From: ara.t.howard@...
Date: 2006-09-20T14:02:21+09:00
Subject: Re: piping input when shelling out

On Wed, 20 Sep 2006, Caio Chassot wrote:

>
> On 2006-09-19, at 23:17 , ara.t.howard@noaa.gov wrote:
>
>> you're making it pretty hard on yourself:
>
> I guess I was :)
>
>> my session and open4 lib both abstract this largely, including a good deal 
>> of
>> error handling.  there is also the built-in open3 module.  check out the 
>> docs.
>
> Thanks.
>
> Having a separate stdout and stderr is great, in fact, just the next thing I 
> was going to ask about. So both open3 and open4 seem like great candidates.
>
> Could you take some time to sell open4 over open3?
>
> The main advantage I see is the greater abstraction, i.e. the spawn method.

- you get the child pid returned also with open4

- a command that fails to exec raises and error (note this is sent back from
   the child fork)

- when using the spawn method a great deal of abstraction is provided, not
   least of which that stdin, stdout, stderr are each handled via a thread so
   you may provide objects that can handle async output

     Open4.spawn cmd, 1=>stdout_handler 2=>stderr_handler

   and it will be passed to the hanlder in an async way


the main reason, however, is having the pid - it's hard to kill a proces
without it!  ;-)

that said - if all you require is stdout/stderr stay with the stdlib.

regards.


-a
-- 
in order to be effective truth must penetrate like an arrow - and that is
likely to hurt. -- wei wu wei