Dart Requires Chilkat v11.1.0+

Regular Expression with Capture Groups

See more Regular Expressions Examples

Note: Chilkat uses PCRE2. See PCRE2 Regular Expressions
Also see: PCRE2 Performance

Demonstrates the following PCRE2 regular expression:

See the sample code below.

Name:\s+(\w+)\s+(\w+),\s+Email:\s+(\S+)

And apply it to this string:

Name: John Smith, Email: john.smith@example.com

---

Regex Components Explained

Part	Meaning	Matched Text
"Name:"	Matches the literal text "Name:"	"Name:"
"\s+"	Matches one or more whitespace characters (spaces, tabs, etc.)	(space)
"(\w+)"	Capture Group 1: One or more word characters ("a-zA-Z0-9_")	"John"
"\s+"	More whitespace	(space)
"(\w+)"	Capture Group 2: Another word (the last name)	"Smith"
","	A literal comma	","
"\s+"	Whitespace again	(space)
"Email:"	Matches the literal "Email:"	"Email:"
"\s+"	Whitespace	(space)
"(\S+)"	Capture Group 3: One or more non-whitespace characters	"john.smith@example.com"

---

Matches for Your Example String

String:

"Name: John Smith, Email: john.smith@example.com"

Regex Match Groups:

Group	Captured Value
Group 1	"John"
Group 2	"Smith"
Group 3	"john.smith@example.com"

---

Notes on Character Classes

• \w matches [a-zA-Z0-9_] — so it doesn’t include punctuation like a period.
• \S matches any non-whitespace character, so it’s good for capturing an email.

Dart

import 'package:chilkat/chilkat.dart';

void main() {
  final subject = 'Name: John Smith, Email: john.smith@example.com';
  final pattern = 'Name:\\s+(\\w+)\\s+(\\w+),\\s+Email:\\s+(\\S+)';

  final sb = CkStringBuilder();
  sb.append(subject);

  final json = CkJsonObject();
  json.emitCompact = false;

  final timeoutMs = 2000;
  final numMatches = sb.regexMatch(pattern, json, timeoutMs);
  if (numMatches < 0) {
    // Probably an error in the regular expression.
    // Suggestion: Use AI to help create and/or diagnose regular expressions.
    print(sb.lastErrorText);
    return;
  }

  // Examine the matches:
  print(json.emit());

  // This is the JSON with the match information.
  // See the JSON parsing code below to get the matched capture group values.

  // Important:  Capture group 0 always contains the entire match — that is, the portion of the input string that matches the full regular expression.

  // {
  //   "match": [
  //     {
  //       "group": [
  //         {
  //           "cap": "Name: John Smith, Email: john.smith@example.com",
  //           "idx": 0,
  //           "len": 47
  //         },
  //         {
  //           "cap": "John",
  //           "idx": 6,
  //           "len": 4
  //         },
  //         {
  //           "cap": "Smith",
  //           "idx": 11,
  //           "len": 5
  //         },
  //         {
  //           "cap": "john.smith@example.com",
  //           "idx": 25,
  //           "len": 22
  //         }
  //       ]
  //     }
  //   ]
  // }

  var cap = '';
  var i = 0;
  final matchCount = json.sizeOfArray('match');
  while (i < matchCount) {
    print('Match ${i + 1}:');
    json.i = i;
    var j = 0;
    final numCaptureGroups = json.sizeOfArray('match[i].group');
    while (j < numCaptureGroups) {
      json.j = j;
      cap = json.stringOf('match[i].group[j].cap');
      print('$j: $cap');
      j++;
    }

    i++;
  }

  // Capture group 0 always contains the entire match — that is, the portion of the input string that matches the full regular expression.

  // Output

  // Match 1:
  // 0: Name: John Smith, Email: john.smith@example.com
  // 1: John
  // 2: Smith
  // 3: john.smith@example.com
}