From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2004-05-14T03:33:56+09:00
Subject: Open4::popen4



blatant rip-off of Open3::popen3 - does anyone think something like this might
be useful (to have a handle on the spawned processes' pid?)

-a


# open4.rb: Spawn a program like popen, but with stderr, and pid, too. You
# might also want to use this if you want to bypass the shell. (By passing
# multiple args, which IO#popen does not allow)
#
# Usage:
#	require "open4"
#
#      stdin, stdout, stderr, pid = Open4.popen4('nroff -man')
#  or
#	include Open4
#      stdin, stdout, stderr, pid = popen4('nroff -man')

module Open4
  #[stdin, stdout, stderr, pid] = popen4(command);
  def popen4(*cmd)
    pw = IO::pipe   # pipe[0] for read, pipe[1] for write
    pr = IO::pipe
    pe = IO::pipe
    pc = IO::pipe

    pid = fork{
      # child
      gcid =
        fork{
          # grandchild
          pw[1].close
          STDIN.reopen(pw[0])
          pw[0].close

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

          pe[0].close
          STDERR.reopen(pe[1])
          pe[1].close

          pc[1].close

          exec(*cmd)
        }
      pc[0].close
      pc[1].puts gcid
      pc[1].close
      exit!
    }

    pc[1].close
    gcid = pc[0].read.to_i

    pw[0].close
    pr[1].close
    pe[1].close
    Process.waitpid(pid)
    pi = [pw[1], pr[0], pe[0]]
    pw[1].sync = true
    if defined? yield
      begin
	return yield(*pi)
      ensure
	pi.each{|p| p.close unless p.closed?}
      end
    end
    [pw[1], pr[0], pe[0], gcid]
  end
  module_function :popen4
end

if $0 == __FILE__
  a = Open4.popen4("nroff -man")
  Thread.start do
    while line = gets
      a[0].print line
    end
    a[0].close
  end
  while line = a[1].gets
    print ":", line
  end
end


-- 
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