Regular expressions with -match in PowerShell - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this PowerShell code using -match?

Consider this PowerShell snippet:

$text = 'Hello123'

if ($text -match '\d{3}$') { 'Match found' } else { 'No match' }

What will it output?

PowerShell

$text = 'Hello123'
if ($text -match '\d{3}$') { 'Match found' } else { 'No match' }

A Match found

B No match

C True

D False

💡 Hint

Check if the string ends with exactly three digits.

The regex '\d{3}$' looks for exactly three digits at the end of the string. 'Hello123' ends with '123', so it matches.

📝 Syntax

intermediate

Which option correctly uses -match to check for a word starting with 'a'?

Which PowerShell command correctly checks if the variable $word starts with the letter 'a'?

A $word -match '[a]'

B $word -match 'a$'

C $word -match '^a'

D $word -match 'a*'

💡 Hint

Use the caret ^ to match the start of a string.

Regex '^a' matches strings starting with 'a'. Option C matches strings ending with 'a'. Option C matches zero or more 'a's anywhere. Option C matches any string containing 'a'.

🔧 Debug

advanced

Why does this -match expression fail to find a match?

Given this code:

$input = 'User-01'

if ($input -match '\w+\d+') { 'Found' } else { 'Not found' }

It outputs 'Not found'. Why?

A Because -match is case sensitive and input has uppercase letters

B Because '\w+' matches letters and digits but the pattern expects digits immediately after letters without hyphen

C Because the backslashes are not escaped properly in the string

D Because the regex is missing anchors ^ and $

💡 Hint

Think about what '\w+' matches and the actual string structure.

The pattern '\w+\d+' expects one or more word characters followed immediately by one or more digits. 'User-01' has a hyphen between letters and digits, so the digits are not immediately after letters, causing no match.

🚀 Application

advanced

Which command extracts the first email from a string using -match?

You have this string:

$text = 'Contact us at [e-mail] or [e-mail].'

Which command extracts the first email address correctly?

A $text -match '[\w.-]+@[\w.-]+\.\w{2,}'; $matches[0]

B $text -match '[\w.-]+@[\w.-]+\.\w{2,}'; $matches[1]

C $text -match '\b[\w.-]+@[\w.-]+\.\w{2,}\b'; $matches[1]

D $text -match '\b[\w.-]+@[\w.-]+\.\w{2,}\b'; $matches[0]

💡 Hint

Remember the automatic variable $matches stores the matched text at index 0.

Option D uses word boundaries and captures the first email correctly. $matches[0] contains the matched string. Other options use wrong indices or miss word boundaries.

🧠 Conceptual

expert

What is the value of $matches after this -match operation?

Run this code:

$string = 'Order #12345 placed'

$string -match 'Order #(\d+)'

What is the value of $matches?

A @{0='Order #12345'; 1='12345'}

B @{0='12345'; 1='Order #12345'}

C @{0='Order #'; 1='12345'}

D @{0='Order #12345'; 1='#12345'}

💡 Hint

The first element is the full match, the next elements are capture groups.

$matches[0] holds the entire matched string 'Order #12345'. $matches[1] holds the first captured group '12345'.

Practice

1. What does the -match operator do in PowerShell?

easy

A. Converts a string to uppercase

B. Replaces text in a string

C. Splits a string into an array

D. Checks if a string fits a pattern using regular expressions

Solution

1. Step 1: Understand the purpose of -match

   The -match operator is used to test if a string matches a regular expression pattern.

2. Step 2: Compare with other string operations

   Replacing text uses -replace, splitting uses -split, and uppercase conversion uses ToUpper(). These are different from -match.

3. Final Answer:

   Checks if a string fits a pattern using regular expressions -> Option D

4. Quick Check:

   -match = pattern check [OK]

Hint: Remember: -match means 'does it fit the pattern?' [OK]

Common Mistakes:

• Confusing -match with -replace or -split
• Thinking -match changes the string
• Assuming -match returns the matched text directly

2. Which of the following is the correct syntax to check if the variable $text contains the word 'hello' using -match?

easy

A. if ($text contains 'hello')

B. match $text 'hello'

C. $text -match 'hello'

D. $text =~ 'hello'

Solution

1. Step 1: Recall PowerShell -match syntax

   The correct syntax is $variable -match 'pattern' to test if the variable matches the pattern.

