Switch with wildcard and regex in PowerShell - Mini Project: Build & Apply

Switch with wildcard and regex

📖 Scenario: You are creating a simple script to categorize file names based on their patterns. This helps you quickly identify file types and special cases.

🎯 Goal: Build a PowerShell script that uses a switch statement with wildcard and regex patterns to classify file names into categories.

📋 What You'll Learn

Create a list of file names in a variable called files with exact values.

Create a variable called specialPattern to hold a regex pattern.

Use a switch statement with wildcard and regex matching to categorize each file name.

Print the file name and its category.

💡 Why This Matters

🌍 Real World

Automating file management tasks by categorizing files based on their names helps organize data and trigger specific actions.

💼 Career

Knowing how to use switch with wildcard and regex in PowerShell is useful for system administrators and automation engineers managing files and logs.

1

Create the list of file names

Create a variable called files and assign it an array with these exact file names: report1.txt, data_backup.zip, image01.png, notes.docx, temp123.tmp.

PowerShell

# Create the variable files with the exact file names
# Your code here

Hint

Use @( ... ) to create an array in PowerShell.

2

Create the regex pattern variable

Create a variable called specialPattern and assign it the regex pattern string ^temp\d+\.tmp$ to match file names starting with 'temp' followed by digits and ending with '.tmp'.

PowerShell

$files = @('report1.txt', 'data_backup.zip', 'image01.png', 'notes.docx', 'temp123.tmp')
# Create the variable specialPattern with the regex string
# Your code here

Hint

Remember to escape backslashes in the regex string.

3

Use switch with wildcard and regex

Use a switch statement with -Wildcard and -Regex parameters to check each file in $files. Use these cases:
- Wildcard *.txt prints ' is a text file'.
- Wildcard *.zip prints ' is a zip archive'.
- Regex matching $specialPattern prints ' is a special temp file'.
- Default case prints ' is an unknown file type'.
Use foreach to loop over $files and apply the switch inside the loop.

PowerShell

$files = @('report1.txt', 'data_backup.zip', 'image01.png', 'notes.docx', 'temp123.tmp')
$specialPattern = '^temp\d+\.tmp$'
# Loop over files and use switch with -Wildcard and -Regex
# Your code here

Hint

Use nested switch statements to handle wildcard and regex separately.

4

Print the categorized file types

Run the script to print the category of each file as per the switch logic. The output should show each file name followed by its category message.

PowerShell

$files = @('report1.txt', 'data_backup.zip', 'image01.png', 'notes.docx', 'temp123.tmp')
$specialPattern = '^temp\d+\.tmp$'
foreach ($file in $files) {
    switch -Wildcard ($file) {
        '*.txt' { Write-Output "$file is a text file"; break }
        '*.zip' { Write-Output "$file is a zip archive"; break }
        default {
            switch -Regex ($file) {
                $specialPattern { Write-Output "$file is a special temp file"; break }
                default { Write-Output "$file is an unknown file type" }
            }
        }
    }
}
# Run the script to see output

Hint

Run the script and check the console output matches the expected categories.

Practice

1. What does the -Wildcard parameter do in a PowerShell switch statement?

easy

A. It matches patterns using complex regular expressions.

B. It makes the switch statement run faster by skipping checks.

C. It forces the switch to ignore case sensitivity.

D. It matches patterns using simple wildcards like * and ?.

Solution

1. Step 1: Understand the role of -Wildcard

   The -Wildcard parameter allows pattern matching using simple wildcards such as * (any characters) and ? (single character).

2. Step 2: Differentiate from -Regex

   Unlike -Regex, which uses complex regular expressions, -Wildcard is simpler and easier for basic pattern matching.

3. Final Answer:

   It matches patterns using simple wildcards like * and ?. -> Option D

4. Quick Check:

   -Wildcard = simple wildcard matching [OK]

Hint: Remember: Wildcard = * and ? patterns, Regex = complex patterns [OK]

Common Mistakes:

• Confusing -Wildcard with -Regex
• Thinking -Wildcard ignores case by default
• Assuming -Wildcard speeds up execution

2. Which of the following is the correct syntax to use a switch statement with wildcard matching in PowerShell?

easy

A. switch ($input) { '*test*' -Wildcard { 'Match' } }

B. switch ($input) -Wildcard { '*test*' { 'Match' } }

C. switch -Wildcard ($input) { '*test*' { 'Match' } }

D. switch ($input) { -Wildcard '*test*' { 'Match' } }

Solution

1. Step 1: Identify correct parameter placement

   In PowerShell, the -Wildcard parameter is placed immediately after switch and before the input expression.

