From: "list. rb" <list.rb@...>
Date: 2009-06-20T06:28:30+09:00
Subject: Re: Capturing System Call Return Values?

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On Fri, Jun 19, 2009 at 5:26 PM, list. rb <list.rb@gmail.com> wrote:

> class Task
>  attr_accessor :cmd, :pid, :output, :exitstatus, :thread
>  def initialize(cmd)
>    @cmd =3D cmd
>    queue =3D Queue.new
>    @thread =3D Thread.new(queue) {|q|
>      pipe =3D IO.popen(cmd + " 2>&1")
>      q.push(pipe)
>      q.push(pipe.pid)
>      self.pid =3D pipe.pid
>      begin
>        self.output =3D pipe.readlines
>        pipe.close
>        self.exitstatus =3D $?.exitstatus
>      rescue =3D> e
>        q.push e
>      end
>    }
>    queue.clear
>  end
>  def join
>    thread.join
>  end
> end
>
> task =3D Task.new("ruby -e 'sleep 3 and puts Time.now'")
> task.join
> p task
>
> On Fri, Jun 19, 2009 at 4:05 PM, Robert Klemme
> <shortcutter@googlemail.com>wrote:
>
> > On 19.06.2009 20:52, Tyler Knappe wrote:
> >
> >> Roger Pack wrote:
> >>
> >>> Tyler Knappe wrote:
> >>>
> >>>> I'm attempting to use Ruby to make system calls (in this case python
> >>>> scripts) which return values,
> >>>>
> >>>
> > The term "system call" is usually used to denote calls of functions in
> the
> > system library (e.g. open(), read(), fork()).  What you mean would rath=
er
> be
> > called an "external process".  (Of course that's done via a system call
> as
> > well, but this is just one of a multitude of available system calls.)
> >
> >  that I then hand off to Ruby on Rails to
> >>>> populate a webpage.  However, I've run into a problem with capturing
> the
> >>>> return values of system calls.
> >>>>
> >>> appears to be $?, from some google work
> >>>
> >>>
> http://74.125.155.132/search?q=3Dcache:lNLxDxyXbj4J:www.rubyist.net/~slag=
ell/ruby/globalvars.html+ruby+global+variables&cd=3D1&hl=3Den&ct=3Dclnk&gl=
=3Dus&client=3Dfirefox-a<http://74.125.155.132/search?q=3Dcache:lNLxDxyXbj4=
J:www.rubyist.net/%7Eslagell/ruby/globalvars.html+ruby+global+variables&cd=
=3D1&hl=3Den&ct=3Dclnk&gl=3Dus&client=3Dfirefox-a>
> <
> http://74.125.155.132/search?q=3Dcache:lNLxDxyXbj4J:www.rubyist.net/%7Esl=
agell/ruby/globalvars.html+ruby+global+variables&cd=3D1&hl=3Den&ct=3Dclnk&g=
l=3Dus&client=3Dfirefox-a
> >
> >>>
> >>
> >> $?    exit status of last executed child process
> >>
> >> I don't think is quite correct.  I tried it and was returned a value o=
f
> 0.
> >>
> >
> > Why would that mean that the statement above is not correct?
> >
> >  I've found a work around by splitting the returned string using
> >> [string].split(' ') but this isn't as elegant as I had hoped.
> >>
> >
> > Now I am not sure what you want: are you interested in the exit status =
of
> a
> > process that was executed?  E.g.
> >
> > irb(main):010:0> system "false"
> > =3D> false
> > irb(main):011:0> $?
> > =3D> #<Process::Status: pid 4008 exit 1>
> > irb(main):012:0> system "echo", "test"
> > test
> > =3D> true
> > irb(main):013:0> $?
> > =3D> #<Process::Status: pid 1228 exit 0>
> > irb(main):014:0>
> >
> > Or do you mean the output of an external process, e.g.
> >
> > irb(main):001:0> dir =3D `ls -dl`
> > =3D> "drwxrwxrwt+ 2 robert Benutzer 0 Jun 19 21:53 .\n"
> > irb(main):002:0>
> >
> > Your last statement seems to indicate the latter.
> >
> > Kind regards
> >
> >        robert
> >
> > --
> > remember.guy do |as, often| as.you_can - without end
> > http://blog.rubybestpractices.com/
> >
> >
>



Whoops, I top posted


class Task
  attr_accessor :cmd, :pid, :output, :exitstatus, :thread
  def initialize(cmd)
    @cmd =3D cmd
    queue =3D Queue.new
    @thread =3D Thread.new(queue) {|q|
      pipe =3D IO.popen(cmd + " 2>&1")
      q.push(pipe)
      q.push(pipe.pid)
      self.pid =3D pipe.pid
      begin
        self.output =3D pipe.readlines
        pipe.close
        self.exitstatus =3D $?.exitstatus
      rescue =3D> e
        q.push e
      end
    }
    queue.clear
  end
  def join
    thread.join
  end
end

task =3D Task.new("ruby -e 'sleep 3 and puts Time.now'")
task.join
p task

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