Lua-std-regex

This is a simple Lua module that wraps C++11's regular expression (regex) capabilities to implement regex versions of Lua's string.find(), string.gmatch(), string.gsub(), and string.match().

It only requires a C++ compiler and runtime that support's the C++11 standard's regex features.

Compiling

There is a simple Makefile that builds a regex.so shared library on Linux by running make. You can also include lregex.h and/or lregex.cpp in your Lua-scripted application's build system. luaopen_regex is the module's C entry point.

Documentation

• regex.find(s, re[, init=1]): Searches string s for regex string re starting at position init, and returns the start and end positions of the match followed by any string values captured by re. Returns nil if no match was found.

• regex.gmatch(s, re[, init=1]): Returns an iterator that can be used in a for loop to iterate over all occurrences of regex string re in string s starting at position init. If re has captures, the captured values are assigned to loop variables. Otherwise, the entire match is used.

• regex.gsub(s, re, replacement[, n=0]): Returns a copy of string s where all (or the first n) instances of regex string re are replaced by string replacement, and also returns the number of replacements made. replacement may contain "$d" sequences, which represent the d-th value captured by re. replacement may also be a table or function. If it is a table, and the match or first capture exists as a key, that key's value is the replacement text. If replacement is a function, that function is called with either the captured values or the entire match as arguments. If the function returns a string or number, that result is the replacement text.

• regex.match(s, re[, init=1]): Searches string s for regex string re starting at position init, and returns either the values captured by re or the entire match itself. Returns nil if no match was found.

Usage

Lua 5.4.4  Copyright (C) 1994-2022 Lua.org, PUC-Rio
> re = require('regex')
> re.find('foo', 'o')
2	2
> for char in re.gmatch('foo', '.', 2) do print(char) end
o
o
> re.gsub('foo', '.', string.upper, 1)
Foo	1
> re.match('foo', 'fo+')
foo