Curated list of awesome lists

Awesome Crystal

A curated list of awesome Crystal code and resources. Inspired by awesome and awesome-awesomeness. The goal is to have projects mostly stable and useful for the community.

Search shards at shards.info or follow announcements Crystal [ANN] for more.

Contributions are welcome. Please take a quick look at the contribution guidelines first.

Awesome Crystal
Community
- Unofficial
Resources
- Official Documentation Translations
Services and Apps
Tools

Algorithms and Data structures

bisect - Inserting values into a sorted array
blurhash.cr - BlurHash implementation
crie - Compile-time Trie
CrOTP - HOTP and TOTP implementation for two factor authentication
crystal-linked-list - Implementation of Linked List
crystaledge - A pure Vector Math library
crystalg - A Generic Algorithm Library
crystalline - A collection of containers and algorithms
csuuid - A Chronologically Sortable UUID
edits.cr - Collection of edit distance algorithms
fzy - A Crystal port of awesome Fzy project fuzzy finder algorithm
Goban - A fast and efficient QR Code implementation
graphlb - Collection of graph datastructure and algorithms
haversine - An Implementation of the Haversine formula
kd_tree - An implementation of "K-Dimensional Tree" and "N-Nearest Neighbors"
ksuid.cr - K-Sortable Globally Unique IDs
markov - Build Markov Chains and run Markov Processes
multiset.cr - Implementation of a multiset
qr-code - QR Code generator
radix - Radix Tree implementation
s2_cells - S2 Geometry for spatial indexing
secure-remote-password - SRP-6a protocol for authentication over an insecure network
splay_tree_map - Splay Tree implementation that conforms to the Hash ducktype

Blockchain

Axentro - A custom blockchain platform
Cocol - A minimal blockchain testbed
secp256k1.cr - Elliptic curve used in the public-private-key cryptography

C bindings

augeas.cr - Bindings for Augeas
clang.cr - Libclang bindings
crt.cr - Bindings for libncursesw and crt
crystal-gsl - Bindings for GNU Scientific Library
crystal-hunspell - Bindings for Hunspell
duktape.cr - Bindings for the Duktape javascript engine
fftw.cr - Bindings for FFTW library
gphoto2.cr - Bindings for the libgphoto2 library
icu.cr - Bindings for the ICU library
libnotify.cr - Bindings for Libnotify
nlopt.cr - Bindings for NLOpt
pcap.cr - Bindings for libpcap
pledge.cr - Bindings for OpenBSD's pledge(2)
ssh2.cr - Bindings for libssh2 library
syslog.cr - Bindings for syslog
v4l2.cr - Bindings for Video4Linux2
wasmer-crystal - Bindings for the wasmer WebAssembly runtime
win32cr - Bindings for Win32 API
x_do.cr - Bindings for libxdo (xdotool)

Caching

crystal-memcached - Implementation of a memcached client

CLI Builders

admiral - A robust DSL for writing command line interfaces
Athena Console - Allows for the creation of CLI based commands
clicr - A simple declarative command line interface builder
clim - Slim command line interface builder
Cling - A modular, non-macro-based command line interface library
commander - Command-line interface builder
Keimeno - A lightweight text user interface library in Crystal
OptionParser - command-line options processing (Crystal stdlib)
Phreak - A highly flexible Crystal CLI builder in the style of OptionParser

CLI Utils

climate - Tiny tool to make your CLI output 🌈 coloured
coin - Command-line application that performs currency conversion via the Fixer API
cride - A light CLI text editor/IDE
git-repository - A git cli wrapper querying and cloning remote repositories with minimal data transfer
hetzner-k3s - A CLI tool to quickly create and manage Kubernetes clusters in Hetzner Cloud
lff - Simple and straightforward large files finder utility in command line
meet - Start a jitsi meeting quickly from the comfort of your command line
oq - A performant, and portable jq wrapper to facilitate the consumption and output of formats other than JSON; using jq filters to transform the data
progress_bar.cr - A simple and customizable progress bar
tablo - A flexible terminal table generator
tallboy - Generate ASCII character tables with support for spanning cells over multiple columns

Code Analysis and Metrics

ameba - A static code analysis tool
linguist.cr - Using multiple ways to find programming language used in files, based on Github's Linguist

