How to use a PowerShell variable as command parameter?

Question

I'm trying to use a variable as a command's parameter but can't quite figure it out. Let's say MyCommand will accept two parameters: option1 and option2 and they accept boolean values. How would I use $newVar to substitute option 1 or 2? For example:

$newVar = "option1"
MyCommand -$newVar:$true

I keep getting something along the lines of 'A positional parameter cannot be found that accepts argument '-System.String option1'.

More Specifically:
Here, the CSV file is an output of a different policy. The loop goes through each property in the file and sets that value in my policy asdf; so -$_.name:$_.value should substitute as -AllowBluetooth:true.

Import-Csv $file | foreach-object {
    $_.psobject.properties | where-object {
    # for testing I'm limiting this to 'AllowBluetooth' option
    if($_.name -eq "AllowBluetooth"){
    Set-ActiveSyncMailboxPolicy -Identity "asdf" -$_.name:$_.value
    }}
}

You mean newVar but wrongly put in myVar?

manojlds
– manojlds

2011-05-10 21:49:07 +00:00
Commented May 10, 2011 at 21:49 — manojlds
– manojlds, Commented May 10, 2011 at 21:49

Gary · Accepted Answer · 2011-05-11 15:43:16Z

35

Typically to use a variable to populate cmdlet parameters, you'd use a hash table variable, and splat it, using @

 $newVar = @{option1 = $true}
 mycommand @newVar

Added example:

$AS_policy1 = @{
Identity = "asdf"
AllowBluetooth = $true
}

Set-ActiveSyncMailboxPolicy @AS_policy1

edited May 11, 2011 at 15:43

Gary

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answered May 10, 2011 at 22:11

mjolinor

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3 Comments

Gary Over a year ago

Thanks for the help, but that returns an error "A positional parameter cannot be found that accepts argument 'System.Collections.Hashtable'. Specifically I have a loop to get properties properties from a Csv and run them into Set-ActiveSyncMailboxPolicy. For a specific instance I'll say $_.name = "AllowBluetooth" and $_.value = $true (I wrote these variables out to confirm correct values. However, I can't quite put it all together Set-ActiveSyncMailboxPolicy -Identity "asdf" @{$_.name = $_.value} or -$_.name:$_.value. It takes $_.value just fine though.

mjolinor Over a year ago

See edit. If you splat the parameters, you should include all of them in the hashtable.

pgr Over a year ago

If anyone is trying to use this answer and the example is not working for you, maybe you're doing the same mistake I did, for lack of attention: using the variable in the usual way writing $AS_policy1 when I should be writing @AS_policy1 with a "splatting" ampersand.

manojlds · Accepted Answer · 2011-05-10 21:59:43Z

7

See if this works for you:

 iex "MyCommand -$($newVar):$true"

answered May 10, 2011 at 21:59

manojlds

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3 Comments

Gary Over a year ago

Thanks manojlds, this got me a little closer. Literally, $newVar is $_.name and $true is $_.value (which equals "Allow"). The way I was doing it, it accepted $_.value for the value but not $_.name as a parameter. Using your method accepts $_.name as my parameter but not $_.value as the value... Saying cannot convert value "System.String" to type [type]. I'll keep trying other things though.

Gary Over a year ago

I got your method to work when -$($newVar) wants a string, but it fails on boolean values because it thinks it's a string. I believe it's because the whole command is in quotes. Any pointers?

Emiliano Poggi Over a year ago

@Fantabulum: iex "MyCommand -$($_.name):$($_.value)" should work then, for the reason I've explained in my answer. +1 @manojlds.

residuum · Accepted Answer · 2017-06-07 20:45:05Z

5

I had the same Problem and just found out how to resolve it. Solution is to use invoke-Expression: invoke-Expression $mycmd This uses the $mycmd-string, replaces variables and executes it as cmdlet with given parameters

answered Jun 7, 2017 at 20:45

residuum

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Comments

Fernando Fabreti · Accepted Answer · 2022-03-28 14:32:20Z

4

Nowadays, If you don't mind evaluating strings as commands, you may use Invoke-Expression:

$mycmd = "MyCommand -$($newVar):$true"
Invoke-Expression $mycmd

answered Mar 28, 2022 at 14:32

Fernando Fabreti

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Comments

Emiliano Poggi · Accepted Answer · 2011-05-11 14:18:40Z

1

I would try with:

$mycmd = "MyCommand -$($newVar):$true"
& $mycmd

result

Can't work because the ampersand operator just execute single commands without prameters, or script blocks.

edited May 11, 2011 at 14:18

answered May 10, 2011 at 22:02

Emiliano Poggi

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1 Comment

Gary Over a year ago

Thanks for the suggestion empo, but this seems to behave the same way as my original. I can post an excerpt of my actual script if that would help, but it involves several loops and Exchange commands so I think it would just cause confusion.

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