2. Step 2: Evaluate each option

   $text -match 'hello' uses the correct syntax. match $text 'hello' is invalid syntax. $text =~ 'hello' uses a Bash-like operator, not PowerShell. if ($text contains 'hello') uses a wrong operator for matching.

3. Final Answer:

   $text -match 'hello' -> Option C

4. Quick Check:

   Correct syntax = $text -match 'hello' [OK]

Hint: Use $var -match 'pattern' to test matches [OK]

Common Mistakes:

• Using Bash or other language operators like =~
• Writing match before the variable
• Using 'contains' instead of -match

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

$text = 'My phone number is 123-456-7890'
if ($text -match '\d{3}-\d{3}-\d{4}') {
  $matches[0]
} else {
  'No match'
}

medium

A. No match

B. 123-456-7890

C. \d{3}-\d{3}-\d{4}

D. My phone number is 123-456-7890

Solution

1. Step 1: Understand the regex pattern

   The pattern \d{3}-\d{3}-\d{4} matches a phone number format with three digits, a dash, three digits, a dash, and four digits.

2. Step 2: Check if the string matches and what $matches[0] contains

   The string contains '123-456-7890' which matches the pattern. $matches[0] holds the matched substring, so it outputs '123-456-7890'.

3. Final Answer:

   123-456-7890 -> Option B

4. Quick Check:

   Regex match found = matched text [OK]

Hint: Matched text is in $matches[0] after -match success [OK]

Common Mistakes:

• Expecting the whole string instead of matched part
• Confusing $matches with the pattern string
• Not escaping backslashes properly

4. Identify the error in this PowerShell snippet:

$text = 'Error code: 404'
if ($text -match '\d{3}') {
  Write-Output $matches
}

medium

A. You must use $matches[0] to get the matched string

B. The regex pattern is invalid

C. $matches is an automatic variable, no error here

D. You need to use -like instead of -match

Solution

1. Step 1: Understand $matches variable usage

   $matches is a hashtable holding matched groups. To get the matched string, you must access $matches[0].

2. Step 2: Analyze the code output

   Using Write-Output $matches prints the whole hashtable, not the matched string. To print the matched text, use Write-Output $matches[0].

3. Final Answer:

   You must use $matches[0] to get the matched string -> Option A

4. Quick Check:

   Print matched text with $matches[0] [OK]

Hint: Use $matches[0] to print matched text, not $matches alone [OK]

Common Mistakes:

• Printing $matches directly instead of $matches[0]
• Thinking $matches is a string, not a hashtable
• Confusing -match with -like operator

5. You want to extract all email addresses from a list of strings stored in $lines. Which PowerShell snippet correctly uses -match and $matches to collect emails into $emails?

hard

A. $emails = foreach ($line in $lines) { if ($line -match '[\w.-]+@[\w.-]+\.\w+') { $matches[0] } }

B. $emails = $lines -match '[\w.-]+@[\w.-]+\.\w+'

C. $emails = $lines | Where-Object { $_ -contains '[\w.-]+@[\w.-]+\.\w+' }

D. $emails = foreach ($line in $lines) { $line -match '[\w.-]+@[\w.-]+\.\w+' }

Solution

1. Step 1: Understand how to loop and match each line

   We must check each line with -match and if it matches, collect the matched email from $matches[0].

2. Step 2: Evaluate each option

   $emails = foreach ($line in $lines) { if ($line -match '[\w.-]+@[\w.-]+\.\w+') { $matches[0] } } loops through lines, tests with -match, and collects matched emails correctly. $emails = $lines -match '[\w.-]+@[\w.-]+\.\w+' tries to match the whole array at once, which doesn't work. $emails = $lines | Where-Object { $_ -contains '[\w.-]+@[\w.-]+\.\w+' } uses -contains which does not support regex. $emails = foreach ($line in $lines) { $line -match '[\w.-]+@[\w.-]+\.\w+' } runs -match but does not collect matched emails.

3. Final Answer:

   $emails = foreach ($line in $lines) { if ($line -match '[\w.-]+@[\w.-]+\.\w+') { $matches[0] } } -> Option A

4. Quick Check:

   Loop + -match + $matches[0] collects matches [OK]

Hint: Use foreach + if (-match) + $matches[0] to collect matches [OK]

Common Mistakes:

• Trying to match the whole array at once
• Using -contains instead of -match for regex
• Not collecting $matches[0] inside the loop