PowerShell version of "GuidGen" application

GuidGen.ps1

<#
.SYNOPSIS
    GUID generator

.DESCRIPTION
    uuidgen.exe replacement.

    Complete functional superset though some parameter syntax differs due to Powershell parameter handling:

    | uuidgen       | guidgen               | Description                           |
    |---------------|-----------------------|---------------------------------------|
    | -x            | --- (not supported)   | Generate sequential (V1) UUIDs        |
    | -i            | -Type IDLInterface    | Output UUI as an initialized C struct |
    | -s            | -Type StructInterface | Output UUI as an initialized C struct |
    | -c            | -Upper                | Output UUID in upper case             |
    | -o<filename>  | -Path <filename>      | Redirect output to a file             |
    | -n<number>    | -N <number>           | Number of UUIDs to generate           |
    | -v            | --- (not supported)   | Display version information           |
    | -h,?          | -Help                 | Display command option summary        |

.PARAMETER Type
    Type of GUID output to generate.

.PARAMETER Upper
    Emit GUID as upper case (default=lower case).

.PARAMETER N
    Number of GUIDs to generate.

.PARAMETER Path
    Specifies the file to redirect the output.

#>
param (
    [ValidateSet('Raw', 'Ole', 'Define', 'Struct', 'Registry', 'AttributeBracket', 'AttributeBrace', 'IDLInterface', 'StructInterface')]
    [Parameter(Position = 0)][string]$Type='Raw',

    [switch]$Upper,

    [int]$N=1,

    [string]$Path
)

Set-StrictMode -Version 3.0

$ErrorActionPreference = "Stop"

function New-GuidObject {
    $guid = (New-Guid).Guid
    $m = Select-String `
        -InputObject $guid `
        -Pattern '([0-9A-Fa-f]{8})-([0-9A-Fa-f]{4})-([0-9A-Fa-f]{4})-([0-9A-Fa-f]{2})([0-9A-Fa-f]{2})-([0-9A-Fa-f]{2})([0-9A-Fa-f]{2})([0-9A-Fa-f]{2})([0-9A-Fa-f]{2})([0-9A-Fa-f]{2})([0-9A-Fa-f]{2})'
    if ($Upper) {
        $guid = $guid.ToUpper()
    }
    [PSCustomObject]@{
        'Guid'    = $guid
        'Data1'   = $m.Matches.Groups[1].Value
        'Data2'   = $m.Matches.Groups[2].Value
        'Data3'   = $m.Matches.Groups[3].Value
        'Data4_1' = $m.Matches.Groups[4].Value
        'Data4_2' = $m.Matches.Groups[5].Value
        'Data4_3' = $m.Matches.Groups[6].Value
        'Data4_4' = $m.Matches.Groups[7].Value
        'Data4_5' = $m.Matches.Groups[8].Value
        'Data4_6' = $m.Matches.Groups[9].Value
        'Data4_7' = $m.Matches.Groups[10].Value
        'Data4_8' = $m.Matches.Groups[11].Value
    }
}

function New-GuidRaw {
    '{0}' -f (New-GuidObject).Guid
}

function New-GuidOle {
    $guid = New-GuidObject

    "// {{{0}}}`nIMPLEMENT_OLECREATE(<<class>>, <<external_name>>,`n0x{1}, 0x{2}, 0x{3}, 0x{4}, 0x{5}, 0x{6}, 0x{7}, 0x{8}, 0x{9}, 0x{10}, 0x{11});" -f `
        $guid.Guid, $guid.Data1, $guid.Data2, $guid.Data3, $guid.Data4_1, $guid.Data4_2, $guid.Data4_3, $guid.Data4_4, $guid.Data4_5, $guid.Data4_6, $guid.Data4_7, $guid.Data4_8
}

function New-GuidDefine {
    $guid = New-GuidObject

    "// {{{0}}}`nDEFINE_GUID(<<name>>,`n0x{1}, 0x{2}, 0x{3}, 0x{4}, 0x{5}, 0x{6}, 0x{7}, 0x{8}, 0x{9}, 0x{10}, 0x{11});" -f `
        $guid.Guid, $guid.Data1, $guid.Data2, $guid.Data3, $guid.Data4_1, $guid.Data4_2, $guid.Data4_3, $guid.Data4_4, $guid.Data4_5, $guid.Data4_6, $guid.Data4_7, $guid.Data4_8
}

function New-GuidStruct {
    $guid = New-GuidObject

    "/* {{{0}}} */`nstatic const GUID <<name>> =`n{{ 0x{1}, 0x{2}, 0x{3}, {{ 0x{4}, 0x{5}, 0x{6}, 0x{7}, 0x{8}, 0x{9}, 0x{10}, 0x{11} }} }};" -f `
        $guid.Guid, $guid.Data1, $guid.Data2, $guid.Data3, $guid.Data4_1, $guid.Data4_2, $guid.Data4_3, $guid.Data4_4, $guid.Data4_5, $guid.Data4_6, $guid.Data4_7, $guid.Data4_8
}

function New-GuidRegistry {
    '{{{0}}}' -f (New-GuidObject).Guid
}

function New-GuidAttributeBracket {
    '[Guid("{0}")]' -f (New-GuidObject).Guid
}

function New-GuidAttributeBrace {
    '<Guid("{0}")>' -f (New-GuidObject).Guid
}

function New-GuidIDLInterface {
    @"
[
uuid({0}),
version(1.0)
]
interface INTERFACENAME
{{

}}
"@ -f (New-GuidObject).Guid
}

function New-GuidStructInterface {
    $guid = New-GuidObject
    @"
INTERFACENAME = {{ /* {0} */
    0x{1},
    0x{2},
    0x{3},
    {{0x{4}, 0x{5}, 0x{6}, 0x{7}, 0x{8}, 0x{9}, 0x{10}, 0x{11}}}
  }};
"@ -f $guid.Guid, $guid.Data1, $guid.Data2, $guid.Data3, $guid.Data4_1, $guid.Data4_2, $guid.Data4_3, $guid.Data4_4, $guid.Data4_5, $guid.Data4_6, $guid.Data4_7, $guid.Data4_8
}


$out = for ($i=0; $i -lt $N; $i++) {
    switch ($Type) {
        'Raw' { New-GuidRaw }
        'Ole' { New-GuidOle }
        'Define' { New-GuidDefine }
        'Struct' { New-GuidStruct }
        'Registry' { New-GuidRegistry }
        'AttributeBracket' { New-GuidAttributeBracket }
        'AttributeBrace' { New-GuidAttributeBrace }
        'IDLInterface' { New-GuidIDLInterface }
        'StructInterface' { New-GuidStructInterface }
    }
}
if ($Path) {
    Set-Content -Path $Path -Value $out
} else {
    $out
}

[switch]$Upper=$false,
[string]$Path=$null

no need to put defaults. these aren't marked [Mandatory] so PowerShell will use logical defaults ($Upper will be $false, and $Path will be $null)

Indeed. Done