How do I check if a PowerShell module is installed?

Question

You can use the ListAvailable option of Get-Module:

if (Get-Module -ListAvailable -Name SomeModule) {
    Write-Host "Module exists"
} 
else {
    Write-Host "Module does not exist"
}

The ListAvailable option doesn't work for me. Instead this does:

if (-not (Get-Module -Name "<moduleNameHere>")) {
    # module is not loaded
}

Or, to be more succinct:

if (!(Get-Module "<moduleNameHere>")) {
    # module is not loaded
}

A module could be in the following states:

• imported
• available on disk (or local network)
• available in an online gallery

If you just want to have the darn thing available in a PowerShell session for use, here is a function that will do that or exit out if it cannot get it done:

function Load-Module ($m) {

    # If module is imported say that and do nothing
    if (Get-Module | Where-Object {$_.Name -eq $m}) {
        write-host "Module $m is already imported."
    }
    else {

        # If module is not imported, but available on disk then import
        if (Get-Module -ListAvailable | Where-Object {$_.Name -eq $m}) {
            Import-Module $m -Verbose
        }
        else {

            # If module is not imported, not available on disk, but is in online gallery then install and import
            if (Find-Module -Name $m | Where-Object {$_.Name -eq $m}) {
                Install-Module -Name $m -Force -Verbose -Scope CurrentUser
                Import-Module $m -Verbose
            }
            else {

                # If the module is not imported, not available and not in the online gallery then abort
                write-host "Module $m not imported, not available and not in an online gallery, exiting."
                EXIT 1
            }
        }
    }
}

Load-Module "ModuleName" # Use "PoshRSJob" to test it out

The current version of Powershell has a Get-InstalledModule function that suits this purpose well (or at least it did in my case).

Get-InstalledModule

Description

The Get-InstalledModule cmdlet gets PowerShell modules that are installed on a computer.

The only issue with it is that it throws an exception if the module that is being requested doesn't exist, so we need to set ErrorAction appropriately to suppress that case.

if ((Get-InstalledModule `
    -Name "AzureRm.Profile" `
    -MinimumVersion 5.0 ` # Optionally specify minimum version to have
    -ErrorAction SilentlyContinue) -eq $null) {

    # Install it...
}

You can use the Get-InstalledModule

If (-not(Get-InstalledModule SomeModule -ErrorAction silentlycontinue)) {
  Write-Host "Module does not exist"
}
Else {
  Write-Host "Module exists"
}

When I use non-default modules in my scripts I call the function below. Besides the module name, you can provide a minimum version.

# See https://www.powershellgallery.com/ for module and version info
Function Install-ModuleIfNotInstalled(
    [string] [Parameter(Mandatory = $true)] $moduleName,
    [string] $minimalVersion
) {
    $module = Get-Module -Name $moduleName -ListAvailable |`
        Where-Object { $null -eq $minimalVersion -or $minimalVersion -lt $_.Version } |`
        Select-Object -Last 1
    if ($null -ne $module) {
         Write-Verbose ('Module {0} (v{1}) is available.' -f $moduleName, $module.Version)
    }
    else {
        Import-Module -Name 'PowershellGet'
        $installedModule = Get-InstalledModule -Name $moduleName -ErrorAction SilentlyContinue
        if ($null -ne $installedModule) {
            Write-Verbose ('Module [{0}] (v {1}) is installed.' -f $moduleName, $installedModule.Version)
        }
        if ($null -eq $installedModule -or ($null -ne $minimalVersion -and $installedModule.Version -lt $minimalVersion)) {
            Write-Verbose ('Module {0} min.vers {1}: not installed; check if nuget v2.8.5.201 or later is installed.' -f $moduleName, $minimalVersion)
            #First check if package provider NuGet is installed. Incase an older version is installed the required version is installed explicitly
            if ((Get-PackageProvider -Name NuGet -Force).Version -lt '2.8.5.201') {
                Write-Warning ('Module {0} min.vers {1}: Install nuget!' -f $moduleName, $minimalVersion)
                Install-PackageProvider -Name NuGet -MinimumVersion 2.8.5.201 -Scope CurrentUser -Force
            }        
            $optionalArgs = New-Object -TypeName Hashtable
            if ($null -ne $minimalVersion) {
                $optionalArgs['RequiredVersion'] = $minimalVersion
            }  
            Write-Warning ('Install module {0} (version [{1}]) within scope of the current user.' -f $moduleName, $minimalVersion)
            Install-Module -Name $moduleName @optionalArgs -Scope CurrentUser -Force -Verbose
        } 
    }
}

usage example:

Install-ModuleIfNotInstalled 'CosmosDB' '2.1.3.528'

Please let me known if it's useful (or not)