Powershell dots and ampersands

19 Jan 2025 - jhunter

Sources

help about_Operators -ShowWindow

Summary

This blog shows a couple of ways to use dots . and ampersands & in PowerShell.

Dot .

Using a dot as the present working directory

When writing the path to a file, begin the path like this to show that the item is inside the present working directory.

.\

For example:

get-childitem .\

Using a dot as a sourcing operator

Run a script in the current scope.

. C:\Temp\20250119_test.ps1

You can use the dot sourcing operator as an alias of ìmport-module, when the .ps1 file contains functions.

Ampersand &

Call operator

The ampersand is a call operator. When you call a script file with the ampersand the code is run in a different scope to the curent one.

& C:\Temp\20250119_test.ps1

Since the script gets executed in another scope, it doesn’t make sense to use an ampersand to import a function.

Example

I create this simple function inside the file C:\Temp\20250119_test.txt.

function james-test{

        $x = 1
        return $x

}

Trying to import the script with an ampersand fails. With the dot source operator it works.

Once the function is imported, the $x variable is still null.

PS C:\Temp> & .\20250119_test.ps1
PS C:\Temp> dir function:*james*
PS C:\Temp>
PS C:\Temp> $x
PS C:\Temp>
PS C:\Temp> . .\20250119_test.ps1
PS C:\Temp> dir function:*james*

CommandType     Name                                               Version    Source
-----------     ----                                               -------    ------
Function        james-test

PS C:\Temp> $x
PS C:\Temp>

When I run the function with an ampersand the script runs in another scope and returns the value of $x. However, the value of $x in the current scope is unchanged.

Interestingly, if I run the function without any call operator, it is as if I used the ampersand. The function is executed but the value of $x is unchanged in the current scope.

The value of $x is changed if I run the function in the current scope with a dot.

PS C:\Temp> & james-test
1
PS C:\Temp> $x
PS C:\Temp>
PS C:\Temp> james-test
1
PS C:\Temp> $x
PS C:\Temp>
PS C:\Temp>
PS C:\Temp> . james-test
1
PS C:\Temp> $x
1
PS C:\Temp>