cregex is a compact implementation of regular expression (regex) matching engine in C. Its design was inspired by Rob Pike's regex-code for the book "Beautiful Code" available online here. It is based on two papers by Russ Cox:

• Regular Expression Matching Can Be Simple And Fast
• Regular Expression Matching: the Virtual Machine Approach

cregex supports a subset of the syntax and semantics of the POSIX Basic Regular Expressions. The main design goal of cregex is to be small, correct, self contained and use few resources while retaining acceptable performance and feature completeness.

• ^ and $ anchors
• . match any single character
• [...] and [^...] character classes
• ?, *, +, and {x,y} greedy quantifiers
• ??, *?, +?, and {x,y}? non-greedy quantifiers
• (...) capturing groups

Simply run to build the library and test programs.

$ make

Run the tests from Go distribution.

$ make check

Visualize the regular expressions with Graphviz.

$ tests/re2dot "(a*)(b{0,1})(b{1,})b{3}" | dot -Tpng -o out.png

cregex is freely redistributable under the BSD 2 clause license. Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.