What does "%" (percent) do in PowerShell?

Question

It seems that the % operation starts script blocks after the pipeline, although about_Script_Blocks indicates the % isn't necessary.

These all work just fine.

get-childitem | % { write-host $_.Name }

{ write-host 'hello' }

% { write-host 'hello' }

But when we add a script block after the pipeline, we need to have the % first.

get-childitem | { write-host $_.Name }

@mjolinor That's useful. I didn't know I could get help on symbols. I see that we can also lookup $_ with get-help. That's great! — Shaun Luttin, Apr 03 '14 at 19:05
@Cole9350 That's a useful item to add to the current answer. — Shaun Luttin, Apr 03 '14 at 19:09
One thing it doesn't do that cmd / batch files used to do is surround environment variables and provide string expansion. cmd used to be able to do things like `echo %programfiles%` but in powershell you'd do `echo $Env:programfiles` — Davos, Mar 08 '18 at 14:04
@mjolinor doesn't work on linux PS-with or without single/double quotes. — Yumi Koizumi, Feb 18 '19 at 16:15

Kohlbrr · Accepted Answer · 2014-04-03T19:41:17.840

194

When used in the context of a cmdlet (such as your example), it's an alias for ForEach-Object:

> Get-Alias -Definition ForEach-Object

CommandType     Name                                                Definition
-----------     ----                                                ----------
Alias           %                                                   ForEach-Object
Alias           foreach                                             ForEach-Object

When used in the context of an equation, it's the modulus operator:

> 11 % 5

1

and as the modulus operator, % can also be used in an assignment operator (%=):

> $this = 11
> $this %= 5
> $this

1

edited Apr 03 '14 at 19:41

answered Apr 03 '14 at 19:03

Kohlbrr

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I will mark this as answer once it also contains the % role as a modulus operator in different contexts. – Shaun Luttin Apr 03 '14 at 19:09
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Added equation and assignment operator examples – Kohlbrr Apr 03 '14 at 19:41
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In the case of Foreach-Object, I'd advise not using the "%" symbol - it makes it harder for folks to read/maintain your code - especially people new to PS. Let's face it, the more people that pick up PS, the better. – Simon Catlin Apr 03 '14 at 20:17
1

Where can I find the ForEach-Object meaning in the official documentation on MSDN? – Oct 24 '19 at 18:55
I disagree Simon Catlin, by that logic we should all be using assembly because the rest is just syntactic sugar – reggaeguitar Feb 06 '20 at 21:36
Another use of the percent symbol can't be simply replaced by ForEach-Object: Get-ChildItem | % Name – robbie fan Dec 16 '20 at 13:37

score 23 · Answer 2 · edited Feb 16 '20 at 06:02

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A post PowerShell - Special Characters And Tokens provides description of multiple symbols including %

% (percentage)

1. Shortcut to foreach.
Task: Print all items in a collection.
Solution.
... | % { Write-Host $_ }

2. Remainder of division, same as Mod in VB.
Example:
5 % 2

edited Feb 16 '20 at 06:02

Shaun Luttin

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answered Dec 29 '16 at 03:18

Michael Freidgeim

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@ShaunLuttin: The value is a link, which describes multiple special characters including % – Michael Freidgeim Dec 30 '16 at 00:02
Technically it's an alias for `ForEach-Object`. `ForEach` is also an alias for `ForEach-Object` - except when used at the start of a statement, where it's a loop control keyword (like `while`). – mwfearnley Aug 31 '18 at 09:15

score 7 · Answer 3 · edited Feb 16 '20 at 06:07

7

% can replace Get-ChildItem | ForEach-Object { write-host $_.Name } which will not work without either the % or the ForEach-Object.

edited Feb 16 '20 at 06:07

Shaun Luttin

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answered Jan 07 '15 at 08:59

Xao

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What does "%" (percent) do in PowerShell?

3 Answers3

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