From: "list. rb" <list.rb@...>
Date: 2009-06-20T06:26:07+09:00
Subject: Re: Capturing System Call Return Values?

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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 th=
e
> system library (e.g. open(), read(), fork()).  What you mean would rather=
 be
> called an "external process".  (Of course that's done via a system call a=
s
> 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 t=
he
>>>> return values of system calls.
>>>>
>>> appears to be $?, from some google work
>>>
>>> http://74.125.155.132/search?q=3Dcache:lNLxDxyXbj4J:www.rubyist.net/~sl=
agell/ruby/globalvars.html+ruby+global+variables&cd=3D1&hl=3Den&ct=3Dclnk&g=
l=3Dus&client=3Dfirefox-a<http://74.125.155.132/search?q=3Dcache:lNLxDxyXbj=
4J:www.rubyist.net/%7Eslagell/ruby/globalvars.html+ruby+global+variables&cd=
=3D1&hl=3Den&ct=3Dclnk&gl=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 of =
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/
>
>

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