Variables and Data Types

# Creating variables
$name = "ShellRAG"
$age = 5
$isActive = $true
$pi = 3.14159
 
# Using variables
Write-Host "Welcome to $name!"
Write-Host "Pi is approximately $pi"

# Good variable names
$userName = "John"
$fileCount = 42
$isCompleted = $false
$serverList = @("server1", "server2")
 
# Valid but less readable
$x = 10
$_ = "current item"  # Special pipeline variable

# String
$greeting = "Hello, World!"
$greeting.GetType().Name  # String
 
# Integer
$count = 42
$count.GetType().Name  # Int32
 
# Double (decimal)
$price = 19.99
$price.GetType().Name  # Double
 
# Boolean
$isReady = $true
$isDone = $false
 
# DateTime
$now = Get-Date
$birthday = [datetime]"1990-05-15"
 
# Array
$colors = @("Red", "Green", "Blue")
 
# Hashtable
$person = @{
    Name = "Alice"
    Age  = 30
    City = "New York"
}

# Cast to integer
[int]$number = "42"
[int]$rounded = 3.7    # Result: 4
 
# Cast to string
[string]$text = 123    # Result: "123"
 
# Cast to double
[double]$decimal = "3.14"
 
# Cast to boolean
[bool]$flag = 1        # Result: $true
[bool]$flag2 = 0       # Result: $false
 
# Cast to datetime
[datetime]$date = "2026-01-15"
 
# Cast to array
[array]$list = "single item"

# Double-quoted: Supports variable expansion and escape sequences
$name = "World"
$greeting = "Hello, $name!"        # "Hello, World!"
$newline = "Line1`nLine2"          # Two lines
 
# Single-quoted: Literal strings (no expansion)
$literal = 'Hello, $name!'        # "Hello, $name!" (literal text)
$raw = 'No `n expansion here'     # No escape processing
 
# Here-strings: Multi-line strings
$multi = @"
This is a multi-line string.
Variable expansion works: $name
Useful for templates and scripts.
"@
 
$literalMulti = @'
This is a literal here-string.
No $variable expansion.
'@

$text = "PowerShell is Awesome"
 
# Length
$text.Length                       # 21
 
# Case conversion
$text.ToUpper()                    # "POWERSHELL IS AWESOME"
$text.ToLower()                    # "powershell is awesome"
 
# Substring
$text.Substring(0, 10)            # "PowerShell"
 
# Contains / StartsWith / EndsWith
$text.Contains("Shell")           # True
$text.StartsWith("Power")         # True
$text.EndsWith("Awesome")         # True
 
# Replace
$text.Replace("Awesome", "Great") # "PowerShell is Great"
 
# Split
$text.Split(" ")                  # @("PowerShell", "is", "Awesome")
 
# Join
$words = @("Hello", "World")
$words -join ", "                  # "Hello, World"
 
# Trim
"  spaces  ".Trim()               # "spaces"
"  spaces  ".TrimStart()          # "spaces  "
"  spaces  ".TrimEnd()            # "  spaces"
 
# String formatting
$formatted = "Name: {0}, Age: {1}" -f "Alice", 30
# "Name: Alice, Age: 30"
 
# Padding
"42".PadLeft(6, '0')              # "000042"
"Hi".PadRight(10, '.')            # "Hi........"

$user = "Alice"
$count = 5
 
# Simple variable
"Hello, $user"
 
# Property access (use $())
$process = Get-Process -Id $PID
"Current process: $($process.Name)"
 
# Expressions (use $())
"Sum: $(2 + 3)"
"Files: $((Get-ChildItem).Count)"
 
# Array indexing
$colors = @("Red", "Green", "Blue")
"First color: $($colors[0])"

# Standard array
$fruits = @("Apple", "Banana", "Cherry")
 
# Implicit array (comma-separated)
$numbers = 1, 2, 3, 4, 5
 
# Range operator
$range = 1..10       # 1 through 10
 
# Empty array
$empty = @()
 
# Single-item array
$single = @("only one")
 
# Typed array
[int[]]$integers = 1, 2, 3
[string[]]$names = "Alice", "Bob"

$colors = @("Red", "Green", "Blue", "Yellow")
 
# Access by index (0-based)
$colors[0]          # "Red"
$colors[-1]         # "Yellow" (last item)
$colors[1..2]       # @("Green", "Blue")
 
# Count
$colors.Count       # 4
$colors.Length       # 4
 
# Add items (creates new array)
$colors += "Purple"
 
# Check if contains
$colors -contains "Red"    # True
"Red" -in $colors          # True
 
# Find index
[array]::IndexOf($colors, "Blue")  # 2
 
# Filter
$colors | Where-Object { $_ -like "B*" }  # "Blue"
 
# Iterate
foreach ($color in $colors) {
    Write-Host $color
}
 
# ForEach method
$colors.ForEach({ $_.ToUpper() })

$list = [System.Collections.ArrayList]@()
$list.Add("Apple")    | Out-Null
$list.Add("Banana")   | Out-Null
$list.Remove("Apple")
$list.Count           # 1
 
# Or use Generic List
$typedList = [System.Collections.Generic.List[string]]::new()
$typedList.Add("Hello")
$typedList.Add("World")

# Creating a hashtable
$person = @{
    Name    = "Alice"
    Age     = 30
    City    = "New York"
    Skills  = @("PowerShell", "Python")
}
 
# Access values
$person["Name"]         # "Alice"
$person.Name            # "Alice" (dot notation)
$person.Skills[0]       # "PowerShell"
 
# Add/modify entries
$person["Email"] = "alice@example.com"
$person.Age = 31
 
# Remove entries
$person.Remove("City")
 
# Check if key exists
$person.ContainsKey("Name")    # True
$person.ContainsValue(31)      # True
 
# Get all keys/values
$person.Keys
$person.Values
 
# Iterate
foreach ($key in $person.Keys) {
    Write-Host "$key : $($person[$key])"
}
 
# Count
$person.Count

$orderedPerson = [ordered]@{
    FirstName = "Alice"
    LastName  = "Smith"
    Age       = 30
}

# Booleans
$true
$false
$null
 
# Current object in pipeline
$_            # or $PSItem
 
# Last command result
$?            # True if last command succeeded
 
# Last error
$Error[0]     # Most recent error
 
# Home directory
$HOME
 
# Current directory
$PWD
 
# Process ID
$PID
 
# PowerShell version
$PSVersionTable
 
# Script information
$MyInvocation
$PSScriptRoot     # Directory of current script
$PSCommandPath    # Full path of current script
 
# Preference variables
$ErrorActionPreference     # Default: "Continue"
$VerbosePreference         # Default: "SilentlyContinue"
$ConfirmPreference         # Default: "High"

# Check type
$value = 42
$value -is [int]          # True
$value -is [string]       # False
$value -isnot [string]    # True
 
# Get type name
$value.GetType().Name     # "Int32"
$value.GetType().FullName # "System.Int32"
 
# Check if null
$null -eq $variable       # True if $variable is null