PowerShell equivalent of LINQ Any()?

Question

I would like to find all directories at the top level from the location of the script that are stored in subversion.

In C# it would be something like this

Directory.GetDirectories(".")
  .Where(d=>Directories.GetDirectories(d)
     .Any(x => x == "_svn" || ".svn"));

I'm having a bit of difficulty finding the equivalent of "Any()" in PowerShell, and I don't want to go through the awkwardness of calling the extension method.

So far I've got this:

 Get-ChildItem | ? {$_.PsIsContainer} | Get-ChildItem -force | ? {$_.PsIsContainer -and $_.Name -eq "_svn" -or $_.Name -eq ".svn"

This finds me the svn directories themselves, but not their parent directories - which is what I want. Bonus points if you can tell me why adding

 | Select-Object {$_.Directory}

to the end of that command list simply displays a sequence of blank lines.

Answer 1

An implementation of mklement0's helpful answer turned into a cmdlet, it should be compatible with Windows PowerShell 5.1 and PowerShell 7+ (probably won't work in previous versions).

The main advantage here is that the StopUpstreamCommandsException is stored in a static field, meaning, we only need to get it once per session. This approach is also significantly faster due to the use of a SteppablePipeline to process input objects.

You can either compile it ahead of time or if you want to compile it ad-hoc, put the code in a file, i.e.: TestAny.cs then you can do:

Add-Type (Get-Content path\to\TestAny.cs -Raw) -PassThru |
    Import-Module -Assembly { $_.Assembly }

And the usage would be:

0..1mb | Test-Any { $_ -gt 500 }

The -UseLocalScope means that the scriptblock will be dot-sourced, something similar to how ForEach-Object and Where-Object, however do note there is a performance penalty using this method.

0..1mb | Test-Any { $i = $_; $_ -gt 500 } -UseLocalScope
$i # Outputs: 501

Lastly a performance comparison between this cmdlet and the PowerShell function counterpart:

CODE

using System;
using System.Linq;
using System.Management.Automation;
using System.Management.Automation.Language;

[Cmdlet(VerbsDiagnostic.Test, "Any")]
public sealed class TestAnyCommand : PSCmdlet, IDisposable
{
    private const string _exceptionType =
        "System.Management.Automation.StopUpstreamCommandsException";

    private SteppablePipeline _pipe;

    private static Exception s_exception;

    private Exception StopUpstreamException
    {
        get
        {
            return s_exception ?? (s_exception = GetException());
        }
    }

    [Parameter(ValueFromPipeline = true)]
    public PSObject InputObject { get; set; }

    [Parameter(Mandatory = true, Position = 0)]
    public ScriptBlock Filter { get; set; }

    [Parameter]
    public SwitchParameter UseLocalScope { get; set; }

    protected override void BeginProcessing()
    {
        _pipe = ScriptBlock
            .Create("param($__sb) " + (UseLocalScope ? "." : "&") + " $__sb")
            .GetSteppablePipeline(
                CommandOrigin.Internal,
                new[] { ConvertToProcessBlockIfUnnamed(Filter) });

        _pipe.Begin(true);
    }

    protected override void ProcessRecord()
    {
        if (LanguagePrimitives.ConvertTo<bool>(_pipe.Process(InputObject)))
        {
            WriteObject(true);
            throw StopUpstreamException;
        }
    }

    protected override void EndProcessing()
    {
        WriteObject(false);
        _pipe.End();
    }

    private static ScriptBlock ConvertToProcessBlockIfUnnamed(ScriptBlock scriptBlock)
    {
        ScriptBlockAst sbAst = (ScriptBlockAst)scriptBlock.Ast;

        if (sbAst.BeginBlock != null || sbAst.ProcessBlock != null)
        {
            return scriptBlock;
        }

        ScriptBlockAst newSbAst = new ScriptBlockAst(
            scriptBlock.Ast.Extent,
            paramBlock: null,
            beginBlock: null,
            processBlock: new NamedBlockAst(
                sbAst.EndBlock.Extent,
                TokenKind.Process,
                new StatementBlockAst(
                    sbAst.EndBlock.Extent,
                    sbAst.EndBlock.Statements.Select(s => s.Copy()).Cast<StatementAst>(),
                    null),
                unnamed: false),
            endBlock: null,
            dynamicParamBlock: null);

        return newSbAst.GetScriptBlock();
    }


    private Exception GetException()
    {
        return (Exception)Activator.CreateInstance(
            typeof(Cmdlet).Assembly.GetType(_exceptionType), this);
    }

    public void Dispose()
    {
        _pipe.Dispose();
        GC.SuppressFinalize(this);
    }
}

