Xojo Plugin

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

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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"

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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.

Xojo Plugin

Dim success As Boolean
success = False

Dim subject As String
subject = "Name: John Smith, Email: john.smith@example.com"
Dim pattern As String
pattern = "Name:\s+(\w+)\s+(\w+),\s+Email:\s+(\S+)"

Dim sb As New Chilkat.StringBuilder
success = sb.Append(subject)

Dim json As New Chilkat.JsonObject
json.EmitCompact = False

Dim timeoutMs As Int32
timeoutMs = 2000
Dim numMatches As Int32
numMatches = sb.RegexMatch(pattern,json,timeoutMs)
If (numMatches < 0) Then
    // Probably an error in the regular expression.
    // Suggestion: Use AI to help create and/or diagnose regular expressions.
    System.DebugLog(sb.LastErrorText)
    Return
End If

// Examine the matches:
System.DebugLog(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
//         }
//       ]
//     }
//   ]
// }

Dim cap As String
Dim i As Int32
i = 0
Dim matchCount As Int32
matchCount = json.SizeOfArray("match")
While i < matchCount
    System.DebugLog("Match " + Str(i + 1) + ":")
    json.I = i
    Dim j As Int32
    j = 0
    Dim numCaptureGroups As Int32
    numCaptureGroups = json.SizeOfArray("match[i].group")
    While j < numCaptureGroups
        json.J = j
        cap = json.StringOf("match[i].group[j].cap")
        System.DebugLog(Str(j) + ": " + cap)
        j = j + 1
    Wend
    i = i + 1
Wend

// 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