PowerShell Cheat-Sheet

PowerShell is a task automation and configuration management program from Microsoft, consisting of a command-line shell and the associated scripting language.

Install PowerShell #

PowerShell was made open-source and cross-platform with PowerShell Core, and can be installed on multiple operating systems.

Windows #

1. Download MSI Package from the Official PowerShell Docs
2. Set up PowerShell Profile in Windows Terminal.

"commandline": "pwsh.exe -nologo",
"name": "Powershell",
"source": "Windows.Terminal.PowershellCore"

Linux (Ubuntu) #

# Update the list of packages
sudo apt-get update
# Install pre-requisite packages.
sudo apt-get install -y wget apt-transport-https software-properties-common
# Download the Microsoft repository GPG keys
wget -q https://packages.microsoft.com/config/ubuntu/20.04/packages-microsoft-prod.deb
# Register the Microsoft repository GPG keys
sudo dpkg -i packages-microsoft-prod.deb
# Update the list of packages after we added packages.microsoft.com
sudo apt-get update
# Install PowerShell
sudo apt-get install -y powershell
# Start PowerShell
pwsh

Profile #

Set up a PowerShell Profile by opening the profile script :

code $PROFILE

(Optional) Set up starship Prompt #

You can customize the look and feel of PowerShell with the Starship Prompt.

Getting Around #

Commands are Verb-Noun (Get-, Set-, New-, Remove-). Run Get-Verb for approved verbs. Tab completion works on commands, parameters and values.

Pipeline and Objects #

PowerShell pipes objects, not text, so you filter and sort on properties instead of parsing columns. Everything flows left to right through |.

Get-Process |
  Where-Object CPU -gt 100 |
  Sort-Object CPU -Descending |
  Select-Object -First 5 Name, Id, CPU

Filter early (Where-Object as far left as possible, or use the cmdlet’s own -Filter parameter) and format last (Format-* output is for the screen, not for more processing).

Variables and Data #

Files and Data Formats #

Error Handling #

PowerShell has terminating errors (stop the script, catchable) and non-terminating errors (print and continue). Most cmdlet errors are non-terminating, so try/catch only sees them if you ask.

try {
    Get-Item C:\missing.txt -ErrorAction Stop
    Write-Output "found"
}
catch [System.Management.Automation.ItemNotFoundException] {
    Write-Warning "Not found: $($_.Exception.Message)"
}
catch {
    Write-Error "Unexpected: $_"
    throw                      # rethrow
}
finally {
    Write-Output "cleanup always runs"
}

External programs do not throw: check $LASTEXITCODE after calling them (for example robocopy, see Robocopy).

Functions and Scripts #

function Get-DiskReport {
    [CmdletBinding()]
    param(
        [Parameter(Mandatory)][string]$ComputerName,
        [int]$MinFreeGB = 10
    )
    Get-CimInstance Win32_LogicalDisk -ComputerName $ComputerName -Filter "DriveType=3" |
        Where-Object { ($_.FreeSpace / 1GB) -lt $MinFreeGB } |
        Select-Object DeviceID, @{n='FreeGB'; e={[math]::Round($_.FreeSpace / 1GB, 1)}}
}

Save as script.ps1 and run .\script.ps1 (the .\ is required). Use [CmdletBinding()] for -Verbose, -ErrorAction and other common parameters, and param() with attributes for validation ([ValidateSet('a','b')], [ValidateRange(1,10)]).

Remoting #

Run commands on other machines with Invoke-Command -ComputerName <SERVER> -ScriptBlock { ... } or open an interactive session with Enter-PSSession. WinRM and SSH setup, sessions and file copy are in PowerShell Remote Access. Remote output comes back as deserialised objects (properties yes, methods no).

Scheduled Tasks #

Create a daily task that runs a script as SYSTEM:

$action  = New-ScheduledTaskAction -Execute "pwsh.exe" -Argument '-NoProfile -ExecutionPolicy Bypass -File "C:\Scripts\backup.ps1"'
$trigger = New-ScheduledTaskTrigger -Daily -At 3am
$settings = New-ScheduledTaskSettingsSet -StartWhenAvailable -ExecutionTimeLimit (New-TimeSpan -Hours 2)
Register-ScheduledTask -TaskName "Nightly Backup" -Action $action -Trigger $trigger -Settings $settings -User "SYSTEM" -RunLevel Highest

Other triggers: -Weekly -DaysOfWeek Monday -At 6am, -AtStartup, -AtLogOn, -Once -At (Get-Date).AddMinutes(5) -RepetitionInterval (New-TimeSpan -Minutes 15). Use powershell.exe instead of pwsh.exe if PowerShell 7 is not installed. A task’s “Last Run Result” of 0 means success.

Useful One-Liners #