Compression

Crystar - Readers and writers of Tar archive format
Gzip - readers and writers of gzip format (Crystal stdlib)
polylines.cr — compression of series of coordinates
snappy - Snappy compression format reader/writer for Crystal
Zip - readers and writers of zip format (Crystal stdlib)
Zlib - readers and writers of zlib format (Crystal stdlib)
zstd.cr - Bindings for Zstandard compression library

Configuration

cr-dotenv - Loads .env file
Envy - Load environment variables from YAML
envyable - A simple YAML to ENV config loader
habitat - Type safe configuration for your classes and modules
totem - Load and parse a configuration in JSON, YAML, dotenv formats

Converters

base62.cr - Base62 encoder/decoder, well suited for url-shortening
crunits - Tool for converting units of measure (miles to kilometers, celsius to fahrenheit etc)
money - Handling money and currency conversion with ease (almost complete port of RubyMoney)
sass.cr - Compile SASS/SCSS to CSS (libsass binding)

Cryptography

cmac - Crystal implementation of Cipher-based Message Authentication Code (CMAC)
ed25519 - the Ed25519 elliptic curve public-key signature system described in [RFC 8032]
monocypher.cr - Crystal wrapper for the Monocypher crypto library
sodium.cr - Crystal wrapper for the libsodium crypto API

Data Formats

BinData - Binary data parser helper with an ASN.1 parser
config.cr - Easy to use configuration format parser
crinder - Class based json renderer
Crystalizer - (De)serialize any Crystal object; supporting JSON, YAML, and Byte formats out of the box
CSV - parsing and generating for comma-separated values (Crystal stdlib)
front_matter.cr - Separates a files front matter from its content
geoip2.cr - GeoIP2 reader
HAR - HAR (HTTP Archive) parser
INI - INI file parser (Crystal stdlib)
JSON - parsing and generating JSON documents (Crystal stdlib)
json-schema - convert JSON serializable classes into a JSON Schema representation
JSON::OnSteroids - handle and mutate JSON document easily
maxminddb.cr - MaxMindDB reader
toml.cr - TOML parser
XML - parsing and generating XML documents (Crystal stdlib)
YAML - parsing and generating YAML documents (Crystal stdlib)

Data Generators

faker - A library for generating fake data
hashids.cr - A library to generate YouTube-like ids from one or many numbers
prime - A prime number generator

Database Drivers/Clients

couchdb.cr - CouchDB client
cryomongo - MongoDB driver
crystal-db - Common db api
crystal-ldap - LDAP client
crystal-mysql - MySQL connector for Crystal
crystal-pg - A Postgres driver
crystal-redis - Full featured Redis client
crystal-rethinkdb - Driver for RethinkDB / RebirthDB
crystal-sqlite3 - SQLite3 bindings
leveldb - Crystal bindings for LevelDB
rocksdb.cr - RocksDB client
surrealdb.cr - Unoffical SurrealDB HTTP & Websocket Client

Database Tools

migrate - A simpler database migration tool with transactions

Debugging

backtracer.cr - Shard aiming to assist with parsing backtraces into a structured form
debug.cr - debug!(…) macro for pp-style debugging

Dependency Injection

Athena Dependency Injection - Robust dependency injection service container framework
Crystal-DI - Lightweight DI Container
HardWire - A compile-time non-intrusive dependency injection system
syringe - A simple and basic dependency injection shard for crystal

Email

carbon - Fun, testable, and adapter-based email library
crystal-email - Simple e-mail sending library
CrystalEmail - A RFC compliant Email validator
sendgrid.cr - Simple Sendgrid Client

Environment Management

asdf-crystal - Plugin for asdf version manager
crenv - Crystal version manager
rcm.cr - Redis Cluster Manager

Examples and funny stuff

blackjack-cr - Console Blackjack
crystal-patterns - Examples of GOF patters
crystalworld - realworld.io back-end API implementation
exercism-crystal - Exercism exercises
try.cr - Try monad

