Ruby Open3.pipeline_start用法及代码示例

pipeline_start(*cmds, &block)

Open3.pipeline_start 将命令列表作为管道启动。没有为第一个命令的标准输入和最后一个命令的标准输出创建管道。

Open3.pipeline_start(cmd1, cmd2, ... [, opts]) {|wait_threads|
  ...
}

wait_threads = Open3.pipeline_start(cmd1, cmd2, ... [, opts])
...

每个 cmd 都是一个字符串或一个数组。如果它是一个数组，则将元素传递给 Process.spawn 。

cmd:
  commandline                              command line string which is passed to a shell
  [env, commandline, opts]                 command line string which is passed to a shell
  [env, cmdname, arg1, ..., opts]          command name and one or more arguments (no shell)
  [env, [cmdname, argv0], arg1, ..., opts] command name and arguments including argv[0] (no shell)

Note that env and opts are optional, as for Process.spawn.

例子：

# Run xeyes in 10 seconds.
Open3.pipeline_start("xeyes") {|ts|
  sleep 10
  t = ts[0]
  Process.kill("TERM", t.pid)
  p t.value #=> #<Process::Status: pid 911 SIGTERM (signal 15)>
}

# Convert pdf to ps and send it to a printer.
# Collect error message of pdftops and lpr.
pdf_file = "paper.pdf"
printer = "printer-name"
err_r, err_w = IO.pipe
Open3.pipeline_start(["pdftops", pdf_file, "-"],
                     ["lpr", "-P#{printer}"],
                     :err=>err_w) {|ts|
  err_w.close
  p err_r.read # error messages of pdftops and lpr.
}