get-IsAdministrator
{
    $Identity = [System.Security.Principal.WindowsIdentity]::GetCurrent()
    $Principal = New-Object System.Security.Principal.WindowsPrincipal($Identity)
    $Principal.IsInRole([System.Security.Principal.WindowsBuiltInRole]::Administrator)
}


function Get-IsUacEnabled
{
    (Get-ItemProperty HKLM:\Software\Microsoft\Windows\CurrentVersion\Policies\System).EnableLua -ne 0
}

Then use them,

If (!(Get-IsAdministrator)) {
  ...
}

# check for UAC enabled user
If (Get-IsUacEnabled) {
  ...
}

Run powershell as Administrator, if not

If (!(Get-IsAdministrator)) {
    If (Get-IsUacEnabled) {
        # We are not running "as Administrator" - so relaunch as administrator
        # Create a new process object that starts PowerShell
        $newProcess = new-object System.Diagnostics.ProcessStartInfo "PowerShell";

        # Specify the current script path and name as a parameter
        $newProcess.Arguments = $myInvocation.MyCommand.Definition

        # Specify the current working directory
        $newProcess.WorkingDirectory = "$script_path"

        # Indicate that the process should be elevated
        $newProcess.Verb = "runas";

        # Start the new process
        [System.Diagnostics.Process]::Start($newProcess);

        # Exit from the current, unelevated, process
        Exit
    } Else {
        Throw "You must be administrator to run this script"
    }
}

Create File or Directory

New-Item "Dir_Name" -ItemType Directory -Force

Delete File or Directory

Remove-Item "my_file"

Delete Directory recursively

Remove-Item "folder" -Force -Recurse

Detecting 32-bit ot 64-bit architecture

If ([System.IntPtr]::Size -ne 4) {
    Write-Output "Detected 64bit Architecture..."

    ...
} Else {
    Write-Output "Detected 32bit Architecture"

Check for file existence

Test-Path "file_path"

# Example

If (Test-Path "file_path") {
    # Found file
    Write-Output " - File Found . . ."
}

Download File from URL

DownloadFileWithProgress $url $file

Where url is the actual http url from where you want to download file. And file is the destination file where you want to write.

Start a process with command options

Start-Process $file -ArgumentList <command options>

Example of installing NSIS,

# Downloading nsis
$file = "nsis.exe"
$url = "URL for NSIS"
DownloadFileWithProgress $url $file

Start-Process $file -ArgumentList '/S' -Wait -NoNewWindow -PassThru

Updating System variable PATH

Temporarily adding a path to PATH variable

To temporarily add a path to PATH variable,

$env:Path += ";my_path"

Note: Do not forgot to use +. Else, it will overwrite previous path

Add a path to PATH permanently

$env:Path += ";my_path"
[Environment]::SetEnvironmentVariable
     ("Path", $env:Path, [System.EnvironmentVariableTarget]::Machine)

Add path when its not added

We will first get PATH variable, and check if our desired value is there. If its not there, we will add that.

$Path = (Get-ItemProperty -Path 'Registry::HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\Environment' -Name PATH).Path

$my_value = "xyz"

If (!($Path.ToLower().Contains("$my_value".ToLower()))) {
    $newPath  = "$my_value"
    Set-ItemProperty -Path 'Registry::HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\Environment' -Name PATH -Value $newPath
    $env:Path = $newPath
}

Get folder items and get its count

if ( (Get-ChildItem "my_folder | Measure-Object).Count -eq 0 ) {
        # folder empty
  ...
}

Copy and Move Files/Folders

For single file

Copy-Item "my_file" "des_dir" -Force

Move-Item "my_file" "des_dir"" -Force

For multiple files using *

Copy-Item "my_folder\*.dll" "dest_folder" -Force

Move-Item "my_folder\*.dll" "dest_folder" -Force

Replace File Content Dyamically

Example, your file path is: /my/path/file.txt

And, you want to replace STR_TO_REPLACE string with target string TARGET_STRING

(Get-Content -path /my/path/file.txt -Raw) -replace 'STR_TO_REPLACE', 'TARGET_STRING' | Set-Content -Path /my/path/file.txt

And, if you have your value set in some environment variable name: MY_ENV_VAR,

(Get-Content -path /my/path/file.txt -Raw) -replace 'BRANCH_NOT_SET', $env:MY_ENV_VAR | Set-Content -Path /my/path/file.txt
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