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

/
/

Test String

Code Generator

Language

Generated Code

import Foundation let pattern = #"\d"# let regex = try! NSRegularExpression(pattern: pattern) let testString = #""" The rundown The modern monitoring stack is increasingly diverse and complex. Represented among the top 10 most popular tools are solutions for systems monitoring, APM, web and user monitoring, and log management. The top five monitoring challenges: 1) Quickly remediating service disruptions 2) Reducing alert noise 3) Securing budget for the proper tools 4) Quickly identifying service disruptions 5) Migrating services to the cloud IT teams are feeling alert pain more than ever before. Almost half of those surveyed receive over 50 alerts per day from their tools, and about a quarter receive more than 100. Alert floods have a clear and substantial effect on remediation. Of those who receive 100+ alerts per day, only 17% are able to investigate and remediate the majority (75-100%) within 24 hours. Strategic monitoring is clearly important, but execution is lacking. 80% agree that strategic monitoring is important to their organization, but only 12% are very satisfied. A good monitoring strategy goes a long way. Respondents who are satisfied with their organization’s monitoring strategy find critical IT issues much easier to handle and report the best rates of remediation. In addition, organizations with a defined monitoring process are better equipped to respond to alerts. IT performance is increasingly tied to business performance. Customer satisfaction and SLA compliance take the lead as the most common KPIs to measure IT performance, outranking “traditional” metrics, such as MTTR and incident volume. Good news for budgets, but not for ROI. Only 16% anticipate a decrease to their overall IT budget in 2016, while a third expect it to increase. However, a dismal 9% agreed that they were very satisfied with their organization’s monitoring strategy, based on overall investment """# let stringRange = NSRange(location: 0, length: testString.utf16.count) if let firstMatch = regex.firstMatch(in: testString, range: stringRange) { let result: [String] = (1 ..< firstMatch.numberOfRanges).map { (testString as NSString).substring(with: firstMatch.range(at: $0)) } print(result) } else { print("No matches were found.") }

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