Framework Components

Athena Event Dispatcher - A Mediator and Observer pattern event library
Athena Negotiation - Framework agnostic content negotiation library
device_detector - Shard for detect device by user agent string
Exception Page - An exceptional exception page for Crystal web libraries and frameworks
graphql - Type-safe GraphQL server implementation
graphql-crystal - GraphQL implementation
kemal-session - Session handler for Kemal
mochi - Authentication shard inspired by Devise supporting: Authenticable, Confirmable, Invitable & more
motion.cr - Object oriented frontend library for Amber
multi-auth - Standardized multi-provider OAuth2 authentication (inspired by omniauth)
praetorian - Minimalist authorization library inspired by Pundit
Shield - Comprehensive security for Lucky framework
shrine.cr - File Attachment toolkit for Crystal applications. Heavily inspired by Shrine for Ruby
tourmaline - Telegram bot framework with an API loosely based on telegraf.js

Game Development

CrSFML - Bindings to SFML multimedia/game library
crystal-chipmunk - Bindings to Chipmunk, a fast and lightweight 2D game physics library
crystal-imgui-sfml - Bindings to integrate Dear ImGui into an SFML project
entitas.cr - A Entity Component System Framework for Crystal
MyECS - A Sparse Entity Component System Framework for Crystal
Raylib-cr - Direct bindings to Raylib, which supports Linux, Windows, and Mac
SDL-Crystal-Bindings - Direct (unsafe) bindings to SDL2, intended for writing own game libraries

GUI Development

crystal-imgui - Bindings to Dear ImGui, an immediate-mode graphical UI library
GTK4.cr - Bindings for GTK4 with Crystalized API
Iu - UI framework based on the Fusion/libui.cr library, with custom elements and modified bindings from hedron-crystal/hedron
Ultimate GTK4 Crystal Guide - Learn how to create premium GTK4 apps in Crystal

HTML Builders

blueprint - Write reusable and testable HTML templates in plain Crystal
form_builder.cr - Dead simple HTML form builder for Crystal with built-in support for many popular UI libraries such as Bootstrap
to_html - The fastest HTML builder engine for Crystal
Water - A library for writing HTML in plain Crystal

HTML/XML Parsing

docx_cr_converter - parse DOCX Word
myhtml - Fast HTML5 Parser that includes CSS selectors

HTTP

Cable - An ActionCable "port" to Crystal, framework agnostic, 100% compatible with the ActionCable JS Client
cossack - Simple flexible HTTP client
crest - Simple HTTP and REST client, inspired by the Ruby's RestClient gem
crul - Command line HTTP client
digest-auth - Digest authentication
halite - Crystal HTTP Requests with a chainable REST API, built-in sessions and loggers
http-multiserver.cr - Mounting multiple servers via routes (a.k.a. URL mapping)
http-params-serializable - HTTP params (de)serialization, applicable to URL queries and URL-encoded forms
http-protection - Protection against typical web attacks
http2 - HTTP/2 Protocol Implementation
HTTP::Client - HTTP client (Crystal stdlib)
HTTP::Server - HTTP server (Crystal stdlib)
HTTP::WebSocket - HTTP WebSocket client (Crystal stdlib)
link-header - HTTP Link Header Parser
ntlm - NTLM authentication
proxy-fetcher.cr - Proxy lists fetching & validating library
sse.cr - Server-Sent Events client

Image processing

celestine - Create SVG images using a DSL
ffmpeg - FFmpeg bindings that works with StumpyPNG to extract frames
Pluto - A fast and convenient image processing library
stumpy_png - Read and write PNG images

Implementations/Compilers

charly - Charly Programming Language
cltk - A crystal port of the Ruby Language Toolkit
crisp - Lisp dialect implemented with Crystal
LinCAS-lang - A programming language for scientific computation
mint-lang - A refreshing programming language for the front-end web
myst-lang - A practical, dynamic language designed to be written and understood as easily and efficiently as possible
novika - A free-form, moldable, interpreted programming language
runic-lang - In-design toy language

Internationalization

crystal-i18n - An internationalization library inspired by Ruby-I18n
i18n.cr - Internationalization shard
Lens - A multiformat internationalization (i18n) shard for Crystal. Supports Gettext, Ruby YAML, etc.
Rosetta - A blazing fast internationalization (i18n) library with compile-time key lookup supporting YAML and JSON formats

Logging and monitoring

crafana - A Grafana library to help autogenerate dashboards
fiber_metrics.cr - Track run time, wait time, or memory allocations per Fiber, method or block
Log - logging utility (Crystal stdlib)
statsd.cr - Statsd client library

