Open3.popen3("echo foo")
Open3.popen2("echo foo")
Open3.popen2e("echo foo")
Open3.capture3("echo foo")
Open3.capture2("echo foo")
Open3.capture2e("echo foo")
Open3.pipeline_rw("echo foo", "grep bar")
Open3.pipeline_r("echo foo", "grep bar")
Open3.pipeline_w("echo foo", "grep bar")
Open3.pipeline_start("echo foo", "grep bar")
Open3.pipeline("echo foo", "grep bar")

Open4::open4("echo foo")
Open4::popen4("echo foo")
Open4.spawn("echo bar")
Open4.popen4ext("echo foo")
Open4.popen4ext("echo", "foo")
Open4.popen4ext(true, "echo foo")
Open4.popen4ext(true, "echo", "foo")