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

/
/
g

Test String

Code Generator

Language

Generated Code

import Foundation let pattern = #"[^\w](?<!->)(trans|trans_choice|Lang::get|Lang::choice|Lang::trans|Lang::transChoice|@lang|@choice|__)\s*\(\s*((?<![\\])['"])((?:.(?!(?<![\\])\2))*.?)\2\s*[,\)]"# let regex = try! NSRegularExpression(pattern: pattern) let testString = #""" Should match variations on method: trans('a.b'); trans_choice('a.b') Lang::get('a.b'); Lang::choice('a.b', 1); Lang::trans('a.b'); Lang::transChoice('a.b', 2); @lang('language.line') @choice('language.line', 1); __('a.b') Should match variations of contained string trans('key'); // No group, so JSON style __('Json string') trans('a.b'); trans('a.b.c'); trans('a_b.c-d'); trans('a.b!'); trans('a.translate me!'); trans('a.über~'); trans("app.i'm"); // contained quote of different type trans('app."ok"'); trans('with contained " quotes'); trans('with an escaped \' quote') trans('with a double \\') Should match additional variables and whitespace trans('a.b', [1,2]); trans ( ' with whitespace ' , $var) Typical use cases (trans ( 'lang.line')); <span>@lang('lang.line')</span> Should not match: trans($var); // No quotes trans(); // Nothing anytrans('group.key'); // not the method we need 1trans('lang.file'); // not the method _trans('lang.file'); // not the method ->trans('lang.line'); trans(\'why do we have an escaped quote here?\') trans('with a triple \\\') <-- fail! trans('lang.line' . $middle); // concatenated vars trans('lang.line' . $middle . '.ending'); // concatenated vars ___('hello') // not the method we need """# 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