filter Foreach-Object results with multiple conditions in Powershell not working

Question

I'm trying to filter a list of changed files in git using Powershell 7. I want only the file paths that begin with 'packages' or 'database'. When I run the code, the results are not filtered and everything is returned. How would I get the filtering to work? I'm new to Powershell scripting.

Here is my code:

$editedFiles = git diff HEAD [git commit id] --name-only
$editedFiles | ForEach-Object {
    $sepIndex = $_.IndexOf('/')
    if($sepIndex -gt 0 -and ($_ -contains 'packages' -or 'database')) {
        Write-Output $_      
    }
}

Mathias R. Jessen · Accepted Answer · 2020-12-29 18:12:24Z

2

Couple of things to watch out for here:

-contains is a collection containment operator - for strings, you'll want either the -like wildcard comparison operator:

$_ -like "*packages*"

or the -match regex operator:

$_ -match 'package'

The other thing to watch out for here is the -or operator - it only takes boolean operands ($true/$false), and if you pass it anything else, it'll convert the operands to [bool] if necessary.

That means that the following kind of statement:

$(<# any expression, really #>) -or 'non-empty string'

ALWAYS returns $true - because a non-empty string evaluates to $true when converted to [bool].

Instead, you'll want to change two separate comparisons:

$_ -like '*packages*' -or $_ -like '*database*'

Alternatively, you can use the -match operator once, by using an alternation (|):

$_ -match 'package|database'

And end up with something like:

$editedFiles | ForEach-Object {
    $sepIndex = $_.IndexOf('/')
    if($sepIndex -gt 0 -and $_ -match 'package|database') {
        Write-Output $_      
    }
}

If filtering is all you intend to do in the ForEach-Object block, you might as well use Where-Object - it's designed exactly for that :)

$editedFiles | Where-Object {
    $_.IndexOf('/') -gt 0 -and $_ -match 'package|database'
}

answered Dec 29, 2020 at 18:12

Mathias R. Jessen

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1 Comment

mdailey77 Over a year ago

Your Where-Object example is exactly what I'm looking for. Thanks so much.

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