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contents/articles/real-world-rawline-usage.html

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-----
title: Real-world Rawline usage
content-type: article
timestamp: 1236398040
tags: ruby|rawline
-----
<p>So I finally decided to update <a href="/rawline">RawLine</a> last week, and I added a more Readline-like <span class="caps">API</span>. When I first started the project, I was determined <em>not</em> to do that, because the current Readline wrapper shipped with Ruby is not very Ruby-ish: it&#8217;s a wrapper, after all!</p>
<p>The good thing of having a new <span class="caps">API</span> compatible with Readline is that now people can use RawLine in their Readline-powered scripts, with very minor modifications.</p>
<p>Let&#8217;s have a look at some examples (they are also shipped with <a href="http://rubyforge.org/projects/rawline">Rawline v0.3.1</a>):<br />
h3. Rush</p>
<p><a href="http://rush.heroku.com">Rush</a> is an excellent gem which provides a cross-platform shell environment, entirely written in Ruby.<br />
Being a shell, it obviously uses Readline for tab completion, and that does the job on Linux. On Windows though, things aren&#8217;t that easy:</p>
<ul>
	<li>text gets garbled if you write long lines</li>
	<li>you can&#8217;t type certain characters if they use some key modifiers like <RIGHT-ALT>, etc.</li>
</ul>
<p>RawLine doesn&#8217;t have these problems (that&#8217;s the very reason why I created it), so here&#8217;s a simple script which launches a Rawline-enabled Rush shell:</p>
<div class='ruby'><pre><code>require 'rubygems'
require 'rush'
require 'rawline'

class RawlineRush &lt; Rush::Shell

	def initialize
		Rawline.basic_word_break_characters = "" 
		Rawline.completion_proc = completion_proc
		super
	end

	def run
		loop do
			cmd = Rawline.readline('rawline_rush&gt; ')
			finish if cmd.nil? or cmd == 'exit'
			next if cmd == ""
			Rawline::HISTORY.push(cmd)
			execute(cmd)
		end
	end
end

shell = RawlineRush.new.run</code></pre></div><p>What happens here? Nothing much really, all I had to do was:</p>
<ol>
	<li>Derive a new class from Rush::Shell</li>
	<li>Set <code>Rawline.basic_word_break_characters</code> to the same value used in the original Rush code</li>
	<li>Set <code>Rawline.completion_proc</code> to <em>the same</em> completion Proc used in the original Rush code</li>
	<li>Rewrite the original <code>run</code> replacing <code>Readline</code> with <code>Rawline</code></li>
</ol>
<p>And it works as it was intended to, i.e. typing <code>root['b&lt;TAB&gt;</code> will expand to <code>root['bin/</code>, etc.<br />
Note that I didn&#8217;t write the completion Proc from scratch: it was already there.</p>
<h3><span class="caps">IRB</span></h3>
<p>After trying out Rush, the next logical step was trying <span class="caps">IRB</span> itself: I could never use it properly on Windows, and that was really frustrating.<br />
After a few minutes trying to figure out how to start <span class="caps">IRB</span> programmatically, I quickly came up with a similar example:</p>
<div class='ruby'><pre><code>require 'irb'
require 'irb/completion'
require 'rubygems'
require 'rawline'

Rawline.basic_word_break_characters= " \t\n\"\\'`&gt;&lt;;|&{(" 
Rawline.completion_append_character = nil
Rawline.completion_proc = IRB::InputCompletor::CompletionProc

class RawlineInputMethod &lt; IRB::ReadlineInputMethod
	include Rawline
	def gets
		if l = readline(@prompt, false)
			HISTORY.push(l) if !l.empty?
			@line[@line_no += 1] = l + "\n"
		else
			@eof = true
			l
		end
	end
end

module IRB
	@CONF[:SCRIPT] = RawlineInputMethod.new
end
IRB.start</code></pre></div><p>In this case, Rawline is included in the <code>RawlineInputMethod</code> class, derived from the original <code>ReadlineInputMethod</code> class, i.e. the class <span class="caps">IRB</span> uses to define (guess&#8230;) how to input characters.<br />
Again, all I had to do was set a few Rawline variables to match the ones used in Readline, and then redefine the function used to get characters. All done.</p>
<p>It works as expected (only with inline completion, of course): typing <code>"test".ma&lt;TAB&gt;</code> will give you <code>"test".map</code>, <code>"test".match</code>, etc.</p>
<p>You also get all Rawline key mappings for free (<span class="caps">CTRL</span>-K to clear the line, <span class="caps">CTRL</span>-U and <span class="caps">CTRL</span>-R to undo and redo, etc.), and you can define your own.</p>