Open stdin, stdout, and stderr streams and start external executable. Non-block form:

require 'open3'

[stdin, stdout, stderr] = Open3.popen3(cmd)

Block form:

require 'open3'

Open3.popen3(cmd) { |stdin, stdout, stderr| ... }

The parameter cmd is passed directly to Kernel#exec.

Source Code

# File open3.rb, line 46
def popen3(*cmd)
  pw = IO::pipe   # pipe[0] for read, pipe[1] for write
  pr = IO::pipe
  pe = IO::pipe

  pid = fork{
    # child
    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

      exec(*cmd)
    }
    exit!(0)
  }

  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
  pi
end