How to check if a cmdlet exists in PowerShell at runtime via script

Question

I have a PowerShell script that needs to run under multiple hosts (PowerGUI, PowerShell ISE, etc...), but I am having an issue where sometimes a cmdlet doesn't exist under one of the hosts. Is there a way to check to see if a cmdlet exists so that I can wrap the code in an if block and do something else when it does not exist?

I know I could use the $host.name to section the code that is suppose to run on each host, but I would prefer to use Feature Detection instead in case the cmdlet ever gets added in the future.

I also could use a try/catch block, but since it runs in managed code I assume there is away to detect if a cmdlet is installed via code.

Keith Hill · Accepted Answer · 2010-10-13 05:10:47Z

169

Use the Get-Command cmdlet to test for the existence of a cmdlet:

if (Get-Command $cmdName -errorAction SilentlyContinue)
{
    "$cmdName exists"
}

And if you want to ensure it is a cmdlet (and not an exe or function or script) use the -CommandType parameter e.g -CommandType Cmdlet

edited Oct 13, 2010 at 5:10

answered Oct 12, 2010 at 23:54

Keith Hill

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5 Comments

Greg Bray Over a year ago

Didn't know there was an errorAction parameter. Found the list of all Common Parameters here: msdn.microsoft.com/en-us/library/dd901844(VS.85).aspx which is good to know. Thanks!

Greg Bray Over a year ago

NOTE: you can also check for Modules using if (get-module | Where-Object {$_.Name -eq "ServerManager"}) { "Module Exists" }. More details: stackoverflow.com/questions/10027156/…

Victor Zakharov Over a year ago

cmdlet may exist, but not be available. Good example: Get-WinEvent exists on Windows 2003, but it throws NotImplemented exception. How would you handle this situation?

Keith Hill Over a year ago

I'm not sure there is an easy way to handle this for an arbitrary cmdlet. If you're only testing Get-WinEvent, you would know appropriate parameters to pass and wrap with a try/catch. I don't think that's feasible for an arbitrary cmdlet. That said, I think it is a corner-case for a cmdlet to throw a NotImplementedException- at least I hope so. :-(

user4317867 Over a year ago

@Neolisk can't you try $test = Get-WinEvent -LogName system -MaxEvents 1; [bool]$test and if it returns False then the cmdlet is not available?

Peter Mortensen · Accepted Answer · 2015-09-24 21:06:11Z

36

This is a simple function to do what you're like to do :)

function Check-Command($cmdname)
{
    return [bool](Get-Command -Name $cmdname -ErrorAction SilentlyContinue)
}

How to use (for example):

if (Check-Command -cmdname 'Invoke-WebRequest')
{
     Invoke-WebRequest $link -OutFile $destination
}
else
{
     $webclient.DownloadFile($link, $destination)
}

edited Sep 24, 2015 at 21:06

Peter Mortensen

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answered Apr 2, 2015 at 23:37

Alexander Schüßler

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Comments

ernestasju · Accepted Answer · 2020-11-09 10:51:47Z

7

If the command is in Verb-Noun form then you can use Get-Command with Verb and Noun parameters.

# Usage:
if (Get-Command -Verb Invoke -Noun MyCommand) {
  # cmdlet Invoke-MyCommand exists
}

Get-Command -Verb Get -Noun Item

# Output:
# CommandType     Name                  Version    Source
# -----------     ----                  -------    ------
# Cmdlet          Get-Item              7.0.0.0    #Microsoft.PowerShell.Management

Get-Command -Verb Take -Noun One

# No output.

function Take-One { [CmdletBinding()]param() }
Get-Command -Verb Take -Noun One

# Output:
# CommandType     Name                   Version    Source
# -----------     ----                   -------    ------
# Function        Take-One

Tested on Windows PowerShell 5.1 and PowerShell Core 7.0.

Edit 2020-11-09 Additional example. Also usage example (adapted from Keith Hill answer).

edited Nov 9, 2020 at 10:51

answered Nov 9, 2020 at 10:26

ernestasju

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2 Comments

ernestasju Over a year ago

I know this question is very old. Just a memo for my future self.

alx9r Nov 27, 2024 at 15:23

This is the appropriate answer where errors will confound an operation even with -ErrorAction SilentlyContinue like in, for example, the Start-Job -InitializationScript scriptblock.

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