Chapter 4: Conditional Statements

Master conditional statements in PowerShell, including if, else, and elseif, to control the flow of your script based on specific conditions.

Conditional statements allow PowerShell scripts to make decisions and execute code based on certain conditions. This chapter covers how to use if, else, and elseif statements to control the flow of your scripts, enabling more dynamic and responsive operations.

The If Statement

The if statement is used to test a condition. If the condition evaluates to $true, the code within the if block is executed. Here�s the basic structure:

if (condition) {
    # Code to execute if the condition is true
}

For example, the following code checks if a number is greater than 10:

$number = 15

if ($number -gt 10) {
    Write-Output "The number is greater than 10"
}

Since $number is 15, this condition is true, so the message will be displayed.

The Else Statement

The else statement provides an alternative action if the if condition is $false. It runs when the if condition is not met:

$number = 5

if ($number -gt 10) {
    Write-Output "The number is greater than 10"
} else {
    Write-Output "The number is 10 or less"
}

In this case, since $number is 5, the else block will execute and display the message �The number is 10 or less.�

The ElseIf Statement

The elseif statement allows you to test multiple conditions in sequence. If the initial if condition is $false, PowerShell checks the elseif conditions in order until one is $true:

$number = 10

if ($number -gt 10) {
    Write-Output "The number is greater than 10"
} elseif ($number -eq 10) {
    Write-Output "The number is exactly 10"
} else {
    Write-Output "The number is less than 10"
}

Here, since $number is exactly 10, the elseif condition will be met, and �The number is exactly 10� will be displayed.

Using Comparison Operators

PowerShell provides several comparison operators to test conditions in if statements:

-eq: Equal to
-ne: Not equal to
-gt: Greater than
-lt: Less than
-ge: Greater than or equal to
-le: Less than or equal to

These operators allow you to evaluate a wide range of conditions and make your scripts highly flexible.

Logical Operators for Complex Conditions

Logical operators can combine multiple conditions within an if statement, making it possible to create complex decision-making structures:

-and: Returns $true if both conditions are true.
-or: Returns $true if at least one condition is true.
-not: Reverses the condition�s result.

For example, to check if a number is between 5 and 15:

$number = 10

if ($number -ge 5 -and $number -le 15) {
    Write-Output "The number is between 5 and 15"
}

Nested If Statements

You can place if statements within other if statements, known as nesting. This is useful for checking multiple conditions sequentially:

$age = 20
$hasPermission = $true

if ($age -ge 18) {
    if ($hasPermission) {
        Write-Output "Access granted."
    } else {
        Write-Output "Permission required."
    }
} else {
    Write-Output "Must be at least 18 years old."
}

In this example, access is granted only if both age and permission conditions are met.

The Switch Statement

The switch statement provides an alternative to if when you need to evaluate a variable against multiple values. This can make code cleaner when checking a single variable against various options:

$day = "Monday"

switch ($day) {
    "Monday" { Write-Output "Start of the week" }
    "Friday" { Write-Output "Almost weekend" }
    default { Write-Output "Just another day" }
}

Here, if $day is �Monday,� it outputs �Start of the week�; if �Friday,� it outputs �Almost weekend�; otherwise, it outputs �Just another day.�

Summary and Next Steps

In this chapter, we covered conditional statements in PowerShell, including if, else, elseif, and switch. We explored comparison and logical operators to help create flexible conditions. In the next chapter, we�ll look at loops and iteration, which allow you to automate repetitive tasks within your scripts.