Common regex patterns in PowerShell

Introduction

Regular expressions help you find or check text patterns quickly and easily.

Checking if an email address is valid.

Finding phone numbers in a document.

Extracting dates from text.

Replacing certain words in a file.

Validating user input like zip codes.

Syntax

PowerShell

Select-String -Pattern '<regex_pattern>' -Path '<file_path>'

# Or use -match operator:
$string -match '<regex_pattern>'

Use single quotes around regex patterns to avoid unwanted variable expansion.

The -match operator returns True if the pattern is found in the string.

Examples

Checks if the string contains one or more digits.

PowerShell

'hello123' -match '\d+'

Validates a simple email pattern.

PowerShell

'[e-mail]' -match '^[\w.-]+@[\w.-]+\.\w{2,}$'

Searches for a pattern like a Social Security number in a file.

PowerShell

Select-String -Pattern '\b\d{3}-\d{2}-\d{4}\b' -Path 'data.txt'

Sample Program

This script looks for an email and a phone number in the text and prints them if found.

PowerShell

$text = 'Contact me at [e-mail] or call 123-456-7890.'

if ($text -match '[\w.-]+@[\w.-]+\.\w{2,}') {
    Write-Output "Found an email address: $($matches[0])"
}

if ($text -match '\d{3}-\d{3}-\d{4}') {
    Write-Output "Found a phone number: $($matches[0])"
}

Important Notes

Remember to escape special characters like dot (.) and backslash (\) in regex patterns.

PowerShell stores the last match in the automatic variable $matches.

Regex patterns are case-insensitive by default with -match; use -cmatch for case-sensitive matching.

Summary

Regular expressions help find text patterns easily.

Use -match operator or Select-String cmdlet in PowerShell.

Common patterns include digits, emails, and phone numbers.