Common regex patterns in PowerShell - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if a string contains only digits using regex.

PowerShell

$string = "12345"
if ($string -match "^[1]$") {
    Write-Output "Only digits"
}

Drag options to blanks, or click blank then click option'

A\d+

B\w+

C\s+

D\D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using \w+ matches letters and digits, not digits only.

Using \s+ matches whitespace, not digits.

The pattern \d+ matches one or more digits. Anchors ^ and $ ensure the entire string is digits only.

2fill in blank

medium

Complete the code to find all words starting with a capital letter.

PowerShell

$text = "Hello World from PowerShell"
$matches = [regex]::Matches($text, "\b[1]\w*")
$matches | ForEach-Object { $_.Value }

Drag options to blanks, or click blank then click option'

A\d

B[a-z]

C[A-Z]

D\s

Attempts:

3 left

💡 Hint

Common Mistakes

Using [a-z] matches lowercase letters, not capital letters.

Using \d matches digits, not letters.

The pattern [A-Z] matches any uppercase letter at the start of a word boundary \b.

3fill in blank

hard

Fix the error in the regex pattern to match email addresses.

PowerShell

$email = "[e-mail]"
if ($email -match "^[\w.-]+@[1]\.[a-z]{2,}$") {
    Write-Output "Valid email"
}

Drag options to blanks, or click blank then click option'

A[\w-]+

B[\d]+

C[\s]+

D[A-Z]+

Attempts:

3 left

💡 Hint

Common Mistakes

Using [\d]+ matches only digits, not domain names.

Using [\s]+ matches spaces, invalid in emails.

The pattern [\w-]+ matches the domain part of the email (letters, digits, underscore, hyphen).

4fill in blank

hard

Fill both blanks to create a regex that matches a US phone number format (e.g., 123-456-7890).

PowerShell

$phone = "123-456-7890"
if ($phone -match "^[1]-[2]-\d{4}$") {
    Write-Output "Valid phone number"
}

Drag options to blanks, or click blank then click option'

A\d{3}

B\w{3}

C\d{4}

D\s{3}

Attempts:

3 left

💡 Hint

Common Mistakes

Using \w{3} matches letters and digits, not just digits.

Using \s{3} matches spaces, not digits.

The pattern \d{3} matches exactly three digits for the first two parts of the phone number.

5fill in blank

hard

Fill both blanks to create a regex that matches a hex color code (e.g., #1A2B3C).

PowerShell

$color = "#1A2B3C"
if ($color -match "^[1][2]$") {
    Write-Output "Valid hex color"
}

Drag options to blanks, or click blank then click option'

A#

B[0-9A-Fa-f]{6}

C[0-9A-Fa-f]

D[A-Fa-f0-9]{3}

Attempts:

3 left

💡 Hint

Common Mistakes

Using [A-Fa-f0-9]{3} matches only 3 digits, not 6.

Missing the # at the start.

The pattern starts with #, followed by 6 hex digits ([0-9A-Fa-f]{6}).

Practice

1. Which regex pattern matches any single digit from 0 to 9 in PowerShell?

easy

A. \d

B. \w

C. \s

D. \D

Solution

1. Step 1: Understand regex digit shorthand

   The pattern \d matches any single digit character (0-9) in regex.

2. Step 2: Compare other options

   \w matches word characters (letters, digits, underscore), \s matches whitespace, \D matches non-digit characters.

3. Final Answer:

   \d -> Option A

4. Quick Check:

   Digit shorthand = \d [OK]

Hint: Remember \d means digit, \w means word character [OK]

Common Mistakes:

• Confusing \d with \w or \s
• Using uppercase \D which means non-digit
• Thinking \w matches only letters

2. Which of the following is the correct PowerShell regex pattern to match a string that starts with 'abc'?

easy

A. abc*

B. abc$

C. ^abc

D. *abc

Solution

1. Step 1: Understand regex anchors

   The caret ^ matches the start of a string, so ^abc matches strings starting with 'abc'.

2. Step 2: Check other options

   abc$ matches strings ending with 'abc', abc* matches 'ab' followed by zero or more 'c's, *abc is invalid syntax.

3. Final Answer:

   ^abc -> Option C

4. Quick Check:

   Start anchor = ^abc [OK]

Hint: Use ^ at start to match beginning of string [OK]

Common Mistakes:

• Using $ instead of ^ for start of string
• Misunderstanding * as wildcard for any chars
• Placing * at start which is invalid

3. What will be the output of this PowerShell command?

$text = 'User123'
if ($text -match '\w{4}\d{3}') { 'Match' } else { 'No Match' }

medium

A. Match

B. No Match

C. Error

D. false

Solution

1. Step 1: Analyze the regex pattern

   \w{4} matches exactly 4 word characters, \d{3} matches exactly 3 digits. Together they match 7 characters: 4 word chars + 3 digits.

2. Step 2: Check the input string

   'User123' has 4 letters 'User' and 3 digits '123', so it matches the pattern.

3. Final Answer:

   Match -> Option A

4. Quick Check:

   4 letters + 3 digits = Match [OK]

Hint: Count characters to match {n} quantifiers exactly [OK]

Common Mistakes:

• Thinking \w includes only letters, ignoring digits
• Confusing {n} with * or + quantifiers
• Not escaping backslash properly in PowerShell string

4. Identify the error in this PowerShell regex usage:

$email = '[e-mail]'
if ($email -match '[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2}') { 'Valid' } else { 'Invalid' }

medium

A. Missing escape for dot before domain extension

B. Incorrect character class for username

C. Using single quotes prevents regex from working

D. Regex pattern is correct, no error

Solution

1. Step 1: Review regex pattern components

   The pattern matches username with allowed chars, an @, domain name, a literal dot (escaped), and domain extension of 2+ letters.

2. Step 2: Check PowerShell string usage

   Single quotes in PowerShell treat string literally, so \ is treated as a single backslash, correctly escaping the dot.

3. Final Answer:

   Regex pattern is correct, no error -> Option D

4. Quick Check:

   Proper escaping and pattern = Correct [OK]

Hint: Single quotes keep regex escapes intact in PowerShell [OK]

Common Mistakes:

• Thinking dot needs double escape in single quotes
• Assuming single quotes disable regex
• Misreading character classes as incorrect

5. You want to extract all words starting with a capital letter from a string in PowerShell. Which regex pattern should you use?

hard

A. \b[a-z][A-Z]*\b

B. \b[A-Z][a-z]*\b

C. [A-Z]+\b

D. \b[A-Z]+[0-9]*\b

Solution

1. Step 1: Understand the requirement

   We want words starting with a capital letter, followed by zero or more lowercase letters.

2. Step 2: Analyze each pattern

   A: \b[A-Z][a-z]*\b matches word boundary, one uppercase letter, then zero or more lowercase letters, then word boundary - correct.
   B: starts with lowercase letter, so incorrect.
   C: matches one or more uppercase letters but no word boundary start.
   D: matches uppercase letters followed by digits, not only letters.

3. Final Answer:

   \b[A-Z][a-z]*\b -> Option B

4. Quick Check:

   Capital start + lowercase letters = \b[A-Z][a-z]*\b [OK]

Hint: Use \b for word boundary and [A-Z] for capital start [OK]

Common Mistakes:

• Ignoring word boundaries causing partial matches
• Using [a-z][A-Z]* which starts with lowercase
• Including digits when only letters needed