Determine if current PowerShell Process is 32-bit or 64-bit?

When running a PowerShell script on a x64-bit OS platform, how can you determine in the script what version of PowerShell (32-bit or 64-bit) the script is running on?

Background
Both 32-bit and 64-bit versions of PowerShell are installed by default on a 64-bit platform such as Windows Server 2008. This can lead to difficulties when a PowerShell script is ran that must target a specific architecture (i.e. using 64-bit for a script for SharePoint 2010, in order to consume the 64-bit libraries).

Related question:

• What is the best way to program against powershell's x64 vs. x86 variability? This question deals with code running against both 32-bit and 64-bit architectures. My question deals with the case when you want to ensure the script only runs against the correct version.

If you're shell is running on .NET 4.0 (PowerShell 3.0):

PS> [Environment]::Is64BitProcess
True

To determine in your script what version of PowerShell you're using, you can use the following helper functions (courtesy of JaredPar's answer to an related question):

# Is this a Wow64 powershell host
function Test-Wow64() {
	return (Test-Win32) -and (test-path env:\PROCESSOR_ARCHITEW6432)
}

# Is this a 64 bit process
function Test-Win64() {
	return [IntPtr]::size -eq 8
}

# Is this a 32 bit process
function Test-Win32() {
	return [IntPtr]::size -eq 4
}

The above functions make use of the fact that the size of System.IntPtr is platform specific. It is 4 bytes on a 32-bit machine and 8 bytes on a 64-bit machine.

Note, it is worth noting that the locations of the 32-bit and 64-bit versions of Powershell are somewhat misleading. The 32-bit PowerShell is found at C:\Windows\SysWOW64\WindowsPowerShell\v1.0\powershell.exe, and the 64-bit PowerShell is at C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe, courtesy of this article.

You can use this as well. I tested it on PowerShell version 2.0 and 4.0.

$Arch = (Get-Process -Id $PID).StartInfo.EnvironmentVariables["PROCESSOR_ARCHITECTURE"];
if ($Arch -eq 'x86') {
    Write-Host -Object 'Running 32-bit PowerShell';
}
elseif ($Arch -eq 'amd64') {
    Write-Host -Object 'Running 64-bit PowerShell';
}

The value of $Arch will either be x86 or amd64.

EDIT:

The caveat is that Process.StartInfo.EnvironmentVariables always returns the environment of the current process, no matter which process you execute it on.

With Windows itself (and PowerShell) now supported on more architectures, like ARM64, it might not always be enough to check whether the application is 64-bit.

[Environment]::Is64BitProcess will also return True on Windows running on ARM64, so you cannot rely on it if what you really need to know is whether you're running on AMD64. To do this, on Windows you can use the following environment variable:

$Env:PROCESSOR_ARCHITECTURE, which returns values like AMD64, Arm64, or x86.

Switch([IntPtr]::size * 8) {

32 { <#your 32 bit stuff#> ;break }

64 { <#your 64 bit stuff#> ;break }

}