PureBasic

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.

PureBasic

IncludeFile "CkStringBuilder.pb"
IncludeFile "CkJsonObject.pb"

Procedure ChilkatExample()

    success.i = 0

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

    sb.i = CkStringBuilder::ckCreate()
    If sb.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkStringBuilder::ckAppend(sb,subject)

    json.i = CkJsonObject::ckCreate()
    If json.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkJsonObject::setCkEmitCompact(json, 0)

    timeoutMs.i = 2000
    numMatches.i = CkStringBuilder::ckRegexMatch(sb,pattern,json,timeoutMs)
    If numMatches < 0
        ; Probably an error in the regular expression.
        ; Suggestion: Use AI to help create and/or diagnose regular expressions.
        Debug CkStringBuilder::ckLastErrorText(sb)
        CkStringBuilder::ckDispose(sb)
        CkJsonObject::ckDispose(json)
        ProcedureReturn
    EndIf

    ; Examine the matches:
    Debug CkJsonObject::ckEmit(json)

    ; 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
    ;         }
    ;       ]
    ;     }
    ;   ]
    ; }

    cap.s
    i.i = 0
    matchCount.i = CkJsonObject::ckSizeOfArray(json,"match")
    While i < matchCount
        Debug "Match " + Str(i + 1) + ":"
        CkJsonObject::setCkI(json, i)
        j.i = 0
        numCaptureGroups.i = CkJsonObject::ckSizeOfArray(json,"match[i].group")
        While j < numCaptureGroups
            CkJsonObject::setCkJ(json, j)
            cap = CkJsonObject::ckStringOf(json,"match[i].group[j].cap")
            Debug 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


    CkStringBuilder::ckDispose(sb)
    CkJsonObject::ckDispose(json)


    ProcedureReturn
EndProcedure