The crs-toolchain is the utility belt of CRS developers. It provides a single point of entry and a consistent interface for a range of different tools. Its core functionality (owed to the great rassemble-go, which is itself based on the brain-melting Regexp::Assemble Perl module) is to assemble individual parts of a regular expression into a single expression (with some optimizations).


With Existing Go Environment

If a current Go environment is present, simply run

go install

Provided that the Go binaries are on the PATH, the toolchain can now be run from anywhere with


With the Binary

Alternatively, one of the pre-built binaries can be downloaded from GitHub. Navigate to the latest release and download the package of choice along with the crs-toolchain-checksums.txt file. To verify the integrity of the binary/archive, navigate to the directory where the two files are stored and verify that the checksum matches:

cd ~/Downloads
shasum -a 256 -c crs-toolchain-checksums.txt 2>&1 | grep OK

The output should look like the following (depending on the binary/archive downloaded):

crs-toolchain-1.0.0_amd64.deb: OK

Test the Toolchain

It should now be possible to use the crs-toolchain. Test this by running the following in a shell:

printf "(?:homer)? simpson\n(?:lisa)? simpson" | crs-toolchain regex generate -

The output should be:

(?:homer|(?:lisa)?) simpson

Adjusting the Logging Level

The level of logging can be adjusted with the --log-level option. Accepted values are trace, debug, info, warn, error, fatal, panic, and disabled. The default level is info.

The regex Command

The regex command provides sub-commands for everything surrounding regular expressions, especially the “assembly” of regular expressions from a specification of its components (see Assembling Regular Expressions for more details).

Example Use

To generate a reduced expression from a list of expressions, simply pass the corresponding CRS rule ID to the script or pipe the contents to it:

crs-toolchain regex generate 942170
# or
cat util/regexp-assemble/data/ | crs-toolchain regex generate -

It is also possible to compare generated expressions to the current expressions in the rule files, like so:

crs-toolchain regex compare 942170

Even better, rule files can be updated directly:

crs-toolchain regex update 942170
# or update all
crs-toolchain regex update --all

Read the built-in help text for the full documentation:

crs-toolchain --help

The util Command

The util command includes sub-commands that are used from time to time and do not fit nicely into any of the other groups. Currently, the only sub-command is renumber-tests. renumber-tests is used to simplify maintenance of the regression tests. Since every test has a consecutive number within its file, adding or removing tests can disrupt numbering. renumber-tests will renumber all tests within each test file consecutively.

The completion command

The completion command can be used to generate a shell script for shell completion. For example:

crs-toolchain completion zsh >  ~/.zsh.d/2/crs-toolchain.zsh

How completion is enabled and where completion scripts are sourced from depends on the environment. Please consult the documentation of the shell in use.