regex 0.1.46

An implementation of regular expressions for Rust.


A Rust library for parsing, compiling, and executing regular expressions. This particular implementation of regular expressions guarantees execution in linear time with respect to the size of the regular expression and search text. Much of the syntax and implementation is inspired by RE2.

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Module documentation with examples. The module documentation also include a comprehensive description of the syntax supported.

Documentation with examples for the various matching functions and iterators can be found on the Regex type.


Add this to your Cargo.toml:

regex = "0.1"

and this to your crate root:

extern crate regex;

Here's a simple example that matches a date in YYYY-MM-DD format and prints the year, month and day:

extern crate regex;

use regex::Regex;

fn main() {
    let re = Regex::new(r"(?x)
(?P<year>\d{4})  # the year
(?P<month>\d{2}) # the month
(?P<day>\d{2})   # the day
    let caps = re.captures("2010-03-14").unwrap();


If you have lots of dates in text that you'd like to iterate over, then it's easy to adapt the above example with an iterator:

extern crate regex;

use regex::Regex;

const TO_SEARCH: &'static str = "
On 2010-03-14, foo happened. On 2014-10-14, bar happened.

fn main() {
    let re = Regex::new(r"(\d{4})-(\d{2})-(\d{2})").unwrap();

    for caps in re.captures_iter(TO_SEARCH) {
        // Note that all of the unwraps are actually OK for this regex
        // because the only way for the regex to match is if all of the
        // capture groups match. This is not true in general though!
        println!("year: {}, month: {}, day: {}",

This example outputs:

year: 2010, month: 03, day: 14
year: 2014, month: 10, day: 14

Usage: regex! compiler plugin

The regex! compiler plugin will compile your regexes at compile time. This only works with a nightly compiler. The documentation explains the trade offs.

Here is a small example:


extern crate regex;

fn main() {
    let re = regex!(r"(\d{4})-(\d{2})-(\d{2})");
    let caps = re.captures("2010-03-14").unwrap();


Notice that we never unwrap the result of regex!. This is because your program won't compile if the regex doesn't compile. (Try regex!("(").)

Usage: a regular expression parser

This repository contains a crate that provides a well tested regular expression parser and abstract syntax. It provides no facilities for compilation or execution. This may be useful if you're implementing your own regex engine or otherwise need to do analysis on the syntax of a regular expression. It is otherwise not recommended for general use.

Documentation for regex-syntax with examples.


regex is primarily distributed under the terms of both the MIT license and the Apache License (Version 2.0), with portions covered by various BSD-like licenses.

See LICENSE-APACHE, and LICENSE-MIT for details.