PowerShell for N00bs: Libraries, Paths, and You

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One of the scripts a coworker inherited has the following workflow:

1. Set-Location $PathContainingScript

2. & $Script

Why?  Because the original author was a believer in libraries.  Or, specifically, TheMotherOfAllLibraries.ps1.  Divide the library into ones for AD, one for host management, etc, or keeping them all in one huge file, that’s a personal decision.  However, making the user change their location to the location of the script is a pretty bad user experience.  To start with, it is prone to error – most command are either run by

 & command.ext

… if it’s on the $env:PATH, or

 $PsProvider:\path\to\command.ext

if it isn’t on the $env:PATH. 

Making the user Set-Location is just begging for the user to run .\Do-Something.ps1 | Set-Content output.txt, which litters it into $PsProvider:\path\to (\command.ext)

The other reason is just as simple: the user may want to be in their current location for a reason.  Why force it, not when it’s so easy to include it in the script?

In short, there’s really no reason to make the user Set-Location like this.

Here’s how to fix it:

 $scriptName = (&{$MyInvocation}).InvocationName;
$baseName = Split-Path -Path $scriptName -Leaf;
$dirName = Split-Path -Path $scriptName -Parent;
Import-Module "$dirName\function_library.psm1";

Or, if you want brevity at the cost of readability:

 Import-Module "$(Split-Path -Path (&{$MyInvocation}).InvocationName -Parent)\function_library.psm1";