Better way to print object than Write-Host

Question

I use Write-Host analyze objects, but some times it is hard to understand what the object actually is.

Consider:

Write-Host $null
Write-Host @()
Write-Host @($null, $null)

Prints:

# Actually it prints nothing

I would like some thing like this:

Null
@()
@(Null, Null)

Any suggestions?

Answer 1

For this specific example, you can easily get what you want by sticking them in the property of an object. For the sake of an example, lets create an array with your three tests in it:

$tests = @($null,@(), @($null,$null))

function Write-Visible {
   param($InputObject) 

   New-Object PSObject -Property @{ Object=$InputObject } | 
       Out-String | Out-Host 
}

Of course, the Out-String | Out-Host stuff is just to make sure we don't actually output the objects to the pipeline, but behave like Write-Host does.

So now we can run our tests:

PS> Write-Visible $tests[0]

Object
------


PS> Write-Visible $tests[1]

Object
------
{}


PS> Write-Visible $tests[2]

Object
------
{$null, $null}

Of course, the problem with that is that it tends not to work so great for real objects because it's turning them into properties of an object, where they get rendered "ToString()" ... however, off the top of my head, I can't think how to invoke the rendering magic that happens there without the new object.

Answer 2

You can write a function that does the pretty-printing for you. Something like the following might work for your needs:

function pp($a) {
    if ($a -eq $null) {
        return "Null"
    } elseif ($a -is [object[]]) {
        $b = @()
        foreach ($x in $a) {
            $b += (pp $x)
        }
        $s = "@(" + [string]::Join(",", $b) + ")"
        return $s
    } else {
        return $a
    }
}

This has, however still problems with an empty array on the shell (works fine from a .ps1 file, though). Also Hashtables aren't supported, but nested arrays are. Probably still needs some plumbing but might give a general direction.

The @($null, $null) array seems to be an ugly beast, resisting even comparing it to $null. Weird.