Regex with Select-String in PowerShell - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of Select-String with simple regex

What is the output of this PowerShell command when run on a file containing the lines:

apple
banana
apricot
grape

Command:

Select-String -Pattern '^a' -Path 'fruits.txt'

PowerShell

Select-String -Pattern '^a' -Path 'fruits.txt'

A apple<br>banana<br>apricot<br>grape

B banana<br>grape

C apple<br>apricot

D No output

💡 Hint

The regex '^a' matches lines starting with 'a'.

The pattern '^a' matches lines that start with the letter 'a'. In the file, 'apple' and 'apricot' start with 'a', so Select-String outputs those lines.

💻 Command Output

intermediate

Select-String with case-insensitive regex

Given a file 'colors.txt' with lines:

Red
blue
GREEN
Yellow

What is the output of:

Select-String -Pattern 'green' -Path 'colors.txt' -CaseSensitive:$false

PowerShell

Select-String -Pattern 'green' -Path 'colors.txt' -CaseSensitive:$false

A GREEN

B green

C No output

D Red

💡 Hint

CaseSensitive:$false makes the search ignore case.

The pattern 'green' matches 'GREEN' ignoring case because CaseSensitive is set to false. So the output is the line 'GREEN'.

📝 Syntax

advanced

Identify the correct regex pattern syntax in Select-String

Which option correctly matches lines containing exactly three digits in a row using Select-String?

PowerShell

Select-String -Pattern '<pattern>' -Path 'numbers.txt'

A [0-9]{3}

B \d{3}

C }3{d\

D \d{,3}

💡 Hint

Use character classes and quantifiers correctly.

Option A '[0-9]{3}' matches exactly three digits in a row. Option A is invalid in PowerShell because '\d' is not recognized as a digit shorthand in Select-String regex. Option A matches three or more digits, and D is invalid syntax.

🔧 Debug

advanced

Why does this Select-String command fail?

You run this command:

Select-String -Pattern '\w+@\w+\.com' -Path 'emails.txt'

But it returns no matches even though the file contains emails like '[e-mail]'. Why?

PowerShell

Select-String -Pattern '\w+@\w+\.com' -Path 'emails.txt'

A Because the file path is incorrect

B Because '\w' is not supported in PowerShell regex, use '[a-zA-Z0-9_]' instead

C Because the pattern needs single quotes instead of double quotes

D Because Select-String does not support regex

💡 Hint

Check if '\w' is recognized in PowerShell regex.

PowerShell's Select-String uses .NET regex which supports '\w', but in PowerShell strings, '\w' needs to be escaped properly or replaced with '[a-zA-Z0-9_]'. Using '\w' inside single quotes is safer. The issue is usually the escape sequence in the string, not the regex itself.

🚀 Application

expert

Extracting matched text with Select-String and regex groups

You want to extract only the domain part from email addresses in 'emails.txt' using Select-String with regex groups. Which command correctly outputs just the domain (e.g., 'example.com')?

PowerShell

Select-String -Pattern '<pattern>' -Path 'emails.txt' | ForEach-Object { <extract> }

A Select-String -Pattern '^[\w.-]+@([\w.-]+)$' -Path 'emails.txt' | ForEach-Object { $_.Matches.Groups[1].Value }

B Select-String -Pattern '^[\w.-]+@([\w.-]+)$' -Path 'emails.txt' | ForEach-Object { $_.Groups[1].Value }

C Select-String -Pattern '^[\w.-]+@([\w.-]+)$' -Path 'emails.txt' | ForEach-Object { $_.Matches[1].Groups[0].Value }

D Select-String -Pattern '^[\w.-]+@([\w.-]+)$' -Path 'emails.txt' | ForEach-Object { $_.Matches[0].Groups[1].Value }

💡 Hint

Check how to access regex groups from Select-String Matches property.

In PowerShell, Select-String returns MatchInfo objects with a Matches collection. Each Match has Groups. The first match is at index 0, and the first group is at Groups[1]. So $_.Matches[0].Groups[1].Value extracts the domain part.