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I'm using an array variable in PowerShell 2.0. If it does not have a value, it will be $null, which I can test for successfully:
PS C:\> [array]$foo = $null PS C:\> $foo -eq $null True But when I give it a value, the test for $null does not return anything:
PS C:\> [array]$foo = @("bar") PS C:\> $foo -eq $null PS C:\> How can "-eq $null" give no results? It's either $null or it's not.
What is the correct way to determine if an array is populated vs. $null?
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$null is an automatic variable in PowerShell used to represent NULL. You can assign it to variables, use it in comparisons and use it as a place holder for NULL in a collection. PowerShell treats $null as an object with a value of NULL. This is different than what you may expect if you come from another language.
To check if all of the values in an array are equal to null , use the every() method to iterate over the array and compare each value to null , e.g. arr. every(value => value === null) . The every method will return true if all values in the array are equal to null .
Type-check with the -is operator returns false for any null value. In most cases, if not all, $value -is [System. Object] will be true for any possible non-null value.
It's an array, so you're looking for Count to test for contents.
I'd recommend
$foo.count -gt 0 The "why" of this is related to how PSH handles comparison of collection objects
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