Chapter 3: Variables and Data Types

Explore PowerShell variables, data types, and how to manage and use variables to store and manipulate data effectively within your scripts.

Variables are essential in PowerShell for storing data and managing information across scripts. PowerShell variables can store text, numbers, objects, arrays, and more, allowing you to manipulate and retrieve data efficiently. This chapter covers how to create and use variables, and introduces common data types.

Creating and Using Variables in PowerShell

In PowerShell, variables are created by prefixing a name with a dollar sign $. There’s no need to declare a data type explicitly, as PowerShell automatically assigns it based on the data stored:

$name = "John Doe"
$age = 30
$isEmployee = $true

In this example, $name is a string, $age is an integer, and $isEmployee is a Boolean variable.

Variable Naming Conventions and Rules

Variable names in PowerShell are case-insensitive and can contain letters, numbers, and underscores. However, they cannot start with a number. Following naming conventions, such as using descriptive names, helps make scripts readable and maintainable.

For example:

$FirstName = "Alice"
$TotalSales = 5000

Common Data Types in PowerShell

PowerShell supports various data types to suit different needs. Here are some common data types:

String: Stores text, such as "Hello, World!".
Integer: Stores whole numbers, such as 42.
Boolean: Stores $true or $false values.
Array: Stores multiple values in a single variable, such as @(1, 2, 3).
Hashtable: Stores key-value pairs, such as @{key1="value1"; key2="value2"}.

Working with Strings

Strings are one of the most common data types, storing text values. You can concatenate strings using the + operator:

$greeting = "Hello, " + $name

PowerShell also supports string interpolation, allowing you to embed variable values directly within a string by using double quotes:

$greeting = "Hello, $name!"

Arrays and Array Operations

Arrays allow you to store multiple values in a single variable. To create an array, use the @() syntax:

$numbers = @(1, 2, 3, 4, 5)

You can access elements in an array by index, starting at 0. For example, $numbers[0] retrieves the first element.

Using Hashtables for Key-Value Pairs

Hashtables store data in key-value pairs, which makes them ideal for storing related information. To create a hashtable, use the @{} syntax:

$person = @{
    Name = "Alice"
    Age = 30
    Department = "Sales"
}

You can retrieve values by referencing their keys, such as $person["Name"], which would return “Alice.”

Data Type Conversion

PowerShell allows you to convert between data types. To cast a variable to a specific data type, place the desired type in square brackets before the value:

$numberAsString = "42"
$number = [int]$numberAsString

This converts the string "42" into an integer. Proper type conversion helps avoid errors in mathematical or logical operations.

Scope of Variables

Variable scope defines where a variable is accessible within your script. PowerShell supports several scopes:

Global: Variables available throughout the session.
Local: Variables available only within the current script or function.
Script: Variables available throughout a script file.

Use scope to control variable visibility and prevent conflicts in complex scripts.

Summary and Next Steps

In this chapter, we explored PowerShell variables, common data types, arrays, and hashtables. We also covered data type conversion and variable scope, which are essential for managing data in PowerShell scripts. In the next chapter, we’ll build on this knowledge with conditional statements, enabling more dynamic and responsive scripts.