Arrays Are like In-Memory Database Tables

Arrays are fundamental to PowerShell scripting. They allow you to store and manipulate collections of objects, making them essential for handling data in scripts. Think of arrays as in-memory database tables where each element is a row, and you can perform operations like filtering, sorting, and slicing.

---

1. What is an Array?

An array is a collection of objects. Unlike a scalar (a single object), an array can hold zero, one, or many objects. Arrays are sometimes called collections or lists.

---

2. Creating Arrays

Empty Array

To create an empty array:

$array = @()

Array with Elements

To create an array with elements, separate them with commas:

$array = @(1, "hello", 433.2, "world")

The @() syntax ensures the variable is treated as an array, even if it contains only one element.

Implicit Array Creation

You can also create arrays without explicitly using @():

$array = 1, "hello", 433.2, "world"

Range Operator

To create an array with a sequence of numbers:

$x = 0..20000  # Array from 0 to 20000
$y = -2..150   # Array from -2 to 150
$z = 58..50058 # Array from 58 to 50058

Single-Element Array

To create an array with a single element:

$array1 = ,"Hello"  # Using a comma
$array2 = @("World") # Using @()

Appending to an Array

To add elements to an existing array:

$array += "morestuff"

---

3. Accessing Array Elements

Counting Elements

To get the number of elements in an array:

$array.Count

Displaying Elements

To display all elements:

$array

To display elements as a single string (space-separated):

[string]$array

To display elements as a comma-separated string:

$array -join ","

Accessing Specific Elements

Array elements are indexed starting from 0. Use square brackets [] to access elements:

$array[0]  # First element
$array[2]  # Third element
$array[-1] # Last element
$array[-2] # Second-to-last element

Slicing Arrays

To retrieve a range of elements:

$array[0..30]  # Elements from index 0 to 30
$array[-1..-10] # Last 10 elements (in reverse order)

To extract specific elements:

$array[0, -1]  # First and last elements

Assigning Elements to Variables

To extract elements and assign them to variables:

$v, $w, $x, $y, $z = $array[2, 30, 997, -32, -1]

---

4. Nested Arrays (Array of Arrays)

A nested array is an array that contains other arrays. This is useful for representing multi-dimensional data.

Creating Nested Arrays

$array1 = 10, 11
$array2 = 20, 22
$arrayAA = $array1, $array2  # Nested array

$array4 = 40, 44
$array5 = 50, 55
$arrayBB = $array4, $array5  # Another nested array

$bigarray = $arrayAA, $arrayBB  # Multi-level nested array

Accessing Nested Array Elements

To access elements in a nested array:

$bigarray[0][0][0]  # 10 (First element of the first nested array)
$bigarray[1][1][1]  # 55 (Second element of the second nested array)
$bigarray[1][0][1]  # 44 (Second element of the first nested array in the second level)

---

5. Manipulating Arrays

Filtering Arrays

Use Where-Object to filter arrays:

$filteredArray = $array | Where-Object { $_ -gt 100 }  # Filter elements greater than 100

Sorting Arrays

Use Sort-Object to sort arrays:

$sortedArray = $array | Sort-Object  # Sort in ascending order

Adding and Removing Elements

• Add: Use += to append elements.

• Remove: Use Where-Object to exclude elements.

Example:

$array += "newElement"  # Add an element
$array = $array | Where-Object { $_ -ne "removeThis" }  # Remove an element

---

6. Advanced Array Features

Multidimensional Arrays

PowerShell doesn’t natively support multidimensional arrays, but you can simulate them using nested arrays:

$matrix = @(
    @(1, 2, 3),
    @(4, 5, 6),
    @(7, 8, 9)
)
$matrix[1][2]  # Access element at row 1, column 2 (value: 6)

Array Slicing with Ranges

Use ranges to slice arrays dynamically:

$slice = $array[10..20]  # Elements from index 10 to 20

Output Field Separator ($OFS)

The $OFS variable controls the separator used when converting arrays to strings:

$OFS = " | "
[string]$array  # Elements separated by " | "