PowerShell: Filtering an array by another [filter] array if any part of the text matches.

Question

Okay, I'm still fairly new to PowerShell.

I've written a piece of code that works, but it smells entirely wrong. What is the right way to write this from a PowerShell standpoint?

$filters = @("*a*","*b*")
$data = @("c/a","c/b","c/a/d","e","a","e/f")
$desiredResults = @("e","e/f")

Write-Host "Filters" -ForegroundColor Yellow
$filters 
Write-Host "Data" -ForegroundColor Yellow
$data

$results = @()

foreach ($d in $data)
{
    [bool] $skip = $false
    foreach ($filter in $filters)
    {
        if ($d -like $filter)
        {
            $skip = $true
        }
    }

    if ($skip -eq $false)
    {
        $results += $d
    }
}

Write-Host "Desired Results" -ForegroundColor Yellow
$desiredResults
Write-Host "Results" -ForegroundColor Yellow
$results

Chandan Rai · Accepted Answer · 2017-01-12 17:37:45Z

6

you can do like this

$filters = @("a","b")
$data = @("c/a","c/b","c/a/d","e","a","e/f")
$desiredResults = @("e","e/f")

$data | Select-String -Pattern $filters -NotMatch

answered Jan 12, 2017 at 17:37

Chandan Rai

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2 Comments

Esperento57 Over a year ago

i like this solution, gj!

Jason V Over a year ago

Exactly what I needed for this issue. Clean and easy to read.

TheMadTechnician · Accepted Answer · 2017-01-12 17:26:38Z

2

The right way? I don't know that there is a right way. I can give you what I consider a better way using RegEx:

$filters = @("a","b")
$data = @("c/a","c/b","c/a/d","e","a","e/f")
$desiredResults = @("e","e/f")

$RegExFilter = ($Filters|%{[regex]::escape($_)}) -join '|'

$Results = $data | Where{$_ -notmatch $RegExFilter}

Write-Host "Desired Results" -ForegroundColor Yellow
$desiredResults
Write-Host "Results" -ForegroundColor Yellow
$results

This basically takes each element of the $filters array, performs a regex escape on it to escape any special characters, and then joins all of those results with a pipe character. So in the example given $RegExFilter equals a|b. Then it filters $data against anything that matches that pattern.

answered Jan 12, 2017 at 17:26

TheMadTechnician

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1 Comment

Jason V Over a year ago

I like this one as well. The reusable aspect is awesome. I have to go with the Select-String option though just because it is easier to read at a glance. Definitely going to save this snippet as well.

Paul · Accepted Answer · 2021-02-11 20:43:33Z

1

I frequently have problems with double pipelines so I switch one to ForEach.
Here is a one-liner.

$filters = @("*a*","*b*")
$data = @("c/a","c/b","c/a/d","e","a","e/f")

ForEach ($Item in $data) { If ( !($filters | Where-Object {$Item -like $_})) { $Item } }

answered Feb 11, 2021 at 20:43

Paul

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Comments

4c74356b41 · Accepted Answer · 2017-01-12 17:20:06Z

0

The only real problem here - is you have to compare string to and array of strings, which I don't think powershell can do elegantly (but I might be wrong), so I've done this:

foreach ($d in $data)
{
    if ($d -notlike $filters[0] -and $d -notlike $filters[1])
    {
        $results += $d
    }
}

I assume the syntaxis is clean enough and doesn't need any explanation. if it needs explanation, tell me in comments.

answered Jan 12, 2017 at 17:20

4c74356b41

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Comments

Esperento57 · Accepted Answer · 2017-01-12 18:42:44Z

0

try this

$data | %{$val=$_; $Nb=($filters | where {$val -like $_}).Count ; if ($Nb -eq 0) {$val} }

answered Jan 12, 2017 at 18:42

Esperento57

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2 Comments

Jason V Over a year ago

This one doesn't match my expected results. It only filters out one value ("a").

Esperento57 Over a year ago

Strange it work on my pc. What is your PowerShell version?

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