PowerShell String Array Pattern Matching

Question

I have a PowerShell query.

I have the below 2 string arrays. What I want to be able to do is to return only those entries from $RecycleBinPaths that do not begin with all the entries from $ExcludeRecycleBinsPathWildCards (i.e. Wildcard pattern match)

$RecycleBinPaths = @('C:\$Recycle.Bin','D:\$RECYCLE.BIN','E:\$RECYCLE.BIN','F:\$RECYCLE.BIN','L:\$RECYCLE.BIN','M:\$RECYCLE.BIN','S:\$RECYCLE.BIN','T:\$RECYCLE.BIN')

$ExcludeRecycleBinsPathWildCards = @('C:\','F:\')

In the above example I want the output to be:

D:\$RECYCLE.BIN
E:\$RECYCLE.BIN
L:\$RECYCLE.BIN
M:\$RECYCLE.BIN
S:\$RECYCLE.BIN
T:\$RECYCLE.BIN

In fact $ExcludeRecycleBinsPathWildCards array above can contain any number of entries, not necessarily just 2 as shown above.

Are you able to help? Thanks.

Mathias R. Jessen · Accepted Answer · 2021-04-19 12:51:50Z

2

Use nested .Where() methods:

$RecycleBinPaths.Where({
  # Save path to separate variable
  $path = $_
  # Now test if _any_ string in the list of wildcards match, and then apply -not - making it resolve to true only if _none_ of the wildcards match the path
  -not $ExcludeRecycleBinsPathWildCards.Where({ $path -like "$_*" }, 'First')
})

edited Apr 19, 2021 at 12:51

answered Apr 19, 2021 at 12:39

Mathias R. Jessen

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5 Comments

Steve Over a year ago

Wow. You just blew my mind though I still haven't understood what your code is doing, Thanks for your help. have a nice day.

Mathias R. Jessen Over a year ago

@Steve You're welcome! I've added some inline comments to help explain better. If this answer solves your problem, please consider marking it accepted by clicking the checkmark on the left :)

Steve Over a year ago

Does this .Where method exist on PowerShell 3 for arrays/collections? If not, is there a workaround for PS3? We have a mixture of PS version in the estate including 3

Mathias R. Jessen Over a year ago

@Steve I think it was introduced in 4.0, if memory serves me right, but I can't remember clearly - for earlier versions you can achieve the same with the Where-Object cmdlet

Steve Over a year ago

Thank you. You have taught me something new today. I never knew Where-Object could do more than just simple comparison :-) $RecycleBinPaths | Where-Object {$path = $_; -not ($ExcludeRecycleBinsPathWildCards | Where-Object {$path -like "$_*" })}

Venkataraman R · Accepted Answer · 2021-04-19 13:07:21Z

0

Another way of looping through the items and adding to another array.

$RecycleBinPaths = @('C:\$Recycle.Bin','D:\$RECYCLE.BIN','E:\$RECYCLE.BIN','F:\$RECYCLE.BIN','L:\$RECYCLE.BIN','M:\$RECYCLE.BIN','S:\$RECYCLE.BIN','T:\$RECYCLE.BIN')

$ExcludeRecycleBinsPathWildCards = @('C:\','F:\')

$SelectedRecycleBinPaths = @()

foreach($rbp in $RecycleBinPaths)
{

    if(-Not ($ExcludeRecycleBinsPathWildCards -contains $rbp.ToString().Substring(0,3)))
    {
        $SelectedRecycleBinPaths += $rbp
    }

} 

$SelectedRecycleBinPaths

D:\$RECYCLE.BIN
E:\$RECYCLE.BIN
L:\$RECYCLE.BIN
M:\$RECYCLE.BIN
S:\$RECYCLE.BIN
T:\$RECYCLE.BIN

answered Apr 19, 2021 at 13:07

Venkataraman R

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1 Comment

Steve Over a year ago

Thanks but your solution above assumes each of the $ExcludeRecycleBinsPathWildCards entries is exactly 3 characters long? What if it was arbitrary length?

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