Regular Expressions 101

Save & Share

Flavor

  • PCRE2 (PHP >=7.3)
  • PCRE (PHP <7.3)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java 8
  • .NET 7.0 (C#)
  • Rust
  • Regex Flavor Guide

Function

  • Match
  • Substitution
  • List
  • Unit Tests

Tools

Sponsors
There are currently no sponsors. Become a sponsor today!
An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression
No Match

/
/
gm

Test String

Code Generator

Language

Generated Code

import Foundation let pattern = #"ec2-(?:25[0-5]|2[0-4]\d|[0-1]?\d{1,2})(?:-(?:25[0-5]|2[0-4]\d|[0-1]?\d{1,2})){3}\.(?:eu|us|af|ap|ca|me|sa)-(?:west|central|south|north|(?:south|north)?east)-[1-9]{1,1}\.compute\.amazonaws\.com"# let regex = try! NSRegularExpression(pattern: pattern, options: .anchorsMatchLines) let testString = #""" ec2-54-189-171-120.us-east-1.compute.amazonaws.com ec2-35-158-116-105.us-east-2.compute.amazonaws.com ec2-13-210-58-232.us-west-1.compute.amazonaws.com ec2-54-202-130-232.us-west-2.compute.amazonaws.com ec2-52-40-225-119.af-south-1.compute.amazonaws.com ec2-54-244-14-137.ap-east-1.compute.amazonaws.com ec2-54-188-91-145.ap-south-1.compute.amazonaws.com ec2-16-221-167-247.ap-northeast-1.compute.amazonaws.com ec2-34-221-167-247.ap-northeast-2.compute.amazonaws.com ec2-34-221-167-247.ap-northeast-3.compute.amazonaws.com ec2-34-221-167-247.ap-southeast-1.compute.amazonaws.com ec2-34-221-167-247.ap-southeast-2.compute.amazonaws.com ec2-34-221-167-247.ap-southeast-3.compute.amazonaws.com ec2-34-221-167-247.ca-central-1.compute.amazonaws.com ec2-34-221-167-247.eu-central-1.compute.amazonaws.com ec2-34-221-167-247.eu-west-1.compute.amazonaws.com ec2-34-221-167-247.eu-west-2.compute.amazonaws.com ec2-34-219-81-114.eu-west-3.compute.amazonaws.com ec2-52-35-119-24.eu-south-1.compute.amazonaws.com ec2-35-160-82-97.eu-north-1.compute.amazonaws.com ec2-34-223-253-69.me-south-1.compute.amazonaws.com ec2-34-216-36-192.sa-east-1.compute.amazonaws.com """# let stringRange = NSRange(location: 0, length: testString.utf16.count) let matches = regex.matches(in: testString, range: stringRange) var result: [[String]] = [] for match in matches { var groups: [String] = [] for rangeIndex in 1 ..< match.numberOfRanges { let nsRange = match.range(at: rangeIndex) guard !NSEqualRanges(nsRange, NSMakeRange(NSNotFound, 0)) else { continue } let string = (testString as NSString).substring(with: nsRange) groups.append(string) } if !groups.isEmpty { result.append(groups) } } print(result)

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Swift 5.2, please visit: https://developer.apple.com/documentation/foundation/nsregularexpression