Add a path to the machine PATH environment variable

Add-EnvironmentPath.ps1

Function Add-EnvironmentPath {
<#
.SYNOPSIS
Adds a path to the PATH environment variable at give scope.

.DESCRIPTION
Adds a Path to the PATH environment variable stored in the current process or in the Windows operating system registry key reserved for the current user or local machine.
In addition to that the command sorts the paths and removes duplicates.

.PARAMETER Path
The path to the PATH environment variable.

.PARAMETER scope
The scope which decides where to extend the PATH environment variable.

.EXAMPLE
Add-EnvironmentPath -Path "C:\WINDOWS\System32\WindowsPowerShell\v1.0\"

Since the default value for the parameter Scope is 'Machine' the path will be added to the PATH environment variable stored in 'HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\Environment'.

.EXAMPLE
Add-EnvironmentPath -Path "C:\WINDOWS\System32\WindowsPowerShell\v1.0\" -Scope User

Adds the given path to the environment variable stored in 'HKEY_CURRENT_USER\Environment'

.EXAMPLE
Add-EnvironmentPath -Path "C:\WINDOWS\System32\WindowsPowerShell\v1.0\" -Scope Process

Adds the given path to $env:PATH of the current process.
#>
  param(
    [Parameter(Mandatory=$true,Position=0,ValueFromPipeline=$true, ValueFromPipelineByPropertyName=$true)]
    [string]$Path,
    [Parameter(Mandatory=$false,Position=1)]
    [ValidateSet("Process", "User", "Machine")]
    [string]$Scope = "Machine")
  Process {
    $currentPaths = [System.Environment]::GetEnvironmentVariable("Path", $Scope)
    if ($currentPaths.indexOf($Path) -eq -1) {
      Write-Output "Updating PATH to include $Path`r`n"
      $paths = @(($currentPaths.Split(";") | ForEach-Object { $_.Trim(); } | Where-Object { -not([string]::IsNullOrWhiteSpace($_)) }) | Sort-Object);
      $paths += $Path;
      $new = [string]::Join(";", @($paths | Select-Object -Unique | Sort-Object));
      [System.Environment]::SetEnvironmentVariable("Path", $new, $Scope);
      ([string](refreshenv)) | Write-Output;
    }
  }
}