Where-Object for filtering in PowerShell - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of filtering numbers greater than 5

What is the output of this PowerShell command?

1..10 | Where-Object { $_ -gt 5 }

PowerShell

1..10 | Where-Object { $_ -gt 5 }

A

6
7
8
9
10

B

1
2
3
4
5
6

C

5
6
7
8
9
10

D

1
2
3
4
5

💡 Hint

Remember, Where-Object filters items where the condition is true.

The command filters numbers from 1 to 10, keeping only those greater than 5, which are 6 to 10.

💻 Command Output

intermediate

Filtering strings containing 'a'

What is the output of this PowerShell command?

@('apple','banana','cherry','date') | Where-Object { $_ -like '*a*' }

PowerShell

@('apple','banana','cherry','date') | Where-Object { $_ -like '*a*' }

A

banana
cherry
date

B

apple
banana
date

C

apple
cherry

D

cherry
date

💡 Hint

The -like operator checks if the string contains the pattern.

Strings containing the letter 'a' are 'apple', 'banana', and 'date'.

📝 Syntax

advanced

Identify the syntax error in filtering

Which option contains a syntax error in using Where-Object to filter even numbers from 1 to 5?

PowerShell

1..5 | Where-Object { $_ % 2 -eq 0 }

A 1..5 | Where-Object { $_ % 2 = 0 }

B } 0 qe- 2 % _$ { tcejbO-erehW | 5..1

C 1..5 | Where-Object { $_ % 2 -eq 0 }

D ..5 | Where-Object { $_ % 2 -eq 0 }

💡 Hint

Check the operator used for comparison.

Option A uses '=' which is assignment, not comparison, causing a syntax error.

🔧 Debug

advanced

Why does this filter return no results?

Given this command:

@('cat','dog','bird') | Where-Object { $_ -ceq 'Cat' }

Why does it return no output?

PowerShell

@('cat','dog','bird') | Where-Object { $_ -ceq 'Cat' }

A Because -ceq operator is invalid here

B Because the array is empty

C Because PowerShell -ceq string comparison is case-sensitive

D Because the script block is missing a return statement

💡 Hint

Check the case sensitivity of the comparison operator used.

PowerShell's -ceq operator performs case-sensitive string comparisons, so 'cat' does not match 'Cat'.

🚀 Application

expert

Filter processes using Where-Object with multiple conditions

Which command filters processes with CPU usage greater than 100 and process name starting with 's' (case-insensitive)?

A Get-Process | Where-Object { $_.CPU -gt 100 -and $_.Name -like 's*' }

B Get-Process | Where-Object { $_.CPU -gt 100 -or $_.Name -ilike 's*' }

C Get-Process | Where-Object { $_.CPU > 100 -and $_.Name -like 's*' }

D Get-Process | Where-Object { $_.CPU -gt 100 -and $_.Name -ilike 's*' }

💡 Hint

Use the correct operator for case-insensitive matching and logical AND.

Option D uses '-ilike' for case-insensitive matching and '-and' for combining conditions correctly.

Practice

1. What does the Where-Object cmdlet do in PowerShell?

easy

A. Filters objects in a collection based on a condition

B. Sorts objects alphabetically

C. Creates new objects from existing ones

D. Deletes objects from a collection

Solution

1. Step 1: Understand the purpose of Where-Object

   Where-Object is used to filter items in a collection by applying a condition to each item.

2. Step 2: Compare options with the purpose

   Only Filters objects in a collection based on a condition correctly describes filtering based on a condition. Sorting, creating, or deleting are different operations.

3. Final Answer:

   Filters objects in a collection based on a condition -> Option A

4. Quick Check:

   Where-Object filters collections = A [OK]

Hint: Where-Object selects items matching a condition [OK]

Common Mistakes:

• Confusing filtering with sorting
• Thinking it creates or deletes objects
• Ignoring the condition part

2. Which of the following is the correct syntax to filter processes with CPU usage greater than 100 using Where-Object?

easy

A. Get-Process | Where-Object { CPU > 100 }

B. Get-Process | Where-Object { $_.CPU -gt 100 }

C. Get-Process | Where-Object CPU -gt 100

D. Get-Process | Where-Object CPU > 100

Solution

1. Step 1: Identify correct use of script block and $_ variable

   Where-Object requires a script block with curly braces and uses $_ to refer to the current object.

2. Step 2: Check each option's syntax

   Get-Process | Where-Object { $_.CPU -gt 100 } correctly uses { $_.CPU -gt 100 }. Versions without the script block braces {} are incorrect. The version with { CPU > 100 } misses $_ before CPU.

3. Final Answer:

   Get-Process | Where-Object { $_.CPU -gt 100 } -> Option B

4. Quick Check:

   { $_.Property -gt value } syntax = D [OK]

Hint: Always use { $_.Property -operator value } inside Where-Object [OK]

Common Mistakes:

• Omitting curly braces {}
• Not using $_ to reference current object
• Writing condition outside script block

3. What will be the output of this command?

1..5 | Where-Object { $_ % 2 -eq 0 }

medium

A. [1, 3, 5]

B. [1, 2, 3, 4, 5]

C. [2, 4]

D. Error: Invalid operator

Solution

1. Step 1: Understand the input and condition

   The input is numbers 1 to 5. The condition filters numbers where remainder when divided by 2 equals 0 (even numbers).

2. Step 2: Apply the condition to each number

   Numbers 2 and 4 satisfy the condition (2 % 2 = 0, 4 % 2 = 0). Others do not.

3. Final Answer:

   [2, 4] -> Option C

4. Quick Check:

   Filter even numbers = [2, 4] [OK]

Hint: Use modulo (%) to filter even numbers [OK]

Common Mistakes:

• Confusing even and odd numbers
• Expecting all numbers as output
• Thinking syntax causes error

4. Identify the error in this command:

Get-Service | Where-Object $_.Status -eq 'Running'

medium

A. Missing curly braces around the condition

B. Incorrect property name 'Status'

C. Wrong operator used for comparison

D. No error, command is correct

Solution

1. Step 1: Check Where-Object syntax

   Where-Object requires the condition inside curly braces {} to form a script block.

2. Step 2: Analyze the given command

   The command misses curly braces around $_.Status -eq 'Running', causing syntax error.

3. Final Answer:

   Missing curly braces around the condition -> Option A

4. Quick Check:

   Where-Object needs { condition } [OK]

Hint: Always wrap condition in { } for Where-Object [OK]

Common Mistakes:

• Omitting curly braces
• Assuming property names are wrong without checking
• Confusing operators

5. You have a list of files with sizes in bytes. Which command filters files larger than 1MB (1048576 bytes) and selects only their names?

Get-ChildItem | Where-Object { $_.Length -gt 1048576 } | ???

What should replace ????

hard

A. Sort-Object Length

B. Where-Object Name

C. Format-Table Length

D. Select-Object Name

Solution

1. Step 1: Understand the filtering part

   Where-Object filters files with Length greater than 1048576 bytes (1MB).

2. Step 2: Identify how to select only file names

   Select-Object Name extracts only the Name property from the filtered files.

3. Final Answer:

   Select-Object Name -> Option D

4. Quick Check:

   Select-Object Name for properties = C [OK]

Hint: Use Select-Object to pick specific properties [OK]

Common Mistakes:

• Using Where-Object instead of Select-Object to pick properties
• Sorting instead of selecting
• Formatting output without selecting needed data