B4X Requires Chilkat v11.1.0+

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

B4X

Dim success As Boolean = False

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

Dim sb As ChilkatStringBuilder
sb.Initialize
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)

Log(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 ChilkatJsonObject
json.Initialize
json.EmitCompact = False

Dim timeoutMs As Int = 2000
Dim numMatches As Int = 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.
    Log(sb.LastErrorText)
    Return
End If


'  Examine the matches:
Log(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 Int = 0
Dim matchCount As Int = json.SizeOfArray("match")
Do While i < matchCount
    Log("Match " & (i + 1) & ":")
    json.I = i
    Dim j As Int = 0
    Dim numCaptureGroups As Int = json.SizeOfArray("match[i].group")
    Do While j < numCaptureGroups
        json.J = j
        cap = json.StringOf("match[i].group[j].cap")
        Log(j & ": " & cap)
        j = j + 1
    Loop
    i = i + 1
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
'  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.com