Parameters in PowerShell - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a parameter in a PowerShell script?

A parameter is a way to pass information into a PowerShell script or function so it can use that information to do its work.

beginner

How do you define a parameter in a PowerShell script?

You define parameters inside a param() block at the start of the script or function.

intermediate

What is the purpose of specifying a parameter type in PowerShell?

Specifying a type helps PowerShell check that the input is the right kind of data, like a number or text, making scripts safer and clearer.

intermediate

How can you make a parameter optional in PowerShell?

You can make a parameter optional by not marking it as mandatory. You can also provide a default value so the script uses that if no input is given.

intermediate

What does the [switch] parameter type do in PowerShell?

A [switch] parameter acts like a simple on/off flag. If you include it when running the script, it is true; if you leave it out, it is false.

Where do you place the param() block in a PowerShell script?

A At the very start of the script

B Anywhere in the middle of the script

C Only inside functions

D At the end of the script

The param() block must be at the start of the script or function to define parameters properly.

What happens if you run a script with a mandatory parameter but do not provide it?

A The script ignores the parameter

B The script runs with a default value

C PowerShell asks you to enter the value

D The script crashes without message

PowerShell prompts you to enter a value for mandatory parameters if you don't provide one.

How do you define a parameter with a default value in PowerShell?

A <code>param([string]$name = 'Guest')</code>

B <code>param([string]$name?)</code>

C <code>param([string]$name!)</code>

D <code>param([string]$name*)</code>

You assign a default value using the equals sign inside the param block.

What type of parameter is best for a simple on/off option?

A [int]

B [switch]

C [bool]

D [string]

The [switch] type is designed for on/off flags without needing to specify true or false explicitly.

Which of these is a correct way to declare a mandatory parameter?

A <code>[Parameter(Required)] [string]$Name</code>

B <code>[Mandatory] [string]$Name</code>

C <code>[string]$Name = Mandatory</code>

D <code>[Parameter(Mandatory=$true)] [string]$Name</code>

The correct syntax uses the Parameter attribute with Mandatory=$true.

Explain how to create a PowerShell script that accepts a mandatory string parameter and an optional integer parameter with a default value.

Think about using [Parameter(Mandatory=$true)] and assigning a default value with =

Describe the difference between a [switch] parameter and a boolean parameter in PowerShell.

Consider how you use them when calling the script.

Practice

1. What is the purpose of using param() in a PowerShell script?

easy

A. To declare input parameters that the script can accept

B. To define a function inside the script

C. To output results from the script

D. To comment lines in the script

Solution

1. Step 1: Understand the role of param()

   The param() block is used at the start of a PowerShell script to declare parameters that the script can accept as input.

2. Step 2: Differentiate from other script parts

   It is not used to define functions, output results, or comment lines. Those have different syntax and purposes.

3. Final Answer:

   To declare input parameters that the script can accept -> Option A

4. Quick Check:

   param() declares input parameters [OK]

Hint: Remember: param() is for input, not output or comments [OK]

Common Mistakes:

• Confusing param() with function declaration
• Thinking param() outputs data
• Using param() to comment code

2. Which of the following is the correct syntax to declare a mandatory string parameter named Name in PowerShell?

easy

A. param([string]$Name = "")

B. param([string]$Name)

C. param($Name:string Mandatory)

D. param([Parameter(Mandatory=$true)][string]$Name)

Solution

1. Step 1: Understand mandatory parameter syntax

   To make a parameter mandatory, use the [Parameter(Mandatory=$true)] attribute before the type and name.

2. Step 2: Check each option

   param([Parameter(Mandatory=$true)][string]$Name) correctly uses [Parameter(Mandatory=$true)][string]$Name. param([string]$Name = "") sets a default empty string, so not mandatory. param([string]$Name) lacks the mandatory attribute. param($Name:string Mandatory) is invalid syntax.

3. Final Answer:

   param([Parameter(Mandatory=$true)][string]$Name) -> Option D

4. Quick Check:

   Mandatory parameter needs [Parameter(Mandatory=$true)] [OK]

Hint: Mandatory parameters use [Parameter(Mandatory=$true)] attribute [OK]

Common Mistakes:

• Omitting the Mandatory attribute
• Using default value instead of mandatory
• Incorrect attribute syntax

3. What will be the output of this script when run with -Count 3?

param([int]$Count = 1)
for ($i = 1; $i -le $Count; $i++) { Write-Output "Number $i" }

medium

A. Number 1
Number 2
Number 3

B. Number 1

C. Number 3

D. Error: Missing parameter

Solution

1. Step 1: Understand parameter default and input

   The parameter $Count has a default of 1 but is overridden by passing -Count 3.

2. Step 2: Trace the loop output

   The for loop runs from 1 to 3, outputting "Number 1", "Number 2", and "Number 3" each on a new line.

3. Final Answer:

   Number 1 Number 2 Number 3 -> Option A

4. Quick Check:

   Loop runs 3 times with Count=3 [OK]

Hint: Parameter overrides default; loop runs Count times [OK]

Common Mistakes:

• Ignoring passed parameter and using default
• Expecting single output instead of looped output
• Confusing parameter name or type

4. Identify the error in this parameter declaration:

param([int]$Age = "twenty")

medium

A. Missing mandatory attribute

B. Type mismatch: assigning string to int parameter

C. Parameter name cannot be Age

D. Default value must be null

Solution

1. Step 1: Check parameter type and default value

   The parameter $Age is declared as [int] but the default value is the string "twenty".

2. Step 2: Understand type mismatch error

   PowerShell cannot convert the string "twenty" to an integer, causing a type mismatch error.

3. Final Answer:

   Type mismatch: assigning string to int parameter -> Option B

4. Quick Check:

   Default value must match parameter type [OK]

Hint: Default values must match declared parameter type [OK]

Common Mistakes:

• Assigning string default to int parameter
• Ignoring type mismatch errors
• Assuming parameter name restrictions

5. You want to create a script that accepts two parameters: Path (string, mandatory) and Verbose (switch, optional). Which is the correct way to declare these parameters?

hard

A. param([string]$Path, [Parameter(Mandatory=$true)][switch]$Verbose)

B. param([string]$Path = "", [switch]$Verbose = $false)

C. param([Parameter(Mandatory=$true)][string]$Path, [switch]$Verbose)

D. param([switch]$Path, [string]$Verbose)

Solution

1. Step 1: Identify mandatory and optional parameters

   Path must be mandatory string, so use [Parameter(Mandatory=$true)][string]$Path. Verbose is an optional switch, so [switch]$Verbose without mandatory attribute.

2. Step 2: Evaluate each option

   param([Parameter(Mandatory=$true)][string]$Path, [switch]$Verbose) correctly declares Path as mandatory string and Verbose as optional switch. param([string]$Path, [Parameter(Mandatory=$true)][switch]$Verbose) wrongly makes Verbose mandatory. param([string]$Path = "", [switch]$Verbose = $false) sets default empty string for Path, so not mandatory. param([switch]$Path, [string]$Verbose) swaps types incorrectly.

3. Final Answer:

   param([Parameter(Mandatory=$true)][string]$Path, [switch]$Verbose) -> Option C

4. Quick Check:

   Mandatory string + optional switch = param([Parameter(Mandatory=$true)][string]$Path, [switch]$Verbose) [OK]

Hint: Mandatory uses [Parameter(Mandatory=$true)], switches don't [OK]

Common Mistakes:

• Making switches mandatory
• Setting default values instead of mandatory
• Mixing parameter types