PowerShell to Search Hash Table Values with -notlike or -notmatch

Question

I'm attempting to search a hash table for keys that have values that are -notlike or -notmatch 'Snagit'. I am able find an exact match with -notcontains.

Data Example:

Name    Value
Host1   FireFox,Snagit 7,Chrome
Host2   Internet,Chrome
Host3   Snagit 5,Internet,Stuff

Code Example:

$global:Csv = Import-Csv -LiteralPath $global:ConvertedSNWReport

$global:hash = @{}
Import-Csv -LiteralPath $global:ConvertedSNWReport | ForEach-Object {
    $global:hash[$_.'Computer name'] += @($_.Application)
}

$global:Results = $hash.GetEnumerator() | Where-Object {
    $_.Value -notmatch '*Snagit*' 
}

So, in the example you'd want to grab only the Host2 entry, is that correctly understood? — Mathias R. Jessen
– Mathias R. Jessen, Commented Aug 30, 2017 at 20:43
Note that *Snagit* is not a valid regular expression (-match, -notmatch). It's a pattern for wildcard matches (-like, -notlike). For a regular expression you don't need to match leading or trailing text, since they aren't anchored by default (you need ^ and/or $ for anchoring them), whereas wildcard patterns are by default anchored at beginning and end of a string. — Ansgar Wiechers
– Ansgar Wiechers, Commented Aug 30, 2017 at 21:10

Ansgar Wiechers · Accepted Answer · 2017-08-30 21:05:05Z

3

You can nest your Where-Object statements to accomplish this:

$results = $hash.GetEnumerator() |Where-Object {
    -not($_.Value |Where-Object {$_ -like '*snagit*'})
}

If any of the items in the individual value array matches snagit, the expression will evaluate to $false and the hashtable entrt will be skipped. Conversely, if no items match snagit, it will evaluate to $true

As Ansgar just reminded me, the nested Where-Object statement isn't actually necessary when evaluating strings, since -like doubles as a filter operator on collections:

$results = $hash.GetEnumerator() |Where-Object {
    -not($_.Value -like '*snagit*')
}

edited Aug 30, 2017 at 21:05

Ansgar Wiechers

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answered Aug 30, 2017 at 20:52

Mathias R. Jessen

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5 Comments

Ansgar Wiechers Over a year ago

Darn, beat me to it. You don't need the nested Where-Object, though, -not ($_.Value -like '*snagit*') should be sufficient.

Ansgar Wiechers Over a year ago

To add some explanation, you cannot use -notlike or -notmatch here, because that would filter only matching elements from the values. Unless all array elements match the pattern you'll still end up with a non-empty array, which evaluates to $true. Instead you need to check if any element of the array matches, and then negate that condition to get "no element matches".

Mathias R. Jessen Over a year ago

@AnsgarWiechers thanks, completely forgot that we're working on bare strings here, I need some sleep ^_^

MrMr Over a year ago

While both of these options worked, for some reason it looks like I received slightly different results. I end up sorting and then exporting to csv and they're different sizes. e.g. The nested where has more results

MrMr Over a year ago

It turns out there were incorrect results within the nest where clause.

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