Machine Learning

ai4cr - Artificial Intelligence (based on https://github.com/SergioFierens/ai4r)
Cadmium - NLP library based heavily on natural
crystal-fann - FANN (Fast Artifical Neural Network) binding
mxnet.cr - Bindings for MXNet
shainet - SHAInet (Neural Network in pure crystal)

Markdown/Text Processors

markd - Yet another markdown parser built for speed, Compliant to CommonMark specification

Misc

aasm.cr - Easy to use finite state machine for Crystal classes
any_hash.cr - Recursive Hash with better JSON::Any included
anyolite - Full mruby interpreter with simple bindings, allowing for easy scripting support in projects
burocracia.cr - burocracia.cr the dependecyless shard to validate, generate and format Brazilian burocracias such as CPF, CNPJ and CEP
callbacks - Expressive callbacks module
circuit_breaker - Implementation of the circuit breaker pattern
CrSignals - Signals/slots notification library
crystal-binary_parser - Binary parser
crystal-web-framework-stars - Web frameworks for Crystal, most starred on Github
crz - Functional programming library
defined - macros for conditional compilation based on constant definitions, version requirements, or environment variable settings
emoji.cr - Emoji library
gphoto2-web.cr - Web API for libgphoto2
immutable - Implementation of thread-safe, persistent, immutable collections
iterm2 - Display images within the terminal using the ITerm2 Inline Images Protocol
monads - Monad implementation
observable - Implementation of the observer pattern
pinger - Ping IP addresses and DNS entries without requiring sudo
port_midi - Crystal C bindings for the PortMIDI cross-platform MIDI I/O library
retriable.cr - Simple DSL to retry failed code blocks
serf-handler.cr - Framework for building Serf handlers, with a suite of useful builtin capabilities
simple_retry - Simple tool for retrying failed code blocks
sslscan.cr - Crystal shard wrapping the rbsec/sslscan utility
version_tools - Version-dependent behaviour, specified at compile-time
wafalyzer - Web Application Firewall (WAF) Detector - shard + cli
zaru_crystal - Filename sanitization

Network Protocols

amqp-client.cr - AMQP 0-9.1, a messaging protocol, implemented by eg. RabbitMQ
connect-proxy - Connect method style of HTTP tunnelling / HTTP proxy
cr-xmpp - XMPP/Jabber Library
Crirc - IRC protocol implementation (Client, Server, Bots)
crystal-bacnet - BACnet protocol implementation with BACnet/IP client
crystal-dns - DNS protocol implementation and resolver
crystal-json-socket - JSON-socket client & server implementation. Inspired by and compatible with node-json-socket and ruby-json-socket
crystal-mqtt - A MQTT client
crystal-snmp - An SNMP implementation with version 1, 2c and 3 support
fast_irc.cr - Fast IRC parser/generator
jwt - Implementation of JWT (JSON Web Token)
mDNS - DNS Service Discovery and multicast DNS
mqtt-client.cr - A fast and lightweight MQTT client
msgpack-crystal - MessagePack library
OAuth - OAuth consumer (Crystal stdlib)
OAuth2 - OAuth2 client (Crystal stdlib)
OpenSSL - bindings to libssl (Crystal stdlib)
simple_rpc - RPC Server and Client for Crystal. Implements msgpack-rpc protocol
stomp - STOMP protocol
telnet.cr - Telnet protocol
transfer_more - Clone of transfer.sh to uploads files

Networking

ipaddress.cr - Library to handle IPv4 and IPv6 addresses
mac-address - Library for working with MAC addresses

ORM/ODM Extensions

avram - A database wrapper for reading, writing, and migrating Postgres databases
clear - ORM specialized to PostgreSQL only but with advanced features
crecto - Database wrapper, based on Ecto
granite - ORM for Postgres, Mysql, Sqlite
jennifer.cr - Active Record pattern implementation with flexible query chainable builder and migration system
rethinkdb-orm - ORM for RethinkDB / RebirthDB

Package Management

shards - Dependency manager for the Crystal

Processes and Threads

await_async - Add keywords await & async in Crystal Lang
concurrent.cr - Simplified concurrency using streams/pipelines, waitgroups, semaphores, smores and more
neph - A modern command line job processor that can execute jobs concurrently
promise - A Promise implementation with type inference
werk - Dead simple task runner with concurrent support, ideal for local CI

