This document discusses best practices for creating reusable PowerShell functions and modules. It recommends breaking code into manageable chunks using functions, following standard naming conventions, making functions flexible by supporting parameters and the pipeline. Functions should be organized into modules for easy distribution and access. Modules can be imported to reuse functions across scripts and automation systems. Source control is suggested to back up and track changes to functions over time.

1. @jonathanmedd

2. PowerShell and PowerCLI
Other programming languages are
available………
…but the principles in this session can
typically be applied to most of them.

3. …move your code from
the equivalent of this….
…to this………

4. From Command to Script…..

5. ….to Function
Reasons for functions:
Primary: Break up code to
manageable, reusable chunks
Also:
1. No cmdlet exists for a task
2. Existing cmdlet doesn’t behave like you want
it to
3. String multiple cmdlets together

6. Functions…….
function Get-Something {
Take some input
Do something with it
Produce some output
}
function Set-Something {
Take some input
Change the configuration of something
}

7. Function Recommendations
1)
Name Your Functions Verb-Noun
Get-VMHostLicense & Set-VMHostLicense
Get-Verb | Sort Verb
….will give you a list of approved verbs

8. Function Recommendations
2)
Use Built-In Help

10. Function Recommendations
3)
Generalise everything!
No hardcoded data in functions (or scripts)!
Data should always come from an external
source…CSV, XML, SQL database….etc

11. Function Recommendations
4)
Parameters

12. Function Recommendations
Pipeline Support
ValueFromPipeline = $true
and
5)

13. Function Flexibility
You need to be able to cater for pipeline
support:
Get-VMHost | Get-VMHostSomething
as well as
Get-VMHostSomething –VMHost ESXi01,ESXI02

14. Function Templates
Build up templates for Get-Something and SetSomething, then to create say GetVMHostiSCSIBinding, all you need is this:

15. ….to Module
A method to organise your functions into
collections of functions
 Easy to distribute via file copy / XCOPY
 Easy to access all functions via:

Import-Module MyModule

Tip: Use a Module Manifest to make your
module professional: New-ModuleManifest

16. Modules

Typically will contain at least 2 files
 *.psm1 - containing your functions
 *.psd1 – the manifest
 $env:PSModulePath contains the path Import-
Module will look for modules
○ Typically this is your user
profileDocumentsWindowsPowerShellModules and
○
C:Windowssystem32WindowsPowerShellv1.0Mo
dules - use this one for deployment!

17. Modules

18. Modules: PSM1
Difficult to
find
individual
functions
 Hassle to
maintain to
keep them
in a
particular
order


20. Nested Modules
Break each module down into
Nested Modules each
containing a single function
 Reference the Nested
Modules in the *.psd1


22. Import-Module vSphereTools

24. Module: Search

Search for string patterns
dir * -Recurse | Select-String 'PSBoundParameters'

25. Module: Search

Search for metadata
Search-ModuleTag -Module vSphereTools -Tag ‘iscsi’

26. Modules: Considerations

Module Dependencies – One module may
requires functions from another module

Generic module with standard tools for other
modules

27. Flexibility

Now you have code broken down into
Functions and Modules you can pick out
various functions or entire modules to plug
into:
 Command line use
 Scripts
 Automation and Orchestration systems

28. Backup / Source Control
Internal File Share
 Dropbox or other….


Git / Atlassian Stash
 Free Atlassian SourceTree client for Windows and
OSX. Works with all Git repositories (not just
Stash), including GitHub

29. Source Control – Version History

31. Template Functions
Will be available on my blog after this presentation
○ Get-Something
○ Set-Something
○ Get-VMSomething
○ Set-VMSomething
○ Get-VMHostSomething
○ Set-VMHostSomething

32. Template Snippets
And also these….Ctrl-J in PowerShell ISE

33. Tweet Poll Results