Answer 2

To answer the immediate question with a PowerShell v3+ solution:

(Get-ChildItem -Force -Directory -Recurse -Depth 2 -Include '_svn', '.svn').Parent.FullName

-Directory limits the matches to directories, -Recurse -Depth 2 recurses up to three levels (children, grandchildren, and great-grandchildren), Include allows specifying multiple (filename-component) filters, and .Parent.FullName returns the full path of the parent dirs. of the matching dirs., using member-access enumeration (implicitly accessing a collection's elements' properties).

^{As for the bonus question: select-object {$_.Directory} does not work, because the [System.IO.DirectoryInfo] instances returned by Get-ChildItem have no .Directory property, only a .Parent property; Select-Object -ExpandProperty Parent should have been used.}

^{In addition to only returning the property value of interest, -ExpandProperty also enforces the existence of the property. By contrast, Select-Object {$_.Directory} returns a custom object with a property literally named $_.Directory, whose value is $null, given that the input objects have no .Directory property; these $null values print as empty lines in the console.}

---

As for the more general question about a PowerShell equivalent to LINQ's .Any() method, which indicates [with a Boolean result] whether a given enumerable (collection) has any elements at all / any elements satisfying a given condition:

Natively, PowerShell offers no such equivalent, but the behavior can be emulated:

---

Using the PowerShell v4+ intrinsic.Where() method:

Caveat: This requires collecting the entire input collection in memory first, which can be problematic with large collections and/or long-running input commands.

(...).Where({ $_ ... }, 'First').Count -gt 0

... represents the command of interest, and $_ ... the condition of interest, applied to each input object, where PowerShell's automatic $_ variable refers to the input object at hand; argument 'First' ensures that the method returns once the first match has been found.

For example:

# See if there's at least one value > 1
PS> (1, 2, 3).Where({ $_ -gt 1 }, 'First').Count -gt 0
True

---

Using the pipeline: Testing whether a command produced at least one output object [matching a condition]:

The advantage of a pipeline-based solution is that it can act on a command's output one by one, as it is being produced, without needing to collect the entire output in memory first.

• If you don't mind that all objects are enumerated - even if you only care if there is at least one - use Paolo Tedesco's helpful extension to JaredPar's helpful answer. The down-side of this approach is that you always have to wait for a (potentially long-running) command to finish producing all output objects, even though - logically - the determination whether there are any output objects can be made as soon as the first object is received.

• If you want to exit the pipeline as soon as one [matching] object has been encountered, you have two options:

  • [Ad-hoc: Easy to understand, but cumbersome to implement] Enclose the pipeline in a dummy loop and use break to break out of the pipeline and that loop (... represents the command whose output to test, and $_ ... match the condition):

     # Exit on first input object.
     [bool] $haveAny = do { ... | % { $true; break } } while ($false)
    
     # Exit on first input object that matches a condition.
     [bool] $haveAny = do { ... | % { if ($_ ...) { $true ; break } } } while ($false)
    

  • [Use a PowerShell v3+ self-contained utility function that is nontrivial to implement] See the implementation of function Test-Any below. It can be added to scripts or, for use in interactive sessions, to your $PROFILE file.

---

PowerShell v3+: Optimized utility function Test-Any

The function is nontrivial, because as of PowerShell (Core) v7.2.x, there is no direct way to exit a pipeline prematurely, so a workaround based on .NET reflection and a private type is currently necessary.

If you agree that there should be such a feature, take part in the conversation in GitHub issue #3821.

#requires -version 3
Function Test-Any {

    [CmdletBinding()]
    param(
        [ScriptBlock] $Filter,
        [Parameter(ValueFromPipeline = $true)] $InputObject
    )

    process {
      if (-not $Filter -or (Foreach-Object $Filter -InputObject $InputObject)) {
          $true # Signal that at least 1 [matching] object was found
          # Now that we have our result, stop the upstream commands in the
          # pipeline so that they don't create more, no-longer-needed input.
          (Add-Type -Passthru -TypeDefinition '
            using System.Management.Automation;
            namespace net.same2u.PowerShell {
              public static class CustomPipelineStopper {
                public static void Stop(Cmdlet cmdlet) {
                  throw (System.Exception) System.Activator.CreateInstance(typeof(Cmdlet).Assembly.GetType("System.Management.Automation.StopUpstreamCommandsException"), cmdlet);
                }
              }
            }')::Stop($PSCmdlet)
      }
    }
    end { $false }
}

• if (-not $Filter -or (Foreach-Object $Filter -InputObject $InputObject)) defaults to true if $Filter wasn't specified, and otherwise evaluates the filter (script block) with the object at hand.

