# Functions Like Cmdlets

Functions with verb-noun names, parameters that check themselves, pipeline input, -WhatIf in your own tools, and help that Get-Help reads.

Updated: November 10, 2026

## [Functions](https://www.ask-codey.com/courses/powershell-in-depth/topics/powershell-functions)

1. [Functions: Naming a Job](https://www.ask-codey.com/lessons/powershell-functions) (Journeyman): A function you share gets a cmdlet's kind of name, an approved verb from Get-Verb and a singular noun, takes its inputs in param() and outputs objects rather than sentences, so its results can be sorted, filtered and saved; a file of functions is loaded into your session with a dot.
2. [Advanced Functions: \`\[CmdletBinding()\]\`](https://www.ask-codey.com/lessons/powershell-advanced-functions) (Journeyman): One line, \[CmdletBinding()\] above param(), turns a function into an advanced function that binds its parameters the way a cmdlet does: it refuses a misspelled parameter instead of quietly ignoring it, and gets -Verbose, -ErrorAction and the other common parameters for free.
3. [Checking Input: Validation Attributes](https://www.ask-codey.com/lessons/powershell-parameter-validation) (Journeyman): Validation attributes check a parameter's value before any line of the function runs: \[ValidateSet()\] allows only a list of choices and makes Tab fill them in, \[ValidateRange()\] keeps a number between two limits, \[ValidateNotNullOrEmpty()\] turns away an empty value, and Mandatory asks for one that's missing.
4. [Taking Pipeline Input](https://www.ask-codey.com/lessons/powershell-pipeline-input) (Freelancer): A parameter marked \[Parameter(ValueFromPipeline)\] receives each object that comes down the pipeline, a process block runs once for each of them, and begin and end run once before the first and after the last, for the setup and the totals.

## [Safety and Help](https://www.ask-codey.com/courses/powershell-in-depth/topics/powershell-safety-and-help)

1. [\`-WhatIf\` in Your Own Tools](https://www.ask-codey.com/lessons/powershell-supports-should-process) (Freelancer): SupportsShouldProcess in \[CmdletBinding()\] gives a function -WhatIf and -Confirm, and wrapping each change in if ($PSCmdlet.ShouldProcess(target, action)) makes it print a What if: line instead of changing anything, or ask before each change, exactly like Remove-Item.
2. [Help for Your Tool](https://www.ask-codey.com/lessons/powershell-comment-based-help) (Journeyman): A comment block at the top of a function, with keywords such as .SYNOPSIS, .DESCRIPTION, .PARAMETER and .EXAMPLE, becomes the function's help page, so Get-Help, -Examples and -Parameter explain your tool the way they explain PowerShell's own commands.

## [Exercise: The Playlist Tools](https://www.ask-codey.com/courses/powershell-in-depth/topics/exercise-powershell-the-playlist-tools)

1. [Exercise: The Playlist Tools](https://www.ask-codey.com/lessons/exercise-powershell-the-playlist-tools) (Journeyman): Turn four rough functions for a homework playlist into tools that behave like PowerShell's own commands, with verb-noun names, objects for output, checked input, pipeline input, -WhatIf and help, while a Pester check tries each one on its own copy of the playlist.

Source: https://www.ask-codey.com/courses/powershell-in-depth/chapters/powershell-functions-like-cmdlets