Powershell - Setting a variable inside a function not setting it globally?

Question

I have the following code:

$firstRun = 'True'

$file | ForEach-Object {

    Function Do-Stuff {
        if ($firstRun = 'True') {

            write-host "null"
            $firstRun = 'False'
        }
    }
Do-Stuff
}

When I call Function 'Do-Stuff', it will run the first time, no matter where I place $firstRun = 'False', it returns true and intiates the if block again. What am I doing wrong?

check out the docs on variable scope. i suspect that is where your glitch is occurring ... — Lee_Dailey
– Lee_Dailey, Commented Jan 20, 2020 at 23:50
kool! [grin] it looks like your problem is related to scope. ///// purely as an aside ... i would replace all your tests for the string true with tests for the boolean $True. it makes no difference in your code, but fits better with how PoSh handles False/True. — Lee_Dailey
– Lee_Dailey, Commented Jan 21, 2020 at 0:35

mklement0 · Accepted Answer · 2020-01-21 03:13:46Z

3

$firstRun = 'True' is setting $firstRun to the String 'True'. If you want to see if it equals that value the comparison operator is -eq, so $firstRun -eq 'True'

For more information on comparison operators run Get-Help about_comparison_operators

Thanks for letting us know about the typo, I'll stick with your example to show how you can prefix your variables with global: so you get the required variable scope.

$firstRun = 'True'
Function Do-Stuff {
    if ($global:firstRun  -eq 'True') {

        Write-Host "True"
        $global:firstRun  = 'False'
    }
    else {
        Write-Host "False"
    }
}

$file | ForEach-Object { Do-Stuff }

For more information on scopes check Get-Help about_scopes.

edited Jan 21, 2020 at 3:13

mklement0

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answered Jan 20, 2020 at 23:37

jfrmilner

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2 Comments

arealhobo Over a year ago

Shoot, that actually a typo in my sample code. Its not like that in my actual code....

arealhobo Over a year ago

Adding $global:fixed the issue I was having

Svyatoslav Pidgorny · Accepted Answer · 2020-01-21 00:14:43Z

2

Use $global:firstRun instead of the $firstRun inside the function to reference variable in the global scope.

answered Jan 21, 2020 at 0:14

Svyatoslav Pidgorny

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Comments

Tobias Meyer · Accepted Answer · 2020-01-21 00:34:14Z

0

Your function doesn't return something.

Here is an example with a returning value.

$value1 = 3
$value2 = 5
function Calculate-Something ($number1,$number2)
{
   $result = $number1 + $number2
   return $result
}
$value3 = Calculate-Something -number1 $value1 -number2 $value2
Write-Host $value3

This code sample would add up value1 and value2 and would write the result:

answered Jan 21, 2020 at 0:34

Tobias Meyer

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