PowerShell Basics¶

PowerShell is a cross-platform shell and scripting language built on .NET. Unlike bash which pipes text, PowerShell pipes objects. This entry covers cmdlets, navigation, variables, pipelines, and scripts.

Key Facts¶

Cmdlets follow Verb-Noun naming: Get-ChildItem, Set-Location
Pipelines pass objects, not text
Many Unix aliases work: ls, cd, cp, mv, rm, cat
Windows PowerShell (5.1) = .NET Framework, Windows-only
PowerShell (7+) = .NET Core, cross-platform

Set-Location C:\Users\data    # change directory
cd C:\Users\data              # alias
cd ..                         # up one level
cd ~                          # home directory
Get-Location                  # current directory (pwd)

File Operations¶

Get-ChildItem                 # list (ls, dir)
Get-ChildItem -Recurse        # recursive
Get-ChildItem *.txt           # filter

Copy-Item file.txt dest\     # copy (cp)
Copy-Item dir\ dest\ -Recurse
Move-Item file.txt dest\     # move/rename (mv)
Remove-Item file.txt         # delete (rm)
Remove-Item dir\ -Recurse    # delete directory

New-Item file.txt -ItemType File       # create file
New-Item folder -ItemType Directory    # create directory (mkdir)

Variables¶

$myVar = "value"
$num = 42
echo $myVar                   # print (Write-Output)
$myVar.GetType()              # type info

Environment Variables¶

$env:PATH                     # PATH variable
$env:USERNAME                 # current user
$env:COMPUTERNAME             # machine name
$env:TEMP                     # temp directory
$env:MY_VAR = "value"         # set (session only)

Cmdlet Structure¶

Get-Command                   # list all commands
Get-Command -Verb Get         # filter by verb
Get-Help Get-ChildItem        # help
Get-Help Get-ChildItem -Examples  # examples
Get-Alias                     # list all aliases
Get-Alias ls                  # what ls maps to

Pipelines (Object-Based)¶

Get-Process | Where-Object {$_.CPU -gt 10}      # filter
Get-Service | Sort-Object Status                 # sort
Get-ChildItem | Select-Object Name, Length       # select fields
Get-Content file.txt | Measure-Object -Line      # count lines

# $_ = current pipeline object
Get-Process | ForEach-Object { Write-Host $_.Name }

Output and Formatting¶

Write-Host "text"             # console only (not pipeline)
Write-Output "text"           # to pipeline
Write-Error "error"           # error stream

Get-Process | Format-Table    # table view
Get-Process | Format-List     # list view
Get-Process | Out-GridView    # GUI grid (Windows)

Functions¶

function Get-Greeting {
    param([string]$Name = "World")
    Write-Output "Hello, $Name!"
}
Get-Greeting -Name "Alice"

Scripts (.ps1)¶

.\myscript.ps1                # run script
Get-ExecutionPolicy           # check policy
Set-ExecutionPolicy RemoteSigned      # allow local scripts
Set-ExecutionPolicy Bypass -Scope Process  # current session only

Profile (Startup Config)¶

$PROFILE                      # path to profile file
notepad $PROFILE              # edit

Common One-Liners¶

# File operations
Get-ChildItem -Recurse -Filter "*.log"
Select-String -Path *.txt -Pattern "error"
Test-Path C:\file.txt
Get-Content file.txt
"content" | Out-File file.txt
Add-Content file.txt "more"

# Process management
Get-Process
Stop-Process -Name notepad
Start-Process notepad

# Network
Test-NetConnection google.com -Port 80
Invoke-WebRequest https://example.com

Aliases Reference¶

Alias	Cmdlet
`ls`, `dir`	`Get-ChildItem`
`cd`	`Set-Location`
`cp`	`Copy-Item`
`mv`	`Move-Item`
`rm`, `del`	`Remove-Item`
`cat`, `type`	`Get-Content`
`echo`	`Write-Output`
`pwd`	`Get-Location`
`ps`	`Get-Process`
`kill`	`Stop-Process`

Gotchas¶

PowerShell aliases look like Unix but pass objects, not text - piping behavior differs
-Recurse not -r (PowerShell uses full parameter names)
rm in PowerShell is Remove-Item, not GNU rm - different flags
Execution policy may block scripts - check with Get-ExecutionPolicy
Write-Host does NOT go to pipeline - use Write-Output for piping
String comparison is case-insensitive by default (use -ceq for case-sensitive)