How to handle $null in the pipeline

Question

I often have the following situation in my PowerShell code: I have a function or property that returns a collection of objects, or $null. If you push the results in

Answer 1

I don't think anyone likes the fact that both "foreach ($a in $null) {}" and "$null | foreach-object{}" iterate once. Unfortunately there is no other way to do it than the ways you have demonstrated. You could be pithier:

$null | ?{$_} | % { ... }

the ?{$_} is shorthand for where-object {$_ -ne $null} as $null evaluated as a boolean expression will be treated as $false

I have a filter defined in my profile like this:

filter Skip-Null { $_|?{ $_ } }

Usage:

$null | skip-null | foreach { ... }

A filter is the same as a function except the default block is process {} not end {}.

UPDATE: As of PowerShell 3.0, $null is no longer iterable as a collection. Yay!

-Oisin