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CLI.K stands for Command Line Interface in the Kernel. It provides a very simple cli method for parsing command line options.


They call it "K.I.S.S."

Usage is very straightforward, although it might look a little odd at first glance:

  require 'clik'

  cli '-f --file'  => lambda{ |f| @file = f },
      '-d --debug' => lambda{ $DEBUG = true },
      '-h --help'  => lambda{ show_help }

There's very little to it really. The cli command simply maps command line options to procedures which are used to process them. That's it.

In our example, notice that -w and --whatever are easily defined as synonymous options. Simple. Then notice that the -f/--file option's procedure takes an argument, so the command line option takes an argument as well. Again simple.

The cli method has a few additional niceties. It can handle run-on flags, i.e. -abc is the same as -a -b -c. And you can pass it an alternate set of arguments to parse, as the first argument, to use something other than the default ARGV.

  argv = ['--testing']

  cli argv,

You need help, no you really don't

At this point, you might be wonder about help output. Clearly there are no descriptions given in our example. Well, guess what! It's really easy to print something out yourself. In fact, if you really want to do it right, create a manpage with ronn or md2man, and impress your friends. It's a much better approach then jamming all that verbiage into you command line options parser code.

Ask and you shell receive

In addition to cli CLI.K include the ask method. This is a very simple command line query method.

ans = ask "Are you nice? [Y/N]"

Other Ruby libraries have their own take on the #ask method, and this very simple implementation can just as soon be overridden. No biggy. But it's nice to have for simple use cases.


We have to give credit where credit is due. This interface is the great achievement of Michel Martens, who created the original Clap library from which CLI.K evolved. Mr. Martens deserves high praise for this design. It's not easy to realize that this level of simplicity is all one really needs! Thank you, Michel!

Copyrights & License

CLI.K is copyrighted open-source software.

Copyright (c) 2013 Rubyworks

CLI.K is base on Michel Marten's Clap library.

Copyright (c) 2010 Michel Martens

See LICENSE.txt and NOTICE.txt files for details.