PowerShell

Personal reference notes on PowerShell: core concepts, syntax, and the cmdlets I reach for most often. For copy-paste project/file scripts I actually use, see Terminal Commands.

Related

See Linux for the Unix/bash equivalent of this page.

Core Concepts

• Object pipeline — unlike bash, PowerShell pipes pass full .NET objects, not plain text. Get-Process | Sort-Object CPU sorts on the actual CPU property, no text parsing needed.
• Verb-Noun naming — cmdlets follow a Verb-Noun pattern (Get-Item, Set-Location, Remove-Item). Verbs are standardized; run Get-Verb to see the approved list.
• Case-insensitive — commands, parameters, and most comparisons are case-insensitive by default.
• Editions — Windows PowerShell (5.1, built into Windows, powershell.exe) vs. PowerShell 7+ (cross-platform, pwsh.exe, actively developed). New scripts should target 7+.
• Providers — PowerShell exposes things like the filesystem, registry, and certificate store as navigable "drives" (cd HKLM:\, cd Cert:\).

Getting Help

Get-Help Get-Process              # help for a cmdlet
Get-Help Get-Process -Examples     # just usage examples
Get-Help Get-Process -Full          # full help incl. parameters
Update-Help                          # refresh local help files (run as admin)
Get-Command                           # list all available commands
Get-Command -Verb Get                  # list commands with a given verb
Get-Command -Noun Process                # list commands with a given noun
Get-Member                                # inspect an object's properties/methods

Get-Process | Get-Member    # see what properties/methods a Process object exposes

Variables & Types

$name = "Alice"             # string
$count = 5                    # int
$items = @("a", "b", "c")      # array
$map = @{ key = "value" }       # hashtable
$true / $false                   # booleans
$null                              # null

$name.GetType()                     # inspect the underlying .NET type
[int]"42"                            # cast to int
[string]42                            # cast to string

String interpolation uses double quotes only:

"Hello, $name!"          # interpolates
'Hello, $name!'            # literal — single quotes do not interpolate

Comparison & Logical Operators

PowerShell doesn't use ==, !=, <, > for comparisons — it uses named operators:

Operator	Meaning
-eq	equal
-ne	not equal
-gt / -lt	greater / less than
-ge / -le	greater-or-equal / less-or-equal
-like	wildcard match (*, ?)
-match	regex match
-contains	collection contains value
-in	value is in collection
-and / -or / -not	logical operators

if ($count -gt 3 -and $name -eq "Alice") { "match" }
Get-ChildItem | Where-Object { $_.Name -like "*.log" }

Control Flow

if ($x -eq 1) { "one" } elseif ($x -eq 2) { "two" } else { "other" }

foreach ($item in $items) { Write-Host $item }

for ($i = 0; $i -lt 5; $i++) { Write-Host $i }

$i = 0
while ($i -lt 5) { $i++ }

switch ($value) {
    1 { "one" }
    2 { "two" }
    default { "other" }
}

Functions & Scripts

function Get-Square {
    param([int]$Number)
    return $Number * $Number
}

Get-Square -Number 4     # 16

# Run a script
.\script.ps1

# Pass arguments
.\script.ps1 -Path "C:\data" -Verbose

Execution Policy

Controls whether scripts are allowed to run (a safety feature, not real security).

Get-ExecutionPolicy                                # check current policy
Set-ExecutionPolicy RemoteSigned -Scope CurrentUser # common dev-friendly setting

Common values: Restricted (default, no scripts), RemoteSigned (local scripts run, downloaded ones need a signature), Unrestricted, Bypass.

Profile (like .bashrc)

$PROFILE                    # path to your profile script
Test-Path $PROFILE            # check if it exists
notepad $PROFILE                # edit it
. $PROFILE                       # reload it in the current session

Use it for aliases, functions, and env vars you want in every session.

