From: ara.t.howard@...
Date: 2007-04-20T00:04:37+09:00
Subject: Re: Executing program from ruby

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
-- 
be kind whenever possible... it is always possible.
- the dalai lama