VB.NET

Regular Expression with Multiple Matches and Capture Groups

See more Regular Expressions Examples

Demonstrates a regular expression with multiple matches and capture groups for each match.

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

VB.NET

Dim success As Boolean = False

Dim pattern As String = "Name:\s+(\w+)\s+(\w+),\s+Email:\s+(\S+)"

Dim sb As New Chilkat.StringBuilder
Dim crlf As Boolean = True
sb.AppendLine("Name: John Smith, Email: john.smith@example.com",crlf)
sb.AppendLine("Name: Jack Johnson, Email: jack.johnson@example.com",crlf)
sb.AppendLine("Name: Mary Adams, Email: mary.adams@example.com",crlf)

Debug.WriteLine(sb.GetAsString())

' We have the following string:
' Name: John Smith, Email: john.smith@example.com
' Name: Jack Johnson, Email: jack.johnson@example.com
' Name: Mary Adams, Email: mary.adams@example.com

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

Dim timeoutMs As Integer = 2000
Dim numMatches As Integer = 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.
    Debug.WriteLine(sb.LastErrorText)
    Exit Sub
End If


' Examine the matches:
Debug.WriteLine(json.Emit())

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

' {
'   "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
'         }
'       ]
'     },
'     {
'       "group": [
'         {
'           "cap": "Name: Jack Johnson, Email: jack.johnson@example.com",
'           "idx": 49,
'           "len": 51
'         },
'         {
'           "cap": "Jack",
'           "idx": 55,
'           "len": 4
'         },
'         {
'           "cap": "Johnson",
'           "idx": 60,
'           "len": 7
'         },
'         {
'           "cap": "jack.johnson@example.com",
'           "idx": 76,
'           "len": 24
'         }
'       ]
'     },
'     {
'       "group": [
'         {
'           "cap": "Name: Mary Adams, Email: mary.adams@example.com",
'           "idx": 102,
'           "len": 47
'         },
'         {
'           "cap": "Mary",
'           "idx": 108,
'           "len": 4
'         },
'         {
'           "cap": "Adams",
'           "idx": 113,
'           "len": 5
'         },
'         {
'           "cap": "mary.adams@example.com",
'           "idx": 127,
'           "len": 22
'         }
'       ]
'     }
'   ]
' }

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

Dim cap As String
Dim i As Integer = 0
Dim matchCount As Integer = json.SizeOfArray("match")
While i < matchCount
    Debug.WriteLine("Match " & (i + 1) & ":")
    json.I = i
    Dim j As Integer = 0
    Dim numCaptureGroups As Integer = json.SizeOfArray("match[i].group")
    While j < numCaptureGroups
        json.J = j
        cap = json.StringOf("match[i].group[j].cap")
        Debug.WriteLine(j & ": " & cap)
        j = j + 1
    End While
    i = i + 1
End While

' 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
' Match 2:
' 0: Name: Jack Johnson, Email: jack.johnson@example.com
' 1: Jack
' 2: Johnson
' 3: jack.johnson@example.com
' Match 3:
' 0: Name: Mary Adams, Email: mary.adams@example.com
' 1: Mary
' 2: Adams
' 3: mary.adams@example.co