Errors passing no value to a string parameter with a default value

Question

I am working from the command line. Let's say my example looks like this:

Param(
  [Parameter()] [string]$greeting="HelloWorld"
)

From the commandline I can do this: mygreeting
And it will output HelloWorld

Or I can do this: mygreeting -greeting="whatever"
And it will output whatever

Why can't I type this?:

mygreeting -greeting

without getting an error that the argument is missing?

In the code I want to be able to basically say:
If greeting is specified but has no value then set the value conditionally based on other things
If greeting is not specified use the default value

What do you mean by "no value"? Like if someone enters mygreeting -greeting ""? If you pass in a flag, I think it requires something — Vivek Chavda
– Vivek Chavda, Commented Jan 6, 2017 at 22:44

Martin Brandl · Accepted Answer · 2017-01-06 22:41:19Z

1

This is by design. In PowerShell you are passing an argument by specifying the name of the parameter followed with the value you want to pass (except if its a switch or you using positional parameters where you only pass the value).

answered Jan 6, 2017 at 22:41

Martin Brandl

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user7377479 · Accepted Answer · 2017-01-07 07:49:42Z

1

you can use this :

function test-test {
    [CmdletBinding()] 
    Param (
    [parameter(Position = 0)]
    [string]$greetings = "hi world"
    )

    $greetings
}

to set value about your parameter and u can call it like this :

test-test "something"

or

test-test -greetings "something"

but you cant run it like parameter="value"

if you want to use this you should use :

test-test ($greetings = "ssss")

like this. but actually this $greetings not the same of variable in your function because have grater oscope than youre function.

answered Jan 7, 2017 at 7:49

user7377479

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