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1#!/usr/bin/env ruby
2#
3# Name: reval.rb
4# License: MIT
5# Author: postmodern (postmodern.mod3 at gmail.com)
6# Description:
7#
8# Re-evaluates a specified Ruby file whenever the file changes.
9# Reval was inspired by Giles Bowkett's kickass talk on Archaeopteryx at
10# RubyFringe 2008, where Giles used some mad Ruby to re-evaluate his
11# Achaeopteryx script as he edited it.
12#
13# Reval might come in handy, when you give that awesome breakthrough talk
14# at some conference.
15#
16
17require 'digest/md5'
18
19#
20# Re-evaluate the contents of the specified _file_, whenever the file
21# changes, using the given _options_.
22#
23# _options_ may contain the following keys:
24# <tt>:pause</tt>:: Number of seconds to sleep between checking the _file_
25#                   for changes. Defaults to +0.4+ if not given.
26#
27#   reval 'file.rb'
28#
29#   reval 'file.rb', :pause => 0.4
30#
31def reval(file,options={})
32  pause = (options[:pause] || 0.4)
33
34  last_time = Time.now
35  this_time = Time.now
36
37  last_fingerprint = nil
38  fingerprint = nil
39
40  if File.file?(file)
41    last_fingerprint = Digest::MD5.hexdigest(File.read(file))
42
43    load(file)
44  end
45
46  loop do
47    begin
48      this_time = File.mtime(file)
49
50      if (this_time > last_time)
51        fingerprint = Digest::MD5.hexdigest(File.read(file))
52
53        if last_fingerprint != fingerprint
54          load(file)
55
56          last_fingerprint = fingerprint
57        end
58
59        last_time = this_time
60      end
61    rescue Errno::ENOENT
62    end
63
64    sleep(pause)
65  end
66end
67
68reval(ARGV[0]) if ($0 =~ /reval/ && ARGV[0])