From: Brian Candler <B.Candler@...>
Date: 2003-05-28T01:48:12+09:00
Subject: Re: system calls

On Tue, May 27, 2003 at 10:24:50PM +0900, mgarriss wrote:
> so I can get the standard output from a system call:
> 
>   s = `date`
> 
> and I can get the return value:
> 
>   system( "date" )
> 
> and I have no idea how to get the standard error:
> 
>   ???
> 
> but what I really want is all three, like:
> 
>   out, err, ret = really_cool_system( "date" )

This is almost what you want, except that the exit code is wrong and I don't
know how to fix it:

require 'open3'
module Kernel
  private
  def really_cool_system(*args)
    inp, out, err = Open3.popen3(*args)
    ret1 = ret2 = nil
    t1 = Thread.new do
      inp.close
    end
    t2 = Thread.new do
      ret1 = out.read
      out.close
    end
    t3 = Thread.new do
      ret2 = err.read
      err.close
    end
    t1.join
    t2.join
    t3.join
    return ret1, ret2, $?
  end
end

irb(main):024:0> really_cool_system("ls","/dev/null","/dev/foo")
=> ["/dev/null\n", "ls: /dev/foo: No such file or directory\n", 65280]

Regards,

Brian.