PowerShell Scripting and Programming
This guide dives deeper into the programming aspects of PowerShell, moving beyond simple one-liners to robust, reusable scripts and tools.
Parent Topic: PowerShell Comprehensive Guide
1. Script Execution
By default, Windows prevents scripts from running for security reasons.
Execution Policies
- Restricted: No scripts run. (Default on many systems)
- RemoteSigned: Scripts created locally run; downloaded scripts must be signed by a trusted publisher. (Recommended)
- Unrestricted: All scripts run, but you may be prompted before running downloaded scripts.
# Check current policy
Get-ExecutionPolicy
# Set policy (requires Admin)
Set-ExecutionPolicy RemoteSignedRunning Scripts
To run a script in the current directory, you must specify the path (e.g., .\).
.\MyScript.ps12. Advanced Functions
You can turn a simple function into a robust tool that behaves like a native cmdlet by adding [CmdletBinding()].
function Get-UserReport {
[CmdletBinding()]
param (
[Parameter(Mandatory=$true, Position=0)]
[string]$UserName,
[Parameter(ValueFromPipeline=$true)]
[string]$Department = "IT"
)
process {
Write-Verbose "Processing user: $UserName"
return [PSCustomObject]@{
Name = $UserName
Dept = $Department
Date = Get-Date
}
}
}[CmdletBinding()]: Enables common parameters like-Verbose,-WhatIf, and-Confirm.[Parameter()]: Defines validation, mandatory status, and pipeline behavior.
3. Input Validation
Ensure your script receives the right data using validation attributes.
param (
[ValidateSet("Dev", "QA", "Prod")]
[string]$Environment,
[ValidateRange(1, 100)]
[int]$Count,
[ValidateScript({ Test-Path $_ })]
[string]$FilePath
)4. Error Handling
Try-Catch-Finally
Use try-catch blocks to handle exceptions gracefully. Note that only terminating errors are caught, so use -ErrorAction Stop.
try {
# Stop error allows Catch to trigger
Get-Item "C:\Missing.txt" -ErrorAction Stop
}
catch [System.IO.FileNotFoundException] {
Write-Warning "File specifically not found."
}
catch {
Write-Error "An unexpected error occurred: $_"
}
finally {
Write-Host "Cleanup operations (runs regardless of error)..."
}Return to PowerShell Comprehensive Guide