From: Marcin Raczkowski <swistak@...>
Date: 2007-04-20T22:46:25+09:00
Subject: Re: Executing program from ruby

On Thursday 19 April 2007 15:04, ara.t.howard@noaa.gov wrote:
> On Thu, 19 Apr 2007, Marcin Raczkowski wrote:
> > Hello i know there are several ways to execute from within ruby
> > but each one have their own problems:
> >
> > `` doesn't check if command /programm runs at all!, also it blocks untill
> > command returns, no bi-directional comunication
> > popen2,3,4 doesn't check if command exists at all ... it's not rising any
> > errors ... and happilly continues to run untill you try to write
> > something to pipe that leads to program that never even started
> >
> > only system() checks if command runs but it also returns false when
> > programs starts but returns anything other then 0
> >
> > does anyone know good way to check if command exists then run it, return
> > pid for monitoring purposes and allow bidirectional comunication, then
> > check exit status ?
> >
> > open4 comes close to fulfilling all that but it doesn't rise (sample
> > program that tells you it'll doesn't eaither),
>
> ??
>
>
>    harp:~ > ruby -r open4 -e'  Open4.popen4 "no-exist"  '
>    /home/ahoward//lib/ruby/site_ruby/1.8/open4.rb:37:in `exec': No such
> file or directory - no-exist (Errno::ENOENT) from
> /home/ahoward//lib/ruby/site_ruby/1.8/open4.rb:37:in `popen4' from
> /home/ahoward//lib/ruby/site_ruby/1.8/open4.rb:21:in `popen4' from -e:1
>
>
>    harp:~ > ruby -r open4 -e'  Open4.spawn "no-exist"  '
>    /home/ahoward//lib/ruby/site_ruby/1.8/open4.rb:37:in `exec': No such
> file or directory - no-exist (Errno::ENOENT) from
> /home/ahoward//lib/ruby/site_ruby/1.8/open4.rb:37:in `popen4' from
> /home/ahoward//lib/ruby/site_ruby/1.8/open4.rb:21:in `popen4' from
> /home/ahoward//lib/ruby/site_ruby/1.8/open4.rb:273:in `spawn' from
> /home/ahoward//lib/ruby/1.8/timeout.rb:38:in `timeout' from
> /home/ahoward//lib/ruby/site_ruby/1.8/open4.rb:272:in `spawn' from -e:1
>
> from the dist
>
>
>    harp:open4-0.9.3 > pwd
>    /home/ahoward/eg/ruby/open4/open4-0.9.3
>
>
>    harp:open4-0.9.3 > cat sample/exception.rb
>    require "open4"
>    Open4::popen4 "noexist"
>
>
>    harp:open4-0.9.3 > ruby sample/exception.rb
>    /home/ahoward/nfs//lib/ruby/site_ruby/1.8/open4.rb:37:in `exec': No such
> file or directory - noexist (Errno::ENOENT) from
> /home/ahoward/nfs//lib/ruby/site_ruby/1.8/open4.rb:37:in `popen4' from
> /home/ahoward/nfs//lib/ruby/site_ruby/1.8/open4.rb:21:in `fork' from
> /home/ahoward/nfs//lib/ruby/site_ruby/1.8/open4.rb:21:in `popen4' from
> sample/exception.rb:3
>
>
>
> can you show an exampe which does not work?
>
> > not to mention compleate lack of > documentation.
>
> ??
>
>    http://codeforpeople.com/lib/ruby/open4/open4-0.9.3/README
>
> this covers nearly every part of open4.  if you need more, there is
>
>    http://codeforpeople.com/lib/ruby/open4/open4-0.9.3/lib/open4.rb
>
> it is an extremely small library
>
> > any expirience with open4? help? pointers?
> > mayby i'm simply missing some obvious way?
>
> i wrote open4 - so i'm expirienced with it ;-)  can you give and example of
> exactly what you're trying to do?
>
> regards.
>
> -a

i sent you example on e-mail, but it was my fault... in you examples there's 
no require 'rubygems', and it's required to work, if not it loads standard 
open4 library :/ took me 2h to figure that out.

preaty good library tho (at least when i got it to work)
-- 
Marcin Raczkowski
---
Friends teach what you should know
Enemies Teach what you have to know