From: nobu.nokada@...
Date: 2003-01-24T10:31:23+09:00
Subject: Re: exit status, stderr and stdout

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Hi,

At Fri, 24 Jan 2003 08:33:11 +0900,
Daniel Bretoi wrote:
> In perl, I was able to do this,
> 
>    my $pid = open3($wtr, $rdr, $err, "ls ---");
> waitpid($pid,WNOHANG);
> warn $? >> 8;
> 
> however, looking at the code for open3.rb it doesn't seem possible to
> capture the pid (infact, it seems to be completely discarded).

Sorry, I've forgotten that I'm using modified version of
open3.rb, due to get rid of that very problem.


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# Usage:
#	require "open3"
#
#	in, out, err = Open3.popen3('nroff -man')
#  or
#	include Open3
#	in, out, err = popen3('nroff -man')
#

module Open3
  class Process < Module
    def initialize(cmd, error = true)
      super(&nil)
      writer = IO::pipe   # pipe[0] for read, pipe[1] for write
      reader = IO::pipe
      error = IO::pipe if error

      pid = fork do
	# child
	writer[1].close
	STDIN.reopen(writer[0])
	writer[0].close

	reader[0].close
	STDOUT.reopen(reader[1])
	reader[1].close

	if error
	  error[0].close
	  STDERR.reopen(error[1])
	  error[1].close
	end

	exec(*cmd)
	exit!
      end

      writer[0].close
      reader[1].close
      error[1].close if error
      cmd = self
      writer, reader, error = writer[1], reader[0], error[0]
      define_method(:pid) {|| pid}
      define_method(:command) {|| cmd}
      define_method(:writer) {|| writer}
      define_method(:reader) {|| reader}
      define_method(:error) {|| error}
      extend(self)
      pi = [reader, writer]
      pi << error if error
      pi.each {|p| p.extend(self)}
      if defined? yield
	begin
	  return yield(*pi)
	ensure
	  pi.each {|p| p.close unless p.closed?}
	  begin Process.waitpid(pid); rescue Errno::ECHILD; end
	end
      end
      ObjectSpace.define_finalizer(self, self.class.finalizer(pid))
    end

    def wait
      status = Process.waitpid(@pid)
      ObjectSpace.undefine_finalizer(self)
      status
    rescue Errno::ECHILD
      nil
    end

    def self.finalizer(pid)
      proc {begin Process.waitpid(pid); rescue Errno::ECHILD; end}
    end
  end

  #[stdin, stdout, stderr] = popen3(command);
  def popen3(*cmd)
    p = Process.new(cmd)
    [p.writer, p.reader, p.error]
  end
  module_function :popen3
end

if $0 == __FILE__
  def test
    a = Open3.popen3("nroff -man")
    Thread.start do
      while line = gets
	a[0].print line
      end
      a[0].close
    end
    pid = a[1].pid
    system("ps", $$.to_s, pid.to_s)
    while line = a[1].gets
      print ":", line
    end
    a.clear
    a = nil
    pid
  end
  pid = test
  system("ps", $$.to_s, pid.to_s)
  GC.start
  system("ps", $$.to_s, pid.to_s)
end

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-- 
Nobu Nakada

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