From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2005-07-05T07:03:40+09:00
Subject: Re: Exececuting another application from within ruby

On Tue, 5 Jul 2005, Nigel Wilkinson wrote:

> Hi folks
>
> I have a smell application from which I wish to display a file using an 
> external helper programme.
>
> Lets say
> app = the external programme
> file = the file to be displayed
>
> I've tried
>
> system(app, file)
>
> This works but it blocks my application. How can I fire up the helper 
> application in the background?

   def background command
     Thread::new(command, Thread::current) do |cmd, cur|
       begin
         pipe = IO::popen cmd
         true while pipe.gets and pipe.close
         $?.exitstatus
       rescue Exception => e
         cur.raise e
       end
     end
   end

   thread = background 'long-running'

   ...
   ...
   ...

   p thread.value # exitstatus

hth.  if you need control over stdout and stderr check out session.  it
provides thread safe execution.

   require 'session'

   def background command
     sh = Session::new
     Thread::new(command, Thread::current) do |cmd, cur|
       begin
         stdout, stderr = sh.execute cmd
         [stdout, stderr, sh.status]
       rescue Exception => e
         cur.raise e
       end
     end
   end

   thread = background 'long-running'

   ...
   ...
   ...

   p thread.value # [stdout, stderr, exitstatus]

session also allows thread safe stuff like

   def background command, widget
     sh = Session::new
     Thread::new(command, Thread::current) do |cmd, cur|
       begin
         sh.execute(cmd) do |stdout, stderr|
           widget.update stdout, stderr
         end
         sh.status
       rescue Exception => e
         cur.raise e
       end
     end
   end


hth.

-a
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