PowerShell Scripting Cheat Sheet

Quick reference for common PowerShell scripting patterns.

Variables

$variable = "value"                    # Create/assign variable
$number = 42
$result = Get-Date
[int]$age = 25                         # Declare type explicitly
$var = $null                           # Empty variable

String Operations

$greeting = "Hello, " + $name          # Concatenation
$message = "Hello, $name"              # String interpolation ($ works inside "")
$text = 'No $variables here'           # Single quotes are literal
$path = "C:\folder\file.txt"           # Escape backslash: C:\\
$fullname = "$first$last"              # Multiple variables
[string]$text = "Convert to string"

Arrays

$arr = @(1, 2, 3, 4, 5)               # Create array
$arr[0]                                # Access first element (0-based)
$arr[-1]                               # Last element
$arr.Length                            # Array size
$arr += 6                              # Add element

Input/Output

Write-Host "Display text"              # Output to console
Write-Host "Red text" -ForegroundColor Red
Write-Host -NoNewline "No newline"     # Same line
$input = Read-Host -Prompt "Enter value"  # Get user input
$input = Read-Host "Enter value"       # Same (prompt optional)

File Operations

Test-Path -LiteralPath $filepath       # File/folder exists?
Set-Content -Path $file -Value $data   # Create/overwrite file
Add-Content -Path $file -Value $data   # Append to file
Get-Content -Path $file                # Read entire file
Remove-Item -Path $file                # Delete file
Get-ChildItem -Path "C:\folder"        # List directory

If/Else Statements

If ($condition) {
    # Code runs if true
}

If ($x -eq 5) {
    # Equal to
} ElseIf ($x -lt 5) {
    # Less than
} Else {
    # None of above
}

Comparison Operators

-eq                                    # Equal
-ne                                    # Not equal
-lt                                    # Less than
-le                                    # Less than or equal
-gt                                    # Greater than
-ge                                    # Greater than or equal
-and                                   # AND (both must be true)
-or                                    # OR (at least one true)
-not                                   # NOT (reverse true/false)
-contains                              # Array contains value

For Loop

For ($i = 1; $i -le 10; $i++) {
    Write-Host $i
}
# Prints 1 through 10

For ($i = 0; $i -lt $arr.Length; $i++) {
    Write-Host $arr[$i]
}
# Loop through array by index

While Loop

While ($count -lt 10) {
    Write-Host $count
    $count++
}
# Runs while condition is true

Do {
    $answer = Read-Host "Enter y or n"
} While (($answer -ne "y") -and ($answer -ne "n"))
# Do-While: runs at least once

ForEach Loop

ForEach ($item in $array) {
    Write-Host $item
}
# Loop through each element

$numbers | ForEach-Object { $_ * 2 }
# Pipeline version (advanced)

Parameters (Script Arguments)

# Access via $args
If ($args[0]) { $duration = $args[0] }      # First argument
If ($args[1]) { $filename = $args[1] }      # Second argument

# Formal parameters (cleaner)
param (
    [int]$duration = 60,
    [string]$filename = "output.txt"
)
# Usage: .\script.ps1 -duration 120 -filename "results.txt"

Functions

function Add-Numbers($a, $b) {
    return $a + $b
}

$result = Add-Numbers 5 3
Write-Host $result                     # Output: 8

function CheckValidity($input) {
    If ($input -eq '1' -or $input -eq '2') {
        return $true
    }
    return $false
}

Comments

# Single line comment

<# Multi-line comment
   Very useful for longer
   explanations #>

Conditional Assignment

$value = If ($condition) { "true value" } Else { "false value" }

# Sets $value based on condition
If ($age -ge 18) {
    $status = "Adult"
} Else {
    $status = "Minor"
}

Switch Statement

Switch ($choice) {
    '1' { Write-Host "Option 1" }
    '2' { Write-Host "Option 2" }
    '9' { exit }
    default { Write-Host "Invalid choice" }
}

Counting/Measuring

$length = $string.Length               # String character count
$count = ($array).Count                # Array element count
$lines = @(Get-Content $file).Length   # File line count

Exiting Script

exit                                   # Exit immediately
exit 0                                 # Exit with success code
exit 1                                 # Exit with error code

Date/Time

Get-Date                               # Current date/time
Get-Date -Format "yyyyMMddHHmmss"      # Formatted: 20240115143022
$later = (Get-Date) + (New-TimeSpan -Seconds 60)  # Add 60 seconds

Clear Screen

clear                                  # Clear console
cls                                    # Same thing

Increment/Decrement

$count++                               # Add 1
$count--                               # Subtract 1
$count += 5                            # Add 5
$count -= 3                            # Subtract 3

Multiple Conditions

If (($age -ge 18) -and ($license -eq $true)) {
    # Both must be true
}

If (($choice -ne '1') -and ($choice -ne '2') -and ($choice -ne '9')) {
    # Repeat until valid input
}

If (($status -eq 'Active') -or ($status -eq 'Pending')) {
    # At least one is true
}