Strange behavior of PowerShell matching against array string element

Question

I'm quite desperate for tips here. Here's my quandary:

First, I had an array of string, which I created this way (showing a subset of the numbers):

$a = @"
00013120747
00013051436
00013110491
00002100011
"@

$aa = $a.Split("`n")

Next, I generate a list of all users in Active Directory (using ActiveRoles) this way:

$all_u = Get-QADUser -DontUseDefaultIncludedProperties -IncludedProperties Name,LogonName,EmployeeID -SizeLimit 0

Now, why can't I match against an element of the $aa array? For example, doing the following:

$all_u | where {$_.EmployeeID -match "00013110491"}

it works. But if I do the following:

$all_u | where {$_.EmployeeID -match $aa[2]}

it doesn't work.

So I did a simpler test:

$aa.GetType().Name
String[]

$aa[2].GetType().Name
String

$aa[2]
00013110491

$aa[2] -eq "00013110491"
False

What?? What's going on here???

I'm using PowerShell ISE, by the way.

Answer 1

If you examine the elements of $aa carefully, you'll find they all have trailing whitespace. This is a consequence of doing the split on "`n". If you trim them after you do the split, you'll get the expected result.

$a = @"
00013120747
00013051436
00013110491
00002100011
"@

$aa = $a.Split("`n") |% {$_.trim()}

$aa[2] -eq "00013110491"

True

The -match will match anywhere in the string, so it will still match even with the trailing space. The -eq requires and exact match, character for character, and the trailing space will cause it to return False.

Answer 2

$a = @"
00013120747
00013051436
00013110491
00002100011
"@

$aa = $a.Split("`r`n")

Answer 3

You're using a here string. That syntax like this:

$String = @"
entry1
entry2
entry3
"@

$String.Count
 >1

You need to Split your here string first before you can compare them. If you look at what you actually get when you run

 $a[2]
 > '0'

You're asking PowerShell for the 2nd index position. That means this. 00[0]13120747

This is because a here-string is a single string, which that happens to contain multiple lines. With PowerShell array indexing, if there is only one single entry, you'll get back that position from the list.

$string = "0123456"
$string[0..2]
 >012