Project Generators

crystal_lib - Automatic binding generator for native libraries
fez - A Kemal application generator
libgen - Automatic bindings generator configured using JSON/YAML files

Queues and Messaging

mosquito - Redis backed periodic and ad hoc job processing
NATS.io - NATS client
sidekiq.cr - Simple, efficient job processing

Routing

orion - A minimal, rails-esque routing library
router.cr - Minimum but powerful http router for HTTP::Server

Scheduling

crystime - Advanced time, calendar, schedule, and remind library
schedule.cr - Run periodic tasks
tasker - A high precision scheduler including timezone aware cron jobs

Science and Data analysis

alea - Repeatable sampling, CDF and other utilities to work with probability distributions
ishi - Graph plotting package with a small API and sensible defaults powered by gnuplot
linalg - Linear algebra library inspired by MATLAB and SciPy.linalg
num.cr - Numerical computing library supporting N-Dimensional data
predict.cr - Satellite prediction library using the sgp4 model
quartz - Modeling and simulation framework

Search

hermes - Data Mapper pattern implementation for ElastiSearch

Serverless Computing

crystal_openfaas - Template to enable crystal as first class citizens in OpenFaaS
secrets-env - Extends ENV module to read values injected by docker / kubernetes secrets and other orchestration tools

System

baked_file_system - Virtual file system implementation
hardware - Get CPU, Memory and Network informations of the running OS and its processes

Task management

cake - Production-ready Make-like utility tool
sam - Another one Rake-like task manager with namespacing and arguments system

Template Engine

crinja - An implementation of the Jinja2 template engine
crustache - {{Mustache}} for Crystal
ECR (Embedded Crystal) - compile time template language which uses plain crystal expressions (Crystal stdlib)
Jbuilder - Generate JSON objects with a Builder-style DSL, inspired by jbuilder
Kilt - Abstraction layer for template engines
Slang - Lightweight, terse, templating language inspired by Ruby's Slim
teeplate - A library for rendering multiple template files

Testing

Athena Spec - Common/helpful Spec compliant testing utilities
crotest - A tiny and simple test framework
crytic - Mutation testing framework
hashr - A tiny class makes test on JSON response easier
LuckyFlow - Automated browser tests similar to Capybara
mass-spec - Web API testing library
microtest - Small opinionated testing library focusing on power asserts
minitest.cr - Library for unit tests and assertions
mocks.cr - Mocking library for Crystal
Spec - spec framework (Crystal stdlib)
spectator - Feature rich spec framework that uses the modern expect syntax
timecop.cr - Library for mocking with Time.now. Inspired by the timecop ruby gem
vcr - A HTTP capture and replay implementation for crystal
webdriver_pump - Page Object library. Inspired by Ruby's WatirPump
webmock.cr - Library for stubbing HTTP::Client requests

Third-party APIs

amazonite - An unofficial SDK supporting popular AWS APIs
aws-signer.cr - This library signs your HTTP requests using AWS v4
awscr-s3 - AWS S3 interface
awscr-signer - Sign HTTP::Request objects and generate presigned post forms
crystal-consul - Consul API client
crystal-darksky - Wrapper for the Dark Sky API
crystal-swapi - Star Wars API (SWAPI) wrapper
crystal_slack - A tool that parses Slack slash commands or send incoming web hooks
GDAX - GDAX REST and WebSocket API Wrapper with request signing
gitlab.cr - GitLab API wrapper
google - Google API wrapper
host_meta - A Web Host Metadata (https://tools.ietf.org/html/rfc6415) client
kube-client.cr - Kubernetes API Client
mixpanel-crystal - A library for sending events to Mixpanel
mollie.cr - Mollie Payments API wrapper (Creditcard, PayPal, Apple Pay, Sofort, Klarna, ...)
office365 - Microsoft Graph API wrapper
pinboard.cr - Pinboard API
raven.cr - Raven is a client for Sentry
stripe.cr - Stripe api wrapper
tmdb.cr - The Movie DB (TMDb) api wrapper
twitter-crystal - A library to access the Twitter API
web_finger - A WebFinger (https://tools.ietf.org/html/rfc7033) client
ynab.cr - A library to interact with your YNAB data

Validation

accord - Shareable validation library for Crystal Objects
Athena Validator - Robust & flexible validation framework
validations - Validations mixin
validator - Data check and validation

