In PowerShell, how do I test whether or not a specific variable exists in global scope?

Question

I\'m using PowerShell scripts for some UI automation of a WPF application. Normally, the scripts are run as a group, based on the value of a global variable. It\'s a littl

Answer 1

EDIT: Use stej's answer below. My own (partially incorrect) one is still reproduced here for reference:

---

You can use

Get-Variable foo -Scope Global

and trap the error that is raised when the variable doesn't exist.

Answer 2

Simple: [boolean](get-variable "Varname" -ErrorAction SilentlyContinue)

Answer 3

There's an even easier way:

if ($variable)
{
    Write-Host "bar exist"
}
else
{
    Write-Host "bar does not exists"
}

Answer 4

You can assign a variable to the return value of Get-Variable then check to see if it is null:

$variable = Get-Variable -Name foo -Scope Global -ErrorAction SilentlyContinue

if ($variable -eq $null)
{
    Write-Host "foo does not exist"
}

# else...

Just be aware that the variable has to be assigned to something for it to "exist". For example:

$global:foo = $null

$variable = Get-Variable -Name foo -Scope Global -ErrorAction SilentlyContinue

if ($variable -eq $null)
{
    Write-Host "foo does not exist"
}
else
{
    Write-Host "foo exists"
}

$global:bar

$variable = Get-Variable -Name bar -Scope Global -ErrorAction SilentlyContinue

if ($variable -eq $null)
{
    Write-Host "bar does not exist"
}
else
{
    Write-Host "bar exists"
}

Output:

foo exists
bar does not exist

Answer 5

Test the existence of variavle MyVariable. Returns boolean true or false.

 Test-Path variable:\MyVariable

Answer 6

Test-Path can be used with a special syntax:

Test-Path variable:global:foo

This also works for environment variables ($env:foo):

Test-Path env:foo

And for non-global variables (just $foo inline):

Test-Path variable:foo