  • The use of ForEach-Object to evaluate the filter script block ensures that $_ binds to the current pipeline object in all scenarios, as demonstrated in PetSerAl's helpful answer here.

• The (Add-Type ... statement uses an ad-hoc type created with C# code that uses reflection to throw the same exception that Select-Object -First (PowerShell v3+) uses internally to stop the pipeline, namely [System.Management.Automation.StopUpstreamCommandsException], which as of PowerShell v5 is still a private type. Background here: http://powershell.com/cs/blogs/tobias/archive/2010/01/01/cancelling-a-pipeline.aspx A big thank-you to PetSerAl for contributing this code in the comments.

Examples:

• PS> @() | Test-Any false

• PS> Get-EventLog Application | Test-Any # should return *right away* true

• PS> 1, 2, 3 | Test-Any { $_ -gt 1 } # see if any object is > 1 true

---

Background information

JaredPar's helpful answer and Paolo Tedesco's helpful extension fall short in one respect: they don't exit the pipeline once a match has been found, which can be an important optimization.

Sadly, even as of PowerShell v5, there is no direct way to exit a pipeline prematurely. If you agree that there should be such a feature, take part in the conversation in GitHub issue #3821.

A naïve optimization of JaredPar's answer actually shortens the code:

# IMPORTANT: ONLY EVER USE THIS INSIDE A PURPOSE-BUILT DUMMY LOOP (see below)
function Test-Any() { process { $true; break } end { $false } }

• The process block is only entered if there's at least one element in the pipeline.

  • Small caveat: By design, if there's no pipeline at all, the process block is still entered, with $_ set to $null, so calling Test-Any outside of a pipeline unhelpfully returns $true. To distinguish between between $null | Test-Any and Test-Any, check $MyInvocation.ExpectingInput, which is $true only in a pipeline: ^{Thanks, PetSerAl} function Test-Any() { process { $MyInvocation.ExpectingInput; break } end { $false } }

• $true, written to the output stream, signals that at least one object was found.

• break then terminates the pipeline and thus prevents superfluous processing of additional objects. HOWEVER, IT ALSO EXITS ANY ENCLOSING LOOP - break is NOT designed to exit a PIPELINE^{Thanks, PetSerAl} .

  • If there were a command to exit the pipeline, this is where it would go.
  • Note that return would simply move on to the next input object.

• Since the process block unconditionally executes break, the end block is only reached if the process block was never entered, which implies an empty pipeline, so $false is written to the output stream to signal that.

Answer 3

Unfortunately there is no equivalent in PowerShell. I wrote a blog post about this with a suggestion for a general purpose Test-Any function / filter.

function Test-Any() {
    begin {
        $any = $false
    }
    process {
        $any = $true
    }
    end {
        $any
    }
}

Blog post: Is there anything in that pipeline?

Answer 4

I took a more linq-style approach.

I know this question is probably super old. I used this to accomplish my needs:

PS> $searchData = "unn"
PS> $StringData = @("unn", "dew", "tri", "peswar", "pymp")
PS> $delegate =  [Func[string,bool]]{ param($d); return $d -eq $searchData }
PS> [Linq.Enumerable]::Any([string[]]$StringData, $delegate)

Taken from here:

https://www.red-gate.com/simple-talk/dotnet/net-framework/high-performance-powershell-linq/#post-71022-_Toc482783751

Answer 5

You can use the original LINQ Any:

[Linq.Enumerable]::Any($list)

Answer 6

I think that the best answer here is the function proposed by @JaredPar, but if you like one-liners as I do I'd like to propose following Any one-liner:

# Any item is greater than 5
$result = $arr | %{ $match = $false }{ $match = $match -or $_ -gt 5 }{ $match }

%{ $match = $false }{ $match = $match -or YOUR_CONDITION }{ $match } checks that at least one item match condition.

One note - usually the Any operation evaluates the array until it finds the first item matching the condition. But this code evaluates all items.

