PowerShell Introduction

PowerShell is a cross-platform shell and scripting language built on .NET. It works with objects rather than plain text, making it far more powerful than traditional shells for automation and system administration.

Installation

Windows — PowerShell 5.1 is built-in. Install the latest PowerShell 7+:

winget install Microsoft.PowerShell

macOS:

brew install --cask powershell

Linux (Ubuntu/Debian):

sudo apt install powershell

Verify installation:

$PSVersionTable.PSVersion

PowerShell vs CMD vs Bash

Feature	CMD	Bash	PowerShell
Object pipeline	No	No	Yes
.NET integration	No	No	Yes
Cross-platform	No	Yes	Yes (PS 7+)
Remote management	Limited	SSH	Built-in (PSSessions)
Module ecosystem	No	Yes	Yes (PSGallery)

Basic Syntax

# Variables — prefix with $
$name = "Alice"
$age = 30
$isAdmin = $true

# String interpolation
Write-Host "Hello, $name! You are $age years old."

# Arrays
$fruits = @("apple", "banana", "cherry")
$fruits[0]          # apple
$fruits.Count       # 3

# Hash tables
$person = @{
    Name = "Alice"
    Age  = 30
    City = "London"
}
$person.Name        # Alice
$person["Age"]      # 30

Cmdlet Naming Convention

PowerShell uses Verb-Noun naming. Common verbs:

Verb	Purpose	Example
Get	Retrieve data	Get-Process, Get-Content
Set	Change something	Set-Location, Set-Content
New	Create something	New-Item, New-Object
Remove	Delete something	Remove-Item, Remove-Service
Start	Begin a process	Start-Process, Start-Service
Stop	End a process	Stop-Process, Stop-Service
Invoke	Execute	Invoke-WebRequest, Invoke-Command

Working with Files

# List files
Get-ChildItem                    # like ls
Get-ChildItem -Recurse *.log     # find all .log files

# Read a file
Get-Content .\readme.txt
Get-Content .\readme.txt | Select-Object -First 10   # head -10

# Write to a file
"Hello World" | Out-File .\output.txt
"Appended line" | Add-Content .\output.txt

# Copy, move, delete
Copy-Item .\source.txt .\dest.txt
Move-Item .\old.txt .\new.txt
Remove-Item .\temp.txt

# Create directory
New-Item -ItemType Directory -Path .\logs

The Pipeline

PowerShell pipes objects, not text. Each cmdlet receives and passes full .NET objects:

# Get all processes using more than 100MB, sorted by memory
Get-Process | Where-Object { $_.WorkingSet -gt 100MB } | Sort-Object WorkingSet -Descending

# Get the 5 largest files in a directory
Get-ChildItem -Recurse | Sort-Object Length -Descending | Select-Object -First 5 Name, Length

# Count lines in a file
Get-Content .\log.txt | Measure-Object -Line

# Find processes by name
Get-Process | Where-Object Name -like "node*"

Filtering and Selecting

# Where-Object — filter
Get-Service | Where-Object Status -eq "Running"

# Select-Object — choose properties
Get-Process | Select-Object Name, Id, CPU | Format-Table

# ForEach-Object — transform
1..5 | ForEach-Object { $_ * 2 }    # 2, 4, 6, 8, 10

# Group-Object — group
Get-Process | Group-Object Name | Sort-Object Count -Descending

Useful One-Liners

# Find files modified in the last 7 days
Get-ChildItem -Recurse | Where-Object LastWriteTime -gt (Get-Date).AddDays(-7)

# Kill all node processes
Get-Process node | Stop-Process

# Get public IP address
(Invoke-WebRequest -Uri "https://api.ipify.org").Content

# Extract lines matching a pattern (like grep)
Get-Content .\log.txt | Select-String "ERROR"

# Show disk usage
Get-PSDrive | Where-Object Provider -like "*FileSystem*" | Select-Object Name, Used, Free

# List environment variables
Get-ChildItem Env:

# Encode/decode Base64
[Convert]::ToBase64String([Text.Encoding]::UTF8.GetBytes("hello"))
[Text.Encoding]::UTF8.GetString([Convert]::FromBase64String("aGVsbG8="))

Getting Help

# Built-in help system
Get-Help Get-Process
Get-Help Get-Process -Examples
Get-Help Get-Process -Full

# Update help files
Update-Help

# Find commands
Get-Command *process*
Get-Command -Verb Get -Noun *file*