If-elseif-else statements in PowerShell

Introduction

If-elseif-else statements help your script make choices. They run different code based on conditions.

Check if a file exists and do something if it does or doesn't.

Decide what message to show based on a user's input.

Run different commands depending on the time of day.

Choose an action based on a number's value.

Syntax

PowerShell

if (<condition1>) {
    # code to run if condition1 is true
} elseif (<condition2>) {
    # code to run if condition2 is true
} else {
    # code to run if none of the above conditions are true
}

Conditions are expressions that result in True or False.

Use elseif for multiple checks after the first if.

Examples

This checks age and prints a message for adult, teenager, or child.

PowerShell

if ($age -ge 18) {
    Write-Output "You are an adult."
} elseif ($age -ge 13) {
    Write-Output "You are a teenager."
} else {
    Write-Output "You are a child."
}

This assigns a grade based on the score value.

PowerShell

if ($score -ge 90) {
    Write-Output "Grade: A"
} elseif ($score -ge 80) {
    Write-Output "Grade: B"
} elseif ($score -ge 70) {
    Write-Output "Grade: C"
} else {
    Write-Output "Grade: F"
}

Sample Program

This script checks the temperature and prints a message about the weather.

PowerShell

$temperature = 75

if ($temperature -ge 85) {
    Write-Output "It's hot outside."
} elseif ($temperature -ge 65) {
    Write-Output "The weather is nice."
} else {
    Write-Output "It's cold outside."
}

Important Notes

PowerShell uses -ge for 'greater than or equal to' in conditions.

Always use curly braces { } to group the code for each condition.

Summary

If-elseif-else lets your script choose what to do based on conditions.

Use if for the first check, elseif for extra checks, and else for the default case.

Conditions must be true or false expressions.

Practice

1. What does an if-elseif-else statement do in PowerShell?

easy

A. It chooses which code to run based on conditions.

B. It repeats code multiple times.

C. It stores data in variables.

D. It defines a function.

Solution

1. Step 1: Identify the purpose of if-elseif-else

   An if-elseif-else statement checks conditions and runs code based on which condition is true. This matches "It chooses which code to run based on conditions."

2. Final Answer:

   It chooses which code to run based on conditions. -> Option A

3. Quick Check:

   if-elseif-else controls flow by conditions = B [OK]

Hint: If it picks code based on true/false, it's if-elseif-else [OK]

Common Mistakes:

• Confusing if-elseif-else with loops
• Thinking it stores data
• Mixing it up with function definitions

2. Which of the following is the correct syntax to start an if statement in PowerShell?

easy

A. if $x == 5 then { }

B. if ( $x -eq 5 ) { }

C. if $x = 5 { }

D. if $x equals 5 { }

Solution

1. Step 1: Recall PowerShell if syntax and verify options

   PowerShell uses if (condition) { code } with -eq for equality check. "if ( $x -eq 5 ) { }" uses correct parentheses, -eq operator, and braces. Others use wrong operators or keywords.

2. Final Answer:

   if ( $x -eq 5 ) { } -> Option B

3. Quick Check:

   PowerShell if: parens + -eq = A [OK]

Hint: Use parentheses and -eq for conditions in if [OK]

Common Mistakes:

• Using == instead of -eq
• Omitting parentheses
• Using = for comparison

3. What will this PowerShell code output?

 $num = 7
if ($num -lt 5) {
  'Less than 5'
} elseif ($num -eq 7) {
  'Equal to 7'
} else {
  'Other'
}

medium

A. Equal to 7

B. No output

C. Other

D. Less than 5

Solution

1. Step 1: Trace code execution step-by-step

   $num is 7, ($num -lt 5) is false. ($num -eq 7) is true, outputs 'Equal to 7'.

2. Final Answer:

   Equal to 7 -> Option A

3. Quick Check:

   7 -eq 7 triggers elseif = D [OK]

Hint: Check conditions top to bottom, first true runs [OK]

Common Mistakes:

• Choosing first if block without checking condition
• Ignoring elseif block
• Assuming else runs always

4. Find the error in this PowerShell snippet:

if $value -gt 10 {
  'Greater than 10'
} elseif ($value -eq 10) {
  'Equal to 10'
} else {
  'Less than 10'
}

medium

A. Braces {} are not allowed

B. Using -gt instead of >

C. Missing else keyword

D. Missing parentheses around first if condition

Solution

1. Step 1: Check syntax and identify the error

   PowerShell requires parentheses around the condition in if statements. The first if lacks them: "if $value -gt 10 {" should be "if ($value -gt 10) {". Matches "Missing parentheses around first if condition".

2. Final Answer:

   Missing parentheses around first if condition -> Option D

3. Quick Check:

   All if conditions need parentheses = A [OK]

Hint: Always put conditions inside parentheses in if [OK]

Common Mistakes:

• Omitting parentheses in if
• Confusing -gt with > (both valid but -gt preferred)
• Forgetting else keyword

5. You want to write a script that prints:
- 'Cold' if temperature is below 10,
- 'Warm' if temperature is between 10 and 25 inclusive,
- 'Hot' if temperature is above 25.
Which if-elseif-else structure correctly implements this?

hard

A. if ($temp -lt 10) { 'Cold' } elseif ($temp -ge 25) { 'Hot' } else { 'Warm' }

B. if ($temp -le 10) { 'Cold' } elseif ($temp -lt 25) { 'Warm' } else { 'Hot' }

C. if ($temp -lt 10) { 'Cold' } elseif ($temp -le 25) { 'Warm' } else { 'Hot' }

D. if ($temp -gt 25) { 'Hot' } elseif ($temp -gt 10) { 'Warm' } else { 'Cold' }

Solution

1. Step 1: Analyze temperature ranges and verify conditions

   Cold: below 10, Warm: 10-25 inclusive, Hot: above 25. "if ($temp -lt 10) { 'Cold' } elseif ($temp -le 25) { 'Warm' } else { 'Hot' }": <10=Cold, <=25=Warm (10-25), else Hot. Matches exactly.

2. Final Answer:

   if ($temp -lt 10) { 'Cold' } elseif ($temp -le 25) { 'Warm' } else { 'Hot' } -> Option C

3. Quick Check:

   Ranges covered correctly = C [OK]

Hint: Order conditions from smallest to largest range [OK]

Common Mistakes:

• Mixing up less than and less or equal
• Wrong order causing wrong output
• Overlapping or missing ranges