Just to mention, you can easily adjust it to become All one-liner:

# All items are greater than zero
$result = $arr | %{ $match = $false }{ $match = $match -and $_ -gt 0 }{ $match }

%{ $match = $false }{ $match = $match -and YOUR_CONDITION }{ $match } checks that all items match condition.

Notice, that to check Any you need -or and to check All you need -and.

Answer 7

This is the best method that I found so far (does not iterate over all elements if already found a true, and does not break the pipeline):

From LINQ Any() equivalent in PowerShell

It’s possible to use a built-in $input variable that contains the whole pipeline in a scope of function.

So, the desired code could look like the following:

function Test-Any([scriptBlock] $scriptBlock = {$true}, [scriptBlock] $debugOut = $null)
{
    if ($debugOut)
    {
        Write-Host(“{0} | % {{{1}}}” -f $input, $scriptBlock)
    }

    $_ret = $false;
    $_input = ($input -as [Collections.IEnumerator])

    if ($_input)
    {
        while ($_input.MoveNext())
        {
            $_ = $_input.Current;

            Write-Host $_

            if ($debugOut)
            {
                Write-Host(“Tested: [{0}]” -f (&$debugOut))
            }

            if (&$scriptBlock)
            {
                if ($debugOut)
                {
                    Write-Host(“Matched: [{0}]” -f (&$debugOut))
                }

                $_ret = $true
                break
            }
        }
    }

    $_ret
}

Answer 8

I ended up doing it with a count:

$directoryContainsSvn = {
    (Get-ChildItem $_.Name -force | ? {$_.PsIsContainer -and $_.Name -eq "_svn" -or $_.Name -eq ".svn"} | Measure-Object).Count -eq 1
}
$svnDirs = Get-ChildItem | ? {$_.PsIsContainer} | ? $directoryContainsSvn

Answer 9

It's actually quite simple - just select first $true (formatted for clarity):

[bool] ($source `
        | foreach { [bool] (<predicate>) } `
        | where { $_ } `
        | select -first 1)

Alternative way:

($source `
        | where { <predicate> } `
        | foreach { $true } `
        | select -first 1)

Answer 10

I recommend the following solution:

<#
.SYNOPSIS 
   Tests if any object in an array matches the expression

.EXAMPLE
    @( "red", "blue" ) | Where-Any { $_ -eq "blue" } | Write-Host
#>
function Where-Any 
{
    [CmdletBinding()]
    param(
        [Parameter(Mandatory = $True)]
        $Condition,

        [Parameter(Mandatory = $True, ValueFromPipeline = $True)]
        $Item
    )

    begin {
        [bool]$isMatch = $False
    }

    process {
      if (& $Condition $Item) {
          [bool]$isMatch = $true
      }
    }

    end {
        Write-Output $isMatch
    }
}

# optional alias
New-Alias any Where-Any

Answer 11

A variation on @JaredPar's answer, to incorporate the test in the Test-Any filter:

function Test-Any {
    [CmdletBinding()]
    param($EvaluateCondition,
        [Parameter(ValueFromPipeline = $true)] $ObjectToTest)
    begin {
        $any = $false
    }
    process {
        if (-not $any -and (& $EvaluateCondition $ObjectToTest)) {
            $any = $true
        }
    }
    end {
        $any
    }
}

Now I can write "any" tests like

> 1..4 | Test-Any { $_ -gt 3 }
True

> 1..4 | Test-Any { $_ -gt 5 }
False

Answer 12

You can tighten this up a bit:

gci -fo | ?{$_.PSIsContainer -and `
            (gci $_ -r -fo | ?{$_.PSIsContainer -and $_ -match '[_.]svn$'})}

Note - passing $__.Name to the nested gci is unnecessary. Passing it $_ is sufficent.

Answer 13

My approach now was:

gci -r -force `
    | ? { $_.PSIsContainer -and $_.Name -match "^[._]svn$" } `
    | select Parent -Unique

---

The reason why

select-object {$_.Directory}

doesn't return anything useful is that there is no such property on a DirectoryInfo object. At least not in my PowerShell.

---

To elaborate on your own answer: PowerShell can treat most non-empty collections as $true, so you can simply do:

$svnDirs = gci `
    | ? {$_.PsIsContainer} `
    | ? {
        gci $_.Name -Force `
            | ? {$_.PSIsContainer -and ($_.Name -eq "_svn" -or $_.Name -eq ".svn") }
        }