From: Gennady <gfb@...>
Date: 2003-11-25T10:01:09+09:00
Subject: Re: Exit status on cmd executed via popen()



Garance A Drosihn wrote:
> At 7:27 AM +0900 11/25/03, Gennady wrote:
> 
>> Try variable $?, it holds the status of the last executed
>> command. Works for commands executed with 'system', I think
>> it is valid for popen as well.
> 
> 
> Interesting.  In the code sequence of:
> 
> cmdout = IO.popen(somecmd, "r")
> cmdout.each_line {|aline|
>     #  Do Stuff...
> }
> cmdout.close
> 
> I had tried checking $? just before cmdout.close, and it had a
> value of nil.  However, checking it immediately *after* the
> close, it does seem to have $? set to the desired value.  As
> long as I can depend on this, it will do the job very nicely.
> Thanks!
> 

I have implemented a method available through Kernel.launch. It allows 
you to execute several commands connecting all of them in a pipeline. I 
makes available each command's  return status together with stderr 
messages. The last command's stdout is also available. I haven't 
released it, however if you are interested you can get it at

http://homepage.mac.com/bystr/Development/Ruby/launch.rb

It has a set of unit tests attached, so it should be easy to figure out 
the usage. I am not sure if it works on Windows as it uses fork() and 
Process.waitpid2()

I mentioned it on ruby-talk before, you may find some description there:
http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/72318

Gennady.