Searching Hash Table Values for Missing Values

Question

I'm attempting to search a hash table that contains a hostname as the key and applications as the values. I'm looking for hostnames (keys) that do NOT contain a specific value AKA application. However, my code does not appear to work as I always receive all of the keys/hostnames back.

foreach ($global:computer in $global:hash.keys){  
  if ($global:hash.$global:computer.values -notcontains 'SnagIt'){
    $global:computer
}

}

Example Data:

Key, Values

Host1:FireFox,Chrome,IE

Host2:Snagit,FireFox,Chrome,IE

Host3:Chrome,IE

Example Value Output from $global:hash.$global:computer:

{Snagit, FireFox, Chrome, IE...}

Hash Table Build Code:

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

[HashTable]$global:Hash=@{}

For ($i = 0; $i -lt ($global:Csv."Computer name").Count; $i++)
{
If ($global:Hash.ContainsKey($global:Csv[$i].'Computer name'))
{
    $global:Hash.($global:Csv[$i].'Computer name').Application += $global:Csv[$i].Application
    Continue
}
$global:Hash.($global:Csv[$i].'Computer name') = @{
  Application = @($global:Csv[$i].Application)
}
}

I don't think your hashtable looks like you think it does. The index operator ([]) belongs after the list variable, not after the property, e.g. $global:Csv[$i].'Computer name'. — Ansgar Wiechers
– Ansgar Wiechers, Commented Aug 30, 2017 at 17:38
I changed it and it didn't seem to make a difference, as far as I could tell. — MrMr
– MrMr, Commented Aug 30, 2017 at 17:45
Ah, I see. You need to use $Hash.Computer.Application to get the array of programs for that PC. — Maximilian Burszley
– Maximilian Burszley, Commented Aug 30, 2017 at 18:26

Ansgar Wiechers · Accepted Answer · 2017-08-30 18:48:06Z

1

Your hashtable creation builds the application lists as nested hashtables:

{
    "Host1": {
        "Application": [ "FireFox", "Chrome", "IE" ]
    },
    "Host2": {
        "Application": [ "Snagit", "FireFox", "Chrome", "IE" ]
    },
    "Host3": {
        "Application": [ "Chrome", "IE" ]
    }
}

Import your data like this:

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

to get a direct mapping between hostname and list of applications:

{
    "Host1": [ "FireFox", "Chrome", "IE" ],
    "Host2": [ "Snagit", "FireFox", "Chrome", "IE" ],
    "Host3": [ "Chrome", "IE" ]
}

With that you can filter the hashtable like this:

$hash.GetEnumerator() | Where-Object {
    $_.Value -notcontains 'Snagit'
}

If you want to stick with your data import procedure (which I do not recommend) you need to expand the Application key of the hashtable values:

$hash.GetEnumerator() | Where-Object {
    $_.Value.Application -notcontains 'Snagit'
}

As a side note: avoid using global variables whenever you can. They're usually a side channel that introduces unexpected state in your scripts. Particularly do not use global variables as loop variables. In most cases it's better to use local variables and pass data from a caller via script/function parameters.

edited Aug 30, 2017 at 18:48

answered Aug 30, 2017 at 17:21

Ansgar Wiechers

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4 Comments

Ansgar Wiechers Over a year ago

"Doesn't work" is an insufficient problem description. Please update your question with how your hashtable is actually defined, like Mathias already requested.

MrMr Over a year ago

Sorry for the confusion, please see the updated post.

MrMr Over a year ago

Thank you very much for this.

MrMr Over a year ago

Bonus points if you can show how you can do a -notlike or -notmatch 'Snagit'

Mathias R. Jessen · Accepted Answer · 2017-08-30 17:22:42Z

0

The expression $hashtable.$key already resolves to the values of the entry with key $key

Remove the .values reference from $global:hash.$global:computer.values

If the values are just single strings with comma-separated items, -notcontains won't work, use the -notlike operator instead:

if($hash.$computer -notlike '*SnagIt*'){...}

edited Aug 30, 2017 at 17:22

answered Aug 30, 2017 at 17:21

Mathias R. Jessen

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4 Comments

Mathias R. Jessen Over a year ago

@MrMr Updated the answer. Can you perhaps update your answer with how you constructed the hashtable in the first place?

MrMr Over a year ago

the second option you provided didn't work either. I used import-csv to build the hash table.

Ansgar Wiechers Over a year ago

@MrMr Import-Csv produces a list of objects, not a hashtable. Please update your question with a sample of your actual input data and how you read them. Basically, put a minimal reproducible example in your question.

MrMr Over a year ago

I apologize, I used import-csv and then I built a hash table with that data.

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