opts.cr

a wrapper for OptionParser to provide default values and handy args

crystal versions

• v0.4.4 for crystal-0.24 or lower
• v0.5.0 for crystal-0.25, 0.26 or higher

Installation

Add this to your application's shard.yml:

dependencies:
  opts:
    github: maiha/opts.cr
    version: 0.6.0

Opts module

class methods

• option : declare a variable which is a proxy to OptionParser

class consts

override PROGRAM VERSION ARGS USAGE as you like.

• see src/opts.cr

instance methods

• args : command line args
• parser : a runtime instance of OptionParser
• xxx : a getter method defined by option xxx
• version : reserved for special option which delegates to show_version
• help : reserved for special option which delegates to show_usage

Flow

1. App(or Opts).run(ARGV) # appliation entrypoint
2. app = App.new # instance creation
3. app.run(ARGV) # instance etnrypoint
4. • app.setup(ARGV) # parse ARGV by parse and args is now available
5. • app.run # (required) write main routine here
6. • app.on_error(err) # only when an error occurred in run(ARGV)

Usage

require "opts"

class App
  include Opts

  VERSION = "0.1.0"
  PROGRAM = "foo"

  option host    : String, "-h host"  , "Server hostname", "127.0.0.1"
  option port    : Int32 , "-p port"  , "Server port number", 80
  option help    : Bool  , "--help"   , "Show this help", false
  option version : Bool  , "--version", "Print the version and exit", false

  def run
    p [host, port, args]
  end
end

App.run

% ./foo
["127.0.0.1", 80, []]

% ./foo a
["127.0.0.1", 80, ["a"]]

% ./foo a b
["127.0.0.1", 80, ["a", "b"]]

% ./foo -h localhost a b
["localhost", 80, ["a", "b"]]

% ./foo --version
foo 0.1.0

% ./foo -x
foo version 0.1.0

Usage: foo

Options:
  -h host                          Server hostname (default: 127.0.0.1).
  -p port                          Server port number (default: 80).
  --help                           Show this help.
  --version                        Print the version and exit.

Invalid option: -x

with block

• v : special variable used for block parameter

class App1
  include Opts

  option list : Array(String)       , "-s VALUE", "store into list" do list << v; end
  option hash : Hash(String, String), "-d VALUE", "store into hash" do
    key, val = v.split("=", 2)
    hash[key] = val
  end
end

App1.run(["-s", "a"]).list   # => ["a"]
App1.run(["-d", "x=1"]).hash # => {"x" => "1"}

Nilable

class App2
  include Opts

  option token : String?, "-a TOKEN", "Your access token", nil
end

App2.run.token                # => nil
App2.run(["-a", "xxx"]).token # => "xxx"

Further usages

Real products

• https://github.com/maiha/redis-cluster-benchmark.cr/blob/master/src/bin/main.cr
• https://github.com/maiha/dstat-redis.cr/blob/master/src/bin/main.cr
• https://github.com/maiha/rcm.cr/blob/master/src/bin/rcm.cr
• https://github.com/maiha/grafana-redis.cr/blob/master/src/bin/main.cr

Contributing

1. Fork it ( https://github.com/maiha/opts.cr/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

• maiha maiha - creator, maintainer