2. Step 2: Check the pattern and block syntax

   The pattern '*test*' and the script block '{ 'Match' }' are correctly placed inside the switch braces.

3. Final Answer:

   switch -Wildcard ($input) { '*test*' { 'Match' } } -> Option C

4. Quick Check:

   Parameter right after switch keyword = switch -Wildcard ($input) { '*test*' { 'Match' } } [OK]

Hint: Put -Wildcard right after switch, before input [OK]

Common Mistakes:

• Placing -Wildcard inside the switch block
• Putting -Wildcard after the input variable
• Using -Wildcard as a pattern inside braces

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

switch -Regex ('apple', 'banana', 'cherry') {
  '^a' { 'Starts with a' }
  'an' { 'Contains an' }
  default { 'No match' }
}

medium

A. Starts with a
Contains an
No match

B. Starts with a
No match
No match

C. No match
Contains an
No match

D. Starts with a
Contains an
Contains an

Solution

1. Step 1: Check each input against regex patterns

   'apple' matches '^a' (starts with 'a'), so outputs 'Starts with a'. 'banana' contains 'an', so matches 'an' pattern, outputs 'Contains an'. 'cherry' matches none, so outputs 'No match'.

2. Step 2: Confirm output order

   The outputs correspond to each input in order: 'apple' -> 'Starts with a', 'banana' -> 'Contains an', 'cherry' -> 'No match'.

3. Final Answer:

   Starts with a Contains an No match -> Option A

4. Quick Check:

   Regex matches each input correctly = Starts with a Contains an No match [OK]

Hint: Match each input line by line with regex patterns [OK]

Common Mistakes:

• Assuming only first match per input
• Confusing regex anchors like ^
• Ignoring default case output

4. Identify the error in this PowerShell switch statement using wildcard matching:

switch ($word) -Wildcard {
  'he*' { 'Starts with he' }
  '*lo' { 'Ends with lo' }
  default { 'No match' }
}

medium

A. The -Wildcard parameter should be before the input variable.

B. The patterns 'he*' and '*lo' are invalid wildcards.

C. The default case is missing a script block.

D. The switch statement cannot use wildcards with variables.

Solution

1. Step 1: Check parameter placement

   The -Wildcard parameter must come immediately after the switch keyword, not after the input variable.

2. Step 2: Validate patterns and default block

   The patterns 'he*' and '*lo' are valid wildcards. The default case has a proper script block. Using wildcards with variables is allowed.

3. Final Answer:

   The -Wildcard parameter should be before the input variable. -> Option A

4. Quick Check:

   Parameter placement error = The -Wildcard parameter should be before the input variable. [OK]

Hint: Place -Wildcard right after switch, before input variable [OK]

Common Mistakes:

• Putting -Wildcard after input variable
• Thinking wildcards are invalid patterns
• Omitting script block braces

5. You want to categorize a list of filenames using switch with both wildcard and regex patterns. Which approach correctly combines -Wildcard and -Regex in one script to handle different patterns?

hard

A. Use a single switch with both -Wildcard and -Regex parameters together.

B. Use two separate switch statements: one with -Wildcard, one with -Regex, processing the list twice.

C. Use -Wildcard and -Regex as pattern modifiers inside one switch statement.

D. Use -Regex only and convert wildcards to regex patterns manually.

Solution

1. Step 1: Understand parameter exclusivity

   PowerShell's switch does not support using -Wildcard and -Regex together in one statement. They are mutually exclusive parameters.

2. Step 2: Choose practical approach

   To handle both wildcard and regex patterns, use two separate switch statements: one with -Wildcard and one with -Regex, processing the list twice.

3. Final Answer:

   Use two separate switch statements: one with -Wildcard, one with -Regex, processing the list twice. -> Option B

4. Quick Check:

   Separate switches for wildcard and regex = Use two separate switch statements: one with -Wildcard, one with -Regex, processing the list twice. [OK]

Hint: Use separate switches for wildcard and regex patterns [OK]

Common Mistakes:

• Trying to combine -Wildcard and -Regex in one switch
• Assuming pattern modifiers inside switch block
• Converting wildcards manually instead of separate switches