Common Cmdlets by Category

Filesystem

Get-ChildItem                 # list directory contents (alias: ls, dir, gci)
Get-ChildItem -Recurse -File    # list files recursively
Set-Location C:\path              # change directory (alias: cd)
Get-Location                        # print working directory (alias: pwd)
New-Item -ItemType Directory name      # mkdir
New-Item -ItemType File name.txt          # touch
Copy-Item src dest -Recurse                 # cp
Move-Item old new                             # mv / rename
Remove-Item path -Recurse -Force                # rm -rf
Test-Path path                                    # check if a path exists
Rename-Item old.txt new.txt                         # rename a file

Content / Text

Get-Content file.txt                    # cat
Get-Content file.txt -Tail 20             # tail
Get-Content file.txt -Wait -Tail 20         # tail -f (follow)
Set-Content file.txt "text"                   # overwrite file contents
Add-Content file.txt "text"                     # append to file
Select-String "pattern" file.txt                  # grep
Select-String "pattern" -Path *.log -Recurse        # recursive grep
(Get-Content file.txt) -replace "foo","bar" |
    Set-Content file.txt                              # sed-style replace

Processes & Services

Get-Process                       # ps aux
Get-Process -Name chrome            # filter by name
Stop-Process -Name chrome              # kill by name
Stop-Process -Id 1234                    # kill by PID
Start-Process notepad.exe                  # launch a process
Get-Service                                  # list services
Get-Service -Name wuauserv                     # filter by name
Start-Service / Stop-Service / Restart-Service   # control a service

Filtering, Sorting, Selecting (the real power of the pipeline)

Get-Process | Sort-Object CPU -Descending
Get-Process | Where-Object { $_.CPU -gt 100 }
Get-Process | Select-Object Name, Id, CPU -First 10
Get-ChildItem | Group-Object Extension
Get-ChildItem | Measure-Object -Property Length -Sum
Get-Process | ForEach-Object { $_.Name }

System Info

Get-ComputerInfo                  # OS/hardware summary
$PSVersionTable                     # PowerShell version info
Get-CimInstance Win32_OperatingSystem  # detailed OS info (modern replacement for Get-WmiObject)
Get-Disk / Get-Volume                    # disk info
Get-EventLog -LogName System -Newest 20    # recent system events (Windows PowerShell)
Get-WinEvent -LogName System -MaxEvents 20   # recent system events (PS7+)

Networking

Test-Connection host             # ping
Test-NetConnection host -Port 443  # test a specific port
Resolve-DnsName domain.com           # DNS lookup
Get-NetIPAddress                       # show IP addresses
Get-NetAdapter                           # list network adapters
Invoke-WebRequest https://example.com      # curl-like HTTP request
Invoke-RestMethod https://api.example.com    # fetch + auto-parse JSON

Modules & Packages

Get-Module -ListAvailable       # list installed modules
Install-Module ModuleName         # install from PowerShell Gallery
Import-Module ModuleName            # load a module into the session
Find-Module keyword                   # search the gallery

Remoting

Enter-PSSession -ComputerName remotehost      # interactive remote session
Invoke-Command -ComputerName remotehost -ScriptBlock { Get-Process }
New-PSSession -ComputerName remotehost           # persistent session object

Aliases Cheat Sheet

Many familiar Unix/cmd names are actually aliases for PowerShell cmdlets:

Alias	Real Cmdlet
ls, dir	Get-ChildItem
cd	Set-Location
pwd	Get-Location
cat, type	Get-Content
cp, copy	Copy-Item
mv, move	Move-Item
rm, del, erase	Remove-Item
ps	Get-Process
kill	Stop-Process
curl, wget	Invoke-WebRequest
echo	Write-Output
cls, clear	Clear-Host
history	Get-History
man, help	Get-Help

Get-Alias ls          # see what an alias actually maps to
Get-Alias -Definition Get-ChildItem   # find all aliases for a cmdlet

Redirection & Pipes

command > file          # redirect output, overwrite
command >> file            # append
command 2> file               # redirect errors (stream 2)
command 2>&1                    # merge error stream into output
command | Out-Null                # discard output
command | Tee-Object file.txt        # write to file AND pass through

Things I Keep Forgetting

• Single quotes '...' never interpolate; double quotes "..." do.
• -Force is needed to see hidden files with Get-ChildItem (and to remove read-only/system files with Remove-Item).
• Comparisons use -eq/-gt/etc., not ==/> — those have different meanings in PowerShell (> is redirection).
• $_ refers to the current pipeline object inside Where-Object / ForEach-Object blocks.
• Arrays are @(), hashtables are @{} — easy to mix up when typing fast.
• Get-ChildItem doesn't recurse by default; you need -Recurse explicitly.
• Check $PSVersionTable.PSVersion before assuming a cmdlet/parameter exists — behavior differs between Windows PowerShell 5.1 and PowerShell 7+.

Further Reading

• Microsoft PowerShell Docs
• PowerShell Gallery — community modules
• about_* conceptual help topics — run Get-Help about_Operators, Get-Help about_Pipelines, etc.