Lua Requires Chilkat v11.1.0+

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.

Lua

local chilkat = require("chilkat")

local success = false

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

local sb = chilkat.StringBuilder.new()
sb:append(subject)

local json = chilkat.JsonObject.new()
json.emit_compact = false

local timeoutMs = 2000
local numMatches = sb:regex_match(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.
    print(sb.last_error_text)
    return
end

-- Examine the matches:
print(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
--         }
--       ]
--     }
--   ]
-- }

local cap = ""
local i = 0
local matchCount = json:size_of_array("match")
while i < matchCount do
    print("Match " .. (i + 1) .. ":")
    json.i = i
    local j = 0
    local numCaptureGroups = json:size_of_array("match[i].group")
    while j < numCaptureGroups do
        json.j = j
        cap = json:string_of("match[i].group[j].cap")
        print(j .. ": " .. cap)
        j = j + 1
    end

    i = i + 1
end

-- 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