From: Jp Hastings-spital <jphastings@...>
Date: 2009-03-19T09:13:43+09:00
Subject: Wrapping applications in Ruby

Variants on this theme have been posted time and again, but I can't find
a solution for this specific problem:

Say I have a program I need to use that performs a task for a given
amount of time then finishes, all the while providing a 'percent
complete' style output on STDOUT. eg:

./counting.rb
[RUBY]
#!/usr/bin/env ruby
n = 0

while n <= 10
  $stdout.puts "Completed: #{n*10}%"
  n = n + 1
end
[/RUBY]

Now, I'd like to build a ruby script that will call this script, wait
until completion and then continue with its tasks BUT all the while
updating a variable with the percentage complete. eg:

./script.rb
[RUBY]
def updatePercentage(pc)
  p "The percentage is now #{pc}"
end

Thread.new {
  # -- Problem area

  # Attempt 1
  `./counting.rb`
  # This will wait until after counting.rb is complete before
  # "All Done!" is printed, but I can't get to its stdout stream
  # before the program has finished running

  # Attempt 2
  Open3.popen3('./counting.rb') { |stdin, stdout, stderr|
    p stdout.readpartial(1)

    # With a view to doing something like:
    updatePercentage(stdout.readline.gsub(/^.*([0-9]+)%.*$/,"$1"))
  }
  # This doesn't work, counting.rb never begins executing
  # (tested by adding a line: open('output.txt','w') {|file| file.puts
"Percentage: #{n*10}%" }
  # to counting.rb and watching the file externally)

  p "All done!"
}

p "Irrelevant things"
sleep
[/RUBY]

Any ideas anyone? Essentially I'm looking for ways to wrap C programs
into ruby.

Cheers, JP
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