From: jqwoods@...
Date: 2008-03-15T05:54:56+09:00
Subject: Re: How to separate stdout & stderr from executed shell comm

On Mar 14, 12:58 pm, James Gray <ja...@grayproductions.net> wrote:
> On Mar 14, 2008, at 2:49 PM, jqwo...@gmail.com wrote:
>
>
>
> > On Mar 14, 12:16 pm, Rodrigo Bermejo <rodrigo.berm...@ps.ge.com>
> > wrote:
> >> unknown wrote:
> >>> On Mar 14, 11:40 am, jqwo...@gmail.com wrote:
>
> >>>>  irb> my_exec_command("ls NON_existant_file")
> >>>>  => ["", "ls: NON_existant_file: No such file or directory\n", 2]
>
> >>>> Any pointers on how to implement my_exec_command?
>
> >>> PS: Unless there's a simpler way, if someone could just point me
> >>> to an
> >>> API that provides stdout and stderr of sub-processes as IO
> >>> objects, I
> >>> could probably figure it out from there. Thanks!
>
> >> Take a look at the IO class.
> >> The Pickaxe book has some good examples.
>
> >> -r.
> >> --
> >> Posted viahttp://www.ruby-forum.com/.
>
> > The closest API I could find is IO::popen. But as the doc for
> > IO::popen says "...the subprocess's standard input and output will be
> > connected..." So far I haven't found any way to get stdout and stderr
> > of a sub-process *separately*.
>
> > Any other pointers?
>
> Yes, Ruby comes with a standard library for this, called open3.  Here
> are the docs for the method you want:
>
> $ qri Open3#popen3
> ----------------------------------------------------------- Open3#popen3
>       popen3(*cmd) {|| ...}
> ------------------------------------------------------------------------
>       Open stdin, stdout, and stderr streams and start external
>       executable. Non-block form:
>
>         require 'open3'
>
>         [stdin, stdout, stderr] = Open3.popen3(cmd)
>
>       Block form:
>
>         require 'open3'
>
>         Open3.popen3(cmd) { |stdin, stdout, stderr| ... }
>
>       The parameter cmd is passed directly to Kernel#exec.
>
> Hope that helps.
>
> James Edward Gray II

Exactly what I was looking for. Thanks!