131

I have a script to which I pass server name(s) in $args.

This way I can do stuff to this (these) server(s) using foreach:

.\script.ps1 host1 host2 host3

foreach ($i in $args)
{
    Do-Stuff $i
}

I'd like to add a named optional parameter called vlan. I've tried:

Param(
    [string]$vlan
)

foreach ($i in $args)
{
    Write-Host $i
}
Write-Host $vlan

It works if you pass a -vlan parameter but if you don't then the script auto assigns the last server name to $vlan.

So, how can you pass single or multiple parameters plus an optional named parameter to a PowerShell script?

Ideally, here are valid examples:

.\script.ps1 host1
.\script.ps1 host1 host2 host3
.\script.ps1 host1 host2 -vlan office
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5 Answers 5

Reset to default
237

The easiest way is probably to use two parameters: One for hosts (can be an array), and one for vlan.

param([String[]] $Hosts, [String] $VLAN)

Instead of

foreach ($i in $args)

you can use

foreach ($hostName in $Hosts)

If there is only one host, the foreach loop will iterate only once. To pass multiple hosts to the script, pass it as an array:

myScript.ps1 -Hosts host1,host2,host3 -VLAN 2

...or something similar.

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3 Comments

thanks for including the info on how to call the script - I'm often missing little pieces like that in powershell.
If you are executing outside a powershell (in wsl for example), then you need to use the -Command flag and to quote the variable. pwsh -Command myScript.ps1 -Hosts "host1,host2,host3" -VLAN 2
@miah Nice one. I'd adjust your command a little bit like pwsh -Command .\myScript.ps1 -Hosts "host1,host2,host3" -VLAN 2
39

One way to do it would be like this:

 param(
       [Parameter(Position=0)][String]$Vlan,
       [Parameter(ValueFromRemainingArguments=$true)][String[]]$Hosts
    ) ...

This would allow multiple hosts to be entered with spaces.

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6 Comments

Really nice! Except your example is missing a ']' to close the second Parameter attribute.
This one should be the best answer.
This is the way.
I don't see how this allows vlan to be optional.
@Tony all parameters are optional by default. You can add the line [Parameter(Mandatory=$false)] before [string]$vlan if you want for readability. But it won't change functionality.
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31

Parameters take input before arguments. What you should do instead is add a parameter that accepts an array, and make it the first position parameter. ex:

param(
    [Parameter(Position = 0)]
    [string[]]$Hosts,
    [string]$VLAN
    )

foreach ($i in $Hosts)  
{ 
    Do-Stuff $i
}

Then call it like:

.\script.ps1 host1, host2, host3 -VLAN 2

Notice the comma between the values. This collects them in an array

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Comments

1

I was having issues doing this in my yml file and then I found this link and adding "-Command" to the front of my script solved it:

https://michlstechblog.info/blog/powershell-passing-an-array-to-a-script-at-command-line/

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Comments

-8

I call a scheduled script who must connect to a list of Server this way:

Powershell.exe -File "YourScriptPath" "Par1,Par2,Par3"

Then inside the script:

param($list_of_servers)
...
Connect-Viserver $list_of_servers.split(",")

The split operator returns an array of string

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2 Comments

This is a horrible way to do it. You should be making $list_of_servers an array: [string[]]$list_of_servers
Thank you, never realized it was so scary. That works from many years.

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