Output variable name to user

Question

When a parameter is not supplied to my script, I want to include the parameter/variable name as a string in the Write-Error message:

$RequiredArgs = @($Arg1, $Arg2, $Arg3, $Arg4)

foreach ($Arg in $RequiredArgs) {
    if (!($Arg)) {
        Write-Error "Argument: $Arg is required."
        throw
    }
}

This currently outputs Argument: is required.. I have tried quoting the variable name:

Write-Error "Argument: "$Arg" is required."

But this shows the error: Write-Error: A positional parameter cannot be found that accepts argument ' is required.

Is there a way to output the variable name, even if the parameter is not set?

score 2 · Answer 1 · answered Feb 28 '18 at 12:46

2

Yes, use single quotes:

Write-Error 'Argument: "$Arg" is required.'

Consider to use the Mandatory parameter attribute to specify required paramter in your script:

Param
(
    [Parameter(Mandatory=$true)]
    $Arg1
)

Write-Host "Hello $Arg1"

Now if you try to execute the script and omit the parameter you will get prompted for them:

answered Feb 28 '18 at 12:46

Martin Brandl

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This outputs: `Argument: "$Arg" is required.` When: `Argument: "$Arg2" is required` or `$Arg3`, `$Arg4` is expected? – Jelphy Feb 28 '18 at 13:52

score 0 · Answer 2 · answered Feb 28 '18 at 12:57

Apart from what Martin has already mentioned you can do this -

$RequiredArgs = @($Arg1, $Arg2, $Arg3, $Arg4)

foreach ($Arg in $RequiredArgs) {
    if (!($Arg)) {
        Write-Error "Argument: $($Arg) is required."
        throw
    }
}

The $($Arg) syntax helps with evaluating the expression inside $Arg. See this SO link for details.

Output variable name to user

2 Answers2