Operators and Comparisons

# Basic math
5 + 3          # 8    (Addition)
10 - 4         # 6    (Subtraction)
6 * 7          # 42   (Multiplication)
20 / 3         # 6.67 (Division)
20 % 3         # 2    (Modulus/remainder)
 
# Assignment operators
$x = 10
$x += 5        # $x is now 15
$x -= 3        # $x is now 12
$x *= 2        # $x is now 24
$x /= 4        # $x is now 6
$x %= 4        # $x is now 2
 
# Increment / Decrement
$i = 0
$i++            # $i is now 1
$i--            # $i is now 0
 
# Power
[math]::Pow(2, 10)   # 1024
 
# Size constants
1KB    # 1024
1MB    # 1048576
1GB    # 1073741824
1TB    # 1099511627776
 
# Useful for file sizes
$size = 1.5GB
"$([math]::Round($size / 1MB, 2)) MB"  # "1536 MB"

# Equality
5 -eq 5          # True  (equal)
5 -ne 3          # True  (not equal)
 
# Greater / Less than
10 -gt 5         # True  (greater than)
10 -ge 10        # True  (greater or equal)
3 -lt 7          # True  (less than)
3 -le 3          # True  (less or equal)
 
# String comparisons (case-insensitive by default)
"Hello" -eq "hello"    # True
"Hello" -ceq "hello"   # False (case-sensitive)
"Hello" -ieq "hello"   # True  (explicitly case-insensitive)

"ABC" -ceq "abc"      # False
"ABC" -cne "abc"      # True
"ABC" -clike "A*"     # True
"ABC" -clike "a*"     # False

"PowerShell" -like "Power*"          # True
"PowerShell" -like "*Shell"          # True
"PowerShell" -like "*wer*"          # True
"PowerShell" -like "P??erShell"     # True (? = single char)
"PowerShell" -notlike "Bash*"       # True
 
# Filter arrays with wildcards
$names = "Alice", "Bob", "Alex", "Anna"
$names -like "A*"      # @("Alice", "Alex", "Anna")

# Basic regex matching
"PowerShell 7.4" -match "\d+\.\d+"      # True
$Matches[0]                                # "7.4"
 
# Email validation
"[email protected]" -match "^[\w.-]+@[\w.-]+\.\w+$"  # True
 
# Extract groups
"2026-02-10" -match "(\d{4})-(\d{2})-(\d{2})"
$Matches[1]    # "2026"
$Matches[2]    # "02"
$Matches[3]    # "10"
 
# Named groups
"John is 30" -match "(?<name>\w+) is (?<age>\d+)"
$Matches.name  # "John"
$Matches.age   # "30"
 
# Array filtering
$emails = "[email protected]", "invalid", "[email protected]"
$emails -match "@"    # @("[email protected]", "[email protected]")

# Simple replace
"Hello World" -replace "World", "PowerShell"
# "Hello PowerShell"
 
# Regex replace
"Phone: 123-456-7890" -replace "\d", "X"
# "Phone: XXX-XXX-XXXX"
 
# Capture group replacement
"John Smith" -replace "(\w+) (\w+)", '$2, $1'
# "Smith, John"
 
# Remove pattern
"Hello   World" -replace "\s+", " "
# "Hello World"

# Check if collection contains value
$fruits = "Apple", "Banana", "Cherry"
$fruits -contains "Banana"    # True
$fruits -contains "Grape"     # False
$fruits -notcontains "Grape"  # True
 
# Reverse syntax with -in
"Banana" -in $fruits          # True
"Grape" -notin $fruits        # True

# AND - both must be true
$true -and $true      # True
$true -and $false     # False
 
# OR - at least one must be true
$true -or $false      # True
$false -or $false     # False
 
# NOT - inverts the value
-not $true            # False
-not $false           # True
!$false               # True (shorthand)
 
# XOR - exactly one must be true
$true -xor $false     # True
$true -xor $true      # False
 
# Practical examples
$age = 25
$hasLicense = $true
 
if ($age -ge 18 -and $hasLicense) {
    Write-Host "Can drive"
}
 
$isWeekend = (Get-Date).DayOfWeek -in "Saturday", "Sunday"
if ($isWeekend -or $isHoliday) {
    Write-Host "Day off!"
}

# Type checking
42 -is [int]                # True
"Hello" -is [string]        # True
$null -is [object]          # False
 
# Type conversion
42 -as [string]             # "42"
"3.14" -as [double]         # 3.14
"notanumber" -as [int]      # $null (safe conversion)

# Create a range
1..5           # @(1, 2, 3, 4, 5)
5..1           # @(5, 4, 3, 2, 1)
-3..3          # @(-3, -2, -1, 0, 1, 2, 3)
 
# Useful with ForEach
1..5 | ForEach-Object { "Item $_" }
 
# Generate alphabet
[char[]]([int][char]'A'..[int][char]'Z')

# Split
"one,two,three" -split ","     # @("one", "two", "three")
"Hello World" -split "\s"      # @("Hello", "World")
 
# Split with limit
"a-b-c-d" -split "-", 3       # @("a", "b", "c-d")
 
# Join
"Red", "Green", "Blue" -join ", "    # "Red, Green, Blue"
1..5 -join "-"                       # "1-2-3-4-5"

# Traditional if/else
$status = if ($age -ge 18) { "Adult" } else { "Minor" }
 
# Ternary operator (PowerShell 7+)
$status = $age -ge 18 ? "Adult" : "Minor"
 
# Null coalescing (PowerShell 7+)
$value = $null
$result = $value ?? "default"     # "default"
 
# Null coalescing assignment
$value ??= "default"              # Assigns "default" only if $value is $null
 
# Null conditional (Pipeline chain operators)
Get-Process -Name "notepad" -ErrorAction SilentlyContinue && Write-Host "Notepad is running"
Get-Process -Name "nonexistent" -ErrorAction SilentlyContinue || Write-Host "Process not found"

$email = Read-Host "Enter your email"
 
if ($email -match "^[\w.+-]+@[\w-]+\.[\w.]+$") {
    Write-Host "Valid email: $email" -ForegroundColor Green
} else {
    Write-Host "Invalid email format" -ForegroundColor Red
}

Get-ChildItem -File | ForEach-Object {
    $sizeCategory = switch ($true) {
        ($_.Length -lt 1KB) { "Tiny" }
        ($_.Length -lt 1MB) { "Small" }
        ($_.Length -lt 100MB) { "Medium" }
        ($_.Length -lt 1GB) { "Large" }
        default { "Huge" }
    }
 
    [PSCustomObject]@{
        Name     = $_.Name
        Size     = "$([math]::Round($_.Length / 1KB, 1)) KB"
        Category = $sizeCategory
    }
}