Lua Requires Chilkat v11.1.0+

Regular Expression with Multiple Matches and Named Capture Groups

See more Regular Expressions Examples

Demonstrates regular expressions with named capture groups and multiple matches. Lua

local chilkat = require("chilkat")

local success = false

local sb = chilkat.StringBuilder.new()
local crlf = true
sb:append_line("Name: John Smith", crlf)
sb:append_line("Name: Jack Johnson", crlf)
sb:append_line("Name: Mary Adams", crlf)

print(sb:get_as_string())

-- We have the following string:
-- Name: John Smith
-- Name: Jack Johnson
-- Name: Mary Adams

local pattern = "Name:\\s+(?<first>\\w+)\\s+(?<last>\\w+)"
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())

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

-- {
--   "named": {
--     "first": 1,
--     "last": 2
--   },
--   "match": [
--     {
--       "group": [
--         {
--           "cap": "Name: John Smith",
--           "idx": 0,
--           "len": 16
--         },
--         {
--           "cap": "John",
--           "idx": 6,
--           "len": 4
--         },
--         {
--           "cap": "Smith",
--           "idx": 11,
--           "len": 5
--         }
--       ]
--     },
--     {
--       "group": [
--         {
--           "cap": "Name: Jack Johnson",
--           "idx": 18,
--           "len": 18
--         },
--         {
--           "cap": "Jack",
--           "idx": 24,
--           "len": 4
--         },
--         {
--           "cap": "Johnson",
--           "idx": 29,
--           "len": 7
--         }
--       ]
--     },
--     {
--       "group": [
--         {
--           "cap": "Name: Mary Adams",
--           "idx": 38,
--           "len": 16
--         },
--         {
--           "cap": "Mary",
--           "idx": 44,
--           "len": 4
--         },
--         {
--           "cap": "Adams",
--           "idx": 49,
--           "len": 5
--         }
--       ]
--     }
--   ]
-- }

-- The capture group index is obtained by looking up the name in the JSON result.
-- For example:

local idx_first = json:int_of("named.first")
local idx_last = json:int_of("named.last")

local i = 0
local matchCount = json:size_of_array("match")
while i < matchCount do
    print("Match " .. (i + 1) .. ":")
    json.i = i

    json.j = idx_first
    print("first: " .. json:string_of("match[i].group[j].cap"))

    json.j = idx_last
    print("first: " .. json:string_of("match[i].group[j].cap"))

    print("")
    i = i + 1
end

-- Output is:

-- Match 1:
-- first: John
-- first: Smith
--
-- Match 2:
-- first: Jack
-- first: Johnson
--
-- Match 3:
-- first: Mary
-- first: Adams