PowerShell Arrays

Arrays are a data structure that holds a collection of items. Items can be of the same type or multiple types.

Creating an Array

Separating items by commas (,) is the simplest way to create an array in PowerShell.

$my_arr = 25, "Codecademy", 1, $False

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Alternatively, the array subexpression operator @( ) can be used. Anything placed within the parentheses is treated as an item of the array.

# 3 elements
$arr_1 = @($True, 5, (Get-Date).DateTime)

# Empty Array
$arr_2 = @( )

# Multi-line Array
$arr_3 = @(
    "Uno"
    "Dos"
    "Tres"
)

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Accessing Array Items

The items in an array are accessed using their index, or their position in the array. Consider the array:

$colors = "red", "yellow", "black", "blue"

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The indexes in PowerShell start at 0.

Brackets [ ] are used to access an item in an array. To access "black" in the $colors array, for example:

PS > $colors[2]
black

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Updating Array Items

Items can be updated — or changed – by utilizing indexes. To change the color yellow to brown, for example:

PS > $colors[1] = "brown"
PS > $colors
red
brown
black
blue

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Indexing

PowerShell offers flexibility when indexing items, such as:

• Multiple indexes: Separate indexes with commas to print multiple items.

PS > $colors[0,2]
red
black

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• Range operator ..: Prints all items between two indexes (inclusive).

Note: This syntax is inclusive since the stop index 3 is included.

PS > $colors[1..3]
brown
black
blue

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• Reverse range: Use range operator from a higher index to a lower index to print items in reverse order (inclusive).

Note: This syntax is inclusive since both the start and stop indexes, 2 and 1, are included.

PS > $colors[2..1]
black
brown

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• Negative indexes: Items are referenced in reverse order where the last item has an index of -1.

PS > $colors[-1]
blue

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Iteration

Each array object has a method called ForEach which can be utilized to perform the same action on each of its items. PowerShell defines the variable $PSItem or just underscore _ to refer to each item in the array.

PS > $colors.ForEach({ $PSItem.Length }) # $_.Length also works
3
5
5
4

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The example above is printing the length of each string of our colors array. red has a length of 3, brown is 5, and so on.

Array Operators

Addition Operator

The addition operator + concatenates – or combines – two arrays.

PS > $fibonacci_1 = 0, 1, 1
PS > $fibonacci_2 = 2, 3, 5
PS > $fibonacci_1 + $fibonacci_2
0
1
1
2
3
5

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Multiplication Operator

The multiplication operator * copies the array a specified number of times.

PS > $fibonacci_2 * 2
2
3
5
2
3
5

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Containment Operators

Containment operators check whether or not an item is in an array and returns a boolean.

-join

The -join operator combines the items in an array into a string separated by a character or a string. Consider the following example:

PS > $fibonacci = 0, 1, 1, 2, 3, 5
PS > $fibonacci = $fibonacci -join "->"
PS > $fibonacci
0->1->1->2->3->5
PS > $fibonacci.GetType().Name
String

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Strongly Typed Arrays

Types can be casted onto arrays to force each item in the array to adhere to that type.

PS > [String[]]$fruits = "apple", "banana", "kiwi"

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Objects Arrays

Arrays can hold objects.

$dogs_arr = @(
    [PSCustomObject]@{Name = 'Rufus'; Age = 10}
    [PSCustomObject]@{Name = 'Miku'; Age = 2}
)

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Each object in the array as well as its properties and methods can be accessed individually.

PS > $dogs_arr.ForEach({ $PSItem.Name + " is " + $PSItem.Age + " years old."})
Rufus is 10 years old.
Miku is 2 years old.

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Note: $PSItem can be replaced with its shorthand alias $_.