Piping values to New-Item to create directories in PowerShell

Question

I've got a directory, C:\temp\test\, containing three DLL's I've called First.dll, Second.dll, Third.dll. I want to create sub-directories named after each of the DLL's.

This is what I've tried so far:

$dirName = "Tenth"
new-item $dirName -ItemType directory

That works. It created a sub-directory called "Tenth".

This also works:

(get-childitem -file).BaseName | select $_

It returns:

First
Second
Third

I've checked the type of the output from that command and it tells me "select $_" is of type System.String.

Now the bit that doesn't work:

(get-childitem -file).BaseName | new-item -Name $_ -ItemType directory

I get the following error repeated three times:

new-item : An item with the specified name C:\temp\test already exists.
At line:1 char:34
+ (get-childitem -file).BaseName | new-item -Name $_ -ItemType directory
+                                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ResourceExists: (C:\temp\test:String) [New-Item], IOException
    + FullyQualifiedErrorId : DirectoryExist,Microsoft.PowerShell.Commands.NewItemCommand

The current folder I'm executing the commands from is C:\temp\test\ .

I haven't been able to find any similar examples on the Internet to show me where I'm going wrong. Can anyone give me any pointers? Cheers.

user4018458 · Accepted Answer · 2015-03-29 12:13:22Z

2

Now the bit that doesn't work:

(get-childitem -file).BaseName | new-item -Name $_ -ItemType directory

This way, it works and doesn't need the ForEach-Object:

(dir -file).BaseName|ni -name{$_} -ItemType directory -WhatIf

answered Mar 29, 2015 at 12:13

user4018458

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2 Comments

Simon Elms Over a year ago

Nice, thanks. Could you explain why the braces { } are needed around the $_?

user4018458 Over a year ago

It's part of the PowerShell syntax, to refer to the pipelined object to a parameter that accepts pipeline input. ForEach-Object and Where-Object, for instance, also requires curly braces (but both got additional new syntax since v3)

Cid · Accepted Answer · 2022-02-25 07:18:43Z

2

New-Item accepts the parameter -Path to be piped and it can be an array of strings.

Then, you can create an object with a property Path that contains all the needed folders to be created

<#
 # a simple array as example,
 # but it could be the result of any enumerable,
 # such as Get-ChildItem and stuff
 #>
$FoldersToCreate = @('a', 'b', 'c')

# creates the folders a, b and c at the current working directory
[PSCustomObject]@{ Path = $FoldersToCreate } | New-Item -ItemType Directory

Or, alternatively :

$FoldersToCreate |
    Select-Object @{ name = "Path"; expression = { "c:\testDir\$_" } } |
    New-Item -ItemType Directory

answered Feb 25, 2022 at 7:18

Cid

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Comments

Bluecakes · Accepted Answer · 2015-03-23 04:54:26Z

1

$_ references each item as it comes along the pipeline so you will need to pipe to ForEach-Object for your line to work, like this:

(get-childitem -file).BaseName | ForEach-Object {new-item -Name $_ -ItemType directory}

This will create the item in the current powershell directory, you can also specify -Path if you want to create the folders somewhere else.

(get-childitem -file).BaseName | ForEach-Object {new-item -Name $_ -Path C:\MyFolder -ItemType directory}

answered Mar 23, 2015 at 4:54

Bluecakes

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