Web Frameworks

amber - Open source efficient and cohesive web application framework
Athena - A web framework comprised of reusable, independent components
grip - The microframework for writing powerful web applications
kemal - Lightning Fast, Super Simple web framework. Inspired by Sinatra
lucky - Catch bugs early, forget about most performance issues, and spend more time on code instead of debugging and writing tests
marten - A web framework that makes building web applications easy, productive, and fun
runcobo - An api framework with simple, intuitive and consistent DSL, using jbuilder to render json
Shivneri - Component based MVC web framework for crystal targeting good code structures, modularity & performance
spider-gazelle - A Rails esque web framework with a focus on speed and extensibility

Community

Unofficial

Chinese-speaking Telegram Group - 来吧！TG 中文圈的朋友们！
Crystal Programming Discord Server - Unofficial Discord server dedicated to the Crystal Programming Language
Portuguese-speaking Telegram Group - Bem vindos ao Crystal Brasil!
Russian-speaking Telegram Group - Добро пожаловать, товарищ!

Resources

Crystal for Rubyists - Free book to bootstrap your Crystal journey
Crystal Shards for Ruby Gems - A list of Ruby Gems and their Crystal Shards equivalents
crystal-koans - Learn Crystal by writing unit tests
crystal-lang.org - Official language site
devdocs.io - API Documentation Browser with Crystal support
Programming Crystal - PragProg book to start your Crystal journey

Official Documentation Translations

br.crystal-lang.org - Brazilian
ja.crystal-lang.org - Japanese
kr.crystal-lang.org - Korean
ru.crystal-lang.org - Russian
tw.crystal-lang.org - Chinese Traditional

Services and Apps

carc.in - A web service that runs your code and displays the result
Crank - A Procfile-based application manager (like Foreman)
cry - Ability to execute crystal code in a fashion similar to Ruby's pry edit
Crystal [ANN] - Announce new project, blog post, version update or any other Crystal work
DeBot - IRC bot written in Crystal
icr - Interactive console for Crystal (like IRB for Ruby)
Invidious - Invidious is an alternative front-end to YouTube
mpngin - A URL shortener with simple stats
procodile - Run processes in the background (and foreground) on Mac & Linux from a Procfile (for production and/or development environments)
quicktype - Generate models and serializers from JSON, JSON Schema, GraphQL, and TypeScript
shards.info - Web service that lists all repositories on GitHub that have Crystal code in them. The sources are available on GitHub

Tools

ast_helper - Helper tool to debug parser and formatter
crystal-base - CentOS base docker image for Crystal development
crystal-dash-docset - Dash docset generator
port_ruby_to_crystal - A regex replace ruby script for port ruby code to crystal easier, reduce friction
public_suffix - A small library designed to make the Public Suffix List (https://publicsuffix.org/) easier to use

DevOps

ansible-crystal - Ansible playbook for installing crystal
DPPM - An easy, universal way to install and manage applications as packages (mostly Linux)

Editor Plugins

Acme:
- acmecrystal - Reformats crystal code in acme
Atom
- crystal-tools - Enables built in tools in Crystal compiler
- language-crystal-actual - Crystal language support in Atom
Emacs
- crystal-mode - Crystal language support for Emacs (crystal-lang-tools/emacs-crystal-mode)
Geany
- geany-crystal - Crystal support for the Geany editor
IntelliJ IDEA
- intellij-crystal-lang - Crystal support for the JetBrains IDEs
Lite-XL
- lite-plugin-crystal - Crystal support for the Lite-XL editor
Spacemacs
- crystal-spacemacs-layer - Spacemacs contribution layer for Crystal
Sublime
- sublime-crystal - Crystal syntax highlighting for sublime Text
TextMate
- Crystal.tmbundle - Crystal syntax highlighting, compile, format command, snippets
Vim
- vim-crystal - Vim filetype support for Crystal
- vim-slang - Vim filetype support for Slang Templating Engine
Visual Studio Code
- vscode-crystal-lang - Formatter, linter and syntax highlighting for cr and ecr files

LSP Language Server Protocol Implementations

crystalline - Crystalline is an implementation of the Language Server Protocol written in and for the Crystal Language
scry - Code analysis server for Crystal implementing the Language Server Protocol

Shell plugins

crun - Crystal Run : shebang wrapper for Crystal
crystal-zsh - .oh-my-zsh plugin