PowerShell Scripting Reference: Syntax, Commands, and Best

PowerShell scripting is a cross-platform automation framework and scripting language built on .NET, enabling administrators to control Windows, Linux, and macOS via cmdlets, pipelines, and object manipulation.

Get-Process | Where-Object { $_.CPU -gt 100 }

Tested on Ubuntu 22.04 with Linux 5.15.x; verify against vendor docs for non-Debian distributions or older kernels.

What is PowerShell scripting and when to use it?

PowerShell scripting automates administrative tasks across Windows, Linux, and macOS. It replaces repetitive manual operations with reusable .ps1 scripts that leverage the .NET framework. Use it for configuration management, system monitoring, CI/CD pipelines, and cloud orchestration.

PowerShell scripting Syntax Reference

Scripts are plaintext .ps1 files executed by the powershell.exe (Windows) or pwsh (Core) host. The language uses a verb-noun convention for cmdlets, pipeline piping (|) to pass .NET objects, and scoping via $ for variables.

# Variable creation
$location = Get-Location

# Pipeline to filter objects
Get-ChildItem -Path C:Logs -Recurse | Where-Object { $_.Length -gt 10MB }

# Function definition
function Get-ProcessSummary {
    param([string]$Name)
    Get-Process -Name $Name | Select-Object Name, CPU, PM
}

# Error handling
try {
    Invoke-Command -ComputerName SRV01 -ScriptBlock { Get-Service }
} catch {
    Write-Error $_.Exception.Message
}

PowerShell scripting Rapid Reference Cheat Sheet

Advanced Implementation & Parameters

Execution Policy Deep Dive

PowerShell enforces script execution rules via execution policies. The default on Windows is Restricted; scripts will not run. Common policies:

# View current policy
Get-ExecutionPolicy

# Set to allow local scripts
Set-ExecutionPolicy RemoteSigned -Scope LocalMachine

Policy scopes cascade: MachinePolicy > UserPolicy > Process > CurrentUser > LocalMachine. The most restrictive policy wins. Use Get-ExecutionPolicy -List to see all scopes.

Pipeline Object Handling

Every cmdlet emits .NET objects, not text. Use Get-Member to inspect properties and methods:

Get-Process | Get-Member
# Output examples: Name, Property, CPU, Method (Kill, Refresh)

Splatting for Clean Parameter Passing

$params = @{
    Path = 'C:Data'
    Filter = '*.log'
    Recurse = $true
}
Get-ChildItem @params   # Expands hashtable into named parameters

Remoting with WinRM

PowerShell Remoting requires WinRM enabled. Use Enable-PSRemoting (elevated) on target machines.

$session = New-PSSession -ComputerName SRV02 -Credential (Get-Credential)
Invoke-Command -Session $session -ScriptBlock { Get-Service -Name spooler }
Remove-PSSession $session

Error Resolution & Troubleshooting

Common Mistakes & What Not To Do

• Don’t rely on text parsing: Get-Content log.txt | Select-String "ERROR" is inefficient; use Get-WinEvent -FilterHashtable for structured logs.
• Don’t hardcode credentials: Use Get-Credential or certificate-based authentication; never embed passwords in scripts.
• Don’t ignore termination errors: Always wrap try/catch around operations that can fail (e.g., network calls, file access).
• Don’t use deprecated aliases in production: Avoid ? % @ in scripts; use full cmdlet names for readability.

Production-Grade Implementation

To minimize latency in PowerShell scripting execution, follow these practices:

• Module isolation: Develop reusable functions in .psm1 modules with a manifest (.psd1). Use Import-Module to load.
• Logging: Use Start-Transcript -Path C:Logsscript.log at the top of scripts; stop with Stop-Transcript.
• Error handling with try/catch/finally: Catch specific exception types ([System.IO.IOException], [System.UnauthorizedAccessException]).
• Least privilege: Run scripts under a service account with only required rights. Use Register-PSSessionConfiguration -ShowSecurityDescriptorUI for constrained endpoints.
• Version-aware scripting: Check $PSVersionTable.PSVersion at runtime; use #Requires -Version 5.1 in scripts.

PowerShell scripting — Performance Considerations and Tuning

When scaling PowerShell scripts, bottleneck often arises from pipeline overhead, serialized remoting, and single-threaded execution. Tuning focuses on parallelism, batch sizes, output buffering, and throttling. The following knobs are documented in official Microsoft PowerShell documentation (about_Parallel, about_Remote, about_PreferenceVariables).

• Parallelism: Use ForEach-Object -Parallel with -ThrottleLimit (default 5). Increase for I/O-bound tasks, but watch thread overhead. E.g., -ThrottleLimit 20.
• Output buffering: In remoting sessions, set $PSSessionOption.OutputBufferingMode = 'Drop' (default Block) to prevent back-pressure on the server. Requires explicit session creation with New-PSSessionOption.
• Batch sizing: When exporting large data, use Export-Csv -NoTypeInformation -Encoding utf8NoBOM and limit pipeline objects per write; consider Group-Object -AsHashTable for deduplication.
• History & errors: Reduce $MaximumHistoryCount (default 4096) to free memory, and set $ErrorActionPreference = 'Stop' for early exit (avoids expensive error collection).

Real commands to surface these settings:

# View current throttle limit default (requires a parallel-enabled edition)
(Get-Command ForEach-Object -ParameterName ThrottleLimit).DefaultParameterSet

# Increase parallelism and limit output buffering in a remote session
$opt = New-PSSessionOption -OutputBufferingMode Drop
$s = New-PSSession -ComputerName SRV1 -SessionOption $opt
Invoke-Command -Session $s -ScriptBlock { 1..100 | ForEach-Object -Parallel { $_ } -ThrottleLimit 20 }

# Optimize CSV export by batching with -Property
$data | Select-Object -First 1000 | Export-Csv -Path results.csv -NoTypeInformation -Append
# Repeat for subsequent batches (avoid single large pipeline)

Monitor script runtime with Measure-Command and pipeline depth using $PSVersionTable.PSVersion to ensure you are on PowerShell 7+ (required for -Parallel). For deep tuning, refer to Microsoft’s about_Scenarios and about_PreferenceVariables documentation.

Advanced: Mapping PowerShell Scripting Concepts to Cloud Connectivity

Note: Cloud equivalents use platform-specific PowerShell modules; install via Install-Module -Name Az or AWS.Tools.Common.

Frequently Asked Questions

Get-ChildItem -Path C:Logs -Filter '*.log' -Recurse -Depth 2

1..10 | ForEach-Object -Parallel { Start-Sleep -Seconds 1 } -ThrottleLimit 5

Invoke-Command -ComputerName SRV01 -Credential $cred -ScriptBlock { script.ps1 }

Get-Process -Name 'sshd' | Select-Object Id, ProcessName

$reader = [System.IO.StreamReader]::new('huge.log'); while (($line = $reader.ReadLine()) -ne $null) { $line }; $reader.Close()