无法使用popen3正确处理STDOUT和STDERR输出？

Question

我正在编写一个函数来执行shell命令，并返回它的退出代码STDOUT和STDERR。

问题是，此函数无法正确捕获STDOUT和STDERR输出。

def sh(*args)
  options = args[-1].respond_to?(:to_hash) ? args.pop.to_hash: {}
  options = { :timeout => 0, :sudo => false }.merge(options)
  cmd = options[:sudo] == false ? args[0] : "sudo " << args[0]

  begin
    stdin, stdout, stderr, wait_thr = Open3.popen3(cmd)
    pid = wait_thr[:pid]
    out_buf = ""
    err_buf = ""
    start = Time.now

    # Manually ping the process per 0.2 second to check whether the process is alive or not
    begin
      out_buf << stdout.read_nonblock(4096)
      err_buf << stderr.read_nonblock(4096)
      # kill the process if it timeouts
      if options[:timeout] != 0 && (Time.now - start) > options[:timeout]
        Process.kill("KILL", pid)
        Process.detach(pid)
        raise RuntimeError, "process with pid #{pid} timed out with #{options[:timeout]} seconds."
      end
      sleep 0.2
    rescue IO::WaitReadable, EOFError
    end while wait_thr.alive?

  rescue => e
    NtfLogger.warn("sh '#{args}' executed with failure: #{e}")

  ensure
    if wait_thr.nil?
      return 1, out_buf, err_buf
    else
      return wait_thr.value.exitstatus, out_buf, err_buf
    end
  end
end # end of sh

有人能帮我找出问题出在哪里吗？

Answer 1

我对popen3文档的理解是，最好在块中进行处理：

Open3.popen3([env,] cmd... [, opts]) do |stdin, stdout, stderr, wait_thr|
  pid = wait_thr.pid # pid of the started process.
  ...
  exit_status = wait_thr.value # Process::Status object returned.
end

在非块形式中，文档注意到流必须关闭：

stdin, stdout, stderr, wait_thr = Open3.popen3([env,] cmd... [, opts])
pid = wait_thr[:pid]  # pid of the started process.
...
stdin.close  # stdin, stdout and stderr should be closed explicitly in this form.
stdout.close
stderr.close
exit_status = wait_thr.value  # Process::Status object returned.

http://www.ruby-doc.org/stdlib-2.0.0/libdoc/open3/rdoc/Open3.html#method-c-popen3

最后，顺便说一句，这里有一个围绕capture3的包装器，我在我的一端使用它。如果sh实用程序中与线程相关的部分并不重要，您可以很容易地将其扩展为添加一个sudo选项：

#
# Identical to Open3.capture3, except that it rescues runtime errors
#
# @param env optional (as `Kernel.system')
# @param *cmd the command and its (auto-escaped) arguments
# @param opts optional a hash of options (as `Kernel.system')
#
# @return [stdout, stderr, success] | [$/, $/, nil] on error
#
def system3(*cmd)
  begin
    stdout, stderr, status = Open3.capture3(*cmd)
    [stdout, stderr, status.success?]
  rescue
    [$/, $/, nil]
  end
end