DataFlex

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.

DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    String sSubject
    String sPattern
    Handle hoSb
    Variant vJson
    Handle hoJson
    Integer iTimeoutMs
    Integer iNumMatches
    String sCap
    Integer i
    Integer iMatchCount
    Integer j
    Integer iNumCaptureGroups
    String sTemp1

    Move False To iSuccess

    Move "Name: John Smith, Email: john.smith@example.com" To sSubject
    Move "Name:\s+(\w+)\s+(\w+),\s+Email:\s+(\S+)" To sPattern

    Get Create (RefClass(cComChilkatStringBuilder)) To hoSb
    If (Not(IsComObjectCreated(hoSb))) Begin
        Send CreateComObject of hoSb
    End
    Get ComAppend Of hoSb sSubject To iSuccess

    Get Create (RefClass(cComChilkatJsonObject)) To hoJson
    If (Not(IsComObjectCreated(hoJson))) Begin
        Send CreateComObject of hoJson
    End
    Set ComEmitCompact Of hoJson To False

    Move 2000 To iTimeoutMs
    Get pvComObject of hoJson to vJson
    Get ComRegexMatch Of hoSb sPattern vJson iTimeoutMs To iNumMatches
    If (iNumMatches < 0) Begin
        // Probably an error in the regular expression.
        // Suggestion: Use AI to help create and/or diagnose regular expressions.
        Get ComLastErrorText Of hoSb To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Examine the matches:
    Get ComEmit Of hoJson To sTemp1
    Showln sTemp1

    // 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
    //         }
    //       ]
    //     }
    //   ]
    // }

    Move 0 To i
    Get ComSizeOfArray Of hoJson "match" To iMatchCount
    While (i < iMatchCount)
        Showln "Match " (i + 1) ":"
        Set ComI Of hoJson To i
        Move 0 To j
        Get ComSizeOfArray Of hoJson "match[i].group" To iNumCaptureGroups
        While (j < iNumCaptureGroups)
            Set ComJ Of hoJson To j
            Get ComStringOf Of hoJson "match[i].group[j].cap" To sCap
            Showln j ": " sCap
            Move (j + 1) To j
        Loop

        Move (i + 1) To i
    Loop

